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process.c

/*
 * arch/xtensa/kernel/process.c
 *
 * Xtensa Processor version.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2001 - 2005 Tensilica Inc.
 *
 * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
 * Chris Zankel <chris@zankel.net>
 * Marc Gauthier <marc@tensilica.com, marc@alumni.uwaterloo.ca>
 * Kevin Chea
 */

#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/elf.h>
#include <linux/init.h>
#include <linux/prctl.h>
#include <linux/init_task.h>
#include <linux/module.h>
#include <linux/mqueue.h>
#include <linux/fs.h>

#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/platform.h>
#include <asm/mmu.h>
#include <asm/irq.h>
#include <asm/atomic.h>
#include <asm/asm-offsets.h>
#include <asm/regs.h>

extern void ret_from_fork(void);

struct task_struct *current_set[NR_CPUS] = {&init_task, };

void (*pm_power_off)(void) = NULL;
EXPORT_SYMBOL(pm_power_off);


/*
 * Powermanagement idle function, if any is provided by the platform.
 */

void cpu_idle(void)
{
      local_irq_enable();

      /* endless idle loop with no priority at all */
      while (1) {
            while (!need_resched())
                  platform_idle();
            preempt_enable_no_resched();
            schedule();
            preempt_disable();
      }
}

/*
 * Free current thread data structures etc..
 */

void exit_thread(void)
{
}

void flush_thread(void)
{
}

/*
 * Copy thread.
 *
 * The stack layout for the new thread looks like this:
 *
 *    +------------------------+ <- sp in childregs (= tos)
 *    |       childregs        |
 *    +------------------------+ <- thread.sp = sp in dummy-frame
 *    |      dummy-frame       |    (saved in dummy-frame spill-area)
 *    +------------------------+
 *
 * We create a dummy frame to return to ret_from_fork:
 *   a0 points to ret_from_fork (simulating a call4)
 *   sp points to itself (thread.sp)
 *   a2, a3 are unused.
 *
 * Note: This is a pristine frame, so we don't need any spill region on top of
 *       childregs.
 */

int copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
            unsigned long unused,
                struct task_struct * p, struct pt_regs * regs)
{
      struct pt_regs *childregs;
      unsigned long tos;
      int user_mode = user_mode(regs);

      /* Set up new TSS. */
      tos = (unsigned long)task_stack_page(p) + THREAD_SIZE;
      if (user_mode)
            childregs = (struct pt_regs*)(tos - PT_USER_SIZE);
      else
            childregs = (struct pt_regs*)tos - 1;

      *childregs = *regs;

      /* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */
      *((int*)childregs - 3) = (unsigned long)childregs;
      *((int*)childregs - 4) = 0;

      childregs->areg[1] = tos;
      childregs->areg[2] = 0;
      p->set_child_tid = p->clear_child_tid = NULL;
      p->thread.ra = MAKE_RA_FOR_CALL((unsigned long)ret_from_fork, 0x1);
      p->thread.sp = (unsigned long)childregs;
      if (user_mode(regs)) {

            int len = childregs->wmask & ~0xf;
            childregs->areg[1] = usp;
            memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],
                   &regs->areg[XCHAL_NUM_AREGS - len/4], len);

            if (clone_flags & CLONE_SETTLS)
                  childregs->areg[2] = childregs->areg[6];

      } else {
            /* In kernel space, we start a new thread with a new stack. */
            childregs->wmask = 1;
      }
      return 0;
}


/*
 * These bracket the sleeping functions..
 */

unsigned long get_wchan(struct task_struct *p)
{
      unsigned long sp, pc;
      unsigned long stack_page = (unsigned long) task_stack_page(p);
      int count = 0;

      if (!p || p == current || p->state == TASK_RUNNING)
            return 0;

      sp = p->thread.sp;
      pc = MAKE_PC_FROM_RA(p->thread.ra, p->thread.sp);

      do {
            if (sp < stack_page + sizeof(struct task_struct) ||
                sp >= (stack_page + THREAD_SIZE) ||
                pc == 0)
                  return 0;
            if (!in_sched_functions(pc))
                  return pc;

            /* Stack layout: sp-4: ra, sp-3: sp' */

            pc = MAKE_PC_FROM_RA(*(unsigned long*)sp - 4, sp);
            sp = *(unsigned long *)sp - 3;
      } while (count++ < 16);
      return 0;
}

/*
 * do_copy_regs() gathers information from 'struct pt_regs' and
 * 'current->thread.areg[]' to fill in the xtensa_gregset_t
 * structure.
 *
 * xtensa_gregset_t and 'struct pt_regs' are vastly different formats
 * of processor registers.  Besides different ordering,
 * xtensa_gregset_t contains non-live register information that
 * 'struct pt_regs' does not.  Exception handling (primarily) uses
 * 'struct pt_regs'.  Core files and ptrace use xtensa_gregset_t.
 *
 */

void do_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs,
               struct task_struct *tsk)
{
      int i, n, wb_offset;

      elfregs->xchal_config_id0 = XCHAL_HW_CONFIGID0;
      elfregs->xchal_config_id1 = XCHAL_HW_CONFIGID1;

      __asm__ __volatile__ ("rsr  %0, 176\n" : "=a" (i));
      elfregs->cpux = i;
      __asm__ __volatile__ ("rsr  %0, 208\n" : "=a" (i));
      elfregs->cpuy = i;

      /* Note:  PS.EXCM is not set while user task is running; its
       * being set in regs->ps is for exception handling convenience.
       */

      elfregs->pc       = regs->pc;
      elfregs->ps       = (regs->ps & ~(1 << PS_EXCM_BIT));
      elfregs->exccause = regs->exccause;
      elfregs->excvaddr = regs->excvaddr;
      elfregs->windowbase     = regs->windowbase;
      elfregs->windowstart    = regs->windowstart;
      elfregs->lbeg           = regs->lbeg;
      elfregs->lend           = regs->lend;
      elfregs->lcount         = regs->lcount;
      elfregs->sar            = regs->sar;
      elfregs->syscall  = regs->syscall;

      /* Copy register file.
       * The layout looks like this:
       *
       * |  a0 ... a15  | Z ... Z |  arX ... arY  |
       *  current window  unused    saved frames
       */

      memset (elfregs->ar, 0, sizeof(elfregs->ar));

      wb_offset = regs->windowbase * 4;
      n = (regs->wmask&1)? 4 : (regs->wmask&2)? 8 : (regs->wmask&4)? 12 : 16;

      for (i = 0; i < n; i++)
            elfregs->ar[(wb_offset + i) % XCHAL_NUM_AREGS] = regs->areg[i];

      n = (regs->wmask >> 4) * 4;

      for (i = XCHAL_NUM_AREGS - n; n > 0; i++, n--)
            elfregs->ar[(wb_offset + i) % XCHAL_NUM_AREGS] = regs->areg[i];
}

void xtensa_elf_core_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs)
{
      do_copy_regs ((xtensa_gregset_t *)elfregs, regs, current);
}


/* The inverse of do_copy_regs().  No error or sanity checking. */

void do_restore_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs,
                  struct task_struct *tsk)
{
      int i, n, wb_offset;

      /* Note:  PS.EXCM is not set while user task is running; it
       * needs to be set in regs->ps is for exception handling convenience.
       */

      regs->pc          = elfregs->pc;
      regs->ps          = (elfregs->ps | (1 << PS_EXCM_BIT));
      regs->exccause          = elfregs->exccause;
      regs->excvaddr          = elfregs->excvaddr;
      regs->windowbase  = elfregs->windowbase;
      regs->windowstart = elfregs->windowstart;
      regs->lbeg        = elfregs->lbeg;
      regs->lend        = elfregs->lend;
      regs->lcount            = elfregs->lcount;
      regs->sar         = elfregs->sar;
      regs->syscall     = elfregs->syscall;

      /* Clear everything. */

      memset (regs->areg, 0, sizeof(regs->areg));

      /* Copy regs from live window frame. */

      wb_offset = regs->windowbase * 4;
      n = (regs->wmask&1)? 4 : (regs->wmask&2)? 8 : (regs->wmask&4)? 12 : 16;

      for (i = 0; i < n; i++)
            regs->areg[(wb_offset+i) % XCHAL_NUM_AREGS] = elfregs->ar[i];

      n = (regs->wmask >> 4) * 4;

      for (i = XCHAL_NUM_AREGS - n; n > 0; i++, n--)
            regs->areg[(wb_offset+i) % XCHAL_NUM_AREGS] = elfregs->ar[i];
}

/*
 * do_save_fpregs() gathers information from 'struct pt_regs' and
 * 'current->thread' to fill in the elf_fpregset_t structure.
 *
 * Core files and ptrace use elf_fpregset_t.
 */

void do_save_fpregs (elf_fpregset_t *fpregs, struct pt_regs *regs,
                 struct task_struct *tsk)
{
#if XCHAL_HAVE_CP

      extern unsigned char    _xtensa_reginfo_tables[];
      extern unsigned         _xtensa_reginfo_table_size;
      int i;
      unsigned long flags;

      /* Before dumping coprocessor state from memory,
       * ensure any live coprocessor contents for this
       * task are first saved to memory:
       */
      local_irq_save(flags);

      for (i = 0; i < XCHAL_CP_MAX; i++) {
            if (tsk == coprocessor_info[i].owner) {
                  enable_coprocessor(i);
                  save_coprocessor_registers(
                      tsk->thread.cp_save+coprocessor_info[i].offset,i);
                  disable_coprocessor(i);
            }
      }

      local_irq_restore(flags);

      /* Now dump coprocessor & extra state: */
      memcpy((unsigned char*)fpregs,
            _xtensa_reginfo_tables, _xtensa_reginfo_table_size);
      memcpy((unsigned char*)fpregs + _xtensa_reginfo_table_size,
            tsk->thread.cp_save, XTENSA_CP_EXTRA_SIZE);
#endif
}

/*
 * The inverse of do_save_fpregs().
 * Copies coprocessor and extra state from fpregs into regs and tsk->thread.
 * Returns 0 on success, non-zero if layout doesn't match.
 */

int  do_restore_fpregs (elf_fpregset_t *fpregs, struct pt_regs *regs,
                    struct task_struct *tsk)
{
#if XCHAL_HAVE_CP

      extern unsigned char    _xtensa_reginfo_tables[];
      extern unsigned         _xtensa_reginfo_table_size;
      int i;
      unsigned long flags;

      /* Make sure save area layouts match.
       * FIXME:  in the future we could allow restoring from
       * a different layout of the same registers, by comparing
       * fpregs' table with _xtensa_reginfo_tables and matching
       * entries and copying registers one at a time.
       * Not too sure yet whether that's very useful.
       */

      if( memcmp((unsigned char*)fpregs,
            _xtensa_reginfo_tables, _xtensa_reginfo_table_size) ) {
          return -1;
      }

      /* Before restoring coprocessor state from memory,
       * ensure any live coprocessor contents for this
       * task are first invalidated.
       */

      local_irq_save(flags);

      for (i = 0; i < XCHAL_CP_MAX; i++) {
            if (tsk == coprocessor_info[i].owner) {
                  enable_coprocessor(i);
                  save_coprocessor_registers(
                      tsk->thread.cp_save+coprocessor_info[i].offset,i);
                  coprocessor_info[i].owner = 0;
                  disable_coprocessor(i);
            }
      }

      local_irq_restore(flags);

      /*  Now restore coprocessor & extra state:  */

      memcpy(tsk->thread.cp_save,
            (unsigned char*)fpregs + _xtensa_reginfo_table_size,
            XTENSA_CP_EXTRA_SIZE);
#endif
      return 0;
}
/*
 * Fill in the CP structure for a core dump for a particular task.
 */

int
dump_task_fpu(struct pt_regs *regs, struct task_struct *task, elf_fpregset_t *r)
{
      return 0;   /* no coprocessors active on this processor */
}

/*
 * Fill in the CP structure for a core dump.
 * This includes any FPU coprocessor.
 * Here, we dump all coprocessors, and other ("extra") custom state.
 *
 * This function is called by elf_core_dump() in fs/binfmt_elf.c
 * (in which case 'regs' comes from calls to do_coredump, see signals.c).
 */
int  dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
{
      return dump_task_fpu(regs, current, r);
}

asmlinkage
long xtensa_clone(unsigned long clone_flags, unsigned long newsp,
                  void __user *parent_tid, void *child_tls,
                  void __user *child_tid, long a5,
                  struct pt_regs *regs)
{
        if (!newsp)
                newsp = regs->areg[1];
        return do_fork(clone_flags, newsp, regs, 0, parent_tid, child_tid);
}

/*
 *  * xtensa_execve() executes a new program.
 *   */

asmlinkage
long xtensa_execve(char __user *name, char __user * __user *argv,
                   char __user * __user *envp,
                   long a3, long a4, long a5,
                   struct pt_regs *regs)
{
      long error;
      char * filename;

      filename = getname(name);
      error = PTR_ERR(filename);
      if (IS_ERR(filename))
            goto out;
      // FIXME: release coprocessor??
      error = do_execve(filename, argv, envp, regs);
      if (error == 0) {
            task_lock(current);
            current->ptrace &= ~PT_DTRACE;
            task_unlock(current);
      }
      putname(filename);
out:
      return error;
}


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