memcpy overlap warn

diff --git a/lib/string.c b/lib/string.c
index 546d59711a12..5fa442145935 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -883,6 +883,9 @@ void *memcpy(void *dest, const void *src, size_t count)
    char *tmp = dest;
    const char *s = src;

+   if (WARN(dest > src && dest - src < count, "Unsafe memcpy!!!"))
+       return memmove(dest, src, count);
+
    while (count--)
        *tmp++ = *s++;
    return dest;