signal.c

   1 /*@ S-nail - a mail user agent derived from Berkeley Mail.
   2  *@ Signal related stuff as well as NotYetDead functions.
   3  *
   4  * Copyright (c) 2000-2004 Gunnar Ritter, Freiburg i. Br., Germany.
   5  * Copyright (c) 2012 - 2015 Steffen (Daode) Nurpmeso <sdaoden@users.sf.net>.
   6  */
   7 /*
   8  * Copyright (c) 1980, 1993
   9  *      The Regents of the University of California.  All rights reserved.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 3. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35 #undef n_FILE
  36 #define n_FILE signal
  37
  38 #ifndef HAVE_AMALGAMATION
  39 # include "nail.h"
  40 #endif
  41
  42 /*
  43  * TODO At the beginning of November 2015 -- for v14.9 -- i've tried for one
  44  * TODO and a half week to convert this codebase to SysV style signal handling,
  45  * TODO meaning no SA_RESTART and EINTR in a lot of places and error reporting
  46  * TODO up the chain.   I failed miserably, not only because S/MIME / SSL but
  47  * TODO also because of general frustration.  Directly after v14.9 i will strip
  48  * TODO ANYTHING off the codebase (socket stuff etc.) and keep only the very
  49  * TODO core, doing namespace and type cleanup and convert this core to a clean
  50  * TODO approach, from which i plan to start this thing anew.
  51  * TODO For now i introduced the n_sigman, yet another hack, to be used in a
  52  * TODO few places.
  53  * TODO The real solution:
  54  * TODO - No SA_RESTART.  Just like for my C++ library: encapsulate EINTR in
  55  * TODO   userspace at the systemcall (I/O rewrite: drop stdio), normal
  56  * TODO   interface auto-restarts, special _intr() series return EINTR.
  57  * TODO   Do n_sigman_poll()/peek()/whatever whenever desired for the former,
  58  * TODO   report errors up the call chain, have places where operations can be
  59  * TODO   "properly" aborted.
  60  * TODO - We save the initial signal settings upon program startup.
  61  * TODO - We register our sigman handlers once, at program startup.
  62  * TODO   Maximally, and most likely only due to lack of atomic CAS, ignore
  63  * TODO   or block some signals temporarily.  Best if not.
  64  * TODO   The signal handlers only set a flag.  Block all signals for handler
  65  * TODO   execution, like this we are safe to "set the first signal was x".
  66  * TODO - In interactive context, ignore SIGTERM.
  67  * TODO   I.e., see the POSIX standard for what a shell does.
  68  * TODO - In non-interactive context, don't know anything about job control!?!
  69  * TODO - Place child processes in their own process group.  Restore the signal
  70  * TODO   mask back to the saved original one for them, before exec.
  71  * TODO - Except for job control related (<-> interactive) ignore any signals
  72  * TODO   while we are "behind" a child that occupies the terminal.  For those,
  73  * TODO   perform proper terminal attribute handling.  For childs that don't
  74  * TODO   occupy the terminal we "are the shell" and should therefore manage
  75  * TODO   them accordingly, including termination request as necessary.
  76  * TODO   And if we have a worker in a pipeline, we need to manage it and deal
  77  * TODO   with it properly, WITHOUT temporary signal overwrites.
  78  * TODO - No more jumps.
  79  * TODO - (When sockets will be reintroduced, non-blocking.)
  80  * TODO - (When SSL is reintroduced, memory BIO.  It MAY be necessary to
  81  * TODO   temporarily block signals during a few SSL functions?  Read SSL docu!
  82  * TODO   But i prefer blocking since it's a single syscall, not temporary
  83  * TODO   SA_RESTART setting, since that has to be done for every signal.)
  84  */
  85
  86 #ifdef HAVE_NYD
  87 struct nyd_info {
  88    char const  *ni_file;
  89    char const  *ni_fun;
  90    ui32_t      ni_chirp_line;
  91    ui32_t      ni_level;
  92 };
  93 #endif
  94
  95 /* {hold,rele}_all_sigs() */
  96 static size_t           _alls_depth;
  97 static sigset_t         _alls_nset, _alls_oset;
  98
  99 /* {hold,rele}_sigs() */
 100 static size_t           _hold_sigdepth;
 101 static sigset_t         _hold_nset, _hold_oset;
 102
 103 /* NYD, memory pool debug */
 104 #ifdef HAVE_NYD
 105 static ui32_t           _nyd_curr, _nyd_level;
 106 static struct nyd_info  _nyd_infos[NYD_CALLS_MAX];
 107 #endif
 108
 109 /* */
 110 #ifdef HAVE_NYD
 111 static void    _nyd_print(int fd, struct nyd_info *nip);
 112 #endif
 113
 114 #ifdef HAVE_NYD
 115 static void
 116 _nyd_print(int fd, struct nyd_info *nip)
 117 {
 118    char buf[80];
 119    union {int i; size_t z;} u;
 120
 121    u.i = snprintf(buf, sizeof buf,
 122          "%c [%2" PRIu32 "] %.25s (%.16s:%" PRIu32 ")\n",
 123          "=><"[(nip->ni_chirp_line >> 29) & 0x3], nip->ni_level, nip->ni_fun,
 124          nip->ni_file, (nip->ni_chirp_line & 0x1FFFFFFFu));
 125    if (u.i > 0) {
 126       u.z = u.i;
 127       if (u.z > sizeof buf)
 128          u.z = sizeof buf - 1; /* (Skip \0) */
 129       write(fd, buf, u.z);
 130    }
 131 }
 132 #endif
 133
 134 FL void
 135 n_raise(int signo)
 136 {
 137    NYD2_ENTER;
 138    kill(getpid(), signo);
 139    NYD2_LEAVE;
 140 }
 141
 142 FL sighandler_type
 143 safe_signal(int signum, sighandler_type handler)
 144 {
 145    struct sigaction nact, oact;
 146    sighandler_type rv;
 147    NYD2_ENTER;
 148
 149    nact.sa_handler = handler;
 150    sigemptyset(&nact.sa_mask);
 151    nact.sa_flags = SA_RESTART;
 152    rv = (sigaction(signum, &nact, &oact) != 0) ? SIG_ERR : oact.sa_handler;
 153    NYD2_LEAVE;
 154    return rv;
 155 }
 156
 157 FL void
 158 hold_all_sigs(void)
 159 {
 160    NYD2_ENTER;
 161    if (_alls_depth++ == 0) {
 162       sigfillset(&_alls_nset);
 163       sigdelset(&_alls_nset, SIGABRT);
 164 #ifdef SIGBUS
 165       sigdelset(&_alls_nset, SIGBUS);
 166 #endif
 167       sigdelset(&_alls_nset, SIGCHLD);
 168       sigdelset(&_alls_nset, SIGFPE);
 169       sigdelset(&_alls_nset, SIGILL);
 170       sigdelset(&_alls_nset, SIGKILL);
 171       sigdelset(&_alls_nset, SIGSEGV);
 172       sigdelset(&_alls_nset, SIGSTOP);
 173       sigprocmask(SIG_BLOCK, &_alls_nset, &_alls_oset);
 174    }
 175    NYD2_LEAVE;
 176 }
 177
 178 FL void
 179 rele_all_sigs(void)
 180 {
 181    NYD2_ENTER;
 182    if (--_alls_depth == 0)
 183       sigprocmask(SIG_SETMASK, &_alls_oset, (sigset_t*)NULL);
 184    NYD2_LEAVE;
 185 }
 186
 187 FL void
 188 hold_sigs(void)
 189 {
 190    NYD2_ENTER;
 191    if (_hold_sigdepth++ == 0) {
 192       sigemptyset(&_hold_nset);
 193       sigaddset(&_hold_nset, SIGHUP);
 194       sigaddset(&_hold_nset, SIGINT);
 195       sigaddset(&_hold_nset, SIGQUIT);
 196       sigprocmask(SIG_BLOCK, &_hold_nset, &_hold_oset);
 197    }
 198    NYD2_LEAVE;
 199 }
 200
 201 FL void
 202 rele_sigs(void)
 203 {
 204    NYD2_ENTER;
 205    if (--_hold_sigdepth == 0)
 206       sigprocmask(SIG_SETMASK, &_hold_oset, NULL);
 207    NYD2_LEAVE;
 208 }
 209
 210 /* TODO This is temporary gracyness */
 211 static struct n_sigman *n__sigman;
 212 static void n__sigman_hdl(int signo);
 213 static void
 214 n__sigman_hdl(int signo){
 215    NYD_X; /* Signal handler */
 216    n__sigman->sm_signo = signo;
 217    siglongjmp(n__sigman->sm_jump, 1);
 218 }
 219
 220 FL int
 221 n__sigman_enter(struct n_sigman *self, int flags){
 222    /* TODO no error checking when installing sighdls */
 223    int rv;
 224    NYD2_ENTER;
 225
 226    if((int)flags >= 0){
 227       self->sm_flags = (enum n_sigman_flags)flags;
 228       self->sm_signo = 0;
 229       self->sm_outer = n__sigman;
 230       if(flags & n_SIGMAN_HUP)
 231          self->sm_ohup = safe_signal(SIGHUP, &n__sigman_hdl);
 232       if(flags & n_SIGMAN_INT)
 233          self->sm_oint = safe_signal(SIGINT, &n__sigman_hdl);
 234       if(flags & n_SIGMAN_QUIT)
 235          self->sm_oquit = safe_signal(SIGQUIT, &n__sigman_hdl);
 236       if(flags & n_SIGMAN_PIPE)
 237          self->sm_opipe = safe_signal(SIGPIPE, &n__sigman_hdl);
 238       n__sigman = self;
 239       rv = 0;
 240    }else{
 241       flags = self->sm_flags;
 242
 243       /* Just in case of a race (signal while holding and ignoring? really?) */
 244       if(!(flags & n__SIGMAN_PING)){
 245          if(flags & n_SIGMAN_HUP)
 246             safe_signal(SIGHUP, SIG_IGN);
 247          if(flags & n_SIGMAN_INT)
 248             safe_signal(SIGINT, SIG_IGN);
 249          if(flags & n_SIGMAN_QUIT)
 250             safe_signal(SIGQUIT, SIG_IGN);
 251          if(flags & n_SIGMAN_PIPE)
 252             safe_signal(SIGPIPE, SIG_IGN);
 253       }
 254       rv = self->sm_signo;
 255    }
 256    rele_sigs();
 257    NYD2_LEAVE;
 258    return rv;
 259 }
 260
 261 FL void
 262 n_sigman_cleanup_ping(struct n_sigman *self){
 263    ui32_t f;
 264    NYD2_ENTER;
 265
 266    hold_sigs();
 267
 268    f = self->sm_flags;
 269    f |= n__SIGMAN_PING;
 270    self->sm_flags = f;
 271
 272    if(f & n_SIGMAN_HUP)
 273       safe_signal(SIGHUP, SIG_IGN);
 274    if(f & n_SIGMAN_INT)
 275       safe_signal(SIGINT, SIG_IGN);
 276    if(f & n_SIGMAN_QUIT)
 277       safe_signal(SIGQUIT, SIG_IGN);
 278    if(f & n_SIGMAN_PIPE)
 279       safe_signal(SIGPIPE, SIG_IGN);
 280
 281    rele_sigs();
 282    NYD2_LEAVE;
 283 }
 284
 285 FL void
 286 n_sigman_leave(struct n_sigman *self,
 287       enum n_sigman_flags reraise_flags){
 288    ui32_t f;
 289    int sig;
 290    NYD2_ENTER;
 291
 292    hold_sigs();
 293    n__sigman = self->sm_outer;
 294
 295    f = self->sm_flags;
 296    if(f & n_SIGMAN_HUP)
 297       safe_signal(SIGHUP, self->sm_ohup);
 298    if(f & n_SIGMAN_INT)
 299       safe_signal(SIGINT, self->sm_oint);
 300    if(f & n_SIGMAN_QUIT)
 301       safe_signal(SIGQUIT, self->sm_oquit);
 302    if(f & n_SIGMAN_PIPE)
 303       safe_signal(SIGPIPE, self->sm_opipe);
 304
 305    rele_sigs();
 306
 307    sig = 0;
 308    switch(self->sm_signo){
 309    case SIGPIPE:
 310       if((reraise_flags & n_SIGMAN_PIPE) ||
 311             ((reraise_flags & n_SIGMAN_NTTYOUT_PIPE) &&
 312              !(options & OPT_TTYOUT)))
 313          sig = SIGPIPE;
 314       break;
 315    case SIGHUP:
 316       if(reraise_flags & n_SIGMAN_HUP)
 317          sig = SIGHUP;
 318       break;
 319    case SIGINT:
 320       if(reraise_flags & n_SIGMAN_INT)
 321          sig = SIGINT;
 322       break;
 323    case SIGQUIT:
 324       if(reraise_flags & n_SIGMAN_QUIT)
 325          sig = SIGQUIT;
 326       break;
 327    default:
 328       break;
 329    }
 330
 331    NYD2_LEAVE;
 332    if(sig != 0){
 333       sigset_t cset;
 334
 335       sigemptyset(&cset);
 336       sigaddset(&cset, sig);
 337       sigprocmask(SIG_UNBLOCK, &cset, NULL);
 338       n_raise(sig);
 339    }
 340 }
 341
 342 FL int
 343 n_sigman_peek(void){
 344    int rv;
 345    NYD2_ENTER;
 346    rv = 0;
 347    NYD2_LEAVE;
 348    return rv;
 349 }
 350
 351 FL void
 352 n_sigman_consume(void){
 353    NYD2_ENTER;
 354    NYD2_LEAVE;
 355 }
 356
 357 #ifdef HAVE_NYD
 358 FL void
 359 _nyd_chirp(ui8_t act, char const *file, ui32_t line, char const *fun)
 360 {
 361    struct nyd_info *nip = _nyd_infos;
 362
 363    if (_nyd_curr != NELEM(_nyd_infos))
 364       nip += _nyd_curr++;
 365    else
 366       _nyd_curr = 1;
 367    nip->ni_file = file;
 368    nip->ni_fun = fun;
 369    nip->ni_chirp_line = ((ui32_t)(act & 0x3) << 29) | (line & 0x1FFFFFFFu);
 370    nip->ni_level = ((act == 0) ? _nyd_level
 371          : (act == 1) ? ++_nyd_level : _nyd_level--);
 372 }
 373
 374 FL void
 375 _nyd_oncrash(int signo)
 376 {
 377    char pathbuf[PATH_MAX], s2ibuf[32], *cp;
 378    struct sigaction xact;
 379    sigset_t xset;
 380    size_t i, fnl;
 381    int fd;
 382    struct nyd_info *nip;
 383
 384    LCTA(sizeof("./") -1 + sizeof(UAGENT) -1 + sizeof(".dat") < PATH_MAX);
 385
 386    xact.sa_handler = SIG_DFL;
 387    sigemptyset(&xact.sa_mask);
 388    xact.sa_flags = 0;
 389    sigaction(signo, &xact, NULL);
 390
 391    i = strlen(tempdir);
 392    fnl = sizeof(UAGENT) -1;
 393
 394    if (i + 1 + fnl + 1 + sizeof(".dat") > sizeof(pathbuf)) {
 395       (cp = pathbuf)[0] = '.';
 396       i = 1;
 397    } else
 398       memcpy(cp = pathbuf, tempdir, i);
 399    cp[i++] = '/'; /* xxx pathsep */
 400    memcpy(cp += i, UAGENT, fnl);
 401    i += fnl;
 402    memcpy(cp += fnl, ".dat", sizeof(".dat"));
 403    fnl = i + sizeof(".dat") -1;
 404
 405    if ((fd = open(pathbuf, O_WRONLY | O_CREAT | O_EXCL, 0666)) == -1)
 406       fd = STDERR_FILENO;
 407
 408 # undef _X
 409 # define _X(X) (X), sizeof(X) -1
 410    write(fd, _X("\n\nNYD: program dying due to signal "));
 411
 412    cp = s2ibuf + sizeof(s2ibuf) -1;
 413    *cp = '\0';
 414    i = signo;
 415    do {
 416       *--cp = "0123456789"[i % 10];
 417       i /= 10;
 418    } while (i != 0);
 419    write(fd, cp, PTR2SIZE((s2ibuf + sizeof(s2ibuf) -1) - cp));
 420
 421    write(fd, _X(":\n"));
 422
 423    if (_nyd_infos[NELEM(_nyd_infos) - 1].ni_file != NULL)
 424       for (i = _nyd_curr, nip = _nyd_infos + i; i < NELEM(_nyd_infos); ++i)
 425          _nyd_print(fd, nip++);
 426    for (i = 0, nip = _nyd_infos; i < _nyd_curr; ++i)
 427       _nyd_print(fd, nip++);
 428
 429    write(fd, _X("----------\nCome up to the lab and see what's on the slab\n"));
 430
 431    if (fd != STDERR_FILENO) {
 432       write(STDERR_FILENO, _X("Crash NYD listing written to "));
 433       write(STDERR_FILENO, pathbuf, fnl);
 434       write(STDERR_FILENO, _X("\n"));
 435 # undef _X
 436
 437       close(fd);
 438    }
 439
 440    sigemptyset(&xset);
 441    sigaddset(&xset, signo);
 442    sigprocmask(SIG_UNBLOCK, &xset, NULL);
 443    n_raise(signo);
 444    for (;;)
 445       _exit(EXIT_ERR);
 446 }
 447 #endif /* HAVE_NYD */
 448
 449 /* s-it-mode */