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