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perfmon.c

/*
 * This file implements the perfmon-2 subsystem which is used
 * to program the IA-64 Performance Monitoring Unit (PMU).
 *
 * The initial version of perfmon.c was written by
 * Ganesh Venkitachalam, IBM Corp.
 *
 * Then it was modified for perfmon-1.x by Stephane Eranian and
 * David Mosberger, Hewlett Packard Co.
 *
 * Version Perfmon-2.x is a rewrite of perfmon-1.x
 * by Stephane Eranian, Hewlett Packard Co.
 *
 * Copyright (C) 1999-2005  Hewlett Packard Co
 *               Stephane Eranian <eranian@hpl.hp.com>
 *               David Mosberger-Tang <davidm@hpl.hp.com>
 *
 * More information about perfmon available at:
 *    http://www.hpl.hp.com/research/linux/perfmon
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/sysctl.h>
#include <linux/list.h>
#include <linux/file.h>
#include <linux/poll.h>
#include <linux/vfs.h>
#include <linux/smp.h>
#include <linux/pagemap.h>
#include <linux/mount.h>
#include <linux/bitops.h>
#include <linux/capability.h>
#include <linux/rcupdate.h>
#include <linux/completion.h>

#include <asm/errno.h>
#include <asm/intrinsics.h>
#include <asm/page.h>
#include <asm/perfmon.h>
#include <asm/processor.h>
#include <asm/signal.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/delay.h>

#ifdef CONFIG_PERFMON
/*
 * perfmon context state
 */
#define PFM_CTX_UNLOADED      1     /* context is not loaded onto any task */
#define PFM_CTX_LOADED        2     /* context is loaded onto a task */
#define PFM_CTX_MASKED        3     /* context is loaded but monitoring is masked due to overflow */
#define PFM_CTX_ZOMBIE        4     /* owner of the context is closing it */

#define PFM_INVALID_ACTIVATION      (~0UL)

#define PFM_NUM_PMC_REGS      64    /* PMC save area for ctxsw */
#define PFM_NUM_PMD_REGS      64    /* PMD save area for ctxsw */

/*
 * depth of message queue
 */
#define PFM_MAX_MSGS          32
#define PFM_CTXQ_EMPTY(g)     ((g)->ctx_msgq_head == (g)->ctx_msgq_tail)

/*
 * type of a PMU register (bitmask).
 * bitmask structure:
 *    bit0   : register implemented
 *    bit1   : end marker
 *    bit2-3 : reserved
 *    bit4   : pmc has pmc.pm
 *    bit5   : pmc controls a counter (has pmc.oi), pmd is used as counter
 *    bit6-7 : register type
 *    bit8-31: reserved
 */
#define PFM_REG_NOTIMPL       0x0 /* not implemented at all */
#define PFM_REG_IMPL          0x1 /* register implemented */
#define PFM_REG_END           0x2 /* end marker */
#define PFM_REG_MONITOR       (0x1<<4|PFM_REG_IMPL) /* a PMC with a pmc.pm field only */
#define PFM_REG_COUNTING      (0x2<<4|PFM_REG_MONITOR) /* a monitor + pmc.oi+ PMD used as a counter */
#define PFM_REG_CONTROL       (0x4<<4|PFM_REG_IMPL) /* PMU control register */
#define     PFM_REG_CONFIG          (0x8<<4|PFM_REG_IMPL) /* configuration register */
#define PFM_REG_BUFFER        (0xc<<4|PFM_REG_IMPL) /* PMD used as buffer */

#define PMC_IS_LAST(i)  (pmu_conf->pmc_desc[i].type & PFM_REG_END)
#define PMD_IS_LAST(i)  (pmu_conf->pmd_desc[i].type & PFM_REG_END)

#define PMC_OVFL_NOTIFY(ctx, i)     ((ctx)->ctx_pmds[i].flags &  PFM_REGFL_OVFL_NOTIFY)

/* i assumed unsigned */
#define PMC_IS_IMPL(i)    (i< PMU_MAX_PMCS && (pmu_conf->pmc_desc[i].type & PFM_REG_IMPL))
#define PMD_IS_IMPL(i)    (i< PMU_MAX_PMDS && (pmu_conf->pmd_desc[i].type & PFM_REG_IMPL))

/* XXX: these assume that register i is implemented */
#define PMD_IS_COUNTING(i) ((pmu_conf->pmd_desc[i].type & PFM_REG_COUNTING) == PFM_REG_COUNTING)
#define PMC_IS_COUNTING(i) ((pmu_conf->pmc_desc[i].type & PFM_REG_COUNTING) == PFM_REG_COUNTING)
#define PMC_IS_MONITOR(i)  ((pmu_conf->pmc_desc[i].type & PFM_REG_MONITOR)  == PFM_REG_MONITOR)
#define PMC_IS_CONTROL(i)  ((pmu_conf->pmc_desc[i].type & PFM_REG_CONTROL)  == PFM_REG_CONTROL)

#define PMC_DFL_VAL(i)     pmu_conf->pmc_desc[i].default_value
#define PMC_RSVD_MASK(i)   pmu_conf->pmc_desc[i].reserved_mask
#define PMD_PMD_DEP(i)     pmu_conf->pmd_desc[i].dep_pmd[0]
#define PMC_PMD_DEP(i)     pmu_conf->pmc_desc[i].dep_pmd[0]

#define PFM_NUM_IBRS      IA64_NUM_DBG_REGS
#define PFM_NUM_DBRS      IA64_NUM_DBG_REGS

#define CTX_OVFL_NOBLOCK(c)   ((c)->ctx_fl_block == 0)
#define CTX_HAS_SMPL(c)       ((c)->ctx_fl_is_sampling)
#define PFM_CTX_TASK(h)       (h)->ctx_task

#define PMU_PMC_OI            5 /* position of pmc.oi bit */

/* XXX: does not support more than 64 PMDs */
#define CTX_USED_PMD(ctx, mask) (ctx)->ctx_used_pmds[0] |= (mask)
#define CTX_IS_USED_PMD(ctx, c) (((ctx)->ctx_used_pmds[0] & (1UL << (c))) != 0UL)

#define CTX_USED_MONITOR(ctx, mask) (ctx)->ctx_used_monitors[0] |= (mask)

#define CTX_USED_IBR(ctx,n)   (ctx)->ctx_used_ibrs[(n)>>6] |= 1UL<< ((n) % 64)
#define CTX_USED_DBR(ctx,n)   (ctx)->ctx_used_dbrs[(n)>>6] |= 1UL<< ((n) % 64)
#define CTX_USES_DBREGS(ctx)  (((pfm_context_t *)(ctx))->ctx_fl_using_dbreg==1)
#define PFM_CODE_RR     0     /* requesting code range restriction */
#define PFM_DATA_RR     1     /* requestion data range restriction */

#define PFM_CPUINFO_CLEAR(v)  pfm_get_cpu_var(pfm_syst_info) &= ~(v)
#define PFM_CPUINFO_SET(v)    pfm_get_cpu_var(pfm_syst_info) |= (v)
#define PFM_CPUINFO_GET()     pfm_get_cpu_var(pfm_syst_info)

#define RDEP(x)   (1UL<<(x))

/*
 * context protection macros
 * in SMP:
 *    - we need to protect against CPU concurrency (spin_lock)
 *    - we need to protect against PMU overflow interrupts (local_irq_disable)
 * in UP:
 *    - we need to protect against PMU overflow interrupts (local_irq_disable)
 *
 * spin_lock_irqsave()/spin_unlock_irqrestore():
 *    in SMP: local_irq_disable + spin_lock
 *    in UP : local_irq_disable
 *
 * spin_lock()/spin_lock():
 *    in UP : removed automatically
 *    in SMP: protect against context accesses from other CPU. interrupts
 *            are not masked. This is useful for the PMU interrupt handler
 *            because we know we will not get PMU concurrency in that code.
 */
#define PROTECT_CTX(c, f) \
      do {  \
            DPRINT(("spinlock_irq_save ctx %p by [%d]\n", c, task_pid_nr(current))); \
            spin_lock_irqsave(&(c)->ctx_lock, f); \
            DPRINT(("spinlocked ctx %p  by [%d]\n", c, task_pid_nr(current))); \
      } while(0)

#define UNPROTECT_CTX(c, f) \
      do { \
            DPRINT(("spinlock_irq_restore ctx %p by [%d]\n", c, task_pid_nr(current))); \
            spin_unlock_irqrestore(&(c)->ctx_lock, f); \
      } while(0)

#define PROTECT_CTX_NOPRINT(c, f) \
      do {  \
            spin_lock_irqsave(&(c)->ctx_lock, f); \
      } while(0)


#define UNPROTECT_CTX_NOPRINT(c, f) \
      do { \
            spin_unlock_irqrestore(&(c)->ctx_lock, f); \
      } while(0)


#define PROTECT_CTX_NOIRQ(c) \
      do {  \
            spin_lock(&(c)->ctx_lock); \
      } while(0)

#define UNPROTECT_CTX_NOIRQ(c) \
      do { \
            spin_unlock(&(c)->ctx_lock); \
      } while(0)


#ifdef CONFIG_SMP

#define GET_ACTIVATION()      pfm_get_cpu_var(pmu_activation_number)
#define INC_ACTIVATION()      pfm_get_cpu_var(pmu_activation_number)++
#define SET_ACTIVATION(c)     (c)->ctx_last_activation = GET_ACTIVATION()

#else /* !CONFIG_SMP */
#define SET_ACTIVATION(t)     do {} while(0)
#define GET_ACTIVATION(t)     do {} while(0)
#define INC_ACTIVATION(t)     do {} while(0)
#endif /* CONFIG_SMP */

#define SET_PMU_OWNER(t, c)   do { pfm_get_cpu_var(pmu_owner) = (t); pfm_get_cpu_var(pmu_ctx) = (c); } while(0)
#define GET_PMU_OWNER()       pfm_get_cpu_var(pmu_owner)
#define GET_PMU_CTX()         pfm_get_cpu_var(pmu_ctx)

#define LOCK_PFS(g)           spin_lock_irqsave(&pfm_sessions.pfs_lock, g)
#define UNLOCK_PFS(g)         spin_unlock_irqrestore(&pfm_sessions.pfs_lock, g)

#define PFM_REG_RETFLAG_SET(flags, val)   do { flags &= ~PFM_REG_RETFL_MASK; flags |= (val); } while(0)

/*
 * cmp0 must be the value of pmc0
 */
#define PMC0_HAS_OVFL(cmp0)  (cmp0 & ~0x1UL)

#define PFMFS_MAGIC 0xa0b4d889

/*
 * debugging
 */
#define PFM_DEBUGGING 1
#ifdef PFM_DEBUGGING
#define DPRINT(a) \
      do { \
            if (unlikely(pfm_sysctl.debug >0)) { printk("%s.%d: CPU%d [%d] ", __FUNCTION__, __LINE__, smp_processor_id(), task_pid_nr(current)); printk a; } \
      } while (0)

#define DPRINT_ovfl(a) \
      do { \
            if (unlikely(pfm_sysctl.debug > 0 && pfm_sysctl.debug_ovfl >0)) { printk("%s.%d: CPU%d [%d] ", __FUNCTION__, __LINE__, smp_processor_id(), task_pid_nr(current)); printk a; } \
      } while (0)
#endif

/*
 * 64-bit software counter structure
 *
 * the next_reset_type is applied to the next call to pfm_reset_regs()
 */
typedef struct {
      unsigned long     val;        /* virtual 64bit counter value */
      unsigned long     lval;       /* last reset value */
      unsigned long     long_reset; /* reset value on sampling overflow */
      unsigned long     short_reset;    /* reset value on overflow */
      unsigned long     reset_pmds[4];  /* which other pmds to reset when this counter overflows */
      unsigned long     smpl_pmds[4];   /* which pmds are accessed when counter overflow */
      unsigned long     seed;       /* seed for random-number generator */
      unsigned long     mask;       /* mask for random-number generator */
      unsigned int      flags;            /* notify/do not notify */
      unsigned long     eventid;    /* overflow event identifier */
} pfm_counter_t;

/*
 * context flags
 */
typedef struct {
      unsigned int block:1;         /* when 1, task will blocked on user notifications */
      unsigned int system:1;        /* do system wide monitoring */
      unsigned int using_dbreg:1;   /* using range restrictions (debug registers) */
      unsigned int is_sampling:1;   /* true if using a custom format */
      unsigned int excl_idle:1;     /* exclude idle task in system wide session */
      unsigned int going_zombie:1;  /* context is zombie (MASKED+blocking) */
      unsigned int trap_reason:2;   /* reason for going into pfm_handle_work() */
      unsigned int no_msg:1;        /* no message sent on overflow */
      unsigned int can_restart:1;   /* allowed to issue a PFM_RESTART */
      unsigned int reserved:22;
} pfm_context_flags_t;

#define PFM_TRAP_REASON_NONE        0x0   /* default value */
#define PFM_TRAP_REASON_BLOCK       0x1   /* we need to block on overflow */
#define PFM_TRAP_REASON_RESET       0x2   /* we need to reset PMDs */


/*
 * perfmon context: encapsulates all the state of a monitoring session
 */

typedef struct pfm_context {
      spinlock_t        ctx_lock;         /* context protection */

      pfm_context_flags_t     ctx_flags;        /* bitmask of flags  (block reason incl.) */
      unsigned int            ctx_state;        /* state: active/inactive (no bitfield) */

      struct task_struct      *ctx_task;        /* task to which context is attached */

      unsigned long           ctx_ovfl_regs[4]; /* which registers overflowed (notification) */

      struct completion ctx_restart_done;       /* use for blocking notification mode */

      unsigned long           ctx_used_pmds[4]; /* bitmask of PMD used            */
      unsigned long           ctx_all_pmds[4];  /* bitmask of all accessible PMDs */
      unsigned long           ctx_reload_pmds[4];     /* bitmask of force reload PMD on ctxsw in */

      unsigned long           ctx_all_pmcs[4];  /* bitmask of all accessible PMCs */
      unsigned long           ctx_reload_pmcs[4];     /* bitmask of force reload PMC on ctxsw in */
      unsigned long           ctx_used_monitors[4];   /* bitmask of monitor PMC being used */

      unsigned long           ctx_pmcs[PFM_NUM_PMC_REGS];   /*  saved copies of PMC values */

      unsigned int            ctx_used_ibrs[1];       /* bitmask of used IBR (speedup ctxsw in) */
      unsigned int            ctx_used_dbrs[1];       /* bitmask of used DBR (speedup ctxsw in) */
      unsigned long           ctx_dbrs[IA64_NUM_DBG_REGS];  /* DBR values (cache) when not loaded */
      unsigned long           ctx_ibrs[IA64_NUM_DBG_REGS];  /* IBR values (cache) when not loaded */

      pfm_counter_t           ctx_pmds[PFM_NUM_PMD_REGS]; /* software state for PMDS */

      unsigned long           th_pmcs[PFM_NUM_PMC_REGS];    /* PMC thread save state */
      unsigned long           th_pmds[PFM_NUM_PMD_REGS];    /* PMD thread save state */

      u64               ctx_saved_psr_up; /* only contains psr.up value */

      unsigned long           ctx_last_activation;    /* context last activation number for last_cpu */
      unsigned int            ctx_last_cpu;           /* CPU id of current or last CPU used (SMP only) */
      unsigned int            ctx_cpu;          /* cpu to which perfmon is applied (system wide) */

      int               ctx_fd;                 /* file descriptor used my this context */
      pfm_ovfl_arg_t          ctx_ovfl_arg;           /* argument to custom buffer format handler */

      pfm_buffer_fmt_t  *ctx_buf_fmt;           /* buffer format callbacks */
      void              *ctx_smpl_hdr;          /* points to sampling buffer header kernel vaddr */
      unsigned long           ctx_smpl_size;          /* size of sampling buffer */
      void              *ctx_smpl_vaddr;  /* user level virtual address of smpl buffer */

      wait_queue_head_t       ctx_msgq_wait;
      pfm_msg_t         ctx_msgq[PFM_MAX_MSGS];
      int               ctx_msgq_head;
      int               ctx_msgq_tail;
      struct fasync_struct    *ctx_async_queue;

      wait_queue_head_t       ctx_zombieq;            /* termination cleanup wait queue */
} pfm_context_t;

/*
 * magic number used to verify that structure is really
 * a perfmon context
 */
#define PFM_IS_FILE(f)        ((f)->f_op == &pfm_file_ops)

#define PFM_GET_CTX(t)        ((pfm_context_t *)(t)->thread.pfm_context)

#ifdef CONFIG_SMP
#define SET_LAST_CPU(ctx, v)  (ctx)->ctx_last_cpu = (v)
#define GET_LAST_CPU(ctx)     (ctx)->ctx_last_cpu
#else
#define SET_LAST_CPU(ctx, v)  do {} while(0)
#define GET_LAST_CPU(ctx)     do {} while(0)
#endif


#define ctx_fl_block          ctx_flags.block
#define ctx_fl_system         ctx_flags.system
#define ctx_fl_using_dbreg    ctx_flags.using_dbreg
#define ctx_fl_is_sampling    ctx_flags.is_sampling
#define ctx_fl_excl_idle      ctx_flags.excl_idle
#define ctx_fl_going_zombie   ctx_flags.going_zombie
#define ctx_fl_trap_reason    ctx_flags.trap_reason
#define ctx_fl_no_msg         ctx_flags.no_msg
#define ctx_fl_can_restart    ctx_flags.can_restart

#define PFM_SET_WORK_PENDING(t, v)  do { (t)->thread.pfm_needs_checking = v; } while(0);
#define PFM_GET_WORK_PENDING(t)           (t)->thread.pfm_needs_checking

/*
 * global information about all sessions
 * mostly used to synchronize between system wide and per-process
 */
typedef struct {
      spinlock_t        pfs_lock;            /* lock the structure */

      unsigned int            pfs_task_sessions;         /* number of per task sessions */
      unsigned int            pfs_sys_sessions;    /* number of per system wide sessions */
      unsigned int            pfs_sys_use_dbregs;        /* incremented when a system wide session uses debug regs */
      unsigned int            pfs_ptrace_use_dbregs;     /* incremented when a process uses debug regs */
      struct task_struct      *pfs_sys_session[NR_CPUS]; /* point to task owning a system-wide session */
} pfm_session_t;

/*
 * information about a PMC or PMD.
 * dep_pmd[]: a bitmask of dependent PMD registers
 * dep_pmc[]: a bitmask of dependent PMC registers
 */
typedef int (*pfm_reg_check_t)(struct task_struct *task, pfm_context_t *ctx, unsigned int cnum, unsigned long *val, struct pt_regs *regs);
typedef struct {
      unsigned int            type;
      int               pm_pos;
      unsigned long           default_value;    /* power-on default value */
      unsigned long           reserved_mask;    /* bitmask of reserved bits */
      pfm_reg_check_t         read_check;
      pfm_reg_check_t         write_check;
      unsigned long           dep_pmd[4];
      unsigned long           dep_pmc[4];
} pfm_reg_desc_t;

/* assume cnum is a valid monitor */
#define PMC_PM(cnum, val)     (((val) >> (pmu_conf->pmc_desc[cnum].pm_pos)) & 0x1)

/*
 * This structure is initialized at boot time and contains
 * a description of the PMU main characteristics.
 *
 * If the probe function is defined, detection is based
 * on its return value: 
 *    - 0 means recognized PMU
 *    - anything else means not supported
 * When the probe function is not defined, then the pmu_family field
 * is used and it must match the host CPU family such that:
 *    - cpu->family & config->pmu_family != 0
 */
typedef struct {
      unsigned long  ovfl_val;      /* overflow value for counters */

      pfm_reg_desc_t *pmc_desc;     /* detailed PMC register dependencies descriptions */
      pfm_reg_desc_t *pmd_desc;     /* detailed PMD register dependencies descriptions */

      unsigned int   num_pmcs;      /* number of PMCS: computed at init time */
      unsigned int   num_pmds;      /* number of PMDS: computed at init time */
      unsigned long  impl_pmcs[4];  /* bitmask of implemented PMCS */
      unsigned long  impl_pmds[4];  /* bitmask of implemented PMDS */

      char        *pmu_name;  /* PMU family name */
      unsigned int  pmu_family;     /* cpuid family pattern used to identify pmu */
      unsigned int  flags;          /* pmu specific flags */
      unsigned int  num_ibrs;       /* number of IBRS: computed at init time */
      unsigned int  num_dbrs;       /* number of DBRS: computed at init time */
      unsigned int  num_counters;   /* PMC/PMD counting pairs : computed at init time */
      int           (*probe)(void);   /* customized probe routine */
      unsigned int  use_rr_dbregs:1;      /* set if debug registers used for range restriction */
} pmu_config_t;
/*
 * PMU specific flags
 */
#define PFM_PMU_IRQ_RESEND    1     /* PMU needs explicit IRQ resend */

/*
 * debug register related type definitions
 */
typedef struct {
      unsigned long ibr_mask:56;
      unsigned long ibr_plm:4;
      unsigned long ibr_ig:3;
      unsigned long ibr_x:1;
} ibr_mask_reg_t;

typedef struct {
      unsigned long dbr_mask:56;
      unsigned long dbr_plm:4;
      unsigned long dbr_ig:2;
      unsigned long dbr_w:1;
      unsigned long dbr_r:1;
} dbr_mask_reg_t;

typedef union {
      unsigned long  val;
      ibr_mask_reg_t ibr;
      dbr_mask_reg_t dbr;
} dbreg_t;


/*
 * perfmon command descriptions
 */
typedef struct {
      int         (*cmd_func)(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs);
      char        *cmd_name;
      int         cmd_flags;
      unsigned int      cmd_narg;
      size_t            cmd_argsize;
      int         (*cmd_getsize)(void *arg, size_t *sz);
} pfm_cmd_desc_t;

#define PFM_CMD_FD            0x01  /* command requires a file descriptor */
#define PFM_CMD_ARG_READ      0x02  /* command must read argument(s) */
#define PFM_CMD_ARG_RW        0x04  /* command must read/write argument(s) */
#define PFM_CMD_STOP          0x08  /* command does not work on zombie context */


#define PFM_CMD_NAME(cmd)     pfm_cmd_tab[(cmd)].cmd_name
#define PFM_CMD_READ_ARG(cmd) (pfm_cmd_tab[(cmd)].cmd_flags & PFM_CMD_ARG_READ)
#define PFM_CMD_RW_ARG(cmd)   (pfm_cmd_tab[(cmd)].cmd_flags & PFM_CMD_ARG_RW)
#define PFM_CMD_USE_FD(cmd)   (pfm_cmd_tab[(cmd)].cmd_flags & PFM_CMD_FD)
#define PFM_CMD_STOPPED(cmd)  (pfm_cmd_tab[(cmd)].cmd_flags & PFM_CMD_STOP)

#define PFM_CMD_ARG_MANY      -1 /* cannot be zero */

typedef struct {
      unsigned long pfm_spurious_ovfl_intr_count;     /* keep track of spurious ovfl interrupts */
      unsigned long pfm_replay_ovfl_intr_count; /* keep track of replayed ovfl interrupts */
      unsigned long pfm_ovfl_intr_count;        /* keep track of ovfl interrupts */
      unsigned long pfm_ovfl_intr_cycles;       /* cycles spent processing ovfl interrupts */
      unsigned long pfm_ovfl_intr_cycles_min;         /* min cycles spent processing ovfl interrupts */
      unsigned long pfm_ovfl_intr_cycles_max;         /* max cycles spent processing ovfl interrupts */
      unsigned long pfm_smpl_handler_calls;
      unsigned long pfm_smpl_handler_cycles;
      char pad[SMP_CACHE_BYTES] ____cacheline_aligned;
} pfm_stats_t;

/*
 * perfmon internal variables
 */
static pfm_stats_t            pfm_stats[NR_CPUS];
static pfm_session_t          pfm_sessions;     /* global sessions information */

static DEFINE_SPINLOCK(pfm_alt_install_check);
static pfm_intr_handler_desc_t  *pfm_alt_intr_handler;

static struct proc_dir_entry  *perfmon_dir;
static pfm_uuid_t       pfm_null_uuid = {0,};

static spinlock_t       pfm_buffer_fmt_lock;
static LIST_HEAD(pfm_buffer_fmt_list);

static pmu_config_t           *pmu_conf;

/* sysctl() controls */
pfm_sysctl_t pfm_sysctl;
EXPORT_SYMBOL(pfm_sysctl);

static ctl_table pfm_ctl_table[]={
      {
            .ctl_name   = CTL_UNNUMBERED,
            .procname   = "debug",
            .data       = &pfm_sysctl.debug,
            .maxlen           = sizeof(int),
            .mode       = 0666,
            .proc_handler     = &proc_dointvec,
      },
      {
            .ctl_name   = CTL_UNNUMBERED,
            .procname   = "debug_ovfl",
            .data       = &pfm_sysctl.debug_ovfl,
            .maxlen           = sizeof(int),
            .mode       = 0666,
            .proc_handler     = &proc_dointvec,
      },
      {
            .ctl_name   = CTL_UNNUMBERED,
            .procname   = "fastctxsw",
            .data       = &pfm_sysctl.fastctxsw,
            .maxlen           = sizeof(int),
            .mode       = 0600,
            .proc_handler     =  &proc_dointvec,
      },
      {
            .ctl_name   = CTL_UNNUMBERED,
            .procname   = "expert_mode",
            .data       = &pfm_sysctl.expert_mode,
            .maxlen           = sizeof(int),
            .mode       = 0600,
            .proc_handler     = &proc_dointvec,
      },
      {}
};
static ctl_table pfm_sysctl_dir[] = {
      {
            .ctl_name   = CTL_UNNUMBERED,
            .procname   = "perfmon",
            .mode       = 0555,
            .child            = pfm_ctl_table,
      },
      {}
};
static ctl_table pfm_sysctl_root[] = {
      {
            .ctl_name   = CTL_KERN,
            .procname   = "kernel",
            .mode       = 0555,
            .child            = pfm_sysctl_dir,
      },
      {}
};
static struct ctl_table_header *pfm_sysctl_header;

static int pfm_context_unload(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs);

#define pfm_get_cpu_var(v)          __ia64_per_cpu_var(v)
#define pfm_get_cpu_data(a,b)       per_cpu(a, b)

static inline void
pfm_put_task(struct task_struct *task)
{
      if (task != current) put_task_struct(task);
}

static inline void
pfm_set_task_notify(struct task_struct *task)
{
      struct thread_info *info;

      info = (struct thread_info *) ((char *) task + IA64_TASK_SIZE);
      set_bit(TIF_PERFMON_WORK, &info->flags);
}

static inline void
pfm_clear_task_notify(void)
{
      clear_thread_flag(TIF_PERFMON_WORK);
}

static inline void
pfm_reserve_page(unsigned long a)
{
      SetPageReserved(vmalloc_to_page((void *)a));
}
static inline void
pfm_unreserve_page(unsigned long a)
{
      ClearPageReserved(vmalloc_to_page((void*)a));
}

static inline unsigned long
pfm_protect_ctx_ctxsw(pfm_context_t *x)
{
      spin_lock(&(x)->ctx_lock);
      return 0UL;
}

static inline void
pfm_unprotect_ctx_ctxsw(pfm_context_t *x, unsigned long f)
{
      spin_unlock(&(x)->ctx_lock);
}

static inline unsigned int
pfm_do_munmap(struct mm_struct *mm, unsigned long addr, size_t len, int acct)
{
      return do_munmap(mm, addr, len);
}

static inline unsigned long 
pfm_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags, unsigned long exec)
{
      return get_unmapped_area(file, addr, len, pgoff, flags);
}


static int
pfmfs_get_sb(struct file_system_type *fs_type, int flags, const char *dev_name, void *data,
           struct vfsmount *mnt)
{
      return get_sb_pseudo(fs_type, "pfm:", NULL, PFMFS_MAGIC, mnt);
}

static struct file_system_type pfm_fs_type = {
      .name     = "pfmfs",
      .get_sb   = pfmfs_get_sb,
      .kill_sb  = kill_anon_super,
};

DEFINE_PER_CPU(unsigned long, pfm_syst_info);
DEFINE_PER_CPU(struct task_struct *, pmu_owner);
DEFINE_PER_CPU(pfm_context_t  *, pmu_ctx);
DEFINE_PER_CPU(unsigned long, pmu_activation_number);
EXPORT_PER_CPU_SYMBOL_GPL(pfm_syst_info);


/* forward declaration */
static const struct file_operations pfm_file_ops;

/*
 * forward declarations
 */
#ifndef CONFIG_SMP
static void pfm_lazy_save_regs (struct task_struct *ta);
#endif

void dump_pmu_state(const char *);
static int pfm_write_ibr_dbr(int mode, pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs);

#include "perfmon_itanium.h"
#include "perfmon_mckinley.h"
#include "perfmon_montecito.h"
#include "perfmon_generic.h"

static pmu_config_t *pmu_confs[]={
      &pmu_conf_mont,
      &pmu_conf_mck,
      &pmu_conf_ita,
      &pmu_conf_gen, /* must be last */
      NULL
};


static int pfm_end_notify_user(pfm_context_t *ctx);

static inline void
pfm_clear_psr_pp(void)
{
      ia64_rsm(IA64_PSR_PP);
      ia64_srlz_i();
}

static inline void
pfm_set_psr_pp(void)
{
      ia64_ssm(IA64_PSR_PP);
      ia64_srlz_i();
}

static inline void
pfm_clear_psr_up(void)
{
      ia64_rsm(IA64_PSR_UP);
      ia64_srlz_i();
}

static inline void
pfm_set_psr_up(void)
{
      ia64_ssm(IA64_PSR_UP);
      ia64_srlz_i();
}

static inline unsigned long
pfm_get_psr(void)
{
      unsigned long tmp;
      tmp = ia64_getreg(_IA64_REG_PSR);
      ia64_srlz_i();
      return tmp;
}

static inline void
pfm_set_psr_l(unsigned long val)
{
      ia64_setreg(_IA64_REG_PSR_L, val);
      ia64_srlz_i();
}

static inline void
pfm_freeze_pmu(void)
{
      ia64_set_pmc(0,1UL);
      ia64_srlz_d();
}

static inline void
pfm_unfreeze_pmu(void)
{
      ia64_set_pmc(0,0UL);
      ia64_srlz_d();
}

static inline void
pfm_restore_ibrs(unsigned long *ibrs, unsigned int nibrs)
{
      int i;

      for (i=0; i < nibrs; i++) {
            ia64_set_ibr(i, ibrs[i]);
            ia64_dv_serialize_instruction();
      }
      ia64_srlz_i();
}

static inline void
pfm_restore_dbrs(unsigned long *dbrs, unsigned int ndbrs)
{
      int i;

      for (i=0; i < ndbrs; i++) {
            ia64_set_dbr(i, dbrs[i]);
            ia64_dv_serialize_data();
      }
      ia64_srlz_d();
}

/*
 * PMD[i] must be a counter. no check is made
 */
static inline unsigned long
pfm_read_soft_counter(pfm_context_t *ctx, int i)
{
      return ctx->ctx_pmds[i].val + (ia64_get_pmd(i) & pmu_conf->ovfl_val);
}

/*
 * PMD[i] must be a counter. no check is made
 */
static inline void
pfm_write_soft_counter(pfm_context_t *ctx, int i, unsigned long val)
{
      unsigned long ovfl_val = pmu_conf->ovfl_val;

      ctx->ctx_pmds[i].val = val  & ~ovfl_val;
      /*
       * writing to unimplemented part is ignore, so we do not need to
       * mask off top part
       */
      ia64_set_pmd(i, val & ovfl_val);
}

static pfm_msg_t *
pfm_get_new_msg(pfm_context_t *ctx)
{
      int idx, next;

      next = (ctx->ctx_msgq_tail+1) % PFM_MAX_MSGS;

      DPRINT(("ctx_fd=%p head=%d tail=%d\n", ctx, ctx->ctx_msgq_head, ctx->ctx_msgq_tail));
      if (next == ctx->ctx_msgq_head) return NULL;

      idx =       ctx->ctx_msgq_tail;
      ctx->ctx_msgq_tail = next;

      DPRINT(("ctx=%p head=%d tail=%d msg=%d\n", ctx, ctx->ctx_msgq_head, ctx->ctx_msgq_tail, idx));

      return ctx->ctx_msgq+idx;
}

static pfm_msg_t *
pfm_get_next_msg(pfm_context_t *ctx)
{
      pfm_msg_t *msg;

      DPRINT(("ctx=%p head=%d tail=%d\n", ctx, ctx->ctx_msgq_head, ctx->ctx_msgq_tail));

      if (PFM_CTXQ_EMPTY(ctx)) return NULL;

      /*
       * get oldest message
       */
      msg = ctx->ctx_msgq+ctx->ctx_msgq_head;

      /*
       * and move forward
       */
      ctx->ctx_msgq_head = (ctx->ctx_msgq_head+1) % PFM_MAX_MSGS;

      DPRINT(("ctx=%p head=%d tail=%d type=%d\n", ctx, ctx->ctx_msgq_head, ctx->ctx_msgq_tail, msg->pfm_gen_msg.msg_type));

      return msg;
}

static void
pfm_reset_msgq(pfm_context_t *ctx)
{
      ctx->ctx_msgq_head = ctx->ctx_msgq_tail = 0;
      DPRINT(("ctx=%p msgq reset\n", ctx));
}

static void *
pfm_rvmalloc(unsigned long size)
{
      void *mem;
      unsigned long addr;

      size = PAGE_ALIGN(size);
      mem  = vmalloc(size);
      if (mem) {
            //printk("perfmon: CPU%d pfm_rvmalloc(%ld)=%p\n", smp_processor_id(), size, mem);
            memset(mem, 0, size);
            addr = (unsigned long)mem;
            while (size > 0) {
                  pfm_reserve_page(addr);
                  addr+=PAGE_SIZE;
                  size-=PAGE_SIZE;
            }
      }
      return mem;
}

static void
pfm_rvfree(void *mem, unsigned long size)
{
      unsigned long addr;

      if (mem) {
            DPRINT(("freeing physical buffer @%p size=%lu\n", mem, size));
            addr = (unsigned long) mem;
            while ((long) size > 0) {
                  pfm_unreserve_page(addr);
                  addr+=PAGE_SIZE;
                  size-=PAGE_SIZE;
            }
            vfree(mem);
      }
      return;
}

static pfm_context_t *
pfm_context_alloc(void)
{
      pfm_context_t *ctx;

      /* 
       * allocate context descriptor 
       * must be able to free with interrupts disabled
       */
      ctx = kzalloc(sizeof(pfm_context_t), GFP_KERNEL);
      if (ctx) {
            DPRINT(("alloc ctx @%p\n", ctx));
      }
      return ctx;
}

static void
pfm_context_free(pfm_context_t *ctx)
{
      if (ctx) {
            DPRINT(("free ctx @%p\n", ctx));
            kfree(ctx);
      }
}

static void
pfm_mask_monitoring(struct task_struct *task)
{
      pfm_context_t *ctx = PFM_GET_CTX(task);
      unsigned long mask, val, ovfl_mask;
      int i;

      DPRINT_ovfl(("masking monitoring for [%d]\n", task_pid_nr(task)));

      ovfl_mask = pmu_conf->ovfl_val;
      /*
       * monitoring can only be masked as a result of a valid
       * counter overflow. In UP, it means that the PMU still
       * has an owner. Note that the owner can be different
       * from the current task. However the PMU state belongs
       * to the owner.
       * In SMP, a valid overflow only happens when task is
       * current. Therefore if we come here, we know that
       * the PMU state belongs to the current task, therefore
       * we can access the live registers.
       *
       * So in both cases, the live register contains the owner's
       * state. We can ONLY touch the PMU registers and NOT the PSR.
       *
       * As a consequence to this call, the ctx->th_pmds[] array
       * contains stale information which must be ignored
       * when context is reloaded AND monitoring is active (see
       * pfm_restart).
       */
      mask = ctx->ctx_used_pmds[0];
      for (i = 0; mask; i++, mask>>=1) {
            /* skip non used pmds */
            if ((mask & 0x1) == 0) continue;
            val = ia64_get_pmd(i);

            if (PMD_IS_COUNTING(i)) {
                  /*
                   * we rebuild the full 64 bit value of the counter
                   */
                  ctx->ctx_pmds[i].val += (val & ovfl_mask);
            } else {
                  ctx->ctx_pmds[i].val = val;
            }
            DPRINT_ovfl(("pmd[%d]=0x%lx hw_pmd=0x%lx\n",
                  i,
                  ctx->ctx_pmds[i].val,
                  val & ovfl_mask));
      }
      /*
       * mask monitoring by setting the privilege level to 0
       * we cannot use psr.pp/psr.up for this, it is controlled by
       * the user
       *
       * if task is current, modify actual registers, otherwise modify
       * thread save state, i.e., what will be restored in pfm_load_regs()
       */
      mask = ctx->ctx_used_monitors[0] >> PMU_FIRST_COUNTER;
      for(i= PMU_FIRST_COUNTER; mask; i++, mask>>=1) {
            if ((mask & 0x1) == 0UL) continue;
            ia64_set_pmc(i, ctx->th_pmcs[i] & ~0xfUL);
            ctx->th_pmcs[i] &= ~0xfUL;
            DPRINT_ovfl(("pmc[%d]=0x%lx\n", i, ctx->th_pmcs[i]));
      }
      /*
       * make all of this visible
       */
      ia64_srlz_d();
}

/*
 * must always be done with task == current
 *
 * context must be in MASKED state when calling
 */
static void
pfm_restore_monitoring(struct task_struct *task)
{
      pfm_context_t *ctx = PFM_GET_CTX(task);
      unsigned long mask, ovfl_mask;
      unsigned long psr, val;
      int i, is_system;

      is_system = ctx->ctx_fl_system;
      ovfl_mask = pmu_conf->ovfl_val;

      if (task != current) {
            printk(KERN_ERR "perfmon.%d: invalid task[%d] current[%d]\n", __LINE__, task_pid_nr(task), task_pid_nr(current));
            return;
      }
      if (ctx->ctx_state != PFM_CTX_MASKED) {
            printk(KERN_ERR "perfmon.%d: task[%d] current[%d] invalid state=%d\n", __LINE__,
                  task_pid_nr(task), task_pid_nr(current), ctx->ctx_state);
            return;
      }
      psr = pfm_get_psr();
      /*
       * monitoring is masked via the PMC.
       * As we restore their value, we do not want each counter to
       * restart right away. We stop monitoring using the PSR,
       * restore the PMC (and PMD) and then re-establish the psr
       * as it was. Note that there can be no pending overflow at
       * this point, because monitoring was MASKED.
       *
       * system-wide session are pinned and self-monitoring
       */
      if (is_system && (PFM_CPUINFO_GET() & PFM_CPUINFO_DCR_PP)) {
            /* disable dcr pp */
            ia64_setreg(_IA64_REG_CR_DCR, ia64_getreg(_IA64_REG_CR_DCR) & ~IA64_DCR_PP);
            pfm_clear_psr_pp();
      } else {
            pfm_clear_psr_up();
      }
      /*
       * first, we restore the PMD
       */
      mask = ctx->ctx_used_pmds[0];
      for (i = 0; mask; i++, mask>>=1) {
            /* skip non used pmds */
            if ((mask & 0x1) == 0) continue;

            if (PMD_IS_COUNTING(i)) {
                  /*
                   * we split the 64bit value according to
                   * counter width
                   */
                  val = ctx->ctx_pmds[i].val & ovfl_mask;
                  ctx->ctx_pmds[i].val &= ~ovfl_mask;
            } else {
                  val = ctx->ctx_pmds[i].val;
            }
            ia64_set_pmd(i, val);

            DPRINT(("pmd[%d]=0x%lx hw_pmd=0x%lx\n",
                  i,
                  ctx->ctx_pmds[i].val,
                  val));
      }
      /*
       * restore the PMCs
       */
      mask = ctx->ctx_used_monitors[0] >> PMU_FIRST_COUNTER;
      for(i= PMU_FIRST_COUNTER; mask; i++, mask>>=1) {
            if ((mask & 0x1) == 0UL) continue;
            ctx->th_pmcs[i] = ctx->ctx_pmcs[i];
            ia64_set_pmc(i, ctx->th_pmcs[i]);
            DPRINT(("[%d] pmc[%d]=0x%lx\n",
                              task_pid_nr(task), i, ctx->th_pmcs[i]));
      }
      ia64_srlz_d();

      /*
       * must restore DBR/IBR because could be modified while masked
       * XXX: need to optimize 
       */
      if (ctx->ctx_fl_using_dbreg) {
            pfm_restore_ibrs(ctx->ctx_ibrs, pmu_conf->num_ibrs);
            pfm_restore_dbrs(ctx->ctx_dbrs, pmu_conf->num_dbrs);
      }

      /*
       * now restore PSR
       */
      if (is_system && (PFM_CPUINFO_GET() & PFM_CPUINFO_DCR_PP)) {
            /* enable dcr pp */
            ia64_setreg(_IA64_REG_CR_DCR, ia64_getreg(_IA64_REG_CR_DCR) | IA64_DCR_PP);
            ia64_srlz_i();
      }
      pfm_set_psr_l(psr);
}

static inline void
pfm_save_pmds(unsigned long *pmds, unsigned long mask)
{
      int i;

      ia64_srlz_d();

      for (i=0; mask; i++, mask>>=1) {
            if (mask & 0x1) pmds[i] = ia64_get_pmd(i);
      }
}

/*
 * reload from thread state (used for ctxw only)
 */
static inline void
pfm_restore_pmds(unsigned long *pmds, unsigned long mask)
{
      int i;
      unsigned long val, ovfl_val = pmu_conf->ovfl_val;

      for (i=0; mask; i++, mask>>=1) {
            if ((mask & 0x1) == 0) continue;
            val = PMD_IS_COUNTING(i) ? pmds[i] & ovfl_val : pmds[i];
            ia64_set_pmd(i, val);
      }
      ia64_srlz_d();
}

/*
 * propagate PMD from context to thread-state
 */
static inline void
pfm_copy_pmds(struct task_struct *task, pfm_context_t *ctx)
{
      unsigned long ovfl_val = pmu_conf->ovfl_val;
      unsigned long mask = ctx->ctx_all_pmds[0];
      unsigned long val;
      int i;

      DPRINT(("mask=0x%lx\n", mask));

      for (i=0; mask; i++, mask>>=1) {

            val = ctx->ctx_pmds[i].val;

            /*
             * We break up the 64 bit value into 2 pieces
             * the lower bits go to the machine state in the
             * thread (will be reloaded on ctxsw in).
             * The upper part stays in the soft-counter.
             */
            if (PMD_IS_COUNTING(i)) {
                  ctx->ctx_pmds[i].val = val & ~ovfl_val;
                   val &= ovfl_val;
            }
            ctx->th_pmds[i] = val;

            DPRINT(("pmd[%d]=0x%lx soft_val=0x%lx\n",
                  i,
                  ctx->th_pmds[i],
                  ctx->ctx_pmds[i].val));
      }
}

/*
 * propagate PMC from context to thread-state
 */
static inline void
pfm_copy_pmcs(struct task_struct *task, pfm_context_t *ctx)
{
      unsigned long mask = ctx->ctx_all_pmcs[0];
      int i;

      DPRINT(("mask=0x%lx\n", mask));

      for (i=0; mask; i++, mask>>=1) {
            /* masking 0 with ovfl_val yields 0 */
            ctx->th_pmcs[i] = ctx->ctx_pmcs[i];
            DPRINT(("pmc[%d]=0x%lx\n", i, ctx->th_pmcs[i]));
      }
}



static inline void
pfm_restore_pmcs(unsigned long *pmcs, unsigned long mask)
{
      int i;

      for (i=0; mask; i++, mask>>=1) {
            if ((mask & 0x1) == 0) continue;
            ia64_set_pmc(i, pmcs[i]);
      }
      ia64_srlz_d();
}

static inline int
pfm_uuid_cmp(pfm_uuid_t a, pfm_uuid_t b)
{
      return memcmp(a, b, sizeof(pfm_uuid_t));
}

static inline int
pfm_buf_fmt_exit(pfm_buffer_fmt_t *fmt, struct task_struct *task, void *buf, struct pt_regs *regs)
{
      int ret = 0;
      if (fmt->fmt_exit) ret = (*fmt->fmt_exit)(task, buf, regs);
      return ret;
}

static inline int
pfm_buf_fmt_getsize(pfm_buffer_fmt_t *fmt, struct task_struct *task, unsigned int flags, int cpu, void *arg, unsigned long *size)
{
      int ret = 0;
      if (fmt->fmt_getsize) ret = (*fmt->fmt_getsize)(task, flags, cpu, arg, size);
      return ret;
}


static inline int
pfm_buf_fmt_validate(pfm_buffer_fmt_t *fmt, struct task_struct *task, unsigned int flags,
                 int cpu, void *arg)
{
      int ret = 0;
      if (fmt->fmt_validate) ret = (*fmt->fmt_validate)(task, flags, cpu, arg);
      return ret;
}

static inline int
pfm_buf_fmt_init(pfm_buffer_fmt_t *fmt, struct task_struct *task, void *buf, unsigned int flags,
                 int cpu, void *arg)
{
      int ret = 0;
      if (fmt->fmt_init) ret = (*fmt->fmt_init)(task, buf, flags, cpu, arg);
      return ret;
}

static inline int
pfm_buf_fmt_restart(pfm_buffer_fmt_t *fmt, struct task_struct *task, pfm_ovfl_ctrl_t *ctrl, void *buf, struct pt_regs *regs)
{
      int ret = 0;
      if (fmt->fmt_restart) ret = (*fmt->fmt_restart)(task, ctrl, buf, regs);
      return ret;
}

static inline int
pfm_buf_fmt_restart_active(pfm_buffer_fmt_t *fmt, struct task_struct *task, pfm_ovfl_ctrl_t *ctrl, void *buf, struct pt_regs *regs)
{
      int ret = 0;
      if (fmt->fmt_restart_active) ret = (*fmt->fmt_restart_active)(task, ctrl, buf, regs);
      return ret;
}

static pfm_buffer_fmt_t *
__pfm_find_buffer_fmt(pfm_uuid_t uuid)
{
      struct list_head * pos;
      pfm_buffer_fmt_t * entry;

      list_for_each(pos, &pfm_buffer_fmt_list) {
            entry = list_entry(pos, pfm_buffer_fmt_t, fmt_list);
            if (pfm_uuid_cmp(uuid, entry->fmt_uuid) == 0)
                  return entry;
      }
      return NULL;
}
 
/*
 * find a buffer format based on its uuid
 */
static pfm_buffer_fmt_t *
pfm_find_buffer_fmt(pfm_uuid_t uuid)
{
      pfm_buffer_fmt_t * fmt;
      spin_lock(&pfm_buffer_fmt_lock);
      fmt = __pfm_find_buffer_fmt(uuid);
      spin_unlock(&pfm_buffer_fmt_lock);
      return fmt;
}
 
int
pfm_register_buffer_fmt(pfm_buffer_fmt_t *fmt)
{
      int ret = 0;

      /* some sanity checks */
      if (fmt == NULL || fmt->fmt_name == NULL) return -EINVAL;

      /* we need at least a handler */
      if (fmt->fmt_handler == NULL) return -EINVAL;

      /*
       * XXX: need check validity of fmt_arg_size
       */

      spin_lock(&pfm_buffer_fmt_lock);

      if (__pfm_find_buffer_fmt(fmt->fmt_uuid)) {
            printk(KERN_ERR "perfmon: duplicate sampling format: %s\n", fmt->fmt_name);
            ret = -EBUSY;
            goto out;
      } 
      list_add(&fmt->fmt_list, &pfm_buffer_fmt_list);
      printk(KERN_INFO "perfmon: added sampling format %s\n", fmt->fmt_name);

out:
      spin_unlock(&pfm_buffer_fmt_lock);
      return ret;
}
EXPORT_SYMBOL(pfm_register_buffer_fmt);

int
pfm_unregister_buffer_fmt(pfm_uuid_t uuid)
{
      pfm_buffer_fmt_t *fmt;
      int ret = 0;

      spin_lock(&pfm_buffer_fmt_lock);

      fmt = __pfm_find_buffer_fmt(uuid);
      if (!fmt) {
            printk(KERN_ERR "perfmon: cannot unregister format, not found\n");
            ret = -EINVAL;
            goto out;
      }
      list_del_init(&fmt->fmt_list);
      printk(KERN_INFO "perfmon: removed sampling format: %s\n", fmt->fmt_name);

out:
      spin_unlock(&pfm_buffer_fmt_lock);
      return ret;

}
EXPORT_SYMBOL(pfm_unregister_buffer_fmt);

extern void update_pal_halt_status(int);

static int
pfm_reserve_session(struct task_struct *task, int is_syswide, unsigned int cpu)
{
      unsigned long flags;
      /*
       * validity checks on cpu_mask have been done upstream
       */
      LOCK_PFS(flags);

      DPRINT(("in sys_sessions=%u task_sessions=%u dbregs=%u syswide=%d cpu=%u\n",
            pfm_sessions.pfs_sys_sessions,
            pfm_sessions.pfs_task_sessions,
            pfm_sessions.pfs_sys_use_dbregs,
            is_syswide,
            cpu));

      if (is_syswide) {
            /*
             * cannot mix system wide and per-task sessions
             */
            if (pfm_sessions.pfs_task_sessions > 0UL) {
                  DPRINT(("system wide not possible, %u conflicting task_sessions\n",
                        pfm_sessions.pfs_task_sessions));
                  goto abort;
            }

            if (pfm_sessions.pfs_sys_session[cpu]) goto error_conflict;

            DPRINT(("reserving system wide session on CPU%u currently on CPU%u\n", cpu, smp_processor_id()));

            pfm_sessions.pfs_sys_session[cpu] = task;

            pfm_sessions.pfs_sys_sessions++ ;

      } else {
            if (pfm_sessions.pfs_sys_sessions) goto abort;
            pfm_sessions.pfs_task_sessions++;
      }

      DPRINT(("out sys_sessions=%u task_sessions=%u dbregs=%u syswide=%d cpu=%u\n",
            pfm_sessions.pfs_sys_sessions,
            pfm_sessions.pfs_task_sessions,
            pfm_sessions.pfs_sys_use_dbregs,
            is_syswide,
            cpu));

      /*
       * disable default_idle() to go to PAL_HALT
       */
      update_pal_halt_status(0);

      UNLOCK_PFS(flags);

      return 0;

error_conflict:
      DPRINT(("system wide not possible, conflicting session [%d] on CPU%d\n",
            task_pid_nr(pfm_sessions.pfs_sys_session[cpu]),
            cpu));
abort:
      UNLOCK_PFS(flags);

      return -EBUSY;

}

static int
pfm_unreserve_session(pfm_context_t *ctx, int is_syswide, unsigned int cpu)
{
      unsigned long flags;
      /*
       * validity checks on cpu_mask have been done upstream
       */
      LOCK_PFS(flags);

      DPRINT(("in sys_sessions=%u task_sessions=%u dbregs=%u syswide=%d cpu=%u\n",
            pfm_sessions.pfs_sys_sessions,
            pfm_sessions.pfs_task_sessions,
            pfm_sessions.pfs_sys_use_dbregs,
            is_syswide,
            cpu));


      if (is_syswide) {
            pfm_sessions.pfs_sys_session[cpu] = NULL;
            /*
             * would not work with perfmon+more than one bit in cpu_mask
             */
            if (ctx && ctx->ctx_fl_using_dbreg) {
                  if (pfm_sessions.pfs_sys_use_dbregs == 0) {
                        printk(KERN_ERR "perfmon: invalid release for ctx %p sys_use_dbregs=0\n", ctx);
                  } else {
                        pfm_sessions.pfs_sys_use_dbregs--;
                  }
            }
            pfm_sessions.pfs_sys_sessions--;
      } else {
            pfm_sessions.pfs_task_sessions--;
      }
      DPRINT(("out sys_sessions=%u task_sessions=%u dbregs=%u syswide=%d cpu=%u\n",
            pfm_sessions.pfs_sys_sessions,
            pfm_sessions.pfs_task_sessions,
            pfm_sessions.pfs_sys_use_dbregs,
            is_syswide,
            cpu));

      /*
       * if possible, enable default_idle() to go into PAL_HALT
       */
      if (pfm_sessions.pfs_task_sessions == 0 && pfm_sessions.pfs_sys_sessions == 0)
            update_pal_halt_status(1);

      UNLOCK_PFS(flags);

      return 0;
}

/*
 * removes virtual mapping of the sampling buffer.
 * IMPORTANT: cannot be called with interrupts disable, e.g. inside
 * a PROTECT_CTX() section.
 */
static int
pfm_remove_smpl_mapping(struct task_struct *task, void *vaddr, unsigned long size)
{
      int r;

      /* sanity checks */
      if (task->mm == NULL || size == 0UL || vaddr == NULL) {
            printk(KERN_ERR "perfmon: pfm_remove_smpl_mapping [%d] invalid context mm=%p\n", task_pid_nr(task), task->mm);
            return -EINVAL;
      }

      DPRINT(("smpl_vaddr=%p size=%lu\n", vaddr, size));

      /*
       * does the actual unmapping
       */
      down_write(&task->mm->mmap_sem);

      DPRINT(("down_write done smpl_vaddr=%p size=%lu\n", vaddr, size));

      r = pfm_do_munmap(task->mm, (unsigned long)vaddr, size, 0);

      up_write(&task->mm->mmap_sem);
      if (r !=0) {
            printk(KERN_ERR "perfmon: [%d] unable to unmap sampling buffer @%p size=%lu\n", task_pid_nr(task), vaddr, size);
      }

      DPRINT(("do_unmap(%p, %lu)=%d\n", vaddr, size, r));

      return 0;
}

/*
 * free actual physical storage used by sampling buffer
 */
#if 0
static int
pfm_free_smpl_buffer(pfm_context_t *ctx)
{
      pfm_buffer_fmt_t *fmt;

      if (ctx->ctx_smpl_hdr == NULL) goto invalid_free;

      /*
       * we won't use the buffer format anymore
       */
      fmt = ctx->ctx_buf_fmt;

      DPRINT(("sampling buffer @%p size %lu vaddr=%p\n",
            ctx->ctx_smpl_hdr,
            ctx->ctx_smpl_size,
            ctx->ctx_smpl_vaddr));

      pfm_buf_fmt_exit(fmt, current, NULL, NULL);

      /*
       * free the buffer
       */
      pfm_rvfree(ctx->ctx_smpl_hdr, ctx->ctx_smpl_size);

      ctx->ctx_smpl_hdr  = NULL;
      ctx->ctx_smpl_size = 0UL;

      return 0;

invalid_free:
      printk(KERN_ERR "perfmon: pfm_free_smpl_buffer [%d] no buffer\n", task_pid_nr(current));
      return -EINVAL;
}
#endif

static inline void
pfm_exit_smpl_buffer(pfm_buffer_fmt_t *fmt)
{
      if (fmt == NULL) return;

      pfm_buf_fmt_exit(fmt, current, NULL, NULL);

}

/*
 * pfmfs should _never_ be mounted by userland - too much of security hassle,
 * no real gain from having the whole whorehouse mounted. So we don't need
 * any operations on the root directory. However, we need a non-trivial
 * d_name - pfm: will go nicely and kill the special-casing in procfs.
 */
static struct vfsmount *pfmfs_mnt;

static int __init
init_pfm_fs(void)
{
      int err = register_filesystem(&pfm_fs_type);
      if (!err) {
            pfmfs_mnt = kern_mount(&pfm_fs_type);
            err = PTR_ERR(pfmfs_mnt);
            if (IS_ERR(pfmfs_mnt))
                  unregister_filesystem(&pfm_fs_type);
            else
                  err = 0;
      }
      return err;
}

static ssize_t
pfm_read(struct file *filp, char __user *buf, size_t size, loff_t *ppos)
{
      pfm_context_t *ctx;
      pfm_msg_t *msg;
      ssize_t ret;
      unsigned long flags;
      DECLARE_WAITQUEUE(wait, current);
      if (PFM_IS_FILE(filp) == 0) {
            printk(KERN_ERR "perfmon: pfm_poll: bad magic [%d]\n", task_pid_nr(current));
            return -EINVAL;
      }

      ctx = (pfm_context_t *)filp->private_data;
      if (ctx == NULL) {
            printk(KERN_ERR "perfmon: pfm_read: NULL ctx [%d]\n", task_pid_nr(current));
            return -EINVAL;
      }

      /*
       * check even when there is no message
       */
      if (size < sizeof(pfm_msg_t)) {
            DPRINT(("message is too small ctx=%p (>=%ld)\n", ctx, sizeof(pfm_msg_t)));
            return -EINVAL;
      }

      PROTECT_CTX(ctx, flags);

      /*
       * put ourselves on the wait queue
       */
      add_wait_queue(&ctx->ctx_msgq_wait, &wait);


      for(;;) {
            /*
             * check wait queue
             */

            set_current_state(TASK_INTERRUPTIBLE);

            DPRINT(("head=%d tail=%d\n", ctx->ctx_msgq_head, ctx->ctx_msgq_tail));

            ret = 0;
            if(PFM_CTXQ_EMPTY(ctx) == 0) break;

            UNPROTECT_CTX(ctx, flags);

            /*
             * check non-blocking read
             */
                  ret = -EAGAIN;
            if(filp->f_flags & O_NONBLOCK) break;

            /*
             * check pending signals
             */
            if(signal_pending(current)) {
                  ret = -EINTR;
                  break;
            }
                  /*
             * no message, so wait
             */
                  schedule();

            PROTECT_CTX(ctx, flags);
      }
      DPRINT(("[%d] back to running ret=%ld\n", task_pid_nr(current), ret));
      set_current_state(TASK_RUNNING);
      remove_wait_queue(&ctx->ctx_msgq_wait, &wait);

      if (ret < 0) goto abort;

      ret = -EINVAL;
      msg = pfm_get_next_msg(ctx);
      if (msg == NULL) {
            printk(KERN_ERR "perfmon: pfm_read no msg for ctx=%p [%d]\n", ctx, task_pid_nr(current));
            goto abort_locked;
      }

      DPRINT(("fd=%d type=%d\n", msg->pfm_gen_msg.msg_ctx_fd, msg->pfm_gen_msg.msg_type));

      ret = -EFAULT;
      if(copy_to_user(buf, msg, sizeof(pfm_msg_t)) == 0) ret = sizeof(pfm_msg_t);

abort_locked:
      UNPROTECT_CTX(ctx, flags);
abort:
      return ret;
}

static ssize_t
pfm_write(struct file *file, const char __user *ubuf,
                    size_t size, loff_t *ppos)
{
      DPRINT(("pfm_write called\n"));
      return -EINVAL;
}

static unsigned int
pfm_poll(struct file *filp, poll_table * wait)
{
      pfm_context_t *ctx;
      unsigned long flags;
      unsigned int mask = 0;

      if (PFM_IS_FILE(filp) == 0) {
            printk(KERN_ERR "perfmon: pfm_poll: bad magic [%d]\n", task_pid_nr(current));
            return 0;
      }

      ctx = (pfm_context_t *)filp->private_data;
      if (ctx == NULL) {
            printk(KERN_ERR "perfmon: pfm_poll: NULL ctx [%d]\n", task_pid_nr(current));
            return 0;
      }


      DPRINT(("pfm_poll ctx_fd=%d before poll_wait\n", ctx->ctx_fd));

      poll_wait(filp, &ctx->ctx_msgq_wait, wait);

      PROTECT_CTX(ctx, flags);

      if (PFM_CTXQ_EMPTY(ctx) == 0)
            mask =  POLLIN | POLLRDNORM;

      UNPROTECT_CTX(ctx, flags);

      DPRINT(("pfm_poll ctx_fd=%d mask=0x%x\n", ctx->ctx_fd, mask));

      return mask;
}

static int
pfm_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
      DPRINT(("pfm_ioctl called\n"));
      return -EINVAL;
}

/*
 * interrupt cannot be masked when coming here
 */
static inline int
pfm_do_fasync(int fd, struct file *filp, pfm_context_t *ctx, int on)
{
      int ret;

      ret = fasync_helper (fd, filp, on, &ctx->ctx_async_queue);

      DPRINT(("pfm_fasync called by [%d] on ctx_fd=%d on=%d async_queue=%p ret=%d\n",
            task_pid_nr(current),
            fd,
            on,
            ctx->ctx_async_queue, ret));

      return ret;
}

static int
pfm_fasync(int fd, struct file *filp, int on)
{
      pfm_context_t *ctx;
      int ret;

      if (PFM_IS_FILE(filp) == 0) {
            printk(KERN_ERR "perfmon: pfm_fasync bad magic [%d]\n", task_pid_nr(current));
            return -EBADF;
      }

      ctx = (pfm_context_t *)filp->private_data;
      if (ctx == NULL) {
            printk(KERN_ERR "perfmon: pfm_fasync NULL ctx [%d]\n", task_pid_nr(current));
            return -EBADF;
      }
      /*
       * we cannot mask interrupts during this call because this may
       * may go to sleep if memory is not readily avalaible.
       *
       * We are protected from the conetxt disappearing by the get_fd()/put_fd()
       * done in caller. Serialization of this function is ensured by caller.
       */
      ret = pfm_do_fasync(fd, filp, ctx, on);


      DPRINT(("pfm_fasync called on ctx_fd=%d on=%d async_queue=%p ret=%d\n",
            fd,
            on,
            ctx->ctx_async_queue, ret));

      return ret;
}

#ifdef CONFIG_SMP
/*
 * this function is exclusively called from pfm_close().
 * The context is not protected at that time, nor are interrupts
 * on the remote CPU. That's necessary to avoid deadlocks.
 */
static void
pfm_syswide_force_stop(void *info)
{
      pfm_context_t   *ctx = (pfm_context_t *)info;
      struct pt_regs *regs = task_pt_regs(current);
      struct task_struct *owner;
      unsigned long flags;
      int ret;

      if (ctx->ctx_cpu != smp_processor_id()) {
            printk(KERN_ERR "perfmon: pfm_syswide_force_stop for CPU%d  but on CPU%d\n",
                  ctx->ctx_cpu,
                  smp_processor_id());
            return;
      }
      owner = GET_PMU_OWNER();
      if (owner != ctx->ctx_task) {
            printk(KERN_ERR "perfmon: pfm_syswide_force_stop CPU%d unexpected owner [%d] instead of [%d]\n",
                  smp_processor_id(),
                  task_pid_nr(owner), task_pid_nr(ctx->ctx_task));
            return;
      }
      if (GET_PMU_CTX() != ctx) {
            printk(KERN_ERR "perfmon: pfm_syswide_force_stop CPU%d unexpected ctx %p instead of %p\n",
                  smp_processor_id(),
                  GET_PMU_CTX(), ctx);
            return;
      }

      DPRINT(("on CPU%d forcing system wide stop for [%d]\n", smp_processor_id(), task_pid_nr(ctx->ctx_task)));
      /*
       * the context is already protected in pfm_close(), we simply
       * need to mask interrupts to avoid a PMU interrupt race on
       * this CPU
       */
      local_irq_save(flags);

      ret = pfm_context_unload(ctx, NULL, 0, regs);
      if (ret) {
            DPRINT(("context_unload returned %d\n", ret));
      }

      /*
       * unmask interrupts, PMU interrupts are now spurious here
       */
      local_irq_restore(flags);
}

static void
pfm_syswide_cleanup_other_cpu(pfm_context_t *ctx)
{
      int ret;

      DPRINT(("calling CPU%d for cleanup\n", ctx->ctx_cpu));
      ret = smp_call_function_single(ctx->ctx_cpu, pfm_syswide_force_stop, ctx, 0, 1);
      DPRINT(("called CPU%d for cleanup ret=%d\n", ctx->ctx_cpu, ret));
}
#endif /* CONFIG_SMP */

/*
 * called for each close(). Partially free resources.
 * When caller is self-monitoring, the context is unloaded.
 */
static int
pfm_flush(struct file *filp, fl_owner_t id)
{
      pfm_context_t *ctx;
      struct task_struct *task;
      struct pt_regs *regs;
      unsigned long flags;
      unsigned long smpl_buf_size = 0UL;
      void *smpl_buf_vaddr = NULL;
      int state, is_system;

      if (PFM_IS_FILE(filp) == 0) {
            DPRINT(("bad magic for\n"));
            return -EBADF;
      }

      ctx = (pfm_context_t *)filp->private_data;
      if (ctx == NULL) {
            printk(KERN_ERR "perfmon: pfm_flush: NULL ctx [%d]\n", task_pid_nr(current));
            return -EBADF;
      }

      /*
       * remove our file from the async queue, if we use this mode.
       * This can be done without the context being protected. We come
       * here when the context has become unreachable by other tasks.
       *
       * We may still have active monitoring at this point and we may
       * end up in pfm_overflow_handler(). However, fasync_helper()
       * operates with interrupts disabled and it cleans up the
       * queue. If the PMU handler is called prior to entering
       * fasync_helper() then it will send a signal. If it is
       * invoked after, it will find an empty queue and no
       * signal will be sent. In both case, we are safe
       */
      if (filp->f_flags & FASYNC) {
            DPRINT(("cleaning up async_queue=%p\n", ctx->ctx_async_queue));
            pfm_do_fasync (-1, filp, ctx, 0);
      }

      PROTECT_CTX(ctx, flags);

      state     = ctx->ctx_state;
      is_system = ctx->ctx_fl_system;

      task = PFM_CTX_TASK(ctx);
      regs = task_pt_regs(task);

      DPRINT(("ctx_state=%d is_current=%d\n",
            state,
            task == current ? 1 : 0));

      /*
       * if state == UNLOADED, then task is NULL
       */

      /*
       * we must stop and unload because we are losing access to the context.
       */
      if (task == current) {
#ifdef CONFIG_SMP
            /*
             * the task IS the owner but it migrated to another CPU: that's bad
             * but we must handle this cleanly. Unfortunately, the kernel does
             * not provide a mechanism to block migration (while the context is loaded).
             *
             * We need to release the resource on the ORIGINAL cpu.
             */
            if (is_system && ctx->ctx_cpu != smp_processor_id()) {

                  DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
                  /*
                   * keep context protected but unmask interrupt for IPI
                   */
                  local_irq_restore(flags);

                  pfm_syswide_cleanup_other_cpu(ctx);

                  /*
                   * restore interrupt masking
                   */
                  local_irq_save(flags);

                  /*
                   * context is unloaded at this point
                   */
            } else
#endif /* CONFIG_SMP */
            {

                  DPRINT(("forcing unload\n"));
                  /*
                  * stop and unload, returning with state UNLOADED
                  * and session unreserved.
                  */
                  pfm_context_unload(ctx, NULL, 0, regs);

                  DPRINT(("ctx_state=%d\n", ctx->ctx_state));
            }
      }

      /*
       * remove virtual mapping, if any, for the calling task.
       * cannot reset ctx field until last user is calling close().
       *
       * ctx_smpl_vaddr must never be cleared because it is needed
       * by every task with access to the context
       *
       * When called from do_exit(), the mm context is gone already, therefore
       * mm is NULL, i.e., the VMA is already gone  and we do not have to
       * do anything here
       */
      if (ctx->ctx_smpl_vaddr && current->mm) {
            smpl_buf_vaddr = ctx->ctx_smpl_vaddr;
            smpl_buf_size  = ctx->ctx_smpl_size;
      }

      UNPROTECT_CTX(ctx, flags);

      /*
       * if there was a mapping, then we systematically remove it
       * at this point. Cannot be done inside critical section
       * because some VM function reenables interrupts.
       *
       */
      if (smpl_buf_vaddr) pfm_remove_smpl_mapping(current, smpl_buf_vaddr, smpl_buf_size);

      return 0;
}
/*
 * called either on explicit close() or from exit_files(). 
 * Only the LAST user of the file gets to this point, i.e., it is
 * called only ONCE.
 *
 * IMPORTANT: we get called ONLY when the refcnt on the file gets to zero 
 * (fput()),i.e, last task to access the file. Nobody else can access the 
 * file at this point.
 *
 * When called from exit_files(), the VMA has been freed because exit_mm()
 * is executed before exit_files().
 *
 * When called from exit_files(), the current task is not yet ZOMBIE but we
 * flush the PMU state to the context. 
 */
static int
pfm_close(struct inode *inode, struct file *filp)
{
      pfm_context_t *ctx;
      struct task_struct *task;
      struct pt_regs *regs;
      DECLARE_WAITQUEUE(wait, current);
      unsigned long flags;
      unsigned long smpl_buf_size = 0UL;
      void *smpl_buf_addr = NULL;
      int free_possible = 1;
      int state, is_system;

      DPRINT(("pfm_close called private=%p\n", filp->private_data));

      if (PFM_IS_FILE(filp) == 0) {
            DPRINT(("bad magic\n"));
            return -EBADF;
      }
      
      ctx = (pfm_context_t *)filp->private_data;
      if (ctx == NULL) {
            printk(KERN_ERR "perfmon: pfm_close: NULL ctx [%d]\n", task_pid_nr(current));
            return -EBADF;
      }

      PROTECT_CTX(ctx, flags);

      state     = ctx->ctx_state;
      is_system = ctx->ctx_fl_system;

      task = PFM_CTX_TASK(ctx);
      regs = task_pt_regs(task);

      DPRINT(("ctx_state=%d is_current=%d\n", 
            state,
            task == current ? 1 : 0));

      /*
       * if task == current, then pfm_flush() unloaded the context
       */
      if (state == PFM_CTX_UNLOADED) goto doit;

      /*
       * context is loaded/masked and task != current, we need to
       * either force an unload or go zombie
       */

      /*
       * The task is currently blocked or will block after an overflow.
       * we must force it to wakeup to get out of the
       * MASKED state and transition to the unloaded state by itself.
       *
       * This situation is only possible for per-task mode
       */
      if (state == PFM_CTX_MASKED && CTX_OVFL_NOBLOCK(ctx) == 0) {

            /*
             * set a "partial" zombie state to be checked
             * upon return from down() in pfm_handle_work().
             *
             * We cannot use the ZOMBIE state, because it is checked
             * by pfm_load_regs() which is called upon wakeup from down().
             * In such case, it would free the context and then we would
             * return to pfm_handle_work() which would access the
             * stale context. Instead, we set a flag invisible to pfm_load_regs()
             * but visible to pfm_handle_work().
             *
             * For some window of time, we have a zombie context with
             * ctx_state = MASKED  and not ZOMBIE
             */
            ctx->ctx_fl_going_zombie = 1;

            /*
             * force task to wake up from MASKED state
             */
            complete(&ctx->ctx_restart_done);

            DPRINT(("waking up ctx_state=%d\n", state));

            /*
             * put ourself to sleep waiting for the other
             * task to report completion
             *
             * the context is protected by mutex, therefore there
             * is no risk of being notified of completion before
             * begin actually on the waitq.
             */
            set_current_state(TASK_INTERRUPTIBLE);
            add_wait_queue(&ctx->ctx_zombieq, &wait);

            UNPROTECT_CTX(ctx, flags);

            /*
             * XXX: check for signals :
             *    - ok for explicit close
             *    - not ok when coming from exit_files()
             */
                  schedule();


            PROTECT_CTX(ctx, flags);


            remove_wait_queue(&ctx->ctx_zombieq, &wait);
            set_current_state(TASK_RUNNING);

            /*
             * context is unloaded at this point
             */
            DPRINT(("after zombie wakeup ctx_state=%d for\n", state));
      }
      else if (task != current) {
#ifdef CONFIG_SMP
            /*
             * switch context to zombie state
             */
            ctx->ctx_state = PFM_CTX_ZOMBIE;

            DPRINT(("zombie ctx for [%d]\n", task_pid_nr(task)));
            /*
             * cannot free the context on the spot. deferred until
             * the task notices the ZOMBIE state
             */
            free_possible = 0;
#else
            pfm_context_unload(ctx, NULL, 0, regs);
#endif
      }

doit:
      /* reload state, may have changed during  opening of critical section */
      state = ctx->ctx_state;

      /*
       * the context is still attached to a task (possibly current)
       * we cannot destroy it right now
       */

      /*
       * we must free the sampling buffer right here because
       * we cannot rely on it being cleaned up later by the
       * monitored task. It is not possible to free vmalloc'ed
       * memory in pfm_load_regs(). Instead, we remove the buffer
       * now. should there be subsequent PMU overflow originally
       * meant for sampling, the will be converted to spurious
       * and that's fine because the monitoring tools is gone anyway.
       */
      if (ctx->ctx_smpl_hdr) {
            smpl_buf_addr = ctx->ctx_smpl_hdr;
            smpl_buf_size = ctx->ctx_smpl_size;
            /* no more sampling */
            ctx->ctx_smpl_hdr = NULL;
            ctx->ctx_fl_is_sampling = 0;
      }

      DPRINT(("ctx_state=%d free_possible=%d addr=%p size=%lu\n",
            state,
            free_possible,
            smpl_buf_addr,
            smpl_buf_size));

      if (smpl_buf_addr) pfm_exit_smpl_buffer(ctx->ctx_buf_fmt);

      /*
       * UNLOADED that the session has already been unreserved.
       */
      if (state == PFM_CTX_ZOMBIE) {
            pfm_unreserve_session(ctx, ctx->ctx_fl_system , ctx->ctx_cpu);
      }

      /*
       * disconnect file descriptor from context must be done
       * before we unlock.
       */
      filp->private_data = NULL;

      /*
       * if we free on the spot, the context is now completely unreachable
       * from the callers side. The monitored task side is also cut, so we
       * can freely cut.
       *
       * If we have a deferred free, only the caller side is disconnected.
       */
      UNPROTECT_CTX(ctx, flags);

      /*
       * All memory free operations (especially for vmalloc'ed memory)
       * MUST be done with interrupts ENABLED.
       */
      if (smpl_buf_addr)  pfm_rvfree(smpl_buf_addr, smpl_buf_size);

      /*
       * return the memory used by the context
       */
      if (free_possible) pfm_context_free(ctx);

      return 0;
}

static int
pfm_no_open(struct inode *irrelevant, struct file *dontcare)
{
      DPRINT(("pfm_no_open called\n"));
      return -ENXIO;
}



static const struct file_operations pfm_file_ops = {
      .llseek   = no_llseek,
      .read     = pfm_read,
      .write    = pfm_write,
      .poll     = pfm_poll,
      .ioctl    = pfm_ioctl,
      .open     = pfm_no_open,      /* special open code to disallow open via /proc */
      .fasync   = pfm_fasync,
      .release  = pfm_close,
      .flush        = pfm_flush
};

static int
pfmfs_delete_dentry(struct dentry *dentry)
{
      return 1;
}

static struct dentry_operations pfmfs_dentry_operations = {
      .d_delete = pfmfs_delete_dentry,
};


static int
pfm_alloc_fd(struct file **cfile)
{
      int fd, ret = 0;
      struct file *file = NULL;
      struct inode * inode;
      char name[32];
      struct qstr this;

      fd = get_unused_fd();
      if (fd < 0) return -ENFILE;

      ret = -ENFILE;

      file = get_empty_filp();
      if (!file) goto out;

      /*
       * allocate a new inode
       */
      inode = new_inode(pfmfs_mnt->mnt_sb);
      if (!inode) goto out;

      DPRINT(("new inode ino=%ld @%p\n", inode->i_ino, inode));

      inode->i_mode = S_IFCHR|S_IRUGO;
      inode->i_uid  = current->fsuid;
      inode->i_gid  = current->fsgid;

      sprintf(name, "[%lu]", inode->i_ino);
      this.name = name;
      this.len  = strlen(name);
      this.hash = inode->i_ino;

      ret = -ENOMEM;

      /*
       * allocate a new dcache entry
       */
      file->f_path.dentry = d_alloc(pfmfs_mnt->mnt_sb->s_root, &this);
      if (!file->f_path.dentry) goto out;

      file->f_path.dentry->d_op = &pfmfs_dentry_operations;

      d_add(file->f_path.dentry, inode);
      file->f_path.mnt = mntget(pfmfs_mnt);
      file->f_mapping = inode->i_mapping;

      file->f_op    = &pfm_file_ops;
      file->f_mode  = FMODE_READ;
      file->f_flags = O_RDONLY;
      file->f_pos   = 0;

      /*
       * may have to delay until context is attached?
       */
      fd_install(fd, file);

      /*
       * the file structure we will use
       */
      *cfile = file;

      return fd;
out:
      if (file) put_filp(file);
      put_unused_fd(fd);
      return ret;
}

static void
pfm_free_fd(int fd, struct file *file)
{
      struct files_struct *files = current->files;
      struct fdtable *fdt;

      /* 
       * there ie no fd_uninstall(), so we do it here
       */
      spin_lock(&files->file_lock);
      fdt = files_fdtable(files);
      rcu_assign_pointer(fdt->fd[fd], NULL);
      spin_unlock(&files->file_lock);

      if (file)
            put_filp(file);
      put_unused_fd(fd);
}

static int
pfm_remap_buffer(struct vm_area_struct *vma, unsigned long buf, unsigned long addr, unsigned long size)
{
      DPRINT(("CPU%d buf=0x%lx addr=0x%lx size=%ld\n", smp_processor_id(), buf, addr, size));

      while (size > 0) {
            unsigned long pfn = ia64_tpa(buf) >> PAGE_SHIFT;


            if (remap_pfn_range(vma, addr, pfn, PAGE_SIZE, PAGE_READONLY))
                  return -ENOMEM;

            addr  += PAGE_SIZE;
            buf   += PAGE_SIZE;
            size  -= PAGE_SIZE;
      }
      return 0;
}

/*
 * allocate a sampling buffer and remaps it into the user address space of the task
 */
static int
pfm_smpl_buffer_alloc(struct task_struct *task, struct file *filp, pfm_context_t *ctx, unsigned long rsize, void **user_vaddr)
{
      struct mm_struct *mm = task->mm;
      struct vm_area_struct *vma = NULL;
      unsigned long size;
      void *smpl_buf;


      /*
       * the fixed header + requested size and align to page boundary
       */
      size = PAGE_ALIGN(rsize);

      DPRINT(("sampling buffer rsize=%lu size=%lu bytes\n", rsize, size));

      /*
       * check requested size to avoid Denial-of-service attacks
       * XXX: may have to refine this test
       * Check against address space limit.
       *
       * if ((mm->total_vm << PAGE_SHIFT) + len> task->rlim[RLIMIT_AS].rlim_cur)
       *    return -ENOMEM;
       */
      if (size > task->signal->rlim[RLIMIT_MEMLOCK].rlim_cur)
            return -ENOMEM;

      /*
       * We do the easy to undo allocations first.
       *
       * pfm_rvmalloc(), clears the buffer, so there is no leak
       */
      smpl_buf = pfm_rvmalloc(size);
      if (smpl_buf == NULL) {
            DPRINT(("Can't allocate sampling buffer\n"));
            return -ENOMEM;
      }

      DPRINT(("smpl_buf @%p\n", smpl_buf));

      /* allocate vma */
      vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
      if (!vma) {
            DPRINT(("Cannot allocate vma\n"));
            goto error_kmem;
      }

      /*
       * partially initialize the vma for the sampling buffer
       */
      vma->vm_mm       = mm;
      vma->vm_file           = filp;
      vma->vm_flags          = VM_READ| VM_MAYREAD |VM_RESERVED;
      vma->vm_page_prot    = PAGE_READONLY; /* XXX may need to change */

      /*
       * Now we have everything we need and we can initialize
       * and connect all the data structures
       */

      ctx->ctx_smpl_hdr   = smpl_buf;
      ctx->ctx_smpl_size  = size; /* aligned size */

      /*
       * Let's do the difficult operations next.
       *
       * now we atomically find some area in the address space and
       * remap the buffer in it.
       */
      down_write(&task->mm->mmap_sem);

      /* find some free area in address space, must have mmap sem held */
      vma->vm_start = pfm_get_unmapped_area(NULL, 0, size, 0, MAP_PRIVATE|MAP_ANONYMOUS, 0);
      if (vma->vm_start == 0UL) {
            DPRINT(("Cannot find unmapped area for size %ld\n", size));
            up_write(&task->mm->mmap_sem);
            goto error;
      }
      vma->vm_end = vma->vm_start + size;
      vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;

      DPRINT(("aligned size=%ld, hdr=%p mapped @0x%lx\n", size, ctx->ctx_smpl_hdr, vma->vm_start));

      /* can only be applied to current task, need to have the mm semaphore held when called */
      if (pfm_remap_buffer(vma, (unsigned long)smpl_buf, vma->vm_start, size)) {
            DPRINT(("Can't remap buffer\n"));
            up_write(&task->mm->mmap_sem);
            goto error;
      }

      get_file(filp);

      /*
       * now insert the vma in the vm list for the process, must be
       * done with mmap lock held
       */
      insert_vm_struct(mm, vma);

      mm->total_vm  += size >> PAGE_SHIFT;
      vm_stat_account(vma->vm_mm, vma->vm_flags, vma->vm_file,
                                          vma_pages(vma));
      up_write(&task->mm->mmap_sem);

      /*
       * keep track of user level virtual address
       */
      ctx->ctx_smpl_vaddr = (void *)vma->vm_start;
      *(unsigned long *)user_vaddr = vma->vm_start;

      return 0;

error:
      kmem_cache_free(vm_area_cachep, vma);
error_kmem:
      pfm_rvfree(smpl_buf, size);

      return -ENOMEM;
}

/*
 * XXX: do something better here
 */
static int
pfm_bad_permissions(struct task_struct *task)
{
      /* inspired by ptrace_attach() */
      DPRINT(("cur: uid=%d gid=%d task: euid=%d suid=%d uid=%d egid=%d sgid=%d\n",
            current->uid,
            current->gid,
            task->euid,
            task->suid,
            task->uid,
            task->egid,
            task->sgid));

      return ((current->uid != task->euid)
          || (current->uid != task->suid)
          || (current->uid != task->uid)
          || (current->gid != task->egid)
          || (current->gid != task->sgid)
          || (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE);
}

static int
pfarg_is_sane(struct task_struct *task, pfarg_context_t *pfx)
{
      int ctx_flags;

      /* valid signal */

      ctx_flags = pfx->ctx_flags;

      if (ctx_flags & PFM_FL_SYSTEM_WIDE) {

            /*
             * cannot block in this mode
             */
            if (ctx_flags & PFM_FL_NOTIFY_BLOCK) {
                  DPRINT(("cannot use blocking mode when in system wide monitoring\n"));
                  return -EINVAL;
            }
      } else {
      }
      /* probably more to add here */

      return 0;
}

static int
pfm_setup_buffer_fmt(struct task_struct *task, struct file *filp, pfm_context_t *ctx, unsigned int ctx_flags,
                 unsigned int cpu, pfarg_context_t *arg)
{
      pfm_buffer_fmt_t *fmt = NULL;
      unsigned long size = 0UL;
      void *uaddr = NULL;
      void *fmt_arg = NULL;
      int ret = 0;
#define PFM_CTXARG_BUF_ARG(a) (pfm_buffer_fmt_t *)(a+1)

      /* invoke and lock buffer format, if found */
      fmt = pfm_find_buffer_fmt(arg->ctx_smpl_buf_id);
      if (fmt == NULL) {
            DPRINT(("[%d] cannot find buffer format\n", task_pid_nr(task)));
            return -EINVAL;
      }

      /*
       * buffer argument MUST be contiguous to pfarg_context_t
       */
      if (fmt->fmt_arg_size) fmt_arg = PFM_CTXARG_BUF_ARG(arg);

      ret = pfm_buf_fmt_validate(fmt, task, ctx_flags, cpu, fmt_arg);

      DPRINT(("[%d] after validate(0x%x,%d,%p)=%d\n", task_pid_nr(task), ctx_flags, cpu, fmt_arg, ret));

      if (ret) goto error;

      /* link buffer format and context */
      ctx->ctx_buf_fmt = fmt;

      /*
       * check if buffer format wants to use perfmon buffer allocation/mapping service
       */
      ret = pfm_buf_fmt_getsize(fmt, task, ctx_flags, cpu, fmt_arg, &size);
      if (ret) goto error;

      if (size) {
            /*
             * buffer is always remapped into the caller's address space
             */
            ret = pfm_smpl_buffer_alloc(current, filp, ctx, size, &uaddr);
            if (ret) goto error;

            /* keep track of user address of buffer */
            arg->ctx_smpl_vaddr = uaddr;
      }
      ret = pfm_buf_fmt_init(fmt, task, ctx->ctx_smpl_hdr, ctx_flags, cpu, fmt_arg);

error:
      return ret;
}

static void
pfm_reset_pmu_state(pfm_context_t *ctx)
{
      int i;

      /*
       * install reset values for PMC.
       */
      for (i=1; PMC_IS_LAST(i) == 0; i++) {
            if (PMC_IS_IMPL(i) == 0) continue;
            ctx->ctx_pmcs[i] = PMC_DFL_VAL(i);
            DPRINT(("pmc[%d]=0x%lx\n", i, ctx->ctx_pmcs[i]));
      }
      /*
       * PMD registers are set to 0UL when the context in memset()
       */

      /*
       * On context switched restore, we must restore ALL pmc and ALL pmd even
       * when they are not actively used by the task. In UP, the incoming process
       * may otherwise pick up left over PMC, PMD state from the previous process.
       * As opposed to PMD, stale PMC can cause harm to the incoming
       * process because they may change what is being measured.
       * Therefore, we must systematically reinstall the entire
       * PMC state. In SMP, the same thing is possible on the
       * same CPU but also on between 2 CPUs.
       *
       * The problem with PMD is information leaking especially
       * to user level when psr.sp=0
       *
       * There is unfortunately no easy way to avoid this problem
       * on either UP or SMP. This definitively slows down the
       * pfm_load_regs() function.
       */

       /*
        * bitmask of all PMCs accessible to this context
        *
        * PMC0 is treated differently.
        */
      ctx->ctx_all_pmcs[0] = pmu_conf->impl_pmcs[0] & ~0x1;

      /*
       * bitmask of all PMDs that are accessible to this context
       */
      ctx->ctx_all_pmds[0] = pmu_conf->impl_pmds[0];

      DPRINT(("<%d> all_pmcs=0x%lx all_pmds=0x%lx\n", ctx->ctx_fd, ctx->ctx_all_pmcs[0],ctx->ctx_all_pmds[0]));

      /*
       * useful in case of re-enable after disable
       */
      ctx->ctx_used_ibrs[0] = 0UL;
      ctx->ctx_used_dbrs[0] = 0UL;
}

static int
pfm_ctx_getsize(void *arg, size_t *sz)
{
      pfarg_context_t *req = (pfarg_context_t *)arg;
      pfm_buffer_fmt_t *fmt;

      *sz = 0;

      if (!pfm_uuid_cmp(req->ctx_smpl_buf_id, pfm_null_uuid)) return 0;

      fmt = pfm_find_buffer_fmt(req->ctx_smpl_buf_id);
      if (fmt == NULL) {
            DPRINT(("cannot find buffer format\n"));
            return -EINVAL;
      }
      /* get just enough to copy in user parameters */
      *sz = fmt->fmt_arg_size;
      DPRINT(("arg_size=%lu\n", *sz));

      return 0;
}



/*
 * cannot attach if :
 *    - kernel task
 *    - task not owned by caller
 *    - task incompatible with context mode
 */
static int
pfm_task_incompatible(pfm_context_t *ctx, struct task_struct *task)
{
      /*
       * no kernel task or task not owner by caller
       */
      if (task->mm == NULL) {
            DPRINT(("task [%d] has not memory context (kernel thread)\n", task_pid_nr(task)));
            return -EPERM;
      }
      if (pfm_bad_permissions(task)) {
            DPRINT(("no permission to attach to  [%d]\n", task_pid_nr(task)));
            return -EPERM;
      }
      /*
       * cannot block in self-monitoring mode
       */
      if (CTX_OVFL_NOBLOCK(ctx) == 0 && task == current) {
            DPRINT(("cannot load a blocking context on self for [%d]\n", task_pid_nr(task)));
            return -EINVAL;
      }

      if (task->exit_state == EXIT_ZOMBIE) {
            DPRINT(("cannot attach to  zombie task [%d]\n", task_pid_nr(task)));
            return -EBUSY;
      }

      /*
       * always ok for self
       */
      if (task == current) return 0;

      if ((task->state != TASK_STOPPED) && (task->state != TASK_TRACED)) {
            DPRINT(("cannot attach to non-stopped task [%d] state=%ld\n", task_pid_nr(task), task->state));
            return -EBUSY;
      }
      /*
       * make sure the task is off any CPU
       */
      wait_task_inactive(task);

      /* more to come... */

      return 0;
}

static int
pfm_get_task(pfm_context_t *ctx, pid_t pid, struct task_struct **task)
{
      struct task_struct *p = current;
      int ret;

      /* XXX: need to add more checks here */
      if (pid < 2) return -EPERM;

      if (pid != current->pid) {

            read_lock(&tasklist_lock);

            p = find_task_by_pid(pid);

            /* make sure task cannot go away while we operate on it */
            if (p) get_task_struct(p);

            read_unlock(&tasklist_lock);

            if (p == NULL) return -ESRCH;
      }

      ret = pfm_task_incompatible(ctx, p);
      if (ret == 0) {
            *task = p;
      } else if (p != current) {
            pfm_put_task(p);
      }
      return ret;
}



static int
pfm_context_create(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      pfarg_context_t *req = (pfarg_context_t *)arg;
      struct file *filp;
      int ctx_flags;
      int ret;

      /* let's check the arguments first */
      ret = pfarg_is_sane(current, req);
      if (ret < 0) return ret;

      ctx_flags = req->ctx_flags;

      ret = -ENOMEM;

      ctx = pfm_context_alloc();
      if (!ctx) goto error;

      ret = pfm_alloc_fd(&filp);
      if (ret < 0) goto error_file;

      req->ctx_fd = ctx->ctx_fd = ret;

      /*
       * attach context to file
       */
      filp->private_data = ctx;

      /*
       * does the user want to sample?
       */
      if (pfm_uuid_cmp(req->ctx_smpl_buf_id, pfm_null_uuid)) {
            ret = pfm_setup_buffer_fmt(current, filp, ctx, ctx_flags, 0, req);
            if (ret) goto buffer_error;
      }

      /*
       * init context protection lock
       */
      spin_lock_init(&ctx->ctx_lock);

      /*
       * context is unloaded
       */
      ctx->ctx_state = PFM_CTX_UNLOADED;

      /*
       * initialization of context's flags
       */
      ctx->ctx_fl_block       = (ctx_flags & PFM_FL_NOTIFY_BLOCK) ? 1 : 0;
      ctx->ctx_fl_system      = (ctx_flags & PFM_FL_SYSTEM_WIDE) ? 1: 0;
      ctx->ctx_fl_is_sampling = ctx->ctx_buf_fmt ? 1 : 0; /* assume record() is defined */
      ctx->ctx_fl_no_msg      = (ctx_flags & PFM_FL_OVFL_NO_MSG) ? 1: 0;
      /*
       * will move to set properties
       * ctx->ctx_fl_excl_idle   = (ctx_flags & PFM_FL_EXCL_IDLE) ? 1: 0;
       */

      /*
       * init restart semaphore to locked
       */
      init_completion(&ctx->ctx_restart_done);

      /*
       * activation is used in SMP only
       */
      ctx->ctx_last_activation = PFM_INVALID_ACTIVATION;
      SET_LAST_CPU(ctx, -1);

      /*
       * initialize notification message queue
       */
      ctx->ctx_msgq_head = ctx->ctx_msgq_tail = 0;
      init_waitqueue_head(&ctx->ctx_msgq_wait);
      init_waitqueue_head(&ctx->ctx_zombieq);

      DPRINT(("ctx=%p flags=0x%x system=%d notify_block=%d excl_idle=%d no_msg=%d ctx_fd=%d \n",
            ctx,
            ctx_flags,
            ctx->ctx_fl_system,
            ctx->ctx_fl_block,
            ctx->ctx_fl_excl_idle,
            ctx->ctx_fl_no_msg,
            ctx->ctx_fd));

      /*
       * initialize soft PMU state
       */
      pfm_reset_pmu_state(ctx);

      return 0;

buffer_error:
      pfm_free_fd(ctx->ctx_fd, filp);

      if (ctx->ctx_buf_fmt) {
            pfm_buf_fmt_exit(ctx->ctx_buf_fmt, current, NULL, regs);
      }
error_file:
      pfm_context_free(ctx);

error:
      return ret;
}

static inline unsigned long
pfm_new_counter_value (pfm_counter_t *reg, int is_long_reset)
{
      unsigned long val = is_long_reset ? reg->long_reset : reg->short_reset;
      unsigned long new_seed, old_seed = reg->seed, mask = reg->mask;
      extern unsigned long carta_random32 (unsigned long seed);

      if (reg->flags & PFM_REGFL_RANDOM) {
            new_seed = carta_random32(old_seed);
            val -= (old_seed & mask);     /* counter values are negative numbers! */
            if ((mask >> 32) != 0)
                  /* construct a full 64-bit random value: */
                  new_seed |= carta_random32(old_seed >> 32) << 32;
            reg->seed = new_seed;
      }
      reg->lval = val;
      return val;
}

static void
pfm_reset_regs_masked(pfm_context_t *ctx, unsigned long *ovfl_regs, int is_long_reset)
{
      unsigned long mask = ovfl_regs[0];
      unsigned long reset_others = 0UL;
      unsigned long val;
      int i;

      /*
       * now restore reset value on sampling overflowed counters
       */
      mask >>= PMU_FIRST_COUNTER;
      for(i = PMU_FIRST_COUNTER; mask; i++, mask >>= 1) {

            if ((mask & 0x1UL) == 0UL) continue;

            ctx->ctx_pmds[i].val = val = pfm_new_counter_value(ctx->ctx_pmds+ i, is_long_reset);
            reset_others        |= ctx->ctx_pmds[i].reset_pmds[0];

            DPRINT_ovfl((" %s reset ctx_pmds[%d]=%lx\n", is_long_reset ? "long" : "short", i, val));
      }

      /*
       * Now take care of resetting the other registers
       */
      for(i = 0; reset_others; i++, reset_others >>= 1) {

            if ((reset_others & 0x1) == 0) continue;

            ctx->ctx_pmds[i].val = val = pfm_new_counter_value(ctx->ctx_pmds + i, is_long_reset);

            DPRINT_ovfl(("%s reset_others pmd[%d]=%lx\n",
                    is_long_reset ? "long" : "short", i, val));
      }
}

static void
pfm_reset_regs(pfm_context_t *ctx, unsigned long *ovfl_regs, int is_long_reset)
{
      unsigned long mask = ovfl_regs[0];
      unsigned long reset_others = 0UL;
      unsigned long val;
      int i;

      DPRINT_ovfl(("ovfl_regs=0x%lx is_long_reset=%d\n", ovfl_regs[0], is_long_reset));

      if (ctx->ctx_state == PFM_CTX_MASKED) {
            pfm_reset_regs_masked(ctx, ovfl_regs, is_long_reset);
            return;
      }

      /*
       * now restore reset value on sampling overflowed counters
       */
      mask >>= PMU_FIRST_COUNTER;
      for(i = PMU_FIRST_COUNTER; mask; i++, mask >>= 1) {

            if ((mask & 0x1UL) == 0UL) continue;

            val           = pfm_new_counter_value(ctx->ctx_pmds+ i, is_long_reset);
            reset_others |= ctx->ctx_pmds[i].reset_pmds[0];

            DPRINT_ovfl((" %s reset ctx_pmds[%d]=%lx\n", is_long_reset ? "long" : "short", i, val));

            pfm_write_soft_counter(ctx, i, val);
      }

      /*
       * Now take care of resetting the other registers
       */
      for(i = 0; reset_others; i++, reset_others >>= 1) {

            if ((reset_others & 0x1) == 0) continue;

            val = pfm_new_counter_value(ctx->ctx_pmds + i, is_long_reset);

            if (PMD_IS_COUNTING(i)) {
                  pfm_write_soft_counter(ctx, i, val);
            } else {
                  ia64_set_pmd(i, val);
            }
            DPRINT_ovfl(("%s reset_others pmd[%d]=%lx\n",
                    is_long_reset ? "long" : "short", i, val));
      }
      ia64_srlz_d();
}

static int
pfm_write_pmcs(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      struct task_struct *task;
      pfarg_reg_t *req = (pfarg_reg_t *)arg;
      unsigned long value, pmc_pm;
      unsigned long smpl_pmds, reset_pmds, impl_pmds;
      unsigned int cnum, reg_flags, flags, pmc_type;
      int i, can_access_pmu = 0, is_loaded, is_system, expert_mode;
      int is_monitor, is_counting, state;
      int ret = -EINVAL;
      pfm_reg_check_t   wr_func;
#define PFM_CHECK_PMC_PM(x, y, z) ((x)->ctx_fl_system ^ PMC_PM(y, z))

      state     = ctx->ctx_state;
      is_loaded = state == PFM_CTX_LOADED ? 1 : 0;
      is_system = ctx->ctx_fl_system;
      task      = ctx->ctx_task;
      impl_pmds = pmu_conf->impl_pmds[0];

      if (state == PFM_CTX_ZOMBIE) return -EINVAL;

      if (is_loaded) {
            /*
             * In system wide and when the context is loaded, access can only happen
             * when the caller is running on the CPU being monitored by the session.
             * It does not have to be the owner (ctx_task) of the context per se.
             */
            if (is_system && ctx->ctx_cpu != smp_processor_id()) {
                  DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
                  return -EBUSY;
            }
            can_access_pmu = GET_PMU_OWNER() == task || is_system ? 1 : 0;
      }
      expert_mode = pfm_sysctl.expert_mode; 

      for (i = 0; i < count; i++, req++) {

            cnum       = req->reg_num;
            reg_flags  = req->reg_flags;
            value      = req->reg_value;
            smpl_pmds  = req->reg_smpl_pmds[0];
            reset_pmds = req->reg_reset_pmds[0];
            flags      = 0;


            if (cnum >= PMU_MAX_PMCS) {
                  DPRINT(("pmc%u is invalid\n", cnum));
                  goto error;
            }

            pmc_type   = pmu_conf->pmc_desc[cnum].type;
            pmc_pm     = (value >> pmu_conf->pmc_desc[cnum].pm_pos) & 0x1;
            is_counting = (pmc_type & PFM_REG_COUNTING) == PFM_REG_COUNTING ? 1 : 0;
            is_monitor  = (pmc_type & PFM_REG_MONITOR) == PFM_REG_MONITOR ? 1 : 0;

            /*
             * we reject all non implemented PMC as well
             * as attempts to modify PMC[0-3] which are used
             * as status registers by the PMU
             */
            if ((pmc_type & PFM_REG_IMPL) == 0 || (pmc_type & PFM_REG_CONTROL) == PFM_REG_CONTROL) {
                  DPRINT(("pmc%u is unimplemented or no-access pmc_type=%x\n", cnum, pmc_type));
                  goto error;
            }
            wr_func = pmu_conf->pmc_desc[cnum].write_check;
            /*
             * If the PMC is a monitor, then if the value is not the default:
             *    - system-wide session: PMCx.pm=1 (privileged monitor)
             *    - per-task           : PMCx.pm=0 (user monitor)
             */
            if (is_monitor && value != PMC_DFL_VAL(cnum) && is_system ^ pmc_pm) {
                  DPRINT(("pmc%u pmc_pm=%lu is_system=%d\n",
                        cnum,
                        pmc_pm,
                        is_system));
                  goto error;
            }

            if (is_counting) {
                  /*
                   * enforce generation of overflow interrupt. Necessary on all
                   * CPUs.
                   */
                  value |= 1 << PMU_PMC_OI;

                  if (reg_flags & PFM_REGFL_OVFL_NOTIFY) {
                        flags |= PFM_REGFL_OVFL_NOTIFY;
                  }

                  if (reg_flags & PFM_REGFL_RANDOM) flags |= PFM_REGFL_RANDOM;

                  /* verify validity of smpl_pmds */
                  if ((smpl_pmds & impl_pmds) != smpl_pmds) {
                        DPRINT(("invalid smpl_pmds 0x%lx for pmc%u\n", smpl_pmds, cnum));
                        goto error;
                  }

                  /* verify validity of reset_pmds */
                  if ((reset_pmds & impl_pmds) != reset_pmds) {
                        DPRINT(("invalid reset_pmds 0x%lx for pmc%u\n", reset_pmds, cnum));
                        goto error;
                  }
            } else {
                  if (reg_flags & (PFM_REGFL_OVFL_NOTIFY|PFM_REGFL_RANDOM)) {
                        DPRINT(("cannot set ovfl_notify or random on pmc%u\n", cnum));
                        goto error;
                  }
                  /* eventid on non-counting monitors are ignored */
            }

            /*
             * execute write checker, if any
             */
            if (likely(expert_mode == 0 && wr_func)) {
                  ret = (*wr_func)(task, ctx, cnum, &value, regs);
                  if (ret) goto error;
                  ret = -EINVAL;
            }

            /*
             * no error on this register
             */
            PFM_REG_RETFLAG_SET(req->reg_flags, 0);

            /*
             * Now we commit the changes to the software state
             */

            /*
             * update overflow information
             */
            if (is_counting) {
                  /*
                   * full flag update each time a register is programmed
                   */
                  ctx->ctx_pmds[cnum].flags = flags;

                  ctx->ctx_pmds[cnum].reset_pmds[0] = reset_pmds;
                  ctx->ctx_pmds[cnum].smpl_pmds[0]  = smpl_pmds;
                  ctx->ctx_pmds[cnum].eventid       = req->reg_smpl_eventid;

                  /*
                   * Mark all PMDS to be accessed as used.
                   *
                   * We do not keep track of PMC because we have to
                   * systematically restore ALL of them.
                   *
                   * We do not update the used_monitors mask, because
                   * if we have not programmed them, then will be in
                   * a quiescent state, therefore we will not need to
                   * mask/restore then when context is MASKED.
                   */
                  CTX_USED_PMD(ctx, reset_pmds);
                  CTX_USED_PMD(ctx, smpl_pmds);
                  /*
                   * make sure we do not try to reset on
                   * restart because we have established new values
                   */
                  if (state == PFM_CTX_MASKED) ctx->ctx_ovfl_regs[0] &= ~1UL << cnum;
            }
            /*
             * Needed in case the user does not initialize the equivalent
             * PMD. Clearing is done indirectly via pfm_reset_pmu_state() so there is no
             * possible leak here.
             */
            CTX_USED_PMD(ctx, pmu_conf->pmc_desc[cnum].dep_pmd[0]);

            /*
             * keep track of the monitor PMC that we are using.
             * we save the value of the pmc in ctx_pmcs[] and if
             * the monitoring is not stopped for the context we also
             * place it in the saved state area so that it will be
             * picked up later by the context switch code.
             *
             * The value in ctx_pmcs[] can only be changed in pfm_write_pmcs().
             *
             * The value in th_pmcs[] may be modified on overflow, i.e.,  when
             * monitoring needs to be stopped.
             */
            if (is_monitor) CTX_USED_MONITOR(ctx, 1UL << cnum);

            /*
             * update context state
             */
            ctx->ctx_pmcs[cnum] = value;

            if (is_loaded) {
                  /*
                   * write thread state
                   */
                  if (is_system == 0) ctx->th_pmcs[cnum] = value;

                  /*
                   * write hardware register if we can
                   */
                  if (can_access_pmu) {
                        ia64_set_pmc(cnum, value);
                  }
#ifdef CONFIG_SMP
                  else {
                        /*
                         * per-task SMP only here
                         *
                         * we are guaranteed that the task is not running on the other CPU,
                         * we indicate that this PMD will need to be reloaded if the task
                         * is rescheduled on the CPU it ran last on.
                         */
                        ctx->ctx_reload_pmcs[0] |= 1UL << cnum;
                  }
#endif
            }

            DPRINT(("pmc[%u]=0x%lx ld=%d apmu=%d flags=0x%x all_pmcs=0x%lx used_pmds=0x%lx eventid=%ld smpl_pmds=0x%lx reset_pmds=0x%lx reloads_pmcs=0x%lx used_monitors=0x%lx ovfl_regs=0x%lx\n",
                    cnum,
                    value,
                    is_loaded,
                    can_access_pmu,
                    flags,
                    ctx->ctx_all_pmcs[0],
                    ctx->ctx_used_pmds[0],
                    ctx->ctx_pmds[cnum].eventid,
                    smpl_pmds,
                    reset_pmds,
                    ctx->ctx_reload_pmcs[0],
                    ctx->ctx_used_monitors[0],
                    ctx->ctx_ovfl_regs[0]));
      }

      /*
       * make sure the changes are visible
       */
      if (can_access_pmu) ia64_srlz_d();

      return 0;
error:
      PFM_REG_RETFLAG_SET(req->reg_flags, PFM_REG_RETFL_EINVAL);
      return ret;
}

static int
pfm_write_pmds(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      struct task_struct *task;
      pfarg_reg_t *req = (pfarg_reg_t *)arg;
      unsigned long value, hw_value, ovfl_mask;
      unsigned int cnum;
      int i, can_access_pmu = 0, state;
      int is_counting, is_loaded, is_system, expert_mode;
      int ret = -EINVAL;
      pfm_reg_check_t wr_func;


      state     = ctx->ctx_state;
      is_loaded = state == PFM_CTX_LOADED ? 1 : 0;
      is_system = ctx->ctx_fl_system;
      ovfl_mask = pmu_conf->ovfl_val;
      task      = ctx->ctx_task;

      if (unlikely(state == PFM_CTX_ZOMBIE)) return -EINVAL;

      /*
       * on both UP and SMP, we can only write to the PMC when the task is
       * the owner of the local PMU.
       */
      if (likely(is_loaded)) {
            /*
             * In system wide and when the context is loaded, access can only happen
             * when the caller is running on the CPU being monitored by the session.
             * It does not have to be the owner (ctx_task) of the context per se.
             */
            if (unlikely(is_system && ctx->ctx_cpu != smp_processor_id())) {
                  DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
                  return -EBUSY;
            }
            can_access_pmu = GET_PMU_OWNER() == task || is_system ? 1 : 0;
      }
      expert_mode = pfm_sysctl.expert_mode; 

      for (i = 0; i < count; i++, req++) {

            cnum  = req->reg_num;
            value = req->reg_value;

            if (!PMD_IS_IMPL(cnum)) {
                  DPRINT(("pmd[%u] is unimplemented or invalid\n", cnum));
                  goto abort_mission;
            }
            is_counting = PMD_IS_COUNTING(cnum);
            wr_func     = pmu_conf->pmd_desc[cnum].write_check;

            /*
             * execute write checker, if any
             */
            if (unlikely(expert_mode == 0 && wr_func)) {
                  unsigned long v = value;

                  ret = (*wr_func)(task, ctx, cnum, &v, regs);
                  if (ret) goto abort_mission;

                  value = v;
                  ret   = -EINVAL;
            }

            /*
             * no error on this register
             */
            PFM_REG_RETFLAG_SET(req->reg_flags, 0);

            /*
             * now commit changes to software state
             */
            hw_value = value;

            /*
             * update virtualized (64bits) counter
             */
            if (is_counting) {
                  /*
                   * write context state
                   */
                  ctx->ctx_pmds[cnum].lval = value;

                  /*
                   * when context is load we use the split value
                   */
                  if (is_loaded) {
                        hw_value = value &  ovfl_mask;
                        value    = value & ~ovfl_mask;
                  }
            }
            /*
             * update reset values (not just for counters)
             */
            ctx->ctx_pmds[cnum].long_reset  = req->reg_long_reset;
            ctx->ctx_pmds[cnum].short_reset = req->reg_short_reset;

            /*
             * update randomization parameters (not just for counters)
             */
            ctx->ctx_pmds[cnum].seed = req->reg_random_seed;
            ctx->ctx_pmds[cnum].mask = req->reg_random_mask;

            /*
             * update context value
             */
            ctx->ctx_pmds[cnum].val  = value;

            /*
             * Keep track of what we use
             *
             * We do not keep track of PMC because we have to
             * systematically restore ALL of them.
             */
            CTX_USED_PMD(ctx, PMD_PMD_DEP(cnum));

            /*
             * mark this PMD register used as well
             */
            CTX_USED_PMD(ctx, RDEP(cnum));

            /*
             * make sure we do not try to reset on
             * restart because we have established new values
             */
            if (is_counting && state == PFM_CTX_MASKED) {
                  ctx->ctx_ovfl_regs[0] &= ~1UL << cnum;
            }

            if (is_loaded) {
                  /*
                   * write thread state
                   */
                  if (is_system == 0) ctx->th_pmds[cnum] = hw_value;

                  /*
                   * write hardware register if we can
                   */
                  if (can_access_pmu) {
                        ia64_set_pmd(cnum, hw_value);
                  } else {
#ifdef CONFIG_SMP
                        /*
                         * we are guaranteed that the task is not running on the other CPU,
                         * we indicate that this PMD will need to be reloaded if the task
                         * is rescheduled on the CPU it ran last on.
                         */
                        ctx->ctx_reload_pmds[0] |= 1UL << cnum;
#endif
                  }
            }

            DPRINT(("pmd[%u]=0x%lx ld=%d apmu=%d, hw_value=0x%lx ctx_pmd=0x%lx  short_reset=0x%lx "
                    "long_reset=0x%lx notify=%c seed=0x%lx mask=0x%lx used_pmds=0x%lx reset_pmds=0x%lx reload_pmds=0x%lx all_pmds=0x%lx ovfl_regs=0x%lx\n",
                  cnum,
                  value,
                  is_loaded,
                  can_access_pmu,
                  hw_value,
                  ctx->ctx_pmds[cnum].val,
                  ctx->ctx_pmds[cnum].short_reset,
                  ctx->ctx_pmds[cnum].long_reset,
                  PMC_OVFL_NOTIFY(ctx, cnum) ? 'Y':'N',
                  ctx->ctx_pmds[cnum].seed,
                  ctx->ctx_pmds[cnum].mask,
                  ctx->ctx_used_pmds[0],
                  ctx->ctx_pmds[cnum].reset_pmds[0],
                  ctx->ctx_reload_pmds[0],
                  ctx->ctx_all_pmds[0],
                  ctx->ctx_ovfl_regs[0]));
      }

      /*
       * make changes visible
       */
      if (can_access_pmu) ia64_srlz_d();

      return 0;

abort_mission:
      /*
       * for now, we have only one possibility for error
       */
      PFM_REG_RETFLAG_SET(req->reg_flags, PFM_REG_RETFL_EINVAL);
      return ret;
}

/*
 * By the way of PROTECT_CONTEXT(), interrupts are masked while we are in this function.
 * Therefore we know, we do not have to worry about the PMU overflow interrupt. If an
 * interrupt is delivered during the call, it will be kept pending until we leave, making
 * it appears as if it had been generated at the UNPROTECT_CONTEXT(). At least we are
 * guaranteed to return consistent data to the user, it may simply be old. It is not
 * trivial to treat the overflow while inside the call because you may end up in
 * some module sampling buffer code causing deadlocks.
 */
static int
pfm_read_pmds(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      struct task_struct *task;
      unsigned long val = 0UL, lval, ovfl_mask, sval;
      pfarg_reg_t *req = (pfarg_reg_t *)arg;
      unsigned int cnum, reg_flags = 0;
      int i, can_access_pmu = 0, state;
      int is_loaded, is_system, is_counting, expert_mode;
      int ret = -EINVAL;
      pfm_reg_check_t rd_func;

      /*
       * access is possible when loaded only for
       * self-monitoring tasks or in UP mode
       */

      state     = ctx->ctx_state;
      is_loaded = state == PFM_CTX_LOADED ? 1 : 0;
      is_system = ctx->ctx_fl_system;
      ovfl_mask = pmu_conf->ovfl_val;
      task      = ctx->ctx_task;

      if (state == PFM_CTX_ZOMBIE) return -EINVAL;

      if (likely(is_loaded)) {
            /*
             * In system wide and when the context is loaded, access can only happen
             * when the caller is running on the CPU being monitored by the session.
             * It does not have to be the owner (ctx_task) of the context per se.
             */
            if (unlikely(is_system && ctx->ctx_cpu != smp_processor_id())) {
                  DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
                  return -EBUSY;
            }
            /*
             * this can be true when not self-monitoring only in UP
             */
            can_access_pmu = GET_PMU_OWNER() == task || is_system ? 1 : 0;

            if (can_access_pmu) ia64_srlz_d();
      }
      expert_mode = pfm_sysctl.expert_mode; 

      DPRINT(("ld=%d apmu=%d ctx_state=%d\n",
            is_loaded,
            can_access_pmu,
            state));

      /*
       * on both UP and SMP, we can only read the PMD from the hardware register when
       * the task is the owner of the local PMU.
       */

      for (i = 0; i < count; i++, req++) {

            cnum        = req->reg_num;
            reg_flags   = req->reg_flags;

            if (unlikely(!PMD_IS_IMPL(cnum))) goto error;
            /*
             * we can only read the register that we use. That includes
             * the one we explicitly initialize AND the one we want included
             * in the sampling buffer (smpl_regs).
             *
             * Having this restriction allows optimization in the ctxsw routine
             * without compromising security (leaks)
             */
            if (unlikely(!CTX_IS_USED_PMD(ctx, cnum))) goto error;

            sval        = ctx->ctx_pmds[cnum].val;
            lval        = ctx->ctx_pmds[cnum].lval;
            is_counting = PMD_IS_COUNTING(cnum);

            /*
             * If the task is not the current one, then we check if the
             * PMU state is still in the local live register due to lazy ctxsw.
             * If true, then we read directly from the registers.
             */
            if (can_access_pmu){
                  val = ia64_get_pmd(cnum);
            } else {
                  /*
                   * context has been saved
                   * if context is zombie, then task does not exist anymore.
                   * In this case, we use the full value saved in the context (pfm_flush_regs()).
                   */
                  val = is_loaded ? ctx->th_pmds[cnum] : 0UL;
            }
            rd_func = pmu_conf->pmd_desc[cnum].read_check;

            if (is_counting) {
                  /*
                   * XXX: need to check for overflow when loaded
                   */
                  val &= ovfl_mask;
                  val += sval;
            }

            /*
             * execute read checker, if any
             */
            if (unlikely(expert_mode == 0 && rd_func)) {
                  unsigned long v = val;
                  ret = (*rd_func)(ctx->ctx_task, ctx, cnum, &v, regs);
                  if (ret) goto error;
                  val = v;
                  ret = -EINVAL;
            }

            PFM_REG_RETFLAG_SET(reg_flags, 0);

            DPRINT(("pmd[%u]=0x%lx\n", cnum, val));

            /*
             * update register return value, abort all if problem during copy.
             * we only modify the reg_flags field. no check mode is fine because
             * access has been verified upfront in sys_perfmonctl().
             */
            req->reg_value            = val;
            req->reg_flags            = reg_flags;
            req->reg_last_reset_val   = lval;
      }

      return 0;

error:
      PFM_REG_RETFLAG_SET(req->reg_flags, PFM_REG_RETFL_EINVAL);
      return ret;
}

int
pfm_mod_write_pmcs(struct task_struct *task, void *req, unsigned int nreq, struct pt_regs *regs)
{
      pfm_context_t *ctx;

      if (req == NULL) return -EINVAL;

      ctx = GET_PMU_CTX();

      if (ctx == NULL) return -EINVAL;

      /*
       * for now limit to current task, which is enough when calling
       * from overflow handler
       */
      if (task != current && ctx->ctx_fl_system == 0) return -EBUSY;

      return pfm_write_pmcs(ctx, req, nreq, regs);
}
EXPORT_SYMBOL(pfm_mod_write_pmcs);

int
pfm_mod_read_pmds(struct task_struct *task, void *req, unsigned int nreq, struct pt_regs *regs)
{
      pfm_context_t *ctx;

      if (req == NULL) return -EINVAL;

      ctx = GET_PMU_CTX();

      if (ctx == NULL) return -EINVAL;

      /*
       * for now limit to current task, which is enough when calling
       * from overflow handler
       */
      if (task != current && ctx->ctx_fl_system == 0) return -EBUSY;

      return pfm_read_pmds(ctx, req, nreq, regs);
}
EXPORT_SYMBOL(pfm_mod_read_pmds);

/*
 * Only call this function when a process it trying to
 * write the debug registers (reading is always allowed)
 */
int
pfm_use_debug_registers(struct task_struct *task)
{
      pfm_context_t *ctx = task->thread.pfm_context;
      unsigned long flags;
      int ret = 0;

      if (pmu_conf->use_rr_dbregs == 0) return 0;

      DPRINT(("called for [%d]\n", task_pid_nr(task)));

      /*
       * do it only once
       */
      if (task->thread.flags & IA64_THREAD_DBG_VALID) return 0;

      /*
       * Even on SMP, we do not need to use an atomic here because
       * the only way in is via ptrace() and this is possible only when the
       * process is stopped. Even in the case where the ctxsw out is not totally
       * completed by the time we come here, there is no way the 'stopped' process
       * could be in the middle of fiddling with the pfm_write_ibr_dbr() routine.
       * So this is always safe.
       */
      if (ctx && ctx->ctx_fl_using_dbreg == 1) return -1;

      LOCK_PFS(flags);

      /*
       * We cannot allow setting breakpoints when system wide monitoring
       * sessions are using the debug registers.
       */
      if (pfm_sessions.pfs_sys_use_dbregs> 0)
            ret = -1;
      else
            pfm_sessions.pfs_ptrace_use_dbregs++;

      DPRINT(("ptrace_use_dbregs=%u  sys_use_dbregs=%u by [%d] ret = %d\n",
              pfm_sessions.pfs_ptrace_use_dbregs,
              pfm_sessions.pfs_sys_use_dbregs,
              task_pid_nr(task), ret));

      UNLOCK_PFS(flags);

      return ret;
}

/*
 * This function is called for every task that exits with the
 * IA64_THREAD_DBG_VALID set. This indicates a task which was
 * able to use the debug registers for debugging purposes via
 * ptrace(). Therefore we know it was not using them for
 * perfmormance monitoring, so we only decrement the number
 * of "ptraced" debug register users to keep the count up to date
 */
int
pfm_release_debug_registers(struct task_struct *task)
{
      unsigned long flags;
      int ret;

      if (pmu_conf->use_rr_dbregs == 0) return 0;

      LOCK_PFS(flags);
      if (pfm_sessions.pfs_ptrace_use_dbregs == 0) {
            printk(KERN_ERR "perfmon: invalid release for [%d] ptrace_use_dbregs=0\n", task_pid_nr(task));
            ret = -1;
      }  else {
            pfm_sessions.pfs_ptrace_use_dbregs--;
            ret = 0;
      }
      UNLOCK_PFS(flags);

      return ret;
}

static int
pfm_restart(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      struct task_struct *task;
      pfm_buffer_fmt_t *fmt;
      pfm_ovfl_ctrl_t rst_ctrl;
      int state, is_system;
      int ret = 0;

      state     = ctx->ctx_state;
      fmt       = ctx->ctx_buf_fmt;
      is_system = ctx->ctx_fl_system;
      task      = PFM_CTX_TASK(ctx);

      switch(state) {
            case PFM_CTX_MASKED:
                  break;
            case PFM_CTX_LOADED: 
                  if (CTX_HAS_SMPL(ctx) && fmt->fmt_restart_active) break;
                  /* fall through */
            case PFM_CTX_UNLOADED:
            case PFM_CTX_ZOMBIE:
                  DPRINT(("invalid state=%d\n", state));
                  return -EBUSY;
            default:
                  DPRINT(("state=%d, cannot operate (no active_restart handler)\n", state));
                  return -EINVAL;
      }

      /*
       * In system wide and when the context is loaded, access can only happen
       * when the caller is running on the CPU being monitored by the session.
       * It does not have to be the owner (ctx_task) of the context per se.
       */
      if (is_system && ctx->ctx_cpu != smp_processor_id()) {
            DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
            return -EBUSY;
      }

      /* sanity check */
      if (unlikely(task == NULL)) {
            printk(KERN_ERR "perfmon: [%d] pfm_restart no task\n", task_pid_nr(current));
            return -EINVAL;
      }

      if (task == current || is_system) {

            fmt = ctx->ctx_buf_fmt;

            DPRINT(("restarting self %d ovfl=0x%lx\n",
                  task_pid_nr(task),
                  ctx->ctx_ovfl_regs[0]));

            if (CTX_HAS_SMPL(ctx)) {

                  prefetch(ctx->ctx_smpl_hdr);

                  rst_ctrl.bits.mask_monitoring = 0;
                  rst_ctrl.bits.reset_ovfl_pmds = 0;

                  if (state == PFM_CTX_LOADED)
                        ret = pfm_buf_fmt_restart_active(fmt, task, &rst_ctrl, ctx->ctx_smpl_hdr, regs);
                  else
                        ret = pfm_buf_fmt_restart(fmt, task, &rst_ctrl, ctx->ctx_smpl_hdr, regs);
            } else {
                  rst_ctrl.bits.mask_monitoring = 0;
                  rst_ctrl.bits.reset_ovfl_pmds = 1;
            }

            if (ret == 0) {
                  if (rst_ctrl.bits.reset_ovfl_pmds)
                        pfm_reset_regs(ctx, ctx->ctx_ovfl_regs, PFM_PMD_LONG_RESET);

                  if (rst_ctrl.bits.mask_monitoring == 0) {
                        DPRINT(("resuming monitoring for [%d]\n", task_pid_nr(task)));

                        if (state == PFM_CTX_MASKED) pfm_restore_monitoring(task);
                  } else {
                        DPRINT(("keeping monitoring stopped for [%d]\n", task_pid_nr(task)));

                        // cannot use pfm_stop_monitoring(task, regs);
                  }
            }
            /*
             * clear overflowed PMD mask to remove any stale information
             */
            ctx->ctx_ovfl_regs[0] = 0UL;

            /*
             * back to LOADED state
             */
            ctx->ctx_state = PFM_CTX_LOADED;

            /*
             * XXX: not really useful for self monitoring
             */
            ctx->ctx_fl_can_restart = 0;

            return 0;
      }

      /* 
       * restart another task
       */

      /*
       * When PFM_CTX_MASKED, we cannot issue a restart before the previous 
       * one is seen by the task.
       */
      if (state == PFM_CTX_MASKED) {
            if (ctx->ctx_fl_can_restart == 0) return -EINVAL;
            /*
             * will prevent subsequent restart before this one is
             * seen by other task
             */
            ctx->ctx_fl_can_restart = 0;
      }

      /*
       * if blocking, then post the semaphore is PFM_CTX_MASKED, i.e.
       * the task is blocked or on its way to block. That's the normal
       * restart path. If the monitoring is not masked, then the task
       * can be actively monitoring and we cannot directly intervene.
       * Therefore we use the trap mechanism to catch the task and
       * force it to reset the buffer/reset PMDs.
       *
       * if non-blocking, then we ensure that the task will go into
       * pfm_handle_work() before returning to user mode.
       *
       * We cannot explicitly reset another task, it MUST always
       * be done by the task itself. This works for system wide because
       * the tool that is controlling the session is logically doing 
       * "self-monitoring".
       */
      if (CTX_OVFL_NOBLOCK(ctx) == 0 && state == PFM_CTX_MASKED) {
            DPRINT(("unblocking [%d] \n", task_pid_nr(task)));
            complete(&ctx->ctx_restart_done);
      } else {
            DPRINT(("[%d] armed exit trap\n", task_pid_nr(task)));

            ctx->ctx_fl_trap_reason = PFM_TRAP_REASON_RESET;

            PFM_SET_WORK_PENDING(task, 1);

            pfm_set_task_notify(task);

            /*
             * XXX: send reschedule if task runs on another CPU
             */
      }
      return 0;
}

static int
pfm_debug(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      unsigned int m = *(unsigned int *)arg;

      pfm_sysctl.debug = m == 0 ? 0 : 1;

      printk(KERN_INFO "perfmon debugging %s (timing reset)\n", pfm_sysctl.debug ? "on" : "off");

      if (m == 0) {
            memset(pfm_stats, 0, sizeof(pfm_stats));
            for(m=0; m < NR_CPUS; m++) pfm_stats[m].pfm_ovfl_intr_cycles_min = ~0UL;
      }
      return 0;
}

/*
 * arg can be NULL and count can be zero for this function
 */
static int
pfm_write_ibr_dbr(int mode, pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      struct thread_struct *thread = NULL;
      struct task_struct *task;
      pfarg_dbreg_t *req = (pfarg_dbreg_t *)arg;
      unsigned long flags;
      dbreg_t dbreg;
      unsigned int rnum;
      int first_time;
      int ret = 0, state;
      int i, can_access_pmu = 0;
      int is_system, is_loaded;

      if (pmu_conf->use_rr_dbregs == 0) return -EINVAL;

      state     = ctx->ctx_state;
      is_loaded = state == PFM_CTX_LOADED ? 1 : 0;
      is_system = ctx->ctx_fl_system;
      task      = ctx->ctx_task;

      if (state == PFM_CTX_ZOMBIE) return -EINVAL;

      /*
       * on both UP and SMP, we can only write to the PMC when the task is
       * the owner of the local PMU.
       */
      if (is_loaded) {
            thread = &task->thread;
            /*
             * In system wide and when the context is loaded, access can only happen
             * when the caller is running on the CPU being monitored by the session.
             * It does not have to be the owner (ctx_task) of the context per se.
             */
            if (unlikely(is_system && ctx->ctx_cpu != smp_processor_id())) {
                  DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
                  return -EBUSY;
            }
            can_access_pmu = GET_PMU_OWNER() == task || is_system ? 1 : 0;
      }

      /*
       * we do not need to check for ipsr.db because we do clear ibr.x, dbr.r, and dbr.w
       * ensuring that no real breakpoint can be installed via this call.
       *
       * IMPORTANT: regs can be NULL in this function
       */

      first_time = ctx->ctx_fl_using_dbreg == 0;

      /*
       * don't bother if we are loaded and task is being debugged
       */
      if (is_loaded && (thread->flags & IA64_THREAD_DBG_VALID) != 0) {
            DPRINT(("debug registers already in use for [%d]\n", task_pid_nr(task)));
            return -EBUSY;
      }

      /*
       * check for debug registers in system wide mode
       *
       * If though a check is done in pfm_context_load(),
       * we must repeat it here, in case the registers are
       * written after the context is loaded
       */
      if (is_loaded) {
            LOCK_PFS(flags);

            if (first_time && is_system) {
                  if (pfm_sessions.pfs_ptrace_use_dbregs)
                        ret = -EBUSY;
                  else
                        pfm_sessions.pfs_sys_use_dbregs++;
            }
            UNLOCK_PFS(flags);
      }

      if (ret != 0) return ret;

      /*
       * mark ourself as user of the debug registers for
       * perfmon purposes.
       */
      ctx->ctx_fl_using_dbreg = 1;

      /*
       * clear hardware registers to make sure we don't
       * pick up stale state.
       *
       * for a system wide session, we do not use
       * thread.dbr, thread.ibr because this process
       * never leaves the current CPU and the state
       * is shared by all processes running on it
       */
      if (first_time && can_access_pmu) {
            DPRINT(("[%d] clearing ibrs, dbrs\n", task_pid_nr(task)));
            for (i=0; i < pmu_conf->num_ibrs; i++) {
                  ia64_set_ibr(i, 0UL);
                  ia64_dv_serialize_instruction();
            }
            ia64_srlz_i();
            for (i=0; i < pmu_conf->num_dbrs; i++) {
                  ia64_set_dbr(i, 0UL);
                  ia64_dv_serialize_data();
            }
            ia64_srlz_d();
      }

      /*
       * Now install the values into the registers
       */
      for (i = 0; i < count; i++, req++) {

            rnum      = req->dbreg_num;
            dbreg.val = req->dbreg_value;

            ret = -EINVAL;

            if ((mode == PFM_CODE_RR && rnum >= PFM_NUM_IBRS) || ((mode == PFM_DATA_RR) && rnum >= PFM_NUM_DBRS)) {
                  DPRINT(("invalid register %u val=0x%lx mode=%d i=%d count=%d\n",
                          rnum, dbreg.val, mode, i, count));

                  goto abort_mission;
            }

            /*
             * make sure we do not install enabled breakpoint
             */
            if (rnum & 0x1) {
                  if (mode == PFM_CODE_RR)
                        dbreg.ibr.ibr_x = 0;
                  else
                        dbreg.dbr.dbr_r = dbreg.dbr.dbr_w = 0;
            }

            PFM_REG_RETFLAG_SET(req->dbreg_flags, 0);

            /*
             * Debug registers, just like PMC, can only be modified
             * by a kernel call. Moreover, perfmon() access to those
             * registers are centralized in this routine. The hardware
             * does not modify the value of these registers, therefore,
             * if we save them as they are written, we can avoid having
             * to save them on context switch out. This is made possible
             * by the fact that when perfmon uses debug registers, ptrace()
             * won't be able to modify them concurrently.
             */
            if (mode == PFM_CODE_RR) {
                  CTX_USED_IBR(ctx, rnum);

                  if (can_access_pmu) {
                        ia64_set_ibr(rnum, dbreg.val);
                        ia64_dv_serialize_instruction();
                  }

                  ctx->ctx_ibrs[rnum] = dbreg.val;

                  DPRINT(("write ibr%u=0x%lx used_ibrs=0x%x ld=%d apmu=%d\n",
                        rnum, dbreg.val, ctx->ctx_used_ibrs[0], is_loaded, can_access_pmu));
            } else {
                  CTX_USED_DBR(ctx, rnum);

                  if (can_access_pmu) {
                        ia64_set_dbr(rnum, dbreg.val);
                        ia64_dv_serialize_data();
                  }
                  ctx->ctx_dbrs[rnum] = dbreg.val;

                  DPRINT(("write dbr%u=0x%lx used_dbrs=0x%x ld=%d apmu=%d\n",
                        rnum, dbreg.val, ctx->ctx_used_dbrs[0], is_loaded, can_access_pmu));
            }
      }

      return 0;

abort_mission:
      /*
       * in case it was our first attempt, we undo the global modifications
       */
      if (first_time) {
            LOCK_PFS(flags);
            if (ctx->ctx_fl_system) {
                  pfm_sessions.pfs_sys_use_dbregs--;
            }
            UNLOCK_PFS(flags);
            ctx->ctx_fl_using_dbreg = 0;
      }
      /*
       * install error return flag
       */
      PFM_REG_RETFLAG_SET(req->dbreg_flags, PFM_REG_RETFL_EINVAL);

      return ret;
}

static int
pfm_write_ibrs(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      return pfm_write_ibr_dbr(PFM_CODE_RR, ctx, arg, count, regs);
}

static int
pfm_write_dbrs(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      return pfm_write_ibr_dbr(PFM_DATA_RR, ctx, arg, count, regs);
}

int
pfm_mod_write_ibrs(struct task_struct *task, void *req, unsigned int nreq, struct pt_regs *regs)
{
      pfm_context_t *ctx;

      if (req == NULL) return -EINVAL;

      ctx = GET_PMU_CTX();

      if (ctx == NULL) return -EINVAL;

      /*
       * for now limit to current task, which is enough when calling
       * from overflow handler
       */
      if (task != current && ctx->ctx_fl_system == 0) return -EBUSY;

      return pfm_write_ibrs(ctx, req, nreq, regs);
}
EXPORT_SYMBOL(pfm_mod_write_ibrs);

int
pfm_mod_write_dbrs(struct task_struct *task, void *req, unsigned int nreq, struct pt_regs *regs)
{
      pfm_context_t *ctx;

      if (req == NULL) return -EINVAL;

      ctx = GET_PMU_CTX();

      if (ctx == NULL) return -EINVAL;

      /*
       * for now limit to current task, which is enough when calling
       * from overflow handler
       */
      if (task != current && ctx->ctx_fl_system == 0) return -EBUSY;

      return pfm_write_dbrs(ctx, req, nreq, regs);
}
EXPORT_SYMBOL(pfm_mod_write_dbrs);


static int
pfm_get_features(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      pfarg_features_t *req = (pfarg_features_t *)arg;

      req->ft_version = PFM_VERSION;
      return 0;
}

static int
pfm_stop(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      struct pt_regs *tregs;
      struct task_struct *task = PFM_CTX_TASK(ctx);
      int state, is_system;

      state     = ctx->ctx_state;
      is_system = ctx->ctx_fl_system;

      /*
       * context must be attached to issue the stop command (includes LOADED,MASKED,ZOMBIE)
       */
      if (state == PFM_CTX_UNLOADED) return -EINVAL;

      /*
       * In system wide and when the context is loaded, access can only happen
       * when the caller is running on the CPU being monitored by the session.
       * It does not have to be the owner (ctx_task) of the context per se.
       */
      if (is_system && ctx->ctx_cpu != smp_processor_id()) {
            DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
            return -EBUSY;
      }
      DPRINT(("task [%d] ctx_state=%d is_system=%d\n",
            task_pid_nr(PFM_CTX_TASK(ctx)),
            state,
            is_system));
      /*
       * in system mode, we need to update the PMU directly
       * and the user level state of the caller, which may not
       * necessarily be the creator of the context.
       */
      if (is_system) {
            /*
             * Update local PMU first
             *
             * disable dcr pp
             */
            ia64_setreg(_IA64_REG_CR_DCR, ia64_getreg(_IA64_REG_CR_DCR) & ~IA64_DCR_PP);
            ia64_srlz_i();

            /*
             * update local cpuinfo
             */
            PFM_CPUINFO_CLEAR(PFM_CPUINFO_DCR_PP);

            /*
             * stop monitoring, does srlz.i
             */
            pfm_clear_psr_pp();

            /*
             * stop monitoring in the caller
             */
            ia64_psr(regs)->pp = 0;

            return 0;
      }
      /*
       * per-task mode
       */

      if (task == current) {
            /* stop monitoring  at kernel level */
            pfm_clear_psr_up();

            /*
             * stop monitoring at the user level
             */
            ia64_psr(regs)->up = 0;
      } else {
            tregs = task_pt_regs(task);

            /*
             * stop monitoring at the user level
             */
            ia64_psr(tregs)->up = 0;

            /*
             * monitoring disabled in kernel at next reschedule
             */
            ctx->ctx_saved_psr_up = 0;
            DPRINT(("task=[%d]\n", task_pid_nr(task)));
      }
      return 0;
}


static int
pfm_start(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      struct pt_regs *tregs;
      int state, is_system;

      state     = ctx->ctx_state;
      is_system = ctx->ctx_fl_system;

      if (state != PFM_CTX_LOADED) return -EINVAL;

      /*
       * In system wide and when the context is loaded, access can only happen
       * when the caller is running on the CPU being monitored by the session.
       * It does not have to be the owner (ctx_task) of the context per se.
       */
      if (is_system && ctx->ctx_cpu != smp_processor_id()) {
            DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
            return -EBUSY;
      }

      /*
       * in system mode, we need to update the PMU directly
       * and the user level state of the caller, which may not
       * necessarily be the creator of the context.
       */
      if (is_system) {

            /*
             * set user level psr.pp for the caller
             */
            ia64_psr(regs)->pp = 1;

            /*
             * now update the local PMU and cpuinfo
             */
            PFM_CPUINFO_SET(PFM_CPUINFO_DCR_PP);

            /*
             * start monitoring at kernel level
             */
            pfm_set_psr_pp();

            /* enable dcr pp */
            ia64_setreg(_IA64_REG_CR_DCR, ia64_getreg(_IA64_REG_CR_DCR) | IA64_DCR_PP);
            ia64_srlz_i();

            return 0;
      }

      /*
       * per-process mode
       */

      if (ctx->ctx_task == current) {

            /* start monitoring at kernel level */
            pfm_set_psr_up();

            /*
             * activate monitoring at user level
             */
            ia64_psr(regs)->up = 1;

      } else {
            tregs = task_pt_regs(ctx->ctx_task);

            /*
             * start monitoring at the kernel level the next
             * time the task is scheduled
             */
            ctx->ctx_saved_psr_up = IA64_PSR_UP;

            /*
             * activate monitoring at user level
             */
            ia64_psr(tregs)->up = 1;
      }
      return 0;
}

static int
pfm_get_pmc_reset(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      pfarg_reg_t *req = (pfarg_reg_t *)arg;
      unsigned int cnum;
      int i;
      int ret = -EINVAL;

      for (i = 0; i < count; i++, req++) {

            cnum = req->reg_num;

            if (!PMC_IS_IMPL(cnum)) goto abort_mission;

            req->reg_value = PMC_DFL_VAL(cnum);

            PFM_REG_RETFLAG_SET(req->reg_flags, 0);

            DPRINT(("pmc_reset_val pmc[%u]=0x%lx\n", cnum, req->reg_value));
      }
      return 0;

abort_mission:
      PFM_REG_RETFLAG_SET(req->reg_flags, PFM_REG_RETFL_EINVAL);
      return ret;
}

static int
pfm_check_task_exist(pfm_context_t *ctx)
{
      struct task_struct *g, *t;
      int ret = -ESRCH;

      read_lock(&tasklist_lock);

      do_each_thread (g, t) {
            if (t->thread.pfm_context == ctx) {
                  ret = 0;
                  break;
            }
      } while_each_thread (g, t);

      read_unlock(&tasklist_lock);

      DPRINT(("pfm_check_task_exist: ret=%d ctx=%p\n", ret, ctx));

      return ret;
}

static int
pfm_context_load(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      struct task_struct *task;
      struct thread_struct *thread;
      struct pfm_context_t *old;
      unsigned long flags;
#ifndef CONFIG_SMP
      struct task_struct *owner_task = NULL;
#endif
      pfarg_load_t *req = (pfarg_load_t *)arg;
      unsigned long *pmcs_source, *pmds_source;
      int the_cpu;
      int ret = 0;
      int state, is_system, set_dbregs = 0;

      state     = ctx->ctx_state;
      is_system = ctx->ctx_fl_system;
      /*
       * can only load from unloaded or terminated state
       */
      if (state != PFM_CTX_UNLOADED) {
            DPRINT(("cannot load to [%d], invalid ctx_state=%d\n",
                  req->load_pid,
                  ctx->ctx_state));
            return -EBUSY;
      }

      DPRINT(("load_pid [%d] using_dbreg=%d\n", req->load_pid, ctx->ctx_fl_using_dbreg));

      if (CTX_OVFL_NOBLOCK(ctx) == 0 && req->load_pid == current->pid) {
            DPRINT(("cannot use blocking mode on self\n"));
            return -EINVAL;
      }

      ret = pfm_get_task(ctx, req->load_pid, &task);
      if (ret) {
            DPRINT(("load_pid [%d] get_task=%d\n", req->load_pid, ret));
            return ret;
      }

      ret = -EINVAL;

      /*
       * system wide is self monitoring only
       */
      if (is_system && task != current) {
            DPRINT(("system wide is self monitoring only load_pid=%d\n",
                  req->load_pid));
            goto error;
      }

      thread = &task->thread;

      ret = 0;
      /*
       * cannot load a context which is using range restrictions,
       * into a task that is being debugged.
       */
      if (ctx->ctx_fl_using_dbreg) {
            if (thread->flags & IA64_THREAD_DBG_VALID) {
                  ret = -EBUSY;
                  DPRINT(("load_pid [%d] task is debugged, cannot load range restrictions\n", req->load_pid));
                  goto error;
            }
            LOCK_PFS(flags);

            if (is_system) {
                  if (pfm_sessions.pfs_ptrace_use_dbregs) {
                        DPRINT(("cannot load [%d] dbregs in use\n",
                                          task_pid_nr(task)));
                        ret = -EBUSY;
                  } else {
                        pfm_sessions.pfs_sys_use_dbregs++;
                        DPRINT(("load [%d] increased sys_use_dbreg=%u\n", task_pid_nr(task), pfm_sessions.pfs_sys_use_dbregs));
                        set_dbregs = 1;
                  }
            }

            UNLOCK_PFS(flags);

            if (ret) goto error;
      }

      /*
       * SMP system-wide monitoring implies self-monitoring.
       *
       * The programming model expects the task to
       * be pinned on a CPU throughout the session.
       * Here we take note of the current CPU at the
       * time the context is loaded. No call from
       * another CPU will be allowed.
       *
       * The pinning via shed_setaffinity()
       * must be done by the calling task prior
       * to this call.
       *
       * systemwide: keep track of CPU this session is supposed to run on
       */
      the_cpu = ctx->ctx_cpu = smp_processor_id();

      ret = -EBUSY;
      /*
       * now reserve the session
       */
      ret = pfm_reserve_session(current, is_system, the_cpu);
      if (ret) goto error;

      /*
       * task is necessarily stopped at this point.
       *
       * If the previous context was zombie, then it got removed in
       * pfm_save_regs(). Therefore we should not see it here.
       * If we see a context, then this is an active context
       *
       * XXX: needs to be atomic
       */
      DPRINT(("before cmpxchg() old_ctx=%p new_ctx=%p\n",
            thread->pfm_context, ctx));

      ret = -EBUSY;
      old = ia64_cmpxchg(acq, &thread->pfm_context, NULL, ctx, sizeof(pfm_context_t *));
      if (old != NULL) {
            DPRINT(("load_pid [%d] already has a context\n", req->load_pid));
            goto error_unres;
      }

      pfm_reset_msgq(ctx);

      ctx->ctx_state = PFM_CTX_LOADED;

      /*
       * link context to task
       */
      ctx->ctx_task = task;

      if (is_system) {
            /*
             * we load as stopped
             */
            PFM_CPUINFO_SET(PFM_CPUINFO_SYST_WIDE);
            PFM_CPUINFO_CLEAR(PFM_CPUINFO_DCR_PP);

            if (ctx->ctx_fl_excl_idle) PFM_CPUINFO_SET(PFM_CPUINFO_EXCL_IDLE);
      } else {
            thread->flags |= IA64_THREAD_PM_VALID;
      }

      /*
       * propagate into thread-state
       */
      pfm_copy_pmds(task, ctx);
      pfm_copy_pmcs(task, ctx);

      pmcs_source = ctx->th_pmcs;
      pmds_source = ctx->th_pmds;

      /*
       * always the case for system-wide
       */
      if (task == current) {

            if (is_system == 0) {

                  /* allow user level control */
                  ia64_psr(regs)->sp = 0;
                  DPRINT(("clearing psr.sp for [%d]\n", task_pid_nr(task)));

                  SET_LAST_CPU(ctx, smp_processor_id());
                  INC_ACTIVATION();
                  SET_ACTIVATION(ctx);
#ifndef CONFIG_SMP
                  /*
                   * push the other task out, if any
                   */
                  owner_task = GET_PMU_OWNER();
                  if (owner_task) pfm_lazy_save_regs(owner_task);
#endif
            }
            /*
             * load all PMD from ctx to PMU (as opposed to thread state)
             * restore all PMC from ctx to PMU
             */
            pfm_restore_pmds(pmds_source, ctx->ctx_all_pmds[0]);
            pfm_restore_pmcs(pmcs_source, ctx->ctx_all_pmcs[0]);

            ctx->ctx_reload_pmcs[0] = 0UL;
            ctx->ctx_reload_pmds[0] = 0UL;

            /*
             * guaranteed safe by earlier check against DBG_VALID
             */
            if (ctx->ctx_fl_using_dbreg) {
                  pfm_restore_ibrs(ctx->ctx_ibrs, pmu_conf->num_ibrs);
                  pfm_restore_dbrs(ctx->ctx_dbrs, pmu_conf->num_dbrs);
            }
            /*
             * set new ownership
             */
            SET_PMU_OWNER(task, ctx);

            DPRINT(("context loaded on PMU for [%d]\n", task_pid_nr(task)));
      } else {
            /*
             * when not current, task MUST be stopped, so this is safe
             */
            regs = task_pt_regs(task);

            /* force a full reload */
            ctx->ctx_last_activation = PFM_INVALID_ACTIVATION;
            SET_LAST_CPU(ctx, -1);

            /* initial saved psr (stopped) */
            ctx->ctx_saved_psr_up = 0UL;
            ia64_psr(regs)->up = ia64_psr(regs)->pp = 0;
      }

      ret = 0;

error_unres:
      if (ret) pfm_unreserve_session(ctx, ctx->ctx_fl_system, the_cpu);
error:
      /*
       * we must undo the dbregs setting (for system-wide)
       */
      if (ret && set_dbregs) {
            LOCK_PFS(flags);
            pfm_sessions.pfs_sys_use_dbregs--;
            UNLOCK_PFS(flags);
      }
      /*
       * release task, there is now a link with the context
       */
      if (is_system == 0 && task != current) {
            pfm_put_task(task);

            if (ret == 0) {
                  ret = pfm_check_task_exist(ctx);
                  if (ret) {
                        ctx->ctx_state = PFM_CTX_UNLOADED;
                        ctx->ctx_task  = NULL;
                  }
            }
      }
      return ret;
}

/*
 * in this function, we do not need to increase the use count
 * for the task via get_task_struct(), because we hold the
 * context lock. If the task were to disappear while having
 * a context attached, it would go through pfm_exit_thread()
 * which also grabs the context lock  and would therefore be blocked
 * until we are here.
 */
static void pfm_flush_pmds(struct task_struct *, pfm_context_t *ctx);

static int
pfm_context_unload(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
      struct task_struct *task = PFM_CTX_TASK(ctx);
      struct pt_regs *tregs;
      int prev_state, is_system;
      int ret;

      DPRINT(("ctx_state=%d task [%d]\n", ctx->ctx_state, task ? task_pid_nr(task) : -1));

      prev_state = ctx->ctx_state;
      is_system  = ctx->ctx_fl_system;

      /*
       * unload only when necessary
       */
      if (prev_state == PFM_CTX_UNLOADED) {
            DPRINT(("ctx_state=%d, nothing to do\n", prev_state));
            return 0;
      }

      /*
       * clear psr and dcr bits
       */
      ret = pfm_stop(ctx, NULL, 0, regs);
      if (ret) return ret;

      ctx->ctx_state = PFM_CTX_UNLOADED;

      /*
       * in system mode, we need to update the PMU directly
       * and the user level state of the caller, which may not
       * necessarily be the creator of the context.
       */
      if (is_system) {

            /*
             * Update cpuinfo
             *
             * local PMU is taken care of in pfm_stop()
             */
            PFM_CPUINFO_CLEAR(PFM_CPUINFO_SYST_WIDE);
            PFM_CPUINFO_CLEAR(PFM_CPUINFO_EXCL_IDLE);

            /*
             * save PMDs in context
             * release ownership
             */
            pfm_flush_pmds(current, ctx);

            /*
             * at this point we are done with the PMU
             * so we can unreserve the resource.
             */
            if (prev_state != PFM_CTX_ZOMBIE) 
                  pfm_unreserve_session(ctx, 1 , ctx->ctx_cpu);

            /*
             * disconnect context from task
             */
            task->thread.pfm_context = NULL;
            /*
             * disconnect task from context
             */
            ctx->ctx_task = NULL;

            /*
             * There is nothing more to cleanup here.
             */
            return 0;
      }

      /*
       * per-task mode
       */
      tregs = task == current ? regs : task_pt_regs(task);

      if (task == current) {
            /*
             * cancel user level control
             */
            ia64_psr(regs)->sp = 1;

            DPRINT(("setting psr.sp for [%d]\n", task_pid_nr(task)));
      }
      /*
       * save PMDs to context
       * release ownership
       */
      pfm_flush_pmds(task, ctx);

      /*
       * at this point we are done with the PMU
       * so we can unreserve the resource.
       *
       * when state was ZOMBIE, we have already unreserved.
       */
      if (prev_state != PFM_CTX_ZOMBIE) 
            pfm_unreserve_session(ctx, 0 , ctx->ctx_cpu);

      /*
       * reset activation counter and psr
       */
      ctx->ctx_last_activation = PFM_INVALID_ACTIVATION;
      SET_LAST_CPU(ctx, -1);

      /*
       * PMU state will not be restored
       */
      task->thread.flags &= ~IA64_THREAD_PM_VALID;

      /*
       * break links between context and task
       */
      task->thread.pfm_context  = NULL;
      ctx->ctx_task             = NULL;

      PFM_SET_WORK_PENDING(task, 0);

      ctx->ctx_fl_trap_reason  = PFM_TRAP_REASON_NONE;
      ctx->ctx_fl_can_restart  = 0;
      ctx->ctx_fl_going_zombie = 0;

      DPRINT(("disconnected [%d] from context\n", task_pid_nr(task)));

      return 0;
}


/*
 * called only from exit_thread(): task == current
 * we come here only if current has a context attached (loaded or masked)
 */
void
pfm_exit_thread(struct task_struct *task)
{
      pfm_context_t *ctx;
      unsigned long flags;
      struct pt_regs *regs = task_pt_regs(task);
      int ret, state;
      int free_ok = 0;

      ctx = PFM_GET_CTX(task);

      PROTECT_CTX(ctx, flags);

      DPRINT(("state=%d task [%d]\n", ctx->ctx_state, task_pid_nr(task)));

      state = ctx->ctx_state;
      switch(state) {
            case PFM_CTX_UNLOADED:
                  /*
                   * only comes to this function if pfm_context is not NULL, i.e., cannot
                   * be in unloaded state
                   */
                  printk(KERN_ERR "perfmon: pfm_exit_thread [%d] ctx unloaded\n", task_pid_nr(task));
                  break;
            case PFM_CTX_LOADED:
            case PFM_CTX_MASKED:
                  ret = pfm_context_unload(ctx, NULL, 0, regs);
                  if (ret) {
                        printk(KERN_ERR "perfmon: pfm_exit_thread [%d] state=%d unload failed %d\n", task_pid_nr(task), state, ret);
                  }
                  DPRINT(("ctx unloaded for current state was %d\n", state));

                  pfm_end_notify_user(ctx);
                  break;
            case PFM_CTX_ZOMBIE:
                  ret = pfm_context_unload(ctx, NULL, 0, regs);
                  if (ret) {
                        printk(KERN_ERR "perfmon: pfm_exit_thread [%d] state=%d unload failed %d\n", task_pid_nr(task), state, ret);
                  }
                  free_ok = 1;
                  break;
            default:
                  printk(KERN_ERR "perfmon: pfm_exit_thread [%d] unexpected state=%d\n", task_pid_nr(task), state);
                  break;
      }
      UNPROTECT_CTX(ctx, flags);

      { u64 psr = pfm_get_psr();
        BUG_ON(psr & (IA64_PSR_UP|IA64_PSR_PP));
        BUG_ON(GET_PMU_OWNER());
        BUG_ON(ia64_psr(regs)->up);
        BUG_ON(ia64_psr(regs)->pp);
      }

      /*
       * All memory free operations (especially for vmalloc'ed memory)
       * MUST be done with interrupts ENABLED.
       */
      if (free_ok) pfm_context_free(ctx);
}

/*
 * functions MUST be listed in the increasing order of their index (see permfon.h)
 */
#define PFM_CMD(name, flags, arg_count, arg_type, getsz) { name, #name, flags, arg_count, sizeof(arg_type), getsz }
#define PFM_CMD_S(name, flags) { name, #name, flags, 0, 0, NULL }
#define PFM_CMD_PCLRWS  (PFM_CMD_FD|PFM_CMD_ARG_RW|PFM_CMD_STOP)
#define PFM_CMD_PCLRW   (PFM_CMD_FD|PFM_CMD_ARG_RW)
#define PFM_CMD_NONE    { NULL, "no-cmd", 0, 0, 0, NULL}

static pfm_cmd_desc_t pfm_cmd_tab[]={
/* 0  */PFM_CMD_NONE,
/* 1  */PFM_CMD(pfm_write_pmcs, PFM_CMD_PCLRWS, PFM_CMD_ARG_MANY, pfarg_reg_t, NULL),
/* 2  */PFM_CMD(pfm_write_pmds, PFM_CMD_PCLRWS, PFM_CMD_ARG_MANY, pfarg_reg_t, NULL),
/* 3  */PFM_CMD(pfm_read_pmds, PFM_CMD_PCLRWS, PFM_CMD_ARG_MANY, pfarg_reg_t, NULL),
/* 4  */PFM_CMD_S(pfm_stop, PFM_CMD_PCLRWS),
/* 5  */PFM_CMD_S(pfm_start, PFM_CMD_PCLRWS),
/* 6  */PFM_CMD_NONE,
/* 7  */PFM_CMD_NONE,
/* 8  */PFM_CMD(pfm_context_create, PFM_CMD_ARG_RW, 1, pfarg_context_t, pfm_ctx_getsize),
/* 9  */PFM_CMD_NONE,
/* 10 */PFM_CMD_S(pfm_restart, PFM_CMD_PCLRW),
/* 11 */PFM_CMD_NONE,
/* 12 */PFM_CMD(pfm_get_features, PFM_CMD_ARG_RW, 1, pfarg_features_t, NULL),
/* 13 */PFM_CMD(pfm_debug, 0, 1, unsigned int, NULL),
/* 14 */PFM_CMD_NONE,
/* 15 */PFM_CMD(pfm_get_pmc_reset, PFM_CMD_ARG_RW, PFM_CMD_ARG_MANY, pfarg_reg_t, NULL),
/* 16 */PFM_CMD(pfm_context_load, PFM_CMD_PCLRWS, 1, pfarg_load_t, NULL),
/* 17 */PFM_CMD_S(pfm_context_unload, PFM_CMD_PCLRWS),
/* 18 */PFM_CMD_NONE,
/* 19 */PFM_CMD_NONE,
/* 20 */PFM_CMD_NONE,
/* 21 */PFM_CMD_NONE,
/* 22 */PFM_CMD_NONE,
/* 23 */PFM_CMD_NONE,
/* 24 */PFM_CMD_NONE,
/* 25 */PFM_CMD_NONE,
/* 26 */PFM_CMD_NONE,
/* 27 */PFM_CMD_NONE,
/* 28 */PFM_CMD_NONE,
/* 29 */PFM_CMD_NONE,
/* 30 */PFM_CMD_NONE,
/* 31 */PFM_CMD_NONE,
/* 32 */PFM_CMD(pfm_write_ibrs, PFM_CMD_PCLRWS, PFM_CMD_ARG_MANY, pfarg_dbreg_t, NULL),
/* 33 */PFM_CMD(pfm_write_dbrs, PFM_CMD_PCLRWS, PFM_CMD_ARG_MANY, pfarg_dbreg_t, NULL)
};
#define PFM_CMD_COUNT   (sizeof(pfm_cmd_tab)/sizeof(pfm_cmd_desc_t))

static int
pfm_check_task_state(pfm_context_t *ctx, int cmd, unsigned long flags)
{
      struct task_struct *task;
      int state, old_state;

recheck:
      state = ctx->ctx_state;
      task  = ctx->ctx_task;

      if (task == NULL) {
            DPRINT(("context %d no task, state=%d\n", ctx->ctx_fd, state));
            return 0;
      }

      DPRINT(("context %d state=%d [%d] task_state=%ld must_stop=%d\n",
            ctx->ctx_fd,
            state,
            task_pid_nr(task),
            task->state, PFM_CMD_STOPPED(cmd)));

      /*
       * self-monitoring always ok.
       *
       * for system-wide the caller can either be the creator of the
       * context (to one to which the context is attached to) OR
       * a task running on the same CPU as the session.
       */
      if (task == current || ctx->ctx_fl_system) return 0;

      /*
       * we are monitoring another thread
       */
      switch(state) {
            case PFM_CTX_UNLOADED:
                  /*
                   * if context is UNLOADED we are safe to go
                   */
                  return 0;
            case PFM_CTX_ZOMBIE:
                  /*
                   * no command can operate on a zombie context
                   */
                  DPRINT(("cmd %d state zombie cannot operate on context\n", cmd));
                  return -EINVAL;
            case PFM_CTX_MASKED:
                  /*
                   * PMU state has been saved to software even though
                   * the thread may still be running.
                   */
                  if (cmd != PFM_UNLOAD_CONTEXT) return 0;
      }

      /*
       * context is LOADED or MASKED. Some commands may need to have 
       * the task stopped.
       *
       * We could lift this restriction for UP but it would mean that
       * the user has no guarantee the task would not run between
       * two successive calls to perfmonctl(). That's probably OK.
       * If this user wants to ensure the task does not run, then
       * the task must be stopped.
       */
      if (PFM_CMD_STOPPED(cmd)) {
            if ((task->state != TASK_STOPPED) && (task->state != TASK_TRACED)) {
                  DPRINT(("[%d] task not in stopped state\n", task_pid_nr(task)));
                  return -EBUSY;
            }
            /*
             * task is now stopped, wait for ctxsw out
             *
             * This is an interesting point in the code.
             * We need to unprotect the context because
             * the pfm_save_regs() routines needs to grab
             * the same lock. There are danger in doing
             * this because it leaves a window open for
             * another task to get access to the context
             * and possibly change its state. The one thing
             * that is not possible is for the context to disappear
             * because we are protected by the VFS layer, i.e.,
             * get_fd()/put_fd().
             */
            old_state = state;

            UNPROTECT_CTX(ctx, flags);

            wait_task_inactive(task);

            PROTECT_CTX(ctx, flags);

            /*
             * we must recheck to verify if state has changed
             */
            if (ctx->ctx_state != old_state) {
                  DPRINT(("old_state=%d new_state=%d\n", old_state, ctx->ctx_state));
                  goto recheck;
            }
      }
      return 0;
}

/*
 * system-call entry point (must return long)
 */
asmlinkage long
sys_perfmonctl (int fd, int cmd, void __user *arg, int count)
{
      struct file *file = NULL;
      pfm_context_t *ctx = NULL;
      unsigned long flags = 0UL;
      void *args_k = NULL;
      long ret; /* will expand int return types */
      size_t base_sz, sz, xtra_sz = 0;
      int narg, completed_args = 0, call_made = 0, cmd_flags;
      int (*func)(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs);
      int (*getsize)(void *arg, size_t *sz);
#define PFM_MAX_ARGSIZE 4096

      /*
       * reject any call if perfmon was disabled at initialization
       */
      if (unlikely(pmu_conf == NULL)) return -ENOSYS;

      if (unlikely(cmd < 0 || cmd >= PFM_CMD_COUNT)) {
            DPRINT(("invalid cmd=%d\n", cmd));
            return -EINVAL;
      }

      func      = pfm_cmd_tab[cmd].cmd_func;
      narg      = pfm_cmd_tab[cmd].cmd_narg;
      base_sz   = pfm_cmd_tab[cmd].cmd_argsize;
      getsize   = pfm_cmd_tab[cmd].cmd_getsize;
      cmd_flags = pfm_cmd_tab[cmd].cmd_flags;

      if (unlikely(func == NULL)) {
            DPRINT(("invalid cmd=%d\n", cmd));
            return -EINVAL;
      }

      DPRINT(("cmd=%s idx=%d narg=0x%x argsz=%lu count=%d\n",
            PFM_CMD_NAME(cmd),
            cmd,
            narg,
            base_sz,
            count));

      /*
       * check if number of arguments matches what the command expects
       */
      if (unlikely((narg == PFM_CMD_ARG_MANY && count <= 0) || (narg > 0 && narg != count)))
            return -EINVAL;

restart_args:
      sz = xtra_sz + base_sz*count;
      /*
       * limit abuse to min page size
       */
      if (unlikely(sz > PFM_MAX_ARGSIZE)) {
            printk(KERN_ERR "perfmon: [%d] argument too big %lu\n", task_pid_nr(current), sz);
            return -E2BIG;
      }

      /*
       * allocate default-sized argument buffer
       */
      if (likely(count && args_k == NULL)) {
            args_k = kmalloc(PFM_MAX_ARGSIZE, GFP_KERNEL);
            if (args_k == NULL) return -ENOMEM;
      }

      ret = -EFAULT;

      /*
       * copy arguments
       *
       * assume sz = 0 for command without parameters
       */
      if (sz && copy_from_user(args_k, arg, sz)) {
            DPRINT(("cannot copy_from_user %lu bytes @%p\n", sz, arg));
            goto error_args;
      }

      /*
       * check if command supports extra parameters
       */
      if (completed_args == 0 && getsize) {
            /*
             * get extra parameters size (based on main argument)
             */
            ret = (*getsize)(args_k, &xtra_sz);
            if (ret) goto error_args;

            completed_args = 1;

            DPRINT(("restart_args sz=%lu xtra_sz=%lu\n", sz, xtra_sz));

            /* retry if necessary */
            if (likely(xtra_sz)) goto restart_args;
      }

      if (unlikely((cmd_flags & PFM_CMD_FD) == 0)) goto skip_fd;

      ret = -EBADF;

      file = fget(fd);
      if (unlikely(file == NULL)) {
            DPRINT(("invalid fd %d\n", fd));
            goto error_args;
      }
      if (unlikely(PFM_IS_FILE(file) == 0)) {
            DPRINT(("fd %d not related to perfmon\n", fd));
            goto error_args;
      }

      ctx = (pfm_context_t *)file->private_data;
      if (unlikely(ctx == NULL)) {
            DPRINT(("no context for fd %d\n", fd));
            goto error_args;
      }
      prefetch(&ctx->ctx_state);

      PROTECT_CTX(ctx, flags);

      /*
       * check task is stopped
       */
      ret = pfm_check_task_state(ctx, cmd, flags);
      if (unlikely(ret)) goto abort_locked;

skip_fd:
      ret = (*func)(ctx, args_k, count, task_pt_regs(current));

      call_made = 1;

abort_locked:
      if (likely(ctx)) {
            DPRINT(("context unlocked\n"));
            UNPROTECT_CTX(ctx, flags);
      }

      /* copy argument back to user, if needed */
      if (call_made && PFM_CMD_RW_ARG(cmd) && copy_to_user(arg, args_k, base_sz*count)) ret = -EFAULT;

error_args:
      if (file)
            fput(file);

      kfree(args_k);

      DPRINT(("cmd=%s ret=%ld\n", PFM_CMD_NAME(cmd), ret));

      return ret;
}

static void
pfm_resume_after_ovfl(pfm_context_t *ctx, unsigned long ovfl_regs, struct pt_regs *regs)
{
      pfm_buffer_fmt_t *fmt = ctx->ctx_buf_fmt;
      pfm_ovfl_ctrl_t rst_ctrl;
      int state;
      int ret = 0;

      state = ctx->ctx_state;
      /*
       * Unlock sampling buffer and reset index atomically
       * XXX: not really needed when blocking
       */
      if (CTX_HAS_SMPL(ctx)) {

            rst_ctrl.bits.mask_monitoring = 0;
            rst_ctrl.bits.reset_ovfl_pmds = 0;

            if (state == PFM_CTX_LOADED)
                  ret = pfm_buf_fmt_restart_active(fmt, current, &rst_ctrl, ctx->ctx_smpl_hdr, regs);
            else
                  ret = pfm_buf_fmt_restart(fmt, current, &rst_ctrl, ctx->ctx_smpl_hdr, regs);
      } else {
            rst_ctrl.bits.mask_monitoring = 0;
            rst_ctrl.bits.reset_ovfl_pmds = 1;
      }

      if (ret == 0) {
            if (rst_ctrl.bits.reset_ovfl_pmds) {
                  pfm_reset_regs(ctx, &ovfl_regs, PFM_PMD_LONG_RESET);
            }
            if (rst_ctrl.bits.mask_monitoring == 0) {
                  DPRINT(("resuming monitoring\n"));
                  if (ctx->ctx_state == PFM_CTX_MASKED) pfm_restore_monitoring(current);
            } else {
                  DPRINT(("stopping monitoring\n"));
                  //pfm_stop_monitoring(current, regs);
            }
            ctx->ctx_state = PFM_CTX_LOADED;
      }
}

/*
 * context MUST BE LOCKED when calling
 * can only be called for current
 */
static void
pfm_context_force_terminate(pfm_context_t *ctx, struct pt_regs *regs)
{
      int ret;

      DPRINT(("entering for [%d]\n", task_pid_nr(current)));

      ret = pfm_context_unload(ctx, NULL, 0, regs);
      if (ret) {
            printk(KERN_ERR "pfm_context_force_terminate: [%d] unloaded failed with %d\n", task_pid_nr(current), ret);
      }

      /*
       * and wakeup controlling task, indicating we are now disconnected
       */
      wake_up_interruptible(&ctx->ctx_zombieq);

      /*
       * given that context is still locked, the controlling
       * task will only get access when we return from
       * pfm_handle_work().
       */
}

static int pfm_ovfl_notify_user(pfm_context_t *ctx, unsigned long ovfl_pmds);
 /*
  * pfm_handle_work() can be called with interrupts enabled
  * (TIF_NEED_RESCHED) or disabled. The down_interruptible
  * call may sleep, therefore we must re-enable interrupts
  * to avoid deadlocks. It is safe to do so because this function
  * is called ONLY when returning to user level (PUStk=1), in which case
  * there is no risk of kernel stack overflow due to deep
  * interrupt nesting.
  */
void
pfm_handle_work(void)
{
      pfm_context_t *ctx;
      struct pt_regs *regs;
      unsigned long flags, dummy_flags;
      unsigned long ovfl_regs;
      unsigned int reason;
      int ret;

      ctx = PFM_GET_CTX(current);
      if (ctx == NULL) {
            printk(KERN_ERR "perfmon: [%d] has no PFM context\n", task_pid_nr(current));
            return;
      }

      PROTECT_CTX(ctx, flags);

      PFM_SET_WORK_PENDING(current, 0);

      pfm_clear_task_notify();

      regs = task_pt_regs(current);

      /*
       * extract reason for being here and clear
       */
      reason = ctx->ctx_fl_trap_reason;
      ctx->ctx_fl_trap_reason = PFM_TRAP_REASON_NONE;
      ovfl_regs = ctx->ctx_ovfl_regs[0];

      DPRINT(("reason=%d state=%d\n", reason, ctx->ctx_state));

      /*
       * must be done before we check for simple-reset mode
       */
      if (ctx->ctx_fl_going_zombie || ctx->ctx_state == PFM_CTX_ZOMBIE) goto do_zombie;


      //if (CTX_OVFL_NOBLOCK(ctx)) goto skip_blocking;
      if (reason == PFM_TRAP_REASON_RESET) goto skip_blocking;

      /*
       * restore interrupt mask to what it was on entry.
       * Could be enabled/diasbled.
       */
      UNPROTECT_CTX(ctx, flags);

      /*
       * force interrupt enable because of down_interruptible()
       */
      local_irq_enable();

      DPRINT(("before block sleeping\n"));

      /*
       * may go through without blocking on SMP systems
       * if restart has been received already by the time we call down()
       */
      ret = wait_for_completion_interruptible(&ctx->ctx_restart_done);

      DPRINT(("after block sleeping ret=%d\n", ret));

      /*
       * lock context and mask interrupts again
       * We save flags into a dummy because we may have
       * altered interrupts mask compared to entry in this
       * function.
       */
      PROTECT_CTX(ctx, dummy_flags);

      /*
       * we need to read the ovfl_regs only after wake-up
       * because we may have had pfm_write_pmds() in between
       * and that can changed PMD values and therefore 
       * ovfl_regs is reset for these new PMD values.
       */
      ovfl_regs = ctx->ctx_ovfl_regs[0];

      if (ctx->ctx_fl_going_zombie) {
do_zombie:
            DPRINT(("context is zombie, bailing out\n"));
            pfm_context_force_terminate(ctx, regs);
            goto nothing_to_do;
      }
      /*
       * in case of interruption of down() we don't restart anything
       */
      if (ret < 0) goto nothing_to_do;

skip_blocking:
      pfm_resume_after_ovfl(ctx, ovfl_regs, regs);
      ctx->ctx_ovfl_regs[0] = 0UL;

nothing_to_do:
      /*
       * restore flags as they were upon entry
       */
      UNPROTECT_CTX(ctx, flags);
}

static int
pfm_notify_user(pfm_context_t *ctx, pfm_msg_t *msg)
{
      if (ctx->ctx_state == PFM_CTX_ZOMBIE) {
            DPRINT(("ignoring overflow notification, owner is zombie\n"));
            return 0;
      }

      DPRINT(("waking up somebody\n"));

      if (msg) wake_up_interruptible(&ctx->ctx_msgq_wait);

      /*
       * safe, we are not in intr handler, nor in ctxsw when
       * we come here
       */
      kill_fasync (&ctx->ctx_async_queue, SIGIO, POLL_IN);

      return 0;
}

static int
pfm_ovfl_notify_user(pfm_context_t *ctx, unsigned long ovfl_pmds)
{
      pfm_msg_t *msg = NULL;

      if (ctx->ctx_fl_no_msg == 0) {
            msg = pfm_get_new_msg(ctx);
            if (msg == NULL) {
                  printk(KERN_ERR "perfmon: pfm_ovfl_notify_user no more notification msgs\n");
                  return -1;
            }

            msg->pfm_ovfl_msg.msg_type         = PFM_MSG_OVFL;
            msg->pfm_ovfl_msg.msg_ctx_fd       = ctx->ctx_fd;
            msg->pfm_ovfl_msg.msg_active_set   = 0;
            msg->pfm_ovfl_msg.msg_ovfl_pmds[0] = ovfl_pmds;
            msg->pfm_ovfl_msg.msg_ovfl_pmds[1] = 0UL;
            msg->pfm_ovfl_msg.msg_ovfl_pmds[2] = 0UL;
            msg->pfm_ovfl_msg.msg_ovfl_pmds[3] = 0UL;
            msg->pfm_ovfl_msg.msg_tstamp       = 0UL;
      }

      DPRINT(("ovfl msg: msg=%p no_msg=%d fd=%d ovfl_pmds=0x%lx\n",
            msg,
            ctx->ctx_fl_no_msg,
            ctx->ctx_fd,
            ovfl_pmds));

      return pfm_notify_user(ctx, msg);
}

static int
pfm_end_notify_user(pfm_context_t *ctx)
{
      pfm_msg_t *msg;

      msg = pfm_get_new_msg(ctx);
      if (msg == NULL) {
            printk(KERN_ERR "perfmon: pfm_end_notify_user no more notification msgs\n");
            return -1;
      }
      /* no leak */
      memset(msg, 0, sizeof(*msg));

      msg->pfm_end_msg.msg_type    = PFM_MSG_END;
      msg->pfm_end_msg.msg_ctx_fd  = ctx->ctx_fd;
      msg->pfm_ovfl_msg.msg_tstamp = 0UL;

      DPRINT(("end msg: msg=%p no_msg=%d ctx_fd=%d\n",
            msg,
            ctx->ctx_fl_no_msg,
            ctx->ctx_fd));

      return pfm_notify_user(ctx, msg);
}

/*
 * main overflow processing routine.
 * it can be called from the interrupt path or explicitly during the context switch code
 */
static void
pfm_overflow_handler(struct task_struct *task, pfm_context_t *ctx, u64 pmc0, struct pt_regs *regs)
{
      pfm_ovfl_arg_t *ovfl_arg;
      unsigned long mask;
      unsigned long old_val, ovfl_val, new_val;
      unsigned long ovfl_notify = 0UL, ovfl_pmds = 0UL, smpl_pmds = 0UL, reset_pmds;
      unsigned long tstamp;
      pfm_ovfl_ctrl_t   ovfl_ctrl;
      unsigned int i, has_smpl;
      int must_notify = 0;

      if (unlikely(ctx->ctx_state == PFM_CTX_ZOMBIE)) goto stop_monitoring;

      /*
       * sanity test. Should never happen
       */
      if (unlikely((pmc0 & 0x1) == 0)) goto sanity_check;

      tstamp   = ia64_get_itc();
      mask     = pmc0 >> PMU_FIRST_COUNTER;
      ovfl_val = pmu_conf->ovfl_val;
      has_smpl = CTX_HAS_SMPL(ctx);

      DPRINT_ovfl(("pmc0=0x%lx pid=%d iip=0x%lx, %s "
                 "used_pmds=0x%lx\n",
                  pmc0,
                  task ? task_pid_nr(task): -1,
                  (regs ? regs->cr_iip : 0),
                  CTX_OVFL_NOBLOCK(ctx) ? "nonblocking" : "blocking",
                  ctx->ctx_used_pmds[0]));


      /*
       * first we update the virtual counters
       * assume there was a prior ia64_srlz_d() issued
       */
      for (i = PMU_FIRST_COUNTER; mask ; i++, mask >>= 1) {

            /* skip pmd which did not overflow */
            if ((mask & 0x1) == 0) continue;

            /*
             * Note that the pmd is not necessarily 0 at this point as qualified events
             * may have happened before the PMU was frozen. The residual count is not
             * taken into consideration here but will be with any read of the pmd via
             * pfm_read_pmds().
             */
            old_val              = new_val = ctx->ctx_pmds[i].val;
            new_val             += 1 + ovfl_val;
            ctx->ctx_pmds[i].val = new_val;

            /*
             * check for overflow condition
             */
            if (likely(old_val > new_val)) {
                  ovfl_pmds |= 1UL << i;
                  if (PMC_OVFL_NOTIFY(ctx, i)) ovfl_notify |= 1UL << i;
            }

            DPRINT_ovfl(("ctx_pmd[%d].val=0x%lx old_val=0x%lx pmd=0x%lx ovfl_pmds=0x%lx ovfl_notify=0x%lx\n",
                  i,
                  new_val,
                  old_val,
                  ia64_get_pmd(i) & ovfl_val,
                  ovfl_pmds,
                  ovfl_notify));
      }

      /*
       * there was no 64-bit overflow, nothing else to do
       */
      if (ovfl_pmds == 0UL) return;

      /* 
       * reset all control bits
       */
      ovfl_ctrl.val = 0;
      reset_pmds    = 0UL;

      /*
       * if a sampling format module exists, then we "cache" the overflow by 
       * calling the module's handler() routine.
       */
      if (has_smpl) {
            unsigned long start_cycles, end_cycles;
            unsigned long pmd_mask;
            int j, k, ret = 0;
            int this_cpu = smp_processor_id();

            pmd_mask = ovfl_pmds >> PMU_FIRST_COUNTER;
            ovfl_arg = &ctx->ctx_ovfl_arg;

            prefetch(ctx->ctx_smpl_hdr);

            for(i=PMU_FIRST_COUNTER; pmd_mask && ret == 0; i++, pmd_mask >>=1) {

                  mask = 1UL << i;

                  if ((pmd_mask & 0x1) == 0) continue;

                  ovfl_arg->ovfl_pmd      = (unsigned char )i;
                  ovfl_arg->ovfl_notify   = ovfl_notify & mask ? 1 : 0;
                  ovfl_arg->active_set    = 0;
                  ovfl_arg->ovfl_ctrl.val = 0; /* module must fill in all fields */
                  ovfl_arg->smpl_pmds[0]  = smpl_pmds = ctx->ctx_pmds[i].smpl_pmds[0];

                  ovfl_arg->pmd_value      = ctx->ctx_pmds[i].val;
                  ovfl_arg->pmd_last_reset = ctx->ctx_pmds[i].lval;
                  ovfl_arg->pmd_eventid    = ctx->ctx_pmds[i].eventid;

                  /*
                   * copy values of pmds of interest. Sampling format may copy them
                   * into sampling buffer.
                   */
                  if (smpl_pmds) {
                        for(j=0, k=0; smpl_pmds; j++, smpl_pmds >>=1) {
                              if ((smpl_pmds & 0x1) == 0) continue;
                              ovfl_arg->smpl_pmds_values[k++] = PMD_IS_COUNTING(j) ?  pfm_read_soft_counter(ctx, j) : ia64_get_pmd(j);
                              DPRINT_ovfl(("smpl_pmd[%d]=pmd%u=0x%lx\n", k-1, j, ovfl_arg->smpl_pmds_values[k-1]));
                        }
                  }

                  pfm_stats[this_cpu].pfm_smpl_handler_calls++;

                  start_cycles = ia64_get_itc();

                  /*
                   * call custom buffer format record (handler) routine
                   */
                  ret = (*ctx->ctx_buf_fmt->fmt_handler)(task, ctx->ctx_smpl_hdr, ovfl_arg, regs, tstamp);

                  end_cycles = ia64_get_itc();

                  /*
                   * For those controls, we take the union because they have
                   * an all or nothing behavior.
                   */
                  ovfl_ctrl.bits.notify_user     |= ovfl_arg->ovfl_ctrl.bits.notify_user;
                  ovfl_ctrl.bits.block_task      |= ovfl_arg->ovfl_ctrl.bits.block_task;
                  ovfl_ctrl.bits.mask_monitoring |= ovfl_arg->ovfl_ctrl.bits.mask_monitoring;
                  /*
                   * build the bitmask of pmds to reset now
                   */
                  if (ovfl_arg->ovfl_ctrl.bits.reset_ovfl_pmds) reset_pmds |= mask;

                  pfm_stats[this_cpu].pfm_smpl_handler_cycles += end_cycles - start_cycles;
            }
            /*
             * when the module cannot handle the rest of the overflows, we abort right here
             */
            if (ret && pmd_mask) {
                  DPRINT(("handler aborts leftover ovfl_pmds=0x%lx\n",
                        pmd_mask<<PMU_FIRST_COUNTER));
            }
            /*
             * remove the pmds we reset now from the set of pmds to reset in pfm_restart()
             */
            ovfl_pmds &= ~reset_pmds;
      } else {
            /*
             * when no sampling module is used, then the default
             * is to notify on overflow if requested by user
             */
            ovfl_ctrl.bits.notify_user     = ovfl_notify ? 1 : 0;
            ovfl_ctrl.bits.block_task      = ovfl_notify ? 1 : 0;
            ovfl_ctrl.bits.mask_monitoring = ovfl_notify ? 1 : 0; /* XXX: change for saturation */
            ovfl_ctrl.bits.reset_ovfl_pmds = ovfl_notify ? 0 : 1;
            /*
             * if needed, we reset all overflowed pmds
             */
            if (ovfl_notify == 0) reset_pmds = ovfl_pmds;
      }

      DPRINT_ovfl(("ovfl_pmds=0x%lx reset_pmds=0x%lx\n", ovfl_pmds, reset_pmds));

      /*
       * reset the requested PMD registers using the short reset values
       */
      if (reset_pmds) {
            unsigned long bm = reset_pmds;
            pfm_reset_regs(ctx, &bm, PFM_PMD_SHORT_RESET);
      }

      if (ovfl_notify && ovfl_ctrl.bits.notify_user) {
            /*
             * keep track of what to reset when unblocking
             */
            ctx->ctx_ovfl_regs[0] = ovfl_pmds;

            /*
             * check for blocking context 
             */
            if (CTX_OVFL_NOBLOCK(ctx) == 0 && ovfl_ctrl.bits.block_task) {

                  ctx->ctx_fl_trap_reason = PFM_TRAP_REASON_BLOCK;

                  /*
                   * set the perfmon specific checking pending work for the task
                   */
                  PFM_SET_WORK_PENDING(task, 1);

                  /*
                   * when coming from ctxsw, current still points to the
                   * previous task, therefore we must work with task and not current.
                   */
                  pfm_set_task_notify(task);
            }
            /*
             * defer until state is changed (shorten spin window). the context is locked
             * anyway, so the signal receiver would come spin for nothing.
             */
            must_notify = 1;
      }

      DPRINT_ovfl(("owner [%d] pending=%ld reason=%u ovfl_pmds=0x%lx ovfl_notify=0x%lx masked=%d\n",
                  GET_PMU_OWNER() ? task_pid_nr(GET_PMU_OWNER()) : -1,
                  PFM_GET_WORK_PENDING(task),
                  ctx->ctx_fl_trap_reason,
                  ovfl_pmds,
                  ovfl_notify,
                  ovfl_ctrl.bits.mask_monitoring ? 1 : 0));
      /*
       * in case monitoring must be stopped, we toggle the psr bits
       */
      if (ovfl_ctrl.bits.mask_monitoring) {
            pfm_mask_monitoring(task);
            ctx->ctx_state = PFM_CTX_MASKED;
            ctx->ctx_fl_can_restart = 1;
      }

      /*
       * send notification now
       */
      if (must_notify) pfm_ovfl_notify_user(ctx, ovfl_notify);

      return;

sanity_check:
      printk(KERN_ERR "perfmon: CPU%d overflow handler [%d] pmc0=0x%lx\n",
                  smp_processor_id(),
                  task ? task_pid_nr(task) : -1,
                  pmc0);
      return;

stop_monitoring:
      /*
       * in SMP, zombie context is never restored but reclaimed in pfm_load_regs().
       * Moreover, zombies are also reclaimed in pfm_save_regs(). Therefore we can
       * come here as zombie only if the task is the current task. In which case, we
       * can access the PMU  hardware directly.
       *
       * Note that zombies do have PM_VALID set. So here we do the minimal.
       *
       * In case the context was zombified it could not be reclaimed at the time
       * the monitoring program exited. At this point, the PMU reservation has been
       * returned, the sampiing buffer has been freed. We must convert this call
       * into a spurious interrupt. However, we must also avoid infinite overflows
       * by stopping monitoring for this task. We can only come here for a per-task
       * context. All we need to do is to stop monitoring using the psr bits which
       * are always task private. By re-enabling secure montioring, we ensure that
       * the monitored task will not be able to re-activate monitoring.
       * The task will eventually be context switched out, at which point the context
       * will be reclaimed (that includes releasing ownership of the PMU).
       *
       * So there might be a window of time where the number of per-task session is zero
       * yet one PMU might have a owner and get at most one overflow interrupt for a zombie
       * context. This is safe because if a per-task session comes in, it will push this one
       * out and by the virtue on pfm_save_regs(), this one will disappear. If a system wide
       * session is force on that CPU, given that we use task pinning, pfm_save_regs() will
       * also push our zombie context out.
       *
       * Overall pretty hairy stuff....
       */
      DPRINT(("ctx is zombie for [%d], converted to spurious\n", task ? task_pid_nr(task): -1));
      pfm_clear_psr_up();
      ia64_psr(regs)->up = 0;
      ia64_psr(regs)->sp = 1;
      return;
}

static int
pfm_do_interrupt_handler(int irq, void *arg, struct pt_regs *regs)
{
      struct task_struct *task;
      pfm_context_t *ctx;
      unsigned long flags;
      u64 pmc0;
      int this_cpu = smp_processor_id();
      int retval = 0;

      pfm_stats[this_cpu].pfm_ovfl_intr_count++;

      /*
       * srlz.d done before arriving here
       */
      pmc0 = ia64_get_pmc(0);

      task = GET_PMU_OWNER();
      ctx  = GET_PMU_CTX();

      /*
       * if we have some pending bits set
       * assumes : if any PMC0.bit[63-1] is set, then PMC0.fr = 1
       */
      if (PMC0_HAS_OVFL(pmc0) && task) {
            /*
             * we assume that pmc0.fr is always set here
             */

            /* sanity check */
            if (!ctx) goto report_spurious1;

            if (ctx->ctx_fl_system == 0 && (task->thread.flags & IA64_THREAD_PM_VALID) == 0) 
                  goto report_spurious2;

            PROTECT_CTX_NOPRINT(ctx, flags);

            pfm_overflow_handler(task, ctx, pmc0, regs);

            UNPROTECT_CTX_NOPRINT(ctx, flags);

      } else {
            pfm_stats[this_cpu].pfm_spurious_ovfl_intr_count++;
            retval = -1;
      }
      /*
       * keep it unfrozen at all times
       */
      pfm_unfreeze_pmu();

      return retval;

report_spurious1:
      printk(KERN_INFO "perfmon: spurious overflow interrupt on CPU%d: process %d has no PFM context\n",
            this_cpu, task_pid_nr(task));
      pfm_unfreeze_pmu();
      return -1;
report_spurious2:
      printk(KERN_INFO "perfmon: spurious overflow interrupt on CPU%d: process %d, invalid flag\n", 
            this_cpu, 
            task_pid_nr(task));
      pfm_unfreeze_pmu();
      return -1;
}

static irqreturn_t
pfm_interrupt_handler(int irq, void *arg)
{
      unsigned long start_cycles, total_cycles;
      unsigned long min, max;
      int this_cpu;
      int ret;
      struct pt_regs *regs = get_irq_regs();

      this_cpu = get_cpu();
      if (likely(!pfm_alt_intr_handler)) {
            min = pfm_stats[this_cpu].pfm_ovfl_intr_cycles_min;
            max = pfm_stats[this_cpu].pfm_ovfl_intr_cycles_max;

            start_cycles = ia64_get_itc();

            ret = pfm_do_interrupt_handler(irq, arg, regs);

            total_cycles = ia64_get_itc();

            /*
             * don't measure spurious interrupts
             */
            if (likely(ret == 0)) {
                  total_cycles -= start_cycles;

                  if (total_cycles < min) pfm_stats[this_cpu].pfm_ovfl_intr_cycles_min = total_cycles;
                  if (total_cycles > max) pfm_stats[this_cpu].pfm_ovfl_intr_cycles_max = total_cycles;

                  pfm_stats[this_cpu].pfm_ovfl_intr_cycles += total_cycles;
            }
      }
      else {
            (*pfm_alt_intr_handler->handler)(irq, arg, regs);
      }

      put_cpu_no_resched();
      return IRQ_HANDLED;
}

/*
 * /proc/perfmon interface, for debug only
 */

#define PFM_PROC_SHOW_HEADER  ((void *)NR_CPUS+1)

static void *
pfm_proc_start(struct seq_file *m, loff_t *pos)
{
      if (*pos == 0) {
            return PFM_PROC_SHOW_HEADER;
      }

      while (*pos <= NR_CPUS) {
            if (cpu_online(*pos - 1)) {
                  return (void *)*pos;
            }
            ++*pos;
      }
      return NULL;
}

static void *
pfm_proc_next(struct seq_file *m, void *v, loff_t *pos)
{
      ++*pos;
      return pfm_proc_start(m, pos);
}

static void
pfm_proc_stop(struct seq_file *m, void *v)
{
}

static void
pfm_proc_show_header(struct seq_file *m)
{
      struct list_head * pos;
      pfm_buffer_fmt_t * entry;
      unsigned long flags;

      seq_printf(m,
            "perfmon version           : %u.%u\n"
            "model                     : %s\n"
            "fastctxsw                 : %s\n"
            "expert mode               : %s\n"
            "ovfl_mask                 : 0x%lx\n"
            "PMU flags                 : 0x%x\n",
            PFM_VERSION_MAJ, PFM_VERSION_MIN,
            pmu_conf->pmu_name,
            pfm_sysctl.fastctxsw > 0 ? "Yes": "No",
            pfm_sysctl.expert_mode > 0 ? "Yes": "No",
            pmu_conf->ovfl_val,
            pmu_conf->flags);

      LOCK_PFS(flags);

      seq_printf(m,
            "proc_sessions             : %u\n"
            "sys_sessions              : %u\n"
            "sys_use_dbregs            : %u\n"
            "ptrace_use_dbregs         : %u\n",
            pfm_sessions.pfs_task_sessions,
            pfm_sessions.pfs_sys_sessions,
            pfm_sessions.pfs_sys_use_dbregs,
            pfm_sessions.pfs_ptrace_use_dbregs);

      UNLOCK_PFS(flags);

      spin_lock(&pfm_buffer_fmt_lock);

      list_for_each(pos, &pfm_buffer_fmt_list) {
            entry = list_entry(pos, pfm_buffer_fmt_t, fmt_list);
            seq_printf(m, "format                    : %02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x %s\n",
                  entry->fmt_uuid[0],
                  entry->fmt_uuid[1],
                  entry->fmt_uuid[2],
                  entry->fmt_uuid[3],
                  entry->fmt_uuid[4],
                  entry->fmt_uuid[5],
                  entry->fmt_uuid[6],
                  entry->fmt_uuid[7],
                  entry->fmt_uuid[8],
                  entry->fmt_uuid[9],
                  entry->fmt_uuid[10],
                  entry->fmt_uuid[11],
                  entry->fmt_uuid[12],
                  entry->fmt_uuid[13],
                  entry->fmt_uuid[14],
                  entry->fmt_uuid[15],
                  entry->fmt_name);
      }
      spin_unlock(&pfm_buffer_fmt_lock);

}

static int
pfm_proc_show(struct seq_file *m, void *v)
{
      unsigned long psr;
      unsigned int i;
      int cpu;

      if (v == PFM_PROC_SHOW_HEADER) {
            pfm_proc_show_header(m);
            return 0;
      }

      /* show info for CPU (v - 1) */

      cpu = (long)v - 1;
      seq_printf(m,
            "CPU%-2d overflow intrs      : %lu\n"
            "CPU%-2d overflow cycles     : %lu\n"
            "CPU%-2d overflow min        : %lu\n"
            "CPU%-2d overflow max        : %lu\n"
            "CPU%-2d smpl handler calls  : %lu\n"
            "CPU%-2d smpl handler cycles : %lu\n"
            "CPU%-2d spurious intrs      : %lu\n"
            "CPU%-2d replay   intrs      : %lu\n"
            "CPU%-2d syst_wide           : %d\n"
            "CPU%-2d dcr_pp              : %d\n"
            "CPU%-2d exclude idle        : %d\n"
            "CPU%-2d owner               : %d\n"
            "CPU%-2d context             : %p\n"
            "CPU%-2d activations         : %lu\n",
            cpu, pfm_stats[cpu].pfm_ovfl_intr_count,
            cpu, pfm_stats[cpu].pfm_ovfl_intr_cycles,
            cpu, pfm_stats[cpu].pfm_ovfl_intr_cycles_min,
            cpu, pfm_stats[cpu].pfm_ovfl_intr_cycles_max,
            cpu, pfm_stats[cpu].pfm_smpl_handler_calls,
            cpu, pfm_stats[cpu].pfm_smpl_handler_cycles,
            cpu, pfm_stats[cpu].pfm_spurious_ovfl_intr_count,
            cpu, pfm_stats[cpu].pfm_replay_ovfl_intr_count,
            cpu, pfm_get_cpu_data(pfm_syst_info, cpu) & PFM_CPUINFO_SYST_WIDE ? 1 : 0,
            cpu, pfm_get_cpu_data(pfm_syst_info, cpu) & PFM_CPUINFO_DCR_PP ? 1 : 0,
            cpu, pfm_get_cpu_data(pfm_syst_info, cpu) & PFM_CPUINFO_EXCL_IDLE ? 1 : 0,
            cpu, pfm_get_cpu_data(pmu_owner, cpu) ? pfm_get_cpu_data(pmu_owner, cpu)->pid: -1,
            cpu, pfm_get_cpu_data(pmu_ctx, cpu),
            cpu, pfm_get_cpu_data(pmu_activation_number, cpu));

      if (num_online_cpus() == 1 && pfm_sysctl.debug > 0) {

            psr = pfm_get_psr();

            ia64_srlz_d();

            seq_printf(m, 
                  "CPU%-2d psr                 : 0x%lx\n"
                  "CPU%-2d pmc0                : 0x%lx\n", 
                  cpu, psr,
                  cpu, ia64_get_pmc(0));

            for (i=0; PMC_IS_LAST(i) == 0;  i++) {
                  if (PMC_IS_COUNTING(i) == 0) continue;
                  seq_printf(m, 
                        "CPU%-2d pmc%u                : 0x%lx\n"
                        "CPU%-2d pmd%u                : 0x%lx\n", 
                        cpu, i, ia64_get_pmc(i),
                        cpu, i, ia64_get_pmd(i));
            }
      }
      return 0;
}

struct seq_operations pfm_seq_ops = {
      .start =    pfm_proc_start,
      .next =           pfm_proc_next,
      .stop =           pfm_proc_stop,
      .show =           pfm_proc_show
};

static int
pfm_proc_open(struct inode *inode, struct file *file)
{
      return seq_open(file, &pfm_seq_ops);
}


/*
 * we come here as soon as local_cpu_data->pfm_syst_wide is set. this happens
 * during pfm_enable() hence before pfm_start(). We cannot assume monitoring
 * is active or inactive based on mode. We must rely on the value in
 * local_cpu_data->pfm_syst_info
 */
void
pfm_syst_wide_update_task(struct task_struct *task, unsigned long info, int is_ctxswin)
{
      struct pt_regs *regs;
      unsigned long dcr;
      unsigned long dcr_pp;

      dcr_pp = info & PFM_CPUINFO_DCR_PP ? 1 : 0;

      /*
       * pid 0 is guaranteed to be the idle task. There is one such task with pid 0
       * on every CPU, so we can rely on the pid to identify the idle task.
       */
      if ((info & PFM_CPUINFO_EXCL_IDLE) == 0 || task->pid) {
            regs = task_pt_regs(task);
            ia64_psr(regs)->pp = is_ctxswin ? dcr_pp : 0;
            return;
      }
      /*
       * if monitoring has started
       */
      if (dcr_pp) {
            dcr = ia64_getreg(_IA64_REG_CR_DCR);
            /*
             * context switching in?
             */
            if (is_ctxswin) {
                  /* mask monitoring for the idle task */
                  ia64_setreg(_IA64_REG_CR_DCR, dcr & ~IA64_DCR_PP);
                  pfm_clear_psr_pp();
                  ia64_srlz_i();
                  return;
            }
            /*
             * context switching out
             * restore monitoring for next task
             *
             * Due to inlining this odd if-then-else construction generates
             * better code.
             */
            ia64_setreg(_IA64_REG_CR_DCR, dcr |IA64_DCR_PP);
            pfm_set_psr_pp();
            ia64_srlz_i();
      }
}

#ifdef CONFIG_SMP

static void
pfm_force_cleanup(pfm_context_t *ctx, struct pt_regs *regs)
{
      struct task_struct *task = ctx->ctx_task;

      ia64_psr(regs)->up = 0;
      ia64_psr(regs)->sp = 1;

      if (GET_PMU_OWNER() == task) {
            DPRINT(("cleared ownership for [%d]\n",
                              task_pid_nr(ctx->ctx_task)));
            SET_PMU_OWNER(NULL, NULL);
      }

      /*
       * disconnect the task from the context and vice-versa
       */
      PFM_SET_WORK_PENDING(task, 0);

      task->thread.pfm_context  = NULL;
      task->thread.flags       &= ~IA64_THREAD_PM_VALID;

      DPRINT(("force cleanup for [%d]\n",  task_pid_nr(task)));
}


/*
 * in 2.6, interrupts are masked when we come here and the runqueue lock is held
 */
void
pfm_save_regs(struct task_struct *task)
{
      pfm_context_t *ctx;
      unsigned long flags;
      u64 psr;


      ctx = PFM_GET_CTX(task);
      if (ctx == NULL) return;

      /*
       * we always come here with interrupts ALREADY disabled by
       * the scheduler. So we simply need to protect against concurrent
       * access, not CPU concurrency.
       */
      flags = pfm_protect_ctx_ctxsw(ctx);

      if (ctx->ctx_state == PFM_CTX_ZOMBIE) {
            struct pt_regs *regs = task_pt_regs(task);

            pfm_clear_psr_up();

            pfm_force_cleanup(ctx, regs);

            BUG_ON(ctx->ctx_smpl_hdr);

            pfm_unprotect_ctx_ctxsw(ctx, flags);

            pfm_context_free(ctx);
            return;
      }

      /*
       * save current PSR: needed because we modify it
       */
      ia64_srlz_d();
      psr = pfm_get_psr();

      BUG_ON(psr & (IA64_PSR_I));

      /*
       * stop monitoring:
       * This is the last instruction which may generate an overflow
       *
       * We do not need to set psr.sp because, it is irrelevant in kernel.
       * It will be restored from ipsr when going back to user level
       */
      pfm_clear_psr_up();

      /*
       * keep a copy of psr.up (for reload)
       */
      ctx->ctx_saved_psr_up = psr & IA64_PSR_UP;

      /*
       * release ownership of this PMU.
       * PM interrupts are masked, so nothing
       * can happen.
       */
      SET_PMU_OWNER(NULL, NULL);

      /*
       * we systematically save the PMD as we have no
       * guarantee we will be schedule at that same
       * CPU again.
       */
      pfm_save_pmds(ctx->th_pmds, ctx->ctx_used_pmds[0]);

      /*
       * save pmc0 ia64_srlz_d() done in pfm_save_pmds()
       * we will need it on the restore path to check
       * for pending overflow.
       */
      ctx->th_pmcs[0] = ia64_get_pmc(0);

      /*
       * unfreeze PMU if had pending overflows
       */
      if (ctx->th_pmcs[0] & ~0x1UL) pfm_unfreeze_pmu();

      /*
       * finally, allow context access.
       * interrupts will still be masked after this call.
       */
      pfm_unprotect_ctx_ctxsw(ctx, flags);
}

#else /* !CONFIG_SMP */
void
pfm_save_regs(struct task_struct *task)
{
      pfm_context_t *ctx;
      u64 psr;

      ctx = PFM_GET_CTX(task);
      if (ctx == NULL) return;

      /*
       * save current PSR: needed because we modify it
       */
      psr = pfm_get_psr();

      BUG_ON(psr & (IA64_PSR_I));

      /*
       * stop monitoring:
       * This is the last instruction which may generate an overflow
       *
       * We do not need to set psr.sp because, it is irrelevant in kernel.
       * It will be restored from ipsr when going back to user level
       */
      pfm_clear_psr_up();

      /*
       * keep a copy of psr.up (for reload)
       */
      ctx->ctx_saved_psr_up = psr & IA64_PSR_UP;
}

static void
pfm_lazy_save_regs (struct task_struct *task)
{
      pfm_context_t *ctx;
      unsigned long flags;

      { u64 psr  = pfm_get_psr();
        BUG_ON(psr & IA64_PSR_UP);
      }

      ctx = PFM_GET_CTX(task);

      /*
       * we need to mask PMU overflow here to
       * make sure that we maintain pmc0 until
       * we save it. overflow interrupts are
       * treated as spurious if there is no
       * owner.
       *
       * XXX: I don't think this is necessary
       */
      PROTECT_CTX(ctx,flags);

      /*
       * release ownership of this PMU.
       * must be done before we save the registers.
       *
       * after this call any PMU interrupt is treated
       * as spurious.
       */
      SET_PMU_OWNER(NULL, NULL);

      /*
       * save all the pmds we use
       */
      pfm_save_pmds(ctx->th_pmds, ctx->ctx_used_pmds[0]);

      /*
       * save pmc0 ia64_srlz_d() done in pfm_save_pmds()
       * it is needed to check for pended overflow
       * on the restore path
       */
      ctx->th_pmcs[0] = ia64_get_pmc(0);

      /*
       * unfreeze PMU if had pending overflows
       */
      if (ctx->th_pmcs[0] & ~0x1UL) pfm_unfreeze_pmu();

      /*
       * now get can unmask PMU interrupts, they will
       * be treated as purely spurious and we will not
       * lose any information
       */
      UNPROTECT_CTX(ctx,flags);
}
#endif /* CONFIG_SMP */

#ifdef CONFIG_SMP
/*
 * in 2.6, interrupts are masked when we come here and the runqueue lock is held
 */
void
pfm_load_regs (struct task_struct *task)
{
      pfm_context_t *ctx;
      unsigned long pmc_mask = 0UL, pmd_mask = 0UL;
      unsigned long flags;
      u64 psr, psr_up;
      int need_irq_resend;

      ctx = PFM_GET_CTX(task);
      if (unlikely(ctx == NULL)) return;

      BUG_ON(GET_PMU_OWNER());

      /*
       * possible on unload
       */
      if (unlikely((task->thread.flags & IA64_THREAD_PM_VALID) == 0)) return;

      /*
       * we always come here with interrupts ALREADY disabled by
       * the scheduler. So we simply need to protect against concurrent
       * access, not CPU concurrency.
       */
      flags = pfm_protect_ctx_ctxsw(ctx);
      psr   = pfm_get_psr();

      need_irq_resend = pmu_conf->flags & PFM_PMU_IRQ_RESEND;

      BUG_ON(psr & (IA64_PSR_UP|IA64_PSR_PP));
      BUG_ON(psr & IA64_PSR_I);

      if (unlikely(ctx->ctx_state == PFM_CTX_ZOMBIE)) {
            struct pt_regs *regs = task_pt_regs(task);

            BUG_ON(ctx->ctx_smpl_hdr);

            pfm_force_cleanup(ctx, regs);

            pfm_unprotect_ctx_ctxsw(ctx, flags);

            /*
             * this one (kmalloc'ed) is fine with interrupts disabled
             */
            pfm_context_free(ctx);

            return;
      }

      /*
       * we restore ALL the debug registers to avoid picking up
       * stale state.
       */
      if (ctx->ctx_fl_using_dbreg) {
            pfm_restore_ibrs(ctx->ctx_ibrs, pmu_conf->num_ibrs);
            pfm_restore_dbrs(ctx->ctx_dbrs, pmu_conf->num_dbrs);
      }
      /*
       * retrieve saved psr.up
       */
      psr_up = ctx->ctx_saved_psr_up;

      /*
       * if we were the last user of the PMU on that CPU,
       * then nothing to do except restore psr
       */
      if (GET_LAST_CPU(ctx) == smp_processor_id() && ctx->ctx_last_activation == GET_ACTIVATION()) {

            /*
             * retrieve partial reload masks (due to user modifications)
             */
            pmc_mask = ctx->ctx_reload_pmcs[0];
            pmd_mask = ctx->ctx_reload_pmds[0];

      } else {
            /*
             * To avoid leaking information to the user level when psr.sp=0,
             * we must reload ALL implemented pmds (even the ones we don't use).
             * In the kernel we only allow PFM_READ_PMDS on registers which
             * we initialized or requested (sampling) so there is no risk there.
             */
            pmd_mask = pfm_sysctl.fastctxsw ?  ctx->ctx_used_pmds[0] : ctx->ctx_all_pmds[0];

            /*
             * ALL accessible PMCs are systematically reloaded, unused registers
             * get their default (from pfm_reset_pmu_state()) values to avoid picking
             * up stale configuration.
             *
             * PMC0 is never in the mask. It is always restored separately.
             */
            pmc_mask = ctx->ctx_all_pmcs[0];
      }
      /*
       * when context is MASKED, we will restore PMC with plm=0
       * and PMD with stale information, but that's ok, nothing
       * will be captured.
       *
       * XXX: optimize here
       */
      if (pmd_mask) pfm_restore_pmds(ctx->th_pmds, pmd_mask);
      if (pmc_mask) pfm_restore_pmcs(ctx->th_pmcs, pmc_mask);

      /*
       * check for pending overflow at the time the state
       * was saved.
       */
      if (unlikely(PMC0_HAS_OVFL(ctx->th_pmcs[0]))) {
            /*
             * reload pmc0 with the overflow information
             * On McKinley PMU, this will trigger a PMU interrupt
             */
            ia64_set_pmc(0, ctx->th_pmcs[0]);
            ia64_srlz_d();
            ctx->th_pmcs[0] = 0UL;

            /*
             * will replay the PMU interrupt
             */
            if (need_irq_resend) ia64_resend_irq(IA64_PERFMON_VECTOR);

            pfm_stats[smp_processor_id()].pfm_replay_ovfl_intr_count++;
      }

      /*
       * we just did a reload, so we reset the partial reload fields
       */
      ctx->ctx_reload_pmcs[0] = 0UL;
      ctx->ctx_reload_pmds[0] = 0UL;

      SET_LAST_CPU(ctx, smp_processor_id());

      /*
       * dump activation value for this PMU
       */
      INC_ACTIVATION();
      /*
       * record current activation for this context
       */
      SET_ACTIVATION(ctx);

      /*
       * establish new ownership. 
       */
      SET_PMU_OWNER(task, ctx);

      /*
       * restore the psr.up bit. measurement
       * is active again.
       * no PMU interrupt can happen at this point
       * because we still have interrupts disabled.
       */
      if (likely(psr_up)) pfm_set_psr_up();

      /*
       * allow concurrent access to context
       */
      pfm_unprotect_ctx_ctxsw(ctx, flags);
}
#else /*  !CONFIG_SMP */
/*
 * reload PMU state for UP kernels
 * in 2.5 we come here with interrupts disabled
 */
void
pfm_load_regs (struct task_struct *task)
{
      pfm_context_t *ctx;
      struct task_struct *owner;
      unsigned long pmd_mask, pmc_mask;
      u64 psr, psr_up;
      int need_irq_resend;

      owner = GET_PMU_OWNER();
      ctx   = PFM_GET_CTX(task);
      psr   = pfm_get_psr();

      BUG_ON(psr & (IA64_PSR_UP|IA64_PSR_PP));
      BUG_ON(psr & IA64_PSR_I);

      /*
       * we restore ALL the debug registers to avoid picking up
       * stale state.
       *
       * This must be done even when the task is still the owner
       * as the registers may have been modified via ptrace()
       * (not perfmon) by the previous task.
       */
      if (ctx->ctx_fl_using_dbreg) {
            pfm_restore_ibrs(ctx->ctx_ibrs, pmu_conf->num_ibrs);
            pfm_restore_dbrs(ctx->ctx_dbrs, pmu_conf->num_dbrs);
      }

      /*
       * retrieved saved psr.up
       */
      psr_up = ctx->ctx_saved_psr_up;
      need_irq_resend = pmu_conf->flags & PFM_PMU_IRQ_RESEND;

      /*
       * short path, our state is still there, just
       * need to restore psr and we go
       *
       * we do not touch either PMC nor PMD. the psr is not touched
       * by the overflow_handler. So we are safe w.r.t. to interrupt
       * concurrency even without interrupt masking.
       */
      if (likely(owner == task)) {
            if (likely(psr_up)) pfm_set_psr_up();
            return;
      }

      /*
       * someone else is still using the PMU, first push it out and
       * then we'll be able to install our stuff !
       *
       * Upon return, there will be no owner for the current PMU
       */
      if (owner) pfm_lazy_save_regs(owner);

      /*
       * To avoid leaking information to the user level when psr.sp=0,
       * we must reload ALL implemented pmds (even the ones we don't use).
       * In the kernel we only allow PFM_READ_PMDS on registers which
       * we initialized or requested (sampling) so there is no risk there.
       */
      pmd_mask = pfm_sysctl.fastctxsw ?  ctx->ctx_used_pmds[0] : ctx->ctx_all_pmds[0];

      /*
       * ALL accessible PMCs are systematically reloaded, unused registers
       * get their default (from pfm_reset_pmu_state()) values to avoid picking
       * up stale configuration.
       *
       * PMC0 is never in the mask. It is always restored separately
       */
      pmc_mask = ctx->ctx_all_pmcs[0];

      pfm_restore_pmds(ctx->th_pmds, pmd_mask);
      pfm_restore_pmcs(ctx->th_pmcs, pmc_mask);

      /*
       * check for pending overflow at the time the state
       * was saved.
       */
      if (unlikely(PMC0_HAS_OVFL(ctx->th_pmcs[0]))) {
            /*
             * reload pmc0 with the overflow information
             * On McKinley PMU, this will trigger a PMU interrupt
             */
            ia64_set_pmc(0, ctx->th_pmcs[0]);
            ia64_srlz_d();

            ctx->th_pmcs[0] = 0UL;

            /*
             * will replay the PMU interrupt
             */
            if (need_irq_resend) ia64_resend_irq(IA64_PERFMON_VECTOR);

            pfm_stats[smp_processor_id()].pfm_replay_ovfl_intr_count++;
      }

      /*
       * establish new ownership. 
       */
      SET_PMU_OWNER(task, ctx);

      /*
       * restore the psr.up bit. measurement
       * is active again.
       * no PMU interrupt can happen at this point
       * because we still have interrupts disabled.
       */
      if (likely(psr_up)) pfm_set_psr_up();
}
#endif /* CONFIG_SMP */

/*
 * this function assumes monitoring is stopped
 */
static void
pfm_flush_pmds(struct task_struct *task, pfm_context_t *ctx)
{
      u64 pmc0;
      unsigned long mask2, val, pmd_val, ovfl_val;
      int i, can_access_pmu = 0;
      int is_self;

      /*
       * is the caller the task being monitored (or which initiated the
       * session for system wide measurements)
       */
      is_self = ctx->ctx_task == task ? 1 : 0;

      /*
       * can access PMU is task is the owner of the PMU state on the current CPU
       * or if we are running on the CPU bound to the context in system-wide mode
       * (that is not necessarily the task the context is attached to in this mode).
       * In system-wide we always have can_access_pmu true because a task running on an
       * invalid processor is flagged earlier in the call stack (see pfm_stop).
       */
      can_access_pmu = (GET_PMU_OWNER() == task) || (ctx->ctx_fl_system && ctx->ctx_cpu == smp_processor_id());
      if (can_access_pmu) {
            /*
             * Mark the PMU as not owned
             * This will cause the interrupt handler to do nothing in case an overflow
             * interrupt was in-flight
             * This also guarantees that pmc0 will contain the final state
             * It virtually gives us full control on overflow processing from that point
             * on.
             */
            SET_PMU_OWNER(NULL, NULL);
            DPRINT(("releasing ownership\n"));

            /*
             * read current overflow status:
             *
             * we are guaranteed to read the final stable state
             */
            ia64_srlz_d();
            pmc0 = ia64_get_pmc(0); /* slow */

            /*
             * reset freeze bit, overflow status information destroyed
             */
            pfm_unfreeze_pmu();
      } else {
            pmc0 = ctx->th_pmcs[0];
            /*
             * clear whatever overflow status bits there were
             */
            ctx->th_pmcs[0] = 0;
      }
      ovfl_val = pmu_conf->ovfl_val;
      /*
       * we save all the used pmds
       * we take care of overflows for counting PMDs
       *
       * XXX: sampling situation is not taken into account here
       */
      mask2 = ctx->ctx_used_pmds[0];

      DPRINT(("is_self=%d ovfl_val=0x%lx mask2=0x%lx\n", is_self, ovfl_val, mask2));

      for (i = 0; mask2; i++, mask2>>=1) {

            /* skip non used pmds */
            if ((mask2 & 0x1) == 0) continue;

            /*
             * can access PMU always true in system wide mode
             */
            val = pmd_val = can_access_pmu ? ia64_get_pmd(i) : ctx->th_pmds[i];

            if (PMD_IS_COUNTING(i)) {
                  DPRINT(("[%d] pmd[%d] ctx_pmd=0x%lx hw_pmd=0x%lx\n",
                        task_pid_nr(task),
                        i,
                        ctx->ctx_pmds[i].val,
                        val & ovfl_val));

                  /*
                   * we rebuild the full 64 bit value of the counter
                   */
                  val = ctx->ctx_pmds[i].val + (val & ovfl_val);

                  /*
                   * now everything is in ctx_pmds[] and we need
                   * to clear the saved context from save_regs() such that
                   * pfm_read_pmds() gets the correct value
                   */
                  pmd_val = 0UL;

                  /*
                   * take care of overflow inline
                   */
                  if (pmc0 & (1UL << i)) {
                        val += 1 + ovfl_val;
                        DPRINT(("[%d] pmd[%d] overflowed\n", task_pid_nr(task), i));
                  }
            }

            DPRINT(("[%d] ctx_pmd[%d]=0x%lx  pmd_val=0x%lx\n", task_pid_nr(task), i, val, pmd_val));

            if (is_self) ctx->th_pmds[i] = pmd_val;

            ctx->ctx_pmds[i].val = val;
      }
}

static struct irqaction perfmon_irqaction = {
      .handler = pfm_interrupt_handler,
      .flags   = IRQF_DISABLED,
      .name    = "perfmon"
};

static void
pfm_alt_save_pmu_state(void *data)
{
      struct pt_regs *regs;

      regs = task_pt_regs(current);

      DPRINT(("called\n"));

      /*
       * should not be necessary but
       * let's take not risk
       */
      pfm_clear_psr_up();
      pfm_clear_psr_pp();
      ia64_psr(regs)->pp = 0;

      /*
       * This call is required
       * May cause a spurious interrupt on some processors
       */
      pfm_freeze_pmu();

      ia64_srlz_d();
}

void
pfm_alt_restore_pmu_state(void *data)
{
      struct pt_regs *regs;

      regs = task_pt_regs(current);

      DPRINT(("called\n"));

      /*
       * put PMU back in state expected
       * by perfmon
       */
      pfm_clear_psr_up();
      pfm_clear_psr_pp();
      ia64_psr(regs)->pp = 0;

      /*
       * perfmon runs with PMU unfrozen at all times
       */
      pfm_unfreeze_pmu();

      ia64_srlz_d();
}

int
pfm_install_alt_pmu_interrupt(pfm_intr_handler_desc_t *hdl)
{
      int ret, i;
      int reserve_cpu;

      /* some sanity checks */
      if (hdl == NULL || hdl->handler == NULL) return -EINVAL;

      /* do the easy test first */
      if (pfm_alt_intr_handler) return -EBUSY;

      /* one at a time in the install or remove, just fail the others */
      if (!spin_trylock(&pfm_alt_install_check)) {
            return -EBUSY;
      }

      /* reserve our session */
      for_each_online_cpu(reserve_cpu) {
            ret = pfm_reserve_session(NULL, 1, reserve_cpu);
            if (ret) goto cleanup_reserve;
      }

      /* save the current system wide pmu states */
      ret = on_each_cpu(pfm_alt_save_pmu_state, NULL, 0, 1);
      if (ret) {
            DPRINT(("on_each_cpu() failed: %d\n", ret));
            goto cleanup_reserve;
      }

      /* officially change to the alternate interrupt handler */
      pfm_alt_intr_handler = hdl;

      spin_unlock(&pfm_alt_install_check);

      return 0;

cleanup_reserve:
      for_each_online_cpu(i) {
            /* don't unreserve more than we reserved */
            if (i >= reserve_cpu) break;

            pfm_unreserve_session(NULL, 1, i);
      }

      spin_unlock(&pfm_alt_install_check);

      return ret;
}
EXPORT_SYMBOL_GPL(pfm_install_alt_pmu_interrupt);

int
pfm_remove_alt_pmu_interrupt(pfm_intr_handler_desc_t *hdl)
{
      int i;
      int ret;

      if (hdl == NULL) return -EINVAL;

      /* cannot remove someone else's handler! */
      if (pfm_alt_intr_handler != hdl) return -EINVAL;

      /* one at a time in the install or remove, just fail the others */
      if (!spin_trylock(&pfm_alt_install_check)) {
            return -EBUSY;
      }

      pfm_alt_intr_handler = NULL;

      ret = on_each_cpu(pfm_alt_restore_pmu_state, NULL, 0, 1);
      if (ret) {
            DPRINT(("on_each_cpu() failed: %d\n", ret));
      }

      for_each_online_cpu(i) {
            pfm_unreserve_session(NULL, 1, i);
      }

      spin_unlock(&pfm_alt_install_check);

      return 0;
}
EXPORT_SYMBOL_GPL(pfm_remove_alt_pmu_interrupt);

/*
 * perfmon initialization routine, called from the initcall() table
 */
static int init_pfm_fs(void);

static int __init
pfm_probe_pmu(void)
{
      pmu_config_t **p;
      int family;

      family = local_cpu_data->family;
      p      = pmu_confs;

      while(*p) {
            if ((*p)->probe) {
                  if ((*p)->probe() == 0) goto found;
            } else if ((*p)->pmu_family == family || (*p)->pmu_family == 0xff) {
                  goto found;
            }
            p++;
      }
      return -1;
found:
      pmu_conf = *p;
      return 0;
}

static const struct file_operations pfm_proc_fops = {
      .open       = pfm_proc_open,
      .read       = seq_read,
      .llseek           = seq_lseek,
      .release    = seq_release,
};

int __init
pfm_init(void)
{
      unsigned int n, n_counters, i;

      printk("perfmon: version %u.%u IRQ %u\n",
            PFM_VERSION_MAJ,
            PFM_VERSION_MIN,
            IA64_PERFMON_VECTOR);

      if (pfm_probe_pmu()) {
            printk(KERN_INFO "perfmon: disabled, there is no support for processor family %d\n", 
                        local_cpu_data->family);
            return -ENODEV;
      }

      /*
       * compute the number of implemented PMD/PMC from the
       * description tables
       */
      n = 0;
      for (i=0; PMC_IS_LAST(i) == 0;  i++) {
            if (PMC_IS_IMPL(i) == 0) continue;
            pmu_conf->impl_pmcs[i>>6] |= 1UL << (i&63);
            n++;
      }
      pmu_conf->num_pmcs = n;

      n = 0; n_counters = 0;
      for (i=0; PMD_IS_LAST(i) == 0;  i++) {
            if (PMD_IS_IMPL(i) == 0) continue;
            pmu_conf->impl_pmds[i>>6] |= 1UL << (i&63);
            n++;
            if (PMD_IS_COUNTING(i)) n_counters++;
      }
      pmu_conf->num_pmds      = n;
      pmu_conf->num_counters  = n_counters;

      /*
       * sanity checks on the number of debug registers
       */
      if (pmu_conf->use_rr_dbregs) {
            if (pmu_conf->num_ibrs > IA64_NUM_DBG_REGS) {
                  printk(KERN_INFO "perfmon: unsupported number of code debug registers (%u)\n", pmu_conf->num_ibrs);
                  pmu_conf = NULL;
                  return -1;
            }
            if (pmu_conf->num_dbrs > IA64_NUM_DBG_REGS) {
                  printk(KERN_INFO "perfmon: unsupported number of data debug registers (%u)\n", pmu_conf->num_ibrs);
                  pmu_conf = NULL;
                  return -1;
            }
      }

      printk("perfmon: %s PMU detected, %u PMCs, %u PMDs, %u counters (%lu bits)\n",
             pmu_conf->pmu_name,
             pmu_conf->num_pmcs,
             pmu_conf->num_pmds,
             pmu_conf->num_counters,
             ffz(pmu_conf->ovfl_val));

      /* sanity check */
      if (pmu_conf->num_pmds >= PFM_NUM_PMD_REGS || pmu_conf->num_pmcs >= PFM_NUM_PMC_REGS) {
            printk(KERN_ERR "perfmon: not enough pmc/pmd, perfmon disabled\n");
            pmu_conf = NULL;
            return -1;
      }

      /*
       * create /proc/perfmon (mostly for debugging purposes)
       */
      perfmon_dir = create_proc_entry("perfmon", S_IRUGO, NULL);
      if (perfmon_dir == NULL) {
            printk(KERN_ERR "perfmon: cannot create /proc entry, perfmon disabled\n");
            pmu_conf = NULL;
            return -1;
      }
      /*
       * install customized file operations for /proc/perfmon entry
       */
      perfmon_dir->proc_fops = &pfm_proc_fops;

      /*
       * create /proc/sys/kernel/perfmon (for debugging purposes)
       */
      pfm_sysctl_header = register_sysctl_table(pfm_sysctl_root);

      /*
       * initialize all our spinlocks
       */
      spin_lock_init(&pfm_sessions.pfs_lock);
      spin_lock_init(&pfm_buffer_fmt_lock);

      init_pfm_fs();

      for(i=0; i < NR_CPUS; i++) pfm_stats[i].pfm_ovfl_intr_cycles_min = ~0UL;

      return 0;
}

__initcall(pfm_init);

/*
 * this function is called before pfm_init()
 */
void
pfm_init_percpu (void)
{
      static int first_time=1;
      /*
       * make sure no measurement is active
       * (may inherit programmed PMCs from EFI).
       */
      pfm_clear_psr_pp();
      pfm_clear_psr_up();

      /*
       * we run with the PMU not frozen at all times
       */
      pfm_unfreeze_pmu();

      if (first_time) {
            register_percpu_irq(IA64_PERFMON_VECTOR, &perfmon_irqaction);
            first_time=0;
      }

      ia64_setreg(_IA64_REG_CR_PMV, IA64_PERFMON_VECTOR);
      ia64_srlz_d();
}

/*
 * used for debug purposes only
 */
void
dump_pmu_state(const char *from)
{
      struct task_struct *task;
      struct pt_regs *regs;
      pfm_context_t *ctx;
      unsigned long psr, dcr, info, flags;
      int i, this_cpu;

      local_irq_save(flags);

      this_cpu = smp_processor_id();
      regs     = task_pt_regs(current);
      info     = PFM_CPUINFO_GET();
      dcr      = ia64_getreg(_IA64_REG_CR_DCR);

      if (info == 0 && ia64_psr(regs)->pp == 0 && (dcr & IA64_DCR_PP) == 0) {
            local_irq_restore(flags);
            return;
      }

      printk("CPU%d from %s() current [%d] iip=0x%lx %s\n", 
            this_cpu, 
            from, 
            task_pid_nr(current),
            regs->cr_iip,
            current->comm);

      task = GET_PMU_OWNER();
      ctx  = GET_PMU_CTX();

      printk("->CPU%d owner [%d] ctx=%p\n", this_cpu, task ? task_pid_nr(task) : -1, ctx);

      psr = pfm_get_psr();

      printk("->CPU%d pmc0=0x%lx psr.pp=%d psr.up=%d dcr.pp=%d syst_info=0x%lx user_psr.up=%d user_psr.pp=%d\n", 
            this_cpu,
            ia64_get_pmc(0),
            psr & IA64_PSR_PP ? 1 : 0,
            psr & IA64_PSR_UP ? 1 : 0,
            dcr & IA64_DCR_PP ? 1 : 0,
            info,
            ia64_psr(regs)->up,
            ia64_psr(regs)->pp);

      ia64_psr(regs)->up = 0;
      ia64_psr(regs)->pp = 0;

      for (i=1; PMC_IS_LAST(i) == 0; i++) {
            if (PMC_IS_IMPL(i) == 0) continue;
            printk("->CPU%d pmc[%d]=0x%lx thread_pmc[%d]=0x%lx\n", this_cpu, i, ia64_get_pmc(i), i, ctx->th_pmcs[i]);
      }

      for (i=1; PMD_IS_LAST(i) == 0; i++) {
            if (PMD_IS_IMPL(i) == 0) continue;
            printk("->CPU%d pmd[%d]=0x%lx thread_pmd[%d]=0x%lx\n", this_cpu, i, ia64_get_pmd(i), i, ctx->th_pmds[i]);
      }

      if (ctx) {
            printk("->CPU%d ctx_state=%d vaddr=%p addr=%p fd=%d ctx_task=[%d] saved_psr_up=0x%lx\n",
                        this_cpu,
                        ctx->ctx_state,
                        ctx->ctx_smpl_vaddr,
                        ctx->ctx_smpl_hdr,
                        ctx->ctx_msgq_head,
                        ctx->ctx_msgq_tail,
                        ctx->ctx_saved_psr_up);
      }
      local_irq_restore(flags);
}

/*
 * called from process.c:copy_thread(). task is new child.
 */
void
pfm_inherit(struct task_struct *task, struct pt_regs *regs)
{
      struct thread_struct *thread;

      DPRINT(("perfmon: pfm_inherit clearing state for [%d]\n", task_pid_nr(task)));

      thread = &task->thread;

      /*
       * cut links inherited from parent (current)
       */
      thread->pfm_context = NULL;

      PFM_SET_WORK_PENDING(task, 0);

      /*
       * the psr bits are already set properly in copy_threads()
       */
}
#else  /* !CONFIG_PERFMON */
asmlinkage long
sys_perfmonctl (int fd, int cmd, void *arg, int count)
{
      return -ENOSYS;
}
#endif /* CONFIG_PERFMON */

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