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 "config.h"
  12 #include "fuse_i.h"
  13 #include "fuse_lowlevel.h"
  14
  15 #include <signal.h>
  16 #include <stdio.h>
  17 #include <stdlib.h>
  18 #include <string.h>
  19
  20 static struct fuse_session *fuse_instance;
  21
  22 static void exit_handler(int sig)
  23 {
  24     if (fuse_instance) {
  25         fuse_session_exit(fuse_instance);
  26         if (sig <= 0) {
  27             fuse_log(FUSE_LOG_ERR, "assertion error: signal value <= 0\n");
  28             abort();
  29         }
  30         fuse_instance->error = sig;
  31     }
  32 }
  33
  34 static void do_nothing(int sig)
  35 {
  36     (void)sig;
  37 }
  38
  39 static int set_one_signal_handler(int sig, void (*handler)(int), int remove)
  40 {
  41     struct sigaction sa;
  42     struct sigaction old_sa;
  43
  44     memset(&sa, 0, sizeof(struct sigaction));
  45     sa.sa_handler = remove ? SIG_DFL : handler;
  46     sigemptyset(&(sa.sa_mask));
  47     sa.sa_flags = 0;
  48
  49     if (sigaction(sig, NULL, &old_sa) == -1) {
  50         perror("fuse: cannot get old signal handler");
  51         return -1;
  52     }
  53
  54     if (old_sa.sa_handler == (remove ? handler : SIG_DFL) &&
  55         sigaction(sig, &sa, NULL) == -1) {
  56         perror("fuse: cannot set signal handler");
  57         return -1;
  58     }
  59     return 0;
  60 }
  61
  62 int fuse_set_signal_handlers(struct fuse_session *se)
  63 {
  64     /*
  65      * If we used SIG_IGN instead of the do_nothing function,
  66      * then we would be unable to tell if we set SIG_IGN (and
  67      * thus should reset to SIG_DFL in fuse_remove_signal_handlers)
  68      * or if it was already set to SIG_IGN (and should be left
  69      * untouched.
  70      */
  71     if (set_one_signal_handler(SIGHUP, exit_handler, 0) == -1 ||
  72         set_one_signal_handler(SIGINT, exit_handler, 0) == -1 ||
  73         set_one_signal_handler(SIGTERM, exit_handler, 0) == -1 ||
  74         set_one_signal_handler(SIGPIPE, do_nothing, 0) == -1) {
  75         return -1;
  76     }
  77
  78     fuse_instance = se;
  79     return 0;
  80 }
  81
  82 void fuse_remove_signal_handlers(struct fuse_session *se)
  83 {
  84     if (fuse_instance != se) {
  85         fuse_log(FUSE_LOG_ERR,
  86                  "fuse: fuse_remove_signal_handlers: unknown session\n");
  87     } else {
  88         fuse_instance = NULL;
  89     }
  90
  91     set_one_signal_handler(SIGHUP, exit_handler, 1);
  92     set_one_signal_handler(SIGINT, exit_handler, 1);
  93     set_one_signal_handler(SIGTERM, exit_handler, 1);
  94     set_one_signal_handler(SIGPIPE, do_nothing, 1);
  95 }