fel: Check for the U-Boot header CRC

A U-Boot image has two CRCs, one to cover the data and that we already
check, and one to cover the header.

Since we're not checking the latter, let's make sure it's the case.
Tested-by: Frank Kunz <mailinglists@kunz-im-inter.net>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

fel.c

@@ -764,6 +764,15 @@ void aw_fel_write_uboot_image(feldev_handle *dev, uint8_t *buf, size_t len)
 
 	image_header_t hdr = *(image_header_t *)buf;
 
+	uint32_t hcrc = be32toh(hdr.ih_hcrc);
+
+	/* The CRC is calculated on the whole header but the CRC itself */
+	hdr.ih_hcrc = 0;
+	uint32_t computed_hcrc = crc32(0, (const uint8_t *) &hdr, HEADER_SIZE);
+	if (hcrc != computed_hcrc)
+		pr_fatal("U-Boot header CRC mismatch: expected %x, got %x\n",
+			 hcrc, computed_hcrc);
+
 	/* Check for a valid mkimage header */
 	int image_type = get_image_type(buf, len);
 	if (image_type <= IH_TYPE_INVALID) {