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ptrace.c

/*
 * Kernel support for the ptrace() and syscall tracing interfaces.
 *
 * Copyright (C) 2000 Hewlett-Packard Co, Linuxcare Inc.
 * Copyright (C) 2000 Matthew Wilcox <matthew@wil.cx>
 * Copyright (C) 2000 David Huggins-Daines <dhd@debian.org>
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/user.h>
#include <linux/personality.h>
#include <linux/security.h>
#include <linux/compat.h>
#include <linux/signal.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/processor.h>
#include <asm/asm-offsets.h>

/* PSW bits we allow the debugger to modify */
#define USER_PSW_BITS   (PSW_N | PSW_V | PSW_CB)

#undef DEBUG_PTRACE

#ifdef DEBUG_PTRACE
#define DBG(x...) printk(x)
#else
#define DBG(x...)
#endif

#ifdef CONFIG_64BIT

/* This function is needed to translate 32 bit pt_regs offsets in to
 * 64 bit pt_regs offsets.  For example, a 32 bit gdb under a 64 bit kernel
 * will request offset 12 if it wants gr3, but the lower 32 bits of
 * the 64 bit kernels view of gr3 will be at offset 28 (3*8 + 4).
 * This code relies on a 32 bit pt_regs being comprised of 32 bit values
 * except for the fp registers which (a) are 64 bits, and (b) follow
 * the gr registers at the start of pt_regs.  The 32 bit pt_regs should
 * be half the size of the 64 bit pt_regs, plus 32*4 to allow for fr[]
 * being 64 bit in both cases.
 */

static long translate_usr_offset(long offset)
{
      if (offset < 0)
            return -1;
      else if (offset <= 32*4)      /* gr[0..31] */
            return offset * 2 + 4;
      else if (offset <= 32*4+32*8) /* gr[0..31] + fr[0..31] */
            return offset + 32*4;
      else if (offset < sizeof(struct pt_regs)/2 + 32*4)
            return offset * 2 + 4 - 32*8;
      else
            return -1;
}
#endif

/*
 * Called by kernel/ptrace.c when detaching..
 *
 * Make sure single step bits etc are not set.
 */
void ptrace_disable(struct task_struct *child)
{
      /* make sure the trap bits are not set */
      pa_psw(child)->r = 0;
      pa_psw(child)->t = 0;
      pa_psw(child)->h = 0;
      pa_psw(child)->l = 0;
}

long arch_ptrace(struct task_struct *child, long request, long addr, long data)
{
      long ret;
#ifdef DEBUG_PTRACE
      long oaddr=addr, odata=data;
#endif

      switch (request) {
      case PTRACE_PEEKTEXT: /* read word at location addr. */ 
      case PTRACE_PEEKDATA: {
#ifdef CONFIG_64BIT
            if (__is_compat_task(child)) {
                  int copied;
                  unsigned int tmp;

                  addr &= 0xffffffffL;
                  copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
                  ret = -EIO;
                  if (copied != sizeof(tmp))
                        goto out_tsk;
                  ret = put_user(tmp,(unsigned int *) data);
                  DBG("sys_ptrace(PEEK%s, %d, %lx, %lx) returning %ld, data %x\n",
                        request == PTRACE_PEEKTEXT ? "TEXT" : "DATA",
                        pid, oaddr, odata, ret, tmp);
            }
            else
#endif
                  ret = generic_ptrace_peekdata(child, addr, data);
            goto out_tsk;
      }

      /* when I and D space are separate, this will have to be fixed. */
      case PTRACE_POKETEXT: /* write the word at location addr. */
      case PTRACE_POKEDATA:
            ret = 0;
#ifdef CONFIG_64BIT
            if (__is_compat_task(child)) {
                  unsigned int tmp = (unsigned int)data;
                  DBG("sys_ptrace(POKE%s, %d, %lx, %lx)\n",
                        request == PTRACE_POKETEXT ? "TEXT" : "DATA",
                        pid, oaddr, odata);
                  addr &= 0xffffffffL;
                  if (access_process_vm(child, addr, &tmp, sizeof(tmp), 1) == sizeof(tmp))
                        goto out_tsk;
            }
            else
#endif
            {
                  if (access_process_vm(child, addr, &data, sizeof(data), 1) == sizeof(data))
                        goto out_tsk;
            }
            ret = -EIO;
            goto out_tsk;

      /* Read the word at location addr in the USER area.  For ptraced
         processes, the kernel saves all regs on a syscall. */
      case PTRACE_PEEKUSR: {
            ret = -EIO;
#ifdef CONFIG_64BIT
            if (__is_compat_task(child)) {
                  unsigned int tmp;

                  if (addr & (sizeof(int)-1))
                        goto out_tsk;
                  if ((addr = translate_usr_offset(addr)) < 0)
                        goto out_tsk;

                  tmp = *(unsigned int *) ((char *) task_regs(child) + addr);
                  ret = put_user(tmp, (unsigned int *) data);
                  DBG("sys_ptrace(PEEKUSR, %d, %lx, %lx) returning %ld, addr %lx, data %x\n",
                        pid, oaddr, odata, ret, addr, tmp);
            }
            else
#endif
            {
                  unsigned long tmp;

                  if ((addr & (sizeof(long)-1)) || (unsigned long) addr >= sizeof(struct pt_regs))
                        goto out_tsk;
                  tmp = *(unsigned long *) ((char *) task_regs(child) + addr);
                  ret = put_user(tmp, (unsigned long *) data);
            }
            goto out_tsk;
      }

      /* Write the word at location addr in the USER area.  This will need
         to change when the kernel no longer saves all regs on a syscall.
         FIXME.  There is a problem at the moment in that r3-r18 are only
         saved if the process is ptraced on syscall entry, and even then
         those values are overwritten by actual register values on syscall
         exit. */
      case PTRACE_POKEUSR:
            ret = -EIO;
            /* Some register values written here may be ignored in
             * entry.S:syscall_restore_rfi; e.g. iaoq is written with
             * r31/r31+4, and not with the values in pt_regs.
             */
             /* PT_PSW=0, so this is valid for 32 bit processes under 64
             * bit kernels.
             */
            if (addr == PT_PSW) {
                  /* PT_PSW=0, so this is valid for 32 bit processes
                   * under 64 bit kernels.
                   *
                   * Allow writing to Nullify, Divide-step-correction,
                   * and carry/borrow bits.
                   * BEWARE, if you set N, and then single step, it won't
                   * stop on the nullified instruction.
                   */
                  DBG("sys_ptrace(POKEUSR, %d, %lx, %lx)\n",
                        pid, oaddr, odata);
                  data &= USER_PSW_BITS;
                  task_regs(child)->gr[0] &= ~USER_PSW_BITS;
                  task_regs(child)->gr[0] |= data;
                  ret = 0;
                  goto out_tsk;
            }
#ifdef CONFIG_64BIT
            if (__is_compat_task(child)) {
                  if (addr & (sizeof(int)-1))
                        goto out_tsk;
                  if ((addr = translate_usr_offset(addr)) < 0)
                        goto out_tsk;
                  DBG("sys_ptrace(POKEUSR, %d, %lx, %lx) addr %lx\n",
                        pid, oaddr, odata, addr);
                  if (addr >= PT_FR0 && addr <= PT_FR31 + 4) {
                        /* Special case, fp regs are 64 bits anyway */
                        *(unsigned int *) ((char *) task_regs(child) + addr) = data;
                        ret = 0;
                  }
                  else if ((addr >= PT_GR1+4 && addr <= PT_GR31+4) ||
                              addr == PT_IAOQ0+4 || addr == PT_IAOQ1+4 ||
                              addr == PT_SAR+4) {
                        /* Zero the top 32 bits */
                        *(unsigned int *) ((char *) task_regs(child) + addr - 4) = 0;
                        *(unsigned int *) ((char *) task_regs(child) + addr) = data;
                        ret = 0;
                  }
                  goto out_tsk;
            }
            else
#endif
            {
                  if ((addr & (sizeof(long)-1)) || (unsigned long) addr >= sizeof(struct pt_regs))
                        goto out_tsk;
                  if ((addr >= PT_GR1 && addr <= PT_GR31) ||
                              addr == PT_IAOQ0 || addr == PT_IAOQ1 ||
                              (addr >= PT_FR0 && addr <= PT_FR31 + 4) ||
                              addr == PT_SAR) {
                        *(unsigned long *) ((char *) task_regs(child) + addr) = data;
                        ret = 0;
                  }
                  goto out_tsk;
            }

      case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
      case PTRACE_CONT:
            ret = -EIO;
            DBG("sys_ptrace(%s)\n",
                  request == PTRACE_SYSCALL ? "SYSCALL" : "CONT");
            if (!valid_signal(data))
                  goto out_tsk;
            child->ptrace &= ~(PT_SINGLESTEP|PT_BLOCKSTEP);
            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;
            goto out_wake_notrap;

      case PTRACE_KILL:
            /*
             * 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.
             */
            ret = 0;
            DBG("sys_ptrace(KILL)\n");
            if (child->exit_state == EXIT_ZOMBIE)     /* already dead */
                  goto out_tsk;
            child->exit_code = SIGKILL;
            goto out_wake_notrap;

      case PTRACE_SINGLEBLOCK:
            DBG("sys_ptrace(SINGLEBLOCK)\n");
            ret = -EIO;
            if (!valid_signal(data))
                  goto out_tsk;
            clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
            child->ptrace &= ~PT_SINGLESTEP;
            child->ptrace |= PT_BLOCKSTEP;
            child->exit_code = data;

            /* Enable taken branch trap. */
            pa_psw(child)->r = 0;
            pa_psw(child)->t = 1;
            pa_psw(child)->h = 0;
            pa_psw(child)->l = 0;
            goto out_wake;

      case PTRACE_SINGLESTEP:
            DBG("sys_ptrace(SINGLESTEP)\n");
            ret = -EIO;
            if (!valid_signal(data))
                  goto out_tsk;

            clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
            child->ptrace &= ~PT_BLOCKSTEP;
            child->ptrace |= PT_SINGLESTEP;
            child->exit_code = data;

            if (pa_psw(child)->n) {
                  struct siginfo si;

                  /* Nullified, just crank over the queue. */
                  task_regs(child)->iaoq[0] = task_regs(child)->iaoq[1];
                  task_regs(child)->iasq[0] = task_regs(child)->iasq[1];
                  task_regs(child)->iaoq[1] = task_regs(child)->iaoq[0] + 4;
                  pa_psw(child)->n = 0;
                  pa_psw(child)->x = 0;
                  pa_psw(child)->y = 0;
                  pa_psw(child)->z = 0;
                  pa_psw(child)->b = 0;
                  ptrace_disable(child);
                  /* Don't wake up the child, but let the
                     parent know something happened. */
                  si.si_code = TRAP_TRACE;
                  si.si_addr = (void __user *) (task_regs(child)->iaoq[0] & ~3);
                  si.si_signo = SIGTRAP;
                  si.si_errno = 0;
                  force_sig_info(SIGTRAP, &si, child);
                  //notify_parent(child, SIGCHLD);
                  //ret = 0;
                  goto out_wake;
            }

            /* Enable recovery counter traps.  The recovery counter
             * itself will be set to zero on a task switch.  If the
             * task is suspended on a syscall then the syscall return
             * path will overwrite the recovery counter with a suitable
             * value such that it traps once back in user space.  We
             * disable interrupts in the childs PSW here also, to avoid
             * interrupts while the recovery counter is decrementing.
             */
            pa_psw(child)->r = 1;
            pa_psw(child)->t = 0;
            pa_psw(child)->h = 0;
            pa_psw(child)->l = 0;
            /* give it a chance to run. */
            goto out_wake;

      case PTRACE_GETEVENTMSG:
                ret = put_user(child->ptrace_message, (unsigned int __user *) data);
            goto out_tsk;

      default:
            ret = ptrace_request(child, request, addr, data);
            goto out_tsk;
      }

out_wake_notrap:
      ptrace_disable(child);
out_wake:
      wake_up_process(child);
      ret = 0;
out_tsk:
      DBG("arch_ptrace(%ld, %d, %lx, %lx) returning %ld\n",
            request, pid, oaddr, odata, ret);
      return ret;
}

void syscall_trace(void)
{
      if (!test_thread_flag(TIF_SYSCALL_TRACE))
            return;
      if (!(current->ptrace & PT_PTRACED))
            return;
      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;
      }
}

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