9pfs: assume utimensat() and futimens() are present

The utimensat() and futimens() syscalls have been around for ages (ie,
glibc 2.6 and linux 2.6.22), and the decision was already taken to
switch to utimensat() anyway when fixing CVE-2016-9602 in 2.9.

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Eric Blake <eblake@redhat.com>

fsdev/virtfs-proxy-helper.c

@@ -945,7 +945,8 @@ static int process_requests(int sock)
                                      &spec[0].tv_sec, &spec[0].tv_nsec,
                                      &spec[1].tv_sec, &spec[1].tv_nsec);
             if (retval > 0) {
-                retval = qemu_utimens(path.data, spec);
+                retval = utimensat(AT_FDCWD, path.data, spec,
+                                   AT_SYMLINK_NOFOLLOW);
                 if (retval < 0) {
                     retval = -errno;
                 }

hw/9pfs/9p-handle.c

@@ -378,7 +378,6 @@ static int handle_utimensat(FsContext *ctx, V9fsPath *fs_path,
                             const struct timespec *buf)
 {
     int ret;
-#ifdef CONFIG_UTIMENSAT
     int fd;
     struct handle_data *data = (struct handle_data *)ctx->private;
 
@@ -388,10 +387,6 @@ static int handle_utimensat(FsContext *ctx, V9fsPath *fs_path,
     }
     ret = futimens(fd, buf);
     close(fd);
-#else
-    ret = -1;
-    errno = ENOSYS;
-#endif
     return ret;
 }