signal.c

Kernel code of linux kernel

	if (may_ptrace_stop()) {
		do_notify_parent_cldstop(current, CLD_TRAPPED);
		read_unlock(&tasklist_lock);
		schedule();
	} else {
		/*
		 * By the time we got the lock, our tracer went away.
		 * Don't drop the lock yet, another tracer may come.
		 */
		__set_current_state(TASK_RUNNING);
		if (clear_code)
			current->exit_code = 0;
		read_unlock(&tasklist_lock);
	}

	/*
	 * While in TASK_TRACED, we were considered "frozen enough".
	 * Now that we woke up, it's crucial if we're supposed to be
	 * frozen that we freeze now before running anything substantial.
	 */
	try_to_freeze();

	/*
	 * We are back.  Now reacquire the siglock before touching
	 * last_siginfo, so that we are sure to have synchronized with
	 * any signal-sending on another CPU that wants to examine it.
	 */
	spin_lock_irq(&current->sighand->siglock);
	current->last_siginfo = NULL;

	/*
	 * Queued signals ignored us while we were stopped for tracing.
	 * So check for any that we should take before resuming user mode.
	 * This sets TIF_SIGPENDING, but never clears it.
	 */
	recalc_sigpending_tsk(current);
}

void ptrace_notify(int exit_code)
{
	siginfo_t info;

	BUG_ON((exit_code & (0x7f | ~0xffff)) != SIGTRAP);

	memset(&info, 0, sizeof info);
	info.si_signo = SIGTRAP;
	info.si_code = exit_code;
	info.si_pid = task_pid_vnr(current);
	info.si_uid = current->uid;

	/* Let the debugger run.  */
	spin_lock_irq(&current->sighand->siglock);
	ptrace_stop(exit_code, 1, &info);
	spin_unlock_irq(&current->sighand->siglock);
}

static void
finish_stop(int stop_count)
{
	/*
	 * If there are no other threads in the group, or if there is
	 * a group stop in progress and we are the last to stop,
	 * report to the parent.  When ptraced, every thread reports itself.
	 */
	if (tracehook_notify_jctl(stop_count == 0, CLD_STOPPED)) {
		read_lock(&tasklist_lock);
		do_notify_parent_cldstop(current, CLD_STOPPED);
		read_unlock(&tasklist_lock);
	}

	do {
		schedule();
	} while (try_to_freeze());
	/*
	 * Now we don't run again until continued.
	 */
	current->exit_code = 0;
}

/*
 * This performs the stopping for SIGSTOP and other stop signals.
 * We have to stop all threads in the thread group.
 * Returns nonzero if we've actually stopped and released the siglock.
 * Returns zero if we didn't stop and still hold the siglock.
 */
static int do_signal_stop(int signr)
{
	struct signal_struct *sig = current->signal;
	int stop_count;

	if (sig->group_stop_count > 0) {
		/*
		 * There is a group stop in progress.  We don't need to
		 * start another one.
		 */
		stop_count = --sig->group_stop_count;
	} else {
		struct task_struct *t;

		if (!likely(sig->flags & SIGNAL_STOP_DEQUEUED) ||
		    unlikely(signal_group_exit(sig)))
			return 0;
		/*
		 * There is no group stop already in progress.
		 * We must initiate one now.
		 */
		sig->group_exit_code = signr;

		stop_count = 0;
		for (t = next_thread(current); t != current; t = next_thread(t))
			/*
			 * Setting state to TASK_STOPPED for a group
			 * stop is always done with the siglock held,
			 * so this check has no races.
			 */
			if (!(t->flags & PF_EXITING) &&
			    !task_is_stopped_or_traced(t)) {
				stop_count++;
				signal_wake_up(t, 0);
			}
		sig->group_stop_count = stop_count;
	}

	if (stop_count == 0)
		sig->flags = SIGNAL_STOP_STOPPED;
	current->exit_code = sig->group_exit_code;
	__set_current_state(TASK_STOPPED);

	spin_unlock_irq(&current->sighand->siglock);
	finish_stop(stop_count);
	return 1;
}

static int ptrace_signal(int signr, siginfo_t *info,
			 struct pt_regs *regs, void *cookie)
{
	if (!(current->ptrace & PT_PTRACED))
		return signr;

	ptrace_signal_deliver(regs, cookie);

	/* Let the debugger run.  */
	ptrace_stop(signr, 0, info);

	/* We're back.  Did the debugger cancel the sig?  */
	signr = current->exit_code;
	if (signr == 0)
		return signr;

	current->exit_code = 0;

	/* Update the siginfo structure if the signal has
	   changed.  If the debugger wanted something
	   specific in the siginfo structure then it should
	   have updated *info via PTRACE_SETSIGINFO.  */
	if (signr != info->si_signo) {
		info->si_signo = signr;
		info->si_errno = 0;
		info->si_code = SI_USER;
		info->si_pid = task_pid_vnr(current->parent);
		info->si_uid = current->parent->uid;
	}

	/* If the (new) signal is now blocked, requeue it.  */
	if (sigismember(&current->blocked, signr)) {
		specific_send_sig_info(signr, info, current);
		signr = 0;
	}

	return signr;
}

int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka,
			  struct pt_regs *regs, void *cookie)
{
	struct sighand_struct *sighand = current->sighand;
	struct signal_struct *signal = current->signal;
	int signr;

relock:
	/*
	 * We'll jump back here after any time we were stopped in TASK_STOPPED.
	 * While in TASK_STOPPED, we were considered "frozen enough".
	 * Now that we woke up, it's crucial if we're supposed to be
	 * frozen that we freeze now before running anything substantial.
	 */
	try_to_freeze();

	spin_lock_irq(&sighand->siglock);
	/*
	 * Every stopped thread goes here after wakeup. Check to see if
	 * we should notify the parent, prepare_signal(SIGCONT) encodes
	 * the CLD_ si_code into SIGNAL_CLD_MASK bits.
	 */
	if (unlikely(signal->flags & SIGNAL_CLD_MASK)) {
		int why = (signal->flags & SIGNAL_STOP_CONTINUED)
				? CLD_CONTINUED : CLD_STOPPED;
		signal->flags &= ~SIGNAL_CLD_MASK;
		spin_unlock_irq(&sighand->siglock);

		if (unlikely(!tracehook_notify_jctl(1, why)))
			goto relock;

		read_lock(&tasklist_lock);
		do_notify_parent_cldstop(current->group_leader, why);
		read_unlock(&tasklist_lock);
		goto relock;
	}

	for (;;) {
		struct k_sigaction *ka;

		if (unlikely(signal->group_stop_count > 0) &&
		    do_signal_stop(0))
			goto relock;

		/*
		 * Tracing can induce an artifical signal and choose sigaction.
		 * The return value in @signr determines the default action,
		 * but @info->si_signo is the signal number we will report.
		 */
		signr = tracehook_get_signal(current, regs, info, return_ka);
		if (unlikely(signr < 0))
			goto relock;
		if (unlikely(signr != 0))
			ka = return_ka;
		else {
			signr = dequeue_signal(current, &current->blocked,
					       info);

			if (!signr)
				break; /* will return 0 */

			if (signr != SIGKILL) {
				signr = ptrace_signal(signr, info,
						      regs, cookie);
				if (!signr)
					continue;
			}

			ka = &sighand->action[signr-1];
		}

		if (ka->sa.sa_handler == SIG_IGN) /* Do nothing.  */
			continue;
		if (ka->sa.sa_handler != SIG_DFL) {
			/* Run the handler.  */
			*return_ka = *ka;

			if (ka->sa.sa_flags & SA_ONESHOT)
				ka->sa.sa_handler = SIG_DFL;

			break; /* will return non-zero "signr" value */
		}

		/*
		 * Now we are doing the default action for this signal.
		 */
		if (sig_kernel_ignore(signr)) /* Default is nothing. */
			continue;

		/*
		 * Global init gets no signals it doesn't want.
		 */
		if (unlikely(signal->flags & SIGNAL_UNKILLABLE) &&
		    !signal_group_exit(signal))
			continue;

		if (sig_kernel_stop(signr)) {
			/*
			 * The default action is to stop all threads in
			 * the thread group.  The job control signals
			 * do nothing in an orphaned pgrp, but SIGSTOP
			 * always works.  Note that siglock needs to be
			 * dropped during the call to is_orphaned_pgrp()
			 * because of lock ordering with tasklist_lock.
			 * This allows an intervening SIGCONT to be posted.
			 * We need to check for that and bail out if necessary.
			 */
			if (signr != SIGSTOP) {
				spin_unlock_irq(&sighand->siglock);

				/* signals can be posted during this window */

				if (is_current_pgrp_orphaned())
					goto relock;

				spin_lock_irq(&sighand->siglock);
			}

			if (likely(do_signal_stop(info->si_signo))) {
				/* It released the siglock.  */
				goto relock;
			}

			/*
			 * We didn't actually stop, due to a race
			 * with SIGCONT or something like that.
			 */
			continue;
		}

		spin_unlock_irq(&sighand->siglock);

		/*
		 * Anything else is fatal, maybe with a core dump.
		 */
		current->flags |= PF_SIGNALED;

		if (sig_kernel_coredump(signr)) {
			if (print_fatal_signals)
				print_fatal_signal(regs, info->si_signo);
			/*
			 * If it was able to dump core, this kills all
			 * other threads in the group and synchronizes with
			 * their demise.  If we lost the race with another
			 * thread getting here, it set group_exit_code
			 * first and our do_group_exit call below will use
			 * that value and ignore the one we pass it.
			 */
			do_coredump(info->si_signo, info->si_signo, regs);
		}

		/*
		 * Death signals, no core dump.
		 */
		do_group_exit(info->si_signo);
		/* NOTREACHED */
	}
	spin_unlock_irq(&sighand->siglock);
	return signr;
}

void exit_signals(struct task_struct *tsk)
{
	int group_stop = 0;
	struct task_struct *t;

	if (thread_group_empty(tsk) || signal_group_exit(tsk->signal)) {
		tsk->flags |= PF_EXITING;
		return;
	}

	spin_lock_irq(&tsk->sighand->siglock);
	/*
	 * From now this task is not visible for group-wide signals,
	 * see wants_signal(), do_signal_stop().
	 */
	tsk->flags |= PF_EXITING;
	if (!signal_pending(tsk))
		goto out;

	/* It could be that __group_complete_signal() choose us to
	 * notify about group-wide signal. Another thread should be
	 * woken now to take the signal since we will not.
	 */
	for (t = tsk; (t = next_thread(t)) != tsk; )
		if (!signal_pending(t) && !(t->flags & PF_EXITING))
			recalc_sigpending_and_wake(t);

	if (unlikely(tsk->signal->group_stop_count) &&
			!--tsk->signal->group_stop_count) {
		tsk->signal->flags = SIGNAL_STOP_STOPPED;
		group_stop = 1;
	}
out:
	spin_unlock_irq(&tsk->sighand->siglock);

	if (unlikely(group_stop) && tracehook_notify_jctl(1, CLD_STOPPED)) {
		read_lock(&tasklist_lock);
		do_notify_parent_cldstop(tsk, CLD_STOPPED);
		read_unlock(&tasklist_lock);
	}
}

EXPORT_SYMBOL(recalc_sigpending);
EXPORT_SYMBOL_GPL(dequeue_signal);
EXPORT_SYMBOL(flush_signals);
EXPORT_SYMBOL(force_sig);
EXPORT_SYMBOL(send_sig);
EXPORT_SYMBOL(send_sig_info);
EXPORT_SYMBOL(sigprocmask);
EXPORT_SYMBOL(block_all_signals);
EXPORT_SYMBOL(unblock_all_signals);


/*
 * System call entry points.
 */

asmlinkage long sys_restart_syscall(void)
{
	struct restart_block *restart = &current_thread_info()->restart_block;
	return restart->fn(restart);
}

long do_no_restart_syscall(struct restart_block *param)
{
	return -EINTR;
}

/*
 * We don't need to get the kernel lock - this is all local to this
 * particular thread.. (and that's good, because this is _heavily_
 * used by various programs)
 */

/*
 * This is also useful for kernel threads that want to temporarily
 * (or permanently) block certain signals.
 *
 * NOTE! Unlike the user-mode sys_sigprocmask(), the kernel
 * interface happily blocks "unblockable" signals like SIGKILL
 * and friends.
 */
int sigprocmask(int how, sigset_t *set, sigset_t *oldset)
{
	int error;

	spin_lock_irq(&current->sighand->siglock);
	if (oldset)
		*oldset = current->blocked;

	error = 0;
	switch (how) {
	case SIG_BLOCK:
		sigorsets(&current->blocked, &current->blocked, set);
		break;
	case SIG_UNBLOCK:
		signandsets(&current->blocked, &current->blocked, set);
		break;
	case SIG_SETMASK:
		current->blocked = *set;
		break;
	default:
		error = -EINVAL;
	}
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);

	return error;
}

asmlinkage long
sys_rt_sigprocmask(int how, sigset_t __user *set, sigset_t __user *oset, size_t sigsetsize)
{
	int error = -EINVAL;
	sigset_t old_set, new_set;

	/* XXX: Don't preclude handling different sized sigset_t's.  */
	if (sigsetsize != sizeof(sigset_t))
		goto out;

	if (set) {
		error = -EFAULT;
		if (copy_from_user(&new_set, set, sizeof(*set)))
			goto out;
		sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));

		error = sigprocmask(how, &new_set, &old_set);
		if (error)
			goto out;
		if (oset)
			goto set_old;
	} else if (oset) {
		spin_lock_irq(&current->sighand->siglock);
		old_set = current->blocked;
		spin_unlock_irq(&current->sighand->siglock);

	set_old:
		error = -EFAULT;
		if (copy_to_user(oset, &old_set, sizeof(*oset)))
			goto out;
	}
	error = 0;
out:
	return error;
}

long do_sigpending(void __user *set, unsigned long sigsetsize)
{
	long error = -EINVAL;
	sigset_t pending;

	if (sigsetsize > sizeof(sigset_t))
		goto out;

	spin_lock_irq(&current->sighand->siglock);
	sigorsets(&pending, &current->pending.signal,
		  &current->signal->shared_pending.signal);
	spin_unlock_irq(&current->sighand->siglock);

	/* Outside the lock because only this thread touches it.  */
	sigandsets(&pending, &current->blocked, &pending);

	error = -EFAULT;
	if (!copy_to_user(set, &pending, sigsetsize))
		error = 0;

out:
	return error;
}	

asmlinkage long
sys_rt_sigpending(sigset_t __user *set, size_t sigsetsize)
{
	return do_sigpending(set, sigsetsize);
}

#ifndef HAVE_ARCH_COPY_SIGINFO_TO_USER

int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from)
{
	int err;

	if (!access_ok (VERIFY_WRITE, to, sizeof(siginfo_t)))