[PATCH v2] kwboot: do a filetype check before sending the image

["Uwe Kleine-König" <uwe@kleine-koenig.org>]

The images that can be sent to a Marvell CPU have a fixed format. Do
some sanity checks before actually sending an image for easier diagnosis
of broken files.

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
---
Changes since (implicit) v1, sent with
Message-Id: 1453276010-4669-1-git-send-email-uwe@kleine-koenig.org:

 - whitespace fix
 - error out if a problem is detected
 - add a commit log

 scripts/kwboot.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/scripts/kwboot.c b/scripts/kwboot.c
index 46328d8ed006..06e58f6a7e3b 100644
--- a/scripts/kwboot.c
+++ b/scripts/kwboot.c
@@ -546,6 +546,59 @@ out:
 	return rc;
 }
 
+static int
+kwboot_check_image(unsigned char *img, size_t size)
+{
+	size_t i;
+	size_t header_size, image_size;
+	unsigned char csum = 0;
+
+	switch (img[0x0]) {
+		case 0x5a: /* SPI/NOR */
+		case 0x69: /* UART0 */
+		case 0x78: /* SATA */
+		case 0x8b: /* NAND */
+		case 0x9c: /* PCIe */
+			break;
+		default:
+			printf("Unknown boot source: 0x%hhx\n", img[0x0]);
+			goto err;
+	}
+
+	if (img[0x8] != 1) {
+		printf("Unknown version: 0x%hhx\n", img[0x8]);
+		goto err;
+	}
+
+	image_size = img[0x4] | (img[0x5] << 8) |
+		(img[0x6] << 16) | (img[0x7] << 24);
+
+	header_size = (img[0x9] << 16) | img[0xa] | (img[0xb] << 8);
+
+	if (header_size + image_size != size) {
+		printf("Size mismatch (%zu + %zu != %zu)\n",
+		       header_size, image_size, size);
+		goto err;
+	} else {
+		for (i = 0; i < header_size; ++i)
+			csum += img[i];
+
+		csum -= img[0x1f];
+
+		if (csum != img[0x1f]) {
+			printf("Checksum mismatch: header: 0x%02hhx, calculated: 0x%02hhx\n",
+			       img[0x1f], csum);
+			goto err;
+		}
+	}
+
+	return 0;
+
+err:
+	errno = EINVAL;
+	return 1;
+}
+
 static void *
 kwboot_mmap_image(const char *path, size_t *size, int prot)
 {
@@ -574,6 +627,8 @@ kwboot_mmap_image(const char *path, size_t *size, int prot)
 
 	rc = 0;
 	*size = st.st_size;
+
+	rc = kwboot_check_image(img, *size);
 out:
 	if (rc && img) {
 		munmap(img, st.st_size);
-- 
2.7.0.rc3


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