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/osdep.h"
  17 #include "qemu/thread.h"
  18
  19 #include <sys/syscall.h>
  20
  21 struct sigfd_compat_info
  22 {
  23     sigset_t mask;
  24     int fd;
  25 };
  26
  27 static void *sigwait_compat(void *opaque)
  28 {
  29     struct sigfd_compat_info *info = opaque;
  30
  31     while (1) {
  32         int sig;
  33         int err;
  34
  35         err = sigwait(&info->mask, &sig);
  36         if (err != 0) {
  37             if (errno == EINTR) {
  38                 continue;
  39             } else {
  40                 return NULL;
  41             }
  42         } else {
  43             struct qemu_signalfd_siginfo buffer;
  44             size_t offset = 0;
  45
  46             memset(&buffer, 0, sizeof(buffer));
  47             buffer.ssi_signo = sig;
  48
  49             while (offset < sizeof(buffer)) {
  50                 ssize_t len;
  51
  52                 len = write(info->fd, (char *)&buffer + offset,
  53                             sizeof(buffer) - offset);
  54                 if (len == -1 && errno == EINTR)
  55                     continue;
  56
  57                 if (len <= 0) {
  58                     return NULL;
  59                 }
  60
  61                 offset += len;
  62             }
  63         }
  64     }
  65 }
  66
  67 static int qemu_signalfd_compat(const sigset_t *mask)
  68 {
  69     struct sigfd_compat_info *info;
  70     QemuThread thread;
  71     int fds[2];
  72
  73     info = malloc(sizeof(*info));
  74     if (info == NULL) {
  75         errno = ENOMEM;
  76         return -1;
  77     }
  78
  79     if (pipe(fds) == -1) {
  80         free(info);
  81         return -1;
  82     }
  83
  84     qemu_set_cloexec(fds[0]);
  85     qemu_set_cloexec(fds[1]);
  86
  87     memcpy(&info->mask, mask, sizeof(*mask));
  88     info->fd = fds[1];
  89
  90     qemu_thread_create(&thread, "signalfd_compat", sigwait_compat, info,
  91                        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 }