oslib: qemu_clear_cloexec

Define qemu_clear_cloexec, analogous to qemu_set_cloexec.

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>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/1759332851-370353-4-git-send-email-steven.sistare@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>

include/qemu/osdep.h

@@ -689,6 +689,15 @@ ssize_t qemu_write_full(int fd, const void *buf, size_t count)
 void qemu_set_cloexec(int fd);
 bool qemu_set_blocking(int fd, bool block, Error **errp);
 
+/*
+ * 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.
  *

util/oslib-posix.c

@@ -305,6 +305,15 @@ 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)
 {

util/oslib-win32.c

@@ -219,6 +219,10 @@ void qemu_set_cloexec(int fd)
 {
 }
 
+void qemu_clear_cloexec(int fd)
+{
+}
+
 int qemu_get_thread_id(void)
 {
     return GetCurrentThreadId();