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: head/bin/sh/trap.c 326025 2017-11-20 19:49:47Z pfg $");
  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 #ifdef __APPLE__
  64 #define sys_nsig (NSIG)
  65 #endif /* __APPLE__ */
  66
  67 /*
  68  * Sigmode records the current value of the signal handlers for the various
  69  * modes.  A value of zero means that the current handler is not known.
  70  * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
  71  */
  72
  73 #define S_DFL 1                 /* default signal handling (SIG_DFL) */
  74 #define S_CATCH 2               /* signal is caught */
  75 #define S_IGN 3                 /* signal is ignored (SIG_IGN) */
  76 #define S_HARD_IGN 4            /* signal is ignored permanently */
  77 #define S_RESET 5               /* temporary - to reset a hard ignored sig */
  78
  79
  80 static char sigmode[NSIG];      /* current value of signal */
  81 volatile sig_atomic_t pendingsig;       /* indicates some signal received */
  82 volatile sig_atomic_t pendingsig_waitcmd;       /* indicates wait builtin should be interrupted */
  83 static int in_dotrap;                   /* do we execute in a trap handler? */
  84 static char *volatile trap[NSIG];       /* trap handler commands */
  85 static volatile sig_atomic_t gotsig[NSIG];
  86                                 /* indicates specified signal received */
  87 static int ignore_sigchld;      /* Used while handling SIGCHLD traps. */
  88 static int last_trapsig;
  89
  90 static int exiting;             /* exitshell() has been called */
  91 static int exiting_exitstatus;  /* value passed to exitshell() */
  92
  93 static int getsigaction(int, sig_t *);
  94
  95
  96 /*
  97  * Map a string to a signal number.
  98  *
  99  * Note: the signal number may exceed NSIG.
 100  */
 101 static int
 102 sigstring_to_signum(char *sig)
 103 {
 104
 105         if (is_number(sig)) {
 106                 int signo;
 107
 108                 signo = atoi(sig);
 109                 return ((signo >= 0 && signo < NSIG) ? signo : (-1));
 110         } else if (strcasecmp(sig, "EXIT") == 0) {
 111                 return (0);
 112         } else {
 113                 int n;
 114
 115                 if (strncasecmp(sig, "SIG", 3) == 0)
 116                         sig += 3;
 117                 for (n = 1; n < sys_nsig; n++)
 118                         if (sys_signame[n] &&
 119                             strcasecmp(sys_signame[n], sig) == 0)
 120                                 return (n);
 121         }
 122         return (-1);
 123 }
 124
 125
 126 /*
 127  * Print a list of valid signal names.
 128  */
 129 static void
 130 printsignals(void)
 131 {
 132         int n, outlen;
 133
 134         outlen = 0;
 135         for (n = 1; n < sys_nsig; n++) {
 136                 if (sys_signame[n]) {
 137                         out1fmt("%s", sys_signame[n]);
 138                         outlen += strlen(sys_signame[n]);
 139                 } else {
 140                         out1fmt("%d", n);
 141                         outlen += 3;    /* good enough */
 142                 }
 143                 ++outlen;
 144                 if (outlen > 71 || n == sys_nsig - 1) {
 145                         out1str("\n");
 146                         outlen = 0;
 147                 } else {
 148                         out1c(' ');
 149                 }
 150         }
 151 }
 152
 153
 154 /*
 155  * The trap builtin.
 156  */
 157 int
 158 trapcmd(int argc __unused, char **argv)
 159 {
 160         char *action;
 161         int signo;
 162         int errors = 0;
 163         int i;
 164
 165         while ((i = nextopt("l")) != '\0') {
 166                 switch (i) {
 167                 case 'l':
 168                         printsignals();
 169                         return (0);
 170                 }
 171         }
 172         argv = argptr;
 173
 174         if (*argv == NULL) {
 175                 for (signo = 0 ; signo < sys_nsig ; signo++) {
 176                         if (signo < NSIG && trap[signo] != NULL) {
 177                                 out1str("trap -- ");
 178                                 out1qstr(trap[signo]);
 179                                 if (signo == 0) {
 180                                         out1str(" EXIT\n");
 181                                 } else if (sys_signame[signo]) {
 182                                         out1fmt(" %s\n", sys_signame[signo]);
 183                                 } else {
 184                                         out1fmt(" %d\n", signo);
 185                                 }
 186                         }
 187                 }
 188                 return 0;
 189         }
 190         action = NULL;
 191         if (*argv && !is_number(*argv)) {
 192                 if (strcmp(*argv, "-") == 0)
 193                         argv++;
 194                 else {
 195                         action = *argv;
 196                         argv++;
 197                 }
 198         }
 199         for (; *argv; argv++) {
 200                 if ((signo = sigstring_to_signum(*argv)) == -1) {
 201                         warning("bad signal %s", *argv);
 202                         errors = 1;
 203                         continue;
 204                 }
 205                 INTOFF;
 206                 if (action)
 207                         action = savestr(action);
 208                 if (trap[signo])
 209                         ckfree(trap[signo]);
 210                 trap[signo] = action;
 211                 if (signo != 0)
 212                         setsignal(signo);
 213                 INTON;
 214         }
 215         return errors;
 216 }
 217
 218
 219 /*
 220  * Clear traps on a fork.
 221  */
 222 void
 223 clear_traps(void)
 224 {
 225         char *volatile *tp;
 226
 227         for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
 228                 if (*tp && **tp) {      /* trap not NULL or SIG_IGN */
 229                         INTOFF;
 230                         ckfree(*tp);
 231                         *tp = NULL;
 232                         if (tp != &trap[0])
 233                                 setsignal(tp - trap);
 234                         INTON;
 235                 }
 236         }
 237 }
 238
 239
 240 /*
 241  * Check if we have any traps enabled.
 242  */
 243 int
 244 have_traps(void)
 245 {
 246         char *volatile *tp;
 247
 248         for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
 249                 if (*tp && **tp)        /* trap not NULL or SIG_IGN */
 250                         return 1;
 251         }
 252         return 0;
 253 }
 254
 255 /*
 256  * Set the signal handler for the specified signal.  The routine figures
 257  * out what it should be set to.
 258  */
 259 void
 260 setsignal(int signo)
 261 {
 262         int action;
 263         sig_t sigact = SIG_DFL;
 264         struct sigaction sa;
 265         char *t;
 266
 267         if ((t = trap[signo]) == NULL)
 268                 action = S_DFL;
 269         else if (*t != '\0')
 270                 action = S_CATCH;
 271         else
 272                 action = S_IGN;
 273         if (action == S_DFL) {
 274                 switch (signo) {
 275                 case SIGINT:
 276                         action = S_CATCH;
 277                         break;
 278                 case SIGQUIT:
 279 #ifdef DEBUG
 280                         {
 281                         extern int debug;
 282
 283                         if (debug)
 284                                 break;
 285                         }
 286 #endif
 287                         action = S_CATCH;
 288                         break;
 289                 case SIGTERM:
 290                         if (rootshell && iflag)
 291                                 action = S_IGN;
 292                         break;
 293 #if JOBS
 294                 case SIGTSTP:
 295                 case SIGTTOU:
 296                         if (rootshell && mflag)
 297                                 action = S_IGN;
 298                         break;
 299 #endif
 300                 }
 301         }
 302
 303         t = &sigmode[signo];
 304         if (*t == 0) {
 305                 /*
 306                  * current setting unknown
 307                  */
 308                 if (!getsigaction(signo, &sigact)) {
 309                         /*
 310                          * Pretend it worked; maybe we should give a warning
 311                          * here, but other shells don't. We don't alter
 312                          * sigmode, so that we retry every time.
 313                          */
 314                         return;
 315                 }
 316                 if (sigact == SIG_IGN) {
 317                         if (mflag && (signo == SIGTSTP ||
 318                              signo == SIGTTIN || signo == SIGTTOU)) {
 319                                 *t = S_IGN;     /* don't hard ignore these */
 320                         } else
 321                                 *t = S_HARD_IGN;
 322                 } else {
 323                         *t = S_RESET;   /* force to be set */
 324                 }
 325         }
 326         if (*t == S_HARD_IGN || *t == action)
 327                 return;
 328         switch (action) {
 329                 case S_DFL:     sigact = SIG_DFL;       break;
 330                 case S_CATCH:   sigact = onsig;         break;
 331                 case S_IGN:     sigact = SIG_IGN;       break;
 332         }
 333         *t = action;
 334         sa.sa_handler = sigact;
 335         sa.sa_flags = 0;
 336         sigemptyset(&sa.sa_mask);
 337         sigaction(signo, &sa, NULL);
 338 }
 339
 340
 341 /*
 342  * Return the current setting for sig w/o changing it.
 343  */
 344 static int
 345 getsigaction(int signo, sig_t *sigact)
 346 {
 347         struct sigaction sa;
 348
 349         if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
 350                 return 0;
 351         *sigact = (sig_t) sa.sa_handler;
 352         return 1;
 353 }
 354
 355
 356 /*
 357  * Ignore a signal.
 358  */
 359 void
 360 ignoresig(int signo)
 361 {
 362
 363         if (sigmode[signo] == 0)
 364                 setsignal(signo);
 365         if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) {
 366                 signal(signo, SIG_IGN);
 367                 sigmode[signo] = S_IGN;
 368         }
 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                 /*
 389                  * The !in_dotrap here is safe.  The only way we can arrive
 390                  * here with in_dotrap set is that a trap handler set SIGINT to
 391                  * SIG_DFL and killed itself.
 392                  */
 393                 if (suppressint && !in_dotrap)
 394                         SET_PENDING_INT;
 395                 else
 396                         onint();
 397                 return;
 398         }
 399
 400         /* If we are currently in a wait builtin, prepare to break it */
 401         if (signo == SIGINT || signo == SIGQUIT)
 402                 pendingsig_waitcmd = signo;
 403
 404         if (trap[signo] != NULL && trap[signo][0] != '\0' &&
 405             (signo != SIGCHLD || !ignore_sigchld)) {
 406                 gotsig[signo] = 1;
 407                 pendingsig = signo;
 408                 pendingsig_waitcmd = signo;
 409         }
 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         struct stackmark smark;
 421         int i;
 422         int savestatus, prev_evalskip, prev_skipcount;
 423
 424         in_dotrap++;
 425         for (;;) {
 426                 pendingsig = 0;
 427                 pendingsig_waitcmd = 0;
 428                 for (i = 1; i < NSIG; i++) {
 429                         if (gotsig[i]) {
 430                                 gotsig[i] = 0;
 431                                 if (trap[i]) {
 432                                         /*
 433                                          * Ignore SIGCHLD to avoid infinite
 434                                          * recursion if the trap action does
 435                                          * a fork.
 436                                          */
 437                                         if (i == SIGCHLD)
 438                                                 ignore_sigchld++;
 439
 440                                         /*
 441                                          * Backup current evalskip
 442                                          * state and reset it before
 443                                          * executing a trap, so that the
 444                                          * trap is not disturbed by an
 445                                          * ongoing break/continue/return
 446                                          * statement.
 447                                          */
 448                                         prev_evalskip  = evalskip;
 449                                         prev_skipcount = skipcount;
 450                                         evalskip = 0;
 451
 452                                         last_trapsig = i;
 453                                         savestatus = exitstatus;
 454                                         setstackmark(&smark);
 455                                         evalstring(stsavestr(trap[i]), 0);
 456                                         popstackmark(&smark);
 457
 458                                         /*
 459                                          * If such a command was not
 460                                          * already in progress, allow a
 461                                          * break/continue/return in the
 462                                          * trap action to have an effect
 463                                          * outside of it.
 464                                          */
 465                                         if (evalskip == 0 ||
 466                                             prev_evalskip != 0) {
 467                                                 evalskip  = prev_evalskip;
 468                                                 skipcount = prev_skipcount;
 469                                                 exitstatus = savestatus;
 470                                         }
 471
 472                                         if (i == SIGCHLD)
 473                                                 ignore_sigchld--;
 474                                 }
 475                                 break;
 476                         }
 477                 }
 478                 if (i >= NSIG)
 479                         break;
 480         }
 481         in_dotrap--;
 482 }
 483
 484
 485 /*
 486  * Controls whether the shell is interactive or not based on iflag.
 487  */
 488 void
 489 setinteractive(void)
 490 {
 491         setsignal(SIGINT);
 492         setsignal(SIGQUIT);
 493         setsignal(SIGTERM);
 494 }
 495
 496
 497 /*
 498  * Called to exit the shell.
 499  */
 500 void
 501 exitshell(int status)
 502 {
 503         TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
 504         exiting = 1;
 505         exiting_exitstatus = status;
 506         exitshell_savedstatus();
 507 }
 508
 509 void
 510 exitshell_savedstatus(void)
 511 {
 512         struct jmploc loc1, loc2;
 513         char *p;
 514         int sig = 0;
 515         sigset_t sigs;
 516
 517         if (!exiting) {
 518                 if (in_dotrap && last_trapsig) {
 519                         sig = last_trapsig;
 520                         exiting_exitstatus = sig + 128;
 521                 } else
 522                         exiting_exitstatus = oexitstatus;
 523         }
 524         exitstatus = oexitstatus = exiting_exitstatus;
 525         if (!setjmp(loc1.loc)) {
 526                 handler = &loc1;
 527                 if ((p = trap[0]) != NULL && *p != '\0') {
 528                         /*
 529                          * Reset evalskip, or the trap on EXIT could be
 530                          * interrupted if the last command was a "return".
 531                          */
 532                         evalskip = 0;
 533                         trap[0] = NULL;
 534                         FORCEINTON;
 535                         evalstring(p, 0);
 536                 }
 537         }
 538         if (!setjmp(loc2.loc)) {
 539                 handler = &loc2;                /* probably unnecessary */
 540                 FORCEINTON;
 541                 flushall();
 542 #if JOBS
 543                 setjobctl(0);
 544 #endif
 545         }
 546         if (sig != 0 && sig != SIGSTOP && sig != SIGTSTP && sig != SIGTTIN &&
 547             sig != SIGTTOU) {
 548                 signal(sig, SIG_DFL);
 549                 sigemptyset(&sigs);
 550                 sigaddset(&sigs, sig);
 551                 sigprocmask(SIG_UNBLOCK, &sigs, NULL);
 552                 kill(getpid(), sig);
 553                 /* If the default action is to ignore, fall back to _exit(). */
 554         }
 555         _exit(exiting_exitstatus);
 556 }