2 * linux/kernel/signal.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * 1997-11-02 Modified for POSIX.1b signals by Richard Henderson
8 * 2003-06-02 Jim Houston - Concurrent Computer Corp.
9 * Changes to use preallocated sigqueue structures
10 * to allow signals to be sent reliably.
13 #include <linux/slab.h>
14 #include <linux/export.h>
15 #include <linux/init.h>
16 #include <linux/sched.h>
18 #include <linux/tty.h>
19 #include <linux/binfmts.h>
20 #include <linux/security.h>
21 #include <linux/syscalls.h>
22 #include <linux/ptrace.h>
23 #include <linux/signal.h>
24 #include <linux/signalfd.h>
25 #include <linux/ratelimit.h>
26 #include <linux/tracehook.h>
27 #include <linux/capability.h>
28 #include <linux/freezer.h>
29 #include <linux/pid_namespace.h>
30 #include <linux/nsproxy.h>
31 #define CREATE_TRACE_POINTS
32 #include <trace/events/signal.h>
34 #include <asm/param.h>
35 #include <asm/uaccess.h>
36 #include <asm/unistd.h>
37 #include <asm/siginfo.h>
38 #include "audit.h" /* audit_signal_info() */
41 * SLAB caches for signal bits.
44 static struct kmem_cache *sigqueue_cachep;
46 int print_fatal_signals __read_mostly;
48 static void __user *sig_handler(struct task_struct *t, int sig)
50 return t->sighand->action[sig - 1].sa.sa_handler;
53 static int sig_handler_ignored(void __user *handler, int sig)
55 /* Is it explicitly or implicitly ignored? */
56 return handler == SIG_IGN ||
57 (handler == SIG_DFL && sig_kernel_ignore(sig));
60 static int sig_task_ignored(struct task_struct *t, int sig,
65 handler = sig_handler(t, sig);
67 if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) &&
68 handler == SIG_DFL && !from_ancestor_ns)
71 return sig_handler_ignored(handler, sig);
74 static int sig_ignored(struct task_struct *t, int sig, int from_ancestor_ns)
77 * Blocked signals are never ignored, since the
78 * signal handler may change by the time it is
81 if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
84 if (!sig_task_ignored(t, sig, from_ancestor_ns))
88 * Tracers may want to know about even ignored signals.
94 * Re-calculate pending state from the set of locally pending
95 * signals, globally pending signals, and blocked signals.
97 static inline int has_pending_signals(sigset_t *signal, sigset_t *blocked)
102 switch (_NSIG_WORDS) {
104 for (i = _NSIG_WORDS, ready = 0; --i >= 0 ;)
105 ready |= signal->sig[i] &~ blocked->sig[i];
108 case 4: ready = signal->sig[3] &~ blocked->sig[3];
109 ready |= signal->sig[2] &~ blocked->sig[2];
110 ready |= signal->sig[1] &~ blocked->sig[1];
111 ready |= signal->sig[0] &~ blocked->sig[0];
114 case 2: ready = signal->sig[1] &~ blocked->sig[1];
115 ready |= signal->sig[0] &~ blocked->sig[0];
118 case 1: ready = signal->sig[0] &~ blocked->sig[0];
123 #define PENDING(p,b) has_pending_signals(&(p)->signal, (b))
125 static int recalc_sigpending_tsk(struct task_struct *t)
127 if ((t->jobctl & JOBCTL_PENDING_MASK) ||
128 PENDING(&t->pending, &t->blocked) ||
129 PENDING(&t->signal->shared_pending, &t->blocked)) {
130 set_tsk_thread_flag(t, TIF_SIGPENDING);
134 * We must never clear the flag in another thread, or in current
135 * when it's possible the current syscall is returning -ERESTART*.
136 * So we don't clear it here, and only callers who know they should do.
142 * After recalculating TIF_SIGPENDING, we need to make sure the task wakes up.
143 * This is superfluous when called on current, the wakeup is a harmless no-op.
145 void recalc_sigpending_and_wake(struct task_struct *t)
147 if (recalc_sigpending_tsk(t))
148 signal_wake_up(t, 0);
151 void recalc_sigpending(void)
153 if (!recalc_sigpending_tsk(current) && !freezing(current))
154 clear_thread_flag(TIF_SIGPENDING);
158 /* Given the mask, find the first available signal that should be serviced. */
160 #define SYNCHRONOUS_MASK \
161 (sigmask(SIGSEGV) | sigmask(SIGBUS) | sigmask(SIGILL) | \
162 sigmask(SIGTRAP) | sigmask(SIGFPE))
164 int next_signal(struct sigpending *pending, sigset_t *mask)
166 unsigned long i, *s, *m, x;
169 s = pending->signal.sig;
173 * Handle the first word specially: it contains the
174 * synchronous signals that need to be dequeued first.
178 if (x & SYNCHRONOUS_MASK)
179 x &= SYNCHRONOUS_MASK;
184 switch (_NSIG_WORDS) {
186 for (i = 1; i < _NSIG_WORDS; ++i) {
190 sig = ffz(~x) + i*_NSIG_BPW + 1;
199 sig = ffz(~x) + _NSIG_BPW + 1;
210 static inline void print_dropped_signal(int sig)
212 static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
214 if (!print_fatal_signals)
217 if (!__ratelimit(&ratelimit_state))
220 printk(KERN_INFO "%s/%d: reached RLIMIT_SIGPENDING, dropped signal %d\n",
221 current->comm, current->pid, sig);
225 * task_set_jobctl_pending - set jobctl pending bits
227 * @mask: pending bits to set
229 * Clear @mask from @task->jobctl. @mask must be subset of
230 * %JOBCTL_PENDING_MASK | %JOBCTL_STOP_CONSUME | %JOBCTL_STOP_SIGMASK |
231 * %JOBCTL_TRAPPING. If stop signo is being set, the existing signo is
232 * cleared. If @task is already being killed or exiting, this function
236 * Must be called with @task->sighand->siglock held.
239 * %true if @mask is set, %false if made noop because @task was dying.
241 bool task_set_jobctl_pending(struct task_struct *task, unsigned int mask)
243 BUG_ON(mask & ~(JOBCTL_PENDING_MASK | JOBCTL_STOP_CONSUME |
244 JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING));
245 BUG_ON((mask & JOBCTL_TRAPPING) && !(mask & JOBCTL_PENDING_MASK));
247 if (unlikely(fatal_signal_pending(task) || (task->flags & PF_EXITING)))
250 if (mask & JOBCTL_STOP_SIGMASK)
251 task->jobctl &= ~JOBCTL_STOP_SIGMASK;
253 task->jobctl |= mask;
258 * task_clear_jobctl_trapping - clear jobctl trapping bit
261 * If JOBCTL_TRAPPING is set, a ptracer is waiting for us to enter TRACED.
262 * Clear it and wake up the ptracer. Note that we don't need any further
263 * locking. @task->siglock guarantees that @task->parent points to the
267 * Must be called with @task->sighand->siglock held.
269 void task_clear_jobctl_trapping(struct task_struct *task)
271 if (unlikely(task->jobctl & JOBCTL_TRAPPING)) {
272 task->jobctl &= ~JOBCTL_TRAPPING;
273 wake_up_bit(&task->jobctl, JOBCTL_TRAPPING_BIT);
278 * task_clear_jobctl_pending - clear jobctl pending bits
280 * @mask: pending bits to clear
282 * Clear @mask from @task->jobctl. @mask must be subset of
283 * %JOBCTL_PENDING_MASK. If %JOBCTL_STOP_PENDING is being cleared, other
284 * STOP bits are cleared together.
286 * If clearing of @mask leaves no stop or trap pending, this function calls
287 * task_clear_jobctl_trapping().
290 * Must be called with @task->sighand->siglock held.
292 void task_clear_jobctl_pending(struct task_struct *task, unsigned int mask)
294 BUG_ON(mask & ~JOBCTL_PENDING_MASK);
296 if (mask & JOBCTL_STOP_PENDING)
297 mask |= JOBCTL_STOP_CONSUME | JOBCTL_STOP_DEQUEUED;
299 task->jobctl &= ~mask;
301 if (!(task->jobctl & JOBCTL_PENDING_MASK))
302 task_clear_jobctl_trapping(task);
306 * task_participate_group_stop - participate in a group stop
307 * @task: task participating in a group stop
309 * @task has %JOBCTL_STOP_PENDING set and is participating in a group stop.
310 * Group stop states are cleared and the group stop count is consumed if
311 * %JOBCTL_STOP_CONSUME was set. If the consumption completes the group
312 * stop, the appropriate %SIGNAL_* flags are set.
315 * Must be called with @task->sighand->siglock held.
318 * %true if group stop completion should be notified to the parent, %false
321 static bool task_participate_group_stop(struct task_struct *task)
323 struct signal_struct *sig = task->signal;
324 bool consume = task->jobctl & JOBCTL_STOP_CONSUME;
326 WARN_ON_ONCE(!(task->jobctl & JOBCTL_STOP_PENDING));
328 task_clear_jobctl_pending(task, JOBCTL_STOP_PENDING);
333 if (!WARN_ON_ONCE(sig->group_stop_count == 0))
334 sig->group_stop_count--;
337 * Tell the caller to notify completion iff we are entering into a
338 * fresh group stop. Read comment in do_signal_stop() for details.
340 if (!sig->group_stop_count && !(sig->flags & SIGNAL_STOP_STOPPED)) {
341 sig->flags = SIGNAL_STOP_STOPPED;
348 * allocate a new signal queue record
349 * - this may be called without locks if and only if t == current, otherwise an
350 * appropriate lock must be held to stop the target task from exiting
352 static struct sigqueue *
353 __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimit)
355 struct sigqueue *q = NULL;
356 struct user_struct *user;
359 * Protect access to @t credentials. This can go away when all
360 * callers hold rcu read lock.
363 user = get_uid(__task_cred(t)->user);
364 atomic_inc(&user->sigpending);
367 if (override_rlimit ||
368 atomic_read(&user->sigpending) <=
369 task_rlimit(t, RLIMIT_SIGPENDING)) {
370 q = kmem_cache_alloc(sigqueue_cachep, flags);
372 print_dropped_signal(sig);
375 if (unlikely(q == NULL)) {
376 atomic_dec(&user->sigpending);
379 INIT_LIST_HEAD(&q->list);
387 static void __sigqueue_free(struct sigqueue *q)
389 if (q->flags & SIGQUEUE_PREALLOC)
391 atomic_dec(&q->user->sigpending);
393 kmem_cache_free(sigqueue_cachep, q);
396 void flush_sigqueue(struct sigpending *queue)
400 sigemptyset(&queue->signal);
401 while (!list_empty(&queue->list)) {
402 q = list_entry(queue->list.next, struct sigqueue , list);
403 list_del_init(&q->list);
409 * Flush all pending signals for a task.
411 void __flush_signals(struct task_struct *t)
413 clear_tsk_thread_flag(t, TIF_SIGPENDING);
414 flush_sigqueue(&t->pending);
415 flush_sigqueue(&t->signal->shared_pending);
418 void flush_signals(struct task_struct *t)
422 spin_lock_irqsave(&t->sighand->siglock, flags);
424 spin_unlock_irqrestore(&t->sighand->siglock, flags);
427 static void __flush_itimer_signals(struct sigpending *pending)
429 sigset_t signal, retain;
430 struct sigqueue *q, *n;
432 signal = pending->signal;
433 sigemptyset(&retain);
435 list_for_each_entry_safe(q, n, &pending->list, list) {
436 int sig = q->info.si_signo;
438 if (likely(q->info.si_code != SI_TIMER)) {
439 sigaddset(&retain, sig);
441 sigdelset(&signal, sig);
442 list_del_init(&q->list);
447 sigorsets(&pending->signal, &signal, &retain);
450 void flush_itimer_signals(void)
452 struct task_struct *tsk = current;
455 spin_lock_irqsave(&tsk->sighand->siglock, flags);
456 __flush_itimer_signals(&tsk->pending);
457 __flush_itimer_signals(&tsk->signal->shared_pending);
458 spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
461 void ignore_signals(struct task_struct *t)
465 for (i = 0; i < _NSIG; ++i)
466 t->sighand->action[i].sa.sa_handler = SIG_IGN;
472 * Flush all handlers for a task.
476 flush_signal_handlers(struct task_struct *t, int force_default)
479 struct k_sigaction *ka = &t->sighand->action[0];
480 for (i = _NSIG ; i != 0 ; i--) {
481 if (force_default || ka->sa.sa_handler != SIG_IGN)
482 ka->sa.sa_handler = SIG_DFL;
484 #ifdef __ARCH_HAS_SA_RESTORER
485 ka->sa.sa_restorer = NULL;
487 sigemptyset(&ka->sa.sa_mask);
492 int unhandled_signal(struct task_struct *tsk, int sig)
494 void __user *handler = tsk->sighand->action[sig-1].sa.sa_handler;
495 if (is_global_init(tsk))
497 if (handler != SIG_IGN && handler != SIG_DFL)
499 /* if ptraced, let the tracer determine */
504 * Notify the system that a driver wants to block all signals for this
505 * process, and wants to be notified if any signals at all were to be
506 * sent/acted upon. If the notifier routine returns non-zero, then the
507 * signal will be acted upon after all. If the notifier routine returns 0,
508 * then then signal will be blocked. Only one block per process is
509 * allowed. priv is a pointer to private data that the notifier routine
510 * can use to determine if the signal should be blocked or not.
513 block_all_signals(int (*notifier)(void *priv), void *priv, sigset_t *mask)
517 spin_lock_irqsave(¤t->sighand->siglock, flags);
518 current->notifier_mask = mask;
519 current->notifier_data = priv;
520 current->notifier = notifier;
521 spin_unlock_irqrestore(¤t->sighand->siglock, flags);
524 /* Notify the system that blocking has ended. */
527 unblock_all_signals(void)
531 spin_lock_irqsave(¤t->sighand->siglock, flags);
532 current->notifier = NULL;
533 current->notifier_data = NULL;
535 spin_unlock_irqrestore(¤t->sighand->siglock, flags);
538 static void collect_signal(int sig, struct sigpending *list, siginfo_t *info)
540 struct sigqueue *q, *first = NULL;
543 * Collect the siginfo appropriate to this signal. Check if
544 * there is another siginfo for the same signal.
546 list_for_each_entry(q, &list->list, list) {
547 if (q->info.si_signo == sig) {
554 sigdelset(&list->signal, sig);
558 list_del_init(&first->list);
559 copy_siginfo(info, &first->info);
560 __sigqueue_free(first);
563 * Ok, it wasn't in the queue. This must be
564 * a fast-pathed signal or we must have been
565 * out of queue space. So zero out the info.
567 info->si_signo = sig;
569 info->si_code = SI_USER;
575 static int __dequeue_signal(struct sigpending *pending, sigset_t *mask,
578 int sig = next_signal(pending, mask);
581 if (current->notifier) {
582 if (sigismember(current->notifier_mask, sig)) {
583 if (!(current->notifier)(current->notifier_data)) {
584 clear_thread_flag(TIF_SIGPENDING);
590 collect_signal(sig, pending, info);
597 * Dequeue a signal and return the element to the caller, which is
598 * expected to free it.
600 * All callers have to hold the siglock.
602 int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
606 /* We only dequeue private signals from ourselves, we don't let
607 * signalfd steal them
609 signr = __dequeue_signal(&tsk->pending, mask, info);
611 signr = __dequeue_signal(&tsk->signal->shared_pending,
616 * itimers are process shared and we restart periodic
617 * itimers in the signal delivery path to prevent DoS
618 * attacks in the high resolution timer case. This is
619 * compliant with the old way of self-restarting
620 * itimers, as the SIGALRM is a legacy signal and only
621 * queued once. Changing the restart behaviour to
622 * restart the timer in the signal dequeue path is
623 * reducing the timer noise on heavy loaded !highres
626 if (unlikely(signr == SIGALRM)) {
627 struct hrtimer *tmr = &tsk->signal->real_timer;
629 if (!hrtimer_is_queued(tmr) &&
630 tsk->signal->it_real_incr.tv64 != 0) {
631 hrtimer_forward(tmr, tmr->base->get_time(),
632 tsk->signal->it_real_incr);
633 hrtimer_restart(tmr);
642 if (unlikely(sig_kernel_stop(signr))) {
644 * Set a marker that we have dequeued a stop signal. Our
645 * caller might release the siglock and then the pending
646 * stop signal it is about to process is no longer in the
647 * pending bitmasks, but must still be cleared by a SIGCONT
648 * (and overruled by a SIGKILL). So those cases clear this
649 * shared flag after we've set it. Note that this flag may
650 * remain set after the signal we return is ignored or
651 * handled. That doesn't matter because its only purpose
652 * is to alert stop-signal processing code when another
653 * processor has come along and cleared the flag.
655 current->jobctl |= JOBCTL_STOP_DEQUEUED;
657 if ((info->si_code & __SI_MASK) == __SI_TIMER && info->si_sys_private) {
659 * Release the siglock to ensure proper locking order
660 * of timer locks outside of siglocks. Note, we leave
661 * irqs disabled here, since the posix-timers code is
662 * about to disable them again anyway.
664 spin_unlock(&tsk->sighand->siglock);
665 do_schedule_next_timer(info);
666 spin_lock(&tsk->sighand->siglock);
672 * Tell a process that it has a new active signal..
674 * NOTE! we rely on the previous spin_lock to
675 * lock interrupts for us! We can only be called with
676 * "siglock" held, and the local interrupt must
677 * have been disabled when that got acquired!
679 * No need to set need_resched since signal event passing
680 * goes through ->blocked
682 void signal_wake_up_state(struct task_struct *t, unsigned int state)
684 set_tsk_thread_flag(t, TIF_SIGPENDING);
686 * TASK_WAKEKILL also means wake it up in the stopped/traced/killable
687 * case. We don't check t->state here because there is a race with it
688 * executing another processor and just now entering stopped state.
689 * By using wake_up_state, we ensure the process will wake up and
690 * handle its death signal.
692 if (!wake_up_state(t, state | TASK_INTERRUPTIBLE))
697 * Remove signals in mask from the pending set and queue.
698 * Returns 1 if any signals were found.
700 * All callers must be holding the siglock.
702 * This version takes a sigset mask and looks at all signals,
703 * not just those in the first mask word.
705 static int rm_from_queue_full(sigset_t *mask, struct sigpending *s)
707 struct sigqueue *q, *n;
710 sigandsets(&m, mask, &s->signal);
711 if (sigisemptyset(&m))
714 sigandnsets(&s->signal, &s->signal, mask);
715 list_for_each_entry_safe(q, n, &s->list, list) {
716 if (sigismember(mask, q->info.si_signo)) {
717 list_del_init(&q->list);
724 * Remove signals in mask from the pending set and queue.
725 * Returns 1 if any signals were found.
727 * All callers must be holding the siglock.
729 static int rm_from_queue(unsigned long mask, struct sigpending *s)
731 struct sigqueue *q, *n;
733 if (!sigtestsetmask(&s->signal, mask))
736 sigdelsetmask(&s->signal, mask);
737 list_for_each_entry_safe(q, n, &s->list, list) {
738 if (q->info.si_signo < SIGRTMIN &&
739 (mask & sigmask(q->info.si_signo))) {
740 list_del_init(&q->list);
747 static inline int is_si_special(const struct siginfo *info)
749 return info <= SEND_SIG_FORCED;
752 static inline bool si_fromuser(const struct siginfo *info)
754 return info == SEND_SIG_NOINFO ||
755 (!is_si_special(info) && SI_FROMUSER(info));
759 * called with RCU read lock from check_kill_permission()
761 static int kill_ok_by_cred(struct task_struct *t)
763 const struct cred *cred = current_cred();
764 const struct cred *tcred = __task_cred(t);
766 if (cred->user->user_ns == tcred->user->user_ns &&
767 (cred->euid == tcred->suid ||
768 cred->euid == tcred->uid ||
769 cred->uid == tcred->suid ||
770 cred->uid == tcred->uid))
773 if (ns_capable(tcred->user->user_ns, CAP_KILL))
780 * Bad permissions for sending the signal
781 * - the caller must hold the RCU read lock
783 static int check_kill_permission(int sig, struct siginfo *info,
784 struct task_struct *t)
789 if (!valid_signal(sig))
792 if (!si_fromuser(info))
795 error = audit_signal_info(sig, t); /* Let audit system see the signal */
799 if (!same_thread_group(current, t) &&
800 !kill_ok_by_cred(t)) {
803 sid = task_session(t);
805 * We don't return the error if sid == NULL. The
806 * task was unhashed, the caller must notice this.
808 if (!sid || sid == task_session(current))
815 return security_task_kill(t, info, sig, 0);
819 * ptrace_trap_notify - schedule trap to notify ptracer
820 * @t: tracee wanting to notify tracer
822 * This function schedules sticky ptrace trap which is cleared on the next
823 * TRAP_STOP to notify ptracer of an event. @t must have been seized by
826 * If @t is running, STOP trap will be taken. If trapped for STOP and
827 * ptracer is listening for events, tracee is woken up so that it can
828 * re-trap for the new event. If trapped otherwise, STOP trap will be
829 * eventually taken without returning to userland after the existing traps
830 * are finished by PTRACE_CONT.
833 * Must be called with @task->sighand->siglock held.
835 static void ptrace_trap_notify(struct task_struct *t)
837 WARN_ON_ONCE(!(t->ptrace & PT_SEIZED));
838 assert_spin_locked(&t->sighand->siglock);
840 task_set_jobctl_pending(t, JOBCTL_TRAP_NOTIFY);
841 ptrace_signal_wake_up(t, t->jobctl & JOBCTL_LISTENING);
845 * Handle magic process-wide effects of stop/continue signals. Unlike
846 * the signal actions, these happen immediately at signal-generation
847 * time regardless of blocking, ignoring, or handling. This does the
848 * actual continuing for SIGCONT, but not the actual stopping for stop
849 * signals. The process stop is done as a signal action for SIG_DFL.
851 * Returns true if the signal should be actually delivered, otherwise
852 * it should be dropped.
854 static int prepare_signal(int sig, struct task_struct *p, int from_ancestor_ns)
856 struct signal_struct *signal = p->signal;
857 struct task_struct *t;
859 if (unlikely(signal->flags & SIGNAL_GROUP_EXIT)) {
861 * The process is in the middle of dying, nothing to do.
863 } else if (sig_kernel_stop(sig)) {
865 * This is a stop signal. Remove SIGCONT from all queues.
867 rm_from_queue(sigmask(SIGCONT), &signal->shared_pending);
870 rm_from_queue(sigmask(SIGCONT), &t->pending);
871 } while_each_thread(p, t);
872 } else if (sig == SIGCONT) {
875 * Remove all stop signals from all queues, wake all threads.
877 rm_from_queue(SIG_KERNEL_STOP_MASK, &signal->shared_pending);
880 task_clear_jobctl_pending(t, JOBCTL_STOP_PENDING);
881 rm_from_queue(SIG_KERNEL_STOP_MASK, &t->pending);
882 if (likely(!(t->ptrace & PT_SEIZED)))
883 wake_up_state(t, __TASK_STOPPED);
885 ptrace_trap_notify(t);
886 } while_each_thread(p, t);
889 * Notify the parent with CLD_CONTINUED if we were stopped.
891 * If we were in the middle of a group stop, we pretend it
892 * was already finished, and then continued. Since SIGCHLD
893 * doesn't queue we report only CLD_STOPPED, as if the next
894 * CLD_CONTINUED was dropped.
897 if (signal->flags & SIGNAL_STOP_STOPPED)
898 why |= SIGNAL_CLD_CONTINUED;
899 else if (signal->group_stop_count)
900 why |= SIGNAL_CLD_STOPPED;
904 * The first thread which returns from do_signal_stop()
905 * will take ->siglock, notice SIGNAL_CLD_MASK, and
906 * notify its parent. See get_signal_to_deliver().
908 signal->flags = why | SIGNAL_STOP_CONTINUED;
909 signal->group_stop_count = 0;
910 signal->group_exit_code = 0;
914 return !sig_ignored(p, sig, from_ancestor_ns);
918 * Test if P wants to take SIG. After we've checked all threads with this,
919 * it's equivalent to finding no threads not blocking SIG. Any threads not
920 * blocking SIG were ruled out because they are not running and already
921 * have pending signals. Such threads will dequeue from the shared queue
922 * as soon as they're available, so putting the signal on the shared queue
923 * will be equivalent to sending it to one such thread.
925 static inline int wants_signal(int sig, struct task_struct *p)
927 if (sigismember(&p->blocked, sig))
929 if (p->flags & PF_EXITING)
933 if (task_is_stopped_or_traced(p))
935 return task_curr(p) || !signal_pending(p);
938 static void complete_signal(int sig, struct task_struct *p, int group)
940 struct signal_struct *signal = p->signal;
941 struct task_struct *t;
944 * Now find a thread we can wake up to take the signal off the queue.
946 * If the main thread wants the signal, it gets first crack.
947 * Probably the least surprising to the average bear.
949 if (wants_signal(sig, p))
951 else if (!group || thread_group_empty(p))
953 * There is just one thread and it does not need to be woken.
954 * It will dequeue unblocked signals before it runs again.
959 * Otherwise try to find a suitable thread.
961 t = signal->curr_target;
962 while (!wants_signal(sig, t)) {
964 if (t == signal->curr_target)
966 * No thread needs to be woken.
967 * Any eligible threads will see
968 * the signal in the queue soon.
972 signal->curr_target = t;
976 * Found a killable thread. If the signal will be fatal,
977 * then start taking the whole group down immediately.
979 if (sig_fatal(p, sig) &&
980 !(signal->flags & (SIGNAL_UNKILLABLE | SIGNAL_GROUP_EXIT)) &&
981 !sigismember(&t->real_blocked, sig) &&
982 (sig == SIGKILL || !t->ptrace)) {
984 * This signal will be fatal to the whole group.
986 if (!sig_kernel_coredump(sig)) {
988 * Start a group exit and wake everybody up.
989 * This way we don't have other threads
990 * running and doing things after a slower
991 * thread has the fatal signal pending.
993 signal->flags = SIGNAL_GROUP_EXIT;
994 signal->group_exit_code = sig;
995 signal->group_stop_count = 0;
998 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
999 sigaddset(&t->pending.signal, SIGKILL);
1000 signal_wake_up(t, 1);
1001 } while_each_thread(p, t);
1007 * The signal is already in the shared-pending queue.
1008 * Tell the chosen thread to wake up and dequeue it.
1010 signal_wake_up(t, sig == SIGKILL);
1014 static inline int legacy_queue(struct sigpending *signals, int sig)
1016 return (sig < SIGRTMIN) && sigismember(&signals->signal, sig);
1019 static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
1020 int group, int from_ancestor_ns)
1022 struct sigpending *pending;
1024 int override_rlimit;
1026 trace_signal_generate(sig, info, t);
1028 assert_spin_locked(&t->sighand->siglock);
1030 if (!prepare_signal(sig, t, from_ancestor_ns))
1033 pending = group ? &t->signal->shared_pending : &t->pending;
1035 * Short-circuit ignored signals and support queuing
1036 * exactly one non-rt signal, so that we can get more
1037 * detailed information about the cause of the signal.
1039 if (legacy_queue(pending, sig))
1042 * fast-pathed signals for kernel-internal things like SIGSTOP
1045 if (info == SEND_SIG_FORCED)
1049 * Real-time signals must be queued if sent by sigqueue, or
1050 * some other real-time mechanism. It is implementation
1051 * defined whether kill() does so. We attempt to do so, on
1052 * the principle of least surprise, but since kill is not
1053 * allowed to fail with EAGAIN when low on memory we just
1054 * make sure at least one signal gets delivered and don't
1055 * pass on the info struct.
1058 override_rlimit = (is_si_special(info) || info->si_code >= 0);
1060 override_rlimit = 0;
1062 q = __sigqueue_alloc(sig, t, GFP_ATOMIC | __GFP_NOTRACK_FALSE_POSITIVE,
1065 list_add_tail(&q->list, &pending->list);
1066 switch ((unsigned long) info) {
1067 case (unsigned long) SEND_SIG_NOINFO:
1068 q->info.si_signo = sig;
1069 q->info.si_errno = 0;
1070 q->info.si_code = SI_USER;
1071 q->info.si_pid = task_tgid_nr_ns(current,
1072 task_active_pid_ns(t));
1073 q->info.si_uid = current_uid();
1075 case (unsigned long) SEND_SIG_PRIV:
1076 q->info.si_signo = sig;
1077 q->info.si_errno = 0;
1078 q->info.si_code = SI_KERNEL;
1083 copy_siginfo(&q->info, info);
1084 if (from_ancestor_ns)
1088 } else if (!is_si_special(info)) {
1089 if (sig >= SIGRTMIN && info->si_code != SI_USER) {
1091 * Queue overflow, abort. We may abort if the
1092 * signal was rt and sent by user using something
1093 * other than kill().
1095 trace_signal_overflow_fail(sig, group, info);
1099 * This is a silent loss of information. We still
1100 * send the signal, but the *info bits are lost.
1102 trace_signal_lose_info(sig, group, info);
1107 signalfd_notify(t, sig);
1108 sigaddset(&pending->signal, sig);
1109 complete_signal(sig, t, group);
1113 static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
1116 int from_ancestor_ns = 0;
1118 #ifdef CONFIG_PID_NS
1119 from_ancestor_ns = si_fromuser(info) &&
1120 !task_pid_nr_ns(current, task_active_pid_ns(t));
1123 return __send_signal(sig, info, t, group, from_ancestor_ns);
1126 static void print_fatal_signal(struct pt_regs *regs, int signr)
1128 printk("%s/%d: potentially unexpected fatal signal %d.\n",
1129 current->comm, task_pid_nr(current), signr);
1131 #if defined(__i386__) && !defined(__arch_um__)
1132 printk("code at %08lx: ", regs->ip);
1135 for (i = 0; i < 16; i++) {
1138 if (get_user(insn, (unsigned char *)(regs->ip + i)))
1140 printk("%02x ", insn);
1150 static int __init setup_print_fatal_signals(char *str)
1152 get_option (&str, &print_fatal_signals);
1157 __setup("print-fatal-signals=", setup_print_fatal_signals);
1160 __group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
1162 return send_signal(sig, info, p, 1);
1166 specific_send_sig_info(int sig, struct siginfo *info, struct task_struct *t)
1168 return send_signal(sig, info, t, 0);
1171 int do_send_sig_info(int sig, struct siginfo *info, struct task_struct *p,
1174 unsigned long flags;
1177 if (lock_task_sighand(p, &flags)) {
1178 ret = send_signal(sig, info, p, group);
1179 unlock_task_sighand(p, &flags);
1186 * Force a signal that the process can't ignore: if necessary
1187 * we unblock the signal and change any SIG_IGN to SIG_DFL.
1189 * Note: If we unblock the signal, we always reset it to SIG_DFL,
1190 * since we do not want to have a signal handler that was blocked
1191 * be invoked when user space had explicitly blocked it.
1193 * We don't want to have recursive SIGSEGV's etc, for example,
1194 * that is why we also clear SIGNAL_UNKILLABLE.
1197 force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
1199 unsigned long int flags;
1200 int ret, blocked, ignored;
1201 struct k_sigaction *action;
1203 spin_lock_irqsave(&t->sighand->siglock, flags);
1204 action = &t->sighand->action[sig-1];
1205 ignored = action->sa.sa_handler == SIG_IGN;
1206 blocked = sigismember(&t->blocked, sig);
1207 if (blocked || ignored) {
1208 action->sa.sa_handler = SIG_DFL;
1210 sigdelset(&t->blocked, sig);
1211 recalc_sigpending_and_wake(t);
1214 if (action->sa.sa_handler == SIG_DFL)
1215 t->signal->flags &= ~SIGNAL_UNKILLABLE;
1216 ret = specific_send_sig_info(sig, info, t);
1217 spin_unlock_irqrestore(&t->sighand->siglock, flags);
1223 * Nuke all other threads in the group.
1225 int zap_other_threads(struct task_struct *p)
1227 struct task_struct *t = p;
1230 p->signal->group_stop_count = 0;
1232 while_each_thread(p, t) {
1233 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
1236 /* Don't bother with already dead threads */
1239 sigaddset(&t->pending.signal, SIGKILL);
1240 signal_wake_up(t, 1);
1246 struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
1247 unsigned long *flags)
1249 struct sighand_struct *sighand;
1252 local_irq_save(*flags);
1254 sighand = rcu_dereference(tsk->sighand);
1255 if (unlikely(sighand == NULL)) {
1257 local_irq_restore(*flags);
1261 spin_lock(&sighand->siglock);
1262 if (likely(sighand == tsk->sighand)) {
1266 spin_unlock(&sighand->siglock);
1268 local_irq_restore(*flags);
1273 EXPORT_SYMBOL_GPL(__lock_task_sighand);
1276 * send signal info to all the members of a group
1278 int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
1283 ret = check_kill_permission(sig, info, p);
1287 ret = do_send_sig_info(sig, info, p, true);
1293 * __kill_pgrp_info() sends a signal to a process group: this is what the tty
1294 * control characters do (^C, ^Z etc)
1295 * - the caller must hold at least a readlock on tasklist_lock
1297 int __kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp)
1299 struct task_struct *p = NULL;
1300 int retval, success;
1304 do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
1305 int err = group_send_sig_info(sig, info, p);
1308 } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
1309 return success ? 0 : retval;
1312 int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
1315 struct task_struct *p;
1319 p = pid_task(pid, PIDTYPE_PID);
1321 error = group_send_sig_info(sig, info, p);
1322 if (unlikely(error == -ESRCH))
1324 * The task was unhashed in between, try again.
1325 * If it is dead, pid_task() will return NULL,
1326 * if we race with de_thread() it will find the
1336 int kill_proc_info(int sig, struct siginfo *info, pid_t pid)
1340 error = kill_pid_info(sig, info, find_vpid(pid));
1345 static int kill_as_cred_perm(const struct cred *cred,
1346 struct task_struct *target)
1348 const struct cred *pcred = __task_cred(target);
1349 if (cred->user_ns != pcred->user_ns)
1351 if (cred->euid != pcred->suid && cred->euid != pcred->uid &&
1352 cred->uid != pcred->suid && cred->uid != pcred->uid)
1357 /* like kill_pid_info(), but doesn't use uid/euid of "current" */
1358 int kill_pid_info_as_cred(int sig, struct siginfo *info, struct pid *pid,
1359 const struct cred *cred, u32 secid)
1362 struct task_struct *p;
1363 unsigned long flags;
1365 if (!valid_signal(sig))
1369 p = pid_task(pid, PIDTYPE_PID);
1374 if (si_fromuser(info) && !kill_as_cred_perm(cred, p)) {
1378 ret = security_task_kill(p, info, sig, secid);
1383 if (lock_task_sighand(p, &flags)) {
1384 ret = __send_signal(sig, info, p, 1, 0);
1385 unlock_task_sighand(p, &flags);
1393 EXPORT_SYMBOL_GPL(kill_pid_info_as_cred);
1396 * kill_something_info() interprets pid in interesting ways just like kill(2).
1398 * POSIX specifies that kill(-1,sig) is unspecified, but what we have
1399 * is probably wrong. Should make it like BSD or SYSV.
1402 static int kill_something_info(int sig, struct siginfo *info, pid_t pid)
1408 ret = kill_pid_info(sig, info, find_vpid(pid));
1413 read_lock(&tasklist_lock);
1415 ret = __kill_pgrp_info(sig, info,
1416 pid ? find_vpid(-pid) : task_pgrp(current));
1418 int retval = 0, count = 0;
1419 struct task_struct * p;
1421 for_each_process(p) {
1422 if (task_pid_vnr(p) > 1 &&
1423 !same_thread_group(p, current)) {
1424 int err = group_send_sig_info(sig, info, p);
1430 ret = count ? retval : -ESRCH;
1432 read_unlock(&tasklist_lock);
1438 * These are for backward compatibility with the rest of the kernel source.
1441 int send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
1444 * Make sure legacy kernel users don't send in bad values
1445 * (normal paths check this in check_kill_permission).
1447 if (!valid_signal(sig))
1450 return do_send_sig_info(sig, info, p, false);
1453 #define __si_special(priv) \
1454 ((priv) ? SEND_SIG_PRIV : SEND_SIG_NOINFO)
1457 send_sig(int sig, struct task_struct *p, int priv)
1459 return send_sig_info(sig, __si_special(priv), p);
1463 force_sig(int sig, struct task_struct *p)
1465 force_sig_info(sig, SEND_SIG_PRIV, p);
1469 * When things go south during signal handling, we
1470 * will force a SIGSEGV. And if the signal that caused
1471 * the problem was already a SIGSEGV, we'll want to
1472 * make sure we don't even try to deliver the signal..
1475 force_sigsegv(int sig, struct task_struct *p)
1477 if (sig == SIGSEGV) {
1478 unsigned long flags;
1479 spin_lock_irqsave(&p->sighand->siglock, flags);
1480 p->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;
1481 spin_unlock_irqrestore(&p->sighand->siglock, flags);
1483 force_sig(SIGSEGV, p);
1487 int kill_pgrp(struct pid *pid, int sig, int priv)
1491 read_lock(&tasklist_lock);
1492 ret = __kill_pgrp_info(sig, __si_special(priv), pid);
1493 read_unlock(&tasklist_lock);
1497 EXPORT_SYMBOL(kill_pgrp);
1499 int kill_pid(struct pid *pid, int sig, int priv)
1501 return kill_pid_info(sig, __si_special(priv), pid);
1503 EXPORT_SYMBOL(kill_pid);
1506 * These functions support sending signals using preallocated sigqueue
1507 * structures. This is needed "because realtime applications cannot
1508 * afford to lose notifications of asynchronous events, like timer
1509 * expirations or I/O completions". In the case of POSIX Timers
1510 * we allocate the sigqueue structure from the timer_create. If this
1511 * allocation fails we are able to report the failure to the application
1512 * with an EAGAIN error.
1514 struct sigqueue *sigqueue_alloc(void)
1516 struct sigqueue *q = __sigqueue_alloc(-1, current, GFP_KERNEL, 0);
1519 q->flags |= SIGQUEUE_PREALLOC;
1524 void sigqueue_free(struct sigqueue *q)
1526 unsigned long flags;
1527 spinlock_t *lock = ¤t->sighand->siglock;
1529 BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
1531 * We must hold ->siglock while testing q->list
1532 * to serialize with collect_signal() or with
1533 * __exit_signal()->flush_sigqueue().
1535 spin_lock_irqsave(lock, flags);
1536 q->flags &= ~SIGQUEUE_PREALLOC;
1538 * If it is queued it will be freed when dequeued,
1539 * like the "regular" sigqueue.
1541 if (!list_empty(&q->list))
1543 spin_unlock_irqrestore(lock, flags);
1549 int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group)
1551 int sig = q->info.si_signo;
1552 struct sigpending *pending;
1553 unsigned long flags;
1556 BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
1559 if (!likely(lock_task_sighand(t, &flags)))
1562 ret = 1; /* the signal is ignored */
1563 if (!prepare_signal(sig, t, 0))
1567 if (unlikely(!list_empty(&q->list))) {
1569 * If an SI_TIMER entry is already queue just increment
1570 * the overrun count.
1572 BUG_ON(q->info.si_code != SI_TIMER);
1573 q->info.si_overrun++;
1576 q->info.si_overrun = 0;
1578 signalfd_notify(t, sig);
1579 pending = group ? &t->signal->shared_pending : &t->pending;
1580 list_add_tail(&q->list, &pending->list);
1581 sigaddset(&pending->signal, sig);
1582 complete_signal(sig, t, group);
1584 unlock_task_sighand(t, &flags);
1590 * Let a parent know about the death of a child.
1591 * For a stopped/continued status change, use do_notify_parent_cldstop instead.
1593 * Returns true if our parent ignored us and so we've switched to
1596 bool do_notify_parent(struct task_struct *tsk, int sig)
1598 struct siginfo info;
1599 unsigned long flags;
1600 struct sighand_struct *psig;
1601 bool autoreap = false;
1605 /* do_notify_parent_cldstop should have been called instead. */
1606 BUG_ON(task_is_stopped_or_traced(tsk));
1608 BUG_ON(!tsk->ptrace &&
1609 (tsk->group_leader != tsk || !thread_group_empty(tsk)));
1611 if (sig != SIGCHLD) {
1613 * This is only possible if parent == real_parent.
1614 * Check if it has changed security domain.
1616 if (tsk->parent_exec_id != tsk->parent->self_exec_id)
1620 info.si_signo = sig;
1623 * we are under tasklist_lock here so our parent is tied to
1624 * us and cannot exit and release its namespace.
1626 * the only it can is to switch its nsproxy with sys_unshare,
1627 * bu uncharing pid namespaces is not allowed, so we'll always
1628 * see relevant namespace
1630 * write_lock() currently calls preempt_disable() which is the
1631 * same as rcu_read_lock(), but according to Oleg, this is not
1632 * correct to rely on this
1635 info.si_pid = task_pid_nr_ns(tsk, tsk->parent->nsproxy->pid_ns);
1636 info.si_uid = __task_cred(tsk)->uid;
1639 info.si_utime = cputime_to_clock_t(cputime_add(tsk->utime,
1640 tsk->signal->utime));
1641 info.si_stime = cputime_to_clock_t(cputime_add(tsk->stime,
1642 tsk->signal->stime));
1644 info.si_status = tsk->exit_code & 0x7f;
1645 if (tsk->exit_code & 0x80)
1646 info.si_code = CLD_DUMPED;
1647 else if (tsk->exit_code & 0x7f)
1648 info.si_code = CLD_KILLED;
1650 info.si_code = CLD_EXITED;
1651 info.si_status = tsk->exit_code >> 8;
1654 psig = tsk->parent->sighand;
1655 spin_lock_irqsave(&psig->siglock, flags);
1656 if (!tsk->ptrace && sig == SIGCHLD &&
1657 (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
1658 (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) {
1660 * We are exiting and our parent doesn't care. POSIX.1
1661 * defines special semantics for setting SIGCHLD to SIG_IGN
1662 * or setting the SA_NOCLDWAIT flag: we should be reaped
1663 * automatically and not left for our parent's wait4 call.
1664 * Rather than having the parent do it as a magic kind of
1665 * signal handler, we just set this to tell do_exit that we
1666 * can be cleaned up without becoming a zombie. Note that
1667 * we still call __wake_up_parent in this case, because a
1668 * blocked sys_wait4 might now return -ECHILD.
1670 * Whether we send SIGCHLD or not for SA_NOCLDWAIT
1671 * is implementation-defined: we do (if you don't want
1672 * it, just use SIG_IGN instead).
1675 if (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN)
1678 if (valid_signal(sig) && sig)
1679 __group_send_sig_info(sig, &info, tsk->parent);
1680 __wake_up_parent(tsk, tsk->parent);
1681 spin_unlock_irqrestore(&psig->siglock, flags);
1687 * do_notify_parent_cldstop - notify parent of stopped/continued state change
1688 * @tsk: task reporting the state change
1689 * @for_ptracer: the notification is for ptracer
1690 * @why: CLD_{CONTINUED|STOPPED|TRAPPED} to report
1692 * Notify @tsk's parent that the stopped/continued state has changed. If
1693 * @for_ptracer is %false, @tsk's group leader notifies to its real parent.
1694 * If %true, @tsk reports to @tsk->parent which should be the ptracer.
1697 * Must be called with tasklist_lock at least read locked.
1699 static void do_notify_parent_cldstop(struct task_struct *tsk,
1700 bool for_ptracer, int why)
1702 struct siginfo info;
1703 unsigned long flags;
1704 struct task_struct *parent;
1705 struct sighand_struct *sighand;
1708 parent = tsk->parent;
1710 tsk = tsk->group_leader;
1711 parent = tsk->real_parent;
1714 info.si_signo = SIGCHLD;
1717 * see comment in do_notify_parent() about the following 4 lines
1720 info.si_pid = task_pid_nr_ns(tsk, parent->nsproxy->pid_ns);
1721 info.si_uid = __task_cred(tsk)->uid;
1724 info.si_utime = cputime_to_clock_t(tsk->utime);
1725 info.si_stime = cputime_to_clock_t(tsk->stime);
1730 info.si_status = SIGCONT;
1733 info.si_status = tsk->signal->group_exit_code & 0x7f;
1736 info.si_status = tsk->exit_code & 0x7f;
1742 sighand = parent->sighand;
1743 spin_lock_irqsave(&sighand->siglock, flags);
1744 if (sighand->action[SIGCHLD-1].sa.sa_handler != SIG_IGN &&
1745 !(sighand->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDSTOP))
1746 __group_send_sig_info(SIGCHLD, &info, parent);
1748 * Even if SIGCHLD is not generated, we must wake up wait4 calls.
1750 __wake_up_parent(tsk, parent);
1751 spin_unlock_irqrestore(&sighand->siglock, flags);
1754 static inline int may_ptrace_stop(void)
1756 if (!likely(current->ptrace))
1759 * Are we in the middle of do_coredump?
1760 * If so and our tracer is also part of the coredump stopping
1761 * is a deadlock situation, and pointless because our tracer
1762 * is dead so don't allow us to stop.
1763 * If SIGKILL was already sent before the caller unlocked
1764 * ->siglock we must see ->core_state != NULL. Otherwise it
1765 * is safe to enter schedule().
1767 * This is almost outdated, a task with the pending SIGKILL can't
1768 * block in TASK_TRACED. But PTRACE_EVENT_EXIT can be reported
1769 * after SIGKILL was already dequeued.
1771 if (unlikely(current->mm->core_state) &&
1772 unlikely(current->mm == current->parent->mm))
1779 * Return non-zero if there is a SIGKILL that should be waking us up.
1780 * Called with the siglock held.
1782 static int sigkill_pending(struct task_struct *tsk)
1784 return sigismember(&tsk->pending.signal, SIGKILL) ||
1785 sigismember(&tsk->signal->shared_pending.signal, SIGKILL);
1789 * This must be called with current->sighand->siglock held.
1791 * This should be the path for all ptrace stops.
1792 * We always set current->last_siginfo while stopped here.
1793 * That makes it a way to test a stopped process for
1794 * being ptrace-stopped vs being job-control-stopped.
1796 * If we actually decide not to stop at all because the tracer
1797 * is gone, we keep current->exit_code unless clear_code.
1799 static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
1800 __releases(¤t->sighand->siglock)
1801 __acquires(¤t->sighand->siglock)
1803 bool gstop_done = false;
1805 if (arch_ptrace_stop_needed(exit_code, info)) {
1807 * The arch code has something special to do before a
1808 * ptrace stop. This is allowed to block, e.g. for faults
1809 * on user stack pages. We can't keep the siglock while
1810 * calling arch_ptrace_stop, so we must release it now.
1811 * To preserve proper semantics, we must do this before
1812 * any signal bookkeeping like checking group_stop_count.
1813 * Meanwhile, a SIGKILL could come in before we retake the
1814 * siglock. That must prevent us from sleeping in TASK_TRACED.
1815 * So after regaining the lock, we must check for SIGKILL.
1817 spin_unlock_irq(¤t->sighand->siglock);
1818 arch_ptrace_stop(exit_code, info);
1819 spin_lock_irq(¤t->sighand->siglock);
1820 if (sigkill_pending(current))
1825 * We're committing to trapping. TRACED should be visible before
1826 * TRAPPING is cleared; otherwise, the tracer might fail do_wait().
1827 * Also, transition to TRACED and updates to ->jobctl should be
1828 * atomic with respect to siglock and should be done after the arch
1829 * hook as siglock is released and regrabbed across it.
1831 set_current_state(TASK_TRACED);
1833 current->last_siginfo = info;
1834 current->exit_code = exit_code;
1837 * If @why is CLD_STOPPED, we're trapping to participate in a group
1838 * stop. Do the bookkeeping. Note that if SIGCONT was delievered
1839 * across siglock relocks since INTERRUPT was scheduled, PENDING
1840 * could be clear now. We act as if SIGCONT is received after
1841 * TASK_TRACED is entered - ignore it.
1843 if (why == CLD_STOPPED && (current->jobctl & JOBCTL_STOP_PENDING))
1844 gstop_done = task_participate_group_stop(current);
1846 /* any trap clears pending STOP trap, STOP trap clears NOTIFY */
1847 task_clear_jobctl_pending(current, JOBCTL_TRAP_STOP);
1848 if (info && info->si_code >> 8 == PTRACE_EVENT_STOP)
1849 task_clear_jobctl_pending(current, JOBCTL_TRAP_NOTIFY);
1851 /* entering a trap, clear TRAPPING */
1852 task_clear_jobctl_trapping(current);
1854 spin_unlock_irq(¤t->sighand->siglock);
1855 read_lock(&tasklist_lock);
1856 if (may_ptrace_stop()) {
1858 * Notify parents of the stop.
1860 * While ptraced, there are two parents - the ptracer and
1861 * the real_parent of the group_leader. The ptracer should
1862 * know about every stop while the real parent is only
1863 * interested in the completion of group stop. The states
1864 * for the two don't interact with each other. Notify
1865 * separately unless they're gonna be duplicates.
1867 do_notify_parent_cldstop(current, true, why);
1868 if (gstop_done && ptrace_reparented(current))
1869 do_notify_parent_cldstop(current, false, why);
1872 * Don't want to allow preemption here, because
1873 * sys_ptrace() needs this task to be inactive.
1875 * XXX: implement read_unlock_no_resched().
1878 read_unlock(&tasklist_lock);
1879 preempt_enable_no_resched();
1883 * By the time we got the lock, our tracer went away.
1884 * Don't drop the lock yet, another tracer may come.
1886 * If @gstop_done, the ptracer went away between group stop
1887 * completion and here. During detach, it would have set
1888 * JOBCTL_STOP_PENDING on us and we'll re-enter
1889 * TASK_STOPPED in do_signal_stop() on return, so notifying
1890 * the real parent of the group stop completion is enough.
1893 do_notify_parent_cldstop(current, false, why);
1895 /* tasklist protects us from ptrace_freeze_traced() */
1896 __set_current_state(TASK_RUNNING);
1898 current->exit_code = 0;
1899 read_unlock(&tasklist_lock);
1903 * While in TASK_TRACED, we were considered "frozen enough".
1904 * Now that we woke up, it's crucial if we're supposed to be
1905 * frozen that we freeze now before running anything substantial.
1910 * We are back. Now reacquire the siglock before touching
1911 * last_siginfo, so that we are sure to have synchronized with
1912 * any signal-sending on another CPU that wants to examine it.
1914 spin_lock_irq(¤t->sighand->siglock);
1915 current->last_siginfo = NULL;
1917 /* LISTENING can be set only during STOP traps, clear it */
1918 current->jobctl &= ~JOBCTL_LISTENING;
1921 * Queued signals ignored us while we were stopped for tracing.
1922 * So check for any that we should take before resuming user mode.
1923 * This sets TIF_SIGPENDING, but never clears it.
1925 recalc_sigpending_tsk(current);
1928 static void ptrace_do_notify(int signr, int exit_code, int why)
1932 memset(&info, 0, sizeof info);
1933 info.si_signo = signr;
1934 info.si_code = exit_code;
1935 info.si_pid = task_pid_vnr(current);
1936 info.si_uid = current_uid();
1938 /* Let the debugger run. */
1939 ptrace_stop(exit_code, why, 1, &info);
1942 void ptrace_notify(int exit_code)
1944 BUG_ON((exit_code & (0x7f | ~0xffff)) != SIGTRAP);
1946 spin_lock_irq(¤t->sighand->siglock);
1947 ptrace_do_notify(SIGTRAP, exit_code, CLD_TRAPPED);
1948 spin_unlock_irq(¤t->sighand->siglock);
1952 * do_signal_stop - handle group stop for SIGSTOP and other stop signals
1953 * @signr: signr causing group stop if initiating
1955 * If %JOBCTL_STOP_PENDING is not set yet, initiate group stop with @signr
1956 * and participate in it. If already set, participate in the existing
1957 * group stop. If participated in a group stop (and thus slept), %true is
1958 * returned with siglock released.
1960 * If ptraced, this function doesn't handle stop itself. Instead,
1961 * %JOBCTL_TRAP_STOP is scheduled and %false is returned with siglock
1962 * untouched. The caller must ensure that INTERRUPT trap handling takes
1963 * places afterwards.
1966 * Must be called with @current->sighand->siglock held, which is released
1970 * %false if group stop is already cancelled or ptrace trap is scheduled.
1971 * %true if participated in group stop.
1973 static bool do_signal_stop(int signr)
1974 __releases(¤t->sighand->siglock)
1976 struct signal_struct *sig = current->signal;
1978 if (!(current->jobctl & JOBCTL_STOP_PENDING)) {
1979 unsigned int gstop = JOBCTL_STOP_PENDING | JOBCTL_STOP_CONSUME;
1980 struct task_struct *t;
1982 /* signr will be recorded in task->jobctl for retries */
1983 WARN_ON_ONCE(signr & ~JOBCTL_STOP_SIGMASK);
1985 if (!likely(current->jobctl & JOBCTL_STOP_DEQUEUED) ||
1986 unlikely(signal_group_exit(sig)))
1989 * There is no group stop already in progress. We must
1992 * While ptraced, a task may be resumed while group stop is
1993 * still in effect and then receive a stop signal and
1994 * initiate another group stop. This deviates from the
1995 * usual behavior as two consecutive stop signals can't
1996 * cause two group stops when !ptraced. That is why we
1997 * also check !task_is_stopped(t) below.
1999 * The condition can be distinguished by testing whether
2000 * SIGNAL_STOP_STOPPED is already set. Don't generate
2001 * group_exit_code in such case.
2003 * This is not necessary for SIGNAL_STOP_CONTINUED because
2004 * an intervening stop signal is required to cause two
2005 * continued events regardless of ptrace.
2007 if (!(sig->flags & SIGNAL_STOP_STOPPED))
2008 sig->group_exit_code = signr;
2010 sig->group_stop_count = 0;
2012 if (task_set_jobctl_pending(current, signr | gstop))
2013 sig->group_stop_count++;
2015 for (t = next_thread(current); t != current;
2016 t = next_thread(t)) {
2018 * Setting state to TASK_STOPPED for a group
2019 * stop is always done with the siglock held,
2020 * so this check has no races.
2022 if (!task_is_stopped(t) &&
2023 task_set_jobctl_pending(t, signr | gstop)) {
2024 sig->group_stop_count++;
2025 if (likely(!(t->ptrace & PT_SEIZED)))
2026 signal_wake_up(t, 0);
2028 ptrace_trap_notify(t);
2033 if (likely(!current->ptrace)) {
2037 * If there are no other threads in the group, or if there
2038 * is a group stop in progress and we are the last to stop,
2039 * report to the parent.
2041 if (task_participate_group_stop(current))
2042 notify = CLD_STOPPED;
2044 __set_current_state(TASK_STOPPED);
2045 spin_unlock_irq(¤t->sighand->siglock);
2048 * Notify the parent of the group stop completion. Because
2049 * we're not holding either the siglock or tasklist_lock
2050 * here, ptracer may attach inbetween; however, this is for
2051 * group stop and should always be delivered to the real
2052 * parent of the group leader. The new ptracer will get
2053 * its notification when this task transitions into
2057 read_lock(&tasklist_lock);
2058 do_notify_parent_cldstop(current, false, notify);
2059 read_unlock(&tasklist_lock);
2062 /* Now we don't run again until woken by SIGCONT or SIGKILL */
2067 * While ptraced, group stop is handled by STOP trap.
2068 * Schedule it and let the caller deal with it.
2070 task_set_jobctl_pending(current, JOBCTL_TRAP_STOP);
2076 * do_jobctl_trap - take care of ptrace jobctl traps
2078 * When PT_SEIZED, it's used for both group stop and explicit
2079 * SEIZE/INTERRUPT traps. Both generate PTRACE_EVENT_STOP trap with
2080 * accompanying siginfo. If stopped, lower eight bits of exit_code contain
2081 * the stop signal; otherwise, %SIGTRAP.
2083 * When !PT_SEIZED, it's used only for group stop trap with stop signal
2084 * number as exit_code and no siginfo.
2087 * Must be called with @current->sighand->siglock held, which may be
2088 * released and re-acquired before returning with intervening sleep.
2090 static void do_jobctl_trap(void)
2092 struct signal_struct *signal = current->signal;
2093 int signr = current->jobctl & JOBCTL_STOP_SIGMASK;
2095 if (current->ptrace & PT_SEIZED) {
2096 if (!signal->group_stop_count &&
2097 !(signal->flags & SIGNAL_STOP_STOPPED))
2099 WARN_ON_ONCE(!signr);
2100 ptrace_do_notify(signr, signr | (PTRACE_EVENT_STOP << 8),
2103 WARN_ON_ONCE(!signr);
2104 ptrace_stop(signr, CLD_STOPPED, 0, NULL);
2105 current->exit_code = 0;
2109 static int ptrace_signal(int signr, siginfo_t *info,
2110 struct pt_regs *regs, void *cookie)
2112 ptrace_signal_deliver(regs, cookie);
2114 * We do not check sig_kernel_stop(signr) but set this marker
2115 * unconditionally because we do not know whether debugger will
2116 * change signr. This flag has no meaning unless we are going
2117 * to stop after return from ptrace_stop(). In this case it will
2118 * be checked in do_signal_stop(), we should only stop if it was
2119 * not cleared by SIGCONT while we were sleeping. See also the
2120 * comment in dequeue_signal().
2122 current->jobctl |= JOBCTL_STOP_DEQUEUED;
2123 ptrace_stop(signr, CLD_TRAPPED, 0, info);
2125 /* We're back. Did the debugger cancel the sig? */
2126 signr = current->exit_code;
2130 current->exit_code = 0;
2133 * Update the siginfo structure if the signal has
2134 * changed. If the debugger wanted something
2135 * specific in the siginfo structure then it should
2136 * have updated *info via PTRACE_SETSIGINFO.
2138 if (signr != info->si_signo) {
2139 info->si_signo = signr;
2141 info->si_code = SI_USER;
2142 info->si_pid = task_pid_vnr(current->parent);
2143 info->si_uid = task_uid(current->parent);
2146 /* If the (new) signal is now blocked, requeue it. */
2147 if (sigismember(¤t->blocked, signr)) {
2148 specific_send_sig_info(signr, info, current);
2155 int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka,
2156 struct pt_regs *regs, void *cookie)
2158 struct sighand_struct *sighand = current->sighand;
2159 struct signal_struct *signal = current->signal;
2164 * We'll jump back here after any time we were stopped in TASK_STOPPED.
2165 * While in TASK_STOPPED, we were considered "frozen enough".
2166 * Now that we woke up, it's crucial if we're supposed to be
2167 * frozen that we freeze now before running anything substantial.
2171 spin_lock_irq(&sighand->siglock);
2173 * Every stopped thread goes here after wakeup. Check to see if
2174 * we should notify the parent, prepare_signal(SIGCONT) encodes
2175 * the CLD_ si_code into SIGNAL_CLD_MASK bits.
2177 if (unlikely(signal->flags & SIGNAL_CLD_MASK)) {
2180 if (signal->flags & SIGNAL_CLD_CONTINUED)
2181 why = CLD_CONTINUED;
2185 signal->flags &= ~SIGNAL_CLD_MASK;
2187 spin_unlock_irq(&sighand->siglock);
2190 * Notify the parent that we're continuing. This event is
2191 * always per-process and doesn't make whole lot of sense
2192 * for ptracers, who shouldn't consume the state via
2193 * wait(2) either, but, for backward compatibility, notify
2194 * the ptracer of the group leader too unless it's gonna be
2197 read_lock(&tasklist_lock);
2198 do_notify_parent_cldstop(current, false, why);
2200 if (ptrace_reparented(current->group_leader))
2201 do_notify_parent_cldstop(current->group_leader,
2203 read_unlock(&tasklist_lock);
2209 struct k_sigaction *ka;
2211 if (unlikely(current->jobctl & JOBCTL_STOP_PENDING) &&
2215 if (unlikely(current->jobctl & JOBCTL_TRAP_MASK)) {
2217 spin_unlock_irq(&sighand->siglock);
2221 signr = dequeue_signal(current, ¤t->blocked, info);
2224 break; /* will return 0 */
2226 if (unlikely(current->ptrace) && signr != SIGKILL) {
2227 signr = ptrace_signal(signr, info,
2233 ka = &sighand->action[signr-1];
2235 /* Trace actually delivered signals. */
2236 trace_signal_deliver(signr, info, ka);
2238 if (ka->sa.sa_handler == SIG_IGN) /* Do nothing. */
2240 if (ka->sa.sa_handler != SIG_DFL) {
2241 /* Run the handler. */
2244 if (ka->sa.sa_flags & SA_ONESHOT)
2245 ka->sa.sa_handler = SIG_DFL;
2247 break; /* will return non-zero "signr" value */
2251 * Now we are doing the default action for this signal.
2253 if (sig_kernel_ignore(signr)) /* Default is nothing. */
2257 * Global init gets no signals it doesn't want.
2258 * Container-init gets no signals it doesn't want from same
2261 * Note that if global/container-init sees a sig_kernel_only()
2262 * signal here, the signal must have been generated internally
2263 * or must have come from an ancestor namespace. In either
2264 * case, the signal cannot be dropped.
2266 if (unlikely(signal->flags & SIGNAL_UNKILLABLE) &&
2267 !sig_kernel_only(signr))
2270 if (sig_kernel_stop(signr)) {
2272 * The default action is to stop all threads in
2273 * the thread group. The job control signals
2274 * do nothing in an orphaned pgrp, but SIGSTOP
2275 * always works. Note that siglock needs to be
2276 * dropped during the call to is_orphaned_pgrp()
2277 * because of lock ordering with tasklist_lock.
2278 * This allows an intervening SIGCONT to be posted.
2279 * We need to check for that and bail out if necessary.
2281 if (signr != SIGSTOP) {
2282 spin_unlock_irq(&sighand->siglock);
2284 /* signals can be posted during this window */
2286 if (is_current_pgrp_orphaned())
2289 spin_lock_irq(&sighand->siglock);
2292 if (likely(do_signal_stop(info->si_signo))) {
2293 /* It released the siglock. */
2298 * We didn't actually stop, due to a race
2299 * with SIGCONT or something like that.
2304 spin_unlock_irq(&sighand->siglock);
2307 * Anything else is fatal, maybe with a core dump.
2309 current->flags |= PF_SIGNALED;
2311 if (sig_kernel_coredump(signr)) {
2312 if (print_fatal_signals)
2313 print_fatal_signal(regs, info->si_signo);
2315 * If it was able to dump core, this kills all
2316 * other threads in the group and synchronizes with
2317 * their demise. If we lost the race with another
2318 * thread getting here, it set group_exit_code
2319 * first and our do_group_exit call below will use
2320 * that value and ignore the one we pass it.
2322 do_coredump(info->si_signo, info->si_signo, regs);
2326 * Death signals, no core dump.
2328 do_group_exit(info->si_signo);
2331 spin_unlock_irq(&sighand->siglock);
2336 * It could be that complete_signal() picked us to notify about the
2337 * group-wide signal. Other threads should be notified now to take
2338 * the shared signals in @which since we will not.
2340 static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which)
2343 struct task_struct *t;
2345 sigandsets(&retarget, &tsk->signal->shared_pending.signal, which);
2346 if (sigisemptyset(&retarget))
2350 while_each_thread(tsk, t) {
2351 if (t->flags & PF_EXITING)
2354 if (!has_pending_signals(&retarget, &t->blocked))
2356 /* Remove the signals this thread can handle. */
2357 sigandsets(&retarget, &retarget, &t->blocked);
2359 if (!signal_pending(t))
2360 signal_wake_up(t, 0);
2362 if (sigisemptyset(&retarget))
2367 void exit_signals(struct task_struct *tsk)
2372 if (thread_group_empty(tsk) || signal_group_exit(tsk->signal)) {
2373 tsk->flags |= PF_EXITING;
2377 spin_lock_irq(&tsk->sighand->siglock);
2379 * From now this task is not visible for group-wide signals,
2380 * see wants_signal(), do_signal_stop().
2382 tsk->flags |= PF_EXITING;
2383 if (!signal_pending(tsk))
2386 unblocked = tsk->blocked;
2387 signotset(&unblocked);
2388 retarget_shared_pending(tsk, &unblocked);
2390 if (unlikely(tsk->jobctl & JOBCTL_STOP_PENDING) &&
2391 task_participate_group_stop(tsk))
2392 group_stop = CLD_STOPPED;
2394 spin_unlock_irq(&tsk->sighand->siglock);
2397 * If group stop has completed, deliver the notification. This
2398 * should always go to the real parent of the group leader.
2400 if (unlikely(group_stop)) {
2401 read_lock(&tasklist_lock);
2402 do_notify_parent_cldstop(tsk, false, group_stop);
2403 read_unlock(&tasklist_lock);
2407 EXPORT_SYMBOL(recalc_sigpending);
2408 EXPORT_SYMBOL_GPL(dequeue_signal);
2409 EXPORT_SYMBOL(flush_signals);
2410 EXPORT_SYMBOL(force_sig);
2411 EXPORT_SYMBOL(send_sig);
2412 EXPORT_SYMBOL(send_sig_info);
2413 EXPORT_SYMBOL(sigprocmask);
2414 EXPORT_SYMBOL(block_all_signals);
2415 EXPORT_SYMBOL(unblock_all_signals);
2419 * System call entry points.
2423 * sys_restart_syscall - restart a system call
2425 SYSCALL_DEFINE0(restart_syscall)
2427 struct restart_block *restart = ¤t_thread_info()->restart_block;
2428 return restart->fn(restart);
2431 long do_no_restart_syscall(struct restart_block *param)
2436 static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset)
2438 if (signal_pending(tsk) && !thread_group_empty(tsk)) {
2439 sigset_t newblocked;
2440 /* A set of now blocked but previously unblocked signals. */
2441 sigandnsets(&newblocked, newset, ¤t->blocked);
2442 retarget_shared_pending(tsk, &newblocked);
2444 tsk->blocked = *newset;
2445 recalc_sigpending();
2449 * set_current_blocked - change current->blocked mask
2452 * It is wrong to change ->blocked directly, this helper should be used
2453 * to ensure the process can't miss a shared signal we are going to block.
2455 void set_current_blocked(const sigset_t *newset)
2457 struct task_struct *tsk = current;
2459 spin_lock_irq(&tsk->sighand->siglock);
2460 __set_task_blocked(tsk, newset);
2461 spin_unlock_irq(&tsk->sighand->siglock);
2465 * This is also useful for kernel threads that want to temporarily
2466 * (or permanently) block certain signals.
2468 * NOTE! Unlike the user-mode sys_sigprocmask(), the kernel
2469 * interface happily blocks "unblockable" signals like SIGKILL
2472 int sigprocmask(int how, sigset_t *set, sigset_t *oldset)
2474 struct task_struct *tsk = current;
2477 /* Lockless, only current can change ->blocked, never from irq */
2479 *oldset = tsk->blocked;
2483 sigorsets(&newset, &tsk->blocked, set);
2486 sigandnsets(&newset, &tsk->blocked, set);
2495 set_current_blocked(&newset);
2500 * sys_rt_sigprocmask - change the list of currently blocked signals
2501 * @how: whether to add, remove, or set signals
2502 * @nset: stores pending signals
2503 * @oset: previous value of signal mask if non-null
2504 * @sigsetsize: size of sigset_t type
2506 SYSCALL_DEFINE4(rt_sigprocmask, int, how, sigset_t __user *, nset,
2507 sigset_t __user *, oset, size_t, sigsetsize)
2509 sigset_t old_set, new_set;
2512 /* XXX: Don't preclude handling different sized sigset_t's. */
2513 if (sigsetsize != sizeof(sigset_t))
2516 old_set = current->blocked;
2519 if (copy_from_user(&new_set, nset, sizeof(sigset_t)))
2521 sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
2523 error = sigprocmask(how, &new_set, NULL);
2529 if (copy_to_user(oset, &old_set, sizeof(sigset_t)))
2536 long do_sigpending(void __user *set, unsigned long sigsetsize)
2538 long error = -EINVAL;
2541 if (sigsetsize > sizeof(sigset_t))
2544 spin_lock_irq(¤t->sighand->siglock);
2545 sigorsets(&pending, ¤t->pending.signal,
2546 ¤t->signal->shared_pending.signal);
2547 spin_unlock_irq(¤t->sighand->siglock);
2549 /* Outside the lock because only this thread touches it. */
2550 sigandsets(&pending, ¤t->blocked, &pending);
2553 if (!copy_to_user(set, &pending, sigsetsize))
2561 * sys_rt_sigpending - examine a pending signal that has been raised
2563 * @set: stores pending signals
2564 * @sigsetsize: size of sigset_t type or larger
2566 SYSCALL_DEFINE2(rt_sigpending, sigset_t __user *, set, size_t, sigsetsize)
2568 return do_sigpending(set, sigsetsize);
2571 #ifndef HAVE_ARCH_COPY_SIGINFO_TO_USER
2573 int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from)
2577 if (!access_ok (VERIFY_WRITE, to, sizeof(siginfo_t)))
2579 if (from->si_code < 0)
2580 return __copy_to_user(to, from, sizeof(siginfo_t))
2583 * If you change siginfo_t structure, please be sure
2584 * this code is fixed accordingly.
2585 * Please remember to update the signalfd_copyinfo() function
2586 * inside fs/signalfd.c too, in case siginfo_t changes.
2587 * It should never copy any pad contained in the structure
2588 * to avoid security leaks, but must copy the generic
2589 * 3 ints plus the relevant union member.
2591 err = __put_user(from->si_signo, &to->si_signo);
2592 err |= __put_user(from->si_errno, &to->si_errno);
2593 err |= __put_user((short)from->si_code, &to->si_code);
2594 switch (from->si_code & __SI_MASK) {
2596 err |= __put_user(from->si_pid, &to->si_pid);
2597 err |= __put_user(from->si_uid, &to->si_uid);
2600 err |= __put_user(from->si_tid, &to->si_tid);
2601 err |= __put_user(from->si_overrun, &to->si_overrun);
2602 err |= __put_user(from->si_ptr, &to->si_ptr);
2605 err |= __put_user(from->si_band, &to->si_band);
2606 err |= __put_user(from->si_fd, &to->si_fd);
2609 err |= __put_user(from->si_addr, &to->si_addr);
2610 #ifdef __ARCH_SI_TRAPNO
2611 err |= __put_user(from->si_trapno, &to->si_trapno);
2613 #ifdef BUS_MCEERR_AO
2615 * Other callers might not initialize the si_lsb field,
2616 * so check explicitly for the right codes here.
2618 if (from->si_code == BUS_MCEERR_AR || from->si_code == BUS_MCEERR_AO)
2619 err |= __put_user(from->si_addr_lsb, &to->si_addr_lsb);
2623 err |= __put_user(from->si_pid, &to->si_pid);
2624 err |= __put_user(from->si_uid, &to->si_uid);
2625 err |= __put_user(from->si_status, &to->si_status);
2626 err |= __put_user(from->si_utime, &to->si_utime);
2627 err |= __put_user(from->si_stime, &to->si_stime);
2629 case __SI_RT: /* This is not generated by the kernel as of now. */
2630 case __SI_MESGQ: /* But this is */
2631 err |= __put_user(from->si_pid, &to->si_pid);
2632 err |= __put_user(from->si_uid, &to->si_uid);
2633 err |= __put_user(from->si_ptr, &to->si_ptr);
2635 default: /* this is just in case for now ... */
2636 err |= __put_user(from->si_pid, &to->si_pid);
2637 err |= __put_user(from->si_uid, &to->si_uid);
2646 * do_sigtimedwait - wait for queued signals specified in @which
2647 * @which: queued signals to wait for
2648 * @info: if non-null, the signal's siginfo is returned here
2649 * @ts: upper bound on process time suspension
2651 int do_sigtimedwait(const sigset_t *which, siginfo_t *info,
2652 const struct timespec *ts)
2654 struct task_struct *tsk = current;
2655 long timeout = MAX_SCHEDULE_TIMEOUT;
2656 sigset_t mask = *which;
2660 if (!timespec_valid(ts))
2662 timeout = timespec_to_jiffies(ts);
2664 * We can be close to the next tick, add another one
2665 * to ensure we will wait at least the time asked for.
2667 if (ts->tv_sec || ts->tv_nsec)
2672 * Invert the set of allowed signals to get those we want to block.
2674 sigdelsetmask(&mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
2677 spin_lock_irq(&tsk->sighand->siglock);
2678 sig = dequeue_signal(tsk, &mask, info);
2679 if (!sig && timeout) {
2681 * None ready, temporarily unblock those we're interested
2682 * while we are sleeping in so that we'll be awakened when
2683 * they arrive. Unblocking is always fine, we can avoid
2684 * set_current_blocked().
2686 tsk->real_blocked = tsk->blocked;
2687 sigandsets(&tsk->blocked, &tsk->blocked, &mask);
2688 recalc_sigpending();
2689 spin_unlock_irq(&tsk->sighand->siglock);
2691 timeout = schedule_timeout_interruptible(timeout);
2693 spin_lock_irq(&tsk->sighand->siglock);
2694 __set_task_blocked(tsk, &tsk->real_blocked);
2695 siginitset(&tsk->real_blocked, 0);
2696 sig = dequeue_signal(tsk, &mask, info);
2698 spin_unlock_irq(&tsk->sighand->siglock);
2702 return timeout ? -EINTR : -EAGAIN;
2706 * sys_rt_sigtimedwait - synchronously wait for queued signals specified
2708 * @uthese: queued signals to wait for
2709 * @uinfo: if non-null, the signal's siginfo is returned here
2710 * @uts: upper bound on process time suspension
2711 * @sigsetsize: size of sigset_t type
2713 SYSCALL_DEFINE4(rt_sigtimedwait, const sigset_t __user *, uthese,
2714 siginfo_t __user *, uinfo, const struct timespec __user *, uts,
2722 /* XXX: Don't preclude handling different sized sigset_t's. */
2723 if (sigsetsize != sizeof(sigset_t))
2726 if (copy_from_user(&these, uthese, sizeof(these)))
2730 if (copy_from_user(&ts, uts, sizeof(ts)))
2734 ret = do_sigtimedwait(&these, &info, uts ? &ts : NULL);
2736 if (ret > 0 && uinfo) {
2737 if (copy_siginfo_to_user(uinfo, &info))
2745 * sys_kill - send a signal to a process
2746 * @pid: the PID of the process
2747 * @sig: signal to be sent
2749 SYSCALL_DEFINE2(kill, pid_t, pid, int, sig)
2751 struct siginfo info;
2753 info.si_signo = sig;
2755 info.si_code = SI_USER;
2756 info.si_pid = task_tgid_vnr(current);
2757 info.si_uid = current_uid();
2759 return kill_something_info(sig, &info, pid);
2763 do_send_specific(pid_t tgid, pid_t pid, int sig, struct siginfo *info)
2765 struct task_struct *p;
2769 p = find_task_by_vpid(pid);
2770 if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) {
2771 error = check_kill_permission(sig, info, p);
2773 * The null signal is a permissions and process existence
2774 * probe. No signal is actually delivered.
2776 if (!error && sig) {
2777 error = do_send_sig_info(sig, info, p, false);
2779 * If lock_task_sighand() failed we pretend the task
2780 * dies after receiving the signal. The window is tiny,
2781 * and the signal is private anyway.
2783 if (unlikely(error == -ESRCH))
2792 static int do_tkill(pid_t tgid, pid_t pid, int sig)
2794 struct siginfo info = {};
2796 info.si_signo = sig;
2798 info.si_code = SI_TKILL;
2799 info.si_pid = task_tgid_vnr(current);
2800 info.si_uid = current_uid();
2802 return do_send_specific(tgid, pid, sig, &info);
2806 * sys_tgkill - send signal to one specific thread
2807 * @tgid: the thread group ID of the thread
2808 * @pid: the PID of the thread
2809 * @sig: signal to be sent
2811 * This syscall also checks the @tgid and returns -ESRCH even if the PID
2812 * exists but it's not belonging to the target process anymore. This
2813 * method solves the problem of threads exiting and PIDs getting reused.
2815 SYSCALL_DEFINE3(tgkill, pid_t, tgid, pid_t, pid, int, sig)
2817 /* This is only valid for single tasks */
2818 if (pid <= 0 || tgid <= 0)
2821 return do_tkill(tgid, pid, sig);
2825 * sys_tkill - send signal to one specific task
2826 * @pid: the PID of the task
2827 * @sig: signal to be sent
2829 * Send a signal to only one task, even if it's a CLONE_THREAD task.
2831 SYSCALL_DEFINE2(tkill, pid_t, pid, int, sig)
2833 /* This is only valid for single tasks */
2837 return do_tkill(0, pid, sig);
2841 * sys_rt_sigqueueinfo - send signal information to a signal
2842 * @pid: the PID of the thread
2843 * @sig: signal to be sent
2844 * @uinfo: signal info to be sent
2846 SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
2847 siginfo_t __user *, uinfo)
2851 if (copy_from_user(&info, uinfo, sizeof(siginfo_t)))
2854 /* Not even root can pretend to send signals from the kernel.
2855 * Nor can they impersonate a kill()/tgkill(), which adds source info.
2857 if (info.si_code >= 0 || info.si_code == SI_TKILL) {
2858 /* We used to allow any < 0 si_code */
2859 WARN_ON_ONCE(info.si_code < 0);
2862 info.si_signo = sig;
2864 /* POSIX.1b doesn't mention process groups. */
2865 return kill_proc_info(sig, &info, pid);
2868 long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
2870 /* This is only valid for single tasks */
2871 if (pid <= 0 || tgid <= 0)
2874 /* Not even root can pretend to send signals from the kernel.
2875 * Nor can they impersonate a kill()/tgkill(), which adds source info.
2877 if (info->si_code >= 0 || info->si_code == SI_TKILL) {
2878 /* We used to allow any < 0 si_code */
2879 WARN_ON_ONCE(info->si_code < 0);
2882 info->si_signo = sig;
2884 return do_send_specific(tgid, pid, sig, info);
2887 SYSCALL_DEFINE4(rt_tgsigqueueinfo, pid_t, tgid, pid_t, pid, int, sig,
2888 siginfo_t __user *, uinfo)
2892 if (copy_from_user(&info, uinfo, sizeof(siginfo_t)))
2895 return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
2898 int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
2900 struct task_struct *t = current;
2901 struct k_sigaction *k;
2904 if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig)))
2907 k = &t->sighand->action[sig-1];
2909 spin_lock_irq(¤t->sighand->siglock);
2914 sigdelsetmask(&act->sa.sa_mask,
2915 sigmask(SIGKILL) | sigmask(SIGSTOP));
2919 * "Setting a signal action to SIG_IGN for a signal that is
2920 * pending shall cause the pending signal to be discarded,
2921 * whether or not it is blocked."
2923 * "Setting a signal action to SIG_DFL for a signal that is
2924 * pending and whose default action is to ignore the signal
2925 * (for example, SIGCHLD), shall cause the pending signal to
2926 * be discarded, whether or not it is blocked"
2928 if (sig_handler_ignored(sig_handler(t, sig), sig)) {
2930 sigaddset(&mask, sig);
2931 rm_from_queue_full(&mask, &t->signal->shared_pending);
2933 rm_from_queue_full(&mask, &t->pending);
2935 } while (t != current);
2939 spin_unlock_irq(¤t->sighand->siglock);
2944 do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long sp)
2949 oss.ss_sp = (void __user *) current->sas_ss_sp;
2950 oss.ss_size = current->sas_ss_size;
2951 oss.ss_flags = sas_ss_flags(sp);
2959 if (!access_ok(VERIFY_READ, uss, sizeof(*uss)))
2961 error = __get_user(ss_sp, &uss->ss_sp) |
2962 __get_user(ss_flags, &uss->ss_flags) |
2963 __get_user(ss_size, &uss->ss_size);
2968 if (on_sig_stack(sp))
2973 * Note - this code used to test ss_flags incorrectly:
2974 * old code may have been written using ss_flags==0
2975 * to mean ss_flags==SS_ONSTACK (as this was the only
2976 * way that worked) - this fix preserves that older
2979 if (ss_flags != SS_DISABLE && ss_flags != SS_ONSTACK && ss_flags != 0)
2982 if (ss_flags == SS_DISABLE) {
2987 if (ss_size < MINSIGSTKSZ)
2991 current->sas_ss_sp = (unsigned long) ss_sp;
2992 current->sas_ss_size = ss_size;
2998 if (!access_ok(VERIFY_WRITE, uoss, sizeof(*uoss)))
3000 error = __put_user(oss.ss_sp, &uoss->ss_sp) |
3001 __put_user(oss.ss_size, &uoss->ss_size) |
3002 __put_user(oss.ss_flags, &uoss->ss_flags);
3009 #ifdef __ARCH_WANT_SYS_SIGPENDING
3012 * sys_sigpending - examine pending signals
3013 * @set: where mask of pending signal is returned
3015 SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, set)
3017 return do_sigpending(set, sizeof(*set));
3022 #ifdef __ARCH_WANT_SYS_SIGPROCMASK
3024 * sys_sigprocmask - examine and change blocked signals
3025 * @how: whether to add, remove, or set signals
3026 * @nset: signals to add or remove (if non-null)
3027 * @oset: previous value of signal mask if non-null
3029 * Some platforms have their own version with special arguments;
3030 * others support only sys_rt_sigprocmask.
3033 SYSCALL_DEFINE3(sigprocmask, int, how, old_sigset_t __user *, nset,
3034 old_sigset_t __user *, oset)
3036 old_sigset_t old_set, new_set;
3037 sigset_t new_blocked;
3039 old_set = current->blocked.sig[0];
3042 if (copy_from_user(&new_set, nset, sizeof(*nset)))
3044 new_set &= ~(sigmask(SIGKILL) | sigmask(SIGSTOP));
3046 new_blocked = current->blocked;
3050 sigaddsetmask(&new_blocked, new_set);
3053 sigdelsetmask(&new_blocked, new_set);
3056 new_blocked.sig[0] = new_set;
3062 set_current_blocked(&new_blocked);
3066 if (copy_to_user(oset, &old_set, sizeof(*oset)))
3072 #endif /* __ARCH_WANT_SYS_SIGPROCMASK */
3074 #ifdef __ARCH_WANT_SYS_RT_SIGACTION
3076 * sys_rt_sigaction - alter an action taken by a process
3077 * @sig: signal to be sent
3078 * @act: new sigaction
3079 * @oact: used to save the previous sigaction
3080 * @sigsetsize: size of sigset_t type
3082 SYSCALL_DEFINE4(rt_sigaction, int, sig,
3083 const struct sigaction __user *, act,
3084 struct sigaction __user *, oact,
3087 struct k_sigaction new_sa, old_sa;
3090 /* XXX: Don't preclude handling different sized sigset_t's. */
3091 if (sigsetsize != sizeof(sigset_t))
3095 if (copy_from_user(&new_sa.sa, act, sizeof(new_sa.sa)))
3099 ret = do_sigaction(sig, act ? &new_sa : NULL, oact ? &old_sa : NULL);
3102 if (copy_to_user(oact, &old_sa.sa, sizeof(old_sa.sa)))
3108 #endif /* __ARCH_WANT_SYS_RT_SIGACTION */
3110 #ifdef __ARCH_WANT_SYS_SGETMASK
3113 * For backwards compatibility. Functionality superseded by sigprocmask.
3115 SYSCALL_DEFINE0(sgetmask)
3118 return current->blocked.sig[0];
3121 SYSCALL_DEFINE1(ssetmask, int, newmask)
3123 int old = current->blocked.sig[0];
3126 siginitset(&newset, newmask & ~(sigmask(SIGKILL) | sigmask(SIGSTOP)));
3127 set_current_blocked(&newset);
3131 #endif /* __ARCH_WANT_SGETMASK */
3133 #ifdef __ARCH_WANT_SYS_SIGNAL
3135 * For backwards compatibility. Functionality superseded by sigaction.
3137 SYSCALL_DEFINE2(signal, int, sig, __sighandler_t, handler)
3139 struct k_sigaction new_sa, old_sa;
3142 new_sa.sa.sa_handler = handler;
3143 new_sa.sa.sa_flags = SA_ONESHOT | SA_NOMASK;
3144 sigemptyset(&new_sa.sa.sa_mask);
3146 ret = do_sigaction(sig, &new_sa, &old_sa);
3148 return ret ? ret : (unsigned long)old_sa.sa.sa_handler;
3150 #endif /* __ARCH_WANT_SYS_SIGNAL */
3152 #ifdef __ARCH_WANT_SYS_PAUSE
3154 SYSCALL_DEFINE0(pause)
3156 while (!signal_pending(current)) {
3157 current->state = TASK_INTERRUPTIBLE;
3160 return -ERESTARTNOHAND;
3165 #ifdef __ARCH_WANT_SYS_RT_SIGSUSPEND
3167 * sys_rt_sigsuspend - replace the signal mask for a value with the
3168 * @unewset value until a signal is received
3169 * @unewset: new signal mask value
3170 * @sigsetsize: size of sigset_t type
3172 SYSCALL_DEFINE2(rt_sigsuspend, sigset_t __user *, unewset, size_t, sigsetsize)
3176 /* XXX: Don't preclude handling different sized sigset_t's. */
3177 if (sigsetsize != sizeof(sigset_t))
3180 if (copy_from_user(&newset, unewset, sizeof(newset)))
3182 sigdelsetmask(&newset, sigmask(SIGKILL)|sigmask(SIGSTOP));
3184 current->saved_sigmask = current->blocked;
3185 set_current_blocked(&newset);
3187 current->state = TASK_INTERRUPTIBLE;
3189 set_restore_sigmask();
3190 return -ERESTARTNOHAND;
3192 #endif /* __ARCH_WANT_SYS_RT_SIGSUSPEND */
3194 __attribute__((weak)) const char *arch_vma_name(struct vm_area_struct *vma)
3199 void __init signals_init(void)
3201 sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC);
3204 #ifdef CONFIG_KGDB_KDB
3205 #include <linux/kdb.h>
3207 * kdb_send_sig_info - Allows kdb to send signals without exposing
3208 * signal internals. This function checks if the required locks are
3209 * available before calling the main signal code, to avoid kdb
3213 kdb_send_sig_info(struct task_struct *t, struct siginfo *info)
3215 static struct task_struct *kdb_prev_t;
3217 if (!spin_trylock(&t->sighand->siglock)) {
3218 kdb_printf("Can't do kill command now.\n"
3219 "The sigmask lock is held somewhere else in "
3220 "kernel, try again later\n");
3223 spin_unlock(&t->sighand->siglock);
3224 new_t = kdb_prev_t != t;
3226 if (t->state != TASK_RUNNING && new_t) {
3227 kdb_printf("Process is not RUNNING, sending a signal from "
3228 "kdb risks deadlock\n"
3229 "on the run queue locks. "
3230 "The signal has _not_ been sent.\n"
3231 "Reissue the kill command if you want to risk "
3235 sig = info->si_signo;
3236 if (send_sig_info(sig, info, t))
3237 kdb_printf("Fail to deliver Signal %d to process %d.\n",
3240 kdb_printf("Signal %d is sent to process %d.\n", sig, t->pid);
3242 #endif /* CONFIG_KGDB_KDB */