sig.c

   1 /* sig.c - interface for shell signal handlers and signal initialization. */
   2
   3 /* Copyright (C) 1994-2009 Free Software Foundation, Inc.
   4
   5    This file is part of GNU Bash, the Bourne Again SHell.
   6
   7    Bash 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 3 of the License, or
  10    (at your option) any later version.
  11
  12    Bash 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 Bash.  If not, see <http://www.gnu.org/licenses/>.
  19 */
  20
  21 #include "config.h"
  22
  23 #include "bashtypes.h"
  24
  25 #if defined (HAVE_UNISTD_H)
  26 #  ifdef _MINIX
  27 #    include <sys/types.h>
  28 #  endif
  29 #  include <unistd.h>
  30 #endif
  31
  32 #include <stdio.h>
  33 #include <signal.h>
  34
  35 #include "bashintl.h"
  36
  37 #include "shell.h"
  38 #if defined (JOB_CONTROL)
  39 #include "jobs.h"
  40 #endif /* JOB_CONTROL */
  41 #include "siglist.h"
  42 #include "sig.h"
  43 #include "trap.h"
  44
  45 #include "builtins/common.h"
  46
  47 #if defined (READLINE)
  48 #  include "bashline.h"
  49 #endif
  50
  51 #if defined (HISTORY)
  52 #  include "bashhist.h"
  53 #endif
  54
  55 extern int last_command_exit_value;
  56 extern int last_command_exit_signal;
  57 extern int return_catch_flag;
  58 extern int loop_level, continuing, breaking;
  59 extern int executing_list;
  60 extern int comsub_ignore_return;
  61 extern int parse_and_execute_level, shell_initialized;
  62
  63 /* Non-zero after SIGINT. */
  64 volatile int interrupt_state = 0;
  65
  66 /* Non-zero after SIGWINCH */
  67 volatile int sigwinch_received = 0;
  68
  69 /* Set to the value of any terminating signal received. */
  70 volatile int terminating_signal = 0;
  71
  72 /* The environment at the top-level R-E loop.  We use this in
  73    the case of error return. */
  74 procenv_t top_level;
  75
  76 #if defined (JOB_CONTROL) || defined (HAVE_POSIX_SIGNALS)
  77 /* The signal masks that this shell runs with. */
  78 sigset_t top_level_mask;
  79 #endif /* JOB_CONTROL */
  80
  81 /* When non-zero, we throw_to_top_level (). */
  82 int interrupt_immediately = 0;
  83
  84 /* When non-zero, we call the terminating signal handler immediately. */
  85 int terminate_immediately = 0;
  86
  87 #if defined (SIGWINCH)
  88 static SigHandler *old_winch = (SigHandler *)SIG_DFL;
  89 #endif
  90
  91 static void initialize_shell_signals __P((void));
  92
  93 void
  94 initialize_signals (reinit)
  95      int reinit;
  96 {
  97   initialize_shell_signals ();
  98   initialize_job_signals ();
  99 #if !defined (HAVE_SYS_SIGLIST) && !defined (HAVE_UNDER_SYS_SIGLIST) && !defined (HAVE_STRSIGNAL)
 100   if (reinit == 0)
 101     initialize_siglist ();
 102 #endif /* !HAVE_SYS_SIGLIST && !HAVE_UNDER_SYS_SIGLIST && !HAVE_STRSIGNAL */
 103 }
 104
 105 /* A structure describing a signal that terminates the shell if not
 106    caught.  The orig_handler member is present so children can reset
 107    these signals back to their original handlers. */
 108 struct termsig {
 109      int signum;
 110      SigHandler *orig_handler;
 111      int orig_flags;
 112 };
 113
 114 #define NULL_HANDLER (SigHandler *)SIG_DFL
 115
 116 /* The list of signals that would terminate the shell if not caught.
 117    We catch them, but just so that we can write the history file,
 118    and so forth. */
 119 static struct termsig terminating_signals[] = {
 120 #ifdef SIGHUP
 121 {  SIGHUP, NULL_HANDLER, 0 },
 122 #endif
 123
 124 #ifdef SIGINT
 125 {  SIGINT, NULL_HANDLER, 0 },
 126 #endif
 127
 128 #ifdef SIGILL
 129 {  SIGILL, NULL_HANDLER, 0 },
 130 #endif
 131
 132 #ifdef SIGTRAP
 133 {  SIGTRAP, NULL_HANDLER, 0 },
 134 #endif
 135
 136 #ifdef SIGIOT
 137 {  SIGIOT, NULL_HANDLER, 0 },
 138 #endif
 139
 140 #ifdef SIGDANGER
 141 {  SIGDANGER, NULL_HANDLER, 0 },
 142 #endif
 143
 144 #ifdef SIGEMT
 145 {  SIGEMT, NULL_HANDLER, 0 },
 146 #endif
 147
 148 #ifdef SIGFPE
 149 {  SIGFPE, NULL_HANDLER, 0 },
 150 #endif
 151
 152 #ifdef SIGBUS
 153 {  SIGBUS, NULL_HANDLER, 0 },
 154 #endif
 155
 156 #ifdef SIGSEGV
 157 {  SIGSEGV, NULL_HANDLER, 0 },
 158 #endif
 159
 160 #ifdef SIGSYS
 161 {  SIGSYS, NULL_HANDLER, 0 },
 162 #endif
 163
 164 #ifdef SIGPIPE
 165 {  SIGPIPE, NULL_HANDLER, 0 },
 166 #endif
 167
 168 #ifdef SIGALRM
 169 {  SIGALRM, NULL_HANDLER, 0 },
 170 #endif
 171
 172 #ifdef SIGTERM
 173 {  SIGTERM, NULL_HANDLER, 0 },
 174 #endif
 175
 176 #ifdef SIGXCPU
 177 {  SIGXCPU, NULL_HANDLER, 0 },
 178 #endif
 179
 180 #ifdef SIGXFSZ
 181 {  SIGXFSZ, NULL_HANDLER, 0 },
 182 #endif
 183
 184 #ifdef SIGVTALRM
 185 {  SIGVTALRM, NULL_HANDLER, 0 },
 186 #endif
 187
 188 #if 0
 189 #ifdef SIGPROF
 190 {  SIGPROF, NULL_HANDLER, 0 },
 191 #endif
 192 #endif
 193
 194 #ifdef SIGLOST
 195 {  SIGLOST, NULL_HANDLER, 0 },
 196 #endif
 197
 198 #ifdef SIGUSR1
 199 {  SIGUSR1, NULL_HANDLER, 0 },
 200 #endif
 201
 202 #ifdef SIGUSR2
 203 {  SIGUSR2, NULL_HANDLER, 0 },
 204 #endif
 205 };
 206
 207 #define TERMSIGS_LENGTH (sizeof (terminating_signals) / sizeof (struct termsig))
 208
 209 #define XSIG(x) (terminating_signals[x].signum)
 210 #define XHANDLER(x) (terminating_signals[x].orig_handler)
 211 #define XSAFLAGS(x) (terminating_signals[x].orig_flags)
 212
 213 static int termsigs_initialized = 0;
 214
 215 /* Initialize signals that will terminate the shell to do some
 216    unwind protection.  For non-interactive shells, we only call
 217    this when a trap is defined for EXIT (0). */
 218 void
 219 initialize_terminating_signals ()
 220 {
 221   register int i;
 222 #if defined (HAVE_POSIX_SIGNALS)
 223   struct sigaction act, oact;
 224 #endif
 225
 226   if (termsigs_initialized)
 227     return;
 228
 229   /* The following code is to avoid an expensive call to
 230      set_signal_handler () for each terminating_signals.  Fortunately,
 231      this is possible in Posix.  Unfortunately, we have to call signal ()
 232      on non-Posix systems for each signal in terminating_signals. */
 233 #if defined (HAVE_POSIX_SIGNALS)
 234   act.sa_handler = termsig_sighandler;
 235   act.sa_flags = 0;
 236   sigemptyset (&act.sa_mask);
 237   sigemptyset (&oact.sa_mask);
 238   for (i = 0; i < TERMSIGS_LENGTH; i++)
 239     sigaddset (&act.sa_mask, XSIG (i));
 240   for (i = 0; i < TERMSIGS_LENGTH; i++)
 241     {
 242       /* If we've already trapped it, don't do anything. */
 243       if (signal_is_trapped (XSIG (i)))
 244         continue;
 245
 246       sigaction (XSIG (i), &act, &oact);
 247       XHANDLER(i) = oact.sa_handler;
 248       XSAFLAGS(i) = oact.sa_flags;
 249       /* Don't do anything with signals that are ignored at shell entry
 250          if the shell is not interactive. */
 251       if (!interactive_shell && XHANDLER (i) == SIG_IGN)
 252         {
 253           sigaction (XSIG (i), &oact, &act);
 254           set_signal_ignored (XSIG (i));
 255         }
 256 #if defined (SIGPROF) && !defined (_MINIX)
 257       if (XSIG (i) == SIGPROF && XHANDLER (i) != SIG_DFL && XHANDLER (i) != SIG_IGN)
 258         sigaction (XSIG (i), &oact, (struct sigaction *)NULL);
 259 #endif /* SIGPROF && !_MINIX */
 260     }
 261
 262 #else /* !HAVE_POSIX_SIGNALS */
 263
 264   for (i = 0; i < TERMSIGS_LENGTH; i++)
 265     {
 266       /* If we've already trapped it, don't do anything. */
 267       if (signal_is_trapped (XSIG (i)))
 268         continue;
 269
 270       XHANDLER(i) = signal (XSIG (i), termsig_sighandler);
 271       XSAFLAGS(i) = 0;
 272       /* Don't do anything with signals that are ignored at shell entry
 273          if the shell is not interactive. */
 274       if (!interactive_shell && XHANDLER (i) == SIG_IGN)
 275         {
 276           signal (XSIG (i), SIG_IGN);
 277           set_signal_ignored (XSIG (i));
 278         }
 279 #ifdef SIGPROF
 280       if (XSIG (i) == SIGPROF && XHANDLER (i) != SIG_DFL && XHANDLER (i) != SIG_IGN)
 281         signal (XSIG (i), XHANDLER (i));
 282 #endif
 283     }
 284
 285 #endif /* !HAVE_POSIX_SIGNALS */
 286
 287   termsigs_initialized = 1;
 288 }
 289
 290 static void
 291 initialize_shell_signals ()
 292 {
 293   if (interactive)
 294     initialize_terminating_signals ();
 295
 296 #if defined (JOB_CONTROL) || defined (HAVE_POSIX_SIGNALS)
 297   /* All shells use the signal mask they inherit, and pass it along
 298      to child processes.  Children will never block SIGCHLD, though. */
 299   sigemptyset (&top_level_mask);
 300   sigprocmask (SIG_BLOCK, (sigset_t *)NULL, &top_level_mask);
 301 #  if defined (SIGCHLD)
 302   sigdelset (&top_level_mask, SIGCHLD);
 303 #  endif
 304 #endif /* JOB_CONTROL || HAVE_POSIX_SIGNALS */
 305
 306   /* And, some signals that are specifically ignored by the shell. */
 307   set_signal_handler (SIGQUIT, SIG_IGN);
 308
 309   if (interactive)
 310     {
 311       set_signal_handler (SIGINT, sigint_sighandler);
 312       set_signal_handler (SIGTERM, SIG_IGN);
 313       set_sigwinch_handler ();
 314     }
 315 }
 316
 317 void
 318 reset_terminating_signals ()
 319 {
 320   register int i;
 321 #if defined (HAVE_POSIX_SIGNALS)
 322   struct sigaction act;
 323 #endif
 324
 325   if (termsigs_initialized == 0)
 326     return;
 327
 328 #if defined (HAVE_POSIX_SIGNALS)
 329   act.sa_flags = 0;
 330   sigemptyset (&act.sa_mask);
 331   for (i = 0; i < TERMSIGS_LENGTH; i++)
 332     {
 333       /* Skip a signal if it's trapped or handled specially, because the
 334          trap code will restore the correct value. */
 335       if (signal_is_trapped (XSIG (i)) || signal_is_special (XSIG (i)))
 336         continue;
 337
 338       act.sa_handler = XHANDLER (i);
 339       act.sa_flags = XSAFLAGS (i);
 340       sigaction (XSIG (i), &act, (struct sigaction *) NULL);
 341     }
 342 #else /* !HAVE_POSIX_SIGNALS */
 343   for (i = 0; i < TERMSIGS_LENGTH; i++)
 344     {
 345       if (signal_is_trapped (XSIG (i)) || signal_is_special (XSIG (i)))
 346         continue;
 347
 348       signal (XSIG (i), XHANDLER (i));
 349     }
 350 #endif /* !HAVE_POSIX_SIGNALS */
 351 }
 352 #undef XSIG
 353 #undef XHANDLER
 354
 355 /* Run some of the cleanups that should be performed when we run
 356    jump_to_top_level from a builtin command context.  XXX - might want to
 357    also call reset_parser here. */
 358 void
 359 top_level_cleanup ()
 360 {
 361   /* Clean up string parser environment. */
 362   while (parse_and_execute_level)
 363     parse_and_execute_cleanup ();
 364
 365 #if defined (PROCESS_SUBSTITUTION)
 366   unlink_fifo_list ();
 367 #endif /* PROCESS_SUBSTITUTION */
 368
 369   run_unwind_protects ();
 370   loop_level = continuing = breaking = 0;
 371   executing_list = comsub_ignore_return = return_catch_flag = 0;
 372 }
 373
 374 /* What to do when we've been interrupted, and it is safe to handle it. */
 375 void
 376 throw_to_top_level ()
 377 {
 378   int print_newline = 0;
 379
 380   if (interrupt_state)
 381     {
 382       print_newline = 1;
 383       DELINTERRUPT;
 384     }
 385
 386   if (interrupt_state)
 387     return;
 388
 389   last_command_exit_signal = (last_command_exit_value > 128) ?
 390                                 (last_command_exit_value - 128) : 0;
 391   last_command_exit_value |= 128;
 392
 393   /* Run any traps set on SIGINT. */
 394   run_interrupt_trap ();
 395
 396   /* Clean up string parser environment. */
 397   while (parse_and_execute_level)
 398     parse_and_execute_cleanup ();
 399
 400 #if defined (JOB_CONTROL)
 401   give_terminal_to (shell_pgrp, 0);
 402 #endif /* JOB_CONTROL */
 403
 404 #if defined (JOB_CONTROL) || defined (HAVE_POSIX_SIGNALS)
 405   /* This should not be necessary on systems using sigsetjmp/siglongjmp. */
 406   sigprocmask (SIG_SETMASK, &top_level_mask, (sigset_t *)NULL);
 407 #endif
 408
 409   reset_parser ();
 410
 411 #if defined (READLINE)
 412   if (interactive)
 413     bashline_reset ();
 414 #endif /* READLINE */
 415
 416 #if defined (PROCESS_SUBSTITUTION)
 417   unlink_fifo_list ();
 418 #endif /* PROCESS_SUBSTITUTION */
 419
 420   run_unwind_protects ();
 421   loop_level = continuing = breaking = 0;
 422   executing_list = comsub_ignore_return = return_catch_flag = 0;
 423
 424   if (interactive && print_newline)
 425     {
 426       fflush (stdout);
 427       fprintf (stderr, "\n");
 428       fflush (stderr);
 429     }
 430
 431   /* An interrupted `wait' command in a script does not exit the script. */
 432   if (interactive || (interactive_shell && !shell_initialized) ||
 433       (print_newline && signal_is_trapped (SIGINT)))
 434     jump_to_top_level (DISCARD);
 435   else
 436     jump_to_top_level (EXITPROG);
 437 }
 438
 439 /* This is just here to isolate the longjmp calls. */
 440 void
 441 jump_to_top_level (value)
 442      int value;
 443 {
 444   longjmp (top_level, value);
 445 }
 446
 447 sighandler
 448 termsig_sighandler (sig)
 449      int sig;
 450 {
 451   /* If we get called twice with the same signal before handling it,
 452      terminate right away. */
 453   if (
 454 #ifdef SIGHUP
 455     sig != SIGHUP &&
 456 #endif
 457 #ifdef SIGINT
 458     sig != SIGINT &&
 459 #endif
 460 #ifdef SIGDANGER
 461     sig != SIGDANGER &&
 462 #endif
 463 #ifdef SIGPIPE
 464     sig != SIGPIPE &&
 465 #endif
 466 #ifdef SIGALRM
 467     sig != SIGALRM &&
 468 #endif
 469 #ifdef SIGTERM
 470     sig != SIGTERM &&
 471 #endif
 472 #ifdef SIGXCPU
 473     sig != SIGXCPU &&
 474 #endif
 475 #ifdef SIGXFSZ
 476     sig != SIGXFSZ &&
 477 #endif
 478 #ifdef SIGVTALRM
 479     sig != SIGVTALRM &&
 480 #endif
 481 #ifdef SIGLOST
 482     sig != SIGLOST &&
 483 #endif
 484 #ifdef SIGUSR1
 485     sig != SIGUSR1 &&
 486 #endif
 487 #ifdef SIGUSR2
 488    sig != SIGUSR2 &&
 489 #endif
 490    sig == terminating_signal)
 491     terminate_immediately = 1;
 492
 493   terminating_signal = sig;
 494
 495   /* XXX - should this also trigger when interrupt_immediately is set? */
 496   if (terminate_immediately)
 497     {
 498       terminate_immediately = 0;
 499       termsig_handler (sig);
 500     }
 501
 502   SIGRETURN (0);
 503 }
 504
 505 void
 506 termsig_handler (sig)
 507      int sig;
 508 {
 509   static int handling_termsig = 0;
 510
 511   /* Simple semaphore to keep this function from being executed multiple
 512      times.  Since we no longer are running as a signal handler, we don't
 513      block multiple occurrences of the terminating signals while running. */
 514   if (handling_termsig)
 515     return;
 516   handling_termsig = 1;
 517   terminating_signal = 0;       /* keep macro from re-testing true. */
 518
 519   /* I don't believe this condition ever tests true. */
 520   if (sig == SIGINT && signal_is_trapped (SIGINT))
 521     run_interrupt_trap ();
 522
 523 #if defined (HISTORY)
 524   if (interactive_shell && sig != SIGABRT)
 525     maybe_save_shell_history ();
 526 #endif /* HISTORY */
 527
 528 #if defined (JOB_CONTROL)
 529   if (interactive && sig == SIGHUP)
 530     hangup_all_jobs ();
 531   end_job_control ();
 532 #endif /* JOB_CONTROL */
 533
 534 #if defined (PROCESS_SUBSTITUTION)
 535   unlink_fifo_list ();
 536 #endif /* PROCESS_SUBSTITUTION */
 537
 538   /* Reset execution context */
 539   loop_level = continuing = breaking = 0;
 540   executing_list = comsub_ignore_return = return_catch_flag = 0;
 541
 542   run_exit_trap ();
 543   set_signal_handler (sig, SIG_DFL);
 544   kill (getpid (), sig);
 545 }
 546
 547 /* What we really do when SIGINT occurs. */
 548 sighandler
 549 sigint_sighandler (sig)
 550      int sig;
 551 {
 552 #if defined (MUST_REINSTALL_SIGHANDLERS)
 553   signal (sig, sigint_sighandler);
 554 #endif
 555
 556   /* interrupt_state needs to be set for the stack of interrupts to work
 557      right.  Should it be set unconditionally? */
 558   if (interrupt_state == 0)
 559     ADDINTERRUPT;
 560
 561   if (interrupt_immediately)
 562     {
 563       interrupt_immediately = 0;
 564       throw_to_top_level ();
 565     }
 566
 567   SIGRETURN (0);
 568 }
 569
 570 #if defined (SIGWINCH)
 571 sighandler
 572 sigwinch_sighandler (sig)
 573      int sig;
 574 {
 575 #if defined (MUST_REINSTALL_SIGHANDLERS)
 576   set_signal_handler (SIGWINCH, sigwinch_sighandler);
 577 #endif /* MUST_REINSTALL_SIGHANDLERS */
 578   sigwinch_received = 1;
 579   SIGRETURN (0);
 580 }
 581 #endif /* SIGWINCH */
 582
 583 void
 584 set_sigwinch_handler ()
 585 {
 586 #if defined (SIGWINCH)
 587  old_winch = set_signal_handler (SIGWINCH, sigwinch_sighandler);
 588 #endif
 589 }
 590
 591 void
 592 unset_sigwinch_handler ()
 593 {
 594 #if defined (SIGWINCH)
 595   set_signal_handler (SIGWINCH, old_winch);
 596 #endif
 597 }
 598
 599 /* Signal functions used by the rest of the code. */
 600 #if !defined (HAVE_POSIX_SIGNALS)
 601
 602 #if defined (JOB_CONTROL)
 603 /* Perform OPERATION on NEWSET, perhaps leaving information in OLDSET. */
 604 sigprocmask (operation, newset, oldset)
 605      int operation, *newset, *oldset;
 606 {
 607   int old, new;
 608
 609   if (newset)
 610     new = *newset;
 611   else
 612     new = 0;
 613
 614   switch (operation)
 615     {
 616     case SIG_BLOCK:
 617       old = sigblock (new);
 618       break;
 619
 620     case SIG_SETMASK:
 621       sigsetmask (new);
 622       break;
 623
 624     default:
 625       internal_error (_("sigprocmask: %d: invalid operation"), operation);
 626     }
 627
 628   if (oldset)
 629     *oldset = old;
 630 }
 631 #endif /* JOB_CONTROL */
 632
 633 #else
 634
 635 #if !defined (SA_INTERRUPT)
 636 #  define SA_INTERRUPT 0
 637 #endif
 638
 639 #if !defined (SA_RESTART)
 640 #  define SA_RESTART 0
 641 #endif
 642
 643 SigHandler *
 644 set_signal_handler (sig, handler)
 645      int sig;
 646      SigHandler *handler;
 647 {
 648   struct sigaction act, oact;
 649
 650   act.sa_handler = handler;
 651   act.sa_flags = 0;
 652 #if 0
 653   if (sig == SIGALRM)
 654     act.sa_flags |= SA_INTERRUPT;       /* XXX */
 655   else
 656     act.sa_flags |= SA_RESTART;         /* XXX */
 657 #endif
 658   sigemptyset (&act.sa_mask);
 659   sigemptyset (&oact.sa_mask);
 660   sigaction (sig, &act, &oact);
 661   return (oact.sa_handler);
 662 }
 663 #endif /* HAVE_POSIX_SIGNALS */