pstore/ram: Use memcpy_toio instead of memcpy

BugLink: http://bugs.launchpad.net/bugs/1637510

commit 7e75678d upstream.

persistent_ram_update uses vmap / iomap based on whether the buffer is in
memory region or reserved region. However, both map it as non-cacheable
memory. For armv8 specifically, non-cacheable mapping requests use a
memory type that has to be accessed aligned to the request size. memcpy()
doesn't guarantee that.
Signed-off-by: Furquan Shaikh <furquan@google.com>
Signed-off-by: Enric Balletbo Serra <enric.balletbo@collabora.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Olof Johansson <olofj@chromium.org>
Tested-by: Furquan Shaikh <furquan@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

fs/pstore/ram_core.c

@@ -263,7 +263,7 @@ static void notrace persistent_ram_update(struct persistent_ram_zone *prz,
 	const void *s, unsigned int start, unsigned int count)
 {
 	struct persistent_ram_buffer *buffer = prz->buffer;
-	memcpy(buffer->data + start, s, count);
+	memcpy_toio(buffer->data + start, s, count);
 	persistent_ram_update_ecc(prz, start, count);
 }