Root/kernel/signal.c

1/*
2 * linux/kernel/signal.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
6 * 1997-11-02 Modified for POSIX.1b signals by Richard Henderson
7 *
8 * 2003-06-02 Jim Houston - Concurrent Computer Corp.
9 * Changes to use preallocated sigqueue structures
10 * to allow signals to be sent reliably.
11 */
12
13#include <linux/slab.h>
14#include <linux/module.h>
15#include <linux/init.h>
16#include <linux/sched.h>
17#include <linux/fs.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>
33
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() */
39
40/*
41 * SLAB caches for signal bits.
42 */
43
44static struct kmem_cache *sigqueue_cachep;
45
46int print_fatal_signals __read_mostly;
47
48static void __user *sig_handler(struct task_struct *t, int sig)
49{
50    return t->sighand->action[sig - 1].sa.sa_handler;
51}
52
53static int sig_handler_ignored(void __user *handler, int sig)
54{
55    /* Is it explicitly or implicitly ignored? */
56    return handler == SIG_IGN ||
57        (handler == SIG_DFL && sig_kernel_ignore(sig));
58}
59
60static int sig_task_ignored(struct task_struct *t, int sig,
61        int from_ancestor_ns)
62{
63    void __user *handler;
64
65    handler = sig_handler(t, sig);
66
67    if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) &&
68            handler == SIG_DFL && !from_ancestor_ns)
69        return 1;
70
71    return sig_handler_ignored(handler, sig);
72}
73
74static int sig_ignored(struct task_struct *t, int sig, int from_ancestor_ns)
75{
76    /*
77     * Blocked signals are never ignored, since the
78     * signal handler may change by the time it is
79     * unblocked.
80     */
81    if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
82        return 0;
83
84    if (!sig_task_ignored(t, sig, from_ancestor_ns))
85        return 0;
86
87    /*
88     * Tracers may want to know about even ignored signals.
89     */
90    return !tracehook_consider_ignored_signal(t, sig);
91}
92
93/*
94 * Re-calculate pending state from the set of locally pending
95 * signals, globally pending signals, and blocked signals.
96 */
97static inline int has_pending_signals(sigset_t *signal, sigset_t *blocked)
98{
99    unsigned long ready;
100    long i;
101
102    switch (_NSIG_WORDS) {
103    default:
104        for (i = _NSIG_WORDS, ready = 0; --i >= 0 ;)
105            ready |= signal->sig[i] &~ blocked->sig[i];
106        break;
107
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];
112        break;
113
114    case 2: ready = signal->sig[1] &~ blocked->sig[1];
115        ready |= signal->sig[0] &~ blocked->sig[0];
116        break;
117
118    case 1: ready = signal->sig[0] &~ blocked->sig[0];
119    }
120    return ready != 0;
121}
122
123#define PENDING(p,b) has_pending_signals(&(p)->signal, (b))
124
125static int recalc_sigpending_tsk(struct task_struct *t)
126{
127    if ((t->group_stop & GROUP_STOP_PENDING) ||
128        PENDING(&t->pending, &t->blocked) ||
129        PENDING(&t->signal->shared_pending, &t->blocked)) {
130        set_tsk_thread_flag(t, TIF_SIGPENDING);
131        return 1;
132    }
133    /*
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.
137     */
138    return 0;
139}
140
141/*
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.
144 */
145void recalc_sigpending_and_wake(struct task_struct *t)
146{
147    if (recalc_sigpending_tsk(t))
148        signal_wake_up(t, 0);
149}
150
151void recalc_sigpending(void)
152{
153    if (unlikely(tracehook_force_sigpending()))
154        set_thread_flag(TIF_SIGPENDING);
155    else if (!recalc_sigpending_tsk(current) && !freezing(current))
156        clear_thread_flag(TIF_SIGPENDING);
157
158}
159
160/* Given the mask, find the first available signal that should be serviced. */
161
162#define SYNCHRONOUS_MASK \
163    (sigmask(SIGSEGV) | sigmask(SIGBUS) | sigmask(SIGILL) | \
164     sigmask(SIGTRAP) | sigmask(SIGFPE))
165
166int next_signal(struct sigpending *pending, sigset_t *mask)
167{
168    unsigned long i, *s, *m, x;
169    int sig = 0;
170
171    s = pending->signal.sig;
172    m = mask->sig;
173
174    /*
175     * Handle the first word specially: it contains the
176     * synchronous signals that need to be dequeued first.
177     */
178    x = *s &~ *m;
179    if (x) {
180        if (x & SYNCHRONOUS_MASK)
181            x &= SYNCHRONOUS_MASK;
182        sig = ffz(~x) + 1;
183        return sig;
184    }
185
186    switch (_NSIG_WORDS) {
187    default:
188        for (i = 1; i < _NSIG_WORDS; ++i) {
189            x = *++s &~ *++m;
190            if (!x)
191                continue;
192            sig = ffz(~x) + i*_NSIG_BPW + 1;
193            break;
194        }
195        break;
196
197    case 2:
198        x = s[1] &~ m[1];
199        if (!x)
200            break;
201        sig = ffz(~x) + _NSIG_BPW + 1;
202        break;
203
204    case 1:
205        /* Nothing to do */
206        break;
207    }
208
209    return sig;
210}
211
212static inline void print_dropped_signal(int sig)
213{
214    static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
215
216    if (!print_fatal_signals)
217        return;
218
219    if (!__ratelimit(&ratelimit_state))
220        return;
221
222    printk(KERN_INFO "%s/%d: reached RLIMIT_SIGPENDING, dropped signal %d\n",
223                current->comm, current->pid, sig);
224}
225
226/**
227 * task_clear_group_stop_trapping - clear group stop trapping bit
228 * @task: target task
229 *
230 * If GROUP_STOP_TRAPPING is set, a ptracer is waiting for us. Clear it
231 * and wake up the ptracer. Note that we don't need any further locking.
232 * @task->siglock guarantees that @task->parent points to the ptracer.
233 *
234 * CONTEXT:
235 * Must be called with @task->sighand->siglock held.
236 */
237static void task_clear_group_stop_trapping(struct task_struct *task)
238{
239    if (unlikely(task->group_stop & GROUP_STOP_TRAPPING)) {
240        task->group_stop &= ~GROUP_STOP_TRAPPING;
241        __wake_up_sync_key(&task->parent->signal->wait_chldexit,
242                   TASK_UNINTERRUPTIBLE, 1, task);
243    }
244}
245
246/**
247 * task_clear_group_stop_pending - clear pending group stop
248 * @task: target task
249 *
250 * Clear group stop states for @task.
251 *
252 * CONTEXT:
253 * Must be called with @task->sighand->siglock held.
254 */
255void task_clear_group_stop_pending(struct task_struct *task)
256{
257    task->group_stop &= ~(GROUP_STOP_PENDING | GROUP_STOP_CONSUME |
258                  GROUP_STOP_DEQUEUED);
259}
260
261/**
262 * task_participate_group_stop - participate in a group stop
263 * @task: task participating in a group stop
264 *
265 * @task has GROUP_STOP_PENDING set and is participating in a group stop.
266 * Group stop states are cleared and the group stop count is consumed if
267 * %GROUP_STOP_CONSUME was set. If the consumption completes the group
268 * stop, the appropriate %SIGNAL_* flags are set.
269 *
270 * CONTEXT:
271 * Must be called with @task->sighand->siglock held.
272 *
273 * RETURNS:
274 * %true if group stop completion should be notified to the parent, %false
275 * otherwise.
276 */
277static bool task_participate_group_stop(struct task_struct *task)
278{
279    struct signal_struct *sig = task->signal;
280    bool consume = task->group_stop & GROUP_STOP_CONSUME;
281
282    WARN_ON_ONCE(!(task->group_stop & GROUP_STOP_PENDING));
283
284    task_clear_group_stop_pending(task);
285
286    if (!consume)
287        return false;
288
289    if (!WARN_ON_ONCE(sig->group_stop_count == 0))
290        sig->group_stop_count--;
291
292    /*
293     * Tell the caller to notify completion iff we are entering into a
294     * fresh group stop. Read comment in do_signal_stop() for details.
295     */
296    if (!sig->group_stop_count && !(sig->flags & SIGNAL_STOP_STOPPED)) {
297        sig->flags = SIGNAL_STOP_STOPPED;
298        return true;
299    }
300    return false;
301}
302
303/*
304 * allocate a new signal queue record
305 * - this may be called without locks if and only if t == current, otherwise an
306 * appropriate lock must be held to stop the target task from exiting
307 */
308static struct sigqueue *
309__sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimit)
310{
311    struct sigqueue *q = NULL;
312    struct user_struct *user;
313
314    /*
315     * Protect access to @t credentials. This can go away when all
316     * callers hold rcu read lock.
317     */
318    rcu_read_lock();
319    user = get_uid(__task_cred(t)->user);
320    atomic_inc(&user->sigpending);
321    rcu_read_unlock();
322
323    if (override_rlimit ||
324        atomic_read(&user->sigpending) <=
325            task_rlimit(t, RLIMIT_SIGPENDING)) {
326        q = kmem_cache_alloc(sigqueue_cachep, flags);
327    } else {
328        print_dropped_signal(sig);
329    }
330
331    if (unlikely(q == NULL)) {
332        atomic_dec(&user->sigpending);
333        free_uid(user);
334    } else {
335        INIT_LIST_HEAD(&q->list);
336        q->flags = 0;
337        q->user = user;
338    }
339
340    return q;
341}
342
343static void __sigqueue_free(struct sigqueue *q)
344{
345    if (q->flags & SIGQUEUE_PREALLOC)
346        return;
347    atomic_dec(&q->user->sigpending);
348    free_uid(q->user);
349    kmem_cache_free(sigqueue_cachep, q);
350}
351
352void flush_sigqueue(struct sigpending *queue)
353{
354    struct sigqueue *q;
355
356    sigemptyset(&queue->signal);
357    while (!list_empty(&queue->list)) {
358        q = list_entry(queue->list.next, struct sigqueue , list);
359        list_del_init(&q->list);
360        __sigqueue_free(q);
361    }
362}
363
364/*
365 * Flush all pending signals for a task.
366 */
367void __flush_signals(struct task_struct *t)
368{
369    clear_tsk_thread_flag(t, TIF_SIGPENDING);
370    flush_sigqueue(&t->pending);
371    flush_sigqueue(&t->signal->shared_pending);
372}
373
374void flush_signals(struct task_struct *t)
375{
376    unsigned long flags;
377
378    spin_lock_irqsave(&t->sighand->siglock, flags);
379    __flush_signals(t);
380    spin_unlock_irqrestore(&t->sighand->siglock, flags);
381}
382
383static void __flush_itimer_signals(struct sigpending *pending)
384{
385    sigset_t signal, retain;
386    struct sigqueue *q, *n;
387
388    signal = pending->signal;
389    sigemptyset(&retain);
390
391    list_for_each_entry_safe(q, n, &pending->list, list) {
392        int sig = q->info.si_signo;
393
394        if (likely(q->info.si_code != SI_TIMER)) {
395            sigaddset(&retain, sig);
396        } else {
397            sigdelset(&signal, sig);
398            list_del_init(&q->list);
399            __sigqueue_free(q);
400        }
401    }
402
403    sigorsets(&pending->signal, &signal, &retain);
404}
405
406void flush_itimer_signals(void)
407{
408    struct task_struct *tsk = current;
409    unsigned long flags;
410
411    spin_lock_irqsave(&tsk->sighand->siglock, flags);
412    __flush_itimer_signals(&tsk->pending);
413    __flush_itimer_signals(&tsk->signal->shared_pending);
414    spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
415}
416
417void ignore_signals(struct task_struct *t)
418{
419    int i;
420
421    for (i = 0; i < _NSIG; ++i)
422        t->sighand->action[i].sa.sa_handler = SIG_IGN;
423
424    flush_signals(t);
425}
426
427/*
428 * Flush all handlers for a task.
429 */
430
431void
432flush_signal_handlers(struct task_struct *t, int force_default)
433{
434    int i;
435    struct k_sigaction *ka = &t->sighand->action[0];
436    for (i = _NSIG ; i != 0 ; i--) {
437        if (force_default || ka->sa.sa_handler != SIG_IGN)
438            ka->sa.sa_handler = SIG_DFL;
439        ka->sa.sa_flags = 0;
440        sigemptyset(&ka->sa.sa_mask);
441        ka++;
442    }
443}
444
445int unhandled_signal(struct task_struct *tsk, int sig)
446{
447    void __user *handler = tsk->sighand->action[sig-1].sa.sa_handler;
448    if (is_global_init(tsk))
449        return 1;
450    if (handler != SIG_IGN && handler != SIG_DFL)
451        return 0;
452    return !tracehook_consider_fatal_signal(tsk, sig);
453}
454
455/*
456 * Notify the system that a driver wants to block all signals for this
457 * process, and wants to be notified if any signals at all were to be
458 * sent/acted upon. If the notifier routine returns non-zero, then the
459 * signal will be acted upon after all. If the notifier routine returns 0,
460 * then then signal will be blocked. Only one block per process is
461 * allowed. priv is a pointer to private data that the notifier routine
462 * can use to determine if the signal should be blocked or not.
463 */
464void
465block_all_signals(int (*notifier)(void *priv), void *priv, sigset_t *mask)
466{
467    unsigned long flags;
468
469    spin_lock_irqsave(&current->sighand->siglock, flags);
470    current->notifier_mask = mask;
471    current->notifier_data = priv;
472    current->notifier = notifier;
473    spin_unlock_irqrestore(&current->sighand->siglock, flags);
474}
475
476/* Notify the system that blocking has ended. */
477
478void
479unblock_all_signals(void)
480{
481    unsigned long flags;
482
483    spin_lock_irqsave(&current->sighand->siglock, flags);
484    current->notifier = NULL;
485    current->notifier_data = NULL;
486    recalc_sigpending();
487    spin_unlock_irqrestore(&current->sighand->siglock, flags);
488}
489
490static void collect_signal(int sig, struct sigpending *list, siginfo_t *info)
491{
492    struct sigqueue *q, *first = NULL;
493
494    /*
495     * Collect the siginfo appropriate to this signal. Check if
496     * there is another siginfo for the same signal.
497    */
498    list_for_each_entry(q, &list->list, list) {
499        if (q->info.si_signo == sig) {
500            if (first)
501                goto still_pending;
502            first = q;
503        }
504    }
505
506    sigdelset(&list->signal, sig);
507
508    if (first) {
509still_pending:
510        list_del_init(&first->list);
511        copy_siginfo(info, &first->info);
512        __sigqueue_free(first);
513    } else {
514        /*
515         * Ok, it wasn't in the queue. This must be
516         * a fast-pathed signal or we must have been
517         * out of queue space. So zero out the info.
518         */
519        info->si_signo = sig;
520        info->si_errno = 0;
521        info->si_code = SI_USER;
522        info->si_pid = 0;
523        info->si_uid = 0;
524    }
525}
526
527static int __dequeue_signal(struct sigpending *pending, sigset_t *mask,
528            siginfo_t *info)
529{
530    int sig = next_signal(pending, mask);
531
532    if (sig) {
533        if (current->notifier) {
534            if (sigismember(current->notifier_mask, sig)) {
535                if (!(current->notifier)(current->notifier_data)) {
536                    clear_thread_flag(TIF_SIGPENDING);
537                    return 0;
538                }
539            }
540        }
541
542        collect_signal(sig, pending, info);
543    }
544
545    return sig;
546}
547
548/*
549 * Dequeue a signal and return the element to the caller, which is
550 * expected to free it.
551 *
552 * All callers have to hold the siglock.
553 */
554int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
555{
556    int signr;
557
558    /* We only dequeue private signals from ourselves, we don't let
559     * signalfd steal them
560     */
561    signr = __dequeue_signal(&tsk->pending, mask, info);
562    if (!signr) {
563        signr = __dequeue_signal(&tsk->signal->shared_pending,
564                     mask, info);
565        /*
566         * itimer signal ?
567         *
568         * itimers are process shared and we restart periodic
569         * itimers in the signal delivery path to prevent DoS
570         * attacks in the high resolution timer case. This is
571         * compliant with the old way of self-restarting
572         * itimers, as the SIGALRM is a legacy signal and only
573         * queued once. Changing the restart behaviour to
574         * restart the timer in the signal dequeue path is
575         * reducing the timer noise on heavy loaded !highres
576         * systems too.
577         */
578        if (unlikely(signr == SIGALRM)) {
579            struct hrtimer *tmr = &tsk->signal->real_timer;
580
581            if (!hrtimer_is_queued(tmr) &&
582                tsk->signal->it_real_incr.tv64 != 0) {
583                hrtimer_forward(tmr, tmr->base->get_time(),
584                        tsk->signal->it_real_incr);
585                hrtimer_restart(tmr);
586            }
587        }
588    }
589
590    recalc_sigpending();
591    if (!signr)
592        return 0;
593
594    if (unlikely(sig_kernel_stop(signr))) {
595        /*
596         * Set a marker that we have dequeued a stop signal. Our
597         * caller might release the siglock and then the pending
598         * stop signal it is about to process is no longer in the
599         * pending bitmasks, but must still be cleared by a SIGCONT
600         * (and overruled by a SIGKILL). So those cases clear this
601         * shared flag after we've set it. Note that this flag may
602         * remain set after the signal we return is ignored or
603         * handled. That doesn't matter because its only purpose
604         * is to alert stop-signal processing code when another
605         * processor has come along and cleared the flag.
606         */
607        current->group_stop |= GROUP_STOP_DEQUEUED;
608    }
609    if ((info->si_code & __SI_MASK) == __SI_TIMER && info->si_sys_private) {
610        /*
611         * Release the siglock to ensure proper locking order
612         * of timer locks outside of siglocks. Note, we leave
613         * irqs disabled here, since the posix-timers code is
614         * about to disable them again anyway.
615         */
616        spin_unlock(&tsk->sighand->siglock);
617        do_schedule_next_timer(info);
618        spin_lock(&tsk->sighand->siglock);
619    }
620    return signr;
621}
622
623/*
624 * Tell a process that it has a new active signal..
625 *
626 * NOTE! we rely on the previous spin_lock to
627 * lock interrupts for us! We can only be called with
628 * "siglock" held, and the local interrupt must
629 * have been disabled when that got acquired!
630 *
631 * No need to set need_resched since signal event passing
632 * goes through ->blocked
633 */
634void signal_wake_up(struct task_struct *t, int resume)
635{
636    unsigned int mask;
637
638    set_tsk_thread_flag(t, TIF_SIGPENDING);
639
640    /*
641     * For SIGKILL, we want to wake it up in the stopped/traced/killable
642     * case. We don't check t->state here because there is a race with it
643     * executing another processor and just now entering stopped state.
644     * By using wake_up_state, we ensure the process will wake up and
645     * handle its death signal.
646     */
647    mask = TASK_INTERRUPTIBLE;
648    if (resume)
649        mask |= TASK_WAKEKILL;
650    if (!wake_up_state(t, mask))
651        kick_process(t);
652}
653
654/*
655 * Remove signals in mask from the pending set and queue.
656 * Returns 1 if any signals were found.
657 *
658 * All callers must be holding the siglock.
659 *
660 * This version takes a sigset mask and looks at all signals,
661 * not just those in the first mask word.
662 */
663static int rm_from_queue_full(sigset_t *mask, struct sigpending *s)
664{
665    struct sigqueue *q, *n;
666    sigset_t m;
667
668    sigandsets(&m, mask, &s->signal);
669    if (sigisemptyset(&m))
670        return 0;
671
672    sigandnsets(&s->signal, &s->signal, mask);
673    list_for_each_entry_safe(q, n, &s->list, list) {
674        if (sigismember(mask, q->info.si_signo)) {
675            list_del_init(&q->list);
676            __sigqueue_free(q);
677        }
678    }
679    return 1;
680}
681/*
682 * Remove signals in mask from the pending set and queue.
683 * Returns 1 if any signals were found.
684 *
685 * All callers must be holding the siglock.
686 */
687static int rm_from_queue(unsigned long mask, struct sigpending *s)
688{
689    struct sigqueue *q, *n;
690
691    if (!sigtestsetmask(&s->signal, mask))
692        return 0;
693
694    sigdelsetmask(&s->signal, mask);
695    list_for_each_entry_safe(q, n, &s->list, list) {
696        if (q->info.si_signo < SIGRTMIN &&
697            (mask & sigmask(q->info.si_signo))) {
698            list_del_init(&q->list);
699            __sigqueue_free(q);
700        }
701    }
702    return 1;
703}
704
705static inline int is_si_special(const struct siginfo *info)
706{
707    return info <= SEND_SIG_FORCED;
708}
709
710static inline bool si_fromuser(const struct siginfo *info)
711{
712    return info == SEND_SIG_NOINFO ||
713        (!is_si_special(info) && SI_FROMUSER(info));
714}
715
716/*
717 * called with RCU read lock from check_kill_permission()
718 */
719static int kill_ok_by_cred(struct task_struct *t)
720{
721    const struct cred *cred = current_cred();
722    const struct cred *tcred = __task_cred(t);
723
724    if (cred->user->user_ns == tcred->user->user_ns &&
725        (cred->euid == tcred->suid ||
726         cred->euid == tcred->uid ||
727         cred->uid == tcred->suid ||
728         cred->uid == tcred->uid))
729        return 1;
730
731    if (ns_capable(tcred->user->user_ns, CAP_KILL))
732        return 1;
733
734    return 0;
735}
736
737/*
738 * Bad permissions for sending the signal
739 * - the caller must hold the RCU read lock
740 */
741static int check_kill_permission(int sig, struct siginfo *info,
742                 struct task_struct *t)
743{
744    struct pid *sid;
745    int error;
746
747    if (!valid_signal(sig))
748        return -EINVAL;
749
750    if (!si_fromuser(info))
751        return 0;
752
753    error = audit_signal_info(sig, t); /* Let audit system see the signal */
754    if (error)
755        return error;
756
757    if (!same_thread_group(current, t) &&
758        !kill_ok_by_cred(t)) {
759        switch (sig) {
760        case SIGCONT:
761            sid = task_session(t);
762            /*
763             * We don't return the error if sid == NULL. The
764             * task was unhashed, the caller must notice this.
765             */
766            if (!sid || sid == task_session(current))
767                break;
768        default:
769            return -EPERM;
770        }
771    }
772
773    return security_task_kill(t, info, sig, 0);
774}
775
776/*
777 * Handle magic process-wide effects of stop/continue signals. Unlike
778 * the signal actions, these happen immediately at signal-generation
779 * time regardless of blocking, ignoring, or handling. This does the
780 * actual continuing for SIGCONT, but not the actual stopping for stop
781 * signals. The process stop is done as a signal action for SIG_DFL.
782 *
783 * Returns true if the signal should be actually delivered, otherwise
784 * it should be dropped.
785 */
786static int prepare_signal(int sig, struct task_struct *p, int from_ancestor_ns)
787{
788    struct signal_struct *signal = p->signal;
789    struct task_struct *t;
790
791    if (unlikely(signal->flags & SIGNAL_GROUP_EXIT)) {
792        /*
793         * The process is in the middle of dying, nothing to do.
794         */
795    } else if (sig_kernel_stop(sig)) {
796        /*
797         * This is a stop signal. Remove SIGCONT from all queues.
798         */
799        rm_from_queue(sigmask(SIGCONT), &signal->shared_pending);
800        t = p;
801        do {
802            rm_from_queue(sigmask(SIGCONT), &t->pending);
803        } while_each_thread(p, t);
804    } else if (sig == SIGCONT) {
805        unsigned int why;
806        /*
807         * Remove all stop signals from all queues, wake all threads.
808         */
809        rm_from_queue(SIG_KERNEL_STOP_MASK, &signal->shared_pending);
810        t = p;
811        do {
812            task_clear_group_stop_pending(t);
813            rm_from_queue(SIG_KERNEL_STOP_MASK, &t->pending);
814            wake_up_state(t, __TASK_STOPPED);
815        } while_each_thread(p, t);
816
817        /*
818         * Notify the parent with CLD_CONTINUED if we were stopped.
819         *
820         * If we were in the middle of a group stop, we pretend it
821         * was already finished, and then continued. Since SIGCHLD
822         * doesn't queue we report only CLD_STOPPED, as if the next
823         * CLD_CONTINUED was dropped.
824         */
825        why = 0;
826        if (signal->flags & SIGNAL_STOP_STOPPED)
827            why |= SIGNAL_CLD_CONTINUED;
828        else if (signal->group_stop_count)
829            why |= SIGNAL_CLD_STOPPED;
830
831        if (why) {
832            /*
833             * The first thread which returns from do_signal_stop()
834             * will take ->siglock, notice SIGNAL_CLD_MASK, and
835             * notify its parent. See get_signal_to_deliver().
836             */
837            signal->flags = why | SIGNAL_STOP_CONTINUED;
838            signal->group_stop_count = 0;
839            signal->group_exit_code = 0;
840        }
841    }
842
843    return !sig_ignored(p, sig, from_ancestor_ns);
844}
845
846/*
847 * Test if P wants to take SIG. After we've checked all threads with this,
848 * it's equivalent to finding no threads not blocking SIG. Any threads not
849 * blocking SIG were ruled out because they are not running and already
850 * have pending signals. Such threads will dequeue from the shared queue
851 * as soon as they're available, so putting the signal on the shared queue
852 * will be equivalent to sending it to one such thread.
853 */
854static inline int wants_signal(int sig, struct task_struct *p)
855{
856    if (sigismember(&p->blocked, sig))
857        return 0;
858    if (p->flags & PF_EXITING)
859        return 0;
860    if (sig == SIGKILL)
861        return 1;
862    if (task_is_stopped_or_traced(p))
863        return 0;
864    return task_curr(p) || !signal_pending(p);
865}
866
867static void complete_signal(int sig, struct task_struct *p, int group)
868{
869    struct signal_struct *signal = p->signal;
870    struct task_struct *t;
871
872    /*
873     * Now find a thread we can wake up to take the signal off the queue.
874     *
875     * If the main thread wants the signal, it gets first crack.
876     * Probably the least surprising to the average bear.
877     */
878    if (wants_signal(sig, p))
879        t = p;
880    else if (!group || thread_group_empty(p))
881        /*
882         * There is just one thread and it does not need to be woken.
883         * It will dequeue unblocked signals before it runs again.
884         */
885        return;
886    else {
887        /*
888         * Otherwise try to find a suitable thread.
889         */
890        t = signal->curr_target;
891        while (!wants_signal(sig, t)) {
892            t = next_thread(t);
893            if (t == signal->curr_target)
894                /*
895                 * No thread needs to be woken.
896                 * Any eligible threads will see
897                 * the signal in the queue soon.
898                 */
899                return;
900        }
901        signal->curr_target = t;
902    }
903
904    /*
905     * Found a killable thread. If the signal will be fatal,
906     * then start taking the whole group down immediately.
907     */
908    if (sig_fatal(p, sig) &&
909        !(signal->flags & (SIGNAL_UNKILLABLE | SIGNAL_GROUP_EXIT)) &&
910        !sigismember(&t->real_blocked, sig) &&
911        (sig == SIGKILL ||
912         !tracehook_consider_fatal_signal(t, sig))) {
913        /*
914         * This signal will be fatal to the whole group.
915         */
916        if (!sig_kernel_coredump(sig)) {
917            /*
918             * Start a group exit and wake everybody up.
919             * This way we don't have other threads
920             * running and doing things after a slower
921             * thread has the fatal signal pending.
922             */
923            signal->flags = SIGNAL_GROUP_EXIT;
924            signal->group_exit_code = sig;
925            signal->group_stop_count = 0;
926            t = p;
927            do {
928                task_clear_group_stop_pending(t);
929                sigaddset(&t->pending.signal, SIGKILL);
930                signal_wake_up(t, 1);
931            } while_each_thread(p, t);
932            return;
933        }
934    }
935
936    /*
937     * The signal is already in the shared-pending queue.
938     * Tell the chosen thread to wake up and dequeue it.
939     */
940    signal_wake_up(t, sig == SIGKILL);
941    return;
942}
943
944static inline int legacy_queue(struct sigpending *signals, int sig)
945{
946    return (sig < SIGRTMIN) && sigismember(&signals->signal, sig);
947}
948
949static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
950            int group, int from_ancestor_ns)
951{
952    struct sigpending *pending;
953    struct sigqueue *q;
954    int override_rlimit;
955
956    trace_signal_generate(sig, info, t);
957
958    assert_spin_locked(&t->sighand->siglock);
959
960    if (!prepare_signal(sig, t, from_ancestor_ns))
961        return 0;
962
963    pending = group ? &t->signal->shared_pending : &t->pending;
964    /*
965     * Short-circuit ignored signals and support queuing
966     * exactly one non-rt signal, so that we can get more
967     * detailed information about the cause of the signal.
968     */
969    if (legacy_queue(pending, sig))
970        return 0;
971    /*
972     * fast-pathed signals for kernel-internal things like SIGSTOP
973     * or SIGKILL.
974     */
975    if (info == SEND_SIG_FORCED)
976        goto out_set;
977
978    /*
979     * Real-time signals must be queued if sent by sigqueue, or
980     * some other real-time mechanism. It is implementation
981     * defined whether kill() does so. We attempt to do so, on
982     * the principle of least surprise, but since kill is not
983     * allowed to fail with EAGAIN when low on memory we just
984     * make sure at least one signal gets delivered and don't
985     * pass on the info struct.
986     */
987    if (sig < SIGRTMIN)
988        override_rlimit = (is_si_special(info) || info->si_code >= 0);
989    else
990        override_rlimit = 0;
991
992    q = __sigqueue_alloc(sig, t, GFP_ATOMIC | __GFP_NOTRACK_FALSE_POSITIVE,
993        override_rlimit);
994    if (q) {
995        list_add_tail(&q->list, &pending->list);
996        switch ((unsigned long) info) {
997        case (unsigned long) SEND_SIG_NOINFO:
998            q->info.si_signo = sig;
999            q->info.si_errno = 0;
1000            q->info.si_code = SI_USER;
1001            q->info.si_pid = task_tgid_nr_ns(current,
1002                            task_active_pid_ns(t));
1003            q->info.si_uid = current_uid();
1004            break;
1005        case (unsigned long) SEND_SIG_PRIV:
1006            q->info.si_signo = sig;
1007            q->info.si_errno = 0;
1008            q->info.si_code = SI_KERNEL;
1009            q->info.si_pid = 0;
1010            q->info.si_uid = 0;
1011            break;
1012        default:
1013            copy_siginfo(&q->info, info);
1014            if (from_ancestor_ns)
1015                q->info.si_pid = 0;
1016            break;
1017        }
1018    } else if (!is_si_special(info)) {
1019        if (sig >= SIGRTMIN && info->si_code != SI_USER) {
1020            /*
1021             * Queue overflow, abort. We may abort if the
1022             * signal was rt and sent by user using something
1023             * other than kill().
1024             */
1025            trace_signal_overflow_fail(sig, group, info);
1026            return -EAGAIN;
1027        } else {
1028            /*
1029             * This is a silent loss of information. We still
1030             * send the signal, but the *info bits are lost.
1031             */
1032            trace_signal_lose_info(sig, group, info);
1033        }
1034    }
1035
1036out_set:
1037    signalfd_notify(t, sig);
1038    sigaddset(&pending->signal, sig);
1039    complete_signal(sig, t, group);
1040    return 0;
1041}
1042
1043static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
1044            int group)
1045{
1046    int from_ancestor_ns = 0;
1047
1048#ifdef CONFIG_PID_NS
1049    from_ancestor_ns = si_fromuser(info) &&
1050               !task_pid_nr_ns(current, task_active_pid_ns(t));
1051#endif
1052
1053    return __send_signal(sig, info, t, group, from_ancestor_ns);
1054}
1055
1056static void print_fatal_signal(struct pt_regs *regs, int signr)
1057{
1058    printk("%s/%d: potentially unexpected fatal signal %d.\n",
1059        current->comm, task_pid_nr(current), signr);
1060
1061#if defined(__i386__) && !defined(__arch_um__)
1062    printk("code at %08lx: ", regs->ip);
1063    {
1064        int i;
1065        for (i = 0; i < 16; i++) {
1066            unsigned char insn;
1067
1068            if (get_user(insn, (unsigned char *)(regs->ip + i)))
1069                break;
1070            printk("%02x ", insn);
1071        }
1072    }
1073#endif
1074    printk("\n");
1075    preempt_disable();
1076    show_regs(regs);
1077    preempt_enable();
1078}
1079
1080static int __init setup_print_fatal_signals(char *str)
1081{
1082    get_option (&str, &print_fatal_signals);
1083
1084    return 1;
1085}
1086
1087__setup("print-fatal-signals=", setup_print_fatal_signals);
1088
1089int
1090__group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
1091{
1092    return send_signal(sig, info, p, 1);
1093}
1094
1095static int
1096specific_send_sig_info(int sig, struct siginfo *info, struct task_struct *t)
1097{
1098    return send_signal(sig, info, t, 0);
1099}
1100
1101int do_send_sig_info(int sig, struct siginfo *info, struct task_struct *p,
1102            bool group)
1103{
1104    unsigned long flags;
1105    int ret = -ESRCH;
1106
1107    if (lock_task_sighand(p, &flags)) {
1108        ret = send_signal(sig, info, p, group);
1109        unlock_task_sighand(p, &flags);
1110    }
1111
1112    return ret;
1113}
1114
1115/*
1116 * Force a signal that the process can't ignore: if necessary
1117 * we unblock the signal and change any SIG_IGN to SIG_DFL.
1118 *
1119 * Note: If we unblock the signal, we always reset it to SIG_DFL,
1120 * since we do not want to have a signal handler that was blocked
1121 * be invoked when user space had explicitly blocked it.
1122 *
1123 * We don't want to have recursive SIGSEGV's etc, for example,
1124 * that is why we also clear SIGNAL_UNKILLABLE.
1125 */
1126int
1127force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
1128{
1129    unsigned long int flags;
1130    int ret, blocked, ignored;
1131    struct k_sigaction *action;
1132
1133    spin_lock_irqsave(&t->sighand->siglock, flags);
1134    action = &t->sighand->action[sig-1];
1135    ignored = action->sa.sa_handler == SIG_IGN;
1136    blocked = sigismember(&t->blocked, sig);
1137    if (blocked || ignored) {
1138        action->sa.sa_handler = SIG_DFL;
1139        if (blocked) {
1140            sigdelset(&t->blocked, sig);
1141            recalc_sigpending_and_wake(t);
1142        }
1143    }
1144    if (action->sa.sa_handler == SIG_DFL)
1145        t->signal->flags &= ~SIGNAL_UNKILLABLE;
1146    ret = specific_send_sig_info(sig, info, t);
1147    spin_unlock_irqrestore(&t->sighand->siglock, flags);
1148
1149    return ret;
1150}
1151
1152/*
1153 * Nuke all other threads in the group.
1154 */
1155int zap_other_threads(struct task_struct *p)
1156{
1157    struct task_struct *t = p;
1158    int count = 0;
1159
1160    p->signal->group_stop_count = 0;
1161
1162    while_each_thread(p, t) {
1163        task_clear_group_stop_pending(t);
1164        count++;
1165
1166        /* Don't bother with already dead threads */
1167        if (t->exit_state)
1168            continue;
1169        sigaddset(&t->pending.signal, SIGKILL);
1170        signal_wake_up(t, 1);
1171    }
1172
1173    return count;
1174}
1175
1176struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
1177                       unsigned long *flags)
1178{
1179    struct sighand_struct *sighand;
1180
1181    for (;;) {
1182        local_irq_save(*flags);
1183        rcu_read_lock();
1184        sighand = rcu_dereference(tsk->sighand);
1185        if (unlikely(sighand == NULL)) {
1186            rcu_read_unlock();
1187            local_irq_restore(*flags);
1188            break;
1189        }
1190
1191        spin_lock(&sighand->siglock);
1192        if (likely(sighand == tsk->sighand)) {
1193            rcu_read_unlock();
1194            break;
1195        }
1196        spin_unlock(&sighand->siglock);
1197        rcu_read_unlock();
1198        local_irq_restore(*flags);
1199    }
1200
1201    return sighand;
1202}
1203
1204/*
1205 * send signal info to all the members of a group
1206 */
1207int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
1208{
1209    int ret;
1210
1211    rcu_read_lock();
1212    ret = check_kill_permission(sig, info, p);
1213    rcu_read_unlock();
1214
1215    if (!ret && sig)
1216        ret = do_send_sig_info(sig, info, p, true);
1217
1218    return ret;
1219}
1220
1221/*
1222 * __kill_pgrp_info() sends a signal to a process group: this is what the tty
1223 * control characters do (^C, ^Z etc)
1224 * - the caller must hold at least a readlock on tasklist_lock
1225 */
1226int __kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp)
1227{
1228    struct task_struct *p = NULL;
1229    int retval, success;
1230
1231    success = 0;
1232    retval = -ESRCH;
1233    do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
1234        int err = group_send_sig_info(sig, info, p);
1235        success |= !err;
1236        retval = err;
1237    } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
1238    return success ? 0 : retval;
1239}
1240
1241int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
1242{
1243    int error = -ESRCH;
1244    struct task_struct *p;
1245
1246    rcu_read_lock();
1247retry:
1248    p = pid_task(pid, PIDTYPE_PID);
1249    if (p) {
1250        error = group_send_sig_info(sig, info, p);
1251        if (unlikely(error == -ESRCH))
1252            /*
1253             * The task was unhashed in between, try again.
1254             * If it is dead, pid_task() will return NULL,
1255             * if we race with de_thread() it will find the
1256             * new leader.
1257             */
1258            goto retry;
1259    }
1260    rcu_read_unlock();
1261
1262    return error;
1263}
1264
1265int kill_proc_info(int sig, struct siginfo *info, pid_t pid)
1266{
1267    int error;
1268    rcu_read_lock();
1269    error = kill_pid_info(sig, info, find_vpid(pid));
1270    rcu_read_unlock();
1271    return error;
1272}
1273
1274/* like kill_pid_info(), but doesn't use uid/euid of "current" */
1275int kill_pid_info_as_uid(int sig, struct siginfo *info, struct pid *pid,
1276              uid_t uid, uid_t euid, u32 secid)
1277{
1278    int ret = -EINVAL;
1279    struct task_struct *p;
1280    const struct cred *pcred;
1281    unsigned long flags;
1282
1283    if (!valid_signal(sig))
1284        return ret;
1285
1286    rcu_read_lock();
1287    p = pid_task(pid, PIDTYPE_PID);
1288    if (!p) {
1289        ret = -ESRCH;
1290        goto out_unlock;
1291    }
1292    pcred = __task_cred(p);
1293    if (si_fromuser(info) &&
1294        euid != pcred->suid && euid != pcred->uid &&
1295        uid != pcred->suid && uid != pcred->uid) {
1296        ret = -EPERM;
1297        goto out_unlock;
1298    }
1299    ret = security_task_kill(p, info, sig, secid);
1300    if (ret)
1301        goto out_unlock;
1302
1303    if (sig) {
1304        if (lock_task_sighand(p, &flags)) {
1305            ret = __send_signal(sig, info, p, 1, 0);
1306            unlock_task_sighand(p, &flags);
1307        } else
1308            ret = -ESRCH;
1309    }
1310out_unlock:
1311    rcu_read_unlock();
1312    return ret;
1313}
1314EXPORT_SYMBOL_GPL(kill_pid_info_as_uid);
1315
1316/*
1317 * kill_something_info() interprets pid in interesting ways just like kill(2).
1318 *
1319 * POSIX specifies that kill(-1,sig) is unspecified, but what we have
1320 * is probably wrong. Should make it like BSD or SYSV.
1321 */
1322
1323static int kill_something_info(int sig, struct siginfo *info, pid_t pid)
1324{
1325    int ret;
1326
1327    if (pid > 0) {
1328        rcu_read_lock();
1329        ret = kill_pid_info(sig, info, find_vpid(pid));
1330        rcu_read_unlock();
1331        return ret;
1332    }
1333
1334    read_lock(&tasklist_lock);
1335    if (pid != -1) {
1336        ret = __kill_pgrp_info(sig, info,
1337                pid ? find_vpid(-pid) : task_pgrp(current));
1338    } else {
1339        int retval = 0, count = 0;
1340        struct task_struct * p;
1341
1342        for_each_process(p) {
1343            if (task_pid_vnr(p) > 1 &&
1344                    !same_thread_group(p, current)) {
1345                int err = group_send_sig_info(sig, info, p);
1346                ++count;
1347                if (err != -EPERM)
1348                    retval = err;
1349            }
1350        }
1351        ret = count ? retval : -ESRCH;
1352    }
1353    read_unlock(&tasklist_lock);
1354
1355    return ret;
1356}
1357
1358/*
1359 * These are for backward compatibility with the rest of the kernel source.
1360 */
1361
1362int send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
1363{
1364    /*
1365     * Make sure legacy kernel users don't send in bad values
1366     * (normal paths check this in check_kill_permission).
1367     */
1368    if (!valid_signal(sig))
1369        return -EINVAL;
1370
1371    return do_send_sig_info(sig, info, p, false);
1372}
1373
1374#define __si_special(priv) \
1375    ((priv) ? SEND_SIG_PRIV : SEND_SIG_NOINFO)
1376
1377int
1378send_sig(int sig, struct task_struct *p, int priv)
1379{
1380    return send_sig_info(sig, __si_special(priv), p);
1381}
1382
1383void
1384force_sig(int sig, struct task_struct *p)
1385{
1386    force_sig_info(sig, SEND_SIG_PRIV, p);
1387}
1388
1389/*
1390 * When things go south during signal handling, we
1391 * will force a SIGSEGV. And if the signal that caused
1392 * the problem was already a SIGSEGV, we'll want to
1393 * make sure we don't even try to deliver the signal..
1394 */
1395int
1396force_sigsegv(int sig, struct task_struct *p)
1397{
1398    if (sig == SIGSEGV) {
1399        unsigned long flags;
1400        spin_lock_irqsave(&p->sighand->siglock, flags);
1401        p->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;
1402        spin_unlock_irqrestore(&p->sighand->siglock, flags);
1403    }
1404    force_sig(SIGSEGV, p);
1405    return 0;
1406}
1407
1408int kill_pgrp(struct pid *pid, int sig, int priv)
1409{
1410    int ret;
1411
1412    read_lock(&tasklist_lock);
1413    ret = __kill_pgrp_info(sig, __si_special(priv), pid);
1414    read_unlock(&tasklist_lock);
1415
1416    return ret;
1417}
1418EXPORT_SYMBOL(kill_pgrp);
1419
1420int kill_pid(struct pid *pid, int sig, int priv)
1421{
1422    return kill_pid_info(sig, __si_special(priv), pid);
1423}
1424EXPORT_SYMBOL(kill_pid);
1425
1426/*
1427 * These functions support sending signals using preallocated sigqueue
1428 * structures. This is needed "because realtime applications cannot
1429 * afford to lose notifications of asynchronous events, like timer
1430 * expirations or I/O completions". In the case of POSIX Timers
1431 * we allocate the sigqueue structure from the timer_create. If this
1432 * allocation fails we are able to report the failure to the application
1433 * with an EAGAIN error.
1434 */
1435struct sigqueue *sigqueue_alloc(void)
1436{
1437    struct sigqueue *q = __sigqueue_alloc(-1, current, GFP_KERNEL, 0);
1438
1439    if (q)
1440        q->flags |= SIGQUEUE_PREALLOC;
1441
1442    return q;
1443}
1444
1445void sigqueue_free(struct sigqueue *q)
1446{
1447    unsigned long flags;
1448    spinlock_t *lock = &current->sighand->siglock;
1449
1450    BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
1451    /*
1452     * We must hold ->siglock while testing q->list
1453     * to serialize with collect_signal() or with
1454     * __exit_signal()->flush_sigqueue().
1455     */
1456    spin_lock_irqsave(lock, flags);
1457    q->flags &= ~SIGQUEUE_PREALLOC;
1458    /*
1459     * If it is queued it will be freed when dequeued,
1460     * like the "regular" sigqueue.
1461     */
1462    if (!list_empty(&q->list))
1463        q = NULL;
1464    spin_unlock_irqrestore(lock, flags);
1465
1466    if (q)
1467        __sigqueue_free(q);
1468}
1469
1470int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group)
1471{
1472    int sig = q->info.si_signo;
1473    struct sigpending *pending;
1474    unsigned long flags;
1475    int ret;
1476
1477    BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
1478
1479    ret = -1;
1480    if (!likely(lock_task_sighand(t, &flags)))
1481        goto ret;
1482
1483    ret = 1; /* the signal is ignored */
1484    if (!prepare_signal(sig, t, 0))
1485        goto out;
1486
1487    ret = 0;
1488    if (unlikely(!list_empty(&q->list))) {
1489        /*
1490         * If an SI_TIMER entry is already queue just increment
1491         * the overrun count.
1492         */
1493        BUG_ON(q->info.si_code != SI_TIMER);
1494        q->info.si_overrun++;
1495        goto out;
1496    }
1497    q->info.si_overrun = 0;
1498
1499    signalfd_notify(t, sig);
1500    pending = group ? &t->signal->shared_pending : &t->pending;
1501    list_add_tail(&q->list, &pending->list);
1502    sigaddset(&pending->signal, sig);
1503    complete_signal(sig, t, group);
1504out:
1505    unlock_task_sighand(t, &flags);
1506ret:
1507    return ret;
1508}
1509
1510/*
1511 * Let a parent know about the death of a child.
1512 * For a stopped/continued status change, use do_notify_parent_cldstop instead.
1513 *
1514 * Returns -1 if our parent ignored us and so we've switched to
1515 * self-reaping, or else @sig.
1516 */
1517int do_notify_parent(struct task_struct *tsk, int sig)
1518{
1519    struct siginfo info;
1520    unsigned long flags;
1521    struct sighand_struct *psig;
1522    int ret = sig;
1523
1524    BUG_ON(sig == -1);
1525
1526     /* do_notify_parent_cldstop should have been called instead. */
1527     BUG_ON(task_is_stopped_or_traced(tsk));
1528
1529    BUG_ON(!task_ptrace(tsk) &&
1530           (tsk->group_leader != tsk || !thread_group_empty(tsk)));
1531
1532    info.si_signo = sig;
1533    info.si_errno = 0;
1534    /*
1535     * we are under tasklist_lock here so our parent is tied to
1536     * us and cannot exit and release its namespace.
1537     *
1538     * the only it can is to switch its nsproxy with sys_unshare,
1539     * bu uncharing pid namespaces is not allowed, so we'll always
1540     * see relevant namespace
1541     *
1542     * write_lock() currently calls preempt_disable() which is the
1543     * same as rcu_read_lock(), but according to Oleg, this is not
1544     * correct to rely on this
1545     */
1546    rcu_read_lock();
1547    info.si_pid = task_pid_nr_ns(tsk, tsk->parent->nsproxy->pid_ns);
1548    info.si_uid = __task_cred(tsk)->uid;
1549    rcu_read_unlock();
1550
1551    info.si_utime = cputime_to_clock_t(cputime_add(tsk->utime,
1552                tsk->signal->utime));
1553    info.si_stime = cputime_to_clock_t(cputime_add(tsk->stime,
1554                tsk->signal->stime));
1555
1556    info.si_status = tsk->exit_code & 0x7f;
1557    if (tsk->exit_code & 0x80)
1558        info.si_code = CLD_DUMPED;
1559    else if (tsk->exit_code & 0x7f)
1560        info.si_code = CLD_KILLED;
1561    else {
1562        info.si_code = CLD_EXITED;
1563        info.si_status = tsk->exit_code >> 8;
1564    }
1565
1566    psig = tsk->parent->sighand;
1567    spin_lock_irqsave(&psig->siglock, flags);
1568    if (!task_ptrace(tsk) && sig == SIGCHLD &&
1569        (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
1570         (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) {
1571        /*
1572         * We are exiting and our parent doesn't care. POSIX.1
1573         * defines special semantics for setting SIGCHLD to SIG_IGN
1574         * or setting the SA_NOCLDWAIT flag: we should be reaped
1575         * automatically and not left for our parent's wait4 call.
1576         * Rather than having the parent do it as a magic kind of
1577         * signal handler, we just set this to tell do_exit that we
1578         * can be cleaned up without becoming a zombie. Note that
1579         * we still call __wake_up_parent in this case, because a
1580         * blocked sys_wait4 might now return -ECHILD.
1581         *
1582         * Whether we send SIGCHLD or not for SA_NOCLDWAIT
1583         * is implementation-defined: we do (if you don't want
1584         * it, just use SIG_IGN instead).
1585         */
1586        ret = tsk->exit_signal = -1;
1587        if (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN)
1588            sig = -1;
1589    }
1590    if (valid_signal(sig) && sig > 0)
1591        __group_send_sig_info(sig, &info, tsk->parent);
1592    __wake_up_parent(tsk, tsk->parent);
1593    spin_unlock_irqrestore(&psig->siglock, flags);
1594
1595    return ret;
1596}
1597
1598/**
1599 * do_notify_parent_cldstop - notify parent of stopped/continued state change
1600 * @tsk: task reporting the state change
1601 * @for_ptracer: the notification is for ptracer
1602 * @why: CLD_{CONTINUED|STOPPED|TRAPPED} to report
1603 *
1604 * Notify @tsk's parent that the stopped/continued state has changed. If
1605 * @for_ptracer is %false, @tsk's group leader notifies to its real parent.
1606 * If %true, @tsk reports to @tsk->parent which should be the ptracer.
1607 *
1608 * CONTEXT:
1609 * Must be called with tasklist_lock at least read locked.
1610 */
1611static void do_notify_parent_cldstop(struct task_struct *tsk,
1612                     bool for_ptracer, int why)
1613{
1614    struct siginfo info;
1615    unsigned long flags;
1616    struct task_struct *parent;
1617    struct sighand_struct *sighand;
1618
1619    if (for_ptracer) {
1620        parent = tsk->parent;
1621    } else {
1622        tsk = tsk->group_leader;
1623        parent = tsk->real_parent;
1624    }
1625
1626    info.si_signo = SIGCHLD;
1627    info.si_errno = 0;
1628    /*
1629     * see comment in do_notify_parent() about the following 4 lines
1630     */
1631    rcu_read_lock();
1632    info.si_pid = task_pid_nr_ns(tsk, parent->nsproxy->pid_ns);
1633    info.si_uid = __task_cred(tsk)->uid;
1634    rcu_read_unlock();
1635
1636    info.si_utime = cputime_to_clock_t(tsk->utime);
1637    info.si_stime = cputime_to_clock_t(tsk->stime);
1638
1639     info.si_code = why;
1640     switch (why) {
1641     case CLD_CONTINUED:
1642         info.si_status = SIGCONT;
1643         break;
1644     case CLD_STOPPED:
1645         info.si_status = tsk->signal->group_exit_code & 0x7f;
1646         break;
1647     case CLD_TRAPPED:
1648         info.si_status = tsk->exit_code & 0x7f;
1649         break;
1650     default:
1651         BUG();
1652     }
1653
1654    sighand = parent->sighand;
1655    spin_lock_irqsave(&sighand->siglock, flags);
1656    if (sighand->action[SIGCHLD-1].sa.sa_handler != SIG_IGN &&
1657        !(sighand->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDSTOP))
1658        __group_send_sig_info(SIGCHLD, &info, parent);
1659    /*
1660     * Even if SIGCHLD is not generated, we must wake up wait4 calls.
1661     */
1662    __wake_up_parent(tsk, parent);
1663    spin_unlock_irqrestore(&sighand->siglock, flags);
1664}
1665
1666static inline int may_ptrace_stop(void)
1667{
1668    if (!likely(task_ptrace(current)))
1669        return 0;
1670    /*
1671     * Are we in the middle of do_coredump?
1672     * If so and our tracer is also part of the coredump stopping
1673     * is a deadlock situation, and pointless because our tracer
1674     * is dead so don't allow us to stop.
1675     * If SIGKILL was already sent before the caller unlocked
1676     * ->siglock we must see ->core_state != NULL. Otherwise it
1677     * is safe to enter schedule().
1678     */
1679    if (unlikely(current->mm->core_state) &&
1680        unlikely(current->mm == current->parent->mm))
1681        return 0;
1682
1683    return 1;
1684}
1685
1686/*
1687 * Return non-zero if there is a SIGKILL that should be waking us up.
1688 * Called with the siglock held.
1689 */
1690static int sigkill_pending(struct task_struct *tsk)
1691{
1692    return sigismember(&tsk->pending.signal, SIGKILL) ||
1693        sigismember(&tsk->signal->shared_pending.signal, SIGKILL);
1694}
1695
1696/*
1697 * Test whether the target task of the usual cldstop notification - the
1698 * real_parent of @child - is in the same group as the ptracer.
1699 */
1700static bool real_parent_is_ptracer(struct task_struct *child)
1701{
1702    return same_thread_group(child->parent, child->real_parent);
1703}
1704
1705/*
1706 * This must be called with current->sighand->siglock held.
1707 *
1708 * This should be the path for all ptrace stops.
1709 * We always set current->last_siginfo while stopped here.
1710 * That makes it a way to test a stopped process for
1711 * being ptrace-stopped vs being job-control-stopped.
1712 *
1713 * If we actually decide not to stop at all because the tracer
1714 * is gone, we keep current->exit_code unless clear_code.
1715 */
1716static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
1717    __releases(&current->sighand->siglock)
1718    __acquires(&current->sighand->siglock)
1719{
1720    bool gstop_done = false;
1721
1722    if (arch_ptrace_stop_needed(exit_code, info)) {
1723        /*
1724         * The arch code has something special to do before a
1725         * ptrace stop. This is allowed to block, e.g. for faults
1726         * on user stack pages. We can't keep the siglock while
1727         * calling arch_ptrace_stop, so we must release it now.
1728         * To preserve proper semantics, we must do this before
1729         * any signal bookkeeping like checking group_stop_count.
1730         * Meanwhile, a SIGKILL could come in before we retake the
1731         * siglock. That must prevent us from sleeping in TASK_TRACED.
1732         * So after regaining the lock, we must check for SIGKILL.
1733         */
1734        spin_unlock_irq(&current->sighand->siglock);
1735        arch_ptrace_stop(exit_code, info);
1736        spin_lock_irq(&current->sighand->siglock);
1737        if (sigkill_pending(current))
1738            return;
1739    }
1740
1741    /*
1742     * If @why is CLD_STOPPED, we're trapping to participate in a group
1743     * stop. Do the bookkeeping. Note that if SIGCONT was delievered
1744     * while siglock was released for the arch hook, PENDING could be
1745     * clear now. We act as if SIGCONT is received after TASK_TRACED
1746     * is entered - ignore it.
1747     */
1748    if (why == CLD_STOPPED && (current->group_stop & GROUP_STOP_PENDING))
1749        gstop_done = task_participate_group_stop(current);
1750
1751    current->last_siginfo = info;
1752    current->exit_code = exit_code;
1753
1754    /*
1755     * TRACED should be visible before TRAPPING is cleared; otherwise,
1756     * the tracer might fail do_wait().
1757     */
1758    set_current_state(TASK_TRACED);
1759
1760    /*
1761     * We're committing to trapping. Clearing GROUP_STOP_TRAPPING and
1762     * transition to TASK_TRACED should be atomic with respect to
1763     * siglock. This hsould be done after the arch hook as siglock is
1764     * released and regrabbed across it.
1765     */
1766    task_clear_group_stop_trapping(current);
1767
1768    spin_unlock_irq(&current->sighand->siglock);
1769    read_lock(&tasklist_lock);
1770    if (may_ptrace_stop()) {
1771        /*
1772         * Notify parents of the stop.
1773         *
1774         * While ptraced, there are two parents - the ptracer and
1775         * the real_parent of the group_leader. The ptracer should
1776         * know about every stop while the real parent is only
1777         * interested in the completion of group stop. The states
1778         * for the two don't interact with each other. Notify
1779         * separately unless they're gonna be duplicates.
1780         */
1781        do_notify_parent_cldstop(current, true, why);
1782        if (gstop_done && !real_parent_is_ptracer(current))
1783            do_notify_parent_cldstop(current, false, why);
1784
1785        /*
1786         * Don't want to allow preemption here, because
1787         * sys_ptrace() needs this task to be inactive.
1788         *
1789         * XXX: implement read_unlock_no_resched().
1790         */
1791        preempt_disable();
1792        read_unlock(&tasklist_lock);
1793        preempt_enable_no_resched();
1794        schedule();
1795    } else {
1796        /*
1797         * By the time we got the lock, our tracer went away.
1798         * Don't drop the lock yet, another tracer may come.
1799         *
1800         * If @gstop_done, the ptracer went away between group stop
1801         * completion and here. During detach, it would have set
1802         * GROUP_STOP_PENDING on us and we'll re-enter TASK_STOPPED
1803         * in do_signal_stop() on return, so notifying the real
1804         * parent of the group stop completion is enough.
1805         */
1806        if (gstop_done)
1807            do_notify_parent_cldstop(current, false, why);
1808
1809        __set_current_state(TASK_RUNNING);
1810        if (clear_code)
1811            current->exit_code = 0;
1812        read_unlock(&tasklist_lock);
1813    }
1814
1815    /*
1816     * While in TASK_TRACED, we were considered "frozen enough".
1817     * Now that we woke up, it's crucial if we're supposed to be
1818     * frozen that we freeze now before running anything substantial.
1819     */
1820    try_to_freeze();
1821
1822    /*
1823     * We are back. Now reacquire the siglock before touching
1824     * last_siginfo, so that we are sure to have synchronized with
1825     * any signal-sending on another CPU that wants to examine it.
1826     */
1827    spin_lock_irq(&current->sighand->siglock);
1828    current->last_siginfo = NULL;
1829
1830    /*
1831     * Queued signals ignored us while we were stopped for tracing.
1832     * So check for any that we should take before resuming user mode.
1833     * This sets TIF_SIGPENDING, but never clears it.
1834     */
1835    recalc_sigpending_tsk(current);
1836}
1837
1838void ptrace_notify(int exit_code)
1839{
1840    siginfo_t info;
1841
1842    BUG_ON((exit_code & (0x7f | ~0xffff)) != SIGTRAP);
1843
1844    memset(&info, 0, sizeof info);
1845    info.si_signo = SIGTRAP;
1846    info.si_code = exit_code;
1847    info.si_pid = task_pid_vnr(current);
1848    info.si_uid = current_uid();
1849
1850    /* Let the debugger run. */
1851    spin_lock_irq(&current->sighand->siglock);
1852    ptrace_stop(exit_code, CLD_TRAPPED, 1, &info);
1853    spin_unlock_irq(&current->sighand->siglock);
1854}
1855
1856/*
1857 * This performs the stopping for SIGSTOP and other stop signals.
1858 * We have to stop all threads in the thread group.
1859 * Returns non-zero if we've actually stopped and released the siglock.
1860 * Returns zero if we didn't stop and still hold the siglock.
1861 */
1862static int do_signal_stop(int signr)
1863{
1864    struct signal_struct *sig = current->signal;
1865
1866    if (!(current->group_stop & GROUP_STOP_PENDING)) {
1867        unsigned int gstop = GROUP_STOP_PENDING | GROUP_STOP_CONSUME;
1868        struct task_struct *t;
1869
1870        /* signr will be recorded in task->group_stop for retries */
1871        WARN_ON_ONCE(signr & ~GROUP_STOP_SIGMASK);
1872
1873        if (!likely(current->group_stop & GROUP_STOP_DEQUEUED) ||
1874            unlikely(signal_group_exit(sig)))
1875            return 0;
1876        /*
1877         * There is no group stop already in progress. We must
1878         * initiate one now.
1879         *
1880         * While ptraced, a task may be resumed while group stop is
1881         * still in effect and then receive a stop signal and
1882         * initiate another group stop. This deviates from the
1883         * usual behavior as two consecutive stop signals can't
1884         * cause two group stops when !ptraced. That is why we
1885         * also check !task_is_stopped(t) below.
1886         *
1887         * The condition can be distinguished by testing whether
1888         * SIGNAL_STOP_STOPPED is already set. Don't generate
1889         * group_exit_code in such case.
1890         *
1891         * This is not necessary for SIGNAL_STOP_CONTINUED because
1892         * an intervening stop signal is required to cause two
1893         * continued events regardless of ptrace.
1894         */
1895        if (!(sig->flags & SIGNAL_STOP_STOPPED))
1896            sig->group_exit_code = signr;
1897        else
1898            WARN_ON_ONCE(!task_ptrace(current));
1899
1900        current->group_stop &= ~GROUP_STOP_SIGMASK;
1901        current->group_stop |= signr | gstop;
1902        sig->group_stop_count = 1;
1903        for (t = next_thread(current); t != current;
1904             t = next_thread(t)) {
1905            t->group_stop &= ~GROUP_STOP_SIGMASK;
1906            /*
1907             * Setting state to TASK_STOPPED for a group
1908             * stop is always done with the siglock held,
1909             * so this check has no races.
1910             */
1911            if (!(t->flags & PF_EXITING) && !task_is_stopped(t)) {
1912                t->group_stop |= signr | gstop;
1913                sig->group_stop_count++;
1914                signal_wake_up(t, 0);
1915            }
1916        }
1917    }
1918retry:
1919    if (likely(!task_ptrace(current))) {
1920        int notify = 0;
1921
1922        /*
1923         * If there are no other threads in the group, or if there
1924         * is a group stop in progress and we are the last to stop,
1925         * report to the parent.
1926         */
1927        if (task_participate_group_stop(current))
1928            notify = CLD_STOPPED;
1929
1930        __set_current_state(TASK_STOPPED);
1931        spin_unlock_irq(&current->sighand->siglock);
1932
1933        /*
1934         * Notify the parent of the group stop completion. Because
1935         * we're not holding either the siglock or tasklist_lock
1936         * here, ptracer may attach inbetween; however, this is for
1937         * group stop and should always be delivered to the real
1938         * parent of the group leader. The new ptracer will get
1939         * its notification when this task transitions into
1940         * TASK_TRACED.
1941         */
1942        if (notify) {
1943            read_lock(&tasklist_lock);
1944            do_notify_parent_cldstop(current, false, notify);
1945            read_unlock(&tasklist_lock);
1946        }
1947
1948        /* Now we don't run again until woken by SIGCONT or SIGKILL */
1949        schedule();
1950
1951        spin_lock_irq(&current->sighand->siglock);
1952    } else {
1953        ptrace_stop(current->group_stop & GROUP_STOP_SIGMASK,
1954                CLD_STOPPED, 0, NULL);
1955        current->exit_code = 0;
1956    }
1957
1958    /*
1959     * GROUP_STOP_PENDING could be set if another group stop has
1960     * started since being woken up or ptrace wants us to transit
1961     * between TASK_STOPPED and TRACED. Retry group stop.
1962     */
1963    if (current->group_stop & GROUP_STOP_PENDING) {
1964        WARN_ON_ONCE(!(current->group_stop & GROUP_STOP_SIGMASK));
1965        goto retry;
1966    }
1967
1968    /* PTRACE_ATTACH might have raced with task killing, clear trapping */
1969    task_clear_group_stop_trapping(current);
1970
1971    spin_unlock_irq(&current->sighand->siglock);
1972
1973    tracehook_finish_jctl();
1974
1975    return 1;
1976}
1977
1978static int ptrace_signal(int signr, siginfo_t *info,
1979             struct pt_regs *regs, void *cookie)
1980{
1981    if (!task_ptrace(current))
1982        return signr;
1983
1984    ptrace_signal_deliver(regs, cookie);
1985
1986    /* Let the debugger run. */
1987    ptrace_stop(signr, CLD_TRAPPED, 0, info);
1988
1989    /* We're back. Did the debugger cancel the sig? */
1990    signr = current->exit_code;
1991    if (signr == 0)
1992        return signr;
1993
1994    current->exit_code = 0;
1995
1996    /*
1997     * Update the siginfo structure if the signal has
1998     * changed. If the debugger wanted something
1999     * specific in the siginfo structure then it should
2000     * have updated *info via PTRACE_SETSIGINFO.
2001     */
2002    if (signr != info->si_signo) {
2003        info->si_signo = signr;
2004        info->si_errno = 0;
2005        info->si_code = SI_USER;
2006        info->si_pid = task_pid_vnr(current->parent);
2007        info->si_uid = task_uid(current->parent);
2008    }
2009
2010    /* If the (new) signal is now blocked, requeue it. */
2011    if (sigismember(&current->blocked, signr)) {
2012        specific_send_sig_info(signr, info, current);
2013        signr = 0;
2014    }
2015
2016    return signr;
2017}
2018
2019int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka,
2020              struct pt_regs *regs, void *cookie)
2021{
2022    struct sighand_struct *sighand = current->sighand;
2023    struct signal_struct *signal = current->signal;
2024    int signr;
2025
2026relock:
2027    /*
2028     * We'll jump back here after any time we were stopped in TASK_STOPPED.
2029     * While in TASK_STOPPED, we were considered "frozen enough".
2030     * Now that we woke up, it's crucial if we're supposed to be
2031     * frozen that we freeze now before running anything substantial.
2032     */
2033    try_to_freeze();
2034
2035    spin_lock_irq(&sighand->siglock);
2036    /*
2037     * Every stopped thread goes here after wakeup. Check to see if
2038     * we should notify the parent, prepare_signal(SIGCONT) encodes
2039     * the CLD_ si_code into SIGNAL_CLD_MASK bits.
2040     */
2041    if (unlikely(signal->flags & SIGNAL_CLD_MASK)) {
2042        struct task_struct *leader;
2043        int why;
2044
2045        if (signal->flags & SIGNAL_CLD_CONTINUED)
2046            why = CLD_CONTINUED;
2047        else
2048            why = CLD_STOPPED;
2049
2050        signal->flags &= ~SIGNAL_CLD_MASK;
2051
2052        spin_unlock_irq(&sighand->siglock);
2053
2054        /*
2055         * Notify the parent that we're continuing. This event is
2056         * always per-process and doesn't make whole lot of sense
2057         * for ptracers, who shouldn't consume the state via
2058         * wait(2) either, but, for backward compatibility, notify
2059         * the ptracer of the group leader too unless it's gonna be
2060         * a duplicate.
2061         */
2062        read_lock(&tasklist_lock);
2063
2064        do_notify_parent_cldstop(current, false, why);
2065
2066        leader = current->group_leader;
2067        if (task_ptrace(leader) && !real_parent_is_ptracer(leader))
2068            do_notify_parent_cldstop(leader, true, why);
2069
2070        read_unlock(&tasklist_lock);
2071
2072        goto relock;
2073    }
2074
2075    for (;;) {
2076        struct k_sigaction *ka;
2077        /*
2078         * Tracing can induce an artificial signal and choose sigaction.
2079         * The return value in @signr determines the default action,
2080         * but @info->si_signo is the signal number we will report.
2081         */
2082        signr = tracehook_get_signal(current, regs, info, return_ka);
2083        if (unlikely(signr < 0))
2084            goto relock;
2085        if (unlikely(signr != 0))
2086            ka = return_ka;
2087        else {
2088            if (unlikely(current->group_stop &
2089                     GROUP_STOP_PENDING) && do_signal_stop(0))
2090                goto relock;
2091
2092            signr = dequeue_signal(current, &current->blocked,
2093                           info);
2094
2095            if (!signr)
2096                break; /* will return 0 */
2097
2098            if (signr != SIGKILL) {
2099                signr = ptrace_signal(signr, info,
2100                              regs, cookie);
2101                if (!signr)
2102                    continue;
2103            }
2104
2105            ka = &sighand->action[signr-1];
2106        }
2107
2108        /* Trace actually delivered signals. */
2109        trace_signal_deliver(signr, info, ka);
2110
2111        if (ka->sa.sa_handler == SIG_IGN) /* Do nothing. */
2112            continue;
2113        if (ka->sa.sa_handler != SIG_DFL) {
2114            /* Run the handler. */
2115            *return_ka = *ka;
2116
2117            if (ka->sa.sa_flags & SA_ONESHOT)
2118                ka->sa.sa_handler = SIG_DFL;
2119
2120            break; /* will return non-zero "signr" value */
2121        }
2122
2123        /*
2124         * Now we are doing the default action for this signal.
2125         */
2126        if (sig_kernel_ignore(signr)) /* Default is nothing. */
2127            continue;
2128
2129        /*
2130         * Global init gets no signals it doesn't want.
2131         * Container-init gets no signals it doesn't want from same
2132         * container.
2133         *
2134         * Note that if global/container-init sees a sig_kernel_only()
2135         * signal here, the signal must have been generated internally
2136         * or must have come from an ancestor namespace. In either
2137         * case, the signal cannot be dropped.
2138         */
2139        if (unlikely(signal->flags & SIGNAL_UNKILLABLE) &&
2140                !sig_kernel_only(signr))
2141            continue;
2142
2143        if (sig_kernel_stop(signr)) {
2144            /*
2145             * The default action is to stop all threads in
2146             * the thread group. The job control signals
2147             * do nothing in an orphaned pgrp, but SIGSTOP
2148             * always works. Note that siglock needs to be
2149             * dropped during the call to is_orphaned_pgrp()
2150             * because of lock ordering with tasklist_lock.
2151             * This allows an intervening SIGCONT to be posted.
2152             * We need to check for that and bail out if necessary.
2153             */
2154            if (signr != SIGSTOP) {
2155                spin_unlock_irq(&sighand->siglock);
2156
2157                /* signals can be posted during this window */
2158
2159                if (is_current_pgrp_orphaned())
2160                    goto relock;
2161
2162                spin_lock_irq(&sighand->siglock);
2163            }
2164
2165            if (likely(do_signal_stop(info->si_signo))) {
2166                /* It released the siglock. */
2167                goto relock;
2168            }
2169
2170            /*
2171             * We didn't actually stop, due to a race
2172             * with SIGCONT or something like that.
2173             */
2174            continue;
2175        }
2176
2177        spin_unlock_irq(&sighand->siglock);
2178
2179        /*
2180         * Anything else is fatal, maybe with a core dump.
2181         */
2182        current->flags |= PF_SIGNALED;
2183
2184        if (sig_kernel_coredump(signr)) {
2185            if (print_fatal_signals)
2186                print_fatal_signal(regs, info->si_signo);
2187            /*
2188             * If it was able to dump core, this kills all
2189             * other threads in the group and synchronizes with
2190             * their demise. If we lost the race with another
2191             * thread getting here, it set group_exit_code
2192             * first and our do_group_exit call below will use
2193             * that value and ignore the one we pass it.
2194             */
2195            do_coredump(info->si_signo, info->si_signo, regs);
2196        }
2197
2198        /*
2199         * Death signals, no core dump.
2200         */
2201        do_group_exit(info->si_signo);
2202        /* NOTREACHED */
2203    }
2204    spin_unlock_irq(&sighand->siglock);
2205    return signr;
2206}
2207
2208/*
2209 * It could be that complete_signal() picked us to notify about the
2210 * group-wide signal. Other threads should be notified now to take
2211 * the shared signals in @which since we will not.
2212 */
2213static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which)
2214{
2215    sigset_t retarget;
2216    struct task_struct *t;
2217
2218    sigandsets(&retarget, &tsk->signal->shared_pending.signal, which);
2219    if (sigisemptyset(&retarget))
2220        return;
2221
2222    t = tsk;
2223    while_each_thread(tsk, t) {
2224        if (t->flags & PF_EXITING)
2225            continue;
2226
2227        if (!has_pending_signals(&retarget, &t->blocked))
2228            continue;
2229        /* Remove the signals this thread can handle. */
2230        sigandsets(&retarget, &retarget, &t->blocked);
2231
2232        if (!signal_pending(t))
2233            signal_wake_up(t, 0);
2234
2235        if (sigisemptyset(&retarget))
2236            break;
2237    }
2238}
2239
2240void exit_signals(struct task_struct *tsk)
2241{
2242    int group_stop = 0;
2243    sigset_t unblocked;
2244
2245    if (thread_group_empty(tsk) || signal_group_exit(tsk->signal)) {
2246        tsk->flags |= PF_EXITING;
2247        return;
2248    }
2249
2250    spin_lock_irq(&tsk->sighand->siglock);
2251    /*
2252     * From now this task is not visible for group-wide signals,
2253     * see wants_signal(), do_signal_stop().
2254     */
2255    tsk->flags |= PF_EXITING;
2256    if (!signal_pending(tsk))
2257        goto out;
2258
2259    unblocked = tsk->blocked;
2260    signotset(&unblocked);
2261    retarget_shared_pending(tsk, &unblocked);
2262
2263    if (unlikely(tsk->group_stop & GROUP_STOP_PENDING) &&
2264        task_participate_group_stop(tsk))
2265        group_stop = CLD_STOPPED;
2266out:
2267    spin_unlock_irq(&tsk->sighand->siglock);
2268
2269    /*
2270     * If group stop has completed, deliver the notification. This
2271     * should always go to the real parent of the group leader.
2272     */
2273    if (unlikely(group_stop)) {
2274        read_lock(&tasklist_lock);
2275        do_notify_parent_cldstop(tsk, false, group_stop);
2276        read_unlock(&tasklist_lock);
2277    }
2278}
2279
2280EXPORT_SYMBOL(recalc_sigpending);
2281EXPORT_SYMBOL_GPL(dequeue_signal);
2282EXPORT_SYMBOL(flush_signals);
2283EXPORT_SYMBOL(force_sig);
2284EXPORT_SYMBOL(send_sig);
2285EXPORT_SYMBOL(send_sig_info);
2286EXPORT_SYMBOL(sigprocmask);
2287EXPORT_SYMBOL(block_all_signals);
2288EXPORT_SYMBOL(unblock_all_signals);
2289
2290
2291/*
2292 * System call entry points.
2293 */
2294
2295/**
2296 * sys_restart_syscall - restart a system call
2297 */
2298SYSCALL_DEFINE0(restart_syscall)
2299{
2300    struct restart_block *restart = &current_thread_info()->restart_block;
2301    return restart->fn(restart);
2302}
2303
2304long do_no_restart_syscall(struct restart_block *param)
2305{
2306    return -EINTR;
2307}
2308
2309static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset)
2310{
2311    if (signal_pending(tsk) && !thread_group_empty(tsk)) {
2312        sigset_t newblocked;
2313        /* A set of now blocked but previously unblocked signals. */
2314        sigandnsets(&newblocked, newset, &current->blocked);
2315        retarget_shared_pending(tsk, &newblocked);
2316    }
2317    tsk->blocked = *newset;
2318    recalc_sigpending();
2319}
2320
2321/**
2322 * set_current_blocked - change current->blocked mask
2323 * @newset: new mask
2324 *
2325 * It is wrong to change ->blocked directly, this helper should be used
2326 * to ensure the process can't miss a shared signal we are going to block.
2327 */
2328void set_current_blocked(const sigset_t *newset)
2329{
2330    struct task_struct *tsk = current;
2331
2332    spin_lock_irq(&tsk->sighand->siglock);
2333    __set_task_blocked(tsk, newset);
2334    spin_unlock_irq(&tsk->sighand->siglock);
2335}
2336
2337/*
2338 * This is also useful for kernel threads that want to temporarily
2339 * (or permanently) block certain signals.
2340 *
2341 * NOTE! Unlike the user-mode sys_sigprocmask(), the kernel
2342 * interface happily blocks "unblockable" signals like SIGKILL
2343 * and friends.
2344 */
2345int sigprocmask(int how, sigset_t *set, sigset_t *oldset)
2346{
2347    struct task_struct *tsk = current;
2348    sigset_t newset;
2349
2350    /* Lockless, only current can change ->blocked, never from irq */
2351    if (oldset)
2352        *oldset = tsk->blocked;
2353
2354    switch (how) {
2355    case SIG_BLOCK:
2356        sigorsets(&newset, &tsk->blocked, set);
2357        break;
2358    case SIG_UNBLOCK:
2359        sigandnsets(&newset, &tsk->blocked, set);
2360        break;
2361    case SIG_SETMASK:
2362        newset = *set;
2363        break;
2364    default:
2365        return -EINVAL;
2366    }
2367
2368    set_current_blocked(&newset);
2369    return 0;
2370}
2371
2372/**
2373 * sys_rt_sigprocmask - change the list of currently blocked signals
2374 * @how: whether to add, remove, or set signals
2375 * @nset: stores pending signals
2376 * @oset: previous value of signal mask if non-null
2377 * @sigsetsize: size of sigset_t type
2378 */
2379SYSCALL_DEFINE4(rt_sigprocmask, int, how, sigset_t __user *, nset,
2380        sigset_t __user *, oset, size_t, sigsetsize)
2381{
2382    sigset_t old_set, new_set;
2383    int error;
2384
2385    /* XXX: Don't preclude handling different sized sigset_t's. */
2386    if (sigsetsize != sizeof(sigset_t))
2387        return -EINVAL;
2388
2389    old_set = current->blocked;
2390
2391    if (nset) {
2392        if (copy_from_user(&new_set, nset, sizeof(sigset_t)))
2393            return -EFAULT;
2394        sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
2395
2396        error = sigprocmask(how, &new_set, NULL);
2397        if (error)
2398            return error;
2399    }
2400
2401    if (oset) {
2402        if (copy_to_user(oset, &old_set, sizeof(sigset_t)))
2403            return -EFAULT;
2404    }
2405
2406    return 0;
2407}
2408
2409long do_sigpending(void __user *set, unsigned long sigsetsize)
2410{
2411    long error = -EINVAL;
2412    sigset_t pending;
2413
2414    if (sigsetsize > sizeof(sigset_t))
2415        goto out;
2416
2417    spin_lock_irq(&current->sighand->siglock);
2418    sigorsets(&pending, &current->pending.signal,
2419          &current->signal->shared_pending.signal);
2420    spin_unlock_irq(&current->sighand->siglock);
2421
2422    /* Outside the lock because only this thread touches it. */
2423    sigandsets(&pending, &current->blocked, &pending);
2424
2425    error = -EFAULT;
2426    if (!copy_to_user(set, &pending, sigsetsize))
2427        error = 0;
2428
2429out:
2430    return error;
2431}
2432
2433/**
2434 * sys_rt_sigpending - examine a pending signal that has been raised
2435 * while blocked
2436 * @set: stores pending signals
2437 * @sigsetsize: size of sigset_t type or larger
2438 */
2439SYSCALL_DEFINE2(rt_sigpending, sigset_t __user *, set, size_t, sigsetsize)
2440{
2441    return do_sigpending(set, sigsetsize);
2442}
2443
2444#ifndef HAVE_ARCH_COPY_SIGINFO_TO_USER
2445
2446int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from)
2447{
2448    int err;
2449
2450    if (!access_ok (VERIFY_WRITE, to, sizeof(siginfo_t)))
2451        return -EFAULT;
2452    if (from->si_code < 0)
2453        return __copy_to_user(to, from, sizeof(siginfo_t))
2454            ? -EFAULT : 0;
2455    /*
2456     * If you change siginfo_t structure, please be sure
2457     * this code is fixed accordingly.
2458     * Please remember to update the signalfd_copyinfo() function
2459     * inside fs/signalfd.c too, in case siginfo_t changes.
2460     * It should never copy any pad contained in the structure
2461     * to avoid security leaks, but must copy the generic
2462     * 3 ints plus the relevant union member.
2463     */
2464    err = __put_user(from->si_signo, &to->si_signo);
2465    err |= __put_user(from->si_errno, &to->si_errno);
2466    err |= __put_user((short)from->si_code, &to->si_code);
2467    switch (from->si_code & __SI_MASK) {
2468    case __SI_KILL:
2469        err |= __put_user(from->si_pid, &to->si_pid);
2470        err |= __put_user(from->si_uid, &to->si_uid);
2471        break;
2472    case __SI_TIMER:
2473         err |= __put_user(from->si_tid, &to->si_tid);
2474         err |= __put_user(from->si_overrun, &to->si_overrun);
2475         err |= __put_user(from->si_ptr, &to->si_ptr);
2476        break;
2477    case __SI_POLL:
2478        err |= __put_user(from->si_band, &to->si_band);
2479        err |= __put_user(from->si_fd, &to->si_fd);
2480        break;
2481    case __SI_FAULT:
2482        err |= __put_user(from->si_addr, &to->si_addr);
2483#ifdef __ARCH_SI_TRAPNO
2484        err |= __put_user(from->si_trapno, &to->si_trapno);
2485#endif
2486#ifdef BUS_MCEERR_AO
2487        /*
2488         * Other callers might not initialize the si_lsb field,
2489         * so check explicitly for the right codes here.
2490         */
2491        if (from->si_code == BUS_MCEERR_AR || from->si_code == BUS_MCEERR_AO)
2492            err |= __put_user(from->si_addr_lsb, &to->si_addr_lsb);
2493#endif
2494        break;
2495    case __SI_CHLD:
2496        err |= __put_user(from->si_pid, &to->si_pid);
2497        err |= __put_user(from->si_uid, &to->si_uid);
2498        err |= __put_user(from->si_status, &to->si_status);
2499        err |= __put_user(from->si_utime, &to->si_utime);
2500        err |= __put_user(from->si_stime, &to->si_stime);
2501        break;
2502    case __SI_RT: /* This is not generated by the kernel as of now. */
2503    case __SI_MESGQ: /* But this is */
2504        err |= __put_user(from->si_pid, &to->si_pid);
2505        err |= __put_user(from->si_uid, &to->si_uid);
2506        err |= __put_user(from->si_ptr, &to->si_ptr);
2507        break;
2508    default: /* this is just in case for now ... */
2509        err |= __put_user(from->si_pid, &to->si_pid);
2510        err |= __put_user(from->si_uid, &to->si_uid);
2511        break;
2512    }
2513    return err;
2514}
2515
2516#endif
2517
2518/**
2519 * do_sigtimedwait - wait for queued signals specified in @which
2520 * @which: queued signals to wait for
2521 * @info: if non-null, the signal's siginfo is returned here
2522 * @ts: upper bound on process time suspension
2523 */
2524int do_sigtimedwait(const sigset_t *which, siginfo_t *info,
2525            const struct timespec *ts)
2526{
2527    struct task_struct *tsk = current;
2528    long timeout = MAX_SCHEDULE_TIMEOUT;
2529    sigset_t mask = *which;
2530    int sig;
2531
2532    if (ts) {
2533        if (!timespec_valid(ts))
2534            return -EINVAL;
2535        timeout = timespec_to_jiffies(ts);
2536        /*
2537         * We can be close to the next tick, add another one
2538         * to ensure we will wait at least the time asked for.
2539         */
2540        if (ts->tv_sec || ts->tv_nsec)
2541            timeout++;
2542    }
2543
2544    /*
2545     * Invert the set of allowed signals to get those we want to block.
2546     */
2547    sigdelsetmask(&mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
2548    signotset(&mask);
2549
2550    spin_lock_irq(&tsk->sighand->siglock);
2551    sig = dequeue_signal(tsk, &mask, info);
2552    if (!sig && timeout) {
2553        /*
2554         * None ready, temporarily unblock those we're interested
2555         * while we are sleeping in so that we'll be awakened when
2556         * they arrive. Unblocking is always fine, we can avoid
2557         * set_current_blocked().
2558         */
2559        tsk->real_blocked = tsk->blocked;
2560        sigandsets(&tsk->blocked, &tsk->blocked, &mask);
2561        recalc_sigpending();
2562        spin_unlock_irq(&tsk->sighand->siglock);
2563
2564        timeout = schedule_timeout_interruptible(timeout);
2565
2566        spin_lock_irq(&tsk->sighand->siglock);
2567        __set_task_blocked(tsk, &tsk->real_blocked);
2568        siginitset(&tsk->real_blocked, 0);
2569        sig = dequeue_signal(tsk, &mask, info);
2570    }
2571    spin_unlock_irq(&tsk->sighand->siglock);
2572
2573    if (sig)
2574        return sig;
2575    return timeout ? -EINTR : -EAGAIN;
2576}
2577
2578/**
2579 * sys_rt_sigtimedwait - synchronously wait for queued signals specified
2580 * in @uthese
2581 * @uthese: queued signals to wait for
2582 * @uinfo: if non-null, the signal's siginfo is returned here
2583 * @uts: upper bound on process time suspension
2584 * @sigsetsize: size of sigset_t type
2585 */
2586SYSCALL_DEFINE4(rt_sigtimedwait, const sigset_t __user *, uthese,
2587        siginfo_t __user *, uinfo, const struct timespec __user *, uts,
2588        size_t, sigsetsize)
2589{
2590    sigset_t these;
2591    struct timespec ts;
2592    siginfo_t info;
2593    int ret;
2594
2595    /* XXX: Don't preclude handling different sized sigset_t's. */
2596    if (sigsetsize != sizeof(sigset_t))
2597        return -EINVAL;
2598
2599    if (copy_from_user(&these, uthese, sizeof(these)))
2600        return -EFAULT;
2601
2602    if (uts) {
2603        if (copy_from_user(&ts, uts, sizeof(ts)))
2604            return -EFAULT;
2605    }
2606
2607    ret = do_sigtimedwait(&these, &info, uts ? &ts : NULL);
2608
2609    if (ret > 0 && uinfo) {
2610        if (copy_siginfo_to_user(uinfo, &info))
2611            ret = -EFAULT;
2612    }
2613
2614    return ret;
2615}
2616
2617/**
2618 * sys_kill - send a signal to a process
2619 * @pid: the PID of the process
2620 * @sig: signal to be sent
2621 */
2622SYSCALL_DEFINE2(kill, pid_t, pid, int, sig)
2623{
2624    struct siginfo info;
2625
2626    info.si_signo = sig;
2627    info.si_errno = 0;
2628    info.si_code = SI_USER;
2629    info.si_pid = task_tgid_vnr(current);
2630    info.si_uid = current_uid();
2631
2632    return kill_something_info(sig, &info, pid);
2633}
2634
2635static int
2636do_send_specific(pid_t tgid, pid_t pid, int sig, struct siginfo *info)
2637{
2638    struct task_struct *p;
2639    int error = -ESRCH;
2640
2641    rcu_read_lock();
2642    p = find_task_by_vpid(pid);
2643    if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) {
2644        error = check_kill_permission(sig, info, p);
2645        /*
2646         * The null signal is a permissions and process existence
2647         * probe. No signal is actually delivered.
2648         */
2649        if (!error && sig) {
2650            error = do_send_sig_info(sig, info, p, false);
2651            /*
2652             * If lock_task_sighand() failed we pretend the task
2653             * dies after receiving the signal. The window is tiny,
2654             * and the signal is private anyway.
2655             */
2656            if (unlikely(error == -ESRCH))
2657                error = 0;
2658        }
2659    }
2660    rcu_read_unlock();
2661
2662    return error;
2663}
2664
2665static int do_tkill(pid_t tgid, pid_t pid, int sig)
2666{
2667    struct siginfo info;
2668
2669    info.si_signo = sig;
2670    info.si_errno = 0;
2671    info.si_code = SI_TKILL;
2672    info.si_pid = task_tgid_vnr(current);
2673    info.si_uid = current_uid();
2674
2675    return do_send_specific(tgid, pid, sig, &info);
2676}
2677
2678/**
2679 * sys_tgkill - send signal to one specific thread
2680 * @tgid: the thread group ID of the thread
2681 * @pid: the PID of the thread
2682 * @sig: signal to be sent
2683 *
2684 * This syscall also checks the @tgid and returns -ESRCH even if the PID
2685 * exists but it's not belonging to the target process anymore. This
2686 * method solves the problem of threads exiting and PIDs getting reused.
2687 */
2688SYSCALL_DEFINE3(tgkill, pid_t, tgid, pid_t, pid, int, sig)
2689{
2690    /* This is only valid for single tasks */
2691    if (pid <= 0 || tgid <= 0)
2692        return -EINVAL;
2693
2694    return do_tkill(tgid, pid, sig);
2695}
2696
2697/**
2698 * sys_tkill - send signal to one specific task
2699 * @pid: the PID of the task
2700 * @sig: signal to be sent
2701 *
2702 * Send a signal to only one task, even if it's a CLONE_THREAD task.
2703 */
2704SYSCALL_DEFINE2(tkill, pid_t, pid, int, sig)
2705{
2706    /* This is only valid for single tasks */
2707    if (pid <= 0)
2708        return -EINVAL;
2709
2710    return do_tkill(0, pid, sig);
2711}
2712
2713/**
2714 * sys_rt_sigqueueinfo - send signal information to a signal
2715 * @pid: the PID of the thread
2716 * @sig: signal to be sent
2717 * @uinfo: signal info to be sent
2718 */
2719SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
2720        siginfo_t __user *, uinfo)
2721{
2722    siginfo_t info;
2723
2724    if (copy_from_user(&info, uinfo, sizeof(siginfo_t)))
2725        return -EFAULT;
2726
2727    /* Not even root can pretend to send signals from the kernel.
2728     * Nor can they impersonate a kill()/tgkill(), which adds source info.
2729     */
2730    if (info.si_code >= 0 || info.si_code == SI_TKILL) {
2731        /* We used to allow any < 0 si_code */
2732        WARN_ON_ONCE(info.si_code < 0);
2733        return -EPERM;
2734    }
2735    info.si_signo = sig;
2736
2737    /* POSIX.1b doesn't mention process groups. */
2738    return kill_proc_info(sig, &info, pid);
2739}
2740
2741long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
2742{
2743    /* This is only valid for single tasks */
2744    if (pid <= 0 || tgid <= 0)
2745        return -EINVAL;
2746
2747    /* Not even root can pretend to send signals from the kernel.
2748     * Nor can they impersonate a kill()/tgkill(), which adds source info.
2749     */
2750    if (info->si_code >= 0 || info->si_code == SI_TKILL) {
2751        /* We used to allow any < 0 si_code */
2752        WARN_ON_ONCE(info->si_code < 0);
2753        return -EPERM;
2754    }
2755    info->si_signo = sig;
2756
2757    return do_send_specific(tgid, pid, sig, info);
2758}
2759
2760SYSCALL_DEFINE4(rt_tgsigqueueinfo, pid_t, tgid, pid_t, pid, int, sig,
2761        siginfo_t __user *, uinfo)
2762{
2763    siginfo_t info;
2764
2765    if (copy_from_user(&info, uinfo, sizeof(siginfo_t)))
2766        return -EFAULT;
2767
2768    return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
2769}
2770
2771int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
2772{
2773    struct task_struct *t = current;
2774    struct k_sigaction *k;
2775    sigset_t mask;
2776
2777    if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig)))
2778        return -EINVAL;
2779
2780    k = &t->sighand->action[sig-1];
2781
2782    spin_lock_irq(&current->sighand->siglock);
2783    if (oact)
2784        *oact = *k;
2785
2786    if (act) {
2787        sigdelsetmask(&act->sa.sa_mask,
2788                  sigmask(SIGKILL) | sigmask(SIGSTOP));
2789        *k = *act;
2790        /*
2791         * POSIX 3.3.1.3:
2792         * "Setting a signal action to SIG_IGN for a signal that is
2793         * pending shall cause the pending signal to be discarded,
2794         * whether or not it is blocked."
2795         *
2796         * "Setting a signal action to SIG_DFL for a signal that is
2797         * pending and whose default action is to ignore the signal
2798         * (for example, SIGCHLD), shall cause the pending signal to
2799         * be discarded, whether or not it is blocked"
2800         */
2801        if (sig_handler_ignored(sig_handler(t, sig), sig)) {
2802            sigemptyset(&mask);
2803            sigaddset(&mask, sig);
2804            rm_from_queue_full(&mask, &t->signal->shared_pending);
2805            do {
2806                rm_from_queue_full(&mask, &t->pending);
2807                t = next_thread(t);
2808            } while (t != current);
2809        }
2810    }
2811
2812    spin_unlock_irq(&current->sighand->siglock);
2813    return 0;
2814}
2815
2816int
2817do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long sp)
2818{
2819    stack_t oss;
2820    int error;
2821
2822    oss.ss_sp = (void __user *) current->sas_ss_sp;
2823    oss.ss_size = current->sas_ss_size;
2824    oss.ss_flags = sas_ss_flags(sp);
2825
2826    if (uss) {
2827        void __user *ss_sp;
2828        size_t ss_size;
2829        int ss_flags;
2830
2831        error = -EFAULT;
2832        if (!access_ok(VERIFY_READ, uss, sizeof(*uss)))
2833            goto out;
2834        error = __get_user(ss_sp, &uss->ss_sp) |
2835            __get_user(ss_flags, &uss->ss_flags) |
2836            __get_user(ss_size, &uss->ss_size);
2837        if (error)
2838            goto out;
2839
2840        error = -EPERM;
2841        if (on_sig_stack(sp))
2842            goto out;
2843
2844        error = -EINVAL;
2845        /*
2846         * Note - this code used to test ss_flags incorrectly:
2847         * old code may have been written using ss_flags==0
2848         * to mean ss_flags==SS_ONSTACK (as this was the only
2849         * way that worked) - this fix preserves that older
2850         * mechanism.
2851         */
2852        if (ss_flags != SS_DISABLE && ss_flags != SS_ONSTACK && ss_flags != 0)
2853            goto out;
2854
2855        if (ss_flags == SS_DISABLE) {
2856            ss_size = 0;
2857            ss_sp = NULL;
2858        } else {
2859            error = -ENOMEM;
2860            if (ss_size < MINSIGSTKSZ)
2861                goto out;
2862        }
2863
2864        current->sas_ss_sp = (unsigned long) ss_sp;
2865        current->sas_ss_size = ss_size;
2866    }
2867
2868    error = 0;
2869    if (uoss) {
2870        error = -EFAULT;
2871        if (!access_ok(VERIFY_WRITE, uoss, sizeof(*uoss)))
2872            goto out;
2873        error = __put_user(oss.ss_sp, &uoss->ss_sp) |
2874            __put_user(oss.ss_size, &uoss->ss_size) |
2875            __put_user(oss.ss_flags, &uoss->ss_flags);
2876    }
2877
2878out:
2879    return error;
2880}
2881
2882#ifdef __ARCH_WANT_SYS_SIGPENDING
2883
2884/**
2885 * sys_sigpending - examine pending signals
2886 * @set: where mask of pending signal is returned
2887 */
2888SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, set)
2889{
2890    return do_sigpending(set, sizeof(*set));
2891}
2892
2893#endif
2894
2895#ifdef __ARCH_WANT_SYS_SIGPROCMASK
2896/**
2897 * sys_sigprocmask - examine and change blocked signals
2898 * @how: whether to add, remove, or set signals
2899 * @nset: signals to add or remove (if non-null)
2900 * @oset: previous value of signal mask if non-null
2901 *
2902 * Some platforms have their own version with special arguments;
2903 * others support only sys_rt_sigprocmask.
2904 */
2905
2906SYSCALL_DEFINE3(sigprocmask, int, how, old_sigset_t __user *, nset,
2907        old_sigset_t __user *, oset)
2908{
2909    old_sigset_t old_set, new_set;
2910    sigset_t new_blocked;
2911
2912    old_set = current->blocked.sig[0];
2913
2914    if (nset) {
2915        if (copy_from_user(&new_set, nset, sizeof(*nset)))
2916            return -EFAULT;
2917        new_set &= ~(sigmask(SIGKILL) | sigmask(SIGSTOP));
2918
2919        new_blocked = current->blocked;
2920
2921        switch (how) {
2922        case SIG_BLOCK:
2923            sigaddsetmask(&new_blocked, new_set);
2924            break;
2925        case SIG_UNBLOCK:
2926            sigdelsetmask(&new_blocked, new_set);
2927            break;
2928        case SIG_SETMASK:
2929            new_blocked.sig[0] = new_set;
2930            break;
2931        default:
2932            return -EINVAL;
2933        }
2934
2935        set_current_blocked(&new_blocked);
2936    }
2937
2938    if (oset) {
2939        if (copy_to_user(oset, &old_set, sizeof(*oset)))
2940            return -EFAULT;
2941    }
2942
2943    return 0;
2944}
2945#endif /* __ARCH_WANT_SYS_SIGPROCMASK */
2946
2947#ifdef __ARCH_WANT_SYS_RT_SIGACTION
2948/**
2949 * sys_rt_sigaction - alter an action taken by a process
2950 * @sig: signal to be sent
2951 * @act: new sigaction
2952 * @oact: used to save the previous sigaction
2953 * @sigsetsize: size of sigset_t type
2954 */
2955SYSCALL_DEFINE4(rt_sigaction, int, sig,
2956        const struct sigaction __user *, act,
2957        struct sigaction __user *, oact,
2958        size_t, sigsetsize)
2959{
2960    struct k_sigaction new_sa, old_sa;
2961    int ret = -EINVAL;
2962
2963    /* XXX: Don't preclude handling different sized sigset_t's. */
2964    if (sigsetsize != sizeof(sigset_t))
2965        goto out;
2966
2967    if (act) {
2968        if (copy_from_user(&new_sa.sa, act, sizeof(new_sa.sa)))
2969            return -EFAULT;
2970    }
2971
2972    ret = do_sigaction(sig, act ? &new_sa : NULL, oact ? &old_sa : NULL);
2973
2974    if (!ret && oact) {
2975        if (copy_to_user(oact, &old_sa.sa, sizeof(old_sa.sa)))
2976            return -EFAULT;
2977    }
2978out:
2979    return ret;
2980}
2981#endif /* __ARCH_WANT_SYS_RT_SIGACTION */
2982
2983#ifdef __ARCH_WANT_SYS_SGETMASK
2984
2985/*
2986 * For backwards compatibility. Functionality superseded by sigprocmask.
2987 */
2988SYSCALL_DEFINE0(sgetmask)
2989{
2990    /* SMP safe */
2991    return current->blocked.sig[0];
2992}
2993
2994SYSCALL_DEFINE1(ssetmask, int, newmask)
2995{
2996    int old;
2997
2998    spin_lock_irq(&current->sighand->siglock);
2999    old = current->blocked.sig[0];
3000
3001    siginitset(&current->blocked, newmask & ~(sigmask(SIGKILL)|
3002                          sigmask(SIGSTOP)));
3003    recalc_sigpending();
3004    spin_unlock_irq(&current->sighand->siglock);
3005
3006    return old;
3007}
3008#endif /* __ARCH_WANT_SGETMASK */
3009
3010#ifdef __ARCH_WANT_SYS_SIGNAL
3011/*
3012 * For backwards compatibility. Functionality superseded by sigaction.
3013 */
3014SYSCALL_DEFINE2(signal, int, sig, __sighandler_t, handler)
3015{
3016    struct k_sigaction new_sa, old_sa;
3017    int ret;
3018
3019    new_sa.sa.sa_handler = handler;
3020    new_sa.sa.sa_flags = SA_ONESHOT | SA_NOMASK;
3021    sigemptyset(&new_sa.sa.sa_mask);
3022
3023    ret = do_sigaction(sig, &new_sa, &old_sa);
3024
3025    return ret ? ret : (unsigned long)old_sa.sa.sa_handler;
3026}
3027#endif /* __ARCH_WANT_SYS_SIGNAL */
3028
3029#ifdef __ARCH_WANT_SYS_PAUSE
3030
3031SYSCALL_DEFINE0(pause)
3032{
3033    while (!signal_pending(current)) {
3034        current->state = TASK_INTERRUPTIBLE;
3035        schedule();
3036    }
3037    return -ERESTARTNOHAND;
3038}
3039
3040#endif
3041
3042#ifdef __ARCH_WANT_SYS_RT_SIGSUSPEND
3043/**
3044 * sys_rt_sigsuspend - replace the signal mask for a value with the
3045 * @unewset value until a signal is received
3046 * @unewset: new signal mask value
3047 * @sigsetsize: size of sigset_t type
3048 */
3049SYSCALL_DEFINE2(rt_sigsuspend, sigset_t __user *, unewset, size_t, sigsetsize)
3050{
3051    sigset_t newset;
3052
3053    /* XXX: Don't preclude handling different sized sigset_t's. */
3054    if (sigsetsize != sizeof(sigset_t))
3055        return -EINVAL;
3056
3057    if (copy_from_user(&newset, unewset, sizeof(newset)))
3058        return -EFAULT;
3059    sigdelsetmask(&newset, sigmask(SIGKILL)|sigmask(SIGSTOP));
3060
3061    spin_lock_irq(&current->sighand->siglock);
3062    current->saved_sigmask = current->blocked;
3063    current->blocked = newset;
3064    recalc_sigpending();
3065    spin_unlock_irq(&current->sighand->siglock);
3066
3067    current->state = TASK_INTERRUPTIBLE;
3068    schedule();
3069    set_restore_sigmask();
3070    return -ERESTARTNOHAND;
3071}
3072#endif /* __ARCH_WANT_SYS_RT_SIGSUSPEND */
3073
3074__attribute__((weak)) const char *arch_vma_name(struct vm_area_struct *vma)
3075{
3076    return NULL;
3077}
3078
3079void __init signals_init(void)
3080{
3081    sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC);
3082}
3083
3084#ifdef CONFIG_KGDB_KDB
3085#include <linux/kdb.h>
3086/*
3087 * kdb_send_sig_info - Allows kdb to send signals without exposing
3088 * signal internals. This function checks if the required locks are
3089 * available before calling the main signal code, to avoid kdb
3090 * deadlocks.
3091 */
3092void
3093kdb_send_sig_info(struct task_struct *t, struct siginfo *info)
3094{
3095    static struct task_struct *kdb_prev_t;
3096    int sig, new_t;
3097    if (!spin_trylock(&t->sighand->siglock)) {
3098        kdb_printf("Can't do kill command now.\n"
3099               "The sigmask lock is held somewhere else in "
3100               "kernel, try again later\n");
3101        return;
3102    }
3103    spin_unlock(&t->sighand->siglock);
3104    new_t = kdb_prev_t != t;
3105    kdb_prev_t = t;
3106    if (t->state != TASK_RUNNING && new_t) {
3107        kdb_printf("Process is not RUNNING, sending a signal from "
3108               "kdb risks deadlock\n"
3109               "on the run queue locks. "
3110               "The signal has _not_ been sent.\n"
3111               "Reissue the kill command if you want to risk "
3112               "the deadlock.\n");
3113        return;
3114    }
3115    sig = info->si_signo;
3116    if (send_sig_info(sig, info, t))
3117        kdb_printf("Fail to deliver Signal %d to process %d.\n",
3118               sig, t->pid);
3119    else
3120        kdb_printf("Signal %d is sent to process %d.\n", sig, t->pid);
3121}
3122#endif /* CONFIG_KGDB_KDB */
3123

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