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
  19 #include <sys/syscall.h>
  20 #include <pthread.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     sigset_t all;
  32
  33     sigfillset(&all);
  34     pthread_sigmask(SIG_BLOCK, &all, NULL);
  35
  36     while (1) {
  37         int sig;
  38         int err;
  39
  40         err = sigwait(&info->mask, &sig);
  41         if (err != 0) {
  42             if (errno == EINTR) {
  43                 continue;
  44             } else {
  45                 return NULL;
  46             }
  47         } else {
  48             struct qemu_signalfd_siginfo buffer;
  49             size_t offset = 0;
  50
  51             memset(&buffer, 0, sizeof(buffer));
  52             buffer.ssi_signo = sig;
  53
  54             while (offset < sizeof(buffer)) {
  55                 ssize_t len;
  56
  57                 len = write(info->fd, (char *)&buffer + offset,
  58                             sizeof(buffer) - offset);
  59                 if (len == -1 && errno == EINTR)
  60                     continue;
  61
  62                 if (len <= 0) {
  63                     return NULL;
  64                 }
  65
  66                 offset += len;
  67             }
  68         }
  69     }
  70 }
  71
  72 static int qemu_signalfd_compat(const sigset_t *mask)
  73 {
  74     pthread_attr_t attr;
  75     pthread_t tid;
  76     struct sigfd_compat_info *info;
  77     int fds[2];
  78
  79     info = malloc(sizeof(*info));
  80     if (info == NULL) {
  81         errno = ENOMEM;
  82         return -1;
  83     }
  84
  85     if (pipe(fds) == -1) {
  86         free(info);
  87         return -1;
  88     }
  89
  90     qemu_set_cloexec(fds[0]);
  91     qemu_set_cloexec(fds[1]);
  92
  93     memcpy(&info->mask, mask, sizeof(*mask));
  94     info->fd = fds[1];
  95
  96     pthread_attr_init(&attr);
  97     pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
  98
  99     pthread_create(&tid, &attr, sigwait_compat, info);
 100
 101     pthread_attr_destroy(&attr);
 102
 103     return fds[0];
 104 }
 105
 106 int qemu_signalfd(const sigset_t *mask)
 107 {
 108 #if defined(CONFIG_SIGNALFD)
 109     int ret;
 110
 111     ret = syscall(SYS_signalfd, -1, mask, _NSIG / 8);
 112     if (ret != -1) {
 113         qemu_set_cloexec(ret);
 114         return ret;
 115     }
 116 #endif
 117
 118     return qemu_signalfd_compat(mask);
 119 }
 120
 121 bool qemu_signalfd_available(void)
 122 {
 123 #ifdef CONFIG_SIGNALFD
 124     sigset_t mask;
 125     int fd;
 126     bool ok;
 127     sigemptyset(&mask);
 128     errno = 0;
 129     fd = syscall(SYS_signalfd, -1, &mask, _NSIG / 8);
 130     ok = (errno != ENOSYS);
 131     if (fd >= 0) {
 132         close(fd);
 133     }
 134     return ok;
 135 #else
 136     return false;
 137 #endif
 138 }