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ptrace.c

/*
 * Copyright 2003 PathScale, Inc.
 * Copyright (C) 2003 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 *
 * Licensed under the GPL
 */

#define __FRAME_OFFSETS
#include <asm/ptrace.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <asm/uaccess.h>
#include <asm/elf.h>

/*
 * determines which flags the user has access to.
 * 1 = access 0 = no access
 */
#define FLAG_MASK 0x44dd5UL

int putreg(struct task_struct *child, int regno, unsigned long value)
{
      unsigned long tmp;

#ifdef TIF_IA32
      /* Some code in the 64bit emulation may not be 64bit clean.
         Don't take any chances. */
      if (test_tsk_thread_flag(child, TIF_IA32))
            value &= 0xffffffff;
#endif
      switch (regno){
      case FS:
      case GS:
      case DS:
      case ES:
      case SS:
      case CS:
            if (value && (value & 3) != 3)
                  return -EIO;
            value &= 0xffff;
            break;

      case FS_BASE:
      case GS_BASE:
            if (!((value >> 48) == 0 || (value >> 48) == 0xffff))
                  return -EIO;
            break;

      case EFLAGS:
            value &= FLAG_MASK;
            tmp = PT_REGS_EFLAGS(&child->thread.regs) & ~FLAG_MASK;
            value |= tmp;
            break;
      }

      PT_REGS_SET(&child->thread.regs, regno, value);
      return 0;
}

int poke_user(struct task_struct *child, long addr, long data)
{
      if ((addr & 3) || addr < 0)
            return -EIO;

      if (addr < MAX_REG_OFFSET)
            return putreg(child, addr, data);
      else if ((addr >= offsetof(struct user, u_debugreg[0])) &&
            (addr <= offsetof(struct user, u_debugreg[7]))){
            addr -= offsetof(struct user, u_debugreg[0]);
            addr = addr >> 2;
            if ((addr == 4) || (addr == 5))
                  return -EIO;
            child->thread.arch.debugregs[addr] = data;
            return 0;
      }
      return -EIO;
}

unsigned long getreg(struct task_struct *child, int regno)
{
      unsigned long retval = ~0UL;
      switch (regno) {
      case FS:
      case GS:
      case DS:
      case ES:
      case SS:
      case CS:
            retval = 0xffff;
            /* fall through */
      default:
            retval &= PT_REG(&child->thread.regs, regno);
#ifdef TIF_IA32
            if (test_tsk_thread_flag(child, TIF_IA32))
                  retval &= 0xffffffff;
#endif
      }
      return retval;
}

int peek_user(struct task_struct *child, long addr, long data)
{
      /* read the word at location addr in the USER area. */
      unsigned long tmp;

      if ((addr & 3) || addr < 0)
            return -EIO;

      tmp = 0;  /* Default return condition */
      if (addr < MAX_REG_OFFSET){
            tmp = getreg(child, addr);
      }
      else if ((addr >= offsetof(struct user, u_debugreg[0])) &&
            (addr <= offsetof(struct user, u_debugreg[7]))){
            addr -= offsetof(struct user, u_debugreg[0]);
            addr = addr >> 2;
            tmp = child->thread.arch.debugregs[addr];
      }
      return put_user(tmp, (unsigned long *) data);
}

/* XXX Mostly copied from sys-i386 */
int is_syscall(unsigned long addr)
{
      unsigned short instr;
      int n;

      n = copy_from_user(&instr, (void __user *) addr, sizeof(instr));
      if (n){
            /* access_process_vm() grants access to vsyscall and stub,
             * while copy_from_user doesn't. Maybe access_process_vm is
             * slow, but that doesn't matter, since it will be called only
             * in case of singlestepping, if copy_from_user failed.
             */
            n = access_process_vm(current, addr, &instr, sizeof(instr), 0);
            if (n != sizeof(instr)) {
                  printk("is_syscall : failed to read instruction from "
                         "0x%lx\n", addr);
                  return 1;
            }
      }
      /* sysenter */
      return instr == 0x050f;
}

int get_fpregs(struct user_i387_struct __user *buf, struct task_struct *child)
{
      int err, n, cpu = ((struct thread_info *) child->stack)->cpu;
      long fpregs[HOST_FP_SIZE];

      BUG_ON(sizeof(*buf) != sizeof(fpregs));
      err = save_fp_registers(userspace_pid[cpu], fpregs);
      if (err)
            return err;

      n = copy_to_user(buf, fpregs, sizeof(fpregs));
      if(n > 0)
            return -EFAULT;

      return n;
}

int set_fpregs(struct user_i387_struct __user *buf, struct task_struct *child)
{
      int n, cpu = ((struct thread_info *) child->stack)->cpu;
      long fpregs[HOST_FP_SIZE];

      BUG_ON(sizeof(*buf) != sizeof(fpregs));
      n = copy_from_user(fpregs, buf, sizeof(fpregs));
      if (n > 0)
            return -EFAULT;

      return restore_fp_registers(userspace_pid[cpu], fpregs);
}

long subarch_ptrace(struct task_struct *child, long request, long addr,
                long data)
{
      int ret = -EIO;

      switch (request) {
      case PTRACE_GETFPXREGS: /* Get the child FPU state. */
            ret = get_fpregs((struct user_i387_struct __user *) data,
                         child);
            break;
      case PTRACE_SETFPXREGS: /* Set the child FPU state. */
            ret = set_fpregs((struct user_i387_struct __user *) data,
                         child);
            break;
      }

      return ret;
}

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