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 SA_SIGINFO
  28 #ifdef HAVE_UCONTEXT_H
  29 #ifdef GNU_LINUX
  30 /* get REG_EIP from ucontext.h */
  31 #ifndef __USE_GNU
  32 #define __USE_GNU
  33 #endif /* __USE_GNU */
  34 #endif /* GNU_LINUX */
  35 #include <ucontext.h>
  36 #endif /* HAVE_UCONTEXT_H */
  37 #endif /* SA_SIGINFO */
  38
  39
  40 /* master signals descriptor struct */
  41 static struct quagga_sigevent_master_t {
  42         struct thread *t;
  43
  44         struct quagga_signal_t *signals;
  45         int sigc;
  46
  47         volatile sig_atomic_t caught;
  48 } sigmaster;
  49
  50 /* Generic signal handler
  51  * Schedules signal event thread
  52  */
  53 static void quagga_signal_handler(int signo)
  54 {
  55         int i;
  56         struct quagga_signal_t *sig;
  57
  58         for (i = 0; i < sigmaster.sigc; i++) {
  59                 sig = &(sigmaster.signals[i]);
  60
  61                 if (sig->signal == signo)
  62                         sig->caught = 1;
  63         }
  64
  65         sigmaster.caught = 1;
  66 }
  67
  68 /* check if signals have been caught and run appropriate handlers */
  69 int quagga_sigevent_process(void)
  70 {
  71         struct quagga_signal_t *sig;
  72         int i;
  73 #ifdef SIGEVENT_BLOCK_SIGNALS
  74         /* shouldnt need to block signals, but potentially may be needed */
  75         sigset_t newmask, oldmask;
  76
  77         /*
  78          * Block most signals, but be careful not to defer SIGTRAP because
  79          * doing so breaks gdb, at least on NetBSD 2.0.  Avoid asking to
  80          * block SIGKILL, just because we shouldn't be able to do so.
  81          */
  82         sigfillset(&newmask);
  83         sigdelset(&newmask, SIGTRAP);
  84         sigdelset(&newmask, SIGKILL);
  85
  86         if ((sigprocmask(SIG_BLOCK, &newmask, &oldmask)) < 0) {
  87                 flog_err_sys(EC_LIB_SYSTEM_CALL,
  88                              "quagga_signal_timer: couldnt block signals!");
  89                 return -1;
  90         }
  91 #endif /* SIGEVENT_BLOCK_SIGNALS */
  92
  93         if (sigmaster.caught > 0) {
  94                 sigmaster.caught = 0;
  95                 /* must not read or set sigmaster.caught after here,
  96                  * race condition with per-sig caught flags if one does
  97                  */
  98
  99                 for (i = 0; i < sigmaster.sigc; i++) {
 100                         sig = &(sigmaster.signals[i]);
 101
 102                         if (sig->caught > 0) {
 103                                 sig->caught = 0;
 104                                 if (sig->handler)
 105                                         sig->handler();
 106                         }
 107                 }
 108         }
 109
 110 #ifdef SIGEVENT_BLOCK_SIGNALS
 111         if (sigprocmask(SIG_UNBLOCK, &oldmask, NULL) < 0)
 112                 ;
 113         return -1;
 114 #endif /* SIGEVENT_BLOCK_SIGNALS */
 115
 116         return 0;
 117 }
 118
 119 #ifdef SIGEVENT_SCHEDULE_THREAD
 120 /* timer thread to check signals. Shouldnt be needed */
 121 int quagga_signal_timer(struct thread *t)
 122 {
 123         struct quagga_sigevent_master_t *sigm;
 124
 125         sigm = THREAD_ARG(t);
 126         sigm->t = NULL;
 127         thread_add_timer(sigm->t->master, quagga_signal_timer, &sigmaster,
 128                          QUAGGA_SIGNAL_TIMER_INTERVAL, &sigm->t);
 129         return quagga_sigevent_process();
 130 }
 131 #endif /* SIGEVENT_SCHEDULE_THREAD */
 132
 133 /* Initialization of signal handles. */
 134 /* Signal wrapper. */
 135 static int signal_set(int signo)
 136 {
 137         int ret;
 138         struct sigaction sig;
 139         struct sigaction osig;
 140
 141         sig.sa_handler = &quagga_signal_handler;
 142         sigfillset(&sig.sa_mask);
 143         sig.sa_flags = 0;
 144         if (signo == SIGALRM) {
 145 #ifdef SA_INTERRUPT
 146                 sig.sa_flags |= SA_INTERRUPT; /* SunOS */
 147 #endif
 148         } else {
 149 #ifdef SA_RESTART
 150                 sig.sa_flags |= SA_RESTART;
 151 #endif /* SA_RESTART */
 152         }
 153
 154         ret = sigaction(signo, &sig, &osig);
 155         if (ret < 0)
 156                 return ret;
 157         else
 158                 return 0;
 159 }
 160
 161 #ifdef SA_SIGINFO
 162
 163 /* XXX This function should be enhanced to support more platforms
 164        (it currently works only on Linux/x86). */
 165 static void *program_counter(void *context)
 166 {
 167 #ifdef HAVE_UCONTEXT_H
 168 #ifdef GNU_LINUX
 169 /* these are from GNU libc, rather than Linux, strictly speaking */
 170 #if defined(REG_EIP)
 171 #  define REG_INDEX REG_EIP
 172 #elif defined(REG_RIP)
 173 #  define REG_INDEX REG_RIP
 174 #elif defined(__powerpc__)
 175 #  define REG_INDEX 32
 176 #endif
 177 #elif defined(SUNOS_5) /* !GNU_LINUX */
 178 # define REG_INDEX REG_PC
 179 #endif                 /* GNU_LINUX */
 180
 181 #ifdef REG_INDEX
 182 #ifdef HAVE_UCONTEXT_T_UC_MCONTEXT_GREGS
 183 #  define REGS gregs[REG_INDEX]
 184 #elif defined(HAVE_UCONTEXT_T_UC_MCONTEXT_UC_REGS)
 185 #  define REGS uc_regs->gregs[REG_INDEX]
 186 #endif /* HAVE_UCONTEXT_T_UC_MCONTEXT_GREGS */
 187 #endif /* REG_INDEX */
 188
 189 #ifdef REGS
 190         if (context)
 191                 return (void *)(((ucontext_t *)context)->uc_mcontext.REGS);
 192 #elif defined(HAVE_UCONTEXT_T_UC_MCONTEXT_REGS__NIP)
 193         /* older Linux / struct pt_regs ? */
 194         if (context)
 195                 return (void *)(((ucontext_t *)context)->uc_mcontext.regs->nip);
 196 #endif /* REGS */
 197
 198 #endif /* HAVE_UCONTEXT_H */
 199         return NULL;
 200 }
 201
 202 #endif /* SA_SIGINFO */
 203
 204 static void __attribute__((noreturn))
 205 exit_handler(int signo
 206 #ifdef SA_SIGINFO
 207              ,
 208              siginfo_t *siginfo, void *context
 209 #endif
 210              )
 211 {
 212 #ifndef SA_SIGINFO
 213         void *siginfo = NULL;
 214         void *pc = NULL;
 215 #else
 216         void *pc = program_counter(context);
 217 #endif
 218
 219         zlog_signal(signo, "exiting...", siginfo, pc);
 220         _exit(128 + signo);
 221 }
 222
 223 static void __attribute__((noreturn))
 224 core_handler(int signo
 225 #ifdef SA_SIGINFO
 226              ,
 227              siginfo_t *siginfo, void *context
 228 #endif
 229              )
 230 {
 231 #ifndef SA_SIGINFO
 232         void *siginfo = NULL;
 233         void *pc = NULL;
 234 #else
 235         void *pc = program_counter(context);
 236 #endif
 237
 238         /* make sure we don't hang in here.  default for SIGALRM is terminate.
 239          * - if we're in backtrace for more than a second, abort. */
 240         struct sigaction sa_default = {.sa_handler = SIG_DFL};
 241         sigaction(SIGALRM, &sa_default, NULL);
 242
 243         sigset_t sigset;
 244         sigemptyset(&sigset);
 245         sigaddset(&sigset, SIGALRM);
 246         sigprocmask(SIG_UNBLOCK, &sigset, NULL);
 247
 248         alarm(1);
 249
 250         zlog_signal(signo, "aborting...", siginfo, pc);
 251
 252         /* dump memory stats on core */
 253         log_memstats(stderr, "core_handler");
 254         abort();
 255 }
 256
 257 static void trap_default_signals(void)
 258 {
 259         static const int core_signals[] = {
 260                 SIGQUIT, SIGILL,
 261 #ifdef SIGEMT
 262                 SIGEMT,
 263 #endif
 264                 SIGFPE,  SIGBUS, SIGSEGV,
 265 #ifdef SIGSYS
 266                 SIGSYS,
 267 #endif
 268 #ifdef SIGXCPU
 269                 SIGXCPU,
 270 #endif
 271 #ifdef SIGXFSZ
 272                 SIGXFSZ,
 273 #endif
 274         };
 275         static const int exit_signals[] = {
 276                 SIGHUP,    SIGINT, SIGALRM, SIGTERM, SIGUSR1, SIGUSR2,
 277 #ifdef SIGPOLL
 278                 SIGPOLL,
 279 #endif
 280 #ifdef SIGVTALRM
 281                 SIGVTALRM,
 282 #endif
 283 #ifdef SIGSTKFLT
 284                 SIGSTKFLT,
 285 #endif
 286         };
 287         static const int ignore_signals[] = {
 288                 SIGPIPE,
 289         };
 290         static const struct {
 291                 const int *sigs;
 292                 unsigned int nsigs;
 293                 void (*handler)(int signo
 294 #ifdef SA_SIGINFO
 295                                 ,
 296                                 siginfo_t *info, void *context
 297 #endif
 298                                 );
 299         } sigmap[] = {
 300                 {core_signals, array_size(core_signals), core_handler},
 301                 {exit_signals, array_size(exit_signals), exit_handler},
 302                 {ignore_signals, array_size(ignore_signals), NULL},
 303         };
 304         unsigned int i;
 305
 306         for (i = 0; i < array_size(sigmap); i++) {
 307                 unsigned int j;
 308
 309                 for (j = 0; j < sigmap[i].nsigs; j++) {
 310                         struct sigaction oact;
 311                         if ((sigaction(sigmap[i].sigs[j], NULL, &oact) == 0)
 312                             && (oact.sa_handler == SIG_DFL)) {
 313                                 struct sigaction act;
 314                                 sigfillset(&act.sa_mask);
 315                                 if (sigmap[i].handler == NULL) {
 316                                         act.sa_handler = SIG_IGN;
 317                                         act.sa_flags = 0;
 318                                 } else {
 319 #ifdef SA_SIGINFO
 320                                         /* Request extra arguments to signal
 321                                          * handler. */
 322                                         act.sa_sigaction = sigmap[i].handler;
 323                                         act.sa_flags = SA_SIGINFO;
 324 #else
 325                                         act.sa_handler = sigmap[i].handler;
 326                                         act.sa_flags = 0;
 327 #endif
 328 #ifdef SA_RESETHAND
 329                                         /* don't try to print backtraces
 330                                          * recursively */
 331                                         if (sigmap[i].handler == core_handler)
 332                                                 act.sa_flags |= SA_RESETHAND;
 333 #endif
 334                                 }
 335                                 if (sigaction(sigmap[i].sigs[j], &act, NULL)
 336                                     < 0)
 337                                         flog_err(
 338                                                 EC_LIB_SYSTEM_CALL,
 339                                                 "Unable to set signal handler for signal %d: %s",
 340                                                 sigmap[i].sigs[j],
 341                                                 safe_strerror(errno));
 342                         }
 343                 }
 344         }
 345 }
 346
 347 void signal_init(struct thread_master *m, int sigc,
 348                  struct quagga_signal_t signals[])
 349 {
 350
 351         int i = 0;
 352         struct quagga_signal_t *sig;
 353
 354         /* First establish some default handlers that can be overridden by
 355            the application. */
 356         trap_default_signals();
 357
 358         while (i < sigc) {
 359                 sig = &signals[i];
 360                 if (signal_set(sig->signal) < 0)
 361                         exit(-1);
 362                 i++;
 363         }
 364
 365         sigmaster.sigc = sigc;
 366         sigmaster.signals = signals;
 367
 368 #ifdef SIGEVENT_SCHEDULE_THREAD
 369         sigmaster.t = NULL;
 370         thread_add_timer(m, quagga_signal_timer, &sigmaster,
 371                          QUAGGA_SIGNAL_TIMER_INTERVAL, &sigmaster.t);
 372 #endif /* SIGEVENT_SCHEDULE_THREAD */
 373 }