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  */
  13
  14 #include "qemu-common.h"
  15 #include "compatfd.h"
  16
  17 #include <sys/syscall.h>
  18 #include <pthread.h>
  19
  20 struct sigfd_compat_info
  21 {
  22     sigset_t mask;
  23     int fd;
  24 };
  25
  26 static void *sigwait_compat(void *opaque)
  27 {
  28     struct sigfd_compat_info *info = opaque;
  29     sigset_t all;
  30
  31     sigfillset(&all);
  32     pthread_sigmask(SIG_BLOCK, &all, NULL);
  33
  34     while (1) {
  35         int sig;
  36         int err;
  37
  38         err = sigwait(&info->mask, &sig);
  39         if (err != 0) {
  40             if (errno == EINTR) {
  41                 continue;
  42             } else {
  43                 return NULL;
  44             }
  45         } else {
  46             struct qemu_signalfd_siginfo buffer;
  47             size_t offset = 0;
  48
  49             memset(&buffer, 0, sizeof(buffer));
  50             buffer.ssi_signo = sig;
  51
  52             while (offset < sizeof(buffer)) {
  53                 ssize_t len;
  54
  55                 len = write(info->fd, (char *)&buffer + offset,
  56                             sizeof(buffer) - offset);
  57                 if (len == -1 && errno == EINTR)
  58                     continue;
  59
  60                 if (len <= 0) {
  61                     return NULL;
  62                 }
  63
  64                 offset += len;
  65             }
  66         }
  67     }
  68 }
  69
  70 static int qemu_signalfd_compat(const sigset_t *mask)
  71 {
  72     pthread_attr_t attr;
  73     pthread_t tid;
  74     struct sigfd_compat_info *info;
  75     int fds[2];
  76
  77     info = malloc(sizeof(*info));
  78     if (info == NULL) {
  79         errno = ENOMEM;
  80         return -1;
  81     }
  82
  83     if (pipe(fds) == -1) {
  84         free(info);
  85         return -1;
  86     }
  87
  88     qemu_set_cloexec(fds[0]);
  89     qemu_set_cloexec(fds[1]);
  90
  91     memcpy(&info->mask, mask, sizeof(*mask));
  92     info->fd = fds[1];
  93
  94     pthread_attr_init(&attr);
  95     pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
  96
  97     pthread_create(&tid, &attr, sigwait_compat, info);
  98
  99     pthread_attr_destroy(&attr);
 100
 101     return fds[0];
 102 }
 103
 104 int qemu_signalfd(const sigset_t *mask)
 105 {
 106 #if defined(CONFIG_SIGNALFD)
 107     int ret;
 108
 109     ret = syscall(SYS_signalfd, -1, mask, _NSIG / 8);
 110     if (ret != -1) {
 111         qemu_set_cloexec(ret);
 112         return ret;
 113     }
 114 #endif
 115
 116     return qemu_signalfd_compat(mask);
 117 }
 118
 119 bool qemu_signalfd_available(void)
 120 {
 121 #ifdef CONFIG_SIGNALFD
 122     errno = 0;
 123     syscall(SYS_signalfd, -1, NULL, _NSIG / 8);
 124     return errno != ENOSYS;
 125 #else
 126     return false;
 127 #endif
 128 }