[PATCH V2] oslib: qemu_clear_cloexec

[Steve Sistare <steven.sistare@oracle.com>]

Define qemu_clear_cloexec, analogous to qemu_set_cloexec.  This will be
used to preserve selected descriptors during cpr.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 include/qemu/osdep.h | 9 +++++++++
 util/oslib-posix.c   | 9 +++++++++
 util/oslib-win32.c   | 4 ++++
 3 files changed, 22 insertions(+)

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 88c9fac..9c8c536 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -618,6 +618,15 @@ ssize_t qemu_write_full(int fd, const void *buf, size_t count)
 
 void qemu_set_cloexec(int fd);
 
+/*
+ * Clear FD_CLOEXEC for a descriptor.
+ *
+ * The caller must guarantee that no other fork+exec's occur before the
+ * exec that is intended to inherit this descriptor, eg by suspending CPUs
+ * and blocking monitor commands.
+ */
+void qemu_clear_cloexec(int fd);
+
 /* Return a dynamically allocated directory path that is appropriate for storing
  * local state.
  *
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 59a891b..a8cc3d0 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -273,6 +273,15 @@ int qemu_socketpair(int domain, int type, int protocol, int sv[2])
     return ret;
 }
 
+void qemu_clear_cloexec(int fd)
+{
+    int f;
+    f = fcntl(fd, F_GETFD);
+    assert(f != -1);
+    f = fcntl(fd, F_SETFD, f & ~FD_CLOEXEC);
+    assert(f != -1);
+}
+
 char *
 qemu_get_local_state_dir(void)
 {
diff --git a/util/oslib-win32.c b/util/oslib-win32.c
index 07ade41..756bee3 100644
--- a/util/oslib-win32.c
+++ b/util/oslib-win32.c
@@ -222,6 +222,10 @@ void qemu_set_cloexec(int fd)
 {
 }
 
+void qemu_clear_cloexec(int fd)
+{
+}
+
 int qemu_get_thread_id(void)
 {
     return GetCurrentThreadId();
-- 
1.8.3.1