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