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 364919 2020-08-28 15:35:45Z jilles $"); 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 #ifndef NO_HISTORY 62 #include "myhistedit.h" 63 #endif 64 65 66 /* 67 * Sigmode records the current value of the signal handlers for the various 68 * modes. A value of zero means that the current handler is not known. 69 * S_HARD_IGN indicates that the signal was ignored on entry to the shell, 70 */ 71 72 #define S_DFL 1 /* default signal handling (SIG_DFL) */ 73 #define S_CATCH 2 /* signal is caught */ 74 #define S_IGN 3 /* signal is ignored (SIG_IGN) */ 75 #define S_HARD_IGN 4 /* signal is ignored permanently */ 76 #define S_RESET 5 /* temporary - to reset a hard ignored sig */ 77 78 79 static char sigmode[NSIG]; /* current value of signal */ 80 volatile sig_atomic_t pendingsig; /* indicates some signal received */ 81 volatile sig_atomic_t pendingsig_waitcmd; /* indicates wait builtin should be interrupted */ 82 static int in_dotrap; /* do we execute in a trap handler? */ 83 static char *volatile trap[NSIG]; /* trap handler commands */ 84 static volatile sig_atomic_t gotsig[NSIG]; 85 /* indicates specified signal received */ 86 static int ignore_sigchld; /* Used while handling SIGCHLD traps. */ 87 static int last_trapsig; 88 89 static int exiting; /* exitshell() has been called */ 90 static int exiting_exitstatus; /* value passed to exitshell() */ 91 92 static int getsigaction(int, sig_t *); 93 94 95 /* 96 * Map a string to a signal number. 97 * 98 * Note: the signal number may exceed NSIG. 99 */ 100 static int 101 sigstring_to_signum(char *sig) 102 { 103 104 if (is_number(sig)) { 105 int signo; 106 107 signo = atoi(sig); 108 return ((signo >= 0 && signo < NSIG) ? signo : (-1)); 109 } else if (strcasecmp(sig, "EXIT") == 0) { 110 return (0); 111 } else { 112 int n; 113 114 if (strncasecmp(sig, "SIG", 3) == 0) 115 sig += 3; 116 for (n = 1; n < sys_nsig; n++) 117 if (sys_signame[n] && 118 strcasecmp(sys_signame[n], sig) == 0) 119 return (n); 120 } 121 return (-1); 122 } 123 124 125 /* 126 * Print a list of valid signal names. 127 */ 128 static void 129 printsignals(void) 130 { 131 int n, outlen; 132 133 outlen = 0; 134 for (n = 1; n < sys_nsig; n++) { 135 if (sys_signame[n]) { 136 out1fmt("%s", sys_signame[n]); 137 outlen += strlen(sys_signame[n]); 138 } else { 139 out1fmt("%d", n); 140 outlen += 3; /* good enough */ 141 } 142 ++outlen; 143 if (outlen > 71 || n == sys_nsig - 1) { 144 out1str("\n"); 145 outlen = 0; 146 } else { 147 out1c(' '); 148 } 149 } 150 } 151 152 153 /* 154 * The trap builtin. 155 */ 156 int 157 trapcmd(int argc __unused, char **argv) 158 { 159 char *action; 160 int signo; 161 int errors = 0; 162 int i; 163 164 while ((i = nextopt("l")) != '\0') { 165 switch (i) { 166 case 'l': 167 printsignals(); 168 return (0); 169 } 170 } 171 argv = argptr; 172 173 if (*argv == NULL) { 174 for (signo = 0 ; signo < sys_nsig ; signo++) { 175 if (signo < NSIG && trap[signo] != NULL) { 176 out1str("trap -- "); 177 out1qstr(trap[signo]); 178 if (signo == 0) { 179 out1str(" EXIT\n"); 180 } else if (sys_signame[signo]) { 181 out1fmt(" %s\n", sys_signame[signo]); 182 } else { 183 out1fmt(" %d\n", signo); 184 } 185 } 186 } 187 return 0; 188 } 189 action = NULL; 190 if (*argv && !is_number(*argv)) { 191 if (strcmp(*argv, "-") == 0) 192 argv++; 193 else { 194 action = *argv; 195 argv++; 196 } 197 } 198 for (; *argv; argv++) { 199 if ((signo = sigstring_to_signum(*argv)) == -1) { 200 warning("bad signal %s", *argv); 201 errors = 1; 202 continue; 203 } 204 INTOFF; 205 if (action) 206 action = savestr(action); 207 if (trap[signo]) 208 ckfree(trap[signo]); 209 trap[signo] = action; 210 if (signo != 0) 211 setsignal(signo); 212 INTON; 213 } 214 return errors; 215 } 216 217 218 /* 219 * Clear traps on a fork. 220 */ 221 void 222 clear_traps(void) 223 { 224 char *volatile *tp; 225 226 for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) { 227 if (*tp && **tp) { /* trap not NULL or SIG_IGN */ 228 INTOFF; 229 ckfree(*tp); 230 *tp = NULL; 231 if (tp != &trap[0]) 232 setsignal(tp - trap); 233 INTON; 234 } 235 } 236 } 237 238 239 /* 240 * Check if we have any traps enabled. 241 */ 242 int 243 have_traps(void) 244 { 245 char *volatile *tp; 246 247 for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) { 248 if (*tp && **tp) /* trap not NULL or SIG_IGN */ 249 return 1; 250 } 251 return 0; 252 } 253 254 /* 255 * Set the signal handler for the specified signal. The routine figures 256 * out what it should be set to. 257 */ 258 void 259 setsignal(int signo) 260 { 261 int action; 262 sig_t sigact = SIG_DFL; 263 struct sigaction sa; 264 char *t; 265 266 if ((t = trap[signo]) == NULL) 267 action = S_DFL; 268 else if (*t != '\0') 269 action = S_CATCH; 270 else 271 action = S_IGN; 272 if (action == S_DFL) { 273 switch (signo) { 274 case SIGINT: 275 action = S_CATCH; 276 break; 277 case SIGQUIT: 278 #ifdef DEBUG 279 { 280 extern int debug; 281 282 if (debug) 283 break; 284 } 285 #endif 286 action = S_CATCH; 287 break; 288 case SIGTERM: 289 if (rootshell && iflag) 290 action = S_IGN; 291 break; 292 #if JOBS 293 case SIGTSTP: 294 case SIGTTOU: 295 if (rootshell && mflag) 296 action = S_IGN; 297 break; 298 #endif 299 } 300 } 301 302 t = &sigmode[signo]; 303 if (*t == 0) { 304 /* 305 * current setting unknown 306 */ 307 if (!getsigaction(signo, &sigact)) { 308 /* 309 * Pretend it worked; maybe we should give a warning 310 * here, but other shells don't. We don't alter 311 * sigmode, so that we retry every time. 312 */ 313 return; 314 } 315 if (sigact == SIG_IGN) { 316 if (mflag && (signo == SIGTSTP || 317 signo == SIGTTIN || signo == SIGTTOU)) { 318 *t = S_IGN; /* don't hard ignore these */ 319 } else 320 *t = S_HARD_IGN; 321 } else { 322 *t = S_RESET; /* force to be set */ 323 } 324 } 325 if (*t == S_HARD_IGN || *t == action) 326 return; 327 switch (action) { 328 case S_DFL: sigact = SIG_DFL; break; 329 case S_CATCH: sigact = onsig; break; 330 case S_IGN: sigact = SIG_IGN; break; 331 } 332 *t = action; 333 sa.sa_handler = sigact; 334 sa.sa_flags = 0; 335 sigemptyset(&sa.sa_mask); 336 sigaction(signo, &sa, NULL); 337 } 338 339 340 /* 341 * Return the current setting for sig w/o changing it. 342 */ 343 static int 344 getsigaction(int signo, sig_t *sigact) 345 { 346 struct sigaction sa; 347 348 if (sigaction(signo, (struct sigaction *)0, &sa) == -1) 349 return 0; 350 *sigact = (sig_t) sa.sa_handler; 351 return 1; 352 } 353 354 355 /* 356 * Ignore a signal. 357 */ 358 void 359 ignoresig(int signo) 360 { 361 362 if (sigmode[signo] == 0) 363 setsignal(signo); 364 if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) { 365 signal(signo, SIG_IGN); 366 sigmode[signo] = S_IGN; 367 } 368 } 369 370 371 int 372 issigchldtrapped(void) 373 { 374 375 return (trap[SIGCHLD] != NULL && *trap[SIGCHLD] != '\0'); 376 } 377 378 379 /* 380 * Signal handler. 381 */ 382 void 383 onsig(int signo) 384 { 385 386 if (signo == SIGINT && trap[SIGINT] == NULL) { 387 if (suppressint) 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 struct stackmark smark; 415 int i; 416 int savestatus, prev_evalskip, prev_skipcount; 417 418 in_dotrap++; 419 for (;;) { 420 pendingsig = 0; 421 pendingsig_waitcmd = 0; 422 for (i = 1; i < NSIG; i++) { 423 if (gotsig[i]) { 424 gotsig[i] = 0; 425 if (trap[i]) { 426 /* 427 * Ignore SIGCHLD to avoid infinite 428 * recursion if the trap action does 429 * a fork. 430 */ 431 if (i == SIGCHLD) 432 ignore_sigchld++; 433 434 /* 435 * Backup current evalskip 436 * state and reset it before 437 * executing a trap, so that the 438 * trap is not disturbed by an 439 * ongoing break/continue/return 440 * statement. 441 */ 442 prev_evalskip = evalskip; 443 prev_skipcount = skipcount; 444 evalskip = 0; 445 446 last_trapsig = i; 447 savestatus = exitstatus; 448 setstackmark(&smark); 449 evalstring(stsavestr(trap[i]), 0); 450 popstackmark(&smark); 451 452 /* 453 * If such a command was not 454 * already in progress, allow a 455 * break/continue/return in the 456 * trap action to have an effect 457 * outside of it. 458 */ 459 if (evalskip == 0 || 460 prev_evalskip != 0) { 461 evalskip = prev_evalskip; 462 skipcount = prev_skipcount; 463 exitstatus = savestatus; 464 } 465 466 if (i == SIGCHLD) 467 ignore_sigchld--; 468 } 469 break; 470 } 471 } 472 if (i >= NSIG) 473 break; 474 } 475 in_dotrap--; 476 } 477 478 479 void 480 trap_init(void) 481 { 482 setsignal(SIGINT); 483 setsignal(SIGQUIT); 484 } 485 486 487 /* 488 * Controls whether the shell is interactive or not based on iflag. 489 */ 490 void 491 setinteractive(void) 492 { 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 } 557