signal.c

linux 2.6.19 kernel source code before patching

/*
 * This must be called with current->sighand->siglock held.
 *
 * This should be the path for all ptrace stops.
 * We always set current->last_siginfo while stopped here.
 * That makes it a way to test a stopped process for
 * being ptrace-stopped vs being job-control-stopped.
 *
 * If we actually decide not to stop at all because the tracer is gone,
 * we leave nostop_code in current->exit_code.
 */
static void ptrace_stop(int exit_code, int nostop_code, siginfo_t *info)
{
	/*
	 * If there is a group stop in progress,
	 * we must participate in the bookkeeping.
	 */
	if (current->signal->group_stop_count > 0)
		--current->signal->group_stop_count;

	current->last_siginfo = info;
	current->exit_code = exit_code;

	/* Let the debugger run.  */
	set_current_state(TASK_TRACED);
	spin_unlock_irq(&current->sighand->siglock);
	try_to_freeze();
	read_lock(&tasklist_lock);
	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 stop here.
		 */
		read_unlock(&tasklist_lock);
		set_current_state(TASK_RUNNING);
		current->exit_code = nostop_code;
	}

	/*
	 * 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 = current->pid;
	info.si_uid = current->uid;

	/* Let the debugger run.  */
	spin_lock_irq(&current->sighand->siglock);
	ptrace_stop(exit_code, 0, &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 (stop_count == 0 || (current->ptrace & PT_PTRACED)) {
		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 (!likely(sig->flags & SIGNAL_STOP_DEQUEUED))
		return 0;

	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 {
		/*
		 * There is no group stop already in progress.
		 * We must initiate one now.
		 */
		struct task_struct *t;

		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->exit_state &&
			    !(t->state & (TASK_STOPPED|TASK_TRACED))) {
				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;
}

/*
 * Do appropriate magic when group_stop_count > 0.
 * We return nonzero if we stopped, after releasing the siglock.
 * We return zero if we still hold the siglock and should look
 * for another signal without checking group_stop_count again.
 */
static int handle_group_stop(void)
{
	int stop_count;

	if (current->signal->group_exit_task == current) {
		/*
		 * Group stop is so we can do a core dump,
		 * We are the initiating thread, so get on with it.
		 */
		current->signal->group_exit_task = NULL;
		return 0;
	}

	if (current->signal->flags & SIGNAL_GROUP_EXIT)
		/*
		 * Group stop is so another thread can do a core dump,
		 * or else we are racing against a death signal.
		 * Just punt the stop so we can get the next signal.
		 */
		return 0;

	/*
	 * There is a group stop in progress.  We stop
	 * without any associated signal being in our queue.
	 */
	stop_count = --current->signal->group_stop_count;
	if (stop_count == 0)
		current->signal->flags = SIGNAL_STOP_STOPPED;
	current->exit_code = current->signal->group_exit_code;
	set_current_state(TASK_STOPPED);
	spin_unlock_irq(&current->sighand->siglock);
	finish_stop(stop_count);
	return 1;
}

int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka,
			  struct pt_regs *regs, void *cookie)
{
	sigset_t *mask = &current->blocked;
	int signr = 0;

	try_to_freeze();

relock:
	spin_lock_irq(&current->sighand->siglock);
	for (;;) {
		struct k_sigaction *ka;

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

		signr = dequeue_signal(current, mask, info);

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

		if ((current->ptrace & PT_PTRACED) && signr != SIGKILL) {
			ptrace_signal_deliver(regs, cookie);

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

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

			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 = current->parent->pid;
				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);
				continue;
			}
		}

		ka = &current->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;

		/*
		 * Init of a pid space gets no signals it doesn't want from
		 * within that pid space. It can of course get signals from
		 * its parent pid space.
		 */
		if (current == child_reaper(current))
			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(&current->sighand->siglock);

				/* signals can be posted during this window */

				if (is_current_pgrp_orphaned())
					goto relock;

				spin_lock_irq(&current->sighand->siglock);
			}

			if (likely(do_signal_stop(signr))) {
				/* 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(&current->sighand->siglock);

		/*
		 * Anything else is fatal, maybe with a core dump.
		 */
		current->flags |= PF_SIGNALED;
		if (sig_kernel_coredump(signr)) {
			/*
			 * 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((long)signr, signr, regs);
		}

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

EXPORT_SYMBOL(recalc_sigpending);
EXPORT_SYMBOL_GPL(dequeue_signal);
EXPORT_SYMBOL(flush_signals);
EXPORT_SYMBOL(force_sig);
EXPORT_SYMBOL(kill_proc);
EXPORT_SYMBOL(ptrace_notify);
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)))
		return -EFAULT;
	if (from->si_code < 0)
		return __copy_to_user(to, from, sizeof(siginfo_t))
			? -EFAULT : 0;
	/*
	 * If you change siginfo_t structure, please be sure
	 * this code is fixed accordingly.
	 * Please remember to update the signalfd_copyinfo() function
	 * inside fs/signalfd.c too, in case siginfo_t changes.
	 * It should never copy any pad contained in the structure
	 * to avoid security leaks, but must copy the generic
	 * 3 ints plus the relevant union member.
	 */
	err = __put_user(from->si_signo, &to->si_signo);
	err |= __put_user(from->si_errno, &to->si_errno);
	err |= __put_user((short)from->si_code, &to->si_code);
	switch (from->si_code & __SI_MASK) {
	case __SI_KILL:
		err |= __put_user(from->si_pid, &to->si_pid);
		err |= __put_user(from->si_uid, &to->si_uid);
		break;
	case __SI_TIMER:
		 err |= __put_user(from->si_tid, &to->si_tid);
		 err |= __put_user(from->si_overrun, &to->si_overrun);
		 err |= __put_user(from->si_ptr, &to->si_ptr);
		break;
	case __SI_POLL:
		err |= __put_user(from->si_band, &to->si_band);
		err |= __put_user(from->si_fd, &to->si_fd);
		break;
	case __SI_FAULT:
		err |= __put_user(from->si_addr, &to->si_addr);
#ifdef __ARCH_SI_TRAPNO
		err |= __put_user(from->si_trapno, &to->si_trapno);