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kgdb.c

/*
 * PowerPC backend to the KGDB stub.
 *
 * 1998 (c) Michael AK Tesch (tesch@cs.wisc.edu)
 * Copyright (C) 2003 Timesys Corporation.
 * Copyright (C) 2004-2006 MontaVista Software, Inc.
 * PPC64 Mods (C) 2005 Frank Rowand (frowand@mvista.com)
 * PPC32 support restored by Vitaly Wool <vwool@ru.mvista.com> and
 * Sergei Shtylyov <sshtylyov@ru.mvista.com>
 * Copyright (C) 2007-2008 Wind River Systems, Inc.
 *
 * This file is licensed under the terms of the GNU General Public License
 * version 2. This program as licensed "as is" without any warranty of any
 * kind, whether express or implied.
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/kgdb.h>
#include <linux/smp.h>
#include <linux/signal.h>
#include <linux/ptrace.h>
#include <asm/current.h>
#include <asm/processor.h>
#include <asm/machdep.h>

/*
 * This table contains the mapping between PowerPC hardware trap types, and
 * signals, which are primarily what GDB understands.  GDB and the kernel
 * don't always agree on values, so we use constants taken from gdb-6.2.
 */
static struct hard_trap_info
{
      unsigned int tt;        /* Trap type code for powerpc */
      unsigned char signo;          /* Signal that we map this trap into */
} hard_trap_info[] = {
      { 0x0100, 0x02 /* SIGINT */  },           /* system reset */
      { 0x0200, 0x0b /* SIGSEGV */ },           /* machine check */
      { 0x0300, 0x0b /* SIGSEGV */ },           /* data access */
      { 0x0400, 0x0b /* SIGSEGV */ },           /* instruction access */
      { 0x0500, 0x02 /* SIGINT */  },           /* external interrupt */
      { 0x0600, 0x0a /* SIGBUS */  },           /* alignment */
      { 0x0700, 0x05 /* SIGTRAP */ },           /* program check */
      { 0x0800, 0x08 /* SIGFPE */  },           /* fp unavailable */
      { 0x0900, 0x0e /* SIGALRM */ },           /* decrementer */
      { 0x0c00, 0x14 /* SIGCHLD */ },           /* system call */
#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
      { 0x2002, 0x05 /* SIGTRAP */ },           /* debug */
#if defined(CONFIG_FSL_BOOKE)
      { 0x2010, 0x08 /* SIGFPE */  },           /* spe unavailable */
      { 0x2020, 0x08 /* SIGFPE */  },           /* spe unavailable */
      { 0x2030, 0x08 /* SIGFPE */  },           /* spe fp data */
      { 0x2040, 0x08 /* SIGFPE */  },           /* spe fp data */
      { 0x2050, 0x08 /* SIGFPE */  },           /* spe fp round */
      { 0x2060, 0x0e /* SIGILL */  },           /* performace monitor */
      { 0x2900, 0x08 /* SIGFPE */  },           /* apu unavailable */
      { 0x3100, 0x0e /* SIGALRM */ },           /* fixed interval timer */
      { 0x3200, 0x02 /* SIGINT */  },     /* watchdog */
#else /* ! CONFIG_FSL_BOOKE */
      { 0x1000, 0x0e /* SIGALRM */ },           /* prog interval timer */
      { 0x1010, 0x0e /* SIGALRM */ },           /* fixed interval timer */
      { 0x1020, 0x02 /* SIGINT */  },     /* watchdog */
      { 0x2010, 0x08 /* SIGFPE */  },           /* fp unavailable */
      { 0x2020, 0x08 /* SIGFPE */  },           /* ap unavailable */
#endif
#else /* ! (defined(CONFIG_40x) || defined(CONFIG_BOOKE)) */
      { 0x0d00, 0x05 /* SIGTRAP */ },           /* single-step */
#if defined(CONFIG_8xx)
      { 0x1000, 0x04 /* SIGILL */  },           /* software emulation */
#else /* ! CONFIG_8xx */
      { 0x0f00, 0x04 /* SIGILL */  },           /* performance monitor */
      { 0x0f20, 0x08 /* SIGFPE */  },           /* altivec unavailable */
      { 0x1300, 0x05 /* SIGTRAP */ },     /* instruction address break */
#if defined(CONFIG_PPC64)
      { 0x1200, 0x05 /* SIGILL */  },           /* system error */
      { 0x1500, 0x04 /* SIGILL */  },           /* soft patch */
      { 0x1600, 0x04 /* SIGILL */  },           /* maintenance */
      { 0x1700, 0x08 /* SIGFPE */  },           /* altivec assist */
      { 0x1800, 0x04 /* SIGILL */  },           /* thermal */
#else /* ! CONFIG_PPC64 */
      { 0x1400, 0x02 /* SIGINT */  },           /* SMI */
      { 0x1600, 0x08 /* SIGFPE */  },           /* altivec assist */
      { 0x1700, 0x04 /* SIGILL */  },           /* TAU */
      { 0x2000, 0x05 /* SIGTRAP */ },           /* run mode */
#endif
#endif
#endif
      { 0x0000, 0x00 }              /* Must be last */
};

static int computeSignal(unsigned int tt)
{
      struct hard_trap_info *ht;

      for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
            if (ht->tt == tt)
                  return ht->signo;

      return SIGHUP;          /* default for things we don't know about */
}

static int kgdb_call_nmi_hook(struct pt_regs *regs)
{
      kgdb_nmicallback(raw_smp_processor_id(), regs);
      return 0;
}

#ifdef CONFIG_SMP
void kgdb_roundup_cpus(unsigned long flags)
{
      smp_send_debugger_break(MSG_ALL_BUT_SELF);
}
#endif

/* KGDB functions to use existing PowerPC64 hooks. */
static int kgdb_debugger(struct pt_regs *regs)
{
      return kgdb_handle_exception(0, computeSignal(TRAP(regs)), 0, regs);
}

static int kgdb_handle_breakpoint(struct pt_regs *regs)
{
      if (user_mode(regs))
            return 0;

      if (kgdb_handle_exception(0, SIGTRAP, 0, regs) != 0)
            return 0;

      if (*(u32 *) (regs->nip) == *(u32 *) (&arch_kgdb_ops.gdb_bpt_instr))
            regs->nip += 4;

      return 1;
}

static int kgdb_singlestep(struct pt_regs *regs)
{
      struct thread_info *thread_info, *exception_thread_info;

      if (user_mode(regs))
            return 0;

      /*
       * On Book E and perhaps other processsors, singlestep is handled on
       * the critical exception stack.  This causes current_thread_info()
       * to fail, since it it locates the thread_info by masking off
       * the low bits of the current stack pointer.  We work around
       * this issue by copying the thread_info from the kernel stack
       * before calling kgdb_handle_exception, and copying it back
       * afterwards.  On most processors the copy is avoided since
       * exception_thread_info == thread_info.
       */
      thread_info = (struct thread_info *)(regs->gpr[1] & ~(THREAD_SIZE-1));
      exception_thread_info = current_thread_info();

      if (thread_info != exception_thread_info)
            memcpy(exception_thread_info, thread_info, sizeof *thread_info);

      kgdb_handle_exception(0, SIGTRAP, 0, regs);

      if (thread_info != exception_thread_info)
            memcpy(thread_info, exception_thread_info, sizeof *thread_info);

      return 1;
}

static int kgdb_iabr_match(struct pt_regs *regs)
{
      if (user_mode(regs))
            return 0;

      if (kgdb_handle_exception(0, computeSignal(TRAP(regs)), 0, regs) != 0)
            return 0;
      return 1;
}

static int kgdb_dabr_match(struct pt_regs *regs)
{
      if (user_mode(regs))
            return 0;

      if (kgdb_handle_exception(0, computeSignal(TRAP(regs)), 0, regs) != 0)
            return 0;
      return 1;
}

#define PACK64(ptr, src) do { *(ptr++) = (src); } while (0)

#define PACK32(ptr, src) do {          \
      u32 *ptr32;                   \
      ptr32 = (u32 *)ptr;           \
      *(ptr32++) = (src);           \
      ptr = (unsigned long *)ptr32; \
      } while (0)


void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
{
      unsigned long *ptr = gdb_regs;
      int reg;

      memset(gdb_regs, 0, NUMREGBYTES);

      for (reg = 0; reg < 32; reg++)
            PACK64(ptr, regs->gpr[reg]);

#ifdef CONFIG_FSL_BOOKE
#ifdef CONFIG_SPE
      for (reg = 0; reg < 32; reg++)
            PACK64(ptr, current->thread.evr[reg]);
#else
      ptr += 32;
#endif
#else
      /* fp registers not used by kernel, leave zero */
      ptr += 32 * 8 / sizeof(long);
#endif

      PACK64(ptr, regs->nip);
      PACK64(ptr, regs->msr);
      PACK32(ptr, regs->ccr);
      PACK64(ptr, regs->link);
      PACK64(ptr, regs->ctr);
      PACK32(ptr, regs->xer);

      BUG_ON((unsigned long)ptr >
             (unsigned long)(((void *)gdb_regs) + NUMREGBYTES));
}

void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
{
      struct pt_regs *regs = (struct pt_regs *)(p->thread.ksp +
                                      STACK_FRAME_OVERHEAD);
      unsigned long *ptr = gdb_regs;
      int reg;

      memset(gdb_regs, 0, NUMREGBYTES);

      /* Regs GPR0-2 */
      for (reg = 0; reg < 3; reg++)
            PACK64(ptr, regs->gpr[reg]);

      /* Regs GPR3-13 are caller saved, not in regs->gpr[] */
      ptr += 11;

      /* Regs GPR14-31 */
      for (reg = 14; reg < 32; reg++)
            PACK64(ptr, regs->gpr[reg]);

#ifdef CONFIG_FSL_BOOKE
#ifdef CONFIG_SPE
      for (reg = 0; reg < 32; reg++)
            PACK64(ptr, p->thread.evr[reg]);
#else
      ptr += 32;
#endif
#else
      /* fp registers not used by kernel, leave zero */
      ptr += 32 * 8 / sizeof(long);
#endif

      PACK64(ptr, regs->nip);
      PACK64(ptr, regs->msr);
      PACK32(ptr, regs->ccr);
      PACK64(ptr, regs->link);
      PACK64(ptr, regs->ctr);
      PACK32(ptr, regs->xer);

      BUG_ON((unsigned long)ptr >
             (unsigned long)(((void *)gdb_regs) + NUMREGBYTES));
}

#define UNPACK64(dest, ptr) do { dest = *(ptr++); } while (0)

#define UNPACK32(dest, ptr) do {       \
      u32 *ptr32;                   \
      ptr32 = (u32 *)ptr;           \
      dest = *(ptr32++);            \
      ptr = (unsigned long *)ptr32; \
      } while (0)

void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
{
      unsigned long *ptr = gdb_regs;
      int reg;
#ifdef CONFIG_SPE
      union {
            u32 v32[2];
            u64 v64;
      } acc;
#endif

      for (reg = 0; reg < 32; reg++)
            UNPACK64(regs->gpr[reg], ptr);

#ifdef CONFIG_FSL_BOOKE
#ifdef CONFIG_SPE
      for (reg = 0; reg < 32; reg++)
            UNPACK64(current->thread.evr[reg], ptr);
#else
      ptr += 32;
#endif
#else
      /* fp registers not used by kernel, leave zero */
      ptr += 32 * 8 / sizeof(int);
#endif

      UNPACK64(regs->nip, ptr);
      UNPACK64(regs->msr, ptr);
      UNPACK32(regs->ccr, ptr);
      UNPACK64(regs->link, ptr);
      UNPACK64(regs->ctr, ptr);
      UNPACK32(regs->xer, ptr);

      BUG_ON((unsigned long)ptr >
             (unsigned long)(((void *)gdb_regs) + NUMREGBYTES));
}

/*
 * This function does PowerPC specific procesing for interfacing to gdb.
 */
int kgdb_arch_handle_exception(int vector, int signo, int err_code,
                         char *remcom_in_buffer, char *remcom_out_buffer,
                         struct pt_regs *linux_regs)
{
      char *ptr = &remcom_in_buffer[1];
      unsigned long addr;

      switch (remcom_in_buffer[0]) {
            /*
             * sAA..AA   Step one instruction from AA..AA
             * This will return an error to gdb ..
             */
      case 's':
      case 'c':
            /* handle the optional parameter */
            if (kgdb_hex2long(&ptr, &addr))
                  linux_regs->nip = addr;

            atomic_set(&kgdb_cpu_doing_single_step, -1);
            /* set the trace bit if we're stepping */
            if (remcom_in_buffer[0] == 's') {
#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
                  mtspr(SPRN_DBCR0,
                        mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
                  linux_regs->msr |= MSR_DE;
#else
                  linux_regs->msr |= MSR_SE;
#endif
                  kgdb_single_step = 1;
                  if (kgdb_contthread)
                        atomic_set(&kgdb_cpu_doing_single_step,
                                 raw_smp_processor_id());
            }
            return 0;
      }

      return -1;
}

/*
 * Global data
 */
struct kgdb_arch arch_kgdb_ops = {
      .gdb_bpt_instr = {0x7d, 0x82, 0x10, 0x08},
};

static int kgdb_not_implemented(struct pt_regs *regs)
{
      return 0;
}

static void *old__debugger_ipi;
static void *old__debugger;
static void *old__debugger_bpt;
static void *old__debugger_sstep;
static void *old__debugger_iabr_match;
static void *old__debugger_dabr_match;
static void *old__debugger_fault_handler;

int kgdb_arch_init(void)
{
      old__debugger_ipi = __debugger_ipi;
      old__debugger = __debugger;
      old__debugger_bpt = __debugger_bpt;
      old__debugger_sstep = __debugger_sstep;
      old__debugger_iabr_match = __debugger_iabr_match;
      old__debugger_dabr_match = __debugger_dabr_match;
      old__debugger_fault_handler = __debugger_fault_handler;

      __debugger_ipi = kgdb_call_nmi_hook;
      __debugger = kgdb_debugger;
      __debugger_bpt = kgdb_handle_breakpoint;
      __debugger_sstep = kgdb_singlestep;
      __debugger_iabr_match = kgdb_iabr_match;
      __debugger_dabr_match = kgdb_dabr_match;
      __debugger_fault_handler = kgdb_not_implemented;

      return 0;
}

void kgdb_arch_exit(void)
{
      __debugger_ipi = old__debugger_ipi;
      __debugger = old__debugger;
      __debugger_bpt = old__debugger_bpt;
      __debugger_sstep = old__debugger_sstep;
      __debugger_iabr_match = old__debugger_iabr_match;
      __debugger_dabr_match = old__debugger_dabr_match;
      __debugger_fault_handler = old__debugger_fault_handler;
}

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