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 - 2017 Steffen (Daode) Nurpmeso <steffen@sdaoden.eu>.
   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 #ifdef HAVE_DEVEL
 135 FL int
 136 c_sigstate(void *vp){ /* TODO remove again */
 137    struct{
 138       int val;
 139       char const name[12];
 140    } const *hdlp, hdla[] = {
 141       {SIGINT, "SIGINT"}, {SIGHUP, "SIGHUP"}, {SIGQUIT, "SIGQUIT"},
 142       {SIGTSTP, "SIGTSTP"}, {SIGTTIN, "SIGTTIN"}, {SIGTTOU, "SIGTTOU"},
 143       {SIGCHLD, "SIGCHLD"}, {SIGPIPE, "SIGPIPE"}
 144    };
 145    char const *cp;
 146    NYD2_ENTER;
 147
 148    if((cp = vp) != NULL && cp[0] != '\0'){
 149       if(!asccasecmp(&cp[1], "all")){
 150          if(cp[0] == '+')
 151             hold_all_sigs();
 152          else
 153             rele_all_sigs();
 154       }else if(!asccasecmp(&cp[1], "hold")){
 155          if(cp[0] == '+')
 156             hold_sigs();
 157          else
 158             rele_sigs();
 159       }
 160    }
 161
 162    fprintf(n_stdout, "alls_depth %zu, hold_sigdepth %zu\nHandlers:\n",
 163       _alls_depth, _hold_sigdepth);
 164    for(hdlp = hdla; hdlp < &hdla[n_NELEM(hdla)]; ++hdlp){
 165       sighandler_type shp;
 166
 167       shp = safe_signal(hdlp->val, SIG_IGN);
 168       safe_signal(hdlp->val, shp);
 169       fprintf(n_stdout, "  %s: %p (%s)\n", hdlp->name, shp,
 170          (shp == SIG_ERR ? "ERR" : (shp == SIG_DFL ? "DFL"
 171             : (shp == SIG_IGN ? "IGN" : "ptf?"))));
 172    }
 173    NYD2_LEAVE;
 174    return OKAY;
 175 }
 176 #endif /* HAVE_DEVEL */
 177
 178 FL void
 179 n_raise(int signo)
 180 {
 181    NYD2_ENTER;
 182    kill(getpid(), signo);
 183    NYD2_LEAVE;
 184 }
 185
 186 FL sighandler_type
 187 safe_signal(int signum, sighandler_type handler)
 188 {
 189    struct sigaction nact, oact;
 190    sighandler_type rv;
 191    NYD2_ENTER;
 192
 193    nact.sa_handler = handler;
 194    sigemptyset(&nact.sa_mask);
 195    nact.sa_flags = SA_RESTART;
 196    rv = (sigaction(signum, &nact, &oact) != 0) ? SIG_ERR : oact.sa_handler;
 197    NYD2_LEAVE;
 198    return rv;
 199 }
 200
 201 FL n_sighdl_t
 202 n_signal(int signo, n_sighdl_t hdl){
 203    struct sigaction nact, oact;
 204    NYD2_ENTER;
 205
 206    nact.sa_handler = hdl;
 207    sigemptyset(&nact.sa_mask);
 208    nact.sa_flags = 0;
 209    hdl = (sigaction(signo, &nact, &oact) != 0) ? SIG_ERR : oact.sa_handler;
 210    NYD2_LEAVE;
 211    return hdl;
 212 }
 213
 214 FL void
 215 hold_all_sigs(void)
 216 {
 217    NYD2_ENTER;
 218    if (_alls_depth++ == 0) {
 219       sigfillset(&_alls_nset);
 220       sigdelset(&_alls_nset, SIGABRT);
 221 #ifdef SIGBUS
 222       sigdelset(&_alls_nset, SIGBUS);
 223 #endif
 224       sigdelset(&_alls_nset, SIGCHLD);
 225       sigdelset(&_alls_nset, SIGFPE);
 226       sigdelset(&_alls_nset, SIGILL);
 227       sigdelset(&_alls_nset, SIGKILL);
 228       sigdelset(&_alls_nset, SIGSEGV);
 229       sigdelset(&_alls_nset, SIGSTOP);
 230       sigprocmask(SIG_BLOCK, &_alls_nset, &_alls_oset);
 231    }
 232    NYD2_LEAVE;
 233 }
 234
 235 FL void
 236 rele_all_sigs(void)
 237 {
 238    NYD2_ENTER;
 239    if (--_alls_depth == 0)
 240       sigprocmask(SIG_SETMASK, &_alls_oset, (sigset_t*)NULL);
 241    NYD2_LEAVE;
 242 }
 243
 244 FL void
 245 hold_sigs(void)
 246 {
 247    NYD2_ENTER;
 248    if (_hold_sigdepth++ == 0) {
 249       sigemptyset(&_hold_nset);
 250       sigaddset(&_hold_nset, SIGHUP);
 251       sigaddset(&_hold_nset, SIGINT);
 252       sigaddset(&_hold_nset, SIGQUIT);
 253       sigprocmask(SIG_BLOCK, &_hold_nset, &_hold_oset);
 254    }
 255    NYD2_LEAVE;
 256 }
 257
 258 FL void
 259 rele_sigs(void)
 260 {
 261    NYD2_ENTER;
 262    if (--_hold_sigdepth == 0)
 263       sigprocmask(SIG_SETMASK, &_hold_oset, NULL);
 264    NYD2_LEAVE;
 265 }
 266
 267 /* TODO This is temporary gracyness */
 268 static struct n_sigman *n__sigman;
 269 static void n__sigman_hdl(int signo);
 270 static void
 271 n__sigman_hdl(int signo){
 272    NYD_X; /* Signal handler */
 273    n__sigman->sm_signo = signo;
 274    siglongjmp(n__sigman->sm_jump, 1);
 275 }
 276
 277 FL int
 278 n__sigman_enter(struct n_sigman *self, int flags){
 279    /* TODO no error checking when installing sighdls */
 280    int rv;
 281    NYD2_ENTER;
 282
 283    if((int)flags >= 0){
 284       self->sm_flags = (enum n_sigman_flags)flags;
 285       self->sm_signo = 0;
 286       self->sm_outer = n__sigman;
 287       if(flags & n_SIGMAN_HUP)
 288          self->sm_ohup = safe_signal(SIGHUP, &n__sigman_hdl);
 289       if(flags & n_SIGMAN_INT)
 290          self->sm_oint = safe_signal(SIGINT, &n__sigman_hdl);
 291       if(flags & n_SIGMAN_QUIT)
 292          self->sm_oquit = safe_signal(SIGQUIT, &n__sigman_hdl);
 293       if(flags & n_SIGMAN_PIPE)
 294          self->sm_opipe = safe_signal(SIGPIPE, &n__sigman_hdl);
 295       n__sigman = self;
 296       rv = 0;
 297    }else{
 298       flags = self->sm_flags;
 299
 300       /* Just in case of a race (signal while holding and ignoring? really?) */
 301       if(!(flags & n__SIGMAN_PING)){
 302          if(flags & n_SIGMAN_HUP)
 303             safe_signal(SIGHUP, SIG_IGN);
 304          if(flags & n_SIGMAN_INT)
 305             safe_signal(SIGINT, SIG_IGN);
 306          if(flags & n_SIGMAN_QUIT)
 307             safe_signal(SIGQUIT, SIG_IGN);
 308          if(flags & n_SIGMAN_PIPE)
 309             safe_signal(SIGPIPE, SIG_IGN);
 310       }
 311       rv = self->sm_signo;
 312       /* The signal mask has been restored, but of course rele_sigs() has
 313        * already been called: account for restoration due to jump */
 314       ++_hold_sigdepth;
 315    }
 316    rele_sigs();
 317    NYD2_LEAVE;
 318    return rv;
 319 }
 320
 321 FL void
 322 n_sigman_cleanup_ping(struct n_sigman *self){
 323    ui32_t f;
 324    NYD2_ENTER;
 325
 326    hold_sigs();
 327
 328    f = self->sm_flags;
 329    f |= n__SIGMAN_PING;
 330    self->sm_flags = f;
 331
 332    if(f & n_SIGMAN_HUP)
 333       safe_signal(SIGHUP, SIG_IGN);
 334    if(f & n_SIGMAN_INT)
 335       safe_signal(SIGINT, SIG_IGN);
 336    if(f & n_SIGMAN_QUIT)
 337       safe_signal(SIGQUIT, SIG_IGN);
 338    if(f & n_SIGMAN_PIPE)
 339       safe_signal(SIGPIPE, SIG_IGN);
 340
 341    rele_sigs();
 342    NYD2_LEAVE;
 343 }
 344
 345 FL void
 346 n_sigman_leave(struct n_sigman *self,
 347       enum n_sigman_flags reraise_flags){
 348    ui32_t f;
 349    int sig;
 350    NYD2_ENTER;
 351
 352    hold_sigs();
 353    n__sigman = self->sm_outer;
 354
 355    f = self->sm_flags;
 356    if(f & n_SIGMAN_HUP)
 357       safe_signal(SIGHUP, self->sm_ohup);
 358    if(f & n_SIGMAN_INT)
 359       safe_signal(SIGINT, self->sm_oint);
 360    if(f & n_SIGMAN_QUIT)
 361       safe_signal(SIGQUIT, self->sm_oquit);
 362    if(f & n_SIGMAN_PIPE)
 363       safe_signal(SIGPIPE, self->sm_opipe);
 364
 365    rele_sigs();
 366
 367    sig = 0;
 368    switch(self->sm_signo){
 369    case SIGPIPE:
 370       if((reraise_flags & n_SIGMAN_PIPE) ||
 371             ((reraise_flags & n_SIGMAN_NTTYOUT_PIPE) &&
 372              !(n_psonce & n_PSO_TTYOUT)))
 373          sig = SIGPIPE;
 374       break;
 375    case SIGHUP:
 376       if(reraise_flags & n_SIGMAN_HUP)
 377          sig = SIGHUP;
 378       break;
 379    case SIGINT:
 380       if(reraise_flags & n_SIGMAN_INT)
 381          sig = SIGINT;
 382       break;
 383    case SIGQUIT:
 384       if(reraise_flags & n_SIGMAN_QUIT)
 385          sig = SIGQUIT;
 386       break;
 387    default:
 388       break;
 389    }
 390
 391    NYD2_LEAVE;
 392    if(sig != 0){
 393       sigset_t cset;
 394
 395       sigemptyset(&cset);
 396       sigaddset(&cset, sig);
 397       sigprocmask(SIG_UNBLOCK, &cset, NULL);
 398       n_raise(sig);
 399    }
 400 }
 401
 402 FL int
 403 n_sigman_peek(void){
 404    int rv;
 405    NYD2_ENTER;
 406    rv = 0;
 407    NYD2_LEAVE;
 408    return rv;
 409 }
 410
 411 FL void
 412 n_sigman_consume(void){
 413    NYD2_ENTER;
 414    NYD2_LEAVE;
 415 }
 416
 417 #ifdef HAVE_NYD
 418 FL void
 419 _nyd_chirp(ui8_t act, char const *file, ui32_t line, char const *fun)
 420 {
 421    struct nyd_info *nip = _nyd_infos;
 422
 423    if (_nyd_curr != n_NELEM(_nyd_infos))
 424       nip += _nyd_curr++;
 425    else
 426       _nyd_curr = 1;
 427    nip->ni_file = file;
 428    nip->ni_fun = fun;
 429    nip->ni_chirp_line = ((ui32_t)(act & 0x3) << 29) | (line & 0x1FFFFFFFu);
 430    nip->ni_level = ((act == 0) ? _nyd_level
 431          : (act == 1) ? ++_nyd_level : _nyd_level--);
 432 }
 433
 434 FL void
 435 _nyd_oncrash(int signo)
 436 {
 437    char pathbuf[PATH_MAX], s2ibuf[32], *cp;
 438    struct sigaction xact;
 439    sigset_t xset;
 440    struct nyd_info *nip;
 441    int fd;
 442    size_t i, fnl;
 443    char const *tmpdir;
 444
 445    n_LCTA(sizeof("./") -1 + sizeof(VAL_UAGENT) -1 + sizeof(".dat") < PATH_MAX,
 446       "System limits too low for fixed-size buffer operation");
 447
 448    xact.sa_handler = SIG_DFL;
 449    sigemptyset(&xact.sa_mask);
 450    xact.sa_flags = 0;
 451    sigaction(signo, &xact, NULL);
 452
 453    i = strlen(tmpdir = ok_vlook(TMPDIR));
 454    fnl = sizeof(VAL_UAGENT) -1;
 455
 456    if (i + 1 + fnl + 1 + sizeof(".dat") > sizeof(pathbuf)) {
 457       (cp = pathbuf)[0] = '.';
 458       i = 1;
 459    } else
 460       memcpy(cp = pathbuf, tmpdir, i);
 461    cp[i++] = '/'; /* xxx pathsep */
 462    memcpy(cp += i, VAL_UAGENT, fnl);
 463    i += fnl;
 464    memcpy(cp += fnl, ".dat", sizeof(".dat"));
 465    fnl = i + sizeof(".dat") -1;
 466
 467    if ((fd = open(pathbuf, O_WRONLY | O_CREAT | O_EXCL, 0666)) == -1)
 468       fd = STDERR_FILENO;
 469
 470 # undef _X
 471 # define _X(X) (X), sizeof(X) -1
 472    write(fd, _X("\n\nNYD: program dying due to signal "));
 473
 474    cp = s2ibuf + sizeof(s2ibuf) -1;
 475    *cp = '\0';
 476    i = signo;
 477    do {
 478       *--cp = "0123456789"[i % 10];
 479       i /= 10;
 480    } while (i != 0);
 481    write(fd, cp, PTR2SIZE((s2ibuf + sizeof(s2ibuf) -1) - cp));
 482
 483    write(fd, _X(":\n"));
 484
 485    if (_nyd_infos[n_NELEM(_nyd_infos) - 1].ni_file != NULL)
 486       for (i = _nyd_curr, nip = _nyd_infos + i; i < n_NELEM(_nyd_infos); ++i)
 487          _nyd_print(fd, nip++);
 488    for (i = 0, nip = _nyd_infos; i < _nyd_curr; ++i)
 489       _nyd_print(fd, nip++);
 490
 491    write(fd, _X("----------\nCome up to the lab and see what's on the slab\n"));
 492
 493    if (fd != STDERR_FILENO) {
 494       write(STDERR_FILENO, _X("Crash NYD listing written to "));
 495       write(STDERR_FILENO, pathbuf, fnl);
 496       write(STDERR_FILENO, _X("\n"));
 497 # undef _X
 498
 499       close(fd);
 500    }
 501
 502    sigemptyset(&xset);
 503    sigaddset(&xset, signo);
 504    sigprocmask(SIG_UNBLOCK, &xset, NULL);
 505    n_raise(signo);
 506    for (;;)
 507       _exit(n_EXIT_ERR);
 508 }
 509 #endif /* HAVE_NYD */
 510
 511 /* s-it-mode */