xref: /openbmc/qemu/util/compatfd.c (revision d0e31a10)
1 /*
2  * signalfd/eventfd compatibility
3  *
4  * Copyright IBM, Corp. 2008
5  *
6  * Authors:
7  *  Anthony Liguori   <aliguori@us.ibm.com>
8  *
9  * This work is licensed under the terms of the GNU GPL, version 2.  See
10  * the COPYING file in the top-level directory.
11  *
12  * Contributions after 2012-01-13 are licensed under the terms of the
13  * GNU GPL, version 2 or (at your option) any later version.
14  */
15 
16 #include "qemu/osdep.h"
17 #include "qemu-common.h"
18 #include "qemu/thread.h"
19 
20 #include <sys/syscall.h>
21 
22 struct sigfd_compat_info
23 {
24     sigset_t mask;
25     int fd;
26 };
27 
28 static void *sigwait_compat(void *opaque)
29 {
30     struct sigfd_compat_info *info = opaque;
31 
32     while (1) {
33         int sig;
34         int err;
35 
36         err = sigwait(&info->mask, &sig);
37         if (err != 0) {
38             if (errno == EINTR) {
39                 continue;
40             } else {
41                 return NULL;
42             }
43         } else {
44             struct qemu_signalfd_siginfo buffer;
45             size_t offset = 0;
46 
47             memset(&buffer, 0, sizeof(buffer));
48             buffer.ssi_signo = sig;
49 
50             while (offset < sizeof(buffer)) {
51                 ssize_t len;
52 
53                 len = write(info->fd, (char *)&buffer + offset,
54                             sizeof(buffer) - offset);
55                 if (len == -1 && errno == EINTR)
56                     continue;
57 
58                 if (len <= 0) {
59                     return NULL;
60                 }
61 
62                 offset += len;
63             }
64         }
65     }
66 }
67 
68 static int qemu_signalfd_compat(const sigset_t *mask)
69 {
70     struct sigfd_compat_info *info;
71     QemuThread thread;
72     int fds[2];
73 
74     info = malloc(sizeof(*info));
75     if (info == NULL) {
76         errno = ENOMEM;
77         return -1;
78     }
79 
80     if (pipe(fds) == -1) {
81         free(info);
82         return -1;
83     }
84 
85     qemu_set_cloexec(fds[0]);
86     qemu_set_cloexec(fds[1]);
87 
88     memcpy(&info->mask, mask, sizeof(*mask));
89     info->fd = fds[1];
90 
91     qemu_thread_create(&thread, "signalfd_compat", sigwait_compat, info,
92                        QEMU_THREAD_DETACHED);
93 
94     return fds[0];
95 }
96 
97 int qemu_signalfd(const sigset_t *mask)
98 {
99 #if defined(CONFIG_SIGNALFD)
100     int ret;
101 
102     ret = syscall(SYS_signalfd, -1, mask, _NSIG / 8);
103     if (ret != -1) {
104         qemu_set_cloexec(ret);
105         return ret;
106     }
107 #endif
108 
109     return qemu_signalfd_compat(mask);
110 }
111