ptrace.c

linux 内核源代码

	res = read_instr(child, pc, &insn);
	if (!res) {
		struct debug_info *dbg = &child->thread.debug;
		unsigned long alt;

		dbg->nsaved = 0;

		alt = get_branch_address(child, pc, insn);
		if (alt)
			add_breakpoint(child, dbg, alt);

		/*
		 * Note that we ignore the result of setting the above
		 * breakpoint since it may fail.  When it does, this is
		 * not so much an error, but a forewarning that we may
		 * be receiving a prefetch abort shortly.
		 *
		 * If we don't set this breakpoint here, then we can
		 * lose control of the thread during single stepping.
		 */
		if (!alt || predicate(insn) != PREDICATE_ALWAYS)
			add_breakpoint(child, dbg, pc + 4);
	}
}

/*
 * Ensure no single-step breakpoint is pending.  Returns non-zero
 * value if child was being single-stepped.
 */
void ptrace_cancel_bpt(struct task_struct *child)
{
	int i, nsaved = child->thread.debug.nsaved;

	child->thread.debug.nsaved = 0;

	if (nsaved > 2) {
		printk("ptrace_cancel_bpt: bogus nsaved: %d!\n", nsaved);
		nsaved = 2;
	}

	for (i = 0; i < nsaved; i++)
		clear_breakpoint(child, &child->thread.debug.bp[i]);
}

/*
 * Called by kernel/ptrace.c when detaching..
 */
void ptrace_disable(struct task_struct *child)
{
	single_step_disable(child);
}

/*
 * Handle hitting a breakpoint.
 */
void ptrace_break(struct task_struct *tsk, struct pt_regs *regs)
{
	siginfo_t info;

	ptrace_cancel_bpt(tsk);

	info.si_signo = SIGTRAP;
	info.si_errno = 0;
	info.si_code  = TRAP_BRKPT;
	info.si_addr  = (void __user *)instruction_pointer(regs);

	force_sig_info(SIGTRAP, &info, tsk);
}

static int break_trap(struct pt_regs *regs, unsigned int instr)
{
	ptrace_break(current, regs);
	return 0;
}

static struct undef_hook arm_break_hook = {
	.instr_mask	= 0x0fffffff,
	.instr_val	= 0x07f001f0,
	.cpsr_mask	= PSR_T_BIT,
	.cpsr_val	= 0,
	.fn		= break_trap,
};

static struct undef_hook thumb_break_hook = {
	.instr_mask	= 0xffff,
	.instr_val	= 0xde01,
	.cpsr_mask	= PSR_T_BIT,
	.cpsr_val	= PSR_T_BIT,
	.fn		= break_trap,
};

static int __init ptrace_break_init(void)
{
	register_undef_hook(&arm_break_hook);
	register_undef_hook(&thumb_break_hook);
	return 0;
}

core_initcall(ptrace_break_init);

/*
 * Read the word at offset "off" into the "struct user".  We
 * actually access the pt_regs stored on the kernel stack.
 */
static int ptrace_read_user(struct task_struct *tsk, unsigned long off,
			    unsigned long __user *ret)
{
	unsigned long tmp;

	if (off & 3 || off >= sizeof(struct user))
		return -EIO;

	tmp = 0;
	if (off < sizeof(struct pt_regs))
		tmp = get_user_reg(tsk, off >> 2);

	return put_user(tmp, ret);
}

/*
 * Write the word at offset "off" into "struct user".  We
 * actually access the pt_regs stored on the kernel stack.
 */
static int ptrace_write_user(struct task_struct *tsk, unsigned long off,
			     unsigned long val)
{
	if (off & 3 || off >= sizeof(struct user))
		return -EIO;

	if (off >= sizeof(struct pt_regs))
		return 0;

	return put_user_reg(tsk, off >> 2, val);
}

/*
 * Get all user integer registers.
 */
static int ptrace_getregs(struct task_struct *tsk, void __user *uregs)
{
	struct pt_regs *regs = task_pt_regs(tsk);

	return copy_to_user(uregs, regs, sizeof(struct pt_regs)) ? -EFAULT : 0;
}

/*
 * Set all user integer registers.
 */
static int ptrace_setregs(struct task_struct *tsk, void __user *uregs)
{
	struct pt_regs newregs;
	int ret;

	ret = -EFAULT;
	if (copy_from_user(&newregs, uregs, sizeof(struct pt_regs)) == 0) {
		struct pt_regs *regs = task_pt_regs(tsk);

		ret = -EINVAL;
		if (valid_user_regs(&newregs)) {
			*regs = newregs;
			ret = 0;
		}
	}

	return ret;
}

/*
 * Get the child FPU state.
 */
static int ptrace_getfpregs(struct task_struct *tsk, void __user *ufp)
{
	return copy_to_user(ufp, &task_thread_info(tsk)->fpstate,
			    sizeof(struct user_fp)) ? -EFAULT : 0;
}

/*
 * Set the child FPU state.
 */
static int ptrace_setfpregs(struct task_struct *tsk, void __user *ufp)
{
	struct thread_info *thread = task_thread_info(tsk);
	thread->used_cp[1] = thread->used_cp[2] = 1;
	return copy_from_user(&thread->fpstate, ufp,
			      sizeof(struct user_fp)) ? -EFAULT : 0;
}

#ifdef CONFIG_IWMMXT

/*
 * Get the child iWMMXt state.
 */
static int ptrace_getwmmxregs(struct task_struct *tsk, void __user *ufp)
{
	struct thread_info *thread = task_thread_info(tsk);

	if (!test_ti_thread_flag(thread, TIF_USING_IWMMXT))
		return -ENODATA;
	iwmmxt_task_disable(thread);  /* force it to ram */
	return copy_to_user(ufp, &thread->fpstate.iwmmxt, IWMMXT_SIZE)
		? -EFAULT : 0;
}

/*
 * Set the child iWMMXt state.
 */
static int ptrace_setwmmxregs(struct task_struct *tsk, void __user *ufp)
{
	struct thread_info *thread = task_thread_info(tsk);

	if (!test_ti_thread_flag(thread, TIF_USING_IWMMXT))
		return -EACCES;
	iwmmxt_task_release(thread);  /* force a reload */
	return copy_from_user(&thread->fpstate.iwmmxt, ufp, IWMMXT_SIZE)
		? -EFAULT : 0;
}

#endif

#ifdef CONFIG_CRUNCH
/*
 * Get the child Crunch state.
 */
static int ptrace_getcrunchregs(struct task_struct *tsk, void __user *ufp)
{
	struct thread_info *thread = task_thread_info(tsk);

	crunch_task_disable(thread);  /* force it to ram */
	return copy_to_user(ufp, &thread->crunchstate, CRUNCH_SIZE)
		? -EFAULT : 0;
}

/*
 * Set the child Crunch state.
 */
static int ptrace_setcrunchregs(struct task_struct *tsk, void __user *ufp)
{
	struct thread_info *thread = task_thread_info(tsk);

	crunch_task_release(thread);  /* force a reload */
	return copy_from_user(&thread->crunchstate, ufp, CRUNCH_SIZE)
		? -EFAULT : 0;
}
#endif

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

	switch (request) {
		/*
		 * read word at location "addr" in the child process.
		 */
		case PTRACE_PEEKTEXT:
		case PTRACE_PEEKDATA:
			ret = generic_ptrace_peekdata(child, addr, data);
			break;

		case PTRACE_PEEKUSR:
			ret = ptrace_read_user(child, addr, (unsigned long __user *)data);
			break;

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

		case PTRACE_POKEUSR:
			ret = ptrace_write_user(child, addr, data);
			break;

		/*
		 * continue/restart and stop at next (return from) syscall
		 */
		case PTRACE_SYSCALL:
		case PTRACE_CONT:
			ret = -EIO;
			if (!valid_signal(data))
				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;
			single_step_disable(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:
			single_step_disable(child);
			if (child->exit_state != EXIT_ZOMBIE) {
				child->exit_code = SIGKILL;
				wake_up_process(child);
			}
			ret = 0;
			break;

		/*
		 * execute single instruction.
		 */
		case PTRACE_SINGLESTEP:
			ret = -EIO;
			if (!valid_signal(data))
				break;
			single_step_enable(child);
			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
			child->exit_code = data;
			/* give it a chance to run. */
			wake_up_process(child);
			ret = 0;
			break;

		case PTRACE_GETREGS:
			ret = ptrace_getregs(child, (void __user *)data);
			break;

		case PTRACE_SETREGS:
			ret = ptrace_setregs(child, (void __user *)data);
			break;

		case PTRACE_GETFPREGS:
			ret = ptrace_getfpregs(child, (void __user *)data);
			break;
		
		case PTRACE_SETFPREGS:
			ret = ptrace_setfpregs(child, (void __user *)data);
			break;

#ifdef CONFIG_IWMMXT
		case PTRACE_GETWMMXREGS:
			ret = ptrace_getwmmxregs(child, (void __user *)data);
			break;

		case PTRACE_SETWMMXREGS:
			ret = ptrace_setwmmxregs(child, (void __user *)data);
			break;
#endif

		case PTRACE_GET_THREAD_AREA:
			ret = put_user(task_thread_info(child)->tp_value,
				       (unsigned long __user *) data);
			break;

		case PTRACE_SET_SYSCALL:
			task_thread_info(child)->syscall = data;
			ret = 0;
			break;

#ifdef CONFIG_CRUNCH
		case PTRACE_GETCRUNCHREGS:
			ret = ptrace_getcrunchregs(child, (void __user *)data);
			break;

		case PTRACE_SETCRUNCHREGS:
			ret = ptrace_setcrunchregs(child, (void __user *)data);
			break;
#endif

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

	return ret;
}

asmlinkage int syscall_trace(int why, struct pt_regs *regs, int scno)
{
	unsigned long ip;

	if (!test_thread_flag(TIF_SYSCALL_TRACE))
		return scno;
	if (!(current->ptrace & PT_PTRACED))
		return scno;

	/*
	 * Save IP.  IP is used to denote syscall entry/exit:
	 *  IP = 0 -> entry, = 1 -> exit
	 */
	ip = regs->ARM_ip;
	regs->ARM_ip = why;

	current_thread_info()->syscall = scno;

	/* 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;
	}
	regs->ARM_ip = ip;

	return current_thread_info()->syscall;
}