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 static int last_trapsig;
  84
  85 static int exiting;             /* exitshell() has been called */
  86 static int exiting_exitstatus;  /* value passed to exitshell() */
  87
  88 static int getsigaction(int, sig_t *);
  89
  90
  91 /*
  92  * Map a string to a signal number.
  93  *
  94  * Note: the signal number may exceed NSIG.
  95  */
  96 static int
  97 sigstring_to_signum(char *sig)
  98 {
  99
 100         if (is_number(sig)) {
 101                 int signo;
 102
 103                 signo = atoi(sig);
 104                 return ((signo >= 0 && signo < NSIG) ? signo : (-1));
 105         } else if (strcasecmp(sig, "EXIT") == 0) {
 106                 return (0);
 107         } else {
 108                 int n;
 109
 110                 if (strncasecmp(sig, "SIG", 3) == 0)
 111                         sig += 3;
 112                 for (n = 1; n < sys_nsig; n++)
 113                         if (sys_signame[n] &&
 114                             strcasecmp(sys_signame[n], sig) == 0)
 115                                 return (n);
 116         }
 117         return (-1);
 118 }
 119
 120
 121 /*
 122  * Print a list of valid signal names.
 123  */
 124 static void
 125 printsignals(void)
 126 {
 127         int n, outlen;
 128
 129         outlen = 0;
 130         for (n = 1; n < sys_nsig; n++) {
 131                 if (sys_signame[n]) {
 132                         out1fmt("%s", sys_signame[n]);
 133                         outlen += strlen(sys_signame[n]);
 134                 } else {
 135                         out1fmt("%d", n);
 136                         outlen += 3;    /* good enough */
 137                 }
 138                 ++outlen;
 139                 if (outlen > 71 || n == sys_nsig - 1) {
 140                         out1str("\n");
 141                         outlen = 0;
 142                 } else {
 143                         out1c(' ');
 144                 }
 145         }
 146 }
 147
 148
 149 /*
 150  * The trap builtin.
 151  */
 152 int
 153 trapcmd(int argc __unused, char **argv)
 154 {
 155         char *action;
 156         int signo;
 157         int errors = 0;
 158         int i;
 159
 160         while ((i = nextopt("l")) != '\0') {
 161                 switch (i) {
 162                 case 'l':
 163                         printsignals();
 164                         return (0);
 165                 }
 166         }
 167         argv = argptr;
 168
 169         if (*argv == NULL) {
 170                 for (signo = 0 ; signo < sys_nsig ; signo++) {
 171                         if (signo < NSIG && trap[signo] != NULL) {
 172                                 out1str("trap -- ");
 173                                 out1qstr(trap[signo]);
 174                                 if (signo == 0) {
 175                                         out1str(" EXIT\n");
 176                                 } else if (sys_signame[signo]) {
 177                                         out1fmt(" %s\n", sys_signame[signo]);
 178                                 } else {
 179                                         out1fmt(" %d\n", signo);
 180                                 }
 181                         }
 182                 }
 183                 return 0;
 184         }
 185         action = NULL;
 186         if (*argv && sigstring_to_signum(*argv) == -1) {
 187                 if (strcmp(*argv, "-") == 0)
 188                         argv++;
 189                 else {
 190                         action = *argv;
 191                         argv++;
 192                 }
 193         }
 194         for (; *argv; argv++) {
 195                 if ((signo = sigstring_to_signum(*argv)) == -1) {
 196                         warning("bad signal %s", *argv);
 197                         errors = 1;
 198                         continue;
 199                 }
 200                 INTOFF;
 201                 if (action)
 202                         action = savestr(action);
 203                 if (trap[signo])
 204                         ckfree(trap[signo]);
 205                 trap[signo] = action;
 206                 if (signo != 0)
 207                         setsignal(signo);
 208                 INTON;
 209         }
 210         return errors;
 211 }
 212
 213
 214 /*
 215  * Clear traps on a fork.
 216  */
 217 void
 218 clear_traps(void)
 219 {
 220         char *volatile *tp;
 221
 222         for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
 223                 if (*tp && **tp) {      /* trap not NULL or SIG_IGN */
 224                         INTOFF;
 225                         ckfree(*tp);
 226                         *tp = NULL;
 227                         if (tp != &trap[0])
 228                                 setsignal(tp - trap);
 229                         INTON;
 230                 }
 231         }
 232 }
 233
 234
 235 /*
 236  * Check if we have any traps enabled.
 237  */
 238 int
 239 have_traps(void)
 240 {
 241         char *volatile *tp;
 242
 243         for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
 244                 if (*tp && **tp)        /* trap not NULL or SIG_IGN */
 245                         return 1;
 246         }
 247         return 0;
 248 }
 249
 250 /*
 251  * Set the signal handler for the specified signal.  The routine figures
 252  * out what it should be set to.
 253  */
 254 void
 255 setsignal(int signo)
 256 {
 257         int action;
 258         sig_t sigact = SIG_DFL;
 259         struct sigaction sa;
 260         char *t;
 261
 262         if ((t = trap[signo]) == NULL)
 263                 action = S_DFL;
 264         else if (*t != '\0')
 265                 action = S_CATCH;
 266         else
 267                 action = S_IGN;
 268         if (action == S_DFL) {
 269                 switch (signo) {
 270                 case SIGINT:
 271                         action = S_CATCH;
 272                         break;
 273                 case SIGQUIT:
 274 #ifdef DEBUG
 275                         {
 276                         extern int debug;
 277
 278                         if (debug)
 279                                 break;
 280                         }
 281 #endif
 282                         action = S_CATCH;
 283                         break;
 284                 case SIGTERM:
 285                         if (rootshell && iflag)
 286                                 action = S_IGN;
 287                         break;
 288 #if JOBS
 289                 case SIGTSTP:
 290                 case SIGTTOU:
 291                         if (rootshell && mflag)
 292                                 action = S_IGN;
 293                         break;
 294 #endif
 295                 }
 296         }
 297
 298         t = &sigmode[signo];
 299         if (*t == 0) {
 300                 /*
 301                  * current setting unknown
 302                  */
 303                 if (!getsigaction(signo, &sigact)) {
 304                         /*
 305                          * Pretend it worked; maybe we should give a warning
 306                          * here, but other shells don't. We don't alter
 307                          * sigmode, so that we retry every time.
 308                          */
 309                         return;
 310                 }
 311                 if (sigact == SIG_IGN) {
 312                         if (mflag && (signo == SIGTSTP ||
 313                              signo == SIGTTIN || signo == SIGTTOU)) {
 314                                 *t = S_IGN;     /* don't hard ignore these */
 315                         } else
 316                                 *t = S_HARD_IGN;
 317                 } else {
 318                         *t = S_RESET;   /* force to be set */
 319                 }
 320         }
 321         if (*t == S_HARD_IGN || *t == action)
 322                 return;
 323         switch (action) {
 324                 case S_DFL:     sigact = SIG_DFL;       break;
 325                 case S_CATCH:   sigact = onsig;         break;
 326                 case S_IGN:     sigact = SIG_IGN;       break;
 327         }
 328         *t = action;
 329         sa.sa_handler = sigact;
 330         sa.sa_flags = 0;
 331         sigemptyset(&sa.sa_mask);
 332         sigaction(signo, &sa, NULL);
 333 }
 334
 335
 336 /*
 337  * Return the current setting for sig w/o changing it.
 338  */
 339 static int
 340 getsigaction(int signo, sig_t *sigact)
 341 {
 342         struct sigaction sa;
 343
 344         if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
 345                 return 0;
 346         *sigact = (sig_t) sa.sa_handler;
 347         return 1;
 348 }
 349
 350
 351 /*
 352  * Ignore a signal.
 353  */
 354 void
 355 ignoresig(int signo)
 356 {
 357
 358         if (sigmode[signo] == 0)
 359                 setsignal(signo);
 360         if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) {
 361                 signal(signo, SIG_IGN);
 362                 sigmode[signo] = S_IGN;
 363         }
 364 }
 365
 366
 367 int
 368 issigchldtrapped(void)
 369 {
 370
 371         return (trap[SIGCHLD] != NULL && *trap[SIGCHLD] != '\0');
 372 }
 373
 374
 375 /*
 376  * Signal handler.
 377  */
 378 void
 379 onsig(int signo)
 380 {
 381
 382         if (signo == SIGINT && trap[SIGINT] == NULL) {
 383                 onint();
 384                 return;
 385         }
 386
 387         /* If we are currently in a wait builtin, prepare to break it */
 388         if (signo == SIGINT || signo == SIGQUIT)
 389                 pendingsig_waitcmd = signo;
 390
 391         if (trap[signo] != NULL && trap[signo][0] != '\0' &&
 392             (signo != SIGCHLD || !ignore_sigchld)) {
 393                 gotsig[signo] = 1;
 394                 pendingsig = signo;
 395         }
 396 }
 397
 398
 399 /*
 400  * Called to execute a trap.  Perhaps we should avoid entering new trap
 401  * handlers while we are executing a trap handler.
 402  */
 403 void
 404 dotrap(void)
 405 {
 406         struct stackmark smark;
 407         int i;
 408         int savestatus, prev_evalskip, prev_skipcount;
 409
 410         in_dotrap++;
 411         for (;;) {
 412                 pendingsig = 0;
 413                 pendingsig_waitcmd = 0;
 414                 for (i = 1; i < NSIG; i++) {
 415                         if (gotsig[i]) {
 416                                 gotsig[i] = 0;
 417                                 if (trap[i]) {
 418                                         /*
 419                                          * Ignore SIGCHLD to avoid infinite
 420                                          * recursion if the trap action does
 421                                          * a fork.
 422                                          */
 423                                         if (i == SIGCHLD)
 424                                                 ignore_sigchld++;
 425
 426                                         /*
 427                                          * Backup current evalskip
 428                                          * state and reset it before
 429                                          * executing a trap, so that the
 430                                          * trap is not disturbed by an
 431                                          * ongoing break/continue/return
 432                                          * statement.
 433                                          */
 434                                         prev_evalskip  = evalskip;
 435                                         prev_skipcount = skipcount;
 436                                         evalskip = 0;
 437
 438                                         last_trapsig = i;
 439                                         savestatus = exitstatus;
 440                                         setstackmark(&smark);
 441                                         evalstring(stsavestr(trap[i]), 0);
 442                                         popstackmark(&smark);
 443
 444                                         /*
 445                                          * If such a command was not
 446                                          * already in progress, allow a
 447                                          * break/continue/return in the
 448                                          * trap action to have an effect
 449                                          * outside of it.
 450                                          */
 451                                         if (evalskip == 0 ||
 452                                             prev_evalskip != 0) {
 453                                                 evalskip  = prev_evalskip;
 454                                                 skipcount = prev_skipcount;
 455                                                 exitstatus = savestatus;
 456                                         }
 457
 458                                         if (i == SIGCHLD)
 459                                                 ignore_sigchld--;
 460                                 }
 461                                 break;
 462                         }
 463                 }
 464                 if (i >= NSIG)
 465                         break;
 466         }
 467         in_dotrap--;
 468 }
 469
 470
 471 /*
 472  * Controls whether the shell is interactive or not.
 473  */
 474 void
 475 setinteractive(int on)
 476 {
 477         static int is_interactive = -1;
 478
 479         if (on == is_interactive)
 480                 return;
 481         setsignal(SIGINT);
 482         setsignal(SIGQUIT);
 483         setsignal(SIGTERM);
 484         is_interactive = on;
 485 }
 486
 487
 488 /*
 489  * Called to exit the shell.
 490  */
 491 void
 492 exitshell(int status)
 493 {
 494         TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
 495         exiting = 1;
 496         exiting_exitstatus = status;
 497         exitshell_savedstatus();
 498 }
 499
 500 void
 501 exitshell_savedstatus(void)
 502 {
 503         struct jmploc loc1, loc2;
 504         char *p;
 505         int sig = 0;
 506         sigset_t sigs;
 507
 508         if (!exiting) {
 509                 if (in_dotrap && last_trapsig) {
 510                         sig = last_trapsig;
 511                         exiting_exitstatus = sig + 128;
 512                 } else
 513                         exiting_exitstatus = oexitstatus;
 514         }
 515         exitstatus = oexitstatus = exiting_exitstatus;
 516         if (!setjmp(loc1.loc)) {
 517                 handler = &loc1;
 518                 if ((p = trap[0]) != NULL && *p != '\0') {
 519                         /*
 520                          * Reset evalskip, or the trap on EXIT could be
 521                          * interrupted if the last command was a "return".
 522                          */
 523                         evalskip = 0;
 524                         trap[0] = NULL;
 525                         evalstring(p, 0);
 526                 }
 527         }
 528         if (!setjmp(loc2.loc)) {
 529                 handler = &loc2;                /* probably unnecessary */
 530                 flushall();
 531 #if JOBS
 532                 setjobctl(0);
 533 #endif
 534         }
 535         if (sig != 0 && sig != SIGSTOP && sig != SIGTSTP && sig != SIGTTIN &&
 536             sig != SIGTTOU) {
 537                 signal(sig, SIG_DFL);
 538                 sigemptyset(&sigs);
 539                 sigaddset(&sigs, sig);
 540                 sigprocmask(SIG_UNBLOCK, &sigs, NULL);
 541                 kill(getpid(), sig);
 542                 /* If the default action is to ignore, fall back to _exit(). */
 543         }
 544         _exit(exiting_exitstatus);
 545 }