path: root/kernel/ptrace.c

/*
 * linux/kernel/ptrace.c
 *
 * (C) Copyright 1999 Linus Torvalds
 *
 * Common interfaces for "ptrace()" which we do not want
 * to continually duplicate across every architecture.
 */

#include <linux/capability.h>
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/ptrace.h>
#include <linux/security.h>
#include <linux/signal.h>
#include <linux/audit.h>
#include <linux/pid_namespace.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>
#include <linux/regset.h>
#include <linux/hw_breakpoint.h>
#include <linux/cn_proc.h>


static int ptrace_trapping_sleep_fn(void *flags)
{
	schedule();
	return 0;
}

/*
 * ptrace a task: make the debugger its new parent and
 * move it to the ptrace list.
 *
 * Must be called with the tasklist lock write-held.
 */
void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
{
	BUG_ON(!list_empty(&child->ptrace_entry));
	list_add(&child->ptrace_entry, &new_parent->ptraced);
	child->parent = new_parent;
}

/**
 * __ptrace_unlink - unlink ptracee and restore its execution state
 * @child: ptracee to be unlinked
 *
 * Remove @child from the ptrace list, move it back to the original parent,
 * and restore the execution state so that it conforms to the group stop
 * state.
 *
 * Unlinking can happen via two paths - explicit PTRACE_DETACH or ptracer
 * exiting.  For PTRACE_DETACH, unless the ptracee has been killed between
 * ptrace_check_attach() and here, it's guaranteed to be in TASK_TRACED.
 * If the ptracer is exiting, the ptracee can be in any state.
 *
 * After detach, the ptracee should be in a state which conforms to the
 * group stop.  If the group is stopped or in the process of stopping, the
 * ptracee should be put into TASK_STOPPED; otherwise, it should be woken
 * up from TASK_TRACED.
 *
 * If the ptracee is in TASK_TRACED and needs to be moved to TASK_STOPPED,
 * it goes through TRACED -> RUNNING -> STOPPED transition which is similar
 * to but in the opposite direction of what happens while attaching to a
 * stopped task.  However, in this direction, the intermediate RUNNING
 * state is not hidden even from the current ptracer and if it immediately
 * re-attaches and performs a WNOHANG wait(2), it may fail.
 *
 * CONTEXT:
 * write_lock_irq(tasklist_lock)
 */
void __ptrace_unlink(struct task_struct *child)
{
	BUG_ON(!child->ptrace);

	child->ptrace = 0;
	child->parent = child->real_parent;
	list_del_init(&child->ptrace_entry);

	spin_lock(&child->sighand->siglock);

	/*
	 * Clear all pending traps and TRAPPING.  TRAPPING should be
	 * cleared regardless of JOBCTL_STOP_PENDING.  Do it explicitly.
	 */
	task_clear_jobctl_pending(child, JOBCTL_TRAP_MASK);
	task_clear_jobctl_trapping(child);

	/*
	 * Reinstate JOBCTL_STOP_PENDING if group stop is in effect and
	 * @child isn't dead.
	 */
	if (!(child->flags & PF_EXITING) &&
	    (child->signal->flags & SIGNAL_STOP_STOPPED ||
	     child->signal->group_stop_count)) {
		child->jobctl |= JOBCTL_STOP_PENDING;

		/*
		 * This is only possible if this thread was cloned by the
		 * traced task running in the stopped group, set the signal
		 * for the future reports.
		 * FIXME: we should change ptrace_init_task() to handle this
		 * case.
		 */
		if (!(child->jobctl & JOBCTL_STOP_SIGMASK))
			child->jobctl |= SIGSTOP;
	}

	/*
	 * If transition to TASK_STOPPED is pending or in TASK_TRACED, kick
	 * @child in the butt.  Note that @resume should be used iff @child
	 * is in TASK_TRACED; otherwise, we might unduly disrupt
	 * TASK_KILLABLE sleeps.
	 */
	if (child->jobctl & JOBCTL_STOP_PENDING || task_is_traced(child))
		ptrace_signal_wake_up(child, true);

	spin_unlock(&child->sighand->siglock);
}

/* Ensure that nothing can wake it up, even SIGKILL */
static bool ptrace_freeze_traced(struct task_struct *task)
{
	bool ret = false;

	/* Lockless, nobody but us can set this flag */
	if (task->jobctl & JOBCTL_LISTENING)
		return ret;

	spin_lock_irq(&task->sighand->siglock);
	if (task_is_traced(task) && !__fatal_signal_pending(task)) {
		task->state = __TASK_TRACED;
		ret = true;
	}
	spin_unlock_irq(&task->sighand->siglock);

	return ret;
}

static void ptrace_unfreeze_traced(struct task_struct *task)
{
	if (task->state != __TASK_TRACED)
		return;

	WARN_ON(!task->ptrace || task->parent != current);

	spin_lock_irq(&task->sighand->siglock);
	if (__fatal_signal_pending(task))
		wake_up_state(task, __TASK_TRACED);
	else
		task->state = TASK_TRACED;
	spin_unlock_irq(&task->sighand->siglock);
}

/**
 * ptrace_check_attach - check whether ptracee is ready for ptrace operation
 * @child: ptracee to check for
 * @ignore_state: don't check whether @child is currently %TASK_TRACED
 *
 * Check whether @child is being ptraced by %current and ready for further
 * ptrace operations.  If @ignore_state is %false, @child also should be in
 * %TASK_TRACED state and on return the child is guaranteed to be traced
 * and not executing.  If @ignore_state is %true, @child can be in any
 * state.
 *
 * CONTEXT:
 * Grabs and releases tasklist_lock and @child->sighand->siglock.
 *
 * RETURNS:
 * 0 on success, -ESRCH if %child is not ready.
 */
int ptrace_check_attach(struct task_struct *child, bool