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 - 2018 Steffen (Daode) Nurpmeso <steffen@sdaoden.eu>.
   6  * SPDX-License-Identifier: BSD-3-Clause TODO ISC (better: drop)
   7  */
   8 /*
   9  * Copyright (c) 1980, 1993
  10  *      The Regents of the University of California.  All rights reserved.
  11  *
  12  * Redistribution and use in source and binary forms, with or without
  13  * modification, are permitted provided that the following conditions
  14  * are met:
  15  * 1. Redistributions of source code must retain the above copyright
  16  *    notice, this list of conditions and the following disclaimer.
  17  * 2. Redistributions in binary form must reproduce the above copyright
  18  *    notice, this list of conditions and the following disclaimer in the
  19  *    documentation and/or other materials provided with the distribution.
  20  * 3. 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 #undef n_FILE
  37 #define n_FILE signal
  38
  39 #ifndef HAVE_AMALGAMATION
  40 # include "nail.h"
  41 #endif
  42
  43 /*
  44  * TODO At the beginning of November 2015 -- for v14.9 -- i've tried for one
  45  * TODO and a half week to convert this codebase to SysV style signal handling,
  46  * TODO meaning no SA_RESTART and EINTR in a lot of places and error reporting
  47  * TODO up the chain.   I failed miserably, not only because S/MIME / SSL but
  48  * TODO also because of general frustration.  Directly after v14.9 i will strip
  49  * TODO ANYTHING off the codebase (socket stuff etc.) and keep only the very
  50  * TODO core, doing namespace and type cleanup and convert this core to a clean
  51  * TODO approach, from which i plan to start this thing anew.
  52  * TODO For now i introduced the n_sigman, yet another hack, to be used in a
  53  * TODO few places.
  54  * TODO The real solution:
  55  * TODO - No SA_RESTART.  Just like for my C++ library: encapsulate EINTR in
  56  * TODO   userspace at the systemcall (I/O rewrite: drop stdio), normal
  57  * TODO   interface auto-restarts, special _intr() series return EINTR.
  58  * TODO   Do n_sigman_poll()/peek()/whatever whenever desired for the former,
  59  * TODO   report errors up the call chain, have places where operations can be
  60  * TODO   "properly" aborted.
  61  * TODO - We save the initial signal settings upon program startup.
  62  * TODO - We register our sigman handlers once, at program startup.
  63  * TODO   Maximally, and most likely only due to lack of atomic CAS, ignore
  64  * TODO   or block some signals temporarily.  Best if not.
  65  * TODO   The signal handlers only set a flag.  Block all signals for handler
  66  * TODO   execution, like this we are safe to "set the first signal was x".
  67  * TODO - In interactive context, ignore SIGTERM.
  68  * TODO   I.e., see the POSIX standard for what a shell does.
  69  * TODO - In non-interactive context, don't know anything about job control!?!
  70  * TODO - Place child processes in their own process group.  Restore the signal
  71  * TODO   mask back to the saved original one for them, before exec.
  72  * TODO - Except for job control related (<-> interactive) ignore any signals
  73  * TODO   while we are "behind" a child that occupies the terminal.  For those,
  74  * TODO   perform proper terminal attribute handling.  For childs that don't
  75  * TODO   occupy the terminal we "are the shell" and should therefore manage
  76  * TODO   them accordingly, including termination request as necessary.
  77  * TODO   And if we have a worker in a pipeline, we need to manage it and deal
  78  * TODO   with it properly, WITHOUT temporary signal overwrites.
  79  * TODO - No more jumps.
  80  * TODO - (When sockets will be reintroduced, non-blocking.)
  81  * TODO - (When SSL is reintroduced, memory BIO.  It MAY be necessary to
  82  * TODO   temporarily block signals during a few SSL functions?  Read SSL docu!
  83  * TODO   But i prefer blocking since it's a single syscall, not temporary
  84  * TODO   SA_RESTART setting, since that has to be done for every signal.)
  85  */
  86
  87 #ifdef HAVE_NYD
  88 struct nyd_info {
  89    char const  *ni_file;
  90    char const  *ni_fun;
  91    ui32_t      ni_chirp_line;
  92    ui32_t      ni_level;
  93 };
  94 #endif
  95
  96 /* {hold,rele}_all_sigs() */
  97 static size_t           _alls_depth;
  98 static sigset_t         _alls_nset, _alls_oset;
  99
 100 /* {hold,rele}_sigs() */
 101 static size_t           _hold_sigdepth;
 102 static sigset_t         _hold_nset, _hold_oset;
 103
 104 /* NYD, memory pool debug */
 105 #ifdef HAVE_NYD
 106 static ui32_t           _nyd_curr, _nyd_level;
 107 static struct nyd_info  _nyd_infos[NYD_CALLS_MAX];
 108 #endif
 109
 110 /* */
 111 #ifdef HAVE_NYD
 112 static void    _nyd_print(int fd, struct nyd_info *nip);
 113 #endif
 114
 115 #ifdef HAVE_NYD
 116 static void
 117 _nyd_print(int fd, struct nyd_info *nip)
 118 {
 119    char buf[80];
 120    union {int i; size_t z;} u;
 121
 122    u.i = snprintf(buf, sizeof buf,
 123          "%c [%2" PRIu32 "] %.25s (%.40s:%" PRIu32 ")\n",
 124          "=><"[(nip->ni_chirp_line >> 29) & 0x3], nip->ni_level, nip->ni_fun,
 125          nip->ni_file, (nip->ni_chirp_line & 0x1FFFFFFFu));
 126    if (u.i > 0) {
 127       u.z = u.i;
 128       if (u.z > sizeof buf)
 129          u.z = sizeof buf - 1; /* (Skip \0) */
 130       write(fd, buf, u.z);
 131    }
 132 }
 133 #endif
 134
 135 #ifdef HAVE_DEVEL
 136 FL int
 137 c_sigstate(void *vp){ /* TODO remove again */
 138    struct{
 139       int val;
 140       char const name[12];
 141    } const *hdlp, hdla[] = {
 142       {SIGINT, "SIGINT"}, {SIGHUP, "SIGHUP"}, {SIGQUIT, "SIGQUIT"},
 143       {SIGTSTP, "SIGTSTP"}, {SIGTTIN, "SIGTTIN"}, {SIGTTOU, "SIGTTOU"},
 144       {SIGCHLD, "SIGCHLD"}, {SIGPIPE, "SIGPIPE"}
 145    };
 146    char const *cp;
 147    NYD2_ENTER;
 148
 149    if((cp = vp) != NULL && cp[0] != '\0'){
 150       if(!asccasecmp(&cp[1], "all")){
 151          if(cp[0] == '+')
 152             hold_all_sigs();
 153          else
 154             rele_all_sigs();
 155       }else if(!asccasecmp(&cp[1], "hold")){
 156          if(cp[0] == '+')
 157             hold_sigs();
 158          else
 159             rele_sigs();
 160       }
 161    }
 162
 163    fprintf(n_stdout, "alls_depth %zu, hold_sigdepth %zu\nHandlers:\n",
 164       _alls_depth, _hold_sigdepth);
 165    for(hdlp = hdla; hdlp < &hdla[n_NELEM(hdla)]; ++hdlp){
 166       sighandler_type shp;
 167
 168       shp = safe_signal(hdlp->val, SIG_IGN);
 169       safe_signal(hdlp->val, shp);
 170       fprintf(n_stdout, "  %s: %p (%s)\n", hdlp->name, shp,
 171          (shp == SIG_ERR ? "ERR" : (shp == SIG_DFL ? "DFL"
 172             : (shp == SIG_IGN ? "IGN" : "ptf?"))));
 173    }
 174    NYD2_LEAVE;
 175    return OKAY;
 176 }
 177 #endif /* HAVE_DEVEL */
 178
 179 FL void
 180 n_raise(int signo)
 181 {
 182    NYD2_ENTER;
 183    if(n_pid == 0)
 184       n_pid = getpid();
 185    kill(n_pid, signo);
 186    NYD2_LEAVE;
 187 }
 188
 189 FL sighandler_type
 190 safe_signal(int signum, sighandler_type handler)
 191 {
 192    struct sigaction nact, oact;
 193    sighandler_type rv;
 194    NYD2_ENTER;
 195
 196    nact.sa_handler = handler;
 197    sigfillset(&nact.sa_mask);
 198    nact.sa_flags = SA_RESTART;
 199    rv = (sigaction(signum, &nact, &oact) != 0) ? SIG_ERR : oact.sa_handler;
 200    NYD2_LEAVE;
 201    return rv;
 202 }
 203
 204 FL n_sighdl_t
 205 n_signal(int signo, n_sighdl_t hdl){
 206    struct sigaction nact, oact;
 207    NYD2_ENTER;
 208
 209    nact.sa_handler = hdl;
 210    sigfillset(&nact.sa_mask);
 211    nact.sa_flags = 0;
 212    hdl = (sigaction(signo, &nact, &oact) != 0) ? SIG_ERR : oact.sa_handler;
 213    NYD2_LEAVE;
 214    return hdl;
 215 }
 216
 217 FL void
 218 hold_all_sigs(void)
 219 {
 220    NYD2_ENTER;
 221    if (_alls_depth++ == 0) {
 222       sigfillset(&_alls_nset);
 223       sigdelset(&_alls_nset, SIGABRT);
 224 #ifdef SIGBUS
 225       sigdelset(&_alls_nset, SIGBUS);
 226 #endif
 227       sigdelset(&_alls_nset, SIGFPE);
 228       sigdelset(&_alls_nset, SIGILL);
 229       sigdelset(&_alls_nset, SIGKILL);
 230       sigdelset(&_alls_nset, SIGSEGV);
 231       sigdelset(&_alls_nset, SIGSTOP);
 232
 233       sigdelset(&_alls_nset, SIGCHLD);
 234       sigprocmask(SIG_BLOCK, &_alls_nset, &_alls_oset);
 235    }
 236    NYD2_LEAVE;
 237 }
 238
 239 FL void
 240 rele_all_sigs(void)
 241 {
 242    NYD2_ENTER;
 243    if (--_alls_depth == 0)
 244       sigprocmask(SIG_SETMASK, &_alls_oset, (sigset_t*)NULL);
 245    NYD2_LEAVE;
 246 }
 247
 248 FL void
 249 hold_sigs(void)
 250 {
 251    NYD2_ENTER;
 252    if (_hold_sigdepth++ == 0) {
 253       sigemptyset(&_hold_nset);
 254       sigaddset(&_hold_nset, SIGHUP);
 255       sigaddset(&_hold_nset, SIGINT);
 256       sigaddset(&_hold_nset, SIGQUIT);
 257       sigprocmask(SIG_BLOCK, &_hold_nset, &_hold_oset);
 258    }
 259    NYD2_LEAVE;
 260 }
 261
 262 FL void
 263 rele_sigs(void)
 264 {
 265    NYD2_ENTER;
 266    if (--_hold_sigdepth == 0)
 267       sigprocmask(SIG_SETMASK, &_hold_oset, NULL);
 268    NYD2_LEAVE;
 269 }
 270
 271 /* TODO This is temporary gracyness */
 272 static struct n_sigman *n__sigman;
 273 static void n__sigman_hdl(int signo);
 274 static void
 275 n__sigman_hdl(int signo){
 276    NYD_X; /* Signal handler */
 277    n__sigman->sm_signo = signo;
 278    siglongjmp(n__sigman->sm_jump, 1);
 279 }
 280
 281 FL int
 282 n__sigman_enter(struct n_sigman *self, int flags){
 283    /* TODO no error checking when installing sighdls */
 284    int rv;
 285    NYD2_ENTER;
 286
 287    if((int)flags >= 0){
 288       self->sm_flags = (enum n_sigman_flags)flags;
 289       self->sm_signo = 0;
 290       self->sm_outer = n__sigman;
 291       if(flags & n_SIGMAN_HUP)
 292          self->sm_ohup = safe_signal(SIGHUP, &n__sigman_hdl);
 293       if(flags & n_SIGMAN_INT)
 294          self->sm_oint = safe_signal(SIGINT, &n__sigman_hdl);
 295       if(flags & n_SIGMAN_QUIT)
 296          self->sm_oquit = safe_signal(SIGQUIT, &n__sigman_hdl);
 297       if(flags & n_SIGMAN_PIPE)
 298          self->sm_opipe = safe_signal(SIGPIPE, &n__sigman_hdl);
 299       n__sigman = self;
 300       rv = 0;
 301    }else{
 302       flags = self->sm_flags;
 303
 304       /* Just in case of a race (signal while holding and ignoring? really?) */
 305       if(!(flags & n__SIGMAN_PING)){
 306          if(flags & n_SIGMAN_HUP)
 307             safe_signal(SIGHUP, SIG_IGN);
 308          if(flags & n_SIGMAN_INT)
 309             safe_signal(SIGINT, SIG_IGN);
 310          if(flags & n_SIGMAN_QUIT)
 311             safe_signal(SIGQUIT, SIG_IGN);
 312          if(flags & n_SIGMAN_PIPE)
 313             safe_signal(SIGPIPE, SIG_IGN);
 314       }
 315       rv = self->sm_signo;
 316       /* The signal mask has been restored, but of course rele_sigs() has
 317        * already been called: account for restoration due to jump */
 318       ++_hold_sigdepth;
 319    }
 320    rele_sigs();
 321    NYD2_LEAVE;
 322    return rv;
 323 }
 324
 325 FL void
 326 n_sigman_cleanup_ping(struct n_sigman *self){
 327    ui32_t f;
 328    NYD2_ENTER;
 329
 330    hold_sigs();
 331
 332    f = self->sm_flags;
 333    f |= n__SIGMAN_PING;
 334    self->sm_flags = f;
 335
 336    if(f & n_SIGMAN_HUP)
 337       safe_signal(SIGHUP, SIG_IGN);
 338    if(f & n_SIGMAN_INT)
 339       safe_signal(SIGINT, SIG_IGN);
 340    if(f & n_SIGMAN_QUIT)
 341       safe_signal(SIGQUIT, SIG_IGN);
 342    if(f & n_SIGMAN_PIPE)
 343       safe_signal(SIGPIPE, SIG_IGN);
 344
 345    rele_sigs();
 346    NYD2_LEAVE;
 347 }
 348
 349 FL void
 350 n_sigman_leave(struct n_sigman *self,
 351       enum n_sigman_flags reraise_flags){
 352    ui32_t f;
 353    int sig;
 354    NYD2_ENTER;
 355
 356    hold_sigs();
 357    n__sigman = self->sm_outer;
 358
 359    f = self->sm_flags;
 360    if(f & n_SIGMAN_HUP)
 361       safe_signal(SIGHUP, self->sm_ohup);
 362    if(f & n_SIGMAN_INT)
 363       safe_signal(SIGINT, self->sm_oint);
 364    if(f & n_SIGMAN_QUIT)
 365       safe_signal(SIGQUIT, self->sm_oquit);
 366    if(f & n_SIGMAN_PIPE)
 367       safe_signal(SIGPIPE, self->sm_opipe);
 368
 369    rele_sigs();
 370
 371    sig = 0;
 372    switch(self->sm_signo){
 373    case SIGPIPE:
 374       if((reraise_flags & n_SIGMAN_PIPE) ||
 375             ((reraise_flags & n_SIGMAN_NTTYOUT_PIPE) &&
 376              !(n_psonce & n_PSO_TTYOUT)))
 377          sig = SIGPIPE;
 378       break;
 379    case SIGHUP:
 380       if(reraise_flags & n_SIGMAN_HUP)
 381          sig = SIGHUP;
 382       break;
 383    case SIGINT:
 384       if(reraise_flags & n_SIGMAN_INT)
 385          sig = SIGINT;
 386       break;
 387    case SIGQUIT:
 388       if(reraise_flags & n_SIGMAN_QUIT)
 389          sig = SIGQUIT;
 390       break;
 391    default:
 392       break;
 393    }
 394
 395    NYD2_LEAVE;
 396    if(sig != 0){
 397       sigset_t cset;
 398
 399       sigemptyset(&cset);
 400       sigaddset(&cset, sig);
 401       sigprocmask(SIG_UNBLOCK, &cset, NULL);
 402       n_raise(sig);
 403    }
 404 }
 405
 406 FL int
 407 n_sigman_peek(void){
 408    int rv;
 409    NYD2_ENTER;
 410    rv = 0;
 411    NYD2_LEAVE;
 412    return rv;
 413 }
 414
 415 FL void
 416 n_sigman_consume(void){
 417    NYD2_ENTER;
 418    NYD2_LEAVE;
 419 }
 420
 421 #ifdef HAVE_NYD
 422 FL void
 423 _nyd_chirp(ui8_t act, char const *file, ui32_t line, char const *fun)
 424 {
 425    struct nyd_info *nip = _nyd_infos;
 426
 427    if (_nyd_curr != n_NELEM(_nyd_infos))
 428       nip += _nyd_curr++;
 429    else
 430       _nyd_curr = 1;
 431    nip->ni_file = file;
 432    nip->ni_fun = fun;
 433    nip->ni_chirp_line = ((ui32_t)(act & 0x3) << 29) | (line & 0x1FFFFFFFu);
 434    nip->ni_level = ((act == 0) ? _nyd_level
 435          : (act == 1) ? ++_nyd_level : _nyd_level--);
 436 }
 437
 438 FL void
 439 _nyd_oncrash(int signo)
 440 {
 441    char pathbuf[PATH_MAX], s2ibuf[32], *cp;
 442    struct sigaction xact;
 443    sigset_t xset;
 444    struct nyd_info *nip;
 445    int fd;
 446    size_t i, fnl;
 447    char const *tmpdir;
 448
 449    n_LCTA(sizeof("./") -1 + sizeof(VAL_UAGENT) -1 + sizeof(".dat") < PATH_MAX,
 450       "System limits too low for fixed-size buffer operation");
 451
 452    xact.sa_handler = SIG_DFL;
 453    sigemptyset(&xact.sa_mask);
 454    xact.sa_flags = 0;
 455    sigaction(signo, &xact, NULL);
 456
 457    i = strlen(tmpdir = ok_vlook(TMPDIR));
 458    fnl = sizeof(VAL_UAGENT) -1;
 459
 460    if (i + 1 + fnl + 1 + sizeof(".dat") > sizeof(pathbuf)) {
 461       (cp = pathbuf)[0] = '.';
 462       i = 1;
 463    } else
 464       memcpy(cp = pathbuf, tmpdir, i);
 465    cp[i++] = '/'; /* xxx pathsep */
 466    memcpy(cp += i, VAL_UAGENT, fnl);
 467    i += fnl;
 468    memcpy(cp += fnl, ".dat", sizeof(".dat"));
 469    fnl = i + sizeof(".dat") -1;
 470
 471    if ((fd = open(pathbuf, O_WRONLY | O_CREAT | O_EXCL, 0666)) == -1)
 472       fd = STDERR_FILENO;
 473
 474 # undef _X
 475 # define _X(X) (X), sizeof(X) -1
 476    write(fd, _X("\n\nNYD: program dying due to signal "));
 477
 478    cp = s2ibuf + sizeof(s2ibuf) -1;
 479    *cp = '\0';
 480    i = signo;
 481    do {
 482       *--cp = "0123456789"[i % 10];
 483       i /= 10;
 484    } while (i != 0);
 485    write(fd, cp, PTR2SIZE((s2ibuf + sizeof(s2ibuf) -1) - cp));
 486
 487    write(fd, _X(":\n"));
 488
 489    if (_nyd_infos[n_NELEM(_nyd_infos) - 1].ni_file != NULL)
 490       for (i = _nyd_curr, nip = _nyd_infos + i; i < n_NELEM(_nyd_infos); ++i)
 491          _nyd_print(fd, nip++);
 492    for (i = 0, nip = _nyd_infos; i < _nyd_curr; ++i)
 493       _nyd_print(fd, nip++);
 494
 495    write(fd, _X("----------\nCome up to the lab and see what's on the slab\n"));
 496
 497    if (fd != STDERR_FILENO) {
 498       write(STDERR_FILENO, _X("Crash NYD listing written to "));
 499       write(STDERR_FILENO, pathbuf, fnl);
 500       write(STDERR_FILENO, _X("\n"));
 501 # undef _X
 502
 503       close(fd);
 504    }
 505
 506    sigemptyset(&xset);
 507    sigaddset(&xset, signo);
 508    sigprocmask(SIG_UNBLOCK, &xset, NULL);
 509    n_raise(signo);
 510    for (;;)
 511       _exit(n_EXIT_ERR);
 512 }
 513 #endif /* HAVE_NYD */
 514
 515 /* s-it-mode */