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ptrace.c

/*
 *  arch/s390/kernel/ptrace.c
 *
 *  S390 version
 *    Copyright (C) 1999,2000 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *    Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com),
 *               Martin Schwidefsky (schwidefsky@de.ibm.com)
 *
 *  Based on PowerPC version 
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *
 *  Derived from "arch/m68k/kernel/ptrace.c"
 *  Copyright (C) 1994 by Hamish Macdonald
 *  Taken from linux/kernel/ptrace.c and modified for M680x0.
 *  linux/kernel/ptrace.c is by Ross Biro 1/23/92, edited by Linus Torvalds
 *
 * Modified by Cort Dougan (cort@cs.nmt.edu) 
 *
 *
 * This file is subject to the terms and conditions of the GNU General
 * Public License.  See the file README.legal in the main directory of
 * this archive for more details.
 */

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

#include <asm/segment.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>

#ifdef CONFIG_COMPAT
#include "compat_ptrace.h"
#endif

static void
FixPerRegisters(struct task_struct *task)
{
      struct pt_regs *regs;
      per_struct *per_info;

      regs = task_pt_regs(task);
      per_info = (per_struct *) &task->thread.per_info;
      per_info->control_regs.bits.em_instruction_fetch =
            per_info->single_step | per_info->instruction_fetch;
      
      if (per_info->single_step) {
            per_info->control_regs.bits.starting_addr = 0;
#ifdef CONFIG_COMPAT
            if (test_thread_flag(TIF_31BIT))
                  per_info->control_regs.bits.ending_addr = 0x7fffffffUL;
            else
#endif
                  per_info->control_regs.bits.ending_addr = PSW_ADDR_INSN;
      } else {
            per_info->control_regs.bits.starting_addr =
                  per_info->starting_addr;
            per_info->control_regs.bits.ending_addr =
                  per_info->ending_addr;
      }
      /*
       * if any of the control reg tracing bits are on 
       * we switch on per in the psw
       */
      if (per_info->control_regs.words.cr[0] & PER_EM_MASK)
            regs->psw.mask |= PSW_MASK_PER;
      else
            regs->psw.mask &= ~PSW_MASK_PER;

      if (per_info->control_regs.bits.em_storage_alteration)
            per_info->control_regs.bits.storage_alt_space_ctl = 1;
      else
            per_info->control_regs.bits.storage_alt_space_ctl = 0;
}

static void set_single_step(struct task_struct *task)
{
      task->thread.per_info.single_step = 1;
      FixPerRegisters(task);
}

static void clear_single_step(struct task_struct *task)
{
      task->thread.per_info.single_step = 0;
      FixPerRegisters(task);
}

/*
 * 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 single step bit is not set. */
      clear_single_step(child);
}

#ifndef CONFIG_64BIT
# define __ADDR_MASK 3
#else
# define __ADDR_MASK 7
#endif

/*
 * Read the word at offset addr from the user area of a process. The
 * trouble here is that the information is littered over different
 * locations. The process registers are found on the kernel stack,
 * the floating point stuff and the trace settings are stored in
 * the task structure. In addition the different structures in
 * struct user contain pad bytes that should be read as zeroes.
 * Lovely...
 */
static int
peek_user(struct task_struct *child, addr_t addr, addr_t data)
{
      struct user *dummy = NULL;
      addr_t offset, tmp, mask;

      /*
       * Stupid gdb peeks/pokes the access registers in 64 bit with
       * an alignment of 4. Programmers from hell...
       */
      mask = __ADDR_MASK;
#ifdef CONFIG_64BIT
      if (addr >= (addr_t) &dummy->regs.acrs &&
          addr < (addr_t) &dummy->regs.orig_gpr2)
            mask = 3;
#endif
      if ((addr & mask) || addr > sizeof(struct user) - __ADDR_MASK)
            return -EIO;

      if (addr < (addr_t) &dummy->regs.acrs) {
            /*
             * psw and gprs are stored on the stack
             */
            tmp = *(addr_t *)((addr_t) &task_pt_regs(child)->psw + addr);
            if (addr == (addr_t) &dummy->regs.psw.mask)
                  /* Remove per bit from user psw. */
                  tmp &= ~PSW_MASK_PER;

      } else if (addr < (addr_t) &dummy->regs.orig_gpr2) {
            /*
             * access registers are stored in the thread structure
             */
            offset = addr - (addr_t) &dummy->regs.acrs;
#ifdef CONFIG_64BIT
            /*
             * Very special case: old & broken 64 bit gdb reading
             * from acrs[15]. Result is a 64 bit value. Read the
             * 32 bit acrs[15] value and shift it by 32. Sick...
             */
            if (addr == (addr_t) &dummy->regs.acrs[15])
                  tmp = ((unsigned long) child->thread.acrs[15]) << 32;
            else
#endif
            tmp = *(addr_t *)((addr_t) &child->thread.acrs + offset);

      } else if (addr == (addr_t) &dummy->regs.orig_gpr2) {
            /*
             * orig_gpr2 is stored on the kernel stack
             */
            tmp = (addr_t) task_pt_regs(child)->orig_gpr2;

      } else if (addr < (addr_t) (&dummy->regs.fp_regs + 1)) {
            /* 
             * floating point regs. are stored in the thread structure
             */
            offset = addr - (addr_t) &dummy->regs.fp_regs;
            tmp = *(addr_t *)((addr_t) &child->thread.fp_regs + offset);
            if (addr == (addr_t) &dummy->regs.fp_regs.fpc)
                  tmp &= (unsigned long) FPC_VALID_MASK
                        << (BITS_PER_LONG - 32);

      } else if (addr < (addr_t) (&dummy->regs.per_info + 1)) {
            /*
             * per_info is found in the thread structure
             */
            offset = addr - (addr_t) &dummy->regs.per_info;
            tmp = *(addr_t *)((addr_t) &child->thread.per_info + offset);

      } else
            tmp = 0;

      return put_user(tmp, (addr_t __user *) data);
}

/*
 * Write a word to the user area of a process at location addr. This
 * operation does have an additional problem compared to peek_user.
 * Stores to the program status word and on the floating point
 * control register needs to get checked for validity.
 */
static int
poke_user(struct task_struct *child, addr_t addr, addr_t data)
{
      struct user *dummy = NULL;
      addr_t offset, mask;

      /*
       * Stupid gdb peeks/pokes the access registers in 64 bit with
       * an alignment of 4. Programmers from hell indeed...
       */
      mask = __ADDR_MASK;
#ifdef CONFIG_64BIT
      if (addr >= (addr_t) &dummy->regs.acrs &&
          addr < (addr_t) &dummy->regs.orig_gpr2)
            mask = 3;
#endif
      if ((addr & mask) || addr > sizeof(struct user) - __ADDR_MASK)
            return -EIO;

      if (addr < (addr_t) &dummy->regs.acrs) {
            /*
             * psw and gprs are stored on the stack
             */
            if (addr == (addr_t) &dummy->regs.psw.mask &&
#ifdef CONFIG_COMPAT
                data != PSW_MASK_MERGE(psw_user32_bits, data) &&
#endif
                data != PSW_MASK_MERGE(psw_user_bits, data))
                  /* Invalid psw mask. */
                  return -EINVAL;
#ifndef CONFIG_64BIT
            if (addr == (addr_t) &dummy->regs.psw.addr)
                  /* I'd like to reject addresses without the
                     high order bit but older gdb's rely on it */
                  data |= PSW_ADDR_AMODE;
#endif
            *(addr_t *)((addr_t) &task_pt_regs(child)->psw + addr) = data;

      } else if (addr < (addr_t) (&dummy->regs.orig_gpr2)) {
            /*
             * access registers are stored in the thread structure
             */
            offset = addr - (addr_t) &dummy->regs.acrs;
#ifdef CONFIG_64BIT
            /*
             * Very special case: old & broken 64 bit gdb writing
             * to acrs[15] with a 64 bit value. Ignore the lower
             * half of the value and write the upper 32 bit to
             * acrs[15]. Sick...
             */
            if (addr == (addr_t) &dummy->regs.acrs[15])
                  child->thread.acrs[15] = (unsigned int) (data >> 32);
            else
#endif
            *(addr_t *)((addr_t) &child->thread.acrs + offset) = data;

      } else if (addr == (addr_t) &dummy->regs.orig_gpr2) {
            /*
             * orig_gpr2 is stored on the kernel stack
             */
            task_pt_regs(child)->orig_gpr2 = data;

      } else if (addr < (addr_t) (&dummy->regs.fp_regs + 1)) {
            /*
             * floating point regs. are stored in the thread structure
             */
            if (addr == (addr_t) &dummy->regs.fp_regs.fpc &&
                (data & ~((unsigned long) FPC_VALID_MASK
                        << (BITS_PER_LONG - 32))) != 0)
                  return -EINVAL;
            offset = addr - (addr_t) &dummy->regs.fp_regs;
            *(addr_t *)((addr_t) &child->thread.fp_regs + offset) = data;

      } else if (addr < (addr_t) (&dummy->regs.per_info + 1)) {
            /*
             * per_info is found in the thread structure 
             */
            offset = addr - (addr_t) &dummy->regs.per_info;
            *(addr_t *)((addr_t) &child->thread.per_info + offset) = data;

      }

      FixPerRegisters(child);
      return 0;
}

static int
do_ptrace_normal(struct task_struct *child, long request, long addr, long data)
{
      ptrace_area parea; 
      int copied, ret;

      switch (request) {
      case PTRACE_PEEKTEXT:
      case PTRACE_PEEKDATA:
            /* Remove high order bit from address (only for 31 bit). */
            addr &= PSW_ADDR_INSN;
            /* read word at location addr. */
            return generic_ptrace_peekdata(child, addr, data);

      case PTRACE_PEEKUSR:
            /* read the word at location addr in the USER area. */
            return peek_user(child, addr, data);

      case PTRACE_POKETEXT:
      case PTRACE_POKEDATA:
            /* Remove high order bit from address (only for 31 bit). */
            addr &= PSW_ADDR_INSN;
            /* write the word at location addr. */
            return generic_ptrace_pokedata(child, addr, data);

      case PTRACE_POKEUSR:
            /* write the word at location addr in the USER area */
            return poke_user(child, addr, data);

      case PTRACE_PEEKUSR_AREA:
      case PTRACE_POKEUSR_AREA:
            if (copy_from_user(&parea, (void __force __user *) addr,
                                          sizeof(parea)))
                  return -EFAULT;
            addr = parea.kernel_addr;
            data = parea.process_addr;
            copied = 0;
            while (copied < parea.len) {
                  if (request == PTRACE_PEEKUSR_AREA)
                        ret = peek_user(child, addr, data);
                  else {
                        addr_t utmp;
                        if (get_user(utmp,
                                   (addr_t __force __user *) data))
                              return -EFAULT;
                        ret = poke_user(child, addr, utmp);
                  }
                  if (ret)
                        return ret;
                  addr += sizeof(unsigned long);
                  data += sizeof(unsigned long);
                  copied += sizeof(unsigned long);
            }
            return 0;
      }
      return ptrace_request(child, request, addr, data);
}

#ifdef CONFIG_COMPAT
/*
 * Now the fun part starts... a 31 bit program running in the
 * 31 bit emulation tracing another program. PTRACE_PEEKTEXT,
 * PTRACE_PEEKDATA, PTRACE_POKETEXT and PTRACE_POKEDATA are easy
 * to handle, the difference to the 64 bit versions of the requests
 * is that the access is done in multiples of 4 byte instead of
 * 8 bytes (sizeof(unsigned long) on 31/64 bit).
 * The ugly part are PTRACE_PEEKUSR, PTRACE_PEEKUSR_AREA,
 * PTRACE_POKEUSR and PTRACE_POKEUSR_AREA. If the traced program
 * is a 31 bit program too, the content of struct user can be
 * emulated. A 31 bit program peeking into the struct user of
 * a 64 bit program is a no-no.
 */

/*
 * Same as peek_user but for a 31 bit program.
 */
static int
peek_user_emu31(struct task_struct *child, addr_t addr, addr_t data)
{
      struct user32 *dummy32 = NULL;
      per_struct32 *dummy_per32 = NULL;
      addr_t offset;
      __u32 tmp;

      if (!test_thread_flag(TIF_31BIT) ||
          (addr & 3) || addr > sizeof(struct user) - 3)
            return -EIO;

      if (addr < (addr_t) &dummy32->regs.acrs) {
            /*
             * psw and gprs are stored on the stack
             */
            if (addr == (addr_t) &dummy32->regs.psw.mask) {
                  /* Fake a 31 bit psw mask. */
                  tmp = (__u32)(task_pt_regs(child)->psw.mask >> 32);
                  tmp = PSW32_MASK_MERGE(psw32_user_bits, tmp);
            } else if (addr == (addr_t) &dummy32->regs.psw.addr) {
                  /* Fake a 31 bit psw address. */
                  tmp = (__u32) task_pt_regs(child)->psw.addr |
                        PSW32_ADDR_AMODE31;
            } else {
                  /* gpr 0-15 */
                  tmp = *(__u32 *)((addr_t) &task_pt_regs(child)->psw +
                               addr*2 + 4);
            }
      } else if (addr < (addr_t) (&dummy32->regs.orig_gpr2)) {
            /*
             * access registers are stored in the thread structure
             */
            offset = addr - (addr_t) &dummy32->regs.acrs;
            tmp = *(__u32*)((addr_t) &child->thread.acrs + offset);

      } else if (addr == (addr_t) (&dummy32->regs.orig_gpr2)) {
            /*
             * orig_gpr2 is stored on the kernel stack
             */
            tmp = *(__u32*)((addr_t) &task_pt_regs(child)->orig_gpr2 + 4);

      } else if (addr < (addr_t) (&dummy32->regs.fp_regs + 1)) {
            /*
             * floating point regs. are stored in the thread structure 
             */
              offset = addr - (addr_t) &dummy32->regs.fp_regs;
            tmp = *(__u32 *)((addr_t) &child->thread.fp_regs + offset);

      } else if (addr < (addr_t) (&dummy32->regs.per_info + 1)) {
            /*
             * per_info is found in the thread structure
             */
            offset = addr - (addr_t) &dummy32->regs.per_info;
            /* This is magic. See per_struct and per_struct32. */
            if ((offset >= (addr_t) &dummy_per32->control_regs &&
                 offset < (addr_t) (&dummy_per32->control_regs + 1)) ||
                (offset >= (addr_t) &dummy_per32->starting_addr &&
                 offset <= (addr_t) &dummy_per32->ending_addr) ||
                offset == (addr_t) &dummy_per32->lowcore.words.address)
                  offset = offset*2 + 4;
            else
                  offset = offset*2;
            tmp = *(__u32 *)((addr_t) &child->thread.per_info + offset);

      } else
            tmp = 0;

      return put_user(tmp, (__u32 __user *) data);
}

/*
 * Same as poke_user but for a 31 bit program.
 */
static int
poke_user_emu31(struct task_struct *child, addr_t addr, addr_t data)
{
      struct user32 *dummy32 = NULL;
      per_struct32 *dummy_per32 = NULL;
      addr_t offset;
      __u32 tmp;

      if (!test_thread_flag(TIF_31BIT) ||
          (addr & 3) || addr > sizeof(struct user32) - 3)
            return -EIO;

      tmp = (__u32) data;

      if (addr < (addr_t) &dummy32->regs.acrs) {
            /*
             * psw, gprs, acrs and orig_gpr2 are stored on the stack
             */
            if (addr == (addr_t) &dummy32->regs.psw.mask) {
                  /* Build a 64 bit psw mask from 31 bit mask. */
                  if (tmp != PSW32_MASK_MERGE(psw32_user_bits, tmp))
                        /* Invalid psw mask. */
                        return -EINVAL;
                  task_pt_regs(child)->psw.mask =
                        PSW_MASK_MERGE(psw_user32_bits, (__u64) tmp << 32);
            } else if (addr == (addr_t) &dummy32->regs.psw.addr) {
                  /* Build a 64 bit psw address from 31 bit address. */
                  task_pt_regs(child)->psw.addr =
                        (__u64) tmp & PSW32_ADDR_INSN;
            } else {
                  /* gpr 0-15 */
                  *(__u32*)((addr_t) &task_pt_regs(child)->psw
                          + addr*2 + 4) = tmp;
            }
      } else if (addr < (addr_t) (&dummy32->regs.orig_gpr2)) {
            /*
             * access registers are stored in the thread structure
             */
            offset = addr - (addr_t) &dummy32->regs.acrs;
            *(__u32*)((addr_t) &child->thread.acrs + offset) = tmp;

      } else if (addr == (addr_t) (&dummy32->regs.orig_gpr2)) {
            /*
             * orig_gpr2 is stored on the kernel stack
             */
            *(__u32*)((addr_t) &task_pt_regs(child)->orig_gpr2 + 4) = tmp;

      } else if (addr < (addr_t) (&dummy32->regs.fp_regs + 1)) {
            /*
             * floating point regs. are stored in the thread structure 
             */
            if (addr == (addr_t) &dummy32->regs.fp_regs.fpc &&
                (tmp & ~FPC_VALID_MASK) != 0)
                  /* Invalid floating point control. */
                  return -EINVAL;
              offset = addr - (addr_t) &dummy32->regs.fp_regs;
            *(__u32 *)((addr_t) &child->thread.fp_regs + offset) = tmp;

      } else if (addr < (addr_t) (&dummy32->regs.per_info + 1)) {
            /*
             * per_info is found in the thread structure.
             */
            offset = addr - (addr_t) &dummy32->regs.per_info;
            /*
             * This is magic. See per_struct and per_struct32.
             * By incident the offsets in per_struct are exactly
             * twice the offsets in per_struct32 for all fields.
             * The 8 byte fields need special handling though,
             * because the second half (bytes 4-7) is needed and
             * not the first half.
             */
            if ((offset >= (addr_t) &dummy_per32->control_regs &&
                 offset < (addr_t) (&dummy_per32->control_regs + 1)) ||
                (offset >= (addr_t) &dummy_per32->starting_addr &&
                 offset <= (addr_t) &dummy_per32->ending_addr) ||
                offset == (addr_t) &dummy_per32->lowcore.words.address)
                  offset = offset*2 + 4;
            else
                  offset = offset*2;
            *(__u32 *)((addr_t) &child->thread.per_info + offset) = tmp;

      }

      FixPerRegisters(child);
      return 0;
}

static int
do_ptrace_emu31(struct task_struct *child, long request, long addr, long data)
{
      unsigned int tmp;  /* 4 bytes !! */
      ptrace_area_emu31 parea; 
      int copied, ret;

      switch (request) {
      case PTRACE_PEEKTEXT:
      case PTRACE_PEEKDATA:
            /* read word at location addr. */
            copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
            if (copied != sizeof(tmp))
                  return -EIO;
            return put_user(tmp, (unsigned int __force __user *) data);

      case PTRACE_PEEKUSR:
            /* read the word at location addr in the USER area. */
            return peek_user_emu31(child, addr, data);

      case PTRACE_POKETEXT:
      case PTRACE_POKEDATA:
            /* write the word at location addr. */
            tmp = data;
            copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 1);
            if (copied != sizeof(tmp))
                  return -EIO;
            return 0;

      case PTRACE_POKEUSR:
            /* write the word at location addr in the USER area */
            return poke_user_emu31(child, addr, data);

      case PTRACE_PEEKUSR_AREA:
      case PTRACE_POKEUSR_AREA:
            if (copy_from_user(&parea, (void __force __user *) addr,
                                          sizeof(parea)))
                  return -EFAULT;
            addr = parea.kernel_addr;
            data = parea.process_addr;
            copied = 0;
            while (copied < parea.len) {
                  if (request == PTRACE_PEEKUSR_AREA)
                        ret = peek_user_emu31(child, addr, data);
                  else {
                        __u32 utmp;
                        if (get_user(utmp,
                                   (__u32 __force __user *) data))
                              return -EFAULT;
                        ret = poke_user_emu31(child, addr, utmp);
                  }
                  if (ret)
                        return ret;
                  addr += sizeof(unsigned int);
                  data += sizeof(unsigned int);
                  copied += sizeof(unsigned int);
            }
            return 0;
      case PTRACE_GETEVENTMSG:
            return put_user((__u32) child->ptrace_message,
                        (unsigned int __force __user *) data);
      case PTRACE_GETSIGINFO:
            if (child->last_siginfo == NULL)
                  return -EINVAL;
            return copy_siginfo_to_user32((compat_siginfo_t
                                     __force __user *) data,
                                    child->last_siginfo);
      case PTRACE_SETSIGINFO:
            if (child->last_siginfo == NULL)
                  return -EINVAL;
            return copy_siginfo_from_user32(child->last_siginfo,
                                    (compat_siginfo_t
                                     __force __user *) data);
      }
      return ptrace_request(child, request, addr, data);
}
#endif

#define PT32_IEEE_IP 0x13c

static int
do_ptrace(struct task_struct *child, long request, long addr, long data)
{
      int ret;

      if (request == PTRACE_ATTACH)
            return ptrace_attach(child);

      /*
       * Special cases to get/store the ieee instructions pointer.
       */
      if (child == current) {
            if (request == PTRACE_PEEKUSR && addr == PT_IEEE_IP)
                  return peek_user(child, addr, data);
            if (request == PTRACE_POKEUSR && addr == PT_IEEE_IP)
                  return poke_user(child, addr, data);
#ifdef CONFIG_COMPAT
            if (request == PTRACE_PEEKUSR &&
                addr == PT32_IEEE_IP && test_thread_flag(TIF_31BIT))
                  return peek_user_emu31(child, addr, data);
            if (request == PTRACE_POKEUSR &&
                addr == PT32_IEEE_IP && test_thread_flag(TIF_31BIT))
                  return poke_user_emu31(child, addr, data);
#endif
      }

      ret = ptrace_check_attach(child, request == PTRACE_KILL);
      if (ret < 0)
            return ret;

      switch (request) {
      case PTRACE_SYSCALL:
            /* continue and stop at next (return from) syscall */
      case PTRACE_CONT:
            /* restart after signal. */
            if (!valid_signal(data))
                  return -EIO;
            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;
            /* make sure the single step bit is not set. */
            clear_single_step(child);
            wake_up_process(child);
            return 0;

      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.
             */
            if (child->exit_state == EXIT_ZOMBIE) /* already dead */
                  return 0;
            child->exit_code = SIGKILL;
            /* make sure the single step bit is not set. */
            clear_single_step(child);
            wake_up_process(child);
            return 0;

      case PTRACE_SINGLESTEP:
            /* set the trap flag. */
            if (!valid_signal(data))
                  return -EIO;
            clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
            child->exit_code = data;
            if (data)
                  set_tsk_thread_flag(child, TIF_SINGLE_STEP);
            else
                  set_single_step(child);
            /* give it a chance to run. */
            wake_up_process(child);
            return 0;

      /* Do requests that differ for 31/64 bit */
      default:
#ifdef CONFIG_COMPAT
            if (test_thread_flag(TIF_31BIT))
                  return do_ptrace_emu31(child, request, addr, data);
#endif
            return do_ptrace_normal(child, request, addr, data);
      }
      /* Not reached.  */
      return -EIO;
}

asmlinkage long
sys_ptrace(long request, long pid, long addr, long data)
{
      struct task_struct *child;
      int ret;

      lock_kernel();
      if (request == PTRACE_TRACEME) {
             ret = ptrace_traceme();
             goto out;
      }

      child = ptrace_get_task_struct(pid);
      if (IS_ERR(child)) {
            ret = PTR_ERR(child);
            goto out;
      }

      ret = do_ptrace(child, request, addr, data);
      put_task_struct(child);
out:
      unlock_kernel();
      return ret;
}

asmlinkage void
syscall_trace(struct pt_regs *regs, int entryexit)
{
      if (unlikely(current->audit_context) && entryexit)
            audit_syscall_exit(AUDITSC_RESULT(regs->gprs[2]), regs->gprs[2]);

      if (!test_thread_flag(TIF_SYSCALL_TRACE))
            goto out;
      if (!(current->ptrace & PT_PTRACED))
            goto out;
      ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
                         ? 0x80 : 0));

      /*
       * If the debuffer has set an invalid system call number,
       * we prepare to skip the system call restart handling.
       */
      if (!entryexit && regs->gprs[2] >= NR_syscalls)
            regs->trap = -1;

      /*
       * 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;
      }
 out:
      if (unlikely(current->audit_context) && !entryexit)
            audit_syscall_entry(test_thread_flag(TIF_31BIT)?AUDIT_ARCH_S390:AUDIT_ARCH_S390X,
                            regs->gprs[2], regs->orig_gpr2, regs->gprs[3],
                            regs->gprs[4], regs->gprs[5]);
}

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