1 /* $NetBSD: trap.c,v 1.34 2008/02/15 17:26:06 matt 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 1.34 2008/02/15 17:26:06 matt 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 "syntax.h" 56 #include "output.h" 57 #include "memalloc.h" 58 #include "error.h" 59 #include "trap.h" 60 #include "mystring.h" 61 #include "var.h" 62 63 64 /* 65 * Sigmode records the current value of the signal handlers for the various 66 * modes. A value of zero means that the current handler is not known. 67 * S_HARD_IGN indicates that the signal was ignored on entry to the shell, 68 */ 69 70 #define S_DFL 1 /* default signal handling (SIG_DFL) */ 71 #define S_CATCH 2 /* signal is caught */ 72 #define S_IGN 3 /* signal is ignored (SIG_IGN) */ 73 #define S_HARD_IGN 4 /* signal is ignored permenantly */ 74 #define S_RESET 5 /* temporary - to reset a hard ignored sig */ 75 76 77 char *trap[NSIG+1]; /* trap handler commands */ 78 MKINIT char sigmode[NSIG]; /* current value of signal */ 79 volatile char gotsig[NSIG]; /* indicates specified signal received */ 80 int pendingsigs; /* indicates some signal received */ 81 82 static int getsigaction(int, sig_t *); 83 84 /* 85 * return the signal number described by `p' (as a number or a name) 86 * or -1 if it isn't one 87 */ 88 89 static int 90 signame_to_signum(const char *p) 91 { 92 int i; 93 94 if (is_number(p)) 95 return number(p); 96 97 if (strcasecmp(p, "exit") == 0 ) 98 return 0; 99 100 if (strncasecmp(p, "sig", 3) == 0) 101 p += 3; 102 103 for (i = 0; i < NSIG; ++i) 104 if (strcasecmp (p, sys_signame[i]) == 0) 105 return i; 106 return -1; 107 } 108 109 /* 110 * Print a list of valid signal names 111 */ 112 static void 113 printsignals(void) 114 { 115 int n; 116 117 out1str("EXIT "); 118 119 for (n = 1; n < NSIG; n++) { 120 out1fmt("%s", sys_signame[n]); 121 if ((n == NSIG/2) || n == (NSIG - 1)) 122 out1str("\n"); 123 else 124 out1c(' '); 125 } 126 } 127 128 /* 129 * The trap builtin. 130 */ 131 132 int 133 trapcmd(int argc, char **argv) 134 { 135 char *action; 136 char **ap; 137 int signo; 138 139 if (argc <= 1) { 140 for (signo = 0 ; signo <= NSIG ; signo++) 141 if (trap[signo] != NULL) { 142 out1fmt("trap -- "); 143 print_quoted(trap[signo]); 144 out1fmt(" %s\n", 145 (signo) ? sys_signame[signo] : "EXIT"); 146 } 147 return 0; 148 } 149 ap = argv + 1; 150 151 action = NULL; 152 153 if (strcmp(*ap, "--") == 0) 154 if (*++ap == NULL) 155 return 0; 156 157 if (signame_to_signum(*ap) == -1) { 158 if ((*ap)[0] == '-') { 159 if ((*ap)[1] == '\0') 160 ap++; 161 else if ((*ap)[1] == 'l' && (*ap)[2] == '\0') { 162 printsignals(); 163 return 0; 164 } 165 else 166 error("bad option %s\n", *ap); 167 } 168 else 169 action = *ap++; 170 } 171 172 while (*ap) { 173 if (is_number(*ap)) 174 signo = number(*ap); 175 else 176 signo = signame_to_signum(*ap); 177 178 if (signo < 0 || signo > NSIG) 179 error("%s: bad trap", *ap); 180 181 INTOFF; 182 if (action) 183 action = savestr(action); 184 185 if (trap[signo]) 186 ckfree(trap[signo]); 187 188 trap[signo] = action; 189 190 if (signo != 0) 191 setsignal(signo, 0); 192 INTON; 193 ap++; 194 } 195 return 0; 196 } 197 198 199 200 /* 201 * Clear traps on a fork or vfork. 202 * Takes one arg vfork, to tell it to not be destructive of 203 * the parents variables. 204 */ 205 206 void 207 clear_traps(int vforked) 208 { 209 char **tp; 210 211 for (tp = trap ; tp <= &trap[NSIG] ; tp++) { 212 if (*tp && **tp) { /* trap not NULL or SIG_IGN */ 213 INTOFF; 214 if (!vforked) { 215 ckfree(*tp); 216 *tp = NULL; 217 } 218 if (tp != &trap[0]) 219 setsignal(tp - trap, vforked); 220 INTON; 221 } 222 } 223 } 224 225 226 227 /* 228 * Set the signal handler for the specified signal. The routine figures 229 * out what it should be set to. 230 */ 231 232 sig_t 233 setsignal(int signo, int vforked) 234 { 235 int action; 236 sig_t sigact = SIG_DFL, sig; 237 char *t, tsig; 238 239 if ((t = trap[signo]) == NULL) 240 action = S_DFL; 241 else if (*t != '\0') 242 action = S_CATCH; 243 else 244 action = S_IGN; 245 if (rootshell && !vforked && action == S_DFL) { 246 switch (signo) { 247 case SIGINT: 248 if (iflag || minusc || sflag == 0) 249 action = S_CATCH; 250 break; 251 case SIGQUIT: 252 #ifdef DEBUG 253 if (debug) 254 break; 255 #endif 256 /* FALLTHROUGH */ 257 case SIGTERM: 258 if (iflag) 259 action = S_IGN; 260 break; 261 #if JOBS 262 case SIGTSTP: 263 case SIGTTOU: 264 if (mflag) 265 action = S_IGN; 266 break; 267 #endif 268 } 269 } 270 271 t = &sigmode[signo - 1]; 272 tsig = *t; 273 if (tsig == 0) { 274 /* 275 * current setting unknown 276 */ 277 if (!getsigaction(signo, &sigact)) { 278 /* 279 * Pretend it worked; maybe we should give a warning 280 * here, but other shells don't. We don't alter 281 * sigmode, so that we retry every time. 282 */ 283 return 0; 284 } 285 if (sigact == SIG_IGN) { 286 /* 287 * POSIX 3.14.13 states that non-interactive shells 288 * should ignore trap commands for signals that were 289 * ignored upon entry, and leaves the behavior 290 * unspecified for interactive shells. On interactive 291 * shells, or if job control is on, and we have a job 292 * control related signal, we allow the trap to work. 293 * 294 * This change allows us to be POSIX compliant, and 295 * at the same time override the default behavior if 296 * we need to by setting the interactive flag. 297 */ 298 if ((mflag && (signo == SIGTSTP || 299 signo == SIGTTIN || signo == SIGTTOU)) || iflag) { 300 tsig = S_IGN; 301 } else 302 tsig = S_HARD_IGN; 303 } else { 304 tsig = S_RESET; /* force to be set */ 305 } 306 } 307 if (tsig == S_HARD_IGN || tsig == action) 308 return 0; 309 switch (action) { 310 case S_DFL: sigact = SIG_DFL; break; 311 case S_CATCH: sigact = onsig; break; 312 case S_IGN: sigact = SIG_IGN; break; 313 } 314 sig = signal(signo, sigact); 315 if (sig != SIG_ERR) { 316 sigset_t ss; 317 if (!vforked) 318 *t = action; 319 if (action == S_CATCH) 320 (void)siginterrupt(signo, 1); 321 /* 322 * If our parent accidentally blocked signals for 323 * us make sure we unblock them 324 */ 325 (void)sigemptyset(&ss); 326 (void)sigaddset(&ss, signo); 327 (void)sigprocmask(SIG_UNBLOCK, &ss, NULL); 328 } 329 return sig; 330 } 331 332 /* 333 * Return the current setting for sig w/o changing it. 334 */ 335 static int 336 getsigaction(int signo, sig_t *sigact) 337 { 338 struct sigaction sa; 339 340 if (sigaction(signo, (struct sigaction *)0, &sa) == -1) 341 return 0; 342 *sigact = (sig_t) sa.sa_handler; 343 return 1; 344 } 345 346 /* 347 * Ignore a signal. 348 */ 349 350 void 351 ignoresig(int signo, int vforked) 352 { 353 if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) { 354 signal(signo, SIG_IGN); 355 } 356 if (!vforked) 357 sigmode[signo - 1] = S_HARD_IGN; 358 } 359 360 361 #ifdef mkinit 362 INCLUDE <signal.h> 363 INCLUDE "trap.h" 364 365 SHELLPROC { 366 char *sm; 367 368 clear_traps(0); 369 for (sm = sigmode ; sm < sigmode + NSIG ; sm++) { 370 if (*sm == S_IGN) 371 *sm = S_HARD_IGN; 372 } 373 } 374 #endif 375 376 377 378 /* 379 * Signal handler. 380 */ 381 382 void 383 onsig(int signo) 384 { 385 signal(signo, onsig); 386 if (signo == SIGINT && trap[SIGINT] == NULL) { 387 onint(); 388 return; 389 } 390 gotsig[signo - 1] = 1; 391 pendingsigs++; 392 } 393 394 395 396 /* 397 * Called to execute a trap. Perhaps we should avoid entering new trap 398 * handlers while we are executing a trap handler. 399 */ 400 401 void 402 dotrap(void) 403 { 404 int i; 405 int savestatus; 406 407 for (;;) { 408 for (i = 1 ; ; i++) { 409 if (gotsig[i - 1]) 410 break; 411 if (i >= NSIG) 412 goto done; 413 } 414 gotsig[i - 1] = 0; 415 savestatus=exitstatus; 416 evalstring(trap[i], 0); 417 exitstatus=savestatus; 418 } 419 done: 420 pendingsigs = 0; 421 } 422 423 424 425 /* 426 * Controls whether the shell is interactive or not. 427 */ 428 429 430 void 431 setinteractive(int on) 432 { 433 static int is_interactive; 434 435 if (on == is_interactive) 436 return; 437 setsignal(SIGINT, 0); 438 setsignal(SIGQUIT, 0); 439 setsignal(SIGTERM, 0); 440 is_interactive = on; 441 } 442 443 444 445 /* 446 * Called to exit the shell. 447 */ 448 449 void 450 exitshell(int status) 451 { 452 struct jmploc loc1, loc2; 453 char *p; 454 455 TRACE(("pid %d, exitshell(%d)\n", getpid(), status)); 456 if (setjmp(loc1.loc)) { 457 goto l1; 458 } 459 if (setjmp(loc2.loc)) { 460 goto l2; 461 } 462 handler = &loc1; 463 if ((p = trap[0]) != NULL && *p != '\0') { 464 trap[0] = NULL; 465 evalstring(p, 0); 466 } 467 l1: handler = &loc2; /* probably unnecessary */ 468 flushall(); 469 #if JOBS 470 setjobctl(0); 471 #endif 472 l2: _exit(status); 473 /* NOTREACHED */ 474 } 475