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 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         zlog_signal(signo, "exiting..."
 213 #ifdef SA_SIGINFO
 214                     ,
 215                     siginfo, program_counter(context)
 216 #endif
 217                             );
 218         _exit(128 + signo);
 219 }
 220
 221 static void __attribute__((noreturn))
 222 core_handler(int signo
 223 #ifdef SA_SIGINFO
 224              ,
 225              siginfo_t *siginfo, void *context
 226 #endif
 227              )
 228 {
 229         /* make sure we don't hang in here.  default for SIGALRM is terminate.
 230          * - if we're in backtrace for more than a second, abort. */
 231         struct sigaction sa_default = {.sa_handler = SIG_DFL};
 232         sigaction(SIGALRM, &sa_default, NULL);
 233
 234         sigset_t sigset;
 235         sigemptyset(&sigset);
 236         sigaddset(&sigset, SIGALRM);
 237         sigprocmask(SIG_UNBLOCK, &sigset, NULL);
 238
 239         alarm(1);
 240
 241         zlog_signal(signo, "aborting..."
 242 #ifdef SA_SIGINFO
 243                     ,
 244                     siginfo, program_counter(context)
 245 #endif
 246                             );
 247         /* dump memory stats on core */
 248         log_memstats(stderr, "core_handler");
 249         abort();
 250 }
 251
 252 static void trap_default_signals(void)
 253 {
 254         static const int core_signals[] = {
 255                 SIGQUIT, SIGILL,
 256 #ifdef SIGEMT
 257                 SIGEMT,
 258 #endif
 259                 SIGFPE,  SIGBUS, SIGSEGV,
 260 #ifdef SIGSYS
 261                 SIGSYS,
 262 #endif
 263 #ifdef SIGXCPU
 264                 SIGXCPU,
 265 #endif
 266 #ifdef SIGXFSZ
 267                 SIGXFSZ,
 268 #endif
 269         };
 270         static const int exit_signals[] = {
 271                 SIGHUP,    SIGINT, SIGALRM, SIGTERM, SIGUSR1, SIGUSR2,
 272 #ifdef SIGPOLL
 273                 SIGPOLL,
 274 #endif
 275 #ifdef SIGVTALRM
 276                 SIGVTALRM,
 277 #endif
 278 #ifdef SIGSTKFLT
 279                 SIGSTKFLT,
 280 #endif
 281         };
 282         static const int ignore_signals[] = {
 283                 SIGPIPE,
 284         };
 285         static const struct {
 286                 const int *sigs;
 287                 unsigned int nsigs;
 288                 void (*handler)(int signo
 289 #ifdef SA_SIGINFO
 290                                 ,
 291                                 siginfo_t *info, void *context
 292 #endif
 293                                 );
 294         } sigmap[] = {
 295                 {core_signals, array_size(core_signals), core_handler},
 296                 {exit_signals, array_size(exit_signals), exit_handler},
 297                 {ignore_signals, array_size(ignore_signals), NULL},
 298         };
 299         unsigned int i;
 300
 301         for (i = 0; i < array_size(sigmap); i++) {
 302                 unsigned int j;
 303
 304                 for (j = 0; j < sigmap[i].nsigs; j++) {
 305                         struct sigaction oact;
 306                         if ((sigaction(sigmap[i].sigs[j], NULL, &oact) == 0)
 307                             && (oact.sa_handler == SIG_DFL)) {
 308                                 struct sigaction act;
 309                                 sigfillset(&act.sa_mask);
 310                                 if (sigmap[i].handler == NULL) {
 311                                         act.sa_handler = SIG_IGN;
 312                                         act.sa_flags = 0;
 313                                 } else {
 314 #ifdef SA_SIGINFO
 315                                         /* Request extra arguments to signal
 316                                          * handler. */
 317                                         act.sa_sigaction = sigmap[i].handler;
 318                                         act.sa_flags = SA_SIGINFO;
 319 #else
 320                                         act.sa_handler = sigmap[i].handler;
 321                                         act.sa_flags = 0;
 322 #endif
 323 #ifdef SA_RESETHAND
 324                                         /* don't try to print backtraces
 325                                          * recursively */
 326                                         if (sigmap[i].handler == core_handler)
 327                                                 act.sa_flags |= SA_RESETHAND;
 328 #endif
 329                                 }
 330                                 if (sigaction(sigmap[i].sigs[j], &act, NULL)
 331                                     < 0)
 332                                         flog_err(
 333                                                 EC_LIB_SYSTEM_CALL,
 334                                                 "Unable to set signal handler for signal %d: %s",
 335                                                 sigmap[i].sigs[j],
 336                                                 safe_strerror(errno));
 337                         }
 338                 }
 339         }
 340 }
 341
 342 void signal_init(struct thread_master *m, int sigc,
 343                  struct quagga_signal_t signals[])
 344 {
 345
 346         int i = 0;
 347         struct quagga_signal_t *sig;
 348
 349         /* First establish some default handlers that can be overridden by
 350            the application. */
 351         trap_default_signals();
 352
 353         while (i < sigc) {
 354                 sig = &signals[i];
 355                 if (signal_set(sig->signal) < 0)
 356                         exit(-1);
 357                 i++;
 358         }
 359
 360         sigmaster.sigc = sigc;
 361         sigmaster.signals = signals;
 362
 363 #ifdef SIGEVENT_SCHEDULE_THREAD
 364         sigmaster.t = NULL;
 365         thread_add_timer(m, quagga_signal_timer, &sigmaster,
 366                          QUAGGA_SIGNAL_TIMER_INTERVAL, &sigmaster.t);
 367 #endif /* SIGEVENT_SCHEDULE_THREAD */
 368 }