bin/ksh/trap.c

   1 /*      $NetBSD: trap.c,v 1.7 2006/05/13 21:54:13 christos Exp $        */
   2
   3 /*
   4  * signal handling
   5  */
   6 #include <sys/cdefs.h>
   7
   8 #ifndef lint
   9 __RCSID("$NetBSD: trap.c,v 1.7 2006/05/13 21:54:13 christos Exp $");
  10 #endif
  11
  12
  13 /* Kludge to avoid bogus re-declaration of sigtraps[] error on AIX 3.2.5 */
  14 #define FROM_TRAP_C
  15 #include "sh.h"
  16
  17 /* Table is indexed by signal number
  18  *
  19  * The script siglist.sh generates siglist.out, which is a sorted, complete
  20  * list of signals
  21  */
  22 Trap sigtraps[SIGNALS+1] = {
  23         { .signal = SIGEXIT_, .name = "EXIT", .mess = "Signal 0" },
  24 #include "siglist.out"  /* generated by siglist.sh */
  25         { .signal = SIGERR_,  .name = "ERR",  .mess = "Error handler" },
  26     };
  27
  28 static struct sigaction Sigact_ign, Sigact_trap;
  29
  30 void
  31 inittraps()
  32 {
  33 #ifdef HAVE_SYS_SIGLIST
  34 # ifndef SYS_SIGLIST_DECLARED
  35         extern char     *sys_siglist[];
  36 # endif
  37         int     i;
  38
  39         /* Use system description, if available, for unknown signals... */
  40         for (i = 0; i < NSIG; i++)
  41                 if (!sigtraps[i].name && sys_siglist[i] && sys_siglist[i][0])
  42                         sigtraps[i].mess = sys_siglist[i];
  43 #endif  /* HAVE_SYS_SIGLIST */
  44
  45         sigemptyset(&Sigact_ign.sa_mask);
  46         Sigact_ign.sa_flags = KSH_SA_FLAGS;
  47         Sigact_ign.sa_handler = SIG_IGN;
  48         Sigact_trap = Sigact_ign;
  49         Sigact_trap.sa_handler = trapsig;
  50
  51         sigtraps[SIGINT].flags |= TF_DFL_INTR | TF_TTY_INTR;
  52         sigtraps[SIGQUIT].flags |= TF_DFL_INTR | TF_TTY_INTR;
  53         sigtraps[SIGTERM].flags |= TF_DFL_INTR;/* not fatal for interactive */
  54         sigtraps[SIGHUP].flags |= TF_FATAL;
  55         sigtraps[SIGCHLD].flags |= TF_SHELL_USES;
  56
  57         /* these are always caught so we can clean up any temporary files. */
  58         setsig(&sigtraps[SIGINT], trapsig, SS_RESTORE_ORIG);
  59         setsig(&sigtraps[SIGQUIT], trapsig, SS_RESTORE_ORIG);
  60         setsig(&sigtraps[SIGTERM], trapsig, SS_RESTORE_ORIG);
  61         setsig(&sigtraps[SIGHUP], trapsig, SS_RESTORE_ORIG);
  62 }
  63
  64 #ifdef KSH
  65 static RETSIGTYPE alarm_catcher ARGS((int sig));
  66
  67 void
  68 alarm_init()
  69 {
  70         sigtraps[SIGALRM].flags |= TF_SHELL_USES;
  71         setsig(&sigtraps[SIGALRM], alarm_catcher,
  72                 SS_RESTORE_ORIG|SS_FORCE|SS_SHTRAP);
  73 }
  74
  75 static RETSIGTYPE
  76 alarm_catcher(sig)
  77         int sig;
  78 {
  79         int errno_ = errno;
  80
  81         if (ksh_tmout_state == TMOUT_READING) {
  82                 int left = alarm(0);
  83
  84                 if (left == 0) {
  85                         ksh_tmout_state = TMOUT_LEAVING;
  86                         intrsig = 1;
  87                 } else
  88                         alarm(left);
  89         }
  90         errno = errno_;
  91         return RETSIGVAL;
  92 }
  93 #endif /* KSH */
  94
  95 Trap *
  96 gettrap(name, igncase)
  97         const char *name;
  98         int igncase;
  99 {
 100         int i;
 101         register Trap *p;
 102
 103         if (digit(*name)) {
 104                 int n;
 105
 106                 if (getn(name, &n) && 0 <= n && n < SIGNALS)
 107                         return &sigtraps[n];
 108                 return NULL;
 109         }
 110         for (p = sigtraps, i = SIGNALS+1; --i >= 0; p++)
 111                 if (p->name) {
 112                         if (igncase) {
 113                                 if (p->name && (!strcasecmp(p->name, name) ||
 114                                     (strlen(name) > 3 && !strncasecmp("SIG",
 115                                     p->name, 3) &&
 116                                     !strcasecmp(p->name, name + 3))))
 117                                         return p;
 118                         } else {
 119                                 if (p->name && (!strcmp(p->name, name) ||
 120                                     (strlen(name) > 3 && !strncmp("SIG",
 121                                     p->name, 3) && !strcmp(p->name, name + 3))))
 122                                         return p;
 123                         }
 124                 }
 125         return NULL;
 126 }
 127
 128 /*
 129  * trap signal handler
 130  */
 131 RETSIGTYPE
 132 trapsig(i)
 133         int i;
 134 {
 135         Trap *p = &sigtraps[i];
 136         int errno_ = errno;
 137
 138         trap = p->set = 1;
 139         if (p->flags & TF_DFL_INTR)
 140                 intrsig = 1;
 141         if ((p->flags & TF_FATAL) && !p->trap) {
 142                 fatal_trap = 1;
 143                 intrsig = 1;
 144         }
 145         if (p->shtrap)
 146                 (*p->shtrap)(i);
 147 #ifdef V7_SIGNALS
 148         if (sigtraps[i].cursig == trapsig) /* this for SIGCHLD,SIGALRM */
 149                 sigaction(i, &Sigact_trap, (struct sigaction *) 0);
 150 #endif /* V7_SIGNALS */
 151         errno = errno_;
 152         return RETSIGVAL;
 153 }
 154
 155 /* called when we want to allow the user to ^C out of something - won't
 156  * work if user has trapped SIGINT.
 157  */
 158 void
 159 intrcheck()
 160 {
 161         if (intrsig)
 162                 runtraps(TF_DFL_INTR|TF_FATAL);
 163 }
 164
 165 /* called after EINTR to check if a signal with normally causes process
 166  * termination has been received.
 167  */
 168 int
 169 fatal_trap_check()
 170 {
 171         int i;
 172         Trap *p;
 173
 174         /* todo: should check if signal is fatal, not the TF_DFL_INTR flag */
 175         for (p = sigtraps, i = SIGNALS+1; --i >= 0; p++)
 176                 if (p->set && (p->flags & (TF_DFL_INTR|TF_FATAL)))
 177                         /* return value is used as an exit code */
 178                         return 128 + p->signal;
 179         return 0;
 180 }
 181
 182 /* Returns the signal number of any pending traps: ie, a signal which has
 183  * occurred for which a trap has been set or for which the TF_DFL_INTR flag
 184  * is set.
 185  */
 186 int
 187 trap_pending()
 188 {
 189         int i;
 190         Trap *p;
 191
 192         for (p = sigtraps, i = SIGNALS+1; --i >= 0; p++)
 193                 if (p->set && ((p->trap && p->trap[0])
 194                                || ((p->flags & (TF_DFL_INTR|TF_FATAL))
 195                                    && !p->trap)))
 196                         return p->signal;
 197         return 0;
 198 }
 199
 200 /*
 201  * run any pending traps.  If intr is set, only run traps that
 202  * can interrupt commands.
 203  */
 204 void
 205 runtraps(flag)
 206         int flag;
 207 {
 208         int i;
 209         register Trap *p;
 210
 211 #ifdef KSH
 212         if (ksh_tmout_state == TMOUT_LEAVING) {
 213                 ksh_tmout_state = TMOUT_EXECUTING;
 214                 warningf(FALSE, "timed out waiting for input");
 215                 unwind(LEXIT);
 216         } else
 217                 /* XXX: this means the alarm will have no effect if a trap
 218                  * is caught after the alarm() was started...not good.
 219                  */
 220                 ksh_tmout_state = TMOUT_EXECUTING;
 221 #endif /* KSH */
 222         if (!flag)
 223                 trap = 0;
 224         if (flag & TF_DFL_INTR)
 225                 intrsig = 0;
 226         if (flag & TF_FATAL)
 227                 fatal_trap = 0;
 228         for (p = sigtraps, i = SIGNALS+1; --i >= 0; p++)
 229                 if (p->set && (!flag
 230                                || ((p->flags & flag) && p->trap == (char *) 0)))
 231                         runtrap(p);
 232 }
 233
 234 void
 235 runtrap(p)
 236         Trap *p;
 237 {
 238         int     i = p->signal;
 239         char    *trapstr = p->trap;
 240         int     oexstat;
 241         int     UNINITIALIZED(old_changed);
 242
 243         p->set = 0;
 244         if (trapstr == (char *) 0) { /* SIG_DFL */
 245                 if (p->flags & TF_FATAL) {
 246                         /* eg, SIGHUP */
 247                         exstat = 128 + i;
 248                         unwind(LLEAVE);
 249                 }
 250                 if (p->flags & TF_DFL_INTR) {
 251                         /* eg, SIGINT, SIGQUIT, SIGTERM, etc. */
 252                         exstat = 128 + i;
 253                         unwind(LINTR);
 254                 }
 255                 return;
 256         }
 257         if (trapstr[0] == '\0') /* SIG_IGN */
 258                 return;
 259         if (i == SIGEXIT_ || i == SIGERR_) {    /* avoid recursion on these */
 260                 old_changed = p->flags & TF_CHANGED;
 261                 p->flags &= ~TF_CHANGED;
 262                 p->trap = (char *) 0;
 263         }
 264         oexstat = exstat;
 265         /* Note: trapstr is fully parsed before anything is executed, thus
 266          * no problem with afree(p->trap) in settrap() while still in use.
 267          */
 268         command(trapstr);
 269         exstat = oexstat;
 270         if (i == SIGEXIT_ || i == SIGERR_) {
 271                 if (p->flags & TF_CHANGED)
 272                         /* don't clear TF_CHANGED */
 273                         afree(trapstr, APERM);
 274                 else
 275                         p->trap = trapstr;
 276                 p->flags |= old_changed;
 277         }
 278 }
 279
 280 /* clear pending traps and reset user's trap handlers; used after fork(2) */
 281 void
 282 cleartraps()
 283 {
 284         int i;
 285         Trap *p;
 286
 287         trap = 0;
 288         intrsig = 0;
 289         fatal_trap = 0;
 290         for (i = SIGNALS+1, p = sigtraps; --i >= 0; p++) {
 291                 p->set = 0;
 292                 if ((p->flags & TF_USER_SET) && (p->trap && p->trap[0]))
 293                         settrap(p, (char *) 0);
 294         }
 295 }
 296
 297 /* restore signals just before an exec(2) */
 298 void
 299 restoresigs()
 300 {
 301         int i;
 302         Trap *p;
 303
 304         for (i = SIGNALS+1, p = sigtraps; --i >= 0; p++)
 305                 if (p->flags & (TF_EXEC_IGN|TF_EXEC_DFL))
 306                         setsig(p, (p->flags & TF_EXEC_IGN) ? SIG_IGN : SIG_DFL,
 307                                 SS_RESTORE_CURR|SS_FORCE);
 308 }
 309
 310 void
 311 settrap(p, s)
 312         Trap *p;
 313         char *s;
 314 {
 315         handler_t f;
 316
 317         if (p->trap)
 318                 afree(p->trap, APERM);
 319         p->flags |= TF_CHANGED|TF_USER_SET;
 320         if (s) {
 321                 p->trap = str_save(s, APERM);
 322                 f = s[0] ? trapsig : SIG_IGN;
 323         } else {
 324                 p->trap = NULL;
 325                 f = SIG_DFL;
 326         }
 327         if ((p->flags & (TF_DFL_INTR|TF_FATAL)) && f == SIG_DFL)
 328                 f = trapsig;
 329         else if (p->flags & TF_SHELL_USES) {
 330                 if (!(p->flags & TF_ORIG_IGN) || Flag(FTALKING)) {
 331                         /* do what user wants at exec time */
 332                         p->flags &= ~(TF_EXEC_IGN|TF_EXEC_DFL);
 333                         if (f == SIG_IGN)
 334                                 p->flags |= TF_EXEC_IGN;
 335                         else
 336                                 p->flags |= TF_EXEC_DFL;
 337                 }
 338                 /* assumes handler already set to what shell wants it
 339                  * (normally trapsig, but could be j_sigchld() or SIG_IGN)
 340                  */
 341                 return;
 342         }
 343
 344         /* todo: should we let user know signal is ignored? how? */
 345         setsig(p, f, SS_RESTORE_CURR|SS_USER);
 346 }
 347
 348 /* Called by c_print() when writing to a co-process to ensure SIGPIPE won't
 349  * kill shell (unless user catches it and exits)
 350  */
 351 int
 352 block_pipe()
 353 {
 354         int restore_dfl = 0;
 355         Trap *p = &sigtraps[SIGPIPE];
 356
 357         if (!(p->flags & (TF_ORIG_IGN|TF_ORIG_DFL))) {
 358                 setsig(p, SIG_IGN, SS_RESTORE_CURR);
 359                 if (p->flags & TF_ORIG_DFL)
 360                         restore_dfl = 1;
 361         } else if (p->cursig == SIG_DFL) {
 362                 setsig(p, SIG_IGN, SS_RESTORE_CURR);
 363                 restore_dfl = 1; /* restore to SIG_DFL */
 364         }
 365         return restore_dfl;
 366 }
 367
 368 /* Called by c_print() to undo whatever block_pipe() did */
 369 void
 370 restore_pipe(restore_dfl)
 371         int restore_dfl;
 372 {
 373         if (restore_dfl)
 374                 setsig(&sigtraps[SIGPIPE], SIG_DFL, SS_RESTORE_CURR);
 375 }
 376
 377 /* Set action for a signal.  Action may not be set if original
 378  * action was SIG_IGN, depending on the value of flags and
 379  * FTALKING.
 380  */
 381 int
 382 setsig(p, f, flags)
 383         Trap *p;
 384         handler_t f;
 385         int flags;
 386 {
 387         struct sigaction sigact;
 388
 389         if (p->signal == SIGEXIT_ || p->signal == SIGERR_)
 390                 return 1;
 391
 392         /* First time setting this signal?  If so, get and note the current
 393          * setting.
 394          */
 395         if (!(p->flags & (TF_ORIG_IGN|TF_ORIG_DFL))) {
 396                 sigaction(p->signal, &Sigact_ign, &sigact);
 397                 p->flags |= sigact.sa_handler == SIG_IGN ?
 398                                         TF_ORIG_IGN : TF_ORIG_DFL;
 399                 p->cursig = SIG_IGN;
 400         }
 401
 402         /* Generally, an ignored signal stays ignored, except if
 403          *      - the user of an interactive shell wants to change it
 404          *      - the shell wants for force a change
 405          */
 406         if ((p->flags & TF_ORIG_IGN) && !(flags & SS_FORCE)
 407             && (!(flags & SS_USER) || !Flag(FTALKING)))
 408                 return 0;
 409
 410         setexecsig(p, flags & SS_RESTORE_MASK);
 411
 412         /* This is here 'cause there should be a way of clearing shtraps, but
 413          * don't know if this is a sane way of doing it.  At the moment,
 414          * all users of shtrap are lifetime users (SIGCHLD, SIGALRM, SIGWINCH).
 415          */
 416         if (!(flags & SS_USER))
 417                 p->shtrap = (handler_t) 0;
 418         if (flags & SS_SHTRAP) {
 419                 p->shtrap = f;
 420                 f = trapsig;
 421         }
 422
 423         if (p->cursig != f) {
 424                 p->cursig = f;
 425                 sigemptyset(&sigact.sa_mask);
 426                 sigact.sa_flags = KSH_SA_FLAGS;
 427                 sigact.sa_handler = f;
 428                 sigaction(p->signal, &sigact, (struct sigaction *) 0);
 429         }
 430
 431         return 1;
 432 }
 433
 434 /* control what signal is set to before an exec() */
 435 void
 436 setexecsig(p, restore)
 437         Trap *p;
 438         int restore;
 439 {
 440         /* XXX debugging */
 441         if (!(p->flags & (TF_ORIG_IGN|TF_ORIG_DFL)))
 442                 internal_errorf(1, "setexecsig: unset signal %d(%s)",
 443                         p->signal, p->name);
 444
 445         /* restore original value for exec'd kids */
 446         p->flags &= ~(TF_EXEC_IGN|TF_EXEC_DFL);
 447         switch (restore & SS_RESTORE_MASK) {
 448           case SS_RESTORE_CURR: /* leave things as they currently are */
 449                 break;
 450           case SS_RESTORE_ORIG:
 451                 p->flags |= p->flags & TF_ORIG_IGN ? TF_EXEC_IGN : TF_EXEC_DFL;
 452                 break;
 453           case SS_RESTORE_DFL:
 454                 p->flags |= TF_EXEC_DFL;
 455                 break;
 456           case SS_RESTORE_IGN:
 457                 p->flags |= TF_EXEC_IGN;
 458                 break;
 459         }
 460 }