linux-user: Implement membarrier syscall

Signed-off-by: Andreas Schwab <schwab@suse.de>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <mvmpnomohfm.fsf@suse.de>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index c930577..7aaa9d9 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -334,6 +334,9 @@
 _syscall5(int, sys_statx, int, dirfd, const char *, pathname, int, flags,
           unsigned int, mask, struct target_statx *, statxbuf)
 #endif
+#if defined(TARGET_NR_membarrier) && defined(__NR_membarrier)
+_syscall2(int, membarrier, int, cmd, int, flags)
+#endif
 
 static bitmask_transtbl fcntl_flags_tbl[] = {
   { TARGET_O_ACCMODE,   TARGET_O_WRONLY,    O_ACCMODE,   O_WRONLY,    },
@@ -12090,6 +12093,10 @@
         unlock_user(p, arg1, 0);
         return ret;
 #endif
+#if defined TARGET_NR_membarrier && defined __NR_membarrier
+    case TARGET_NR_membarrier:
+        return get_errno(membarrier(arg1, arg2));
+#endif
 
     default:
         qemu_log_mask(LOG_UNIMP, "Unsupported syscall: %d\n", num);