tools/virtiofsd/fuse_signals.c

   1 /*
   2  * FUSE: Filesystem in Userspace
   3  * Copyright (C) 2001-2007  Miklos Szeredi <miklos@szeredi.hu>
   4  *
   5  * Utility functions for setting signal handlers.
   6  *
   7  * This program can be distributed under the terms of the GNU LGPLv2.
   8  * See the file COPYING.LIB
   9  */
  10
  11 #include "qemu/osdep.h"
  12 #include "fuse_i.h"
  13 #include "fuse_lowlevel.h"
  14
  15
  16 static struct fuse_session *fuse_instance;
  17
  18 static void exit_handler(int sig)
  19 {
  20     if (fuse_instance) {
  21         fuse_session_exit(fuse_instance);
  22         if (sig <= 0) {
  23             fuse_log(FUSE_LOG_ERR, "assertion error: signal value <= 0\n");
  24             abort();
  25         }
  26         fuse_instance->error = sig;
  27     }
  28 }
  29
  30 static void do_nothing(int sig)
  31 {
  32     (void)sig;
  33 }
  34
  35 static int set_one_signal_handler(int sig, void (*handler)(int), int remove)
  36 {
  37     struct sigaction sa;
  38     struct sigaction old_sa;
  39
  40     memset(&sa, 0, sizeof(struct sigaction));
  41     sa.sa_handler = remove ? SIG_DFL : handler;
  42     sigemptyset(&(sa.sa_mask));
  43     sa.sa_flags = 0;
  44
  45     if (sigaction(sig, NULL, &old_sa) == -1) {
  46         fuse_log(FUSE_LOG_ERR, "fuse: cannot get old signal handler: %s\n",
  47                  strerror(errno));
  48         return -1;
  49     }
  50
  51     if (old_sa.sa_handler == (remove ? handler : SIG_DFL) &&
  52         sigaction(sig, &sa, NULL) == -1) {
  53         fuse_log(FUSE_LOG_ERR, "fuse: cannot set signal handler: %s\n",
  54                  strerror(errno));
  55         return -1;
  56     }
  57     return 0;
  58 }
  59
  60 int fuse_set_signal_handlers(struct fuse_session *se)
  61 {
  62     /*
  63      * If we used SIG_IGN instead of the do_nothing function,
  64      * then we would be unable to tell if we set SIG_IGN (and
  65      * thus should reset to SIG_DFL in fuse_remove_signal_handlers)
  66      * or if it was already set to SIG_IGN (and should be left
  67      * untouched.
  68      */
  69     if (set_one_signal_handler(SIGHUP, exit_handler, 0) == -1 ||
  70         set_one_signal_handler(SIGINT, exit_handler, 0) == -1 ||
  71         set_one_signal_handler(SIGTERM, exit_handler, 0) == -1 ||
  72         set_one_signal_handler(SIGPIPE, do_nothing, 0) == -1) {
  73         return -1;
  74     }
  75
  76     fuse_instance = se;
  77     return 0;
  78 }
  79
  80 void fuse_remove_signal_handlers(struct fuse_session *se)
  81 {
  82     if (fuse_instance != se) {
  83         fuse_log(FUSE_LOG_ERR,
  84                  "fuse: fuse_remove_signal_handlers: unknown session\n");
  85     } else {
  86         fuse_instance = NULL;
  87     }
  88
  89     set_one_signal_handler(SIGHUP, exit_handler, 1);
  90     set_one_signal_handler(SIGINT, exit_handler, 1);
  91     set_one_signal_handler(SIGTERM, exit_handler, 1);
  92     set_one_signal_handler(SIGPIPE, do_nothing, 1);
  93 }