bin/sh/trap.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Kenneth Almquist.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 4. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #ifndef lint
  34 #if 0
  35 static char sccsid[] = "@(#)trap.c      8.5 (Berkeley) 6/5/95";
  36 #endif
  37 #endif /* not lint */
  38 #include <sys/cdefs.h>
  39 __FBSDID("$FreeBSD$");
  40
  41 #include <signal.h>
  42 #include <unistd.h>
  43 #include <stdlib.h>
  44
  45 #include "shell.h"
  46 #include "main.h"
  47 #include "nodes.h"      /* for other headers */
  48 #include "eval.h"
  49 #include "jobs.h"
  50 #include "show.h"
  51 #include "options.h"
  52 #include "syntax.h"
  53 #include "output.h"
  54 #include "memalloc.h"
  55 #include "error.h"
  56 #include "trap.h"
  57 #include "mystring.h"
  58 #include "builtins.h"
  59 #include "myhistedit.h"
  60
  61
  62 /*
  63  * Sigmode records the current value of the signal handlers for the various
  64  * modes.  A value of zero means that the current handler is not known.
  65  * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
  66  */
  67
  68 #define S_DFL 1                 /* default signal handling (SIG_DFL) */
  69 #define S_CATCH 2               /* signal is caught */
  70 #define S_IGN 3                 /* signal is ignored (SIG_IGN) */
  71 #define S_HARD_IGN 4            /* signal is ignored permanently */
  72 #define S_RESET 5               /* temporary - to reset a hard ignored sig */
  73
  74
  75 static char sigmode[NSIG];      /* current value of signal */
  76 volatile sig_atomic_t pendingsig;       /* indicates some signal received */
  77 volatile sig_atomic_t pendingsig_waitcmd;       /* indicates SIGINT/SIGQUIT received */
  78 int in_dotrap;                  /* do we execute in a trap handler? */
  79 static char *volatile trap[NSIG];       /* trap handler commands */
  80 static volatile sig_atomic_t gotsig[NSIG];
  81                                 /* indicates specified signal received */
  82 static int ignore_sigchld;      /* Used while handling SIGCHLD traps. */
  83 volatile sig_atomic_t gotwinch;
  84 static int last_trapsig;
  85
  86 static int exiting;             /* exitshell() has been called */
  87 static int exiting_exitstatus;  /* value passed to exitshell() */
  88
  89 static int getsigaction(int, sig_t *);
  90
  91
  92 /*
  93  * Map a string to a signal number.
  94  *
  95  * Note: the signal number may exceed NSIG.
  96  */
  97 static int
  98 sigstring_to_signum(char *sig)
  99 {
 100
 101         if (is_number(sig)) {
 102                 int signo;
 103
 104                 signo = atoi(sig);
 105                 return ((signo >= 0 && signo < NSIG) ? signo : (-1));
 106         } else if (strcasecmp(sig, "EXIT") == 0) {
 107                 return (0);
 108         } else {
 109                 int n;
 110
 111                 if (strncasecmp(sig, "SIG", 3) == 0)
 112                         sig += 3;
 113                 for (n = 1; n < sys_nsig; n++)
 114                         if (sys_signame[n] &&
 115                             strcasecmp(sys_signame[n], sig) == 0)
 116                                 return (n);
 117         }
 118         return (-1);
 119 }
 120
 121
 122 /*
 123  * Print a list of valid signal names.
 124  */
 125 static void
 126 printsignals(void)
 127 {
 128         int n, outlen;
 129
 130         outlen = 0;
 131         for (n = 1; n < sys_nsig; n++) {
 132                 if (sys_signame[n]) {
 133                         out1fmt("%s", sys_signame[n]);
 134                         outlen += strlen(sys_signame[n]);
 135                 } else {
 136                         out1fmt("%d", n);
 137                         outlen += 3;    /* good enough */
 138                 }
 139                 ++outlen;
 140                 if (outlen > 71 || n == sys_nsig - 1) {
 141                         out1str("\n");
 142                         outlen = 0;
 143                 } else {
 144                         out1c(' ');
 145                 }
 146         }
 147 }
 148
 149
 150 /*
 151  * The trap builtin.
 152  */
 153 int
 154 trapcmd(int argc __unused, char **argv)
 155 {
 156         char *action;
 157         int signo;
 158         int errors = 0;
 159         int i;
 160
 161         while ((i = nextopt("l")) != '\0') {
 162                 switch (i) {
 163                 case 'l':
 164                         printsignals();
 165                         return (0);
 166                 }
 167         }
 168         argv = argptr;
 169
 170         if (*argv == NULL) {
 171                 for (signo = 0 ; signo < sys_nsig ; signo++) {
 172                         if (signo < NSIG && trap[signo] != NULL) {
 173                                 out1str("trap -- ");
 174                                 out1qstr(trap[signo]);
 175                                 if (signo == 0) {
 176                                         out1str(" EXIT\n");
 177                                 } else if (sys_signame[signo]) {
 178                                         out1fmt(" %s\n", sys_signame[signo]);
 179                                 } else {
 180                                         out1fmt(" %d\n", signo);
 181                                 }
 182                         }
 183                 }
 184                 return 0;
 185         }
 186         action = NULL;
 187         if (*argv && sigstring_to_signum(*argv) == -1) {
 188                 if (strcmp(*argv, "-") == 0)
 189                         argv++;
 190                 else {
 191                         action = *argv;
 192                         argv++;
 193                 }
 194         }
 195         for (; *argv; argv++) {
 196                 if ((signo = sigstring_to_signum(*argv)) == -1) {
 197                         warning("bad signal %s", *argv);
 198                         errors = 1;
 199                         continue;
 200                 }
 201                 INTOFF;
 202                 if (action)
 203                         action = savestr(action);
 204                 if (trap[signo])
 205                         ckfree(trap[signo]);
 206                 trap[signo] = action;
 207                 if (signo != 0)
 208                         setsignal(signo);
 209                 INTON;
 210         }
 211         return errors;
 212 }
 213
 214
 215 /*
 216  * Clear traps on a fork.
 217  */
 218 void
 219 clear_traps(void)
 220 {
 221         char *volatile *tp;
 222
 223         for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
 224                 if (*tp && **tp) {      /* trap not NULL or SIG_IGN */
 225                         INTOFF;
 226                         ckfree(*tp);
 227                         *tp = NULL;
 228                         if (tp != &trap[0])
 229                                 setsignal(tp - trap);
 230                         INTON;
 231                 }
 232         }
 233 }
 234
 235
 236 /*
 237  * Check if we have any traps enabled.
 238  */
 239 int
 240 have_traps(void)
 241 {
 242         char *volatile *tp;
 243
 244         for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
 245                 if (*tp && **tp)        /* trap not NULL or SIG_IGN */
 246                         return 1;
 247         }
 248         return 0;
 249 }
 250
 251 /*
 252  * Set the signal handler for the specified signal.  The routine figures
 253  * out what it should be set to.
 254  */
 255 void
 256 setsignal(int signo)
 257 {
 258         int action;
 259         sig_t sigact = SIG_DFL;
 260         struct sigaction sa;
 261         char *t;
 262
 263         if ((t = trap[signo]) == NULL)
 264                 action = S_DFL;
 265         else if (*t != '\0')
 266                 action = S_CATCH;
 267         else
 268                 action = S_IGN;
 269         if (action == S_DFL) {
 270                 switch (signo) {
 271                 case SIGINT:
 272                         action = S_CATCH;
 273                         break;
 274                 case SIGQUIT:
 275 #ifdef DEBUG
 276                         {
 277                         extern int debug;
 278
 279                         if (debug)
 280                                 break;
 281                         }
 282 #endif
 283                         action = S_CATCH;
 284                         break;
 285                 case SIGTERM:
 286                         if (rootshell && iflag)
 287                                 action = S_IGN;
 288                         break;
 289 #if JOBS
 290                 case SIGTSTP:
 291                 case SIGTTOU:
 292                         if (rootshell && mflag)
 293                                 action = S_IGN;
 294                         break;
 295 #endif
 296 #ifndef NO_HISTORY
 297                 case SIGWINCH:
 298                         if (rootshell && iflag)
 299                                 action = S_CATCH;
 300                         break;
 301 #endif
 302                 }
 303         }
 304
 305         t = &sigmode[signo];
 306         if (*t == 0) {
 307                 /*
 308                  * current setting unknown
 309                  */
 310                 if (!getsigaction(signo, &sigact)) {
 311                         /*
 312                          * Pretend it worked; maybe we should give a warning
 313                          * here, but other shells don't. We don't alter
 314                          * sigmode, so that we retry every time.
 315                          */
 316                         return;
 317                 }
 318                 if (sigact == SIG_IGN) {
 319                         if (mflag && (signo == SIGTSTP ||
 320                              signo == SIGTTIN || signo == SIGTTOU)) {
 321                                 *t = S_IGN;     /* don't hard ignore these */
 322                         } else
 323                                 *t = S_HARD_IGN;
 324                 } else {
 325                         *t = S_RESET;   /* force to be set */
 326                 }
 327         }
 328         if (*t == S_HARD_IGN || *t == action)
 329                 return;
 330         switch (action) {
 331                 case S_DFL:     sigact = SIG_DFL;       break;
 332                 case S_CATCH:   sigact = onsig;         break;
 333                 case S_IGN:     sigact = SIG_IGN;       break;
 334         }
 335         *t = action;
 336         sa.sa_handler = sigact;
 337         sa.sa_flags = 0;
 338         sigemptyset(&sa.sa_mask);
 339         sigaction(signo, &sa, NULL);
 340 }
 341
 342
 343 /*
 344  * Return the current setting for sig w/o changing it.
 345  */
 346 static int
 347 getsigaction(int signo, sig_t *sigact)
 348 {
 349         struct sigaction sa;
 350
 351         if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
 352                 return 0;
 353         *sigact = (sig_t) sa.sa_handler;
 354         return 1;
 355 }
 356
 357
 358 /*
 359  * Ignore a signal.
 360  */
 361 void
 362 ignoresig(int signo)
 363 {
 364
 365         if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) {
 366                 signal(signo, SIG_IGN);
 367         }
 368         sigmode[signo] = S_HARD_IGN;
 369 }
 370
 371
 372 int
 373 issigchldtrapped(void)
 374 {
 375
 376         return (trap[SIGCHLD] != NULL && *trap[SIGCHLD] != '\0');
 377 }
 378
 379
 380 /*
 381  * Signal handler.
 382  */
 383 void
 384 onsig(int signo)
 385 {
 386
 387         if (signo == SIGINT && trap[SIGINT] == NULL) {
 388                 onint();
 389                 return;
 390         }
 391
 392         /* If we are currently in a wait builtin, prepare to break it */
 393         if (signo == SIGINT || signo == SIGQUIT)
 394                 pendingsig_waitcmd = signo;
 395
 396         if (trap[signo] != NULL && trap[signo][0] != '\0' &&
 397             (signo != SIGCHLD || !ignore_sigchld)) {
 398                 gotsig[signo] = 1;
 399                 pendingsig = signo;
 400         }
 401
 402 #ifndef NO_HISTORY
 403         if (signo == SIGWINCH)
 404                 gotwinch = 1;
 405 #endif
 406 }
 407
 408
 409 /*
 410  * Called to execute a trap.  Perhaps we should avoid entering new trap
 411  * handlers while we are executing a trap handler.
 412  */
 413 void
 414 dotrap(void)
 415 {
 416         int i;
 417         int savestatus, prev_evalskip, prev_skipcount;
 418
 419         in_dotrap++;
 420         for (;;) {
 421                 pendingsig = 0;
 422                 pendingsig_waitcmd = 0;
 423                 for (i = 1; i < NSIG; i++) {
 424                         if (gotsig[i]) {
 425                                 gotsig[i] = 0;
 426                                 if (trap[i]) {
 427                                         /*
 428                                          * Ignore SIGCHLD to avoid infinite
 429                                          * recursion if the trap action does
 430                                          * a fork.
 431                                          */
 432                                         if (i == SIGCHLD)
 433                                                 ignore_sigchld++;
 434
 435                                         /*
 436                                          * Backup current evalskip
 437                                          * state and reset it before
 438                                          * executing a trap, so that the
 439                                          * trap is not disturbed by an
 440                                          * ongoing break/continue/return
 441                                          * statement.
 442                                          */
 443                                         prev_evalskip  = evalskip;
 444                                         prev_skipcount = skipcount;
 445                                         evalskip = 0;
 446
 447                                         last_trapsig = i;
 448                                         savestatus = exitstatus;
 449                                         evalstring(trap[i], 0);
 450
 451                                         /*
 452                                          * If such a command was not
 453                                          * already in progress, allow a
 454                                          * break/continue/return in the
 455                                          * trap action to have an effect
 456                                          * outside of it.
 457                                          */
 458                                         if (evalskip == 0 ||
 459                                             prev_evalskip != 0) {
 460                                                 evalskip  = prev_evalskip;
 461                                                 skipcount = prev_skipcount;
 462                                                 exitstatus = savestatus;
 463                                         }
 464
 465                                         if (i == SIGCHLD)
 466                                                 ignore_sigchld--;
 467                                 }
 468                                 break;
 469                         }
 470                 }
 471                 if (i >= NSIG)
 472                         break;
 473         }
 474         in_dotrap--;
 475 }
 476
 477
 478 /*
 479  * Controls whether the shell is interactive or not.
 480  */
 481 void
 482 setinteractive(int on)
 483 {
 484         static int is_interactive = -1;
 485
 486         if (on == is_interactive)
 487                 return;
 488         setsignal(SIGINT);
 489         setsignal(SIGQUIT);
 490         setsignal(SIGTERM);
 491 #ifndef NO_HISTORY
 492         setsignal(SIGWINCH);
 493 #endif
 494         is_interactive = on;
 495 }
 496
 497
 498 /*
 499  * Called to exit the shell.
 500  */
 501 void
 502 exitshell(int status)
 503 {
 504         TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
 505         exiting = 1;
 506         exiting_exitstatus = status;
 507         exitshell_savedstatus();
 508 }
 509
 510 void
 511 exitshell_savedstatus(void)
 512 {
 513         struct jmploc loc1, loc2;
 514         char *p;
 515         int sig = 0;
 516         sigset_t sigs;
 517
 518         if (!exiting) {
 519                 if (in_dotrap && last_trapsig) {
 520                         sig = last_trapsig;
 521                         exiting_exitstatus = sig + 128;
 522                 } else
 523                         exiting_exitstatus = oexitstatus;
 524         }
 525         exitstatus = oexitstatus = exiting_exitstatus;
 526         if (setjmp(loc1.loc)) {
 527                 goto l1;
 528         }
 529         if (setjmp(loc2.loc)) {
 530                 goto l2;
 531         }
 532         handler = &loc1;
 533         if ((p = trap[0]) != NULL && *p != '\0') {
 534                 /*
 535                  * Reset evalskip, or the trap on EXIT could be
 536                  * interrupted if the last command was a "return".
 537                  */
 538                 evalskip = 0;
 539                 trap[0] = NULL;
 540                 evalstring(p, 0);
 541         }
 542 l1:   handler = &loc2;                  /* probably unnecessary */
 543         flushall();
 544 #if JOBS
 545         setjobctl(0);
 546 #endif
 547 l2:
 548         if (sig != 0 && sig != SIGSTOP && sig != SIGTSTP && sig != SIGTTIN &&
 549             sig != SIGTTOU) {
 550                 signal(sig, SIG_DFL);
 551                 sigemptyset(&sigs);
 552                 sigaddset(&sigs, sig);
 553                 sigprocmask(SIG_UNBLOCK, &sigs, NULL);
 554                 kill(getpid(), sig);
 555                 /* If the default action is to ignore, fall back to _exit(). */
 556         }
 557         _exit(exiting_exitstatus);
 558 }