bin/sh/trap.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Kenneth Almquist.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * @(#)trap.c   8.5 (Berkeley) 6/5/95
  37  * $FreeBSD: src/bin/sh/trap.c,v 1.32 2006/04/17 17:55:11 schweikh Exp $
  38  * $DragonFly: src/bin/sh/trap.c,v 1.5 2007/01/14 07:38:27 pavalos Exp $
  39  */
  40
  41 #include <signal.h>
  42 #include <unistd.h>
  43 #include <stdlib.h>
  44
  45 #include "shell.h"
  46 #include "main.h"
  47 #include "nodes.h"      /* for other headers */
  48 #include "eval.h"
  49 #include "jobs.h"
  50 #include "show.h"
  51 #include "options.h"
  52 #include "syntax.h"
  53 #include "output.h"
  54 #include "memalloc.h"
  55 #include "error.h"
  56 #include "trap.h"
  57 #include "mystring.h"
  58 #include "myhistedit.h"
  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 MKINIT char sigmode[NSIG];      /* current value of signal */
  75 int pendingsigs;                /* indicates some signal received */
  76 int in_dotrap;                  /* do we execute in a trap handler? */
  77 static char *volatile trap[NSIG];       /* trap handler commands */
  78 static volatile sig_atomic_t gotsig[NSIG];
  79                                 /* indicates specified signal received */
  80 static int ignore_sigchld;      /* Used while handling SIGCHLD traps. */
  81 volatile sig_atomic_t gotwinch;
  82
  83 static int getsigaction(int, sig_t *);
  84
  85
  86 /*
  87  * Map a string to a signal number.
  88  *
  89  * Note: the signal number may exceed NSIG.
  90  */
  91 static int
  92 sigstring_to_signum(char *sig)
  93 {
  94
  95         if (is_number(sig)) {
  96                 int signo;
  97
  98                 signo = atoi(sig);
  99                 return ((signo >= 0 && signo < NSIG) ? signo : (-1));
 100         } else if (strcasecmp(sig, "exit") == 0) {
 101                 return (0);
 102         } else {
 103                 int n;
 104
 105                 if (strncasecmp(sig, "sig", 3) == 0)
 106                         sig += 3;
 107                 for (n = 1; n < sys_nsig; n++)
 108                         if (sys_signame[n] &&
 109                             strcasecmp(sys_signame[n], sig) == 0)
 110                                 return (n);
 111         }
 112         return (-1);
 113 }
 114
 115
 116 /*
 117  * Print a list of valid signal names.
 118  */
 119 static void
 120 printsignals(void)
 121 {
 122         int n, outlen;
 123
 124         outlen = 0;
 125         for (n = 1; n < sys_nsig; n++) {
 126                 if (sys_signame[n]) {
 127                         out1fmt("%s", sys_signame[n]);
 128                         outlen += strlen(sys_signame[n]);
 129                 } else {
 130                         out1fmt("%d", n);
 131                         outlen += 3;    /* good enough */
 132                 }
 133                 ++outlen;
 134                 if (outlen > 70 || n == sys_nsig - 1) {
 135                         out1str("\n");
 136                         outlen = 0;
 137                 } else {
 138                         out1c(' ');
 139                 }
 140         }
 141 }
 142
 143
 144 /*
 145  * The trap builtin.
 146  */
 147 int
 148 trapcmd(int argc, char **argv)
 149 {
 150         char *action;
 151         int signo;
 152
 153         if (argc <= 1) {
 154                 for (signo = 0 ; signo < sys_nsig ; signo++) {
 155                         if (signo < NSIG && trap[signo] != NULL) {
 156                                 out1str("trap -- ");
 157                                 out1qstr(trap[signo]);
 158                                 if (signo == 0) {
 159                                         out1str(" exit\n");
 160                                 } else if (sys_signame[signo]) {
 161                                         out1fmt(" %s\n", sys_signame[signo]);
 162                                 } else {
 163                                         out1fmt(" %d\n", signo);
 164                                 }
 165                         }
 166                 }
 167                 return 0;
 168         }
 169         action = NULL;
 170         if (*++argv && strcmp(*argv, "--") == 0)
 171                 argv++;
 172         if (*argv && sigstring_to_signum(*argv) == -1) {
 173                 if ((*argv)[0] != '-') {
 174                         action = *argv;
 175                         argv++;
 176                 } else if ((*argv)[1] == '\0') {
 177                         argv++;
 178                 } else if ((*argv)[1] == 'l' && (*argv)[2] == '\0') {
 179                         printsignals();
 180                         return 0;
 181                 } else {
 182                         error("bad option %s", *argv);
 183                 }
 184         }
 185         while (*argv) {
 186                 if ((signo = sigstring_to_signum(*argv)) == -1)
 187                         error("bad signal %s", *argv);
 188                 INTOFF;
 189                 if (action)
 190                         action = savestr(action);
 191                 if (trap[signo])
 192                         ckfree(trap[signo]);
 193                 trap[signo] = action;
 194                 if (signo != 0)
 195                         setsignal(signo);
 196                 INTON;
 197                 argv++;
 198         }
 199         return 0;
 200 }
 201
 202
 203 /*
 204  * Clear traps on a fork.
 205  */
 206 void
 207 clear_traps(void)
 208 {
 209         char *volatile *tp;
 210
 211         for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
 212                 if (*tp && **tp) {      /* trap not NULL or SIG_IGN */
 213                         INTOFF;
 214                         ckfree(*tp);
 215                         *tp = NULL;
 216                         if (tp != &trap[0])
 217                                 setsignal(tp - trap);
 218                         INTON;
 219                 }
 220         }
 221 }
 222
 223
 224 /*
 225  * Set the signal handler for the specified signal.  The routine figures
 226  * out what it should be set to.
 227  */
 228 void
 229 setsignal(int signo)
 230 {
 231         int action;
 232         sig_t sig, sigact = SIG_DFL;
 233         char *t;
 234
 235         if ((t = trap[signo]) == NULL)
 236                 action = S_DFL;
 237         else if (*t != '\0')
 238                 action = S_CATCH;
 239         else
 240                 action = S_IGN;
 241         if (action == S_DFL) {
 242                 switch (signo) {
 243                 case SIGINT:
 244                         action = S_CATCH;
 245                         break;
 246                 case SIGQUIT:
 247 #ifdef DEBUG
 248                         {
 249                         extern int debug;
 250
 251                         if (debug)
 252                                 break;
 253                         }
 254 #endif
 255                         action = S_CATCH;
 256                         break;
 257                 case SIGTERM:
 258                         if (rootshell && iflag)
 259                                 action = S_IGN;
 260                         break;
 261 #if JOBS
 262                 case SIGTSTP:
 263                 case SIGTTOU:
 264                         if (rootshell && mflag)
 265                                 action = S_IGN;
 266                         break;
 267 #endif
 268 #ifndef NO_HISTORY
 269                 case SIGWINCH:
 270                         if (rootshell && iflag)
 271                                 action = S_CATCH;
 272                         break;
 273 #endif
 274                 }
 275         }
 276
 277         t = &sigmode[signo];
 278         if (*t == 0) {
 279                 /*
 280                  * current setting unknown
 281                  */
 282                 if (!getsigaction(signo, &sigact)) {
 283                         /*
 284                          * Pretend it worked; maybe we should give a warning
 285                          * here, but other shells don't. We don't alter
 286                          * sigmode, so that we retry every time.
 287                          */
 288                         return;
 289                 }
 290                 if (sigact == SIG_IGN) {
 291                         if (mflag && (signo == SIGTSTP ||
 292                              signo == SIGTTIN || signo == SIGTTOU)) {
 293                                 *t = S_IGN;     /* don't hard ignore these */
 294                         } else
 295                                 *t = S_HARD_IGN;
 296                 } else {
 297                         *t = S_RESET;   /* force to be set */
 298                 }
 299         }
 300         if (*t == S_HARD_IGN || *t == action)
 301                 return;
 302         switch (action) {
 303                 case S_DFL:     sigact = SIG_DFL;       break;
 304                 case S_CATCH:   sigact = onsig;         break;
 305                 case S_IGN:     sigact = SIG_IGN;       break;
 306         }
 307         *t = action;
 308         sig = signal(signo, sigact);
 309         if (sig != SIG_ERR && action == S_CATCH)
 310                 siginterrupt(signo, 1);
 311 }
 312
 313
 314 /*
 315  * Return the current setting for sig w/o changing it.
 316  */
 317 static int
 318 getsigaction(int signo, sig_t *sigact)
 319 {
 320         struct sigaction sa;
 321
 322         if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
 323                 return 0;
 324         *sigact = (sig_t) sa.sa_handler;
 325         return 1;
 326 }
 327
 328
 329 /*
 330  * Ignore a signal.
 331  */
 332 void
 333 ignoresig(int signo)
 334 {
 335
 336         if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) {
 337                 signal(signo, SIG_IGN);
 338         }
 339         sigmode[signo] = S_HARD_IGN;
 340 }
 341
 342
 343 #ifdef mkinit
 344 INCLUDE <signal.h>
 345 INCLUDE "trap.h"
 346
 347 SHELLPROC {
 348         char *sm;
 349
 350         clear_traps();
 351         for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
 352                 if (*sm == S_IGN)
 353                         *sm = S_HARD_IGN;
 354         }
 355 }
 356 #endif
 357
 358
 359 /*
 360  * Signal handler.
 361  */
 362 void
 363 onsig(int signo)
 364 {
 365
 366         if (signo == SIGINT && trap[SIGINT] == NULL) {
 367                 onint();
 368                 return;
 369         }
 370
 371         if (signo != SIGCHLD || !ignore_sigchld)
 372                 gotsig[signo] = 1;
 373         pendingsigs++;
 374
 375         /* If we are currently in a wait builtin, prepare to break it */
 376         if ((signo == SIGINT || signo == SIGQUIT) && in_waitcmd != 0)
 377                 breakwaitcmd = 1;
 378         /*
 379          * If a trap is set, not ignored and not the null command, we need
 380          * to make sure traps are executed even when a child blocks signals.
 381          */
 382         if (Tflag &&
 383             trap[signo] != NULL &&
 384             ! (trap[signo][0] == '\0') &&
 385             ! (trap[signo][0] == ':' && trap[signo][1] == '\0'))
 386                 breakwaitcmd = 1;
 387
 388 #ifndef NO_HISTORY
 389         if (signo == SIGWINCH)
 390                 gotwinch = 1;
 391 #endif
 392 }
 393
 394
 395 /*
 396  * Called to execute a trap.  Perhaps we should avoid entering new trap
 397  * handlers while we are executing a trap handler.
 398  */
 399 void
 400 dotrap(void)
 401 {
 402         int i;
 403         int savestatus;
 404
 405         in_dotrap++;
 406         for (;;) {
 407                 for (i = 1; i < NSIG; i++) {
 408                         if (gotsig[i]) {
 409                                 gotsig[i] = 0;
 410                                 if (trap[i]) {
 411                                         /*
 412                                          * Ignore SIGCHLD to avoid infinite
 413                                          * recursion if the trap action does
 414                                          * a fork.
 415                                          */
 416                                         if (i == SIGCHLD)
 417                                                 ignore_sigchld++;
 418                                         savestatus = exitstatus;
 419                                         evalstring(trap[i]);
 420                                         exitstatus = savestatus;
 421                                         if (i == SIGCHLD)
 422                                                 ignore_sigchld--;
 423                                 }
 424                                 break;
 425                         }
 426                 }
 427                 if (i >= NSIG)
 428                         break;
 429         }
 430         in_dotrap--;
 431         pendingsigs = 0;
 432 }
 433
 434
 435 /*
 436  * Controls whether the shell is interactive or not.
 437  */
 438 void
 439 setinteractive(int on)
 440 {
 441         static int is_interactive = -1;
 442
 443         if (on == is_interactive)
 444                 return;
 445         setsignal(SIGINT);
 446         setsignal(SIGQUIT);
 447         setsignal(SIGTERM);
 448 #ifndef NO_HISTORY
 449         setsignal(SIGWINCH);
 450 #endif
 451         is_interactive = on;
 452 }
 453
 454
 455 /*
 456  * Called to exit the shell.
 457  */
 458 void
 459 exitshell(int status)
 460 {
 461         struct jmploc loc1, loc2;
 462         char *p;
 463
 464         TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
 465         if (setjmp(loc1.loc)) {
 466                 goto l1;
 467         }
 468         if (setjmp(loc2.loc)) {
 469                 goto l2;
 470         }
 471         handler = &loc1;
 472         if ((p = trap[0]) != NULL && *p != '\0') {
 473                 trap[0] = NULL;
 474                 evalstring(p);
 475         }
 476 l1:   handler = &loc2;                  /* probably unnecessary */
 477         flushall();
 478 #if JOBS
 479         setjobctl(0);
 480 #endif
 481 l2:   _exit(status);
 482 }