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                 ;
 138         return -1;
 139 #endif /* SIGEVENT_BLOCK_SIGNALS */
 140
 141         return 0;
 142 }
 143
 144 #ifdef SIGEVENT_SCHEDULE_THREAD
 145 /* timer thread to check signals. shouldn't be needed */
 146 void frr_signal_timer(struct thread *t)
 147 {
 148         struct frr_sigevent_master_t *sigm;
 149
 150         sigm = THREAD_ARG(t);
 151         sigm->t = NULL;
 152         thread_add_timer(sigm->t->master, frr_signal_timer, &sigmaster,
 153                          FRR_SIGNAL_TIMER_INTERVAL, &sigm->t);
 154         frr_sigevent_process();
 155 }
 156 #endif /* SIGEVENT_SCHEDULE_THREAD */
 157
 158 /* Initialization of signal handles. */
 159 /* Signal wrapper. */
 160 static int signal_set(int signo)
 161 {
 162         int ret;
 163         struct sigaction sig;
 164         struct sigaction osig;
 165
 166         sig.sa_handler = &frr_signal_handler;
 167         sigfillset(&sig.sa_mask);
 168         sig.sa_flags = 0;
 169         if (signo == SIGALRM) {
 170 #ifdef SA_INTERRUPT
 171                 sig.sa_flags |= SA_INTERRUPT; /* SunOS */
 172 #endif
 173         } else {
 174 #ifdef SA_RESTART
 175                 sig.sa_flags |= SA_RESTART;
 176 #endif /* SA_RESTART */
 177         }
 178
 179         ret = sigaction(signo, &sig, &osig);
 180         if (ret < 0)
 181                 return ret;
 182         else
 183                 return 0;
 184 }
 185
 186 /* XXX This function should be enhanced to support more platforms
 187        (it currently works only on Linux/x86). */
 188 static void *program_counter(void *context)
 189 {
 190 #ifdef HAVE_UCONTEXT_H
 191 #ifdef GNU_LINUX
 192 /* these are from GNU libc, rather than Linux, strictly speaking */
 193 #if defined(REG_EIP)
 194 #  define REG_INDEX REG_EIP
 195 #elif defined(REG_RIP)
 196 #  define REG_INDEX REG_RIP
 197 #elif defined(__powerpc__)
 198 #  define REG_INDEX 32
 199 #endif
 200 #endif                 /* GNU_LINUX */
 201
 202 #ifdef REG_INDEX
 203 #ifdef HAVE_UCONTEXT_T_UC_MCONTEXT_GREGS
 204 #  define REGS gregs[REG_INDEX]
 205 #elif defined(HAVE_UCONTEXT_T_UC_MCONTEXT_UC_REGS)
 206 #  define REGS uc_regs->gregs[REG_INDEX]
 207 #endif /* HAVE_UCONTEXT_T_UC_MCONTEXT_GREGS */
 208 #endif /* REG_INDEX */
 209
 210 #ifdef REGS
 211         if (context)
 212                 return (void *)(((ucontext_t *)context)->uc_mcontext.REGS);
 213 #elif defined(HAVE_UCONTEXT_T_UC_MCONTEXT_REGS__NIP)
 214         /* older Linux / struct pt_regs ? */
 215         if (context)
 216                 return (void *)(((ucontext_t *)context)->uc_mcontext.regs->nip);
 217 #endif /* REGS */
 218
 219 #endif /* HAVE_UCONTEXT_H */
 220         return NULL;
 221 }
 222
 223 static void __attribute__((noreturn))
 224 exit_handler(int signo, siginfo_t *siginfo, void *context)
 225 {
 226         void *pc = program_counter(context);
 227
 228         zlog_signal(signo, "exiting...", siginfo, pc);
 229         _exit(128 + signo);
 230 }
 231
 232 static void __attribute__((noreturn))
 233 core_handler(int signo, siginfo_t *siginfo, void *context)
 234 {
 235         void *pc = program_counter(context);
 236
 237         /* make sure we don't hang in here.  default for SIGALRM is terminate.
 238          * - if we're in backtrace for more than a second, abort. */
 239         struct sigaction sa_default = {.sa_handler = SIG_DFL};
 240
 241         sigaction(SIGALRM, &sa_default, NULL);
 242         sigaction(signo, &sa_default, NULL);
 243
 244         sigset_t sigset;
 245
 246         sigemptyset(&sigset);
 247         sigaddset(&sigset, SIGALRM);
 248         sigprocmask(SIG_UNBLOCK, &sigset, NULL);
 249
 250         alarm(1);
 251
 252         zlog_signal(signo, "aborting...", siginfo, pc);
 253
 254         /* dump memory stats on core */
 255         log_memstats(stderr, "core_handler");
 256
 257         zlog_tls_buffer_fini();
 258
 259         /* give the kernel a chance to generate a coredump */
 260         sigaddset(&sigset, signo);
 261         sigprocmask(SIG_UNBLOCK, &sigset, NULL);
 262         raise(signo);
 263
 264         /* only chance to end up here is if the default action for signo is
 265          * something other than kill or coredump the process
 266          */
 267         _exit(128 + signo);
 268 }
 269
 270 static void trap_default_signals(void)
 271 {
 272         static const int core_signals[] = {
 273                 SIGQUIT, SIGILL, SIGABRT,
 274 #ifdef SIGEMT
 275                 SIGEMT,
 276 #endif
 277                 SIGFPE,  SIGBUS, SIGSEGV,
 278 #ifdef SIGSYS
 279                 SIGSYS,
 280 #endif
 281 #ifdef SIGXCPU
 282                 SIGXCPU,
 283 #endif
 284 #ifdef SIGXFSZ
 285                 SIGXFSZ,
 286 #endif
 287         };
 288         static const int exit_signals[] = {
 289                 SIGHUP,    SIGINT, SIGALRM, SIGTERM, SIGUSR1, SIGUSR2,
 290 #ifdef SIGPOLL
 291                 SIGPOLL,
 292 #endif
 293 #ifdef SIGVTALRM
 294                 SIGVTALRM,
 295 #endif
 296 #ifdef SIGSTKFLT
 297                 SIGSTKFLT,
 298 #endif
 299         };
 300         static const int ignore_signals[] = {
 301                 SIGPIPE,
 302         };
 303         static const struct {
 304                 const int *sigs;
 305                 unsigned int nsigs;
 306                 void (*handler)(int signo, siginfo_t *info, void *context);
 307         } sigmap[] = {
 308                 {core_signals, array_size(core_signals), core_handler},
 309                 {exit_signals, array_size(exit_signals), exit_handler},
 310                 {ignore_signals, array_size(ignore_signals), NULL},
 311         };
 312         unsigned int i;
 313
 314         for (i = 0; i < array_size(sigmap); i++) {
 315                 unsigned int j;
 316
 317                 for (j = 0; j < sigmap[i].nsigs; j++) {
 318                         struct sigaction oact;
 319                         if ((sigaction(sigmap[i].sigs[j], NULL, &oact) == 0)
 320                             && (oact.sa_handler == SIG_DFL)) {
 321                                 struct sigaction act;
 322                                 sigfillset(&act.sa_mask);
 323                                 if (sigmap[i].handler == NULL) {
 324                                         act.sa_handler = SIG_IGN;
 325                                         act.sa_flags = 0;
 326                                 } else {
 327                                         /* Request extra arguments to signal
 328                                          * handler. */
 329                                         act.sa_sigaction = sigmap[i].handler;
 330                                         act.sa_flags = SA_SIGINFO;
 331 #ifdef SA_RESETHAND
 332                                         /* don't try to print backtraces
 333                                          * recursively */
 334                                         if (sigmap[i].handler == core_handler)
 335                                                 act.sa_flags |= SA_RESETHAND;
 336 #endif
 337                                 }
 338                                 if (sigaction(sigmap[i].sigs[j], &act, NULL)
 339                                     < 0)
 340                                         flog_err(
 341                                                 EC_LIB_SYSTEM_CALL,
 342                                                 "Unable to set signal handler for signal %d: %s",
 343                                                 sigmap[i].sigs[j],
 344                                                 safe_strerror(errno));
 345                         }
 346                 }
 347         }
 348 }
 349
 350 void signal_init(struct thread_master *m, int sigc,
 351                  struct frr_signal_t signals[])
 352 {
 353
 354         int i = 0;
 355         struct frr_signal_t *sig;
 356
 357         /* First establish some default handlers that can be overridden by
 358            the application. */
 359         trap_default_signals();
 360
 361         while (i < sigc) {
 362                 sig = &signals[i];
 363                 if (signal_set(sig->signal) < 0)
 364                         exit(-1);
 365                 i++;
 366         }
 367
 368         sigmaster.sigc = sigc;
 369         sigmaster.signals = signals;
 370
 371 #ifdef SIGEVENT_SCHEDULE_THREAD
 372         sigmaster.t = NULL;
 373         thread_add_timer(m, frr_signal_timer, &sigmaster,
 374                          FRR_SIGNAL_TIMER_INTERVAL, &sigmaster.t);
 375 #endif /* SIGEVENT_SCHEDULE_THREAD */
 376 }