lib/sigevent.c

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