xref: /openbmc/qemu/bsd-user/signal.c (revision 74154d7e)
1 /*
2  *  Emulation of BSD signals
3  *
4  *  Copyright (c) 2003 - 2008 Fabrice Bellard
5  *  Copyright (c) 2013 Stacey Son
6  *
7  *  This program is free software; you can redistribute it and/or modify
8  *  it under the terms of the GNU General Public License as published by
9  *  the Free Software Foundation; either version 2 of the License, or
10  *  (at your option) any later version.
11  *
12  *  This program is distributed in the hope that it will be useful,
13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  *  GNU General Public License for more details.
16  *
17  *  You should have received a copy of the GNU General Public License
18  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
19  */
20 
21 #include "qemu/osdep.h"
22 #include "qemu.h"
23 #include "signal-common.h"
24 #include "trace.h"
25 #include "hw/core/tcg-cpu-ops.h"
26 #include "host-signal.h"
27 
28 static struct target_sigaction sigact_table[TARGET_NSIG];
29 static void host_signal_handler(int host_sig, siginfo_t *info, void *puc);
30 static void target_to_host_sigset_internal(sigset_t *d,
31         const target_sigset_t *s);
32 
33 static inline int on_sig_stack(TaskState *ts, unsigned long sp)
34 {
35     return sp - ts->sigaltstack_used.ss_sp < ts->sigaltstack_used.ss_size;
36 }
37 
38 static inline int sas_ss_flags(TaskState *ts, unsigned long sp)
39 {
40     return ts->sigaltstack_used.ss_size == 0 ? SS_DISABLE :
41         on_sig_stack(ts, sp) ? SS_ONSTACK : 0;
42 }
43 
44 /*
45  * The BSD ABIs use the same singal numbers across all the CPU architectures, so
46  * (unlike Linux) these functions are just the identity mapping. This might not
47  * be true for XyzBSD running on AbcBSD, which doesn't currently work.
48  */
49 int host_to_target_signal(int sig)
50 {
51     return sig;
52 }
53 
54 int target_to_host_signal(int sig)
55 {
56     return sig;
57 }
58 
59 static inline void target_sigemptyset(target_sigset_t *set)
60 {
61     memset(set, 0, sizeof(*set));
62 }
63 
64 static inline void target_sigaddset(target_sigset_t *set, int signum)
65 {
66     signum--;
67     uint32_t mask = (uint32_t)1 << (signum % TARGET_NSIG_BPW);
68     set->__bits[signum / TARGET_NSIG_BPW] |= mask;
69 }
70 
71 static inline int target_sigismember(const target_sigset_t *set, int signum)
72 {
73     signum--;
74     abi_ulong mask = (abi_ulong)1 << (signum % TARGET_NSIG_BPW);
75     return (set->__bits[signum / TARGET_NSIG_BPW] & mask) != 0;
76 }
77 
78 /* Adjust the signal context to rewind out of safe-syscall if we're in it */
79 static inline void rewind_if_in_safe_syscall(void *puc)
80 {
81     ucontext_t *uc = (ucontext_t *)puc;
82     uintptr_t pcreg = host_signal_pc(uc);
83 
84     if (pcreg > (uintptr_t)safe_syscall_start
85         && pcreg < (uintptr_t)safe_syscall_end) {
86         host_signal_set_pc(uc, (uintptr_t)safe_syscall_start);
87     }
88 }
89 
90 /*
91  * Note: The following take advantage of the BSD signal property that all
92  * signals are available on all architectures.
93  */
94 static void host_to_target_sigset_internal(target_sigset_t *d,
95         const sigset_t *s)
96 {
97     int i;
98 
99     target_sigemptyset(d);
100     for (i = 1; i <= NSIG; i++) {
101         if (sigismember(s, i)) {
102             target_sigaddset(d, host_to_target_signal(i));
103         }
104     }
105 }
106 
107 void host_to_target_sigset(target_sigset_t *d, const sigset_t *s)
108 {
109     target_sigset_t d1;
110     int i;
111 
112     host_to_target_sigset_internal(&d1, s);
113     for (i = 0; i < _SIG_WORDS; i++) {
114         d->__bits[i] = tswap32(d1.__bits[i]);
115     }
116 }
117 
118 static void target_to_host_sigset_internal(sigset_t *d,
119         const target_sigset_t *s)
120 {
121     int i;
122 
123     sigemptyset(d);
124     for (i = 1; i <= TARGET_NSIG; i++) {
125         if (target_sigismember(s, i)) {
126             sigaddset(d, target_to_host_signal(i));
127         }
128     }
129 }
130 
131 void target_to_host_sigset(sigset_t *d, const target_sigset_t *s)
132 {
133     target_sigset_t s1;
134     int i;
135 
136     for (i = 0; i < TARGET_NSIG_WORDS; i++) {
137         s1.__bits[i] = tswap32(s->__bits[i]);
138     }
139     target_to_host_sigset_internal(d, &s1);
140 }
141 
142 static bool has_trapno(int tsig)
143 {
144     return tsig == TARGET_SIGILL ||
145         tsig == TARGET_SIGFPE ||
146         tsig == TARGET_SIGSEGV ||
147         tsig == TARGET_SIGBUS ||
148         tsig == TARGET_SIGTRAP;
149 }
150 
151 /* Siginfo conversion. */
152 
153 /*
154  * Populate tinfo w/o swapping based on guessing which fields are valid.
155  */
156 static inline void host_to_target_siginfo_noswap(target_siginfo_t *tinfo,
157         const siginfo_t *info)
158 {
159     int sig = host_to_target_signal(info->si_signo);
160     int si_code = info->si_code;
161     int si_type;
162 
163     /*
164      * Make sure we that the variable portion of the target siginfo is zeroed
165      * out so we don't leak anything into that.
166      */
167     memset(&tinfo->_reason, 0, sizeof(tinfo->_reason));
168 
169     /*
170      * This is awkward, because we have to use a combination of the si_code and
171      * si_signo to figure out which of the union's members are valid.o We
172      * therefore make our best guess.
173      *
174      * Once we have made our guess, we record it in the top 16 bits of
175      * the si_code, so that tswap_siginfo() later can use it.
176      * tswap_siginfo() will strip these top bits out before writing
177      * si_code to the guest (sign-extending the lower bits).
178      */
179     tinfo->si_signo = sig;
180     tinfo->si_errno = info->si_errno;
181     tinfo->si_code = info->si_code;
182     tinfo->si_pid = info->si_pid;
183     tinfo->si_uid = info->si_uid;
184     tinfo->si_status = info->si_status;
185     tinfo->si_addr = (abi_ulong)(unsigned long)info->si_addr;
186     /*
187      * si_value is opaque to kernel. On all FreeBSD platforms,
188      * sizeof(sival_ptr) >= sizeof(sival_int) so the following
189      * always will copy the larger element.
190      */
191     tinfo->si_value.sival_ptr =
192         (abi_ulong)(unsigned long)info->si_value.sival_ptr;
193 
194     switch (si_code) {
195         /*
196          * All the SI_xxx codes that are defined here are global to
197          * all the signals (they have values that none of the other,
198          * more specific signal info will set).
199          */
200     case SI_USER:
201     case SI_LWP:
202     case SI_KERNEL:
203     case SI_QUEUE:
204     case SI_ASYNCIO:
205         /*
206          * Only the fixed parts are valid (though FreeBSD doesn't always
207          * set all the fields to non-zero values.
208          */
209         si_type = QEMU_SI_NOINFO;
210         break;
211     case SI_TIMER:
212         tinfo->_reason._timer._timerid = info->_reason._timer._timerid;
213         tinfo->_reason._timer._overrun = info->_reason._timer._overrun;
214         si_type = QEMU_SI_TIMER;
215         break;
216     case SI_MESGQ:
217         tinfo->_reason._mesgq._mqd = info->_reason._mesgq._mqd;
218         si_type = QEMU_SI_MESGQ;
219         break;
220     default:
221         /*
222          * We have to go based on the signal number now to figure out
223          * what's valid.
224          */
225         si_type = QEMU_SI_NOINFO;
226         if (has_trapno(sig)) {
227             tinfo->_reason._fault._trapno = info->_reason._fault._trapno;
228             si_type = QEMU_SI_FAULT;
229         }
230 #ifdef TARGET_SIGPOLL
231         /*
232          * FreeBSD never had SIGPOLL, but emulates it for Linux so there's
233          * a chance it may popup in the future.
234          */
235         if (sig == TARGET_SIGPOLL) {
236             tinfo->_reason._poll._band = info->_reason._poll._band;
237             si_type = QEMU_SI_POLL;
238         }
239 #endif
240         /*
241          * Unsure that this can actually be generated, and our support for
242          * capsicum is somewhere between weak and non-existant, but if we get
243          * one, then we know what to save.
244          */
245 #ifdef QEMU_SI_CAPSICUM
246         if (sig == TARGET_SIGTRAP) {
247             tinfo->_reason._capsicum._syscall =
248                 info->_reason._capsicum._syscall;
249             si_type = QEMU_SI_CAPSICUM;
250         }
251 #endif
252         break;
253     }
254     tinfo->si_code = deposit32(si_code, 24, 8, si_type);
255 }
256 
257 static void tswap_siginfo(target_siginfo_t *tinfo, const target_siginfo_t *info)
258 {
259     int si_type = extract32(info->si_code, 24, 8);
260     int si_code = sextract32(info->si_code, 0, 24);
261 
262     __put_user(info->si_signo, &tinfo->si_signo);
263     __put_user(info->si_errno, &tinfo->si_errno);
264     __put_user(si_code, &tinfo->si_code); /* Zero out si_type, it's internal */
265     __put_user(info->si_pid, &tinfo->si_pid);
266     __put_user(info->si_uid, &tinfo->si_uid);
267     __put_user(info->si_status, &tinfo->si_status);
268     __put_user(info->si_addr, &tinfo->si_addr);
269     /*
270      * Unswapped, because we passed it through mostly untouched.  si_value is
271      * opaque to the kernel, so we didn't bother with potentially wasting cycles
272      * to swap it into host byte order.
273      */
274     tinfo->si_value.sival_ptr = info->si_value.sival_ptr;
275 
276     /*
277      * We can use our internal marker of which fields in the structure
278      * are valid, rather than duplicating the guesswork of
279      * host_to_target_siginfo_noswap() here.
280      */
281     switch (si_type) {
282     case QEMU_SI_NOINFO:        /* No additional info */
283         break;
284     case QEMU_SI_FAULT:
285         __put_user(info->_reason._fault._trapno,
286                    &tinfo->_reason._fault._trapno);
287         break;
288     case QEMU_SI_TIMER:
289         __put_user(info->_reason._timer._timerid,
290                    &tinfo->_reason._timer._timerid);
291         __put_user(info->_reason._timer._overrun,
292                    &tinfo->_reason._timer._overrun);
293         break;
294     case QEMU_SI_MESGQ:
295         __put_user(info->_reason._mesgq._mqd, &tinfo->_reason._mesgq._mqd);
296         break;
297     case QEMU_SI_POLL:
298         /* Note: Not generated on FreeBSD */
299         __put_user(info->_reason._poll._band, &tinfo->_reason._poll._band);
300         break;
301 #ifdef QEMU_SI_CAPSICUM
302     case QEMU_SI_CAPSICUM:
303         __put_user(info->_reason._capsicum._syscall,
304                    &tinfo->_reason._capsicum._syscall);
305         break;
306 #endif
307     default:
308         g_assert_not_reached();
309     }
310 }
311 
312 int block_signals(void)
313 {
314     TaskState *ts = (TaskState *)thread_cpu->opaque;
315     sigset_t set;
316 
317     /*
318      * It's OK to block everything including SIGSEGV, because we won't run any
319      * further guest code before unblocking signals in
320      * process_pending_signals(). We depend on the FreeBSD behaivor here where
321      * this will only affect this thread's signal mask. We don't use
322      * pthread_sigmask which might seem more correct because that routine also
323      * does odd things with SIGCANCEL to implement pthread_cancel().
324      */
325     sigfillset(&set);
326     sigprocmask(SIG_SETMASK, &set, 0);
327 
328     return qatomic_xchg(&ts->signal_pending, 1);
329 }
330 
331 /* Returns 1 if given signal should dump core if not handled. */
332 static int core_dump_signal(int sig)
333 {
334     switch (sig) {
335     case TARGET_SIGABRT:
336     case TARGET_SIGFPE:
337     case TARGET_SIGILL:
338     case TARGET_SIGQUIT:
339     case TARGET_SIGSEGV:
340     case TARGET_SIGTRAP:
341     case TARGET_SIGBUS:
342         return 1;
343     default:
344         return 0;
345     }
346 }
347 
348 /* Abort execution with signal. */
349 static void QEMU_NORETURN dump_core_and_abort(int target_sig)
350 {
351     CPUArchState *env = thread_cpu->env_ptr;
352     CPUState *cpu = env_cpu(env);
353     TaskState *ts = cpu->opaque;
354     int core_dumped = 0;
355     int host_sig;
356     struct sigaction act;
357 
358     host_sig = target_to_host_signal(target_sig);
359     gdb_signalled(env, target_sig);
360 
361     /* Dump core if supported by target binary format */
362     if (core_dump_signal(target_sig) && (ts->bprm->core_dump != NULL)) {
363         stop_all_tasks();
364         core_dumped =
365             ((*ts->bprm->core_dump)(target_sig, env) == 0);
366     }
367     if (core_dumped) {
368         struct rlimit nodump;
369 
370         /*
371          * We already dumped the core of target process, we don't want
372          * a coredump of qemu itself.
373          */
374          getrlimit(RLIMIT_CORE, &nodump);
375          nodump.rlim_cur = 0;
376          setrlimit(RLIMIT_CORE, &nodump);
377          (void) fprintf(stderr, "qemu: uncaught target signal %d (%s) "
378              "- %s\n", target_sig, strsignal(host_sig), "core dumped");
379     }
380 
381     /*
382      * The proper exit code for dying from an uncaught signal is
383      * -<signal>.  The kernel doesn't allow exit() or _exit() to pass
384      * a negative value.  To get the proper exit code we need to
385      * actually die from an uncaught signal.  Here the default signal
386      * handler is installed, we send ourself a signal and we wait for
387      * it to arrive.
388      */
389     memset(&act, 0, sizeof(act));
390     sigfillset(&act.sa_mask);
391     act.sa_handler = SIG_DFL;
392     sigaction(host_sig, &act, NULL);
393 
394     kill(getpid(), host_sig);
395 
396     /*
397      * Make sure the signal isn't masked (just reuse the mask inside
398      * of act).
399      */
400     sigdelset(&act.sa_mask, host_sig);
401     sigsuspend(&act.sa_mask);
402 
403     /* unreachable */
404     abort();
405 }
406 
407 /*
408  * Queue a signal so that it will be send to the virtual CPU as soon as
409  * possible.
410  */
411 void queue_signal(CPUArchState *env, int sig, int si_type,
412                   target_siginfo_t *info)
413 {
414     CPUState *cpu = env_cpu(env);
415     TaskState *ts = cpu->opaque;
416 
417     trace_user_queue_signal(env, sig);
418 
419     info->si_code = deposit32(info->si_code, 24, 8, si_type);
420 
421     ts->sync_signal.info = *info;
422     ts->sync_signal.pending = sig;
423     /* Signal that a new signal is pending. */
424     qatomic_set(&ts->signal_pending, 1);
425     return;
426 }
427 
428 static int fatal_signal(int sig)
429 {
430 
431     switch (sig) {
432     case TARGET_SIGCHLD:
433     case TARGET_SIGURG:
434     case TARGET_SIGWINCH:
435     case TARGET_SIGINFO:
436         /* Ignored by default. */
437         return 0;
438     case TARGET_SIGCONT:
439     case TARGET_SIGSTOP:
440     case TARGET_SIGTSTP:
441     case TARGET_SIGTTIN:
442     case TARGET_SIGTTOU:
443         /* Job control signals.  */
444         return 0;
445     default:
446         return 1;
447     }
448 }
449 
450 /*
451  * Force a synchronously taken QEMU_SI_FAULT signal. For QEMU the
452  * 'force' part is handled in process_pending_signals().
453  */
454 void force_sig_fault(int sig, int code, abi_ulong addr)
455 {
456     CPUState *cpu = thread_cpu;
457     CPUArchState *env = cpu->env_ptr;
458     target_siginfo_t info = {};
459 
460     info.si_signo = sig;
461     info.si_errno = 0;
462     info.si_code = code;
463     info.si_addr = addr;
464     queue_signal(env, sig, QEMU_SI_FAULT, &info);
465 }
466 
467 static void host_signal_handler(int host_sig, siginfo_t *info, void *puc)
468 {
469     CPUArchState *env = thread_cpu->env_ptr;
470     CPUState *cpu = env_cpu(env);
471     TaskState *ts = cpu->opaque;
472     target_siginfo_t tinfo;
473     ucontext_t *uc = puc;
474     struct emulated_sigtable *k;
475     int guest_sig;
476     uintptr_t pc = 0;
477     bool sync_sig = false;
478 
479     /*
480      * Non-spoofed SIGSEGV and SIGBUS are synchronous, and need special
481      * handling wrt signal blocking and unwinding.
482      */
483     if ((host_sig == SIGSEGV || host_sig == SIGBUS) && info->si_code > 0) {
484         MMUAccessType access_type;
485         uintptr_t host_addr;
486         abi_ptr guest_addr;
487         bool is_write;
488 
489         host_addr = (uintptr_t)info->si_addr;
490 
491         /*
492          * Convert forcefully to guest address space: addresses outside
493          * reserved_va are still valid to report via SEGV_MAPERR.
494          */
495         guest_addr = h2g_nocheck(host_addr);
496 
497         pc = host_signal_pc(uc);
498         is_write = host_signal_write(info, uc);
499         access_type = adjust_signal_pc(&pc, is_write);
500 
501         if (host_sig == SIGSEGV) {
502             bool maperr = true;
503 
504             if (info->si_code == SEGV_ACCERR && h2g_valid(host_addr)) {
505                 /* If this was a write to a TB protected page, restart. */
506                 if (is_write &&
507                     handle_sigsegv_accerr_write(cpu, &uc->uc_sigmask,
508                                                 pc, guest_addr)) {
509                     return;
510                 }
511 
512                 /*
513                  * With reserved_va, the whole address space is PROT_NONE,
514                  * which means that we may get ACCERR when we want MAPERR.
515                  */
516                 if (page_get_flags(guest_addr) & PAGE_VALID) {
517                     maperr = false;
518                 } else {
519                     info->si_code = SEGV_MAPERR;
520                 }
521             }
522 
523             sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL);
524             cpu_loop_exit_sigsegv(cpu, guest_addr, access_type, maperr, pc);
525         } else {
526             sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL);
527             if (info->si_code == BUS_ADRALN) {
528                 cpu_loop_exit_sigbus(cpu, guest_addr, access_type, pc);
529             }
530         }
531 
532         sync_sig = true;
533     }
534 
535     /* Get the target signal number. */
536     guest_sig = host_to_target_signal(host_sig);
537     if (guest_sig < 1 || guest_sig > TARGET_NSIG) {
538         return;
539     }
540     trace_user_host_signal(cpu, host_sig, guest_sig);
541 
542     host_to_target_siginfo_noswap(&tinfo, info);
543 
544     k = &ts->sigtab[guest_sig - 1];
545     k->info = tinfo;
546     k->pending = guest_sig;
547     ts->signal_pending = 1;
548 
549     /*
550      * For synchronous signals, unwind the cpu state to the faulting
551      * insn and then exit back to the main loop so that the signal
552      * is delivered immediately.
553      */
554     if (sync_sig) {
555         cpu->exception_index = EXCP_INTERRUPT;
556         cpu_loop_exit_restore(cpu, pc);
557     }
558 
559     rewind_if_in_safe_syscall(puc);
560 
561     /*
562      * Block host signals until target signal handler entered. We
563      * can't block SIGSEGV or SIGBUS while we're executing guest
564      * code in case the guest code provokes one in the window between
565      * now and it getting out to the main loop. Signals will be
566      * unblocked again in process_pending_signals().
567      */
568     sigfillset(&uc->uc_sigmask);
569     sigdelset(&uc->uc_sigmask, SIGSEGV);
570     sigdelset(&uc->uc_sigmask, SIGBUS);
571 
572     /* Interrupt the virtual CPU as soon as possible. */
573     cpu_exit(thread_cpu);
574 }
575 
576 /* do_sigaltstack() returns target values and errnos. */
577 /* compare to kern/kern_sig.c sys_sigaltstack() and kern_sigaltstack() */
578 abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong sp)
579 {
580     TaskState *ts = (TaskState *)thread_cpu->opaque;
581     int ret;
582     target_stack_t oss;
583 
584     if (uoss_addr) {
585         /* Save current signal stack params */
586         oss.ss_sp = tswapl(ts->sigaltstack_used.ss_sp);
587         oss.ss_size = tswapl(ts->sigaltstack_used.ss_size);
588         oss.ss_flags = tswapl(sas_ss_flags(ts, sp));
589     }
590 
591     if (uss_addr) {
592         target_stack_t *uss;
593         target_stack_t ss;
594         size_t minstacksize = TARGET_MINSIGSTKSZ;
595 
596         ret = -TARGET_EFAULT;
597         if (!lock_user_struct(VERIFY_READ, uss, uss_addr, 1)) {
598             goto out;
599         }
600         __get_user(ss.ss_sp, &uss->ss_sp);
601         __get_user(ss.ss_size, &uss->ss_size);
602         __get_user(ss.ss_flags, &uss->ss_flags);
603         unlock_user_struct(uss, uss_addr, 0);
604 
605         ret = -TARGET_EPERM;
606         if (on_sig_stack(ts, sp)) {
607             goto out;
608         }
609 
610         ret = -TARGET_EINVAL;
611         if (ss.ss_flags != TARGET_SS_DISABLE
612             && ss.ss_flags != TARGET_SS_ONSTACK
613             && ss.ss_flags != 0) {
614             goto out;
615         }
616 
617         if (ss.ss_flags == TARGET_SS_DISABLE) {
618             ss.ss_size = 0;
619             ss.ss_sp = 0;
620         } else {
621             ret = -TARGET_ENOMEM;
622             if (ss.ss_size < minstacksize) {
623                 goto out;
624             }
625         }
626 
627         ts->sigaltstack_used.ss_sp = ss.ss_sp;
628         ts->sigaltstack_used.ss_size = ss.ss_size;
629     }
630 
631     if (uoss_addr) {
632         ret = -TARGET_EFAULT;
633         if (copy_to_user(uoss_addr, &oss, sizeof(oss))) {
634             goto out;
635         }
636     }
637 
638     ret = 0;
639 out:
640     return ret;
641 }
642 
643 /* do_sigaction() return host values and errnos */
644 int do_sigaction(int sig, const struct target_sigaction *act,
645         struct target_sigaction *oact)
646 {
647     struct target_sigaction *k;
648     struct sigaction act1;
649     int host_sig;
650     int ret = 0;
651 
652     if (sig < 1 || sig > TARGET_NSIG) {
653         return -TARGET_EINVAL;
654     }
655 
656     if ((sig == TARGET_SIGKILL || sig == TARGET_SIGSTOP) &&
657         act != NULL && act->_sa_handler != TARGET_SIG_DFL) {
658         return -TARGET_EINVAL;
659     }
660 
661     if (block_signals()) {
662         return -TARGET_ERESTART;
663     }
664 
665     k = &sigact_table[sig - 1];
666     if (oact) {
667         oact->_sa_handler = tswapal(k->_sa_handler);
668         oact->sa_flags = tswap32(k->sa_flags);
669         oact->sa_mask = k->sa_mask;
670     }
671     if (act) {
672         k->_sa_handler = tswapal(act->_sa_handler);
673         k->sa_flags = tswap32(act->sa_flags);
674         k->sa_mask = act->sa_mask;
675 
676         /* Update the host signal state. */
677         host_sig = target_to_host_signal(sig);
678         if (host_sig != SIGSEGV && host_sig != SIGBUS) {
679             memset(&act1, 0, sizeof(struct sigaction));
680             sigfillset(&act1.sa_mask);
681             act1.sa_flags = SA_SIGINFO;
682             if (k->sa_flags & TARGET_SA_RESTART) {
683                 act1.sa_flags |= SA_RESTART;
684             }
685             /*
686              *  Note: It is important to update the host kernel signal mask to
687              *  avoid getting unexpected interrupted system calls.
688              */
689             if (k->_sa_handler == TARGET_SIG_IGN) {
690                 act1.sa_sigaction = (void *)SIG_IGN;
691             } else if (k->_sa_handler == TARGET_SIG_DFL) {
692                 if (fatal_signal(sig)) {
693                     act1.sa_sigaction = host_signal_handler;
694                 } else {
695                     act1.sa_sigaction = (void *)SIG_DFL;
696                 }
697             } else {
698                 act1.sa_sigaction = host_signal_handler;
699             }
700             ret = sigaction(host_sig, &act1, NULL);
701         }
702     }
703     return ret;
704 }
705 
706 static inline abi_ulong get_sigframe(struct target_sigaction *ka,
707         CPUArchState *env, size_t frame_size)
708 {
709     TaskState *ts = (TaskState *)thread_cpu->opaque;
710     abi_ulong sp;
711 
712     /* Use default user stack */
713     sp = get_sp_from_cpustate(env);
714 
715     if ((ka->sa_flags & TARGET_SA_ONSTACK) && sas_ss_flags(ts, sp) == 0) {
716         sp = ts->sigaltstack_used.ss_sp + ts->sigaltstack_used.ss_size;
717     }
718 
719 /* TODO: make this a target_arch function / define */
720 #if defined(TARGET_ARM)
721     return (sp - frame_size) & ~7;
722 #elif defined(TARGET_AARCH64)
723     return (sp - frame_size) & ~15;
724 #else
725     return sp - frame_size;
726 #endif
727 }
728 
729 /* compare to $M/$M/exec_machdep.c sendsig and sys/kern/kern_sig.c sigexit */
730 
731 static void setup_frame(int sig, int code, struct target_sigaction *ka,
732     target_sigset_t *set, target_siginfo_t *tinfo, CPUArchState *env)
733 {
734     struct target_sigframe *frame;
735     abi_ulong frame_addr;
736     int i;
737 
738     frame_addr = get_sigframe(ka, env, sizeof(*frame));
739     trace_user_setup_frame(env, frame_addr);
740     if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
741         unlock_user_struct(frame, frame_addr, 1);
742         dump_core_and_abort(TARGET_SIGILL);
743         return;
744     }
745 
746     memset(frame, 0, sizeof(*frame));
747     setup_sigframe_arch(env, frame_addr, frame, 0);
748 
749     for (i = 0; i < TARGET_NSIG_WORDS; i++) {
750         __put_user(set->__bits[i], &frame->sf_uc.uc_sigmask.__bits[i]);
751     }
752 
753     if (tinfo) {
754         frame->sf_si.si_signo = tinfo->si_signo;
755         frame->sf_si.si_errno = tinfo->si_errno;
756         frame->sf_si.si_code = tinfo->si_code;
757         frame->sf_si.si_pid = tinfo->si_pid;
758         frame->sf_si.si_uid = tinfo->si_uid;
759         frame->sf_si.si_status = tinfo->si_status;
760         frame->sf_si.si_addr = tinfo->si_addr;
761         /* see host_to_target_siginfo_noswap() for more details */
762         frame->sf_si.si_value.sival_ptr = tinfo->si_value.sival_ptr;
763         /*
764          * At this point, whatever is in the _reason union is complete
765          * and in target order, so just copy the whole thing over, even
766          * if it's too large for this specific signal.
767          * host_to_target_siginfo_noswap() and tswap_siginfo() have ensured
768          * that's so.
769          */
770         memcpy(&frame->sf_si._reason, &tinfo->_reason,
771                sizeof(tinfo->_reason));
772     }
773 
774     set_sigtramp_args(env, sig, frame, frame_addr, ka);
775 
776     unlock_user_struct(frame, frame_addr, 1);
777 }
778 
779 static int reset_signal_mask(target_ucontext_t *ucontext)
780 {
781     int i;
782     sigset_t blocked;
783     target_sigset_t target_set;
784     TaskState *ts = (TaskState *)thread_cpu->opaque;
785 
786     for (i = 0; i < TARGET_NSIG_WORDS; i++) {
787         if (__get_user(target_set.__bits[i],
788                     &ucontext->uc_sigmask.__bits[i])) {
789             return -TARGET_EFAULT;
790         }
791     }
792     target_to_host_sigset_internal(&blocked, &target_set);
793     ts->signal_mask = blocked;
794 
795     return 0;
796 }
797 
798 /* See sys/$M/$M/exec_machdep.c sigreturn() */
799 long do_sigreturn(CPUArchState *env, abi_ulong addr)
800 {
801     long ret;
802     abi_ulong target_ucontext;
803     target_ucontext_t *ucontext = NULL;
804 
805     /* Get the target ucontext address from the stack frame */
806     ret = get_ucontext_sigreturn(env, addr, &target_ucontext);
807     if (is_error(ret)) {
808         return ret;
809     }
810     trace_user_do_sigreturn(env, addr);
811     if (!lock_user_struct(VERIFY_READ, ucontext, target_ucontext, 0)) {
812         goto badframe;
813     }
814 
815     /* Set the register state back to before the signal. */
816     if (set_mcontext(env, &ucontext->uc_mcontext, 1)) {
817         goto badframe;
818     }
819 
820     /* And reset the signal mask. */
821     if (reset_signal_mask(ucontext)) {
822         goto badframe;
823     }
824 
825     unlock_user_struct(ucontext, target_ucontext, 0);
826     return -TARGET_EJUSTRETURN;
827 
828 badframe:
829     if (ucontext != NULL) {
830         unlock_user_struct(ucontext, target_ucontext, 0);
831     }
832     return -TARGET_EFAULT;
833 }
834 
835 void signal_init(void)
836 {
837     TaskState *ts = (TaskState *)thread_cpu->opaque;
838     struct sigaction act;
839     struct sigaction oact;
840     int i;
841     int host_sig;
842 
843     /* Set the signal mask from the host mask. */
844     sigprocmask(0, 0, &ts->signal_mask);
845 
846     sigfillset(&act.sa_mask);
847     act.sa_sigaction = host_signal_handler;
848     act.sa_flags = SA_SIGINFO;
849 
850     for (i = 1; i <= TARGET_NSIG; i++) {
851 #ifdef CONFIG_GPROF
852         if (i == TARGET_SIGPROF) {
853             continue;
854         }
855 #endif
856         host_sig = target_to_host_signal(i);
857         sigaction(host_sig, NULL, &oact);
858         if (oact.sa_sigaction == (void *)SIG_IGN) {
859             sigact_table[i - 1]._sa_handler = TARGET_SIG_IGN;
860         } else if (oact.sa_sigaction == (void *)SIG_DFL) {
861             sigact_table[i - 1]._sa_handler = TARGET_SIG_DFL;
862         }
863         /*
864          * If there's already a handler installed then something has
865          * gone horribly wrong, so don't even try to handle that case.
866          * Install some handlers for our own use.  We need at least
867          * SIGSEGV and SIGBUS, to detect exceptions.  We can not just
868          * trap all signals because it affects syscall interrupt
869          * behavior.  But do trap all default-fatal signals.
870          */
871         if (fatal_signal(i)) {
872             sigaction(host_sig, &act, NULL);
873         }
874     }
875 }
876 
877 static void handle_pending_signal(CPUArchState *env, int sig,
878                                   struct emulated_sigtable *k)
879 {
880     CPUState *cpu = env_cpu(env);
881     TaskState *ts = cpu->opaque;
882     struct target_sigaction *sa;
883     int code;
884     sigset_t set;
885     abi_ulong handler;
886     target_siginfo_t tinfo;
887     target_sigset_t target_old_set;
888 
889     trace_user_handle_signal(env, sig);
890 
891     k->pending = 0;
892 
893     sig = gdb_handlesig(cpu, sig);
894     if (!sig) {
895         sa = NULL;
896         handler = TARGET_SIG_IGN;
897     } else {
898         sa = &sigact_table[sig - 1];
899         handler = sa->_sa_handler;
900     }
901 
902     if (do_strace) {
903         print_taken_signal(sig, &k->info);
904     }
905 
906     if (handler == TARGET_SIG_DFL) {
907         /*
908          * default handler : ignore some signal. The other are job
909          * control or fatal.
910          */
911         if (sig == TARGET_SIGTSTP || sig == TARGET_SIGTTIN ||
912             sig == TARGET_SIGTTOU) {
913             kill(getpid(), SIGSTOP);
914         } else if (sig != TARGET_SIGCHLD && sig != TARGET_SIGURG &&
915                    sig != TARGET_SIGINFO && sig != TARGET_SIGWINCH &&
916                    sig != TARGET_SIGCONT) {
917             dump_core_and_abort(sig);
918         }
919     } else if (handler == TARGET_SIG_IGN) {
920         /* ignore sig */
921     } else if (handler == TARGET_SIG_ERR) {
922         dump_core_and_abort(sig);
923     } else {
924         /* compute the blocked signals during the handler execution */
925         sigset_t *blocked_set;
926 
927         target_to_host_sigset(&set, &sa->sa_mask);
928         /*
929          * SA_NODEFER indicates that the current signal should not be
930          * blocked during the handler.
931          */
932         if (!(sa->sa_flags & TARGET_SA_NODEFER)) {
933             sigaddset(&set, target_to_host_signal(sig));
934         }
935 
936         /*
937          * Save the previous blocked signal state to restore it at the
938          * end of the signal execution (see do_sigreturn).
939          */
940         host_to_target_sigset_internal(&target_old_set, &ts->signal_mask);
941 
942         blocked_set = ts->in_sigsuspend ?
943             &ts->sigsuspend_mask : &ts->signal_mask;
944         sigorset(&ts->signal_mask, blocked_set, &set);
945         ts->in_sigsuspend = false;
946         sigprocmask(SIG_SETMASK, &ts->signal_mask, NULL);
947 
948         /* XXX VM86 on x86 ??? */
949 
950         code = k->info.si_code; /* From host, so no si_type */
951         /* prepare the stack frame of the virtual CPU */
952         if (sa->sa_flags & TARGET_SA_SIGINFO) {
953             tswap_siginfo(&tinfo, &k->info);
954             setup_frame(sig, code, sa, &target_old_set, &tinfo, env);
955         } else {
956             setup_frame(sig, code, sa, &target_old_set, NULL, env);
957         }
958         if (sa->sa_flags & TARGET_SA_RESETHAND) {
959             sa->_sa_handler = TARGET_SIG_DFL;
960         }
961     }
962 }
963 
964 void process_pending_signals(CPUArchState *env)
965 {
966     CPUState *cpu = env_cpu(env);
967     int sig;
968     sigset_t *blocked_set, set;
969     struct emulated_sigtable *k;
970     TaskState *ts = cpu->opaque;
971 
972     while (qatomic_read(&ts->signal_pending)) {
973         sigfillset(&set);
974         sigprocmask(SIG_SETMASK, &set, 0);
975 
976     restart_scan:
977         sig = ts->sync_signal.pending;
978         if (sig) {
979             /*
980              * Synchronous signals are forced by the emulated CPU in some way.
981              * If they are set to ignore, restore the default handler (see
982              * sys/kern_sig.c trapsignal() and execsigs() for this behavior)
983              * though maybe this is done only when forcing exit for non SIGCHLD.
984              */
985             if (sigismember(&ts->signal_mask, target_to_host_signal(sig)) ||
986                 sigact_table[sig - 1]._sa_handler == TARGET_SIG_IGN) {
987                 sigdelset(&ts->signal_mask, target_to_host_signal(sig));
988                 sigact_table[sig - 1]._sa_handler = TARGET_SIG_DFL;
989             }
990             handle_pending_signal(env, sig, &ts->sync_signal);
991         }
992 
993         k = ts->sigtab;
994         for (sig = 1; sig <= TARGET_NSIG; sig++, k++) {
995             blocked_set = ts->in_sigsuspend ?
996                 &ts->sigsuspend_mask : &ts->signal_mask;
997             if (k->pending &&
998                 !sigismember(blocked_set, target_to_host_signal(sig))) {
999                 handle_pending_signal(env, sig, k);
1000                 /*
1001                  * Restart scan from the beginning, as handle_pending_signal
1002                  * might have resulted in a new synchronous signal (eg SIGSEGV).
1003                  */
1004                 goto restart_scan;
1005             }
1006         }
1007 
1008         /*
1009          * Unblock signals and check one more time. Unblocking signals may cause
1010          * us to take another host signal, which will set signal_pending again.
1011          */
1012         qatomic_set(&ts->signal_pending, 0);
1013         ts->in_sigsuspend = false;
1014         set = ts->signal_mask;
1015         sigdelset(&set, SIGSEGV);
1016         sigdelset(&set, SIGBUS);
1017         sigprocmask(SIG_SETMASK, &set, 0);
1018     }
1019     ts->in_sigsuspend = false;
1020 }
1021 
1022 void cpu_loop_exit_sigsegv(CPUState *cpu, target_ulong addr,
1023                            MMUAccessType access_type, bool maperr, uintptr_t ra)
1024 {
1025     const struct TCGCPUOps *tcg_ops = CPU_GET_CLASS(cpu)->tcg_ops;
1026 
1027     if (tcg_ops->record_sigsegv) {
1028         tcg_ops->record_sigsegv(cpu, addr, access_type, maperr, ra);
1029     }
1030 
1031     force_sig_fault(TARGET_SIGSEGV,
1032                     maperr ? TARGET_SEGV_MAPERR : TARGET_SEGV_ACCERR,
1033                     addr);
1034     cpu->exception_index = EXCP_INTERRUPT;
1035     cpu_loop_exit_restore(cpu, ra);
1036 }
1037 
1038 void cpu_loop_exit_sigbus(CPUState *cpu, target_ulong addr,
1039                           MMUAccessType access_type, uintptr_t ra)
1040 {
1041     const struct TCGCPUOps *tcg_ops = CPU_GET_CLASS(cpu)->tcg_ops;
1042 
1043     if (tcg_ops->record_sigbus) {
1044         tcg_ops->record_sigbus(cpu, addr, access_type, ra);
1045     }
1046 
1047     force_sig_fault(TARGET_SIGBUS, TARGET_BUS_ADRALN, addr);
1048     cpu->exception_index = EXCP_INTERRUPT;
1049     cpu_loop_exit_restore(cpu, ra);
1050 }
1051