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  * @(#)trap.c   8.5 (Berkeley) 6/5/95
  33  * $FreeBSD: head/bin/sh/trap.c 247720 2013-03-03 17:33:59Z jilles $
  34  */
  35
  36 #include <signal.h>
  37 #include <unistd.h>
  38 #include <stdlib.h>
  39
  40 #include "shell.h"
  41 #include "main.h"
  42 #include "nodes.h"      /* for other headers */
  43 #include "eval.h"
  44 #include "jobs.h"
  45 #include "show.h"
  46 #include "options.h"
  47 #include "syntax.h"
  48 #include "output.h"
  49 #include "memalloc.h"
  50 #include "error.h"
  51 #include "trap.h"
  52 #include "mystring.h"
  53 #include "builtins.h"
  54 #include "myhistedit.h"
  55
  56
  57 /*
  58  * Sigmode records the current value of the signal handlers for the various
  59  * modes.  A value of zero means that the current handler is not known.
  60  * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
  61  */
  62
  63 #define S_DFL 1                 /* default signal handling (SIG_DFL) */
  64 #define S_CATCH 2               /* signal is caught */
  65 #define S_IGN 3                 /* signal is ignored (SIG_IGN) */
  66 #define S_HARD_IGN 4            /* signal is ignored permanently */
  67 #define S_RESET 5               /* temporary - to reset a hard ignored sig */
  68
  69
  70 MKINIT char sigmode[NSIG];      /* current value of signal */
  71 volatile sig_atomic_t pendingsig;       /* indicates some signal received */
  72 int in_dotrap;                  /* do we execute in a trap handler? */
  73 static char *volatile trap[NSIG];       /* trap handler commands */
  74 static volatile sig_atomic_t gotsig[NSIG];
  75                                 /* indicates specified signal received */
  76 static int ignore_sigchld;      /* Used while handling SIGCHLD traps. */
  77 volatile sig_atomic_t gotwinch;
  78 static int last_trapsig;
  79
  80 static int exiting;             /* exitshell() has been called */
  81 static int exiting_exitstatus;  /* value passed to exitshell() */
  82
  83 static int getsigaction(int, sig_t *);
  84
  85
  86 /*
  87  * Map a string to a signal number.
  88  *
  89  * Note: the signal number may exceed NSIG.
  90  */
  91 static int
  92 sigstring_to_signum(char *sig)
  93 {
  94
  95         if (is_number(sig)) {
  96                 int signo;
  97
  98                 signo = atoi(sig);
  99                 return ((signo >= 0 && signo < NSIG) ? signo : (-1));
 100         } else if (strcasecmp(sig, "EXIT") == 0) {
 101                 return (0);
 102         } else {
 103                 int n;
 104
 105                 if (strncasecmp(sig, "SIG", 3) == 0)
 106                         sig += 3;
 107                 for (n = 1; n < sys_nsig; n++)
 108                         if (sys_signame[n] &&
 109                             strcasecmp(sys_signame[n], sig) == 0)
 110                                 return (n);
 111         }
 112         return (-1);
 113 }
 114
 115
 116 /*
 117  * Print a list of valid signal names.
 118  */
 119 static void
 120 printsignals(void)
 121 {
 122         int n, outlen;
 123
 124         outlen = 0;
 125         for (n = 1; n < sys_nsig; n++) {
 126                 if (sys_signame[n]) {
 127                         out1fmt("%s", sys_signame[n]);
 128                         outlen += strlen(sys_signame[n]);
 129                 } else {
 130                         out1fmt("%d", n);
 131                         outlen += 3;    /* good enough */
 132                 }
 133                 ++outlen;
 134                 if (outlen > 71 || n == sys_nsig - 1) {
 135                         out1str("\n");
 136                         outlen = 0;
 137                 } else {
 138                         out1c(' ');
 139                 }
 140         }
 141 }
 142
 143
 144 /*
 145  * The trap builtin.
 146  */
 147 int
 148 trapcmd(int argc __unused, char **argv)
 149 {
 150         char *action;
 151         int signo;
 152         int errors = 0;
 153         int i;
 154
 155         while ((i = nextopt("l")) != '\0') {
 156                 switch (i) {
 157                 case 'l':
 158                         printsignals();
 159                         return (0);
 160                 }
 161         }
 162         argv = argptr;
 163
 164         if (*argv == NULL) {
 165                 for (signo = 0 ; signo < sys_nsig ; signo++) {
 166                         if (signo < NSIG && trap[signo] != NULL) {
 167                                 out1str("trap -- ");
 168                                 out1qstr(trap[signo]);
 169                                 if (signo == 0) {
 170                                         out1str(" EXIT\n");
 171                                 } else if (sys_signame[signo]) {
 172                                         out1fmt(" %s\n", sys_signame[signo]);
 173                                 } else {
 174                                         out1fmt(" %d\n", signo);
 175                                 }
 176                         }
 177                 }
 178                 return 0;
 179         }
 180         action = NULL;
 181         if (*argv && sigstring_to_signum(*argv) == -1) {
 182                 if (strcmp(*argv, "-") == 0)
 183                         argv++;
 184                 else {
 185                         action = *argv;
 186                         argv++;
 187                 }
 188         }
 189         for (; *argv; argv++) {
 190                 if ((signo = sigstring_to_signum(*argv)) == -1) {
 191                         warning("bad signal %s", *argv);
 192                         errors = 1;
 193                         continue;
 194                 }
 195                 INTOFF;
 196                 if (action)
 197                         action = savestr(action);
 198                 if (trap[signo])
 199                         ckfree(trap[signo]);
 200                 trap[signo] = action;
 201                 if (signo != 0)
 202                         setsignal(signo);
 203                 INTON;
 204         }
 205         return errors;
 206 }
 207
 208
 209 /*
 210  * Clear traps on a fork.
 211  */
 212 void
 213 clear_traps(void)
 214 {
 215         char *volatile *tp;
 216
 217         for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
 218                 if (*tp && **tp) {      /* trap not NULL or SIG_IGN */
 219                         INTOFF;
 220                         ckfree(*tp);
 221                         *tp = NULL;
 222                         if (tp != &trap[0])
 223                                 setsignal(tp - trap);
 224                         INTON;
 225                 }
 226         }
 227 }
 228
 229
 230 /*
 231  * Check if we have any traps enabled.
 232  */
 233 int
 234 have_traps(void)
 235 {
 236         char *volatile *tp;
 237
 238         for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
 239                 if (*tp && **tp)        /* trap not NULL or SIG_IGN */
 240                         return 1;
 241         }
 242         return 0;
 243 }
 244
 245 /*
 246  * Set the signal handler for the specified signal.  The routine figures
 247  * out what it should be set to.
 248  */
 249 void
 250 setsignal(int signo)
 251 {
 252         int action;
 253         sig_t sigact = SIG_DFL;
 254         struct sigaction sa;
 255         char *t;
 256
 257         if ((t = trap[signo]) == NULL)
 258                 action = S_DFL;
 259         else if (*t != '\0')
 260                 action = S_CATCH;
 261         else
 262                 action = S_IGN;
 263         if (action == S_DFL) {
 264                 switch (signo) {
 265                 case SIGINT:
 266                         action = S_CATCH;
 267                         break;
 268                 case SIGQUIT:
 269 #ifdef DEBUG
 270                         {
 271                         extern int debug;
 272
 273                         if (debug)
 274                                 break;
 275                         }
 276 #endif
 277                         action = S_CATCH;
 278                         break;
 279                 case SIGTERM:
 280                         if (rootshell && iflag)
 281                                 action = S_IGN;
 282                         break;
 283 #if JOBS
 284                 case SIGTSTP:
 285                 case SIGTTOU:
 286                         if (rootshell && mflag)
 287                                 action = S_IGN;
 288                         break;
 289 #endif
 290 #ifndef NO_HISTORY
 291                 case SIGWINCH:
 292                         if (rootshell && iflag)
 293                                 action = S_CATCH;
 294                         break;
 295 #endif
 296                 }
 297         }
 298
 299         t = &sigmode[signo];
 300         if (*t == 0) {
 301                 /*
 302                  * current setting unknown
 303                  */
 304                 if (!getsigaction(signo, &sigact)) {
 305                         /*
 306                          * Pretend it worked; maybe we should give a warning
 307                          * here, but other shells don't. We don't alter
 308                          * sigmode, so that we retry every time.
 309                          */
 310                         return;
 311                 }
 312                 if (sigact == SIG_IGN) {
 313                         if (mflag && (signo == SIGTSTP ||
 314                              signo == SIGTTIN || signo == SIGTTOU)) {
 315                                 *t = S_IGN;     /* don't hard ignore these */
 316                         } else
 317                                 *t = S_HARD_IGN;
 318                 } else {
 319                         *t = S_RESET;   /* force to be set */
 320                 }
 321         }
 322         if (*t == S_HARD_IGN || *t == action)
 323                 return;
 324         switch (action) {
 325                 case S_DFL:     sigact = SIG_DFL;       break;
 326                 case S_CATCH:   sigact = onsig;         break;
 327                 case S_IGN:     sigact = SIG_IGN;       break;
 328         }
 329         *t = action;
 330         sa.sa_handler = sigact;
 331         sa.sa_flags = 0;
 332         sigemptyset(&sa.sa_mask);
 333         sigaction(signo, &sa, NULL);
 334 }
 335
 336
 337 /*
 338  * Return the current setting for sig w/o changing it.
 339  */
 340 static int
 341 getsigaction(int signo, sig_t *sigact)
 342 {
 343         struct sigaction sa;
 344
 345         if (sigaction(signo, NULL, &sa) == -1)
 346                 return 0;
 347         *sigact = (sig_t) sa.sa_handler;
 348         return 1;
 349 }
 350
 351
 352 /*
 353  * Ignore a signal.
 354  */
 355 void
 356 ignoresig(int signo)
 357 {
 358
 359         if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) {
 360                 signal(signo, SIG_IGN);
 361         }
 362         sigmode[signo] = S_HARD_IGN;
 363 }
 364
 365
 366 int
 367 issigchldtrapped(void)
 368 {
 369
 370         return (trap[SIGCHLD] != NULL && *trap[SIGCHLD] != '\0');
 371 }
 372
 373
 374 /*
 375  * Signal handler.
 376  */
 377 void
 378 onsig(int signo)
 379 {
 380
 381         if (signo == SIGINT && trap[SIGINT] == NULL) {
 382                 onint();
 383                 return;
 384         }
 385
 386         /* If we are currently in a wait builtin, prepare to break it */
 387         if ((signo == SIGINT || signo == SIGQUIT) && in_waitcmd != 0) {
 388                 breakwaitcmd = 1;
 389                 pendingsig = signo;
 390         }
 391
 392         if (trap[signo] != NULL && trap[signo][0] != '\0' &&
 393             (signo != SIGCHLD || !ignore_sigchld)) {
 394                 gotsig[signo] = 1;
 395                 pendingsig = signo;
 396
 397                 /*
 398                  * If a trap is set, not ignored and not the null command, we
 399                  * need to make sure traps are executed even when a child
 400                  * blocks signals.
 401                  */
 402                 if (Tflag && !(trap[signo][0] == ':' && trap[signo][1] == '\0'))
 403                         breakwaitcmd = 1;
 404         }
 405
 406 #ifndef NO_HISTORY
 407         if (signo == SIGWINCH)
 408                 gotwinch = 1;
 409 #endif
 410 }
 411
 412
 413 /*
 414  * Called to execute a trap.  Perhaps we should avoid entering new trap
 415  * handlers while we are executing a trap handler.
 416  */
 417 void
 418 dotrap(void)
 419 {
 420         int i;
 421         int savestatus, prev_evalskip, prev_skipcount;
 422
 423         in_dotrap++;
 424         for (;;) {
 425                 pendingsig = 0;
 426                 for (i = 1; i < NSIG; i++) {
 427                         if (gotsig[i]) {
 428                                 gotsig[i] = 0;
 429                                 if (trap[i]) {
 430                                         /*
 431                                          * Ignore SIGCHLD to avoid infinite
 432                                          * recursion if the trap action does
 433                                          * a fork.
 434                                          */
 435                                         if (i == SIGCHLD)
 436                                                 ignore_sigchld++;
 437
 438                                         /*
 439                                          * Backup current evalskip
 440                                          * state and reset it before
 441                                          * executing a trap, so that the
 442                                          * trap is not disturbed by an
 443                                          * ongoing break/continue/return
 444                                          * statement.
 445                                          */
 446                                         prev_evalskip  = evalskip;
 447                                         prev_skipcount = skipcount;
 448                                         evalskip = 0;
 449
 450                                         last_trapsig = i;
 451                                         savestatus = exitstatus;
 452                                         evalstring(trap[i], 0);
 453
 454                                         /*
 455                                          * If such a command was not
 456                                          * already in progress, allow a
 457                                          * break/continue/return in the
 458                                          * trap action to have an effect
 459                                          * outside of it.
 460                                          */
 461                                         if (evalskip == 0 ||
 462                                             prev_evalskip != 0) {
 463                                                 evalskip  = prev_evalskip;
 464                                                 skipcount = prev_skipcount;
 465                                                 exitstatus = savestatus;
 466                                         }
 467
 468                                         if (i == SIGCHLD)
 469                                                 ignore_sigchld--;
 470                                 }
 471                                 break;
 472                         }
 473                 }
 474                 if (i >= NSIG)
 475                         break;
 476         }
 477         in_dotrap--;
 478 }
 479
 480
 481 /*
 482  * Controls whether the shell is interactive or not.
 483  */
 484 void
 485 setinteractive(int on)
 486 {
 487         static int is_interactive = -1;
 488
 489         if (on == is_interactive)
 490                 return;
 491         setsignal(SIGINT);
 492         setsignal(SIGQUIT);
 493         setsignal(SIGTERM);
 494 #ifndef NO_HISTORY
 495         setsignal(SIGWINCH);
 496 #endif
 497         is_interactive = on;
 498 }
 499
 500
 501 /*
 502  * Called to exit the shell.
 503  */
 504 void
 505 exitshell(int status)
 506 {
 507         TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
 508         exiting = 1;
 509         exiting_exitstatus = status;
 510         exitshell_savedstatus();
 511 }
 512
 513 void
 514 exitshell_savedstatus(void)
 515 {
 516         struct jmploc loc1, loc2;
 517         char *p;
 518         volatile int sig = 0;
 519         sigset_t sigs;
 520
 521         if (!exiting) {
 522                 if (in_dotrap && last_trapsig) {
 523                         sig = last_trapsig;
 524                         exiting_exitstatus = sig + 128;
 525                 } else
 526                         exiting_exitstatus = oexitstatus;
 527         }
 528         exitstatus = oexitstatus = exiting_exitstatus;
 529         if (setjmp(loc1.loc)) {
 530                 goto l1;
 531         }
 532         if (setjmp(loc2.loc)) {
 533                 goto l2;
 534         }
 535         handler = &loc1;
 536         if ((p = trap[0]) != NULL && *p != '\0') {
 537                 /*
 538                  * Reset evalskip, or the trap on EXIT could be
 539                  * interrupted if the last command was a "return".
 540                  */
 541                 evalskip = 0;
 542                 trap[0] = NULL;
 543                 evalstring(p, 0);
 544         }
 545 l1:   handler = &loc2;                  /* probably unnecessary */
 546         flushall();
 547 #if JOBS
 548         setjobctl(0);
 549 #endif
 550 l2:
 551         if (sig != 0 && sig != SIGSTOP && sig != SIGTSTP && sig != SIGTTIN &&
 552             sig != SIGTTOU) {
 553                 signal(sig, SIG_DFL);
 554                 sigemptyset(&sigs);
 555                 sigaddset(&sigs, sig);
 556                 sigprocmask(SIG_UNBLOCK, &sigs, NULL);
 557                 kill(getpid(), sig);
 558                 /* If the default action is to ignore, fall back to _exit(). */
 559         }
 560         _exit(exiting_exitstatus);
 561 }