lib/sigevent.c

   1 /* Quagga signal handling functions.
   2  * Copyright (C) 2004 Paul Jakma,
   3  *
   4  * This file is part of Quagga.
   5  *
   6  * Quagga is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the
   8  * Free Software Foundation; either version 2, or (at your option) any
   9  * later version.
  10  *
  11  * Quagga is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; see the file COPYING; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #include <zebra.h>
  22 #include <sigevent.h>
  23 #include <log.h>
  24 #include <memory.h>
  25 #include <lib_errors.h>
  26
  27 #ifdef HAVE_UCONTEXT_H
  28 #ifdef GNU_LINUX
  29 /* get REG_EIP from ucontext.h */
  30 #ifndef __USE_GNU
  31 #define __USE_GNU
  32 #endif /* __USE_GNU */
  33 #endif /* GNU_LINUX */
  34 #include <ucontext.h>
  35 #endif /* HAVE_UCONTEXT_H */
  36
  37
  38 /* master signals descriptor struct */
  39 static struct frr_sigevent_master_t {
  40         struct thread *t;
  41
  42         struct frr_signal_t *signals;
  43         int sigc;
  44
  45         volatile sig_atomic_t caught;
  46 } sigmaster;
  47
  48 /* Generic signal handler
  49  * Schedules signal event thread
  50  */
  51 static void frr_signal_handler(int signo)
  52 {
  53         int i;
  54         struct frr_signal_t *sig;
  55
  56         for (i = 0; i < sigmaster.sigc; i++) {
  57                 sig = &(sigmaster.signals[i]);
  58
  59                 if (sig->signal == signo)
  60                         sig->caught = 1;
  61         }
  62
  63         sigmaster.caught = 1;
  64 }
  65
  66 /*
  67  * Check whether any signals have been received and are pending. This is done
  68  * with the application's key signals blocked. The complete set of signals
  69  * is returned in 'setp', so the caller can restore them when appropriate.
  70  * If there are pending signals, returns 'true', 'false' otherwise.
  71  */
  72 bool frr_sigevent_check(sigset_t *setp)
  73 {
  74         sigset_t blocked;
  75         int i;
  76         bool ret;
  77
  78         sigemptyset(setp);
  79         sigemptyset(&blocked);
  80
  81         /* Set up mask of application's signals */
  82         for (i = 0; i < sigmaster.sigc; i++)
  83                 sigaddset(&blocked, sigmaster.signals[i].signal);
  84
  85         pthread_sigmask(SIG_BLOCK, &blocked, setp);
  86
  87         /* Now that the application's signals are blocked, test. */
  88         ret = (sigmaster.caught != 0);
  89
  90         return ret;
  91 }
  92
  93 /* check if signals have been caught and run appropriate handlers */
  94 int frr_sigevent_process(void)
  95 {
  96         struct frr_signal_t *sig;
  97         int i;
  98 #ifdef SIGEVENT_BLOCK_SIGNALS
  99         /* shouldn't need to block signals, but potentially may be needed */
 100         sigset_t newmask, oldmask;
 101
 102         /*
 103          * Block most signals, but be careful not to defer SIGTRAP because
 104          * doing so breaks gdb, at least on NetBSD 2.0.  Avoid asking to
 105          * block SIGKILL, just because we shouldn't be able to do so.
 106          */
 107         sigfillset(&newmask);
 108         sigdelset(&newmask, SIGTRAP);
 109         sigdelset(&newmask, SIGKILL);
 110
 111         if ((sigprocmask(SIG_BLOCK, &newmask, &oldmask)) < 0) {
 112                 flog_err_sys(EC_LIB_SYSTEM_CALL,
 113                              "frr_signal_timer: couldnt block signals!");
 114                 return -1;
 115         }
 116 #endif /* SIGEVENT_BLOCK_SIGNALS */
 117
 118         if (sigmaster.caught > 0) {
 119                 sigmaster.caught = 0;
 120                 /* must not read or set sigmaster.caught after here,
 121                  * race condition with per-sig caught flags if one does
 122                  */
 123
 124                 for (i = 0; i < sigmaster.sigc; i++) {
 125                         sig = &(sigmaster.signals[i]);
 126
 127                         if (sig->caught > 0) {
 128                                 sig->caught = 0;
 129                                 if (sig->handler)
 130                                         sig->handler();
 131                         }
 132                 }
 133         }
 134
 135 #ifdef SIGEVENT_BLOCK_SIGNALS
 136         if (sigprocmask(SIG_UNBLOCK, &oldmask, NULL) < 0)
 137                 return -1;
 138 #endif /* SIGEVENT_BLOCK_SIGNALS */
 139
 140         return 0;
 141 }
 142
 143 #ifdef SIGEVENT_SCHEDULE_THREAD
 144 /* timer thread to check signals. shouldn't be needed */
 145 void frr_signal_timer(struct thread *t)
 146 {
 147         struct frr_sigevent_master_t *sigm;
 148
 149         sigm = THREAD_ARG(t);
 150         sigm->t = NULL;
 151         thread_add_timer(sigm->t->master, frr_signal_timer, &sigmaster,
 152                          FRR_SIGNAL_TIMER_INTERVAL, &sigm->t);
 153         frr_sigevent_process();
 154 }
 155 #endif /* SIGEVENT_SCHEDULE_THREAD */
 156
 157 /* Initialization of signal handles. */
 158 /* Signal wrapper. */
 159 static int signal_set(int signo)
 160 {
 161         int ret;
 162         struct sigaction sig;
 163         struct sigaction osig;
 164
 165         sig.sa_handler = &frr_signal_handler;
 166         sigfillset(&sig.sa_mask);
 167         sig.sa_flags = 0;
 168         if (signo == SIGALRM) {
 169 #ifdef SA_INTERRUPT
 170                 sig.sa_flags |= SA_INTERRUPT; /* SunOS */
 171 #endif
 172         } else {
 173 #ifdef SA_RESTART
 174                 sig.sa_flags |= SA_RESTART;
 175 #endif /* SA_RESTART */
 176         }
 177
 178         ret = sigaction(signo, &sig, &osig);
 179         if (ret < 0)
 180                 return ret;
 181         else
 182                 return 0;
 183 }
 184
 185 /* XXX This function should be enhanced to support more platforms
 186        (it currently works only on Linux/x86). */
 187 static void *program_counter(void *context)
 188 {
 189 #ifdef HAVE_UCONTEXT_H
 190 #ifdef GNU_LINUX
 191 /* these are from GNU libc, rather than Linux, strictly speaking */
 192 #if defined(REG_EIP)
 193 #  define REG_INDEX REG_EIP
 194 #elif defined(REG_RIP)
 195 #  define REG_INDEX REG_RIP
 196 #elif defined(__powerpc__)
 197 #  define REG_INDEX 32
 198 #endif
 199 #endif                 /* GNU_LINUX */
 200
 201 #ifdef REG_INDEX
 202 #ifdef HAVE_UCONTEXT_T_UC_MCONTEXT_GREGS
 203 #  define REGS gregs[REG_INDEX]
 204 #elif defined(HAVE_UCONTEXT_T_UC_MCONTEXT_UC_REGS)
 205 #  define REGS uc_regs->gregs[REG_INDEX]
 206 #endif /* HAVE_UCONTEXT_T_UC_MCONTEXT_GREGS */
 207 #endif /* REG_INDEX */
 208
 209 #ifdef REGS
 210         if (context)
 211                 return (void *)(((ucontext_t *)context)->uc_mcontext.REGS);
 212 #elif defined(HAVE_UCONTEXT_T_UC_MCONTEXT_REGS__NIP)
 213         /* older Linux / struct pt_regs ? */
 214         if (context)
 215                 return (void *)(((ucontext_t *)context)->uc_mcontext.regs->nip);
 216 #endif /* REGS */
 217
 218 #endif /* HAVE_UCONTEXT_H */
 219         return NULL;
 220 }
 221
 222 static void __attribute__((noreturn))
 223 exit_handler(int signo, siginfo_t *siginfo, void *context)
 224 {
 225         void *pc = program_counter(context);
 226
 227         zlog_signal(signo, "exiting...", siginfo, pc);
 228         _exit(128 + signo);
 229 }
 230
 231 static void __attribute__((noreturn))
 232 core_handler(int signo, siginfo_t *siginfo, void *context)
 233 {
 234         void *pc = program_counter(context);
 235
 236         /* make sure we don't hang in here.  default for SIGALRM is terminate.
 237          * - if we're in backtrace for more than a second, abort. */
 238         struct sigaction sa_default = {.sa_handler = SIG_DFL};
 239
 240         sigaction(SIGALRM, &sa_default, NULL);
 241         sigaction(signo, &sa_default, NULL);
 242
 243         sigset_t sigset;
 244
 245         sigemptyset(&sigset);
 246         sigaddset(&sigset, SIGALRM);
 247         sigprocmask(SIG_UNBLOCK, &sigset, NULL);
 248
 249         alarm(1);
 250
 251         zlog_signal(signo, "aborting...", siginfo, pc);
 252
 253         /* dump memory stats on core */
 254         log_memstats(stderr, "core_handler");
 255
 256         zlog_tls_buffer_fini();
 257
 258         /* give the kernel a chance to generate a coredump */
 259         sigaddset(&sigset, signo);
 260         sigprocmask(SIG_UNBLOCK, &sigset, NULL);
 261         raise(signo);
 262
 263         /* only chance to end up here is if the default action for signo is
 264          * something other than kill or coredump the process
 265          */
 266         _exit(128 + signo);
 267 }
 268
 269 static void trap_default_signals(void)
 270 {
 271         static const int core_signals[] = {
 272                 SIGQUIT, SIGILL, SIGABRT,
 273 #ifdef SIGEMT
 274                 SIGEMT,
 275 #endif
 276                 SIGFPE,  SIGBUS, SIGSEGV,
 277 #ifdef SIGSYS
 278                 SIGSYS,
 279 #endif
 280 #ifdef SIGXCPU
 281                 SIGXCPU,
 282 #endif
 283 #ifdef SIGXFSZ
 284                 SIGXFSZ,
 285 #endif
 286         };
 287         static const int exit_signals[] = {
 288                 SIGHUP,    SIGINT, SIGALRM, SIGTERM, SIGUSR1, SIGUSR2,
 289 #ifdef SIGPOLL
 290                 SIGPOLL,
 291 #endif
 292 #ifdef SIGVTALRM
 293                 SIGVTALRM,
 294 #endif
 295 #ifdef SIGSTKFLT
 296                 SIGSTKFLT,
 297 #endif
 298         };
 299         static const int ignore_signals[] = {
 300                 SIGPIPE,
 301         };
 302         static const struct {
 303                 const int *sigs;
 304                 unsigned int nsigs;
 305                 void (*handler)(int signo, siginfo_t *info, void *context);
 306         } sigmap[] = {
 307                 {core_signals, array_size(core_signals), core_handler},
 308                 {exit_signals, array_size(exit_signals), exit_handler},
 309                 {ignore_signals, array_size(ignore_signals), NULL},
 310         };
 311         unsigned int i;
 312
 313         for (i = 0; i < array_size(sigmap); i++) {
 314                 unsigned int j;
 315
 316                 for (j = 0; j < sigmap[i].nsigs; j++) {
 317                         struct sigaction oact;
 318                         if ((sigaction(sigmap[i].sigs[j], NULL, &oact) == 0)
 319                             && (oact.sa_handler == SIG_DFL)) {
 320                                 struct sigaction act;
 321                                 sigfillset(&act.sa_mask);
 322                                 if (sigmap[i].handler == NULL) {
 323                                         act.sa_handler = SIG_IGN;
 324                                         act.sa_flags = 0;
 325                                 } else {
 326                                         /* Request extra arguments to signal
 327                                          * handler. */
 328                                         act.sa_sigaction = sigmap[i].handler;
 329                                         act.sa_flags = SA_SIGINFO;
 330 #ifdef SA_RESETHAND
 331                                         /* don't try to print backtraces
 332                                          * recursively */
 333                                         if (sigmap[i].handler == core_handler)
 334                                                 act.sa_flags |= SA_RESETHAND;
 335 #endif
 336                                 }
 337                                 if (sigaction(sigmap[i].sigs[j], &act, NULL)
 338                                     < 0)
 339                                         flog_err(
 340                                                 EC_LIB_SYSTEM_CALL,
 341                                                 "Unable to set signal handler for signal %d: %s",
 342                                                 sigmap[i].sigs[j],
 343                                                 safe_strerror(errno));
 344                         }
 345                 }
 346         }
 347 }
 348
 349 void signal_init(struct thread_master *m, int sigc,
 350                  struct frr_signal_t signals[])
 351 {
 352
 353         int i = 0;
 354         struct frr_signal_t *sig;
 355
 356         /* First establish some default handlers that can be overridden by
 357            the application. */
 358         trap_default_signals();
 359
 360         while (i < sigc) {
 361                 sig = &signals[i];
 362                 if (signal_set(sig->signal) < 0)
 363                         exit(-1);
 364                 i++;
 365         }
 366
 367         sigmaster.sigc = sigc;
 368         sigmaster.signals = signals;
 369
 370 #ifdef SIGEVENT_SCHEDULE_THREAD
 371         sigmaster.t = NULL;
 372         thread_add_timer(m, frr_signal_timer, &sigmaster,
 373                          FRR_SIGNAL_TIMER_INTERVAL, &sigmaster.t);
 374 #endif /* SIGEVENT_SCHEDULE_THREAD */
 375 }