Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 106 insertions, 0 deletions

diff --git a/util/compatfd.c b/util/compatfd.c
new file mode 100644
index 000000000..ab810c42a
--- /dev/null
+++ b/util/compatfd.c
@@ -0,0 +1,106 @@
+/*
+ * signalfd/eventfd compatibility
+ *
+ * Copyright IBM, Corp. 2008
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ * Contributions after 2012-01-13 are licensed under the terms of the
+ * GNU GPL, version 2 or (at your option) any later version.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/thread.h"
+
+#if defined(CONFIG_SIGNALFD)
+#include <sys/signalfd.h>
+#endif
+
+struct sigfd_compat_info {
+    sigset_t mask;
+    int fd;
+};
+
+static void *sigwait_compat(void *opaque)
+{
+    struct sigfd_compat_info *info = opaque;
+
+    while (1) {
+        int sig;
+        int err;
+
+        err = sigwait(&info->mask, &sig);
+        if (err != 0) {
+            if (errno == EINTR) {
+                continue;
+            } else {
+                return NULL;
+            }
+        } else {
+            struct qemu_signalfd_siginfo buffer;
+            size_t offset = 0;
+
+            memset(&buffer, 0, sizeof(buffer));
+            buffer.ssi_signo = sig;
+
+            while (offset < sizeof(buffer)) {
+                ssize_t len;
+
+                len = write(info->fd, (char *)&buffer + offset,
+                            sizeof(buffer) - offset);
+                if (len == -1 && errno == EINTR) {
+                    continue;
+                }
+
+                if (len <= 0) {
+                    return NULL;
+                }
+
+                offset += len;
+            }
+        }
+    }
+}
+
+static int qemu_signalfd_compat(const sigset_t *mask)
+{
+    struct sigfd_compat_info *info;
+    QemuThread thread;
+    int fds[2];
+
+    info = g_malloc(sizeof(*info));
+
+    if (pipe(fds) == -1) {
+        g_free(info);
+        return -1;
+    }
+
+    qemu_set_cloexec(fds[0]);
+    qemu_set_cloexec(fds[1]);
+
+    memcpy(&info->mask, mask, sizeof(*mask));
+    info->fd = fds[1];
+
+    qemu_thread_create(&thread, "signalfd_compat", sigwait_compat, info,
+                       QEMU_THREAD_DETACHED);
+
+    return fds[0];
+}
+
+int qemu_signalfd(const sigset_t *mask)
+{
+#if defined(CONFIG_SIGNALFD)
+    int ret;
+
+    ret = signalfd(-1, mask, SFD_CLOEXEC);
+    if (ret != -1) {
+        return ret;
+    }
+#endif
+
+    return qemu_signalfd_compat(mask);
+}