util/compatfd.c

   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-common.h"
  17 #include "qemu/compatfd.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, sigwait_compat, info, QEMU_THREAD_DETACHED);
  92
  93     return fds[0];
  94 }
  95
  96 int qemu_signalfd(const sigset_t *mask)
  97 {
  98 #if defined(CONFIG_SIGNALFD)
  99     int ret;
 100
 101     ret = syscall(SYS_signalfd, -1, mask, _NSIG / 8);
 102     if (ret != -1) {
 103         qemu_set_cloexec(ret);
 104         return ret;
 105     }
 106 #endif
 107
 108     return qemu_signalfd_compat(mask);
 109 }
 110
 111 bool qemu_signalfd_available(void)
 112 {
 113 #ifdef CONFIG_SIGNALFD
 114     sigset_t mask;
 115     int fd;
 116     bool ok;
 117     sigemptyset(&mask);
 118     errno = 0;
 119     fd = syscall(SYS_signalfd, -1, &mask, _NSIG / 8);
 120     ok = (errno != ENOSYS);
 121     if (fd >= 0) {
 122         close(fd);
 123     }
 124     return ok;
 125 #else
 126     return false;
 127 #endif
 128 }