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 #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 if (debug) 280 break; 281 #endif 282 action = S_CATCH; 283 break; 284 case SIGTERM: 285 if (rootshell && iflag) 286 action = S_IGN; 287 break; 288 #if JOBS 289 case SIGTSTP: 290 case SIGTTOU: 291 if (rootshell && mflag) 292 action = S_IGN; 293 break; 294 #endif 295 } 296 } 297 298 t = &sigmode[signo]; 299 if (*t == 0) { 300 /* 301 * current setting unknown 302 */ 303 if (!getsigaction(signo, &sigact)) { 304 /* 305 * Pretend it worked; maybe we should give a warning 306 * here, but other shells don't. We don't alter 307 * sigmode, so that we retry every time. 308 */ 309 return; 310 } 311 if (sigact == SIG_IGN) { 312 if (mflag && (signo == SIGTSTP || 313 signo == SIGTTIN || signo == SIGTTOU)) { 314 *t = S_IGN; /* don't hard ignore these */ 315 } else 316 *t = S_HARD_IGN; 317 } else { 318 *t = S_RESET; /* force to be set */ 319 } 320 } 321 if (*t == S_HARD_IGN || *t == action) 322 return; 323 switch (action) { 324 case S_DFL: sigact = SIG_DFL; break; 325 case S_CATCH: sigact = onsig; break; 326 case S_IGN: sigact = SIG_IGN; break; 327 } 328 *t = action; 329 sa.sa_handler = sigact; 330 sa.sa_flags = 0; 331 sigemptyset(&sa.sa_mask); 332 sigaction(signo, &sa, NULL); 333 } 334 335 336 /* 337 * Return the current setting for sig w/o changing it. 338 */ 339 static int 340 getsigaction(int signo, sig_t *sigact) 341 { 342 struct sigaction sa; 343 344 if (sigaction(signo, (struct sigaction *)0, &sa) == -1) 345 return 0; 346 *sigact = (sig_t) sa.sa_handler; 347 return 1; 348 } 349 350 351 /* 352 * Ignore a signal. 353 */ 354 void 355 ignoresig(int signo) 356 { 357 358 if (sigmode[signo] == 0) 359 setsignal(signo); 360 if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) { 361 signal(signo, SIG_IGN); 362 sigmode[signo] = S_IGN; 363 } 364 } 365 366 367 int 368 issigchldtrapped(void) 369 { 370 371 return (trap[SIGCHLD] != NULL && *trap[SIGCHLD] != '\0'); 372 } 373 374 375 /* 376 * Signal handler. 377 */ 378 void 379 onsig(int signo) 380 { 381 382 if (signo == SIGINT && trap[SIGINT] == NULL) { 383 if (suppressint) 384 SET_PENDING_INT; 385 else 386 onint(); 387 return; 388 } 389 390 /* If we are currently in a wait builtin, prepare to break it */ 391 if (signo == SIGINT || signo == SIGQUIT) 392 pendingsig_waitcmd = signo; 393 394 if (trap[signo] != NULL && trap[signo][0] != '\0' && 395 (signo != SIGCHLD || !ignore_sigchld)) { 396 gotsig[signo] = 1; 397 pendingsig = signo; 398 pendingsig_waitcmd = signo; 399 } 400 } 401 402 403 /* 404 * Called to execute a trap. Perhaps we should avoid entering new trap 405 * handlers while we are executing a trap handler. 406 */ 407 void 408 dotrap(void) 409 { 410 struct stackmark smark; 411 int i; 412 int savestatus, prev_evalskip, prev_skipcount; 413 414 in_dotrap++; 415 for (;;) { 416 pendingsig = 0; 417 pendingsig_waitcmd = 0; 418 for (i = 1; i < NSIG; i++) { 419 if (gotsig[i]) { 420 gotsig[i] = 0; 421 if (trap[i]) { 422 /* 423 * Ignore SIGCHLD to avoid infinite 424 * recursion if the trap action does 425 * a fork. 426 */ 427 if (i == SIGCHLD) 428 ignore_sigchld++; 429 430 /* 431 * Backup current evalskip 432 * state and reset it before 433 * executing a trap, so that the 434 * trap is not disturbed by an 435 * ongoing break/continue/return 436 * statement. 437 */ 438 prev_evalskip = evalskip; 439 prev_skipcount = skipcount; 440 evalskip = 0; 441 442 last_trapsig = i; 443 savestatus = exitstatus; 444 setstackmark(&smark); 445 evalstring(stsavestr(trap[i]), 0); 446 popstackmark(&smark); 447 448 /* 449 * If such a command was not 450 * already in progress, allow a 451 * break/continue/return in the 452 * trap action to have an effect 453 * outside of it. 454 */ 455 if (evalskip == 0 || 456 prev_evalskip != 0) { 457 evalskip = prev_evalskip; 458 skipcount = prev_skipcount; 459 exitstatus = savestatus; 460 } 461 462 if (i == SIGCHLD) 463 ignore_sigchld--; 464 } 465 break; 466 } 467 } 468 if (i >= NSIG) 469 break; 470 } 471 in_dotrap--; 472 } 473 474 475 void 476 trap_init(void) 477 { 478 setsignal(SIGINT); 479 setsignal(SIGQUIT); 480 } 481 482 483 /* 484 * Controls whether the shell is interactive or not based on iflag. 485 */ 486 void 487 setinteractive(void) 488 { 489 setsignal(SIGTERM); 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 FORCEINTON; 531 evalstring(p, 0); 532 } 533 } 534 if (!setjmp(loc2.loc)) { 535 handler = &loc2; /* probably unnecessary */ 536 FORCEINTON; 537 flushall(); 538 #if JOBS 539 setjobctl(0); 540 #endif 541 #ifndef NO_HISTORY 542 histsave(); 543 #endif 544 } 545 if (sig != 0 && sig != SIGSTOP && sig != SIGTSTP && sig != SIGTTIN && 546 sig != SIGTTOU) { 547 signal(sig, SIG_DFL); 548 sigemptyset(&sigs); 549 sigaddset(&sigs, sig); 550 sigprocmask(SIG_UNBLOCK, &sigs, NULL); 551 kill(getpid(), sig); 552 /* If the default action is to ignore, fall back to _exit(). */ 553 } 554 _exit(exiting_exitstatus); 555 } 556