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ptrace.c

/*
 * arch/v850/kernel/ptrace.c -- `ptrace' system call
 *
 *  Copyright (C) 2002,03,04  NEC Electronics Corporation
 *  Copyright (C) 2002,03,04  Miles Bader <miles@gnu.org>
 *
 * Derived from arch/mips/kernel/ptrace.c:
 *
 *  Copyright (C) 1992 Ross Biro
 *  Copyright (C) Linus Torvalds
 *  Copyright (C) 1994, 95, 96, 97, 98, 2000 Ralf Baechle
 *  Copyright (C) 1996 David S. Miller
 *  Kevin D. Kissell, kevink@mips.com and Carsten Langgaard, carstenl@mips.com
 *  Copyright (C) 1999 MIPS Technologies, Inc.
 *
 * 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.
 */

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/signal.h>

#include <asm/errno.h>
#include <asm/ptrace.h>
#include <asm/processor.h>
#include <asm/uaccess.h>

/* Returns the address where the register at REG_OFFS in P is stashed away.  */
static v850_reg_t *reg_save_addr (unsigned reg_offs, struct task_struct *t)
{
      struct pt_regs *regs;

      /* Three basic cases:

         (1) A register normally saved before calling the scheduler, is
             available in the kernel entry pt_regs structure at the top
             of the kernel stack.  The kernel trap/irq exit path takes
             care to save/restore almost all registers for ptrace'd
             processes.

         (2) A call-clobbered register, where the process P entered the
             kernel via [syscall] trap, is not stored anywhere; that's
             OK, because such registers are not expected to be preserved
             when the trap returns anyway (so we don't actually bother to
             test for this case).

         (3) A few registers not used at all by the kernel, and so
             normally never saved except by context-switches, are in the
             context switch state.  */

      if (reg_offs == PT_CTPC || reg_offs == PT_CTPSW || reg_offs == PT_CTBP)
            /* Register saved during context switch.  */
            regs = thread_saved_regs (t);
      else
            /* Register saved during kernel entry (or not available).  */
            regs = task_pt_regs (t);

      return (v850_reg_t *)((char *)regs + reg_offs);
}

/* Set the bits SET and clear the bits CLEAR in the v850e DIR
   (`debug information register').  Returns the new value of DIR.  */
static inline v850_reg_t set_dir (v850_reg_t set, v850_reg_t clear)
{
      register v850_reg_t rval asm ("r10");
      register v850_reg_t arg0 asm ("r6") = set;
      register v850_reg_t arg1 asm ("r7") = clear;

      /* The dbtrap handler has exactly this functionality when called
         from kernel mode.  0xf840 is a `dbtrap' insn.  */
      asm (".short 0xf840" : "=r" (rval) : "r" (arg0), "r" (arg1));

      return rval;
}

/* Makes sure hardware single-stepping is (globally) enabled.
   Returns true if successful.  */
static inline int enable_single_stepping (void)
{
      static int enabled = 0; /* Remember whether we already did it.  */
      if (! enabled) {
            /* Turn on the SE (`single-step enable') bit, 0x100, in the
               DIR (`debug information register').  This may fail if a
               processor doesn't support it or something.  We also try
               to clear bit 0x40 (`INI'), which is necessary to use the
               debug stuff on the v850e2; on the v850e, clearing 0x40
               shouldn't cause any problem.  */
            v850_reg_t dir = set_dir (0x100, 0x40);
            /* Make sure it really got set.  */
            if (dir & 0x100)
                  enabled = 1;
      }
      return enabled;
}

/* Try to set CHILD's single-step flag to VAL.  Returns true if successful.  */
static int set_single_step (struct task_struct *t, int val)
{
      v850_reg_t *psw_addr = reg_save_addr(PT_PSW, t);
      if (val) {
            /* Make sure single-stepping is enabled.  */
            if (! enable_single_stepping ())
                  return 0;
            /* Set T's single-step flag.  */
            *psw_addr |= 0x800;
      } else
            *psw_addr &= ~0x800;
      return 1;
}

long arch_ptrace(struct task_struct *child, long request, long addr, long data)
{
      int rval;

      switch (request) {
            unsigned long val;

      case PTRACE_PEEKTEXT: /* read word at location addr. */
      case PTRACE_PEEKDATA:
            rval = generic_ptrace_peekdata(child, addr, data);
            goto out;

      case PTRACE_POKETEXT: /* write the word at location addr. */
      case PTRACE_POKEDATA:
            rval = generic_ptrace_pokedata(child, addr, data);
            goto out;

      /* Read/write the word at location ADDR in the registers.  */
      case PTRACE_PEEKUSR:
      case PTRACE_POKEUSR:
            rval = 0;
            if (addr >= PT_SIZE && request == PTRACE_PEEKUSR) {
                  /* Special requests that don't actually correspond
                     to offsets in struct pt_regs.  */
                  if (addr == PT_TEXT_ADDR)
                        val = child->mm->start_code;
                  else if (addr == PT_DATA_ADDR)
                        val = child->mm->start_data;
                  else if (addr == PT_TEXT_LEN)
                        val = child->mm->end_code
                              - child->mm->start_code;
                  else
                        rval = -EIO;
            } else if (addr >= 0 && addr < PT_SIZE && (addr & 0x3) == 0) {
                  v850_reg_t *reg_addr = reg_save_addr(addr, child);
                  if (request == PTRACE_PEEKUSR)
                        val = *reg_addr;
                  else
                        *reg_addr = data;
            } else
                  rval = -EIO;

            if (rval == 0 && request == PTRACE_PEEKUSR)
                  rval = put_user (val, (unsigned long *)data);
            goto out;

      /* Continue and stop at next (return from) syscall */
      case PTRACE_SYSCALL:
      /* Restart after a signal.  */
      case PTRACE_CONT:
      /* Execute a single instruction. */
      case PTRACE_SINGLESTEP:
            rval = -EIO;
            if (!valid_signal(data))
                  break;

            /* Turn CHILD's single-step flag on or off.  */
            if (! set_single_step (child, request == PTRACE_SINGLESTEP))
                  break;

            if (request == PTRACE_SYSCALL)
                  set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
            else
                  clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);

            child->exit_code = data;
            wake_up_process(child);
            rval = 0;
            break;

      /*
       * make the child exit.  Best I can do is send it a sigkill.
       * perhaps it should be put in the status that it wants to
       * exit.
       */
      case PTRACE_KILL:
            rval = 0;
            if (child->exit_state == EXIT_ZOMBIE)     /* already dead */
                  break;
            child->exit_code = SIGKILL;
            wake_up_process(child);
            break;

      case PTRACE_DETACH: /* detach a process that was attached. */
            set_single_step (child, 0);  /* Clear single-step flag */
            rval = ptrace_detach(child, data);
            break;

      default:
            rval = -EIO;
            goto out;
      }
 out:
      return rval;
}

asmlinkage void syscall_trace(void)
{
      if (!test_thread_flag(TIF_SYSCALL_TRACE))
            return;
      if (!(current->ptrace & PT_PTRACED))
            return;
      /* The 0x80 provides a way for the tracing parent to distinguish
         between a syscall stop and SIGTRAP delivery */
      ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
                         ? 0x80 : 0));
      /*
       * this isn't the same as continuing with a signal, but it will do
       * for normal use.  strace only continues with a signal if the
       * stopping signal is not SIGTRAP.  -brl
       */
      if (current->exit_code) {
            send_sig(current->exit_code, current, 1);
            current->exit_code = 0;
      }
}

void ptrace_disable (struct task_struct *child)
{
      /* nothing to do */
}

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