minix/servers/pm/signal.c

   1 /* This file handles signals, which are asynchronous events and are generally
   2  * a messy and unpleasant business.  Signals can be generated by the KILL
   3  * system call, or from the keyboard (SIGINT) or from the clock (SIGALRM).
   4  * In all cases control eventually passes to check_sig() to see which processes
   5  * can be signaled.  The actual signaling is done by sig_proc().
   6  *
   7  * The entry points into this file are:
   8  *   do_sigaction:      perform the SIGACTION system call
   9  *   do_sigpending:     perform the SIGPENDING system call
  10  *   do_sigprocmask:    perform the SIGPROCMASK system call
  11  *   do_sigreturn:      perform the SIGRETURN system call
  12  *   do_sigsuspend:     perform the SIGSUSPEND system call
  13  *   do_kill:           perform the KILL system call
  14  *   process_ksig:      process a signal an behalf of the kernel
  15  *   sig_proc:          interrupt or terminate a signaled process
  16  *   check_sig:         check which processes to signal with sig_proc()
  17  *   check_pending:     check if a pending signal can now be delivered
  18  *   restart_sigs:      restart signal work after finishing a VFS call
  19  */
  20
  21 #include "pm.h"
  22 #include <sys/stat.h>
  23 #include <sys/ptrace.h>
  24 #include <minix/callnr.h>
  25 #include <minix/endpoint.h>
  26 #include <minix/com.h>
  27 #include <minix/vm.h>
  28 #include <signal.h>
  29 #include <sys/resource.h>
  30 #include <assert.h>
  31 #include "mproc.h"
  32
  33 static int unpause(struct mproc *rmp);
  34 static int sig_send(struct mproc *rmp, int signo);
  35 static void sig_proc_exit(struct mproc *rmp, int signo);
  36
  37 /*===========================================================================*
  38  *                              do_sigaction                                 *
  39  *===========================================================================*/
  40 int do_sigaction(void)
  41 {
  42   int r, sig_nr;
  43   struct sigaction svec;
  44   struct sigaction *svp;
  45
  46   assert(!(mp->mp_flags & (PROC_STOPPED | VFS_CALL | UNPAUSED | EVENT_CALL)));
  47
  48   sig_nr = m_in.m_lc_pm_sig.nr;
  49   if (sig_nr == SIGKILL) return(OK);
  50   if (sig_nr < 1 || sig_nr >= _NSIG) return(EINVAL);
  51
  52   svp = &mp->mp_sigact[sig_nr];
  53   if (m_in.m_lc_pm_sig.oact != 0) {
  54         r = sys_datacopy(PM_PROC_NR,(vir_bytes) svp, who_e,
  55                 m_in.m_lc_pm_sig.oact, (phys_bytes) sizeof(svec));
  56         if (r != OK) return(r);
  57   }
  58
  59   if (m_in.m_lc_pm_sig.act == 0)
  60         return(OK);
  61
  62   /* Read in the sigaction structure. */
  63   r = sys_datacopy(who_e, m_in.m_lc_pm_sig.act, PM_PROC_NR, (vir_bytes) &svec,
  64           (phys_bytes) sizeof(svec));
  65   if (r != OK) return(r);
  66
  67   if (svec.sa_handler == SIG_IGN) {
  68         sigaddset(&mp->mp_ignore, sig_nr);
  69         sigdelset(&mp->mp_sigpending, sig_nr);
  70         sigdelset(&mp->mp_ksigpending, sig_nr);
  71         sigdelset(&mp->mp_catch, sig_nr);
  72   } else if (svec.sa_handler == SIG_DFL) {
  73         sigdelset(&mp->mp_ignore, sig_nr);
  74         sigdelset(&mp->mp_catch, sig_nr);
  75   } else {
  76         sigdelset(&mp->mp_ignore, sig_nr);
  77         sigaddset(&mp->mp_catch, sig_nr);
  78   }
  79   mp->mp_sigact[sig_nr].sa_handler = svec.sa_handler;
  80   sigdelset(&svec.sa_mask, SIGKILL);
  81   sigdelset(&svec.sa_mask, SIGSTOP);
  82   mp->mp_sigact[sig_nr].sa_mask = svec.sa_mask;
  83   mp->mp_sigact[sig_nr].sa_flags = svec.sa_flags;
  84   mp->mp_sigreturn = m_in.m_lc_pm_sig.ret;
  85   return(OK);
  86 }
  87
  88 /*===========================================================================*
  89  *                              do_sigpending                                *
  90  *===========================================================================*/
  91 int do_sigpending(void)
  92 {
  93   assert(!(mp->mp_flags & (PROC_STOPPED | VFS_CALL | UNPAUSED | EVENT_CALL)));
  94
  95   mp->mp_reply.m_pm_lc_sigset.set = mp->mp_sigpending;
  96   return OK;
  97 }
  98
  99 /*===========================================================================*
 100  *                              do_sigprocmask                               *
 101  *===========================================================================*/
 102 int do_sigprocmask(void)
 103 {
 104 /* Note that the library interface passes the actual mask in sigmask_set,
 105  * not a pointer to the mask, in order to save a copy.  Similarly,
 106  * the old mask is placed in the return message which the library
 107  * interface copies (if requested) to the user specified address.
 108  *
 109  * The library interface must set SIG_INQUIRE if the 'act' argument
 110  * is NULL.
 111  *
 112  * KILL and STOP can't be masked.
 113  */
 114   sigset_t set;
 115   int i;
 116
 117   assert(!(mp->mp_flags & (PROC_STOPPED | VFS_CALL | UNPAUSED | EVENT_CALL)));
 118
 119   set = m_in.m_lc_pm_sigset.set;
 120   mp->mp_reply.m_pm_lc_sigset.set = mp->mp_sigmask;
 121
 122   switch (m_in.m_lc_pm_sigset.how) {
 123       case SIG_BLOCK:
 124         sigdelset(&set, SIGKILL);
 125         sigdelset(&set, SIGSTOP);
 126         for (i = 1; i < _NSIG; i++) {
 127                 if (sigismember(&set, i))
 128                         sigaddset(&mp->mp_sigmask, i);
 129         }
 130         break;
 131
 132       case SIG_UNBLOCK:
 133         for (i = 1; i < _NSIG; i++) {
 134                 if (sigismember(&set, i))
 135                         sigdelset(&mp->mp_sigmask, i);
 136         }
 137         check_pending(mp);
 138         break;
 139
 140       case SIG_SETMASK:
 141         sigdelset(&set, SIGKILL);
 142         sigdelset(&set, SIGSTOP);
 143         mp->mp_sigmask = set;
 144         check_pending(mp);
 145         break;
 146
 147       case SIG_INQUIRE:
 148         break;
 149
 150       default:
 151         return(EINVAL);
 152         break;
 153   }
 154   return OK;
 155 }
 156
 157 /*===========================================================================*
 158  *                              do_sigsuspend                                *
 159  *===========================================================================*/
 160 int do_sigsuspend(void)
 161 {
 162   assert(!(mp->mp_flags & (PROC_STOPPED | VFS_CALL | UNPAUSED | EVENT_CALL)));
 163
 164   mp->mp_sigmask2 = mp->mp_sigmask;     /* save the old mask */
 165   mp->mp_sigmask = m_in.m_lc_pm_sigset.set;
 166   sigdelset(&mp->mp_sigmask, SIGKILL);
 167   sigdelset(&mp->mp_sigmask, SIGSTOP);
 168   mp->mp_flags |= SIGSUSPENDED;
 169   check_pending(mp);
 170   return(SUSPEND);
 171 }
 172
 173 /*===========================================================================*
 174  *                              do_sigreturn                                 *
 175  *===========================================================================*/
 176 int do_sigreturn(void)
 177 {
 178 /* A user signal handler is done.  Restore context and check for
 179  * pending unblocked signals.
 180  */
 181   int r;
 182
 183   assert(!(mp->mp_flags & (PROC_STOPPED | VFS_CALL | UNPAUSED | EVENT_CALL)));
 184
 185   mp->mp_sigmask = m_in.m_lc_pm_sigset.set;
 186   sigdelset(&mp->mp_sigmask, SIGKILL);
 187   sigdelset(&mp->mp_sigmask, SIGSTOP);
 188
 189   r = sys_sigreturn(who_e, (struct sigmsg *)m_in.m_lc_pm_sigset.ctx);
 190   check_pending(mp);
 191   return(r);
 192 }
 193
 194 /*===========================================================================*
 195  *                              do_kill                                      *
 196  *===========================================================================*/
 197 int do_kill(void)
 198 {
 199 /* Perform the kill(pid, signo) system call. */
 200
 201   return check_sig(m_in.m_lc_pm_sig.pid, m_in.m_lc_pm_sig.nr, FALSE /* ksig */);
 202 }
 203
 204 /*===========================================================================*
 205  *                            do_srv_kill                                    *
 206  *===========================================================================*/
 207 int do_srv_kill(void)
 208 {
 209 /* Perform the srv_kill(pid, signo) system call. */
 210
 211   /* Only RS is allowed to use srv_kill. */
 212   if (mp->mp_endpoint != RS_PROC_NR)
 213         return EPERM;
 214
 215   /* Pretend the signal comes from the kernel when RS wants to deliver a signal
 216    * to a system process. RS sends a SIGKILL when it wants to perform cleanup.
 217    * In that case, ksig == TRUE forces PM to exit the process immediately.
 218    */
 219   return check_sig(m_in.m_rs_pm_srv_kill.pid, m_in.m_rs_pm_srv_kill.nr,
 220           TRUE /* ksig */);
 221 }
 222
 223 /*===========================================================================*
 224  *                              stop_proc                                    *
 225  *===========================================================================*/
 226 static int stop_proc(struct mproc *rmp, int may_delay)
 227 {
 228 /* Try to stop the given process in the kernel. If successful, mark the process
 229  * as stopped and return TRUE.  If the process is still busy sending a message,
 230  * the behavior depends on the 'may_delay' parameter. If set, the process will
 231  * be marked as having a delay call pending, and the function returns FALSE. If
 232  * not set, the caller already knows that the process has no delay call, and PM
 233  * will panic.
 234  */
 235   int r;
 236
 237   assert(!(rmp->mp_flags & (PROC_STOPPED | DELAY_CALL | UNPAUSED)));
 238
 239   r = sys_delay_stop(rmp->mp_endpoint);
 240
 241   /* If the process is still busy sending a message, the kernel will give us
 242    * EBUSY now and send a SIGSNDELAY to the process as soon as sending is done.
 243    */
 244   switch (r) {
 245   case OK:
 246         rmp->mp_flags |= PROC_STOPPED;
 247
 248         return TRUE;
 249
 250   case EBUSY:
 251         if (!may_delay)
 252                 panic("stop_proc: unexpected delay call");
 253
 254         rmp->mp_flags |= DELAY_CALL;
 255
 256         return FALSE;
 257
 258   default:
 259         panic("sys_delay_stop failed: %d", r);
 260   }
 261 }
 262
 263 /*===========================================================================*
 264  *                              try_resume_proc                              *
 265  *===========================================================================*/
 266 static void try_resume_proc(struct mproc *rmp)
 267 {
 268 /* Resume the given process if possible. */
 269   int r;
 270
 271   assert(rmp->mp_flags & PROC_STOPPED);
 272
 273   /* If the process is blocked on a VFS call or a process event notification,
 274    * do not resume it now.  Most likely it will be unpausing, in which case the
 275    * process must remain stopped.  Otherwise, it will still be resumed once the
 276    * VFS or event call is replied to.  If the process has died, do not resume
 277    * it either.
 278    */
 279   if (rmp->mp_flags & (VFS_CALL | EVENT_CALL | EXITING))
 280         return;
 281
 282   if ((r = sys_resume(rmp->mp_endpoint)) != OK)
 283         panic("sys_resume failed: %d", r);
 284
 285   /* Also unset the unpaused flag. We can safely assume that a stopped process
 286    * need only be unpaused once, but once it is resumed, all bets are off.
 287    */
 288   rmp->mp_flags &= ~(PROC_STOPPED | UNPAUSED);
 289 }
 290
 291 /*===========================================================================*
 292  *                              process_ksig                                 *
 293  *===========================================================================*/
 294 int process_ksig(endpoint_t proc_nr_e, int signo)
 295 {
 296   register struct mproc *rmp;
 297   int proc_nr;
 298   pid_t proc_id, id;
 299
 300   if(pm_isokendpt(proc_nr_e, &proc_nr) != OK) {
 301         printf("PM: process_ksig: %d?? not ok\n", proc_nr_e);
 302         return EDEADEPT; /* process is gone. */
 303   }
 304   rmp = &mproc[proc_nr];
 305   if ((rmp->mp_flags & (IN_USE | EXITING)) != IN_USE) {
 306 #if 0
 307         printf("PM: process_ksig: %d?? exiting / not in use\n", proc_nr_e);
 308 #endif
 309         return EDEADEPT; /* process is gone. */
 310   }
 311   proc_id = rmp->mp_pid;
 312   mp = &mproc[0];                       /* pretend signals are from PM */
 313   mp->mp_procgrp = rmp->mp_procgrp;     /* get process group right */
 314
 315   /* For SIGVTALRM and SIGPROF, see if we need to restart a
 316    * virtual timer. For SIGINT, SIGINFO, SIGWINCH and SIGQUIT, use proc_id 0
 317    * to indicate a broadcast to the recipient's process group.  For
 318    * SIGKILL, use proc_id -1 to indicate a systemwide broadcast.
 319    */
 320   switch (signo) {
 321       case SIGINT:
 322       case SIGQUIT:
 323       case SIGWINCH:
 324       case SIGINFO:
 325         id = 0; break;  /* broadcast to process group */
 326       case SIGVTALRM:
 327       case SIGPROF:
 328         check_vtimer(proc_nr, signo);
 329         /* fall-through */
 330       default:
 331         id = proc_id;
 332         break;
 333   }
 334   check_sig(id, signo, TRUE /* ksig */);
 335   mp->mp_procgrp = 0;                   /* restore proper PM process group */
 336
 337   /* If SIGSNDELAY is set, an earlier sys_stop() failed because the process was
 338    * still sending, and the kernel hereby tells us that the process is now done
 339    * with that. We can now try to resume what we planned to do in the first
 340    * place: set up a signal handler. However, the process's message may have
 341    * been a call to PM, in which case the process may have changed any of its
 342    * signal settings. The process may also have forked, exited etcetera.
 343    */
 344   if (signo == SIGSNDELAY && (rmp->mp_flags & DELAY_CALL)) {
 345         /* When getting SIGSNDELAY, the process is stopped at least until the
 346          * receipt of the SIGSNDELAY signal is acknowledged to the kernel. The
 347          * process is not stopped on PROC_STOP in the kernel. However, now that
 348          * there is no longer a delay call, stop_proc() is guaranteed to
 349          * succeed immediately.
 350          */
 351         rmp->mp_flags &= ~DELAY_CALL;
 352
 353         assert(!(rmp->mp_flags & PROC_STOPPED));
 354
 355         /* If the delay call was to PM, it may have resulted in a VFS call. In
 356          * that case, we must wait with further signal processing until VFS has
 357          * replied. Stop the process.
 358          */
 359         if (rmp->mp_flags & (VFS_CALL | EVENT_CALL)) {
 360                 stop_proc(rmp, FALSE /*may_delay*/);
 361
 362                 return OK;
 363         }
 364
 365         /* Process as many normal signals as possible. */
 366         check_pending(rmp);
 367
 368         assert(!(rmp->mp_flags & DELAY_CALL));
 369   }
 370
 371   /* See if the process is still alive */
 372   if ((mproc[proc_nr].mp_flags & (IN_USE | EXITING)) == IN_USE)  {
 373       return OK; /* signal has been delivered */
 374   }
 375   else {
 376       return EDEADEPT; /* process is gone */
 377   }
 378 }
 379
 380 /*===========================================================================*
 381  *                              sig_proc                                     *
 382  *===========================================================================*/
 383 void
 384 sig_proc(
 385         register struct mproc *rmp,     /* pointer to the process to be signaled */
 386         int signo,                      /* signal to send to process (1 to _NSIG-1) */
 387         int trace,                      /* pass signal to tracer first? */
 388         int ksig                        /* non-zero means signal comes from kernel  */
 389 )
 390 {
 391 /* Send a signal to a process.  Check to see if the signal is to be caught,
 392  * ignored, tranformed into a message (for system processes) or blocked.
 393  *  - If the signal is to be transformed into a message, request the KERNEL to
 394  * send the target process a system notification with the pending signal as an
 395  * argument.
 396  *  - If the signal is to be caught, request the KERNEL to push a sigcontext
 397  * structure and a sigframe structure onto the catcher's stack.  Also, KERNEL
 398  * will reset the program counter and stack pointer, so that when the process
 399  * next runs, it will be executing the signal handler. When the signal handler
 400  * returns,  sigreturn(2) will be called.  Then KERNEL will restore the signal
 401  * context from the sigcontext structure.
 402  * If there is insufficient stack space, kill the process.
 403  */
 404   int slot, badignore;
 405
 406   slot = (int) (rmp - mproc);
 407   if ((rmp->mp_flags & (IN_USE | EXITING)) != IN_USE) {
 408         panic("PM: signal %d sent to exiting process %d\n", signo, slot);
 409   }
 410
 411   if (trace == TRUE && rmp->mp_tracer != NO_TRACER && signo != SIGKILL) {
 412         /* Signal should be passed to the debugger first.
 413          * This happens before any checks on block/ignore masks; otherwise,
 414          * the process itself could block/ignore debugger signals.
 415          */
 416
 417         sigaddset(&rmp->mp_sigtrace, signo);
 418
 419         if (!(rmp->mp_flags & TRACE_STOPPED))
 420                 trace_stop(rmp, signo); /* a signal causes it to stop */
 421
 422         return;
 423   }
 424
 425   if (rmp->mp_flags & (VFS_CALL | EVENT_CALL)) {
 426         sigaddset(&rmp->mp_sigpending, signo);
 427         if(ksig)
 428                 sigaddset(&rmp->mp_ksigpending, signo);
 429
 430         /* Process the signal once VFS and process event subscribers reply.
 431          * Stop the process in the meantime, so that it cannot make another
 432          * call after the VFS reply comes in but before we look at its signals
 433          * again. Since we always stop the process to deliver signals during a
 434          * VFS or event call, the PROC_STOPPED flag doubles as an indicator in
 435          * restart_sigs() that signals must be rechecked after a reply arrives.
 436          */
 437         if (!(rmp->mp_flags & (PROC_STOPPED | DELAY_CALL))) {
 438                 /* If a VFS call is ongoing and the process is not yet stopped,
 439                  * the process must have made a call to PM. Therefore, there
 440                  * can be no delay calls in this case.
 441                  */
 442                 stop_proc(rmp, FALSE /*delay_call*/);
 443         }
 444         return;
 445   }
 446
 447   /* Handle system signals for system processes first. */
 448   if(rmp->mp_flags & PRIV_PROC) {
 449         /* Always skip signals for PM (only necessary when broadcasting). */
 450         if(rmp->mp_endpoint == PM_PROC_NR) {
 451                 return;
 452         }
 453
 454         /* System signals have always to go through the kernel first to let it
 455          * pick the right signal manager. If PM is the assigned signal manager,
 456          * the signal will come back and will actually be processed.
 457          */
 458         if(!ksig) {
 459                 sys_kill(rmp->mp_endpoint, signo);
 460                 return;
 461         }
 462
 463         /* Print stacktrace if necessary. */
 464         if(SIGS_IS_STACKTRACE(signo)) {
 465                 sys_diagctl_stacktrace(rmp->mp_endpoint);
 466         }
 467
 468         if(!SIGS_IS_TERMINATION(signo)) {
 469                 /* Translate every non-termination sys signal into a message. */
 470                 message m;
 471                 m.m_type = SIGS_SIGNAL_RECEIVED;
 472                 m.m_pm_lsys_sigs_signal.num = signo;
 473                 asynsend3(rmp->mp_endpoint, &m, AMF_NOREPLY);
 474         }
 475         else {
 476                 /* Exit the process in case of termination system signal. */
 477                 sig_proc_exit(rmp, signo);
 478         }
 479         return;
 480   }
 481
 482   /* Handle user processes now. See if the signal cannot be safely ignored. */
 483   badignore = ksig && sigismember(&noign_sset, signo) && (
 484           sigismember(&rmp->mp_ignore, signo) ||
 485           sigismember(&rmp->mp_sigmask, signo));
 486
 487   if (!badignore && sigismember(&rmp->mp_ignore, signo)) {
 488         /* Signal should be ignored. */
 489         return;
 490   }
 491   if (!badignore && sigismember(&rmp->mp_sigmask, signo)) {
 492         /* Signal should be blocked. */
 493         sigaddset(&rmp->mp_sigpending, signo);
 494         if(ksig)
 495                 sigaddset(&rmp->mp_ksigpending, signo);
 496         return;
 497   }
 498
 499   if ((rmp->mp_flags & TRACE_STOPPED) && signo != SIGKILL) {
 500         /* If the process is stopped for a debugger, do not deliver any signals
 501          * (except SIGKILL) in order not to confuse the debugger. The signals
 502          * will be delivered using the check_pending() calls in do_trace().
 503          */
 504         sigaddset(&rmp->mp_sigpending, signo);
 505         if(ksig)
 506                 sigaddset(&rmp->mp_ksigpending, signo);
 507         return;
 508   }
 509   if (!badignore && sigismember(&rmp->mp_catch, signo)) {
 510         /* Signal is caught. First interrupt the process's current call, if
 511          * applicable. This may involve a roundtrip to VFS, in which case we'll
 512          * have to check back later.
 513          */
 514         if (!unpause(rmp)) {
 515                 /* not yet unpaused; continue later */
 516                 sigaddset(&rmp->mp_sigpending, signo);
 517                 if(ksig)
 518                         sigaddset(&rmp->mp_ksigpending, signo);
 519
 520                 return;
 521         }
 522
 523         /* Then send the actual signal to the process, by setting up a signal
 524          * handler.
 525          */
 526         if (sig_send(rmp, signo))
 527                 return;
 528
 529         /* We were unable to spawn a signal handler. Kill the process. */
 530         printf("PM: %d can't catch signal %d - killing\n",
 531                 rmp->mp_pid, signo);
 532   }
 533   else if (!badignore && sigismember(&ign_sset, signo)) {
 534         /* Signal defaults to being ignored. */
 535         return;
 536   }
 537
 538   /* Terminate process */
 539   sig_proc_exit(rmp, signo);
 540 }
 541
 542 /*===========================================================================*
 543  *                              sig_proc_exit                                *
 544  *===========================================================================*/
 545 static void
 546 sig_proc_exit(
 547         struct mproc *rmp,              /* process that must exit */
 548         int signo                       /* signal that caused termination */
 549 )
 550 {
 551   rmp->mp_sigstatus = (char) signo;
 552   if (sigismember(&core_sset, signo)) {
 553         if(!(rmp->mp_flags & PRIV_PROC)) {
 554                 printf("PM: coredump signal %d for %d / %s\n", signo,
 555                         rmp->mp_pid, rmp->mp_name);
 556                 sys_diagctl_stacktrace(rmp->mp_endpoint);
 557         }
 558         exit_proc(rmp, 0, TRUE /*dump_core*/);
 559   }
 560   else {
 561         exit_proc(rmp, 0, FALSE /*dump_core*/);
 562   }
 563 }
 564
 565 /*===========================================================================*
 566  *                              check_sig                                    *
 567  *===========================================================================*/
 568 int check_sig(proc_id, signo, ksig)
 569 pid_t proc_id;                  /* pid of proc to sig, or 0 or -1, or -pgrp */
 570 int signo;                      /* signal to send to process (0 to _NSIG-1) */
 571 int ksig;                       /* non-zero means signal comes from kernel  */
 572 {
 573 /* Check to see if it is possible to send a signal.  The signal may have to be
 574  * sent to a group of processes.  This routine is invoked by the KILL system
 575  * call, and also when the kernel catches a DEL or other signal.
 576  */
 577
 578   register struct mproc *rmp;
 579   int count;                    /* count # of signals sent */
 580   int error_code;
 581
 582   if (signo < 0 || signo >= _NSIG) return(EINVAL);
 583
 584   /* Return EINVAL for attempts to send SIGKILL to INIT alone. */
 585   if (proc_id == INIT_PID && signo == SIGKILL) return(EINVAL);
 586
 587   /* Signal RS first when broadcasting SIGTERM. */
 588   if (proc_id == -1 && signo == SIGTERM)
 589       sys_kill(RS_PROC_NR, signo);
 590
 591   /* Search the proc table for processes to signal. Start from the end of the
 592    * table to analyze core system processes at the end when broadcasting.
 593    * (See forkexit.c about pid magic.)
 594    */
 595   count = 0;
 596   error_code = ESRCH;
 597   for (rmp = &mproc[NR_PROCS-1]; rmp >= &mproc[0]; rmp--) {
 598         if (!(rmp->mp_flags & IN_USE)) continue;
 599
 600         /* Check for selection. */
 601         if (proc_id > 0 && proc_id != rmp->mp_pid) continue;
 602         if (proc_id == 0 && mp->mp_procgrp != rmp->mp_procgrp) continue;
 603         if (proc_id == -1 && rmp->mp_pid <= INIT_PID) continue;
 604         if (proc_id < -1 && rmp->mp_procgrp != -proc_id) continue;
 605
 606         /* Do not kill servers and drivers when broadcasting SIGKILL. */
 607         if (proc_id == -1 && signo == SIGKILL &&
 608                 (rmp->mp_flags & PRIV_PROC)) continue;
 609
 610         /* Skip VM entirely as it might lead to a deadlock with its signal
 611          * manager if the manager page faults at the same time.
 612          */
 613         if (rmp->mp_endpoint == VM_PROC_NR) continue;
 614
 615         /* Disallow lethal signals sent by user processes to sys processes. */
 616         if (!ksig && SIGS_IS_LETHAL(signo) && (rmp->mp_flags & PRIV_PROC)) {
 617             error_code = EPERM;
 618             continue;
 619         }
 620
 621         /* Check for permission. */
 622         if (mp->mp_effuid != SUPER_USER
 623             && mp->mp_realuid != rmp->mp_realuid
 624             && mp->mp_effuid != rmp->mp_realuid
 625             && mp->mp_realuid != rmp->mp_effuid
 626             && mp->mp_effuid != rmp->mp_effuid) {
 627                 error_code = EPERM;
 628                 continue;
 629         }
 630
 631         count++;
 632         if (signo == 0 || (rmp->mp_flags & EXITING)) continue;
 633
 634         /* 'sig_proc' will handle the disposition of the signal.  The
 635          * signal may be caught, blocked, ignored, or cause process
 636          * termination, possibly with core dump.
 637          */
 638         sig_proc(rmp, signo, TRUE /*trace*/, ksig);
 639
 640         if (proc_id > 0) break; /* only one process being signaled */
 641   }
 642
 643   /* If the calling process has killed itself, don't reply. */
 644   if ((mp->mp_flags & (IN_USE | EXITING)) != IN_USE) return(SUSPEND);
 645   return(count > 0 ? OK : error_code);
 646 }
 647
 648 /*===========================================================================*
 649  *                              check_pending                                *
 650  *===========================================================================*/
 651 void
 652 check_pending(register struct mproc *rmp)
 653 {
 654   /* Check to see if any pending signals have been unblocked. Deliver as many
 655    * of them as we can, until we have to wait for a reply from VFS first.
 656    *
 657    * There are several places in this file where the signal mask is
 658    * changed.  At each such place, check_pending() should be called to
 659    * check for newly unblocked signals.
 660    */
 661   int i;
 662   int ksig;
 663
 664   for (i = 1; i < _NSIG; i++) {
 665         if (sigismember(&rmp->mp_sigpending, i) &&
 666                 !sigismember(&rmp->mp_sigmask, i)) {
 667                 ksig = sigismember(&rmp->mp_ksigpending, i);
 668                 sigdelset(&rmp->mp_sigpending, i);
 669                 sigdelset(&rmp->mp_ksigpending, i);
 670                 sig_proc(rmp, i, FALSE /*trace*/, ksig);
 671
 672                 if (rmp->mp_flags & (VFS_CALL | EVENT_CALL)) {
 673                         /* Signals must be rechecked upon return from the new
 674                          * VFS call, unless the process was killed. In both
 675                          * cases, the process is stopped.
 676                          */
 677                         assert(rmp->mp_flags & PROC_STOPPED);
 678                         break;
 679                 }
 680         }
 681   }
 682 }
 683
 684 /*===========================================================================*
 685  *                              restart_sigs                                 *
 686  *===========================================================================*/
 687 void
 688 restart_sigs(struct mproc *rmp)
 689 {
 690 /* VFS has replied to a request from us; do signal-related work.
 691  */
 692
 693   if (rmp->mp_flags & (VFS_CALL | EVENT_CALL | EXITING)) return;
 694
 695   if (rmp->mp_flags & TRACE_EXIT) {
 696         /* Tracer requested exit with specific exit value */
 697         exit_proc(rmp, rmp->mp_exitstatus, FALSE /*dump_core*/);
 698   }
 699   else if (rmp->mp_flags & PROC_STOPPED) {
 700         /* If a signal arrives while we are performing a VFS call, the process
 701          * will always be stopped immediately. Thus, if the process is stopped
 702          * once the reply from VFS arrives, we might have to check signals.
 703          */
 704         assert(!(rmp->mp_flags & DELAY_CALL));
 705
 706         /* We saved signal(s) for after finishing a VFS call. Deal with this.
 707          * PROC_STOPPED remains set to indicate the process is still stopped.
 708          */
 709         check_pending(rmp);
 710
 711         /* Resume the process now, unless there is a reason not to. */
 712         try_resume_proc(rmp);
 713   }
 714 }
 715
 716 /*===========================================================================*
 717  *                              unpause                                      *
 718  *===========================================================================*/
 719 static int
 720 unpause(
 721         struct mproc *rmp               /* which process */
 722 )
 723 {
 724 /* A signal is to be sent to a process.  If that process is hanging on a
 725  * system call, the system call must be terminated with EINTR.  First check if
 726  * the process is hanging on an PM call.  If not, tell VFS, so it can check for
 727  * interruptible calls such as READs and WRITEs from pipes, ttys and the like.
 728  */
 729   message m;
 730
 731   assert(!(rmp->mp_flags & (VFS_CALL | EVENT_CALL)));
 732
 733   /* If the UNPAUSED flag is set, VFS replied to an earlier unpause request. */
 734   if (rmp->mp_flags & UNPAUSED) {
 735         assert((rmp->mp_flags & (DELAY_CALL | PROC_STOPPED)) == PROC_STOPPED);
 736
 737         return TRUE;
 738   }
 739
 740   /* If the process is already stopping, don't do anything now. */
 741   if (rmp->mp_flags & DELAY_CALL)
 742         return FALSE;
 743
 744   /* Check to see if process is hanging on a WAIT or SIGSUSPEND call. */
 745   if (rmp->mp_flags & (WAITING | SIGSUSPENDED)) {
 746         /* Stop the process from running. Do not interrupt the actual call yet.
 747          * sig_send() will interrupt the call and resume the process afterward.
 748          * No delay calls: we know for a fact that the process called us.
 749          */
 750         stop_proc(rmp, FALSE /*may_delay*/);
 751
 752         return TRUE;
 753   }
 754
 755   /* Not paused in PM. Let VFS, and after that any matching process event
 756    * subscribers, try to unpause the process. The process needs to be stopped
 757    * for this. If it is not already stopped, try to stop it now. If that does
 758    * not succeed immediately, postpone signal delivery.
 759    */
 760   if (!(rmp->mp_flags & PROC_STOPPED) && !stop_proc(rmp, TRUE /*may_delay*/))
 761         return FALSE;
 762
 763   memset(&m, 0, sizeof(m));
 764   m.m_type = VFS_PM_UNPAUSE;
 765   m.VFS_PM_ENDPT = rmp->mp_endpoint;
 766
 767   tell_vfs(rmp, &m);
 768
 769   return FALSE;
 770 }
 771
 772 /*===========================================================================*
 773  *                              sig_send                                     *
 774  *===========================================================================*/
 775 static int
 776 sig_send(
 777         struct mproc *rmp,              /* what process to spawn a signal handler in */
 778         int signo                       /* signal to send to process (1 to _NSIG-1) */
 779 )
 780 {
 781 /* The process is supposed to catch this signal. Spawn a signal handler.
 782  * Return TRUE if this succeeded, FALSE otherwise.
 783  */
 784   struct sigmsg sigmsg;
 785   int i, r, sigflags, slot;
 786
 787   assert(rmp->mp_flags & PROC_STOPPED);
 788
 789   sigflags = rmp->mp_sigact[signo].sa_flags;
 790   slot = (int) (rmp - mproc);
 791
 792   if (rmp->mp_flags & SIGSUSPENDED)
 793         sigmsg.sm_mask = rmp->mp_sigmask2;
 794   else
 795         sigmsg.sm_mask = rmp->mp_sigmask;
 796   sigmsg.sm_signo = signo;
 797   sigmsg.sm_sighandler =
 798         (vir_bytes) rmp->mp_sigact[signo].sa_handler;
 799   sigmsg.sm_sigreturn = rmp->mp_sigreturn;
 800   for (i = 1; i < _NSIG; i++) {
 801         if (sigismember(&rmp->mp_sigact[signo].sa_mask, i))
 802                 sigaddset(&rmp->mp_sigmask, i);
 803   }
 804
 805   if (sigflags & SA_NODEFER)
 806         sigdelset(&rmp->mp_sigmask, signo);
 807   else
 808         sigaddset(&rmp->mp_sigmask, signo);
 809
 810   if (sigflags & SA_RESETHAND) {
 811         sigdelset(&rmp->mp_catch, signo);
 812         rmp->mp_sigact[signo].sa_handler = SIG_DFL;
 813   }
 814   sigdelset(&rmp->mp_sigpending, signo);
 815   sigdelset(&rmp->mp_ksigpending, signo);
 816
 817   /* Ask the kernel to deliver the signal */
 818   r = sys_sigsend(rmp->mp_endpoint, &sigmsg);
 819   /* sys_sigsend can fail legitimately with EFAULT or ENOMEM if the process
 820    * memory can't accommodate the signal handler.  The target process will be
 821    * killed in that case, so do not bother interrupting or resuming it.
 822    */
 823   if(r == EFAULT || r == ENOMEM) {
 824         return(FALSE);
 825   }
 826   /* Other errors are unexpected pm/kernel discrepancies. */
 827   if (r != OK) {
 828         panic("sys_sigsend failed: %d", r);
 829   }
 830
 831   /* Was the process suspended in PM? Then interrupt the blocking call. */
 832   if (rmp->mp_flags & (WAITING | SIGSUSPENDED)) {
 833         rmp->mp_flags &= ~(WAITING | SIGSUSPENDED);
 834
 835         reply(slot, EINTR);
 836
 837         /* The process must just have been stopped by unpause(), which means
 838          * that the UNPAUSE flag is not set.
 839          */
 840         assert(!(rmp->mp_flags & UNPAUSED));
 841
 842         try_resume_proc(rmp);
 843
 844         assert(!(rmp->mp_flags & PROC_STOPPED));
 845   } else {
 846         /* If the process was not suspended in PM, VFS must first have
 847          * confirmed that it has tried to unsuspend any blocking call. Thus, we
 848          * got here from restart_sigs() as part of handling PM_UNPAUSE_REPLY,
 849          * and restart_sigs() will resume the process later.
 850          */
 851         assert(rmp->mp_flags & UNPAUSED);
 852   }
 853
 854   return(TRUE);
 855 }