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 #endif /* not lint */ 37 #include <sys/cdefs.h> 38 #include <signal.h> 39 #include <unistd.h> 40 #include <stdlib.h> 41 42 #include "shell.h" 43 #include "main.h" 44 #include "nodes.h" /* for other headers */ 45 #include "eval.h" 46 #include "jobs.h" 47 #include "show.h" 48 #include "options.h" 49 #include "syntax.h" 50 #include "output.h" 51 #include "memalloc.h" 52 #include "error.h" 53 #include "trap.h" 54 #include "mystring.h" 55 #include "builtins.h" 56 #ifndef NO_HISTORY 57 #include "myhistedit.h" 58 #endif 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 if (debug) 275 break; 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 } 291 } 292 293 t = &sigmode[signo]; 294 if (*t == 0) { 295 /* 296 * current setting unknown 297 */ 298 if (!getsigaction(signo, &sigact)) { 299 /* 300 * Pretend it worked; maybe we should give a warning 301 * here, but other shells don't. We don't alter 302 * sigmode, so that we retry every time. 303 */ 304 return; 305 } 306 if (sigact == SIG_IGN) { 307 if (mflag && (signo == SIGTSTP || 308 signo == SIGTTIN || signo == SIGTTOU)) { 309 *t = S_IGN; /* don't hard ignore these */ 310 } else 311 *t = S_HARD_IGN; 312 } else { 313 *t = S_RESET; /* force to be set */ 314 } 315 } 316 if (*t == S_HARD_IGN || *t == action) 317 return; 318 switch (action) { 319 case S_DFL: sigact = SIG_DFL; break; 320 case S_CATCH: sigact = onsig; break; 321 case S_IGN: sigact = SIG_IGN; break; 322 } 323 *t = action; 324 sa.sa_handler = sigact; 325 sa.sa_flags = 0; 326 sigemptyset(&sa.sa_mask); 327 sigaction(signo, &sa, NULL); 328 } 329 330 331 /* 332 * Return the current setting for sig w/o changing it. 333 */ 334 static int 335 getsigaction(int signo, sig_t *sigact) 336 { 337 struct sigaction sa; 338 339 if (sigaction(signo, (struct sigaction *)0, &sa) == -1) 340 return 0; 341 *sigact = (sig_t) sa.sa_handler; 342 return 1; 343 } 344 345 346 /* 347 * Ignore a signal. 348 */ 349 void 350 ignoresig(int signo) 351 { 352 353 if (sigmode[signo] == 0) 354 setsignal(signo); 355 if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) { 356 signal(signo, SIG_IGN); 357 sigmode[signo] = S_IGN; 358 } 359 } 360 361 362 int 363 issigchldtrapped(void) 364 { 365 366 return (trap[SIGCHLD] != NULL && *trap[SIGCHLD] != '\0'); 367 } 368 369 370 /* 371 * Signal handler. 372 */ 373 void 374 onsig(int signo) 375 { 376 377 if (signo == SIGINT && trap[SIGINT] == NULL) { 378 if (suppressint) 379 SET_PENDING_INT; 380 else 381 onint(); 382 return; 383 } 384 385 /* If we are currently in a wait builtin, prepare to break it */ 386 if (signo == SIGINT || signo == SIGQUIT) 387 pendingsig_waitcmd = signo; 388 389 if (trap[signo] != NULL && trap[signo][0] != '\0' && 390 (signo != SIGCHLD || !ignore_sigchld)) { 391 gotsig[signo] = 1; 392 pendingsig = signo; 393 pendingsig_waitcmd = signo; 394 } 395 } 396 397 398 /* 399 * Called to execute a trap. Perhaps we should avoid entering new trap 400 * handlers while we are executing a trap handler. 401 */ 402 void 403 dotrap(void) 404 { 405 struct stackmark smark; 406 int i; 407 int savestatus, prev_evalskip, prev_skipcount; 408 409 in_dotrap++; 410 for (;;) { 411 pendingsig = 0; 412 pendingsig_waitcmd = 0; 413 for (i = 1; i < NSIG; i++) { 414 if (gotsig[i]) { 415 gotsig[i] = 0; 416 if (trap[i]) { 417 /* 418 * Ignore SIGCHLD to avoid infinite 419 * recursion if the trap action does 420 * a fork. 421 */ 422 if (i == SIGCHLD) 423 ignore_sigchld++; 424 425 /* 426 * Backup current evalskip 427 * state and reset it before 428 * executing a trap, so that the 429 * trap is not disturbed by an 430 * ongoing break/continue/return 431 * statement. 432 */ 433 prev_evalskip = evalskip; 434 prev_skipcount = skipcount; 435 evalskip = 0; 436 437 last_trapsig = i; 438 savestatus = exitstatus; 439 setstackmark(&smark); 440 evalstring(stsavestr(trap[i]), 0); 441 popstackmark(&smark); 442 443 /* 444 * If such a command was not 445 * already in progress, allow a 446 * break/continue/return in the 447 * trap action to have an effect 448 * outside of it. 449 */ 450 if (evalskip == 0 || 451 prev_evalskip != 0) { 452 evalskip = prev_evalskip; 453 skipcount = prev_skipcount; 454 exitstatus = savestatus; 455 } 456 457 if (i == SIGCHLD) 458 ignore_sigchld--; 459 } 460 break; 461 } 462 } 463 if (i >= NSIG) 464 break; 465 } 466 in_dotrap--; 467 } 468 469 470 void 471 trap_init(void) 472 { 473 setsignal(SIGINT); 474 setsignal(SIGQUIT); 475 } 476 477 478 /* 479 * Controls whether the shell is interactive or not based on iflag. 480 */ 481 void 482 setinteractive(void) 483 { 484 setsignal(SIGTERM); 485 } 486 487 488 /* 489 * Called to exit the shell. 490 */ 491 void 492 exitshell(int status) 493 { 494 TRACE(("exitshell(%d) pid=%d\n", status, getpid())); 495 exiting = 1; 496 exiting_exitstatus = status; 497 exitshell_savedstatus(); 498 } 499 500 void 501 exitshell_savedstatus(void) 502 { 503 struct jmploc loc1, loc2; 504 char *p; 505 int sig = 0; 506 sigset_t sigs; 507 508 if (!exiting) { 509 if (in_dotrap && last_trapsig) { 510 sig = last_trapsig; 511 exiting_exitstatus = sig + 128; 512 } else 513 exiting_exitstatus = oexitstatus; 514 } 515 exitstatus = oexitstatus = exiting_exitstatus; 516 if (!setjmp(loc1.loc)) { 517 handler = &loc1; 518 if ((p = trap[0]) != NULL && *p != '\0') { 519 /* 520 * Reset evalskip, or the trap on EXIT could be 521 * interrupted if the last command was a "return". 522 */ 523 evalskip = 0; 524 trap[0] = NULL; 525 FORCEINTON; 526 evalstring(p, 0); 527 } 528 } 529 if (!setjmp(loc2.loc)) { 530 handler = &loc2; /* probably unnecessary */ 531 FORCEINTON; 532 flushall(); 533 #if JOBS 534 setjobctl(0); 535 #endif 536 #ifndef NO_HISTORY 537 histsave(); 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 } 551