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-common.h"
  18 #include "qemu/compatfd.h"
  19 #include "qemu/thread.h"
  20
  21 #include <sys/syscall.h>
  22
  23 struct sigfd_compat_info
  24 {
  25     sigset_t mask;
  26     int fd;
  27 };
  28
  29 static void *sigwait_compat(void *opaque)
  30 {
  31     struct sigfd_compat_info *info = opaque;
  32
  33     while (1) {
  34         int sig;
  35         int err;
  36
  37         err = sigwait(&info->mask, &sig);
  38         if (err != 0) {
  39             if (errno == EINTR) {
  40                 continue;
  41             } else {
  42                 return NULL;
  43             }
  44         } else {
  45             struct qemu_signalfd_siginfo buffer;
  46             size_t offset = 0;
  47
  48             memset(&buffer, 0, sizeof(buffer));
  49             buffer.ssi_signo = sig;
  50
  51             while (offset < sizeof(buffer)) {
  52                 ssize_t len;
  53
  54                 len = write(info->fd, (char *)&buffer + offset,
  55                             sizeof(buffer) - offset);
  56                 if (len == -1 && errno == EINTR)
  57                     continue;
  58
  59                 if (len <= 0) {
  60                     return NULL;
  61                 }
  62
  63                 offset += len;
  64             }
  65         }
  66     }
  67 }
  68
  69 static int qemu_signalfd_compat(const sigset_t *mask)
  70 {
  71     struct sigfd_compat_info *info;
  72     QemuThread thread;
  73     int fds[2];
  74
  75     info = malloc(sizeof(*info));
  76     if (info == NULL) {
  77         errno = ENOMEM;
  78         return -1;
  79     }
  80
  81     if (pipe(fds) == -1) {
  82         free(info);
  83         return -1;
  84     }
  85
  86     qemu_set_cloexec(fds[0]);
  87     qemu_set_cloexec(fds[1]);
  88
  89     memcpy(&info->mask, mask, sizeof(*mask));
  90     info->fd = fds[1];
  91
  92     qemu_thread_create(&thread, "signalfd_compat", sigwait_compat, info,
  93                        QEMU_THREAD_DETACHED);
  94
  95     return fds[0];
  96 }
  97
  98 int qemu_signalfd(const sigset_t *mask)
  99 {
 100 #if defined(CONFIG_SIGNALFD)
 101     int ret;
 102
 103     ret = syscall(SYS_signalfd, -1, mask, _NSIG / 8);
 104     if (ret != -1) {
 105         qemu_set_cloexec(ret);
 106         return ret;
 107     }
 108 #endif
 109
 110     return qemu_signalfd_compat(mask);
 111 }