long arch_ptrace(struct task_struct *child, long request, long addr, long data)
{
	struct user * dummy = NULL;
	int i, ret;
	unsigned long __user *datap = (unsigned long __user *)data;

	switch (request) {
	/* when I and D space are separate, these will need to be fixed. */
	case PTRACE_PEEKTEXT: /* read word at location addr. */ 
	case PTRACE_PEEKDATA:
		ret = generic_ptrace_peekdata(child, addr, data);
		break;

	/* read the word at location addr in the USER area. */
	case PTRACE_PEEKUSR: {
		unsigned long tmp;

		ret = -EIO;
		if ((addr & 3) || addr < 0 || 
		    addr > sizeof(struct user) - 3)
			break;

		tmp = 0;  /* Default return condition */
		if(addr < FRAME_SIZE*sizeof(long))
			tmp = getreg(child, addr);
		if(addr >= (long) &dummy->u_debugreg[0] &&
		   addr <= (long) &dummy->u_debugreg[7]){
			addr -= (long) &dummy->u_debugreg[0];
			addr = addr >> 2;
			tmp = child->thread.debugreg[addr];
		}
		ret = put_user(tmp, datap);
		break;
	}

	/* 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 = generic_ptrace_pokedata(child, addr, data);
		break;

	case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
		ret = -EIO;
		if ((addr & 3) || addr < 0 || 
		    addr > sizeof(struct user) - 3)
			break;

		if (addr < FRAME_SIZE*sizeof(long)) {
			ret = putreg(child, addr, data);
			break;
		}
		/* We need to be very careful here.  We implicitly
		   want to modify a portion of the task_struct, and we
		   have to be selective about what portions we allow someone
		   to modify. */

		  ret = -EIO;
		  if(addr >= (long) &dummy->u_debugreg[0] &&
		     addr <= (long) &dummy->u_debugreg[7]){

			  if(addr == (long) &dummy->u_debugreg[4]) break;
			  if(addr == (long) &dummy->u_debugreg[5]) break;
			  if(addr < (long) &dummy->u_debugreg[4] &&
			     ((unsigned long) data) >= TASK_SIZE-3) break;
			  
			  /* Sanity-check data. Take one half-byte at once with
			   * check = (val >> (16 + 4*i)) & 0xf. It contains the
			   * R/Wi and LENi bits; bits 0 and 1 are R/Wi, and bits
			   * 2 and 3 are LENi. Given a list of invalid values,
			   * we do mask |= 1 << invalid_value, so that
			   * (mask >> check) & 1 is a correct test for invalid
			   * values.
			   *
			   * R/Wi contains the type of the breakpoint /
			   * watchpoint, LENi contains the length of the watched
			   * data in the watchpoint case.
			   *
			   * The invalid values are:
			   * - LENi == 0x10 (undefined), so mask |= 0x0f00.
			   * - R/Wi == 0x10 (break on I/O reads or writes), so
			   *   mask |= 0x4444.
			   * - R/Wi == 0x00 && LENi != 0x00, so we have mask |=
			   *   0x1110.
			   *
			   * Finally, mask = 0x0f00 | 0x4444 | 0x1110 == 0x5f54.
			   *
			   * See the Intel Manual "System Programming Guide",
			   * 15.2.4
			   *
			   * Note that LENi == 0x10 is defined on x86_64 in long
			   * mode (i.e. even for 32-bit userspace software, but
			   * 64-bit kernel), so the x86_64 mask value is 0x5454.
			   * See the AMD manual no. 24593 (AMD64 System
			   * Programming)*/

			  if(addr == (long) &dummy->u_debugreg[7]) {
				  data &= ~DR_CONTROL_RESERVED;
				  for(i=0; i<4; i++)
					  if ((0x5f54 >> ((data >> (16 + 4*i)) & 0xf)) & 1)
						  goto out_tsk;
				  if (data)
					  set_tsk_thread_flag(child, TIF_DEBUG);
				  else
					  clear_tsk_thread_flag(child, TIF_DEBUG);
			  }
			  addr -= (long) &dummy->u_debugreg;
			  addr = addr >> 2;
			  child->thread.debugreg[addr] = data;
			  ret = 0;
		  }
		  break;

	case PTRACE_SYSEMU: /* continue and stop at next syscall, which will not be executed */
	case PTRACE_SYSCALL:	/* continue and stop at next (return from) syscall */
	case PTRACE_CONT:	/* restart after signal. */
		ret = -EIO;
		if (!valid_signal(data))
			break;
		if (request == PTRACE_SYSEMU) {
			set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
		} else if (request == PTRACE_SYSCALL) {
			set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
		} else {
			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
		}
		child->exit_code = data;
		/* make sure the single step bit is not set. */
		clear_singlestep(child);
		wake_up_process(child);
		ret = 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:
		ret = 0;
		if (child->exit_state == EXIT_ZOMBIE)	/* already dead */
			break;
		child->exit_code = SIGKILL;
		/* make sure the single step bit is not set. */
		clear_singlestep(child);
		wake_up_process(child);
		break;

	case PTRACE_SYSEMU_SINGLESTEP: /* Same as SYSEMU, but singlestep if not syscall */
	case PTRACE_SINGLESTEP:	/* set the trap flag. */
		ret = -EIO;
		if (!valid_signal(data))
			break;

		if (request == PTRACE_SYSEMU_SINGLESTEP)
			set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
		else
			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);

		clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
		set_singlestep(child);
		child->exit_code = data;
		/* give it a chance to run. */
		wake_up_process(child);
		ret = 0;
		break;

	case PTRACE_DETACH:
		/* detach a process that was attached. */
		ret = ptrace_detach(child, data);
		break;

	case PTRACE_GETREGS: { /* Get all gp regs from the child. */
	  	if (!access_ok(VERIFY_WRITE, datap, FRAME_SIZE*sizeof(long))) {
			ret = -EIO;
			break;
		}
		for ( i = 0; i < FRAME_SIZE*sizeof(long); i += sizeof(long) ) {
			__put_user(getreg(child, i), datap);
			datap++;
		}
		ret = 0;
		break;
	}

	case PTRACE_SETREGS: { /* Set all gp regs in the child. */
		unsigned long tmp;
	  	if (!access_ok(VERIFY_READ, datap, FRAME_SIZE*sizeof(long))) {
			ret = -EIO;
			break;
		}
		for ( i = 0; i < FRAME_SIZE*sizeof(long); i += sizeof(long) ) {
			__get_user(tmp, datap);
			putreg(child, i, tmp);
			datap++;
		}
		ret = 0;
		break;
	}

	case PTRACE_GETFPREGS: { /* Get the child FPU state. */
		if (!access_ok(VERIFY_WRITE, datap,
			       sizeof(struct user_i387_struct))) {
			ret = -EIO;
			break;
		}
		ret = 0;
		if (!tsk_used_math(child))
			init_fpu(child);
		get_fpregs((struct user_i387_struct __user *)data, child);
		break;
	}

	case PTRACE_SETFPREGS: { /* Set the child FPU state. */
		if (!access_ok(VERIFY_READ, datap,
			       sizeof(struct user_i387_struct))) {
			ret = -EIO;
			break;
		}
		set_stopped_child_used_math(child);
		set_fpregs(child, (struct user_i387_struct __user *)data);
		ret = 0;
		break;
	}

	case PTRACE_GETFPXREGS: { /* Get the child extended FPU state. */
		if (!access_ok(VERIFY_WRITE, datap,
			       sizeof(struct user_fxsr_struct))) {
			ret = -EIO;
			break;
		}
		if (!tsk_used_math(child))
			init_fpu(child);
		ret = get_fpxregs((struct user_fxsr_struct __user *)data, child);
		break;
	}

	case PTRACE_SETFPXREGS: { /* Set the child extended FPU state. */
		if (!access_ok(VERIFY_READ, datap,
			       sizeof(struct user_fxsr_struct))) {
			ret = -EIO;
			break;
		}
		set_stopped_child_used_math(child);
		ret = set_fpxregs(child, (struct user_fxsr_struct __user *)data);
		break;
	}

	case PTRACE_GET_THREAD_AREA:
		ret = ptrace_get_thread_area(child, addr,
					(struct user_desc __user *) data);
		break;

	case PTRACE_SET_THREAD_AREA:
		ret = ptrace_set_thread_area(child, addr,
					(struct user_desc __user *) data);
		break;

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