linux-user/signal.c

   1 /*
   2  *  Emulation of Linux signals
   3  *
   4  *  Copyright (c) 2003 Fabrice Bellard
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; either version 2 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19 #include "qemu/osdep.h"
  20 #include "qemu/bitops.h"
  21 #include <sys/ucontext.h>
  22 #include <sys/resource.h>
  23
  24 #include "qemu.h"
  25 #include "qemu-common.h"
  26 #include "trace.h"
  27 #include "signal-common.h"
  28
  29 struct target_sigaltstack target_sigaltstack_used = {
  30     .ss_sp = 0,
  31     .ss_size = 0,
  32     .ss_flags = TARGET_SS_DISABLE,
  33 };
  34
  35 static struct target_sigaction sigact_table[TARGET_NSIG];
  36
  37 static void host_signal_handler(int host_signum, siginfo_t *info,
  38                                 void *puc);
  39
  40 static uint8_t host_to_target_signal_table[_NSIG] = {
  41     [SIGHUP] = TARGET_SIGHUP,
  42     [SIGINT] = TARGET_SIGINT,
  43     [SIGQUIT] = TARGET_SIGQUIT,
  44     [SIGILL] = TARGET_SIGILL,
  45     [SIGTRAP] = TARGET_SIGTRAP,
  46     [SIGABRT] = TARGET_SIGABRT,
  47 /*    [SIGIOT] = TARGET_SIGIOT,*/
  48     [SIGBUS] = TARGET_SIGBUS,
  49     [SIGFPE] = TARGET_SIGFPE,
  50     [SIGKILL] = TARGET_SIGKILL,
  51     [SIGUSR1] = TARGET_SIGUSR1,
  52     [SIGSEGV] = TARGET_SIGSEGV,
  53     [SIGUSR2] = TARGET_SIGUSR2,
  54     [SIGPIPE] = TARGET_SIGPIPE,
  55     [SIGALRM] = TARGET_SIGALRM,
  56     [SIGTERM] = TARGET_SIGTERM,
  57 #ifdef SIGSTKFLT
  58     [SIGSTKFLT] = TARGET_SIGSTKFLT,
  59 #endif
  60     [SIGCHLD] = TARGET_SIGCHLD,
  61     [SIGCONT] = TARGET_SIGCONT,
  62     [SIGSTOP] = TARGET_SIGSTOP,
  63     [SIGTSTP] = TARGET_SIGTSTP,
  64     [SIGTTIN] = TARGET_SIGTTIN,
  65     [SIGTTOU] = TARGET_SIGTTOU,
  66     [SIGURG] = TARGET_SIGURG,
  67     [SIGXCPU] = TARGET_SIGXCPU,
  68     [SIGXFSZ] = TARGET_SIGXFSZ,
  69     [SIGVTALRM] = TARGET_SIGVTALRM,
  70     [SIGPROF] = TARGET_SIGPROF,
  71     [SIGWINCH] = TARGET_SIGWINCH,
  72     [SIGIO] = TARGET_SIGIO,
  73     [SIGPWR] = TARGET_SIGPWR,
  74     [SIGSYS] = TARGET_SIGSYS,
  75     /* next signals stay the same */
  76     /* Nasty hack: Reverse SIGRTMIN and SIGRTMAX to avoid overlap with
  77        host libpthread signals.  This assumes no one actually uses SIGRTMAX :-/
  78        To fix this properly we need to do manual signal delivery multiplexed
  79        over a single host signal.  */
  80     [__SIGRTMIN] = __SIGRTMAX,
  81     [__SIGRTMAX] = __SIGRTMIN,
  82 };
  83 static uint8_t target_to_host_signal_table[_NSIG];
  84
  85 int host_to_target_signal(int sig)
  86 {
  87     if (sig < 0 || sig >= _NSIG)
  88         return sig;
  89     return host_to_target_signal_table[sig];
  90 }
  91
  92 int target_to_host_signal(int sig)
  93 {
  94     if (sig < 0 || sig >= _NSIG)
  95         return sig;
  96     return target_to_host_signal_table[sig];
  97 }
  98
  99 static inline void target_sigaddset(target_sigset_t *set, int signum)
 100 {
 101     signum--;
 102     abi_ulong mask = (abi_ulong)1 << (signum % TARGET_NSIG_BPW);
 103     set->sig[signum / TARGET_NSIG_BPW] |= mask;
 104 }
 105
 106 static inline int target_sigismember(const target_sigset_t *set, int signum)
 107 {
 108     signum--;
 109     abi_ulong mask = (abi_ulong)1 << (signum % TARGET_NSIG_BPW);
 110     return ((set->sig[signum / TARGET_NSIG_BPW] & mask) != 0);
 111 }
 112
 113 void host_to_target_sigset_internal(target_sigset_t *d,
 114                                     const sigset_t *s)
 115 {
 116     int i;
 117     target_sigemptyset(d);
 118     for (i = 1; i <= TARGET_NSIG; i++) {
 119         if (sigismember(s, i)) {
 120             target_sigaddset(d, host_to_target_signal(i));
 121         }
 122     }
 123 }
 124
 125 void host_to_target_sigset(target_sigset_t *d, const sigset_t *s)
 126 {
 127     target_sigset_t d1;
 128     int i;
 129
 130     host_to_target_sigset_internal(&d1, s);
 131     for(i = 0;i < TARGET_NSIG_WORDS; i++)
 132         d->sig[i] = tswapal(d1.sig[i]);
 133 }
 134
 135 void target_to_host_sigset_internal(sigset_t *d,
 136                                     const target_sigset_t *s)
 137 {
 138     int i;
 139     sigemptyset(d);
 140     for (i = 1; i <= TARGET_NSIG; i++) {
 141         if (target_sigismember(s, i)) {
 142             sigaddset(d, target_to_host_signal(i));
 143         }
 144     }
 145 }
 146
 147 void target_to_host_sigset(sigset_t *d, const target_sigset_t *s)
 148 {
 149     target_sigset_t s1;
 150     int i;
 151
 152     for(i = 0;i < TARGET_NSIG_WORDS; i++)
 153         s1.sig[i] = tswapal(s->sig[i]);
 154     target_to_host_sigset_internal(d, &s1);
 155 }
 156
 157 void host_to_target_old_sigset(abi_ulong *old_sigset,
 158                                const sigset_t *sigset)
 159 {
 160     target_sigset_t d;
 161     host_to_target_sigset(&d, sigset);
 162     *old_sigset = d.sig[0];
 163 }
 164
 165 void target_to_host_old_sigset(sigset_t *sigset,
 166                                const abi_ulong *old_sigset)
 167 {
 168     target_sigset_t d;
 169     int i;
 170
 171     d.sig[0] = *old_sigset;
 172     for(i = 1;i < TARGET_NSIG_WORDS; i++)
 173         d.sig[i] = 0;
 174     target_to_host_sigset(sigset, &d);
 175 }
 176
 177 int block_signals(void)
 178 {
 179     TaskState *ts = (TaskState *)thread_cpu->opaque;
 180     sigset_t set;
 181
 182     /* It's OK to block everything including SIGSEGV, because we won't
 183      * run any further guest code before unblocking signals in
 184      * process_pending_signals().
 185      */
 186     sigfillset(&set);
 187     sigprocmask(SIG_SETMASK, &set, 0);
 188
 189     return atomic_xchg(&ts->signal_pending, 1);
 190 }
 191
 192 /* Wrapper for sigprocmask function
 193  * Emulates a sigprocmask in a safe way for the guest. Note that set and oldset
 194  * are host signal set, not guest ones. Returns -TARGET_ERESTARTSYS if
 195  * a signal was already pending and the syscall must be restarted, or
 196  * 0 on success.
 197  * If set is NULL, this is guaranteed not to fail.
 198  */
 199 int do_sigprocmask(int how, const sigset_t *set, sigset_t *oldset)
 200 {
 201     TaskState *ts = (TaskState *)thread_cpu->opaque;
 202
 203     if (oldset) {
 204         *oldset = ts->signal_mask;
 205     }
 206
 207     if (set) {
 208         int i;
 209
 210         if (block_signals()) {
 211             return -TARGET_ERESTARTSYS;
 212         }
 213
 214         switch (how) {
 215         case SIG_BLOCK:
 216             sigorset(&ts->signal_mask, &ts->signal_mask, set);
 217             break;
 218         case SIG_UNBLOCK:
 219             for (i = 1; i <= NSIG; ++i) {
 220                 if (sigismember(set, i)) {
 221                     sigdelset(&ts->signal_mask, i);
 222                 }
 223             }
 224             break;
 225         case SIG_SETMASK:
 226             ts->signal_mask = *set;
 227             break;
 228         default:
 229             g_assert_not_reached();
 230         }
 231
 232         /* Silently ignore attempts to change blocking status of KILL or STOP */
 233         sigdelset(&ts->signal_mask, SIGKILL);
 234         sigdelset(&ts->signal_mask, SIGSTOP);
 235     }
 236     return 0;
 237 }
 238
 239 #if !defined(TARGET_OPENRISC) && !defined(TARGET_NIOS2)
 240 /* Just set the guest's signal mask to the specified value; the
 241  * caller is assumed to have called block_signals() already.
 242  */
 243 void set_sigmask(const sigset_t *set)
 244 {
 245     TaskState *ts = (TaskState *)thread_cpu->opaque;
 246
 247     ts->signal_mask = *set;
 248 }
 249 #endif
 250
 251 /* sigaltstack management */
 252
 253 int on_sig_stack(unsigned long sp)
 254 {
 255     return (sp - target_sigaltstack_used.ss_sp
 256             < target_sigaltstack_used.ss_size);
 257 }
 258
 259 int sas_ss_flags(unsigned long sp)
 260 {
 261     return (target_sigaltstack_used.ss_size == 0 ? SS_DISABLE
 262             : on_sig_stack(sp) ? SS_ONSTACK : 0);
 263 }
 264
 265 abi_ulong target_sigsp(abi_ulong sp, struct target_sigaction *ka)
 266 {
 267     /*
 268      * This is the X/Open sanctioned signal stack switching.
 269      */
 270     if ((ka->sa_flags & TARGET_SA_ONSTACK) && !sas_ss_flags(sp)) {
 271         return target_sigaltstack_used.ss_sp + target_sigaltstack_used.ss_size;
 272     }
 273     return sp;
 274 }
 275
 276 void target_save_altstack(target_stack_t *uss, CPUArchState *env)
 277 {
 278     __put_user(target_sigaltstack_used.ss_sp, &uss->ss_sp);
 279     __put_user(sas_ss_flags(get_sp_from_cpustate(env)), &uss->ss_flags);
 280     __put_user(target_sigaltstack_used.ss_size, &uss->ss_size);
 281 }
 282
 283 /* siginfo conversion */
 284
 285 static inline void host_to_target_siginfo_noswap(target_siginfo_t *tinfo,
 286                                                  const siginfo_t *info)
 287 {
 288     int sig = host_to_target_signal(info->si_signo);
 289     int si_code = info->si_code;
 290     int si_type;
 291     tinfo->si_signo = sig;
 292     tinfo->si_errno = 0;
 293     tinfo->si_code = info->si_code;
 294
 295     /* This memset serves two purposes:
 296      * (1) ensure we don't leak random junk to the guest later
 297      * (2) placate false positives from gcc about fields
 298      *     being used uninitialized if it chooses to inline both this
 299      *     function and tswap_siginfo() into host_to_target_siginfo().
 300      */
 301     memset(tinfo->_sifields._pad, 0, sizeof(tinfo->_sifields._pad));
 302
 303     /* This is awkward, because we have to use a combination of
 304      * the si_code and si_signo to figure out which of the union's
 305      * members are valid. (Within the host kernel it is always possible
 306      * to tell, but the kernel carefully avoids giving userspace the
 307      * high 16 bits of si_code, so we don't have the information to
 308      * do this the easy way...) We therefore make our best guess,
 309      * bearing in mind that a guest can spoof most of the si_codes
 310      * via rt_sigqueueinfo() if it likes.
 311      *
 312      * Once we have made our guess, we record it in the top 16 bits of
 313      * the si_code, so that tswap_siginfo() later can use it.
 314      * tswap_siginfo() will strip these top bits out before writing
 315      * si_code to the guest (sign-extending the lower bits).
 316      */
 317
 318     switch (si_code) {
 319     case SI_USER:
 320     case SI_TKILL:
 321     case SI_KERNEL:
 322         /* Sent via kill(), tkill() or tgkill(), or direct from the kernel.
 323          * These are the only unspoofable si_code values.
 324          */
 325         tinfo->_sifields._kill._pid = info->si_pid;
 326         tinfo->_sifields._kill._uid = info->si_uid;
 327         si_type = QEMU_SI_KILL;
 328         break;
 329     default:
 330         /* Everything else is spoofable. Make best guess based on signal */
 331         switch (sig) {
 332         case TARGET_SIGCHLD:
 333             tinfo->_sifields._sigchld._pid = info->si_pid;
 334             tinfo->_sifields._sigchld._uid = info->si_uid;
 335             tinfo->_sifields._sigchld._status
 336                 = host_to_target_waitstatus(info->si_status);
 337             tinfo->_sifields._sigchld._utime = info->si_utime;
 338             tinfo->_sifields._sigchld._stime = info->si_stime;
 339             si_type = QEMU_SI_CHLD;
 340             break;
 341         case TARGET_SIGIO:
 342             tinfo->_sifields._sigpoll._band = info->si_band;
 343             tinfo->_sifields._sigpoll._fd = info->si_fd;
 344             si_type = QEMU_SI_POLL;
 345             break;
 346         default:
 347             /* Assume a sigqueue()/mq_notify()/rt_sigqueueinfo() source. */
 348             tinfo->_sifields._rt._pid = info->si_pid;
 349             tinfo->_sifields._rt._uid = info->si_uid;
 350             /* XXX: potential problem if 64 bit */
 351             tinfo->_sifields._rt._sigval.sival_ptr
 352                 = (abi_ulong)(unsigned long)info->si_value.sival_ptr;
 353             si_type = QEMU_SI_RT;
 354             break;
 355         }
 356         break;
 357     }
 358
 359     tinfo->si_code = deposit32(si_code, 16, 16, si_type);
 360 }
 361
 362 void tswap_siginfo(target_siginfo_t *tinfo,
 363                    const target_siginfo_t *info)
 364 {
 365     int si_type = extract32(info->si_code, 16, 16);
 366     int si_code = sextract32(info->si_code, 0, 16);
 367
 368     __put_user(info->si_signo, &tinfo->si_signo);
 369     __put_user(info->si_errno, &tinfo->si_errno);
 370     __put_user(si_code, &tinfo->si_code);
 371
 372     /* We can use our internal marker of which fields in the structure
 373      * are valid, rather than duplicating the guesswork of
 374      * host_to_target_siginfo_noswap() here.
 375      */
 376     switch (si_type) {
 377     case QEMU_SI_KILL:
 378         __put_user(info->_sifields._kill._pid, &tinfo->_sifields._kill._pid);
 379         __put_user(info->_sifields._kill._uid, &tinfo->_sifields._kill._uid);
 380         break;
 381     case QEMU_SI_TIMER:
 382         __put_user(info->_sifields._timer._timer1,
 383                    &tinfo->_sifields._timer._timer1);
 384         __put_user(info->_sifields._timer._timer2,
 385                    &tinfo->_sifields._timer._timer2);
 386         break;
 387     case QEMU_SI_POLL:
 388         __put_user(info->_sifields._sigpoll._band,
 389                    &tinfo->_sifields._sigpoll._band);
 390         __put_user(info->_sifields._sigpoll._fd,
 391                    &tinfo->_sifields._sigpoll._fd);
 392         break;
 393     case QEMU_SI_FAULT:
 394         __put_user(info->_sifields._sigfault._addr,
 395                    &tinfo->_sifields._sigfault._addr);
 396         break;
 397     case QEMU_SI_CHLD:
 398         __put_user(info->_sifields._sigchld._pid,
 399                    &tinfo->_sifields._sigchld._pid);
 400         __put_user(info->_sifields._sigchld._uid,
 401                    &tinfo->_sifields._sigchld._uid);
 402         __put_user(info->_sifields._sigchld._status,
 403                    &tinfo->_sifields._sigchld._status);
 404         __put_user(info->_sifields._sigchld._utime,
 405                    &tinfo->_sifields._sigchld._utime);
 406         __put_user(info->_sifields._sigchld._stime,
 407                    &tinfo->_sifields._sigchld._stime);
 408         break;
 409     case QEMU_SI_RT:
 410         __put_user(info->_sifields._rt._pid, &tinfo->_sifields._rt._pid);
 411         __put_user(info->_sifields._rt._uid, &tinfo->_sifields._rt._uid);
 412         __put_user(info->_sifields._rt._sigval.sival_ptr,
 413                    &tinfo->_sifields._rt._sigval.sival_ptr);
 414         break;
 415     default:
 416         g_assert_not_reached();
 417     }
 418 }
 419
 420 void host_to_target_siginfo(target_siginfo_t *tinfo, const siginfo_t *info)
 421 {
 422     target_siginfo_t tgt_tmp;
 423     host_to_target_siginfo_noswap(&tgt_tmp, info);
 424     tswap_siginfo(tinfo, &tgt_tmp);
 425 }
 426
 427 /* XXX: we support only POSIX RT signals are used. */
 428 /* XXX: find a solution for 64 bit (additional malloced data is needed) */
 429 void target_to_host_siginfo(siginfo_t *info, const target_siginfo_t *tinfo)
 430 {
 431     /* This conversion is used only for the rt_sigqueueinfo syscall,
 432      * and so we know that the _rt fields are the valid ones.
 433      */
 434     abi_ulong sival_ptr;
 435
 436     __get_user(info->si_signo, &tinfo->si_signo);
 437     __get_user(info->si_errno, &tinfo->si_errno);
 438     __get_user(info->si_code, &tinfo->si_code);
 439     __get_user(info->si_pid, &tinfo->_sifields._rt._pid);
 440     __get_user(info->si_uid, &tinfo->_sifields._rt._uid);
 441     __get_user(sival_ptr, &tinfo->_sifields._rt._sigval.sival_ptr);
 442     info->si_value.sival_ptr = (void *)(long)sival_ptr;
 443 }
 444
 445 static int fatal_signal (int sig)
 446 {
 447     switch (sig) {
 448     case TARGET_SIGCHLD:
 449     case TARGET_SIGURG:
 450     case TARGET_SIGWINCH:
 451         /* Ignored by default.  */
 452         return 0;
 453     case TARGET_SIGCONT:
 454     case TARGET_SIGSTOP:
 455     case TARGET_SIGTSTP:
 456     case TARGET_SIGTTIN:
 457     case TARGET_SIGTTOU:
 458         /* Job control signals.  */
 459         return 0;
 460     default:
 461         return 1;
 462     }
 463 }
 464
 465 /* returns 1 if given signal should dump core if not handled */
 466 static int core_dump_signal(int sig)
 467 {
 468     switch (sig) {
 469     case TARGET_SIGABRT:
 470     case TARGET_SIGFPE:
 471     case TARGET_SIGILL:
 472     case TARGET_SIGQUIT:
 473     case TARGET_SIGSEGV:
 474     case TARGET_SIGTRAP:
 475     case TARGET_SIGBUS:
 476         return (1);
 477     default:
 478         return (0);
 479     }
 480 }
 481
 482 void signal_init(void)
 483 {
 484     TaskState *ts = (TaskState *)thread_cpu->opaque;
 485     struct sigaction act;
 486     struct sigaction oact;
 487     int i, j;
 488     int host_sig;
 489
 490     /* generate signal conversion tables */
 491     for(i = 1; i < _NSIG; i++) {
 492         if (host_to_target_signal_table[i] == 0)
 493             host_to_target_signal_table[i] = i;
 494     }
 495     for(i = 1; i < _NSIG; i++) {
 496         j = host_to_target_signal_table[i];
 497         target_to_host_signal_table[j] = i;
 498     }
 499
 500     /* Set the signal mask from the host mask. */
 501     sigprocmask(0, 0, &ts->signal_mask);
 502
 503     /* set all host signal handlers. ALL signals are blocked during
 504        the handlers to serialize them. */
 505     memset(sigact_table, 0, sizeof(sigact_table));
 506
 507     sigfillset(&act.sa_mask);
 508     act.sa_flags = SA_SIGINFO;
 509     act.sa_sigaction = host_signal_handler;
 510     for(i = 1; i <= TARGET_NSIG; i++) {
 511         host_sig = target_to_host_signal(i);
 512         sigaction(host_sig, NULL, &oact);
 513         if (oact.sa_sigaction == (void *)SIG_IGN) {
 514             sigact_table[i - 1]._sa_handler = TARGET_SIG_IGN;
 515         } else if (oact.sa_sigaction == (void *)SIG_DFL) {
 516             sigact_table[i - 1]._sa_handler = TARGET_SIG_DFL;
 517         }
 518         /* If there's already a handler installed then something has
 519            gone horribly wrong, so don't even try to handle that case.  */
 520         /* Install some handlers for our own use.  We need at least
 521            SIGSEGV and SIGBUS, to detect exceptions.  We can not just
 522            trap all signals because it affects syscall interrupt
 523            behavior.  But do trap all default-fatal signals.  */
 524         if (fatal_signal (i))
 525             sigaction(host_sig, &act, NULL);
 526     }
 527 }
 528
 529 /* Force a synchronously taken signal. The kernel force_sig() function
 530  * also forces the signal to "not blocked, not ignored", but for QEMU
 531  * that work is done in process_pending_signals().
 532  */
 533 void force_sig(int sig)
 534 {
 535     CPUState *cpu = thread_cpu;
 536     CPUArchState *env = cpu->env_ptr;
 537     target_siginfo_t info;
 538
 539     info.si_signo = sig;
 540     info.si_errno = 0;
 541     info.si_code = TARGET_SI_KERNEL;
 542     info._sifields._kill._pid = 0;
 543     info._sifields._kill._uid = 0;
 544     queue_signal(env, info.si_signo, QEMU_SI_KILL, &info);
 545 }
 546
 547 /* Force a SIGSEGV if we couldn't write to memory trying to set
 548  * up the signal frame. oldsig is the signal we were trying to handle
 549  * at the point of failure.
 550  */
 551 #if !defined(TARGET_RISCV)
 552 void force_sigsegv(int oldsig)
 553 {
 554     if (oldsig == SIGSEGV) {
 555         /* Make sure we don't try to deliver the signal again; this will
 556          * end up with handle_pending_signal() calling dump_core_and_abort().
 557          */
 558         sigact_table[oldsig - 1]._sa_handler = TARGET_SIG_DFL;
 559     }
 560     force_sig(TARGET_SIGSEGV);
 561 }
 562
 563 #endif
 564
 565 /* abort execution with signal */
 566 static void QEMU_NORETURN dump_core_and_abort(int target_sig)
 567 {
 568     CPUState *cpu = thread_cpu;
 569     CPUArchState *env = cpu->env_ptr;
 570     TaskState *ts = (TaskState *)cpu->opaque;
 571     int host_sig, core_dumped = 0;
 572     struct sigaction act;
 573
 574     host_sig = target_to_host_signal(target_sig);
 575     trace_user_force_sig(env, target_sig, host_sig);
 576     gdb_signalled(env, target_sig);
 577
 578     /* dump core if supported by target binary format */
 579     if (core_dump_signal(target_sig) && (ts->bprm->core_dump != NULL)) {
 580         stop_all_tasks();
 581         core_dumped =
 582             ((*ts->bprm->core_dump)(target_sig, env) == 0);
 583     }
 584     if (core_dumped) {
 585         /* we already dumped the core of target process, we don't want
 586          * a coredump of qemu itself */
 587         struct rlimit nodump;
 588         getrlimit(RLIMIT_CORE, &nodump);
 589         nodump.rlim_cur=0;
 590         setrlimit(RLIMIT_CORE, &nodump);
 591         (void) fprintf(stderr, "qemu: uncaught target signal %d (%s) - %s\n",
 592             target_sig, strsignal(host_sig), "core dumped" );
 593     }
 594
 595     /* The proper exit code for dying from an uncaught signal is
 596      * -<signal>.  The kernel doesn't allow exit() or _exit() to pass
 597      * a negative value.  To get the proper exit code we need to
 598      * actually die from an uncaught signal.  Here the default signal
 599      * handler is installed, we send ourself a signal and we wait for
 600      * it to arrive. */
 601     sigfillset(&act.sa_mask);
 602     act.sa_handler = SIG_DFL;
 603     act.sa_flags = 0;
 604     sigaction(host_sig, &act, NULL);
 605
 606     /* For some reason raise(host_sig) doesn't send the signal when
 607      * statically linked on x86-64. */
 608     kill(getpid(), host_sig);
 609
 610     /* Make sure the signal isn't masked (just reuse the mask inside
 611     of act) */
 612     sigdelset(&act.sa_mask, host_sig);
 613     sigsuspend(&act.sa_mask);
 614
 615     /* unreachable */
 616     abort();
 617 }
 618
 619 /* queue a signal so that it will be send to the virtual CPU as soon
 620    as possible */
 621 int queue_signal(CPUArchState *env, int sig, int si_type,
 622                  target_siginfo_t *info)
 623 {
 624     CPUState *cpu = ENV_GET_CPU(env);
 625     TaskState *ts = cpu->opaque;
 626
 627     trace_user_queue_signal(env, sig);
 628
 629     info->si_code = deposit32(info->si_code, 16, 16, si_type);
 630
 631     ts->sync_signal.info = *info;
 632     ts->sync_signal.pending = sig;
 633     /* signal that a new signal is pending */
 634     atomic_set(&ts->signal_pending, 1);
 635     return 1; /* indicates that the signal was queued */
 636 }
 637
 638 #ifndef HAVE_SAFE_SYSCALL
 639 static inline void rewind_if_in_safe_syscall(void *puc)
 640 {
 641     /* Default version: never rewind */
 642 }
 643 #endif
 644
 645 static void host_signal_handler(int host_signum, siginfo_t *info,
 646                                 void *puc)
 647 {
 648     CPUArchState *env = thread_cpu->env_ptr;
 649     CPUState *cpu = ENV_GET_CPU(env);
 650     TaskState *ts = cpu->opaque;
 651
 652     int sig;
 653     target_siginfo_t tinfo;
 654     ucontext_t *uc = puc;
 655     struct emulated_sigtable *k;
 656
 657     /* the CPU emulator uses some host signals to detect exceptions,
 658        we forward to it some signals */
 659     if ((host_signum == SIGSEGV || host_signum == SIGBUS)
 660         && info->si_code > 0) {
 661         if (cpu_signal_handler(host_signum, info, puc))
 662             return;
 663     }
 664
 665     /* get target signal number */
 666     sig = host_to_target_signal(host_signum);
 667     if (sig < 1 || sig > TARGET_NSIG)
 668         return;
 669     trace_user_host_signal(env, host_signum, sig);
 670
 671     rewind_if_in_safe_syscall(puc);
 672
 673     host_to_target_siginfo_noswap(&tinfo, info);
 674     k = &ts->sigtab[sig - 1];
 675     k->info = tinfo;
 676     k->pending = sig;
 677     ts->signal_pending = 1;
 678
 679     /* Block host signals until target signal handler entered. We
 680      * can't block SIGSEGV or SIGBUS while we're executing guest
 681      * code in case the guest code provokes one in the window between
 682      * now and it getting out to the main loop. Signals will be
 683      * unblocked again in process_pending_signals().
 684      *
 685      * WARNING: we cannot use sigfillset() here because the uc_sigmask
 686      * field is a kernel sigset_t, which is much smaller than the
 687      * libc sigset_t which sigfillset() operates on. Using sigfillset()
 688      * would write 0xff bytes off the end of the structure and trash
 689      * data on the struct.
 690      * We can't use sizeof(uc->uc_sigmask) either, because the libc
 691      * headers define the struct field with the wrong (too large) type.
 692      */
 693     memset(&uc->uc_sigmask, 0xff, SIGSET_T_SIZE);
 694     sigdelset(&uc->uc_sigmask, SIGSEGV);
 695     sigdelset(&uc->uc_sigmask, SIGBUS);
 696
 697     /* interrupt the virtual CPU as soon as possible */
 698     cpu_exit(thread_cpu);
 699 }
 700
 701 /* do_sigaltstack() returns target values and errnos. */
 702 /* compare linux/kernel/signal.c:do_sigaltstack() */
 703 abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong sp)
 704 {
 705     int ret;
 706     struct target_sigaltstack oss;
 707
 708     /* XXX: test errors */
 709     if(uoss_addr)
 710     {
 711         __put_user(target_sigaltstack_used.ss_sp, &oss.ss_sp);
 712         __put_user(target_sigaltstack_used.ss_size, &oss.ss_size);
 713         __put_user(sas_ss_flags(sp), &oss.ss_flags);
 714     }
 715
 716     if(uss_addr)
 717     {
 718         struct target_sigaltstack *uss;
 719         struct target_sigaltstack ss;
 720         size_t minstacksize = TARGET_MINSIGSTKSZ;
 721
 722 #if defined(TARGET_PPC64)
 723         /* ELF V2 for PPC64 has a 4K minimum stack size for signal handlers */
 724         struct image_info *image = ((TaskState *)thread_cpu->opaque)->info;
 725         if (get_ppc64_abi(image) > 1) {
 726             minstacksize = 4096;
 727         }
 728 #endif
 729
 730         ret = -TARGET_EFAULT;
 731         if (!lock_user_struct(VERIFY_READ, uss, uss_addr, 1)) {
 732             goto out;
 733         }
 734         __get_user(ss.ss_sp, &uss->ss_sp);
 735         __get_user(ss.ss_size, &uss->ss_size);
 736         __get_user(ss.ss_flags, &uss->ss_flags);
 737         unlock_user_struct(uss, uss_addr, 0);
 738
 739         ret = -TARGET_EPERM;
 740         if (on_sig_stack(sp))
 741             goto out;
 742
 743         ret = -TARGET_EINVAL;
 744         if (ss.ss_flags != TARGET_SS_DISABLE
 745             && ss.ss_flags != TARGET_SS_ONSTACK
 746             && ss.ss_flags != 0)
 747             goto out;
 748
 749         if (ss.ss_flags == TARGET_SS_DISABLE) {
 750             ss.ss_size = 0;
 751             ss.ss_sp = 0;
 752         } else {
 753             ret = -TARGET_ENOMEM;
 754             if (ss.ss_size < minstacksize) {
 755                 goto out;
 756             }
 757         }
 758
 759         target_sigaltstack_used.ss_sp = ss.ss_sp;
 760         target_sigaltstack_used.ss_size = ss.ss_size;
 761     }
 762
 763     if (uoss_addr) {
 764         ret = -TARGET_EFAULT;
 765         if (copy_to_user(uoss_addr, &oss, sizeof(oss)))
 766             goto out;
 767     }
 768
 769     ret = 0;
 770 out:
 771     return ret;
 772 }
 773
 774 /* do_sigaction() return target values and host errnos */
 775 int do_sigaction(int sig, const struct target_sigaction *act,
 776                  struct target_sigaction *oact)
 777 {
 778     struct target_sigaction *k;
 779     struct sigaction act1;
 780     int host_sig;
 781     int ret = 0;
 782
 783     if (sig < 1 || sig > TARGET_NSIG || sig == TARGET_SIGKILL || sig == TARGET_SIGSTOP) {
 784         return -TARGET_EINVAL;
 785     }
 786
 787     if (block_signals()) {
 788         return -TARGET_ERESTARTSYS;
 789     }
 790
 791     k = &sigact_table[sig - 1];
 792     if (oact) {
 793         __put_user(k->_sa_handler, &oact->_sa_handler);
 794         __put_user(k->sa_flags, &oact->sa_flags);
 795 #ifdef TARGET_ARCH_HAS_SA_RESTORER
 796         __put_user(k->sa_restorer, &oact->sa_restorer);
 797 #endif
 798         /* Not swapped.  */
 799         oact->sa_mask = k->sa_mask;
 800     }
 801     if (act) {
 802         /* FIXME: This is not threadsafe.  */
 803         __get_user(k->_sa_handler, &act->_sa_handler);
 804         __get_user(k->sa_flags, &act->sa_flags);
 805 #ifdef TARGET_ARCH_HAS_SA_RESTORER
 806         __get_user(k->sa_restorer, &act->sa_restorer);
 807 #endif
 808         /* To be swapped in target_to_host_sigset.  */
 809         k->sa_mask = act->sa_mask;
 810
 811         /* we update the host linux signal state */
 812         host_sig = target_to_host_signal(sig);
 813         if (host_sig != SIGSEGV && host_sig != SIGBUS) {
 814             sigfillset(&act1.sa_mask);
 815             act1.sa_flags = SA_SIGINFO;
 816             if (k->sa_flags & TARGET_SA_RESTART)
 817                 act1.sa_flags |= SA_RESTART;
 818             /* NOTE: it is important to update the host kernel signal
 819                ignore state to avoid getting unexpected interrupted
 820                syscalls */
 821             if (k->_sa_handler == TARGET_SIG_IGN) {
 822                 act1.sa_sigaction = (void *)SIG_IGN;
 823             } else if (k->_sa_handler == TARGET_SIG_DFL) {
 824                 if (fatal_signal (sig))
 825                     act1.sa_sigaction = host_signal_handler;
 826                 else
 827                     act1.sa_sigaction = (void *)SIG_DFL;
 828             } else {
 829                 act1.sa_sigaction = host_signal_handler;
 830             }
 831             ret = sigaction(host_sig, &act1, NULL);
 832         }
 833     }
 834     return ret;
 835 }
 836
 837 static void handle_pending_signal(CPUArchState *cpu_env, int sig,
 838                                   struct emulated_sigtable *k)
 839 {
 840     CPUState *cpu = ENV_GET_CPU(cpu_env);
 841     abi_ulong handler;
 842     sigset_t set;
 843     target_sigset_t target_old_set;
 844     struct target_sigaction *sa;
 845     TaskState *ts = cpu->opaque;
 846
 847     trace_user_handle_signal(cpu_env, sig);
 848     /* dequeue signal */
 849     k->pending = 0;
 850
 851     sig = gdb_handlesig(cpu, sig);
 852     if (!sig) {
 853         sa = NULL;
 854         handler = TARGET_SIG_IGN;
 855     } else {
 856         sa = &sigact_table[sig - 1];
 857         handler = sa->_sa_handler;
 858     }
 859
 860     if (do_strace) {
 861         print_taken_signal(sig, &k->info);
 862     }
 863
 864     if (handler == TARGET_SIG_DFL) {
 865         /* default handler : ignore some signal. The other are job control or fatal */
 866         if (sig == TARGET_SIGTSTP || sig == TARGET_SIGTTIN || sig == TARGET_SIGTTOU) {
 867             kill(getpid(),SIGSTOP);
 868         } else if (sig != TARGET_SIGCHLD &&
 869                    sig != TARGET_SIGURG &&
 870                    sig != TARGET_SIGWINCH &&
 871                    sig != TARGET_SIGCONT) {
 872             dump_core_and_abort(sig);
 873         }
 874     } else if (handler == TARGET_SIG_IGN) {
 875         /* ignore sig */
 876     } else if (handler == TARGET_SIG_ERR) {
 877         dump_core_and_abort(sig);
 878     } else {
 879         /* compute the blocked signals during the handler execution */
 880         sigset_t *blocked_set;
 881
 882         target_to_host_sigset(&set, &sa->sa_mask);
 883         /* SA_NODEFER indicates that the current signal should not be
 884            blocked during the handler */
 885         if (!(sa->sa_flags & TARGET_SA_NODEFER))
 886             sigaddset(&set, target_to_host_signal(sig));
 887
 888         /* save the previous blocked signal state to restore it at the
 889            end of the signal execution (see do_sigreturn) */
 890         host_to_target_sigset_internal(&target_old_set, &ts->signal_mask);
 891
 892         /* block signals in the handler */
 893         blocked_set = ts->in_sigsuspend ?
 894             &ts->sigsuspend_mask : &ts->signal_mask;
 895         sigorset(&ts->signal_mask, blocked_set, &set);
 896         ts->in_sigsuspend = 0;
 897
 898         /* if the CPU is in VM86 mode, we restore the 32 bit values */
 899 #if defined(TARGET_I386) && !defined(TARGET_X86_64)
 900         {
 901             CPUX86State *env = cpu_env;
 902             if (env->eflags & VM_MASK)
 903                 save_v86_state(env);
 904         }
 905 #endif
 906         /* prepare the stack frame of the virtual CPU */
 907 #if defined(TARGET_ARCH_HAS_SETUP_FRAME)
 908         if (sa->sa_flags & TARGET_SA_SIGINFO) {
 909             setup_rt_frame(sig, sa, &k->info, &target_old_set, cpu_env);
 910         } else {
 911             setup_frame(sig, sa, &target_old_set, cpu_env);
 912         }
 913 #else
 914         /* These targets do not have traditional signals.  */
 915         setup_rt_frame(sig, sa, &k->info, &target_old_set, cpu_env);
 916 #endif
 917         if (sa->sa_flags & TARGET_SA_RESETHAND) {
 918             sa->_sa_handler = TARGET_SIG_DFL;
 919         }
 920     }
 921 }
 922
 923 void process_pending_signals(CPUArchState *cpu_env)
 924 {
 925     CPUState *cpu = ENV_GET_CPU(cpu_env);
 926     int sig;
 927     TaskState *ts = cpu->opaque;
 928     sigset_t set;
 929     sigset_t *blocked_set;
 930
 931     while (atomic_read(&ts->signal_pending)) {
 932         /* FIXME: This is not threadsafe.  */
 933         sigfillset(&set);
 934         sigprocmask(SIG_SETMASK, &set, 0);
 935
 936     restart_scan:
 937         sig = ts->sync_signal.pending;
 938         if (sig) {
 939             /* Synchronous signals are forced,
 940              * see force_sig_info() and callers in Linux
 941              * Note that not all of our queue_signal() calls in QEMU correspond
 942              * to force_sig_info() calls in Linux (some are send_sig_info()).
 943              * However it seems like a kernel bug to me to allow the process
 944              * to block a synchronous signal since it could then just end up
 945              * looping round and round indefinitely.
 946              */
 947             if (sigismember(&ts->signal_mask, target_to_host_signal_table[sig])
 948                 || sigact_table[sig - 1]._sa_handler == TARGET_SIG_IGN) {
 949                 sigdelset(&ts->signal_mask, target_to_host_signal_table[sig]);
 950                 sigact_table[sig - 1]._sa_handler = TARGET_SIG_DFL;
 951             }
 952
 953             handle_pending_signal(cpu_env, sig, &ts->sync_signal);
 954         }
 955
 956         for (sig = 1; sig <= TARGET_NSIG; sig++) {
 957             blocked_set = ts->in_sigsuspend ?
 958                 &ts->sigsuspend_mask : &ts->signal_mask;
 959
 960             if (ts->sigtab[sig - 1].pending &&
 961                 (!sigismember(blocked_set,
 962                               target_to_host_signal_table[sig]))) {
 963                 handle_pending_signal(cpu_env, sig, &ts->sigtab[sig - 1]);
 964                 /* Restart scan from the beginning, as handle_pending_signal
 965                  * might have resulted in a new synchronous signal (eg SIGSEGV).
 966                  */
 967                 goto restart_scan;
 968             }
 969         }
 970
 971         /* if no signal is pending, unblock signals and recheck (the act
 972          * of unblocking might cause us to take another host signal which
 973          * will set signal_pending again).
 974          */
 975         atomic_set(&ts->signal_pending, 0);
 976         ts->in_sigsuspend = 0;
 977         set = ts->signal_mask;
 978         sigdelset(&set, SIGSEGV);
 979         sigdelset(&set, SIGBUS);
 980         sigprocmask(SIG_SETMASK, &set, 0);
 981     }
 982     ts->in_sigsuspend = 0;
 983 }