bin/sh/trap.c

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