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    if(n_pid == 0)
 183       n_pid = getpid();
 184    kill(n_pid, signo);
 185    NYD2_LEAVE;
 186 }
 187
 188 FL sighandler_type
 189 safe_signal(int signum, sighandler_type handler)
 190 {
 191    struct sigaction nact, oact;
 192    sighandler_type rv;
 193    NYD2_ENTER;
 194
 195    nact.sa_handler = handler;
 196    sigfillset(&nact.sa_mask);
 197    nact.sa_flags = SA_RESTART;
 198    rv = (sigaction(signum, &nact, &oact) != 0) ? SIG_ERR : oact.sa_handler;
 199    NYD2_LEAVE;
 200    return rv;
 201 }
 202
 203 FL n_sighdl_t
 204 n_signal(int signo, n_sighdl_t hdl){
 205    struct sigaction nact, oact;
 206    NYD2_ENTER;
 207
 208    nact.sa_handler = hdl;
 209    sigfillset(&nact.sa_mask);
 210    nact.sa_flags = 0;
 211    hdl = (sigaction(signo, &nact, &oact) != 0) ? SIG_ERR : oact.sa_handler;
 212    NYD2_LEAVE;
 213    return hdl;
 214 }
 215
 216 FL void
 217 hold_all_sigs(void)
 218 {
 219    NYD2_ENTER;
 220    if (_alls_depth++ == 0) {
 221       sigfillset(&_alls_nset);
 222       sigdelset(&_alls_nset, SIGABRT);
 223 #ifdef SIGBUS
 224       sigdelset(&_alls_nset, SIGBUS);
 225 #endif
 226       sigdelset(&_alls_nset, SIGFPE);
 227       sigdelset(&_alls_nset, SIGILL);
 228       sigdelset(&_alls_nset, SIGKILL);
 229       sigdelset(&_alls_nset, SIGSEGV);
 230       sigdelset(&_alls_nset, SIGSTOP);
 231
 232       sigdelset(&_alls_nset, SIGCHLD);
 233       sigprocmask(SIG_BLOCK, &_alls_nset, &_alls_oset);
 234    }
 235    NYD2_LEAVE;
 236 }
 237
 238 FL void
 239 rele_all_sigs(void)
 240 {
 241    NYD2_ENTER;
 242    if (--_alls_depth == 0)
 243       sigprocmask(SIG_SETMASK, &_alls_oset, (sigset_t*)NULL);
 244    NYD2_LEAVE;
 245 }
 246
 247 FL void
 248 hold_sigs(void)
 249 {
 250    NYD2_ENTER;
 251    if (_hold_sigdepth++ == 0) {
 252       sigemptyset(&_hold_nset);
 253       sigaddset(&_hold_nset, SIGHUP);
 254       sigaddset(&_hold_nset, SIGINT);
 255       sigaddset(&_hold_nset, SIGQUIT);
 256       sigprocmask(SIG_BLOCK, &_hold_nset, &_hold_oset);
 257    }
 258    NYD2_LEAVE;
 259 }
 260
 261 FL void
 262 rele_sigs(void)
 263 {
 264    NYD2_ENTER;
 265    if (--_hold_sigdepth == 0)
 266       sigprocmask(SIG_SETMASK, &_hold_oset, NULL);
 267    NYD2_LEAVE;
 268 }
 269
 270 /* TODO This is temporary gracyness */
 271 static struct n_sigman *n__sigman;
 272 static void n__sigman_hdl(int signo);
 273 static void
 274 n__sigman_hdl(int signo){
 275    NYD_X; /* Signal handler */
 276    n__sigman->sm_signo = signo;
 277    siglongjmp(n__sigman->sm_jump, 1);
 278 }
 279
 280 FL int
 281 n__sigman_enter(struct n_sigman *self, int flags){
 282    /* TODO no error checking when installing sighdls */
 283    int rv;
 284    NYD2_ENTER;
 285
 286    if((int)flags >= 0){
 287       self->sm_flags = (enum n_sigman_flags)flags;
 288       self->sm_signo = 0;
 289       self->sm_outer = n__sigman;
 290       if(flags & n_SIGMAN_HUP)
 291          self->sm_ohup = safe_signal(SIGHUP, &n__sigman_hdl);
 292       if(flags & n_SIGMAN_INT)
 293          self->sm_oint = safe_signal(SIGINT, &n__sigman_hdl);
 294       if(flags & n_SIGMAN_QUIT)
 295          self->sm_oquit = safe_signal(SIGQUIT, &n__sigman_hdl);
 296       if(flags & n_SIGMAN_PIPE)
 297          self->sm_opipe = safe_signal(SIGPIPE, &n__sigman_hdl);
 298       n__sigman = self;
 299       rv = 0;
 300    }else{
 301       flags = self->sm_flags;
 302
 303       /* Just in case of a race (signal while holding and ignoring? really?) */
 304       if(!(flags & n__SIGMAN_PING)){
 305          if(flags & n_SIGMAN_HUP)
 306             safe_signal(SIGHUP, SIG_IGN);
 307          if(flags & n_SIGMAN_INT)
 308             safe_signal(SIGINT, SIG_IGN);
 309          if(flags & n_SIGMAN_QUIT)
 310             safe_signal(SIGQUIT, SIG_IGN);
 311          if(flags & n_SIGMAN_PIPE)
 312             safe_signal(SIGPIPE, SIG_IGN);
 313       }
 314       rv = self->sm_signo;
 315       /* The signal mask has been restored, but of course rele_sigs() has
 316        * already been called: account for restoration due to jump */
 317       ++_hold_sigdepth;
 318    }
 319    rele_sigs();
 320    NYD2_LEAVE;
 321    return rv;
 322 }
 323
 324 FL void
 325 n_sigman_cleanup_ping(struct n_sigman *self){
 326    ui32_t f;
 327    NYD2_ENTER;
 328
 329    hold_sigs();
 330
 331    f = self->sm_flags;
 332    f |= n__SIGMAN_PING;
 333    self->sm_flags = f;
 334
 335    if(f & n_SIGMAN_HUP)
 336       safe_signal(SIGHUP, SIG_IGN);
 337    if(f & n_SIGMAN_INT)
 338       safe_signal(SIGINT, SIG_IGN);
 339    if(f & n_SIGMAN_QUIT)
 340       safe_signal(SIGQUIT, SIG_IGN);
 341    if(f & n_SIGMAN_PIPE)
 342       safe_signal(SIGPIPE, SIG_IGN);
 343
 344    rele_sigs();
 345    NYD2_LEAVE;
 346 }
 347
 348 FL void
 349 n_sigman_leave(struct n_sigman *self,
 350       enum n_sigman_flags reraise_flags){
 351    ui32_t f;
 352    int sig;
 353    NYD2_ENTER;
 354
 355    hold_sigs();
 356    n__sigman = self->sm_outer;
 357
 358    f = self->sm_flags;
 359    if(f & n_SIGMAN_HUP)
 360       safe_signal(SIGHUP, self->sm_ohup);
 361    if(f & n_SIGMAN_INT)
 362       safe_signal(SIGINT, self->sm_oint);
 363    if(f & n_SIGMAN_QUIT)
 364       safe_signal(SIGQUIT, self->sm_oquit);
 365    if(f & n_SIGMAN_PIPE)
 366       safe_signal(SIGPIPE, self->sm_opipe);
 367
 368    rele_sigs();
 369
 370    sig = 0;
 371    switch(self->sm_signo){
 372    case SIGPIPE:
 373       if((reraise_flags & n_SIGMAN_PIPE) ||
 374             ((reraise_flags & n_SIGMAN_NTTYOUT_PIPE) &&
 375              !(n_psonce & n_PSO_TTYOUT)))
 376          sig = SIGPIPE;
 377       break;
 378    case SIGHUP:
 379       if(reraise_flags & n_SIGMAN_HUP)
 380          sig = SIGHUP;
 381       break;
 382    case SIGINT:
 383       if(reraise_flags & n_SIGMAN_INT)
 384          sig = SIGINT;
 385       break;
 386    case SIGQUIT:
 387       if(reraise_flags & n_SIGMAN_QUIT)
 388          sig = SIGQUIT;
 389       break;
 390    default:
 391       break;
 392    }
 393
 394    NYD2_LEAVE;
 395    if(sig != 0){
 396       sigset_t cset;
 397
 398       sigemptyset(&cset);
 399       sigaddset(&cset, sig);
 400       sigprocmask(SIG_UNBLOCK, &cset, NULL);
 401       n_raise(sig);
 402    }
 403 }
 404
 405 FL int
 406 n_sigman_peek(void){
 407    int rv;
 408    NYD2_ENTER;
 409    rv = 0;
 410    NYD2_LEAVE;
 411    return rv;
 412 }
 413
 414 FL void
 415 n_sigman_consume(void){
 416    NYD2_ENTER;
 417    NYD2_LEAVE;
 418 }
 419
 420 #ifdef HAVE_NYD
 421 FL void
 422 _nyd_chirp(ui8_t act, char const *file, ui32_t line, char const *fun)
 423 {
 424    struct nyd_info *nip = _nyd_infos;
 425
 426    if (_nyd_curr != n_NELEM(_nyd_infos))
 427       nip += _nyd_curr++;
 428    else
 429       _nyd_curr = 1;
 430    nip->ni_file = file;
 431    nip->ni_fun = fun;
 432    nip->ni_chirp_line = ((ui32_t)(act & 0x3) << 29) | (line & 0x1FFFFFFFu);
 433    nip->ni_level = ((act == 0) ? _nyd_level
 434          : (act == 1) ? ++_nyd_level : _nyd_level--);
 435 }
 436
 437 FL void
 438 _nyd_oncrash(int signo)
 439 {
 440    char pathbuf[PATH_MAX], s2ibuf[32], *cp;
 441    struct sigaction xact;
 442    sigset_t xset;
 443    struct nyd_info *nip;
 444    int fd;
 445    size_t i, fnl;
 446    char const *tmpdir;
 447
 448    n_LCTA(sizeof("./") -1 + sizeof(VAL_UAGENT) -1 + sizeof(".dat") < PATH_MAX,
 449       "System limits too low for fixed-size buffer operation");
 450
 451    xact.sa_handler = SIG_DFL;
 452    sigemptyset(&xact.sa_mask);
 453    xact.sa_flags = 0;
 454    sigaction(signo, &xact, NULL);
 455
 456    i = strlen(tmpdir = ok_vlook(TMPDIR));
 457    fnl = sizeof(VAL_UAGENT) -1;
 458
 459    if (i + 1 + fnl + 1 + sizeof(".dat") > sizeof(pathbuf)) {
 460       (cp = pathbuf)[0] = '.';
 461       i = 1;
 462    } else
 463       memcpy(cp = pathbuf, tmpdir, i);
 464    cp[i++] = '/'; /* xxx pathsep */
 465    memcpy(cp += i, VAL_UAGENT, fnl);
 466    i += fnl;
 467    memcpy(cp += fnl, ".dat", sizeof(".dat"));
 468    fnl = i + sizeof(".dat") -1;
 469
 470    if ((fd = open(pathbuf, O_WRONLY | O_CREAT | O_EXCL, 0666)) == -1)
 471       fd = STDERR_FILENO;
 472
 473 # undef _X
 474 # define _X(X) (X), sizeof(X) -1
 475    write(fd, _X("\n\nNYD: program dying due to signal "));
 476
 477    cp = s2ibuf + sizeof(s2ibuf) -1;
 478    *cp = '\0';
 479    i = signo;
 480    do {
 481       *--cp = "0123456789"[i % 10];
 482       i /= 10;
 483    } while (i != 0);
 484    write(fd, cp, PTR2SIZE((s2ibuf + sizeof(s2ibuf) -1) - cp));
 485
 486    write(fd, _X(":\n"));
 487
 488    if (_nyd_infos[n_NELEM(_nyd_infos) - 1].ni_file != NULL)
 489       for (i = _nyd_curr, nip = _nyd_infos + i; i < n_NELEM(_nyd_infos); ++i)
 490          _nyd_print(fd, nip++);
 491    for (i = 0, nip = _nyd_infos; i < _nyd_curr; ++i)
 492       _nyd_print(fd, nip++);
 493
 494    write(fd, _X("----------\nCome up to the lab and see what's on the slab\n"));
 495
 496    if (fd != STDERR_FILENO) {
 497       write(STDERR_FILENO, _X("Crash NYD listing written to "));
 498       write(STDERR_FILENO, pathbuf, fnl);
 499       write(STDERR_FILENO, _X("\n"));
 500 # undef _X
 501
 502       close(fd);
 503    }
 504
 505    sigemptyset(&xset);
 506    sigaddset(&xset, signo);
 507    sigprocmask(SIG_UNBLOCK, &xset, NULL);
 508    n_raise(signo);
 509    for (;;)
 510       _exit(n_EXIT_ERR);
 511 }
 512 #endif /* HAVE_NYD */
 513
 514 /* s-it-mode */