Merge remote-tracking branch 'remotes/mst/tags/for_upstream' into staging
[qemu.git] / 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 }