1 /* $NetBSD: trap.c,v 1.35 2011/06/18 21:18:46 christos Exp $ */ 2 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 #include <sys/cdefs.h> 36 #ifndef lint 37 #if 0 38 static char sccsid[] = "@(#)trap.c 8.5 (Berkeley) 6/5/95"; 39 #else 40 __RCSID("$NetBSD: trap.c,v 1.35 2011/06/18 21:18:46 christos Exp $"); 41 #endif 42 #endif /* not lint */ 43 44 #include <signal.h> 45 #include <unistd.h> 46 #include <stdlib.h> 47 48 #include "shell.h" 49 #include "main.h" 50 #include "nodes.h" /* for other headers */ 51 #include "eval.h" 52 #include "jobs.h" 53 #include "show.h" 54 #include "options.h" 55 #include "builtins.h" 56 #include "syntax.h" 57 #include "output.h" 58 #include "memalloc.h" 59 #include "error.h" 60 #include "trap.h" 61 #include "mystring.h" 62 #include "var.h" 63 64 65 /* 66 * Sigmode records the current value of the signal handlers for the various 67 * modes. A value of zero means that the current handler is not known. 68 * S_HARD_IGN indicates that the signal was ignored on entry to the shell, 69 */ 70 71 #define S_DFL 1 /* default signal handling (SIG_DFL) */ 72 #define S_CATCH 2 /* signal is caught */ 73 #define S_IGN 3 /* signal is ignored (SIG_IGN) */ 74 #define S_HARD_IGN 4 /* signal is ignored permenantly */ 75 #define S_RESET 5 /* temporary - to reset a hard ignored sig */ 76 77 78 char *trap[NSIG+1]; /* trap handler commands */ 79 MKINIT char sigmode[NSIG]; /* current value of signal */ 80 volatile char gotsig[NSIG]; /* indicates specified signal received */ 81 int pendingsigs; /* indicates some signal received */ 82 83 static int getsigaction(int, sig_t *); 84 85 /* 86 * return the signal number described by `p' (as a number or a name) 87 * or -1 if it isn't one 88 */ 89 90 static int 91 signame_to_signum(const char *p) 92 { 93 int i; 94 95 if (is_number(p)) 96 return number(p); 97 98 if (strcasecmp(p, "exit") == 0 ) 99 return 0; 100 101 if (strncasecmp(p, "sig", 3) == 0) 102 p += 3; 103 104 for (i = 0; i < NSIG; ++i) 105 if (strcasecmp (p, sys_signame[i]) == 0) 106 return i; 107 return -1; 108 } 109 110 /* 111 * Print a list of valid signal names 112 */ 113 static void 114 printsignals(void) 115 { 116 int n; 117 118 out1str("EXIT "); 119 120 for (n = 1; n < NSIG; n++) { 121 out1fmt("%s", sys_signame[n]); 122 if ((n == NSIG/2) || n == (NSIG - 1)) 123 out1str("\n"); 124 else 125 out1c(' '); 126 } 127 } 128 129 /* 130 * The trap builtin. 131 */ 132 133 int 134 trapcmd(int argc, char **argv) 135 { 136 char *action; 137 char **ap; 138 int signo; 139 140 if (argc <= 1) { 141 for (signo = 0 ; signo <= NSIG ; signo++) 142 if (trap[signo] != NULL) { 143 out1fmt("trap -- "); 144 print_quoted(trap[signo]); 145 out1fmt(" %s\n", 146 (signo) ? sys_signame[signo] : "EXIT"); 147 } 148 return 0; 149 } 150 ap = argv + 1; 151 152 action = NULL; 153 154 if (strcmp(*ap, "--") == 0) 155 if (*++ap == NULL) 156 return 0; 157 158 if (signame_to_signum(*ap) == -1) { 159 if ((*ap)[0] == '-') { 160 if ((*ap)[1] == '\0') 161 ap++; 162 else if ((*ap)[1] == 'l' && (*ap)[2] == '\0') { 163 printsignals(); 164 return 0; 165 } 166 else 167 error("bad option %s\n", *ap); 168 } 169 else 170 action = *ap++; 171 } 172 173 while (*ap) { 174 if (is_number(*ap)) 175 signo = number(*ap); 176 else 177 signo = signame_to_signum(*ap); 178 179 if (signo < 0 || signo > NSIG) 180 error("%s: bad trap", *ap); 181 182 INTOFF; 183 if (action) 184 action = savestr(action); 185 186 if (trap[signo]) 187 ckfree(trap[signo]); 188 189 trap[signo] = action; 190 191 if (signo != 0) 192 setsignal(signo, 0); 193 INTON; 194 ap++; 195 } 196 return 0; 197 } 198 199 200 201 /* 202 * Clear traps on a fork or vfork. 203 * Takes one arg vfork, to tell it to not be destructive of 204 * the parents variables. 205 */ 206 207 void 208 clear_traps(int vforked) 209 { 210 char **tp; 211 212 for (tp = trap ; tp <= &trap[NSIG] ; tp++) { 213 if (*tp && **tp) { /* trap not NULL or SIG_IGN */ 214 INTOFF; 215 if (!vforked) { 216 ckfree(*tp); 217 *tp = NULL; 218 } 219 if (tp != &trap[0]) 220 setsignal(tp - trap, vforked); 221 INTON; 222 } 223 } 224 } 225 226 227 228 /* 229 * Set the signal handler for the specified signal. The routine figures 230 * out what it should be set to. 231 */ 232 233 sig_t 234 setsignal(int signo, int vforked) 235 { 236 int action; 237 sig_t sigact = SIG_DFL, sig; 238 char *t, tsig; 239 240 if ((t = trap[signo]) == NULL) 241 action = S_DFL; 242 else if (*t != '\0') 243 action = S_CATCH; 244 else 245 action = S_IGN; 246 if (rootshell && !vforked && action == S_DFL) { 247 switch (signo) { 248 case SIGINT: 249 if (iflag || minusc || sflag == 0) 250 action = S_CATCH; 251 break; 252 case SIGQUIT: 253 #ifdef DEBUG 254 if (debug) 255 break; 256 #endif 257 /* FALLTHROUGH */ 258 case SIGTERM: 259 if (iflag) 260 action = S_IGN; 261 break; 262 #if JOBS 263 case SIGTSTP: 264 case SIGTTOU: 265 if (mflag) 266 action = S_IGN; 267 break; 268 #endif 269 } 270 } 271 272 t = &sigmode[signo - 1]; 273 tsig = *t; 274 if (tsig == 0) { 275 /* 276 * current setting unknown 277 */ 278 if (!getsigaction(signo, &sigact)) { 279 /* 280 * Pretend it worked; maybe we should give a warning 281 * here, but other shells don't. We don't alter 282 * sigmode, so that we retry every time. 283 */ 284 return 0; 285 } 286 if (sigact == SIG_IGN) { 287 /* 288 * POSIX 3.14.13 states that non-interactive shells 289 * should ignore trap commands for signals that were 290 * ignored upon entry, and leaves the behavior 291 * unspecified for interactive shells. On interactive 292 * shells, or if job control is on, and we have a job 293 * control related signal, we allow the trap to work. 294 * 295 * This change allows us to be POSIX compliant, and 296 * at the same time override the default behavior if 297 * we need to by setting the interactive flag. 298 */ 299 if ((mflag && (signo == SIGTSTP || 300 signo == SIGTTIN || signo == SIGTTOU)) || iflag) { 301 tsig = S_IGN; 302 } else 303 tsig = S_HARD_IGN; 304 } else { 305 tsig = S_RESET; /* force to be set */ 306 } 307 } 308 if (tsig == S_HARD_IGN || tsig == action) 309 return 0; 310 switch (action) { 311 case S_DFL: sigact = SIG_DFL; break; 312 case S_CATCH: sigact = onsig; break; 313 case S_IGN: sigact = SIG_IGN; break; 314 } 315 sig = signal(signo, sigact); 316 if (sig != SIG_ERR) { 317 sigset_t ss; 318 if (!vforked) 319 *t = action; 320 if (action == S_CATCH) 321 (void)siginterrupt(signo, 1); 322 /* 323 * If our parent accidentally blocked signals for 324 * us make sure we unblock them 325 */ 326 (void)sigemptyset(&ss); 327 (void)sigaddset(&ss, signo); 328 (void)sigprocmask(SIG_UNBLOCK, &ss, NULL); 329 } 330 return sig; 331 } 332 333 /* 334 * Return the current setting for sig w/o changing it. 335 */ 336 static int 337 getsigaction(int signo, sig_t *sigact) 338 { 339 struct sigaction sa; 340 341 if (sigaction(signo, (struct sigaction *)0, &sa) == -1) 342 return 0; 343 *sigact = (sig_t) sa.sa_handler; 344 return 1; 345 } 346 347 /* 348 * Ignore a signal. 349 */ 350 351 void 352 ignoresig(int signo, int vforked) 353 { 354 if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) { 355 signal(signo, SIG_IGN); 356 } 357 if (!vforked) 358 sigmode[signo - 1] = S_HARD_IGN; 359 } 360 361 362 #ifdef mkinit 363 INCLUDE <signal.h> 364 INCLUDE "trap.h" 365 366 SHELLPROC { 367 char *sm; 368 369 clear_traps(0); 370 for (sm = sigmode ; sm < sigmode + NSIG ; sm++) { 371 if (*sm == S_IGN) 372 *sm = S_HARD_IGN; 373 } 374 } 375 #endif 376 377 378 379 /* 380 * Signal handler. 381 */ 382 383 void 384 onsig(int signo) 385 { 386 signal(signo, onsig); 387 if (signo == SIGINT && trap[SIGINT] == NULL) { 388 onint(); 389 return; 390 } 391 gotsig[signo - 1] = 1; 392 pendingsigs++; 393 } 394 395 396 397 /* 398 * Called to execute a trap. Perhaps we should avoid entering new trap 399 * handlers while we are executing a trap handler. 400 */ 401 402 void 403 dotrap(void) 404 { 405 int i; 406 int savestatus; 407 408 for (;;) { 409 for (i = 1 ; ; i++) { 410 if (gotsig[i - 1]) 411 break; 412 if (i >= NSIG) 413 goto done; 414 } 415 gotsig[i - 1] = 0; 416 savestatus=exitstatus; 417 evalstring(trap[i], 0); 418 exitstatus=savestatus; 419 } 420 done: 421 pendingsigs = 0; 422 } 423 424 425 426 /* 427 * Controls whether the shell is interactive or not. 428 */ 429 430 431 void 432 setinteractive(int on) 433 { 434 static int is_interactive; 435 436 if (on == is_interactive) 437 return; 438 setsignal(SIGINT, 0); 439 setsignal(SIGQUIT, 0); 440 setsignal(SIGTERM, 0); 441 is_interactive = on; 442 } 443 444 445 446 /* 447 * Called to exit the shell. 448 */ 449 450 void 451 exitshell(int status) 452 { 453 struct jmploc loc1, loc2; 454 char *p; 455 456 TRACE(("pid %d, exitshell(%d)\n", getpid(), status)); 457 if (setjmp(loc1.loc)) { 458 goto l1; 459 } 460 if (setjmp(loc2.loc)) { 461 goto l2; 462 } 463 handler = &loc1; 464 if ((p = trap[0]) != NULL && *p != '\0') { 465 trap[0] = NULL; 466 evalstring(p, 0); 467 } 468 l1: handler = &loc2; /* probably unnecessary */ 469 flushall(); 470 #if JOBS 471 setjobctl(0); 472 #endif 473 l2: _exit(status); 474 /* NOTREACHED */ 475 } 476