sig.c

   1 /* sig.c - interface for shell signal handlers and signal initialization. */
   2
   3 /* Copyright (C) 1994 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 it under
   8    the terms of the GNU General Public License as published by the Free
   9    Software Foundation; either version 2, or (at your option) any later
  10    version.
  11
  12    Bash is distributed in the hope that it will be useful, but WITHOUT ANY
  13    WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15    for more details.
  16
  17    You should have received a copy of the GNU General Public License along
  18    with Bash; see the file COPYING.  If not, write to the Free Software
  19    Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
  20
  21 #include "config.h"
  22
  23 #include "bashtypes.h"
  24
  25 #if defined (HAVE_UNISTD_H)
  26 #  include <unistd.h>
  27 #endif
  28
  29 #include <stdio.h>
  30 #include <signal.h>
  31
  32 #include "shell.h"
  33 #if defined (JOB_CONTROL)
  34 #include "jobs.h"
  35 #endif /* JOB_CONTROL */
  36 #include "siglist.h"
  37 #include "sig.h"
  38 #include "trap.h"
  39
  40 #include "builtins/common.h"
  41
  42 #if defined (READLINE)
  43 #  include "bashline.h"
  44 #endif
  45
  46 #if defined (HISTORY)
  47 #  include "bashhist.h"
  48 #endif
  49
  50 extern int last_command_exit_value;
  51 extern int return_catch_flag;
  52 extern int loop_level, continuing, breaking;
  53 extern int parse_and_execute_level, shell_initialized;
  54 extern int interactive, interactive_shell, login_shell, startup_state;
  55
  56 /* Non-zero after SIGINT. */
  57 int interrupt_state;
  58
  59 /* The environment at the top-level R-E loop.  We use this in
  60    the case of error return. */
  61 procenv_t top_level;
  62
  63 #if defined (JOB_CONTROL) || defined (HAVE_POSIX_SIGNALS)
  64 /* The signal masks that this shell runs with. */
  65 sigset_t top_level_mask;
  66 #endif /* JOB_CONTROL */
  67
  68 /* When non-zero, we throw_to_top_level (). */
  69 int interrupt_immediately = 0;
  70
  71 static void initialize_terminating_signals ();
  72
  73 void
  74 initialize_signals ()
  75 {
  76   initialize_terminating_signals ();
  77   initialize_job_signals ();
  78 #if !defined (HAVE_SYS_SIGLIST) && !defined (HAVE_STRSIGNAL)
  79   initialize_siglist ();
  80 #endif
  81 }
  82
  83 void
  84 reinitialize_signals ()
  85 {
  86   initialize_terminating_signals ();
  87   initialize_job_signals ();
  88 }
  89
  90 /* A structure describing a signal that terminates the shell if not
  91    caught.  The orig_handler member is present so children can reset
  92    these signals back to their original handlers. */
  93 struct termsig {
  94      int signum;
  95      SigHandler *orig_handler;
  96 };
  97
  98 #define NULL_HANDLER (SigHandler *)SIG_DFL
  99
 100 /* The list of signals that would terminate the shell if not caught.
 101    We catch them, but just so that we can write the history file,
 102    and so forth. */
 103 static struct termsig terminating_signals[] = {
 104 #ifdef SIGHUP
 105   SIGHUP, NULL_HANDLER,
 106 #endif
 107
 108 #ifdef SIGINT
 109   SIGINT, NULL_HANDLER,
 110 #endif
 111
 112 #ifdef SIGILL
 113   SIGILL, NULL_HANDLER,
 114 #endif
 115
 116 #ifdef SIGTRAP
 117   SIGTRAP, NULL_HANDLER,
 118 #endif
 119
 120 #ifdef SIGIOT
 121   SIGIOT, NULL_HANDLER,
 122 #endif
 123
 124 #ifdef SIGDANGER
 125   SIGDANGER, NULL_HANDLER,
 126 #endif
 127
 128 #ifdef SIGEMT
 129   SIGEMT, NULL_HANDLER,
 130 #endif
 131
 132 #ifdef SIGFPE
 133   SIGFPE, NULL_HANDLER,
 134 #endif
 135
 136 #ifdef SIGBUS
 137   SIGBUS, NULL_HANDLER,
 138 #endif
 139
 140 #ifdef SIGSEGV
 141   SIGSEGV, NULL_HANDLER,
 142 #endif
 143
 144 #ifdef SIGSYS
 145   SIGSYS, NULL_HANDLER,
 146 #endif
 147
 148 #ifdef SIGPIPE
 149   SIGPIPE, NULL_HANDLER,
 150 #endif
 151
 152 #ifdef SIGALRM
 153   SIGALRM, NULL_HANDLER,
 154 #endif
 155
 156 #ifdef SIGTERM
 157   SIGTERM, NULL_HANDLER,
 158 #endif
 159
 160 #ifdef SIGXCPU
 161   SIGXCPU, NULL_HANDLER,
 162 #endif
 163
 164 #ifdef SIGXFSZ
 165   SIGXFSZ, NULL_HANDLER,
 166 #endif
 167
 168 #ifdef SIGVTALRM
 169   SIGVTALRM, NULL_HANDLER,
 170 #endif
 171
 172 #ifdef SIGPROF
 173   SIGPROF, NULL_HANDLER,
 174 #endif
 175
 176 #ifdef SIGLOST
 177   SIGLOST, NULL_HANDLER,
 178 #endif
 179
 180 #ifdef SIGUSR1
 181   SIGUSR1, NULL_HANDLER,
 182 #endif
 183
 184 #ifdef SIGUSR2
 185   SIGUSR2, NULL_HANDLER,
 186 #endif
 187 };
 188
 189 #define TERMSIGS_LENGTH (sizeof (terminating_signals) / sizeof (struct termsig))
 190
 191 #define XSIG(x) (terminating_signals[x].signum)
 192 #define XHANDLER(x) (terminating_signals[x].orig_handler)
 193
 194 /* Initialize signals that will terminate the shell to do some
 195    unwind protection. */
 196 static void
 197 initialize_terminating_signals ()
 198 {
 199   register int i;
 200
 201   /* The following code is to avoid an expensive call to
 202      set_signal_handler () for each terminating_signals.  Fortunately,
 203      this is possible in Posix.  Unfortunately, we have to call signal ()
 204      on non-Posix systems for each signal in terminating_signals. */
 205 #if defined (HAVE_POSIX_SIGNALS)
 206   struct sigaction act, oact;
 207
 208   act.sa_handler = termination_unwind_protect;
 209   act.sa_flags = 0;
 210   sigemptyset (&act.sa_mask);
 211   sigemptyset (&oact.sa_mask);
 212   for (i = 0; i < TERMSIGS_LENGTH; i++)
 213     sigaddset (&act.sa_mask, XSIG (i));
 214   for (i = 0; i < TERMSIGS_LENGTH; i++)
 215     {
 216       sigaction (XSIG (i), &act, &oact);
 217       terminating_signals[i].orig_handler = oact.sa_handler;
 218       /* Don't do anything with signals that are ignored at shell entry
 219          if the shell is not interactive. */
 220       if (!interactive_shell && oact.sa_handler == SIG_IGN)
 221         {
 222           sigaction (XSIG (i), &oact, &act);
 223           set_signal_ignored (XSIG (i));
 224         }
 225     }
 226
 227 #else /* !HAVE_POSIX_SIGNALS */
 228
 229   for (i = 0; i < TERMSIGS_LENGTH; i++)
 230     {
 231       terminating_signals[i].orig_handler =
 232         signal (XSIG (i), termination_unwind_protect);
 233       /* Don't do anything with signals that are ignored at shell entry
 234          if the shell is not interactive. */
 235       if (!interactive_shell && terminating_signals[i].orig_handler == SIG_IGN)
 236         {
 237           signal (XSIG (i), SIG_IGN);
 238           set_signal_ignored (XSIG (i));
 239         }
 240     }
 241
 242 #endif /* !HAVE_POSIX_SIGNALS */
 243
 244 #if defined (JOB_CONTROL) || defined (HAVE_POSIX_SIGNALS)
 245   /* All shells use the signal mask they inherit, and pass it along
 246      to child processes.  Children will never block SIGCHLD, though. */
 247   sigemptyset (&top_level_mask);
 248   sigprocmask (SIG_BLOCK, (sigset_t *)NULL, &top_level_mask);
 249   sigdelset (&top_level_mask, SIGCHLD);
 250 #endif /* JOB_CONTROL || HAVE_POSIX_SIGNALS */
 251
 252   /* And, some signals that are specifically ignored by the shell. */
 253   set_signal_handler (SIGQUIT, SIG_IGN);
 254
 255   if (interactive)
 256     {
 257       set_signal_handler (SIGINT, sigint_sighandler);
 258       set_signal_handler (SIGTERM, SIG_IGN);
 259     }
 260 }
 261
 262 void
 263 reset_terminating_signals ()
 264 {
 265   register int i;
 266
 267 #if defined (HAVE_POSIX_SIGNALS)
 268   struct sigaction act;
 269
 270   act.sa_flags = 0;
 271   sigemptyset (&act.sa_mask);
 272   for (i = 0; i < TERMSIGS_LENGTH; i++)
 273     {
 274       /* Skip a signal if it's trapped or handled specially, because the
 275          trap code will restore the correct value. */
 276       if (signal_is_trapped (XSIG (i)) || signal_is_special (XSIG (i)))
 277         continue;
 278
 279       act.sa_handler = XHANDLER (i);
 280       sigaction (XSIG (i), &act, (struct sigaction *) NULL);
 281     }
 282 #else /* !HAVE_POSIX_SIGNALS */
 283   for (i = 0; i < TERMSIGS_LENGTH; i++)
 284     {
 285       if (signal_is_trapped (XSIG (i)) || signal_is_special (XSIG (i)))
 286         continue;
 287
 288       signal (XSIG (i), XHANDLER (i));
 289     }
 290 #endif /* !HAVE_POSIX_SIGNALS */
 291 }
 292 #undef XSIG
 293 #undef XHANDLER
 294
 295 /* What to do when we've been interrupted, and it is safe to handle it. */
 296 void
 297 throw_to_top_level ()
 298 {
 299   int print_newline = 0;
 300
 301   if (interrupt_state)
 302     {
 303       print_newline = 1;
 304       DELINTERRUPT;
 305     }
 306
 307   if (interrupt_state)
 308     return;
 309
 310   last_command_exit_value |= 128;
 311
 312   /* Run any traps set on SIGINT. */
 313   run_interrupt_trap ();
 314
 315   /* Cleanup string parser environment. */
 316   while (parse_and_execute_level)
 317     parse_and_execute_cleanup ();
 318
 319 #if defined (JOB_CONTROL)
 320   give_terminal_to (shell_pgrp);
 321 #endif /* JOB_CONTROL */
 322
 323 #if defined (JOB_CONTROL) || defined (HAVE_POSIX_SIGNALS)
 324   /* This should not be necessary on systems using sigsetjmp/siglongjmp. */
 325   sigprocmask (SIG_SETMASK, &top_level_mask, (sigset_t *)NULL);
 326 #endif
 327
 328   reset_parser ();
 329
 330 #if defined (READLINE)
 331   if (interactive)
 332     bashline_reinitialize ();
 333 #endif /* READLINE */
 334
 335 #if defined (PROCESS_SUBSTITUTION)
 336   unlink_fifo_list ();
 337 #endif /* PROCESS_SUBSTITUTION */
 338
 339   run_unwind_protects ();
 340   loop_level = continuing = breaking = 0;
 341   return_catch_flag = 0;
 342
 343   if (interactive && print_newline)
 344     {
 345       fflush (stdout);
 346       fprintf (stderr, "\n");
 347       fflush (stderr);
 348     }
 349
 350   /* An interrupted `wait' command in a script does not exit the script. */
 351   if (interactive || (interactive_shell && !shell_initialized) ||
 352       (print_newline && signal_is_trapped (SIGINT)))
 353     jump_to_top_level (DISCARD);
 354   else
 355     jump_to_top_level (EXITPROG);
 356 }
 357
 358 /* This is just here to isolate the longjmp calls. */
 359 void
 360 jump_to_top_level (value)
 361      int value;
 362 {
 363   longjmp (top_level, value);
 364 }
 365
 366 sighandler
 367 termination_unwind_protect (sig)
 368      int sig;
 369 {
 370   if (sig == SIGINT && signal_is_trapped (SIGINT))
 371     run_interrupt_trap ();
 372
 373 #if defined (HISTORY)
 374   if (interactive_shell && sig != SIGABRT)
 375     maybe_save_shell_history ();
 376 #endif /* HISTORY */
 377
 378 #if defined (JOB_CONTROL)
 379   if (interactive && sig == SIGHUP)
 380     hangup_all_jobs ();
 381   end_job_control ();
 382 #endif /* JOB_CONTROL */
 383
 384 #if defined (PROCESS_SUBSTITUTION)
 385   unlink_fifo_list ();
 386 #endif /* PROCESS_SUBSTITUTION */
 387
 388   run_exit_trap ();
 389   set_signal_handler (sig, SIG_DFL);
 390   kill (getpid (), sig);
 391
 392   SIGRETURN (0);
 393 }
 394
 395 /* What we really do when SIGINT occurs. */
 396 sighandler
 397 sigint_sighandler (sig)
 398      int sig;
 399 {
 400 #if defined (MUST_REINSTALL_SIGHANDLERS)
 401   signal (sig, sigint_sighandler);
 402 #endif
 403
 404   /* interrupt_state needs to be set for the stack of interrupts to work
 405      right.  Should it be set unconditionally? */
 406   if (interrupt_state == 0)
 407     ADDINTERRUPT;
 408
 409   if (interrupt_immediately)
 410     {
 411       interrupt_immediately = 0;
 412       throw_to_top_level ();
 413     }
 414
 415   SIGRETURN (0);
 416 }
 417
 418 /* Signal functions used by the rest of the code. */
 419 #if !defined (HAVE_POSIX_SIGNALS)
 420
 421 #if defined (JOB_CONTROL)
 422 /* Perform OPERATION on NEWSET, perhaps leaving information in OLDSET. */
 423 sigprocmask (operation, newset, oldset)
 424      int operation, *newset, *oldset;
 425 {
 426   int old, new;
 427
 428   if (newset)
 429     new = *newset;
 430   else
 431     new = 0;
 432
 433   switch (operation)
 434     {
 435     case SIG_BLOCK:
 436       old = sigblock (new);
 437       break;
 438
 439     case SIG_SETMASK:
 440       sigsetmask (new);
 441       break;
 442
 443     default:
 444       internal_error ("Bad code in sig.c: sigprocmask");
 445     }
 446
 447   if (oldset)
 448     *oldset = old;
 449 }
 450 #endif /* JOB_CONTROL */
 451
 452 #else
 453
 454 #if !defined (SA_INTERRUPT)
 455 #  define SA_INTERRUPT 0
 456 #endif
 457
 458 #if !defined (SA_RESTART)
 459 #  define SA_RESTART 0
 460 #endif
 461
 462 SigHandler *
 463 set_signal_handler (sig, handler)
 464      int sig;
 465      SigHandler *handler;
 466 {
 467   struct sigaction act, oact;
 468
 469   act.sa_handler = handler;
 470   act.sa_flags = 0;
 471 #if 0
 472   if (sig == SIGALRM)
 473     act.sa_flags |= SA_INTERRUPT;       /* XXX */
 474   else
 475     act.sa_flags |= SA_RESTART;         /* XXX */
 476 #endif
 477   sigemptyset (&act.sa_mask);
 478   sigemptyset (&oact.sa_mask);
 479   sigaction (sig, &act, &oact);
 480   return (oact.sa_handler);
 481 }
 482 #endif /* HAVE_POSIX_SIGNALS */