[OpenWrt-Devel] [PATCH 1/2] kernel: mtdsplit: wrgg: Support big and little endian

Linus Walleij linus.walleij at linaro.org
Mon Mar 11 14:16:42 EDT 2019

The WRGG images exist in both big and little endian variants,
as can be seen from the image generator in
tools/firmware-utils/src/mkwrggimg.c, you either pass
the "-b" flag or not. The D-Link DIR-685 is using little
endian images so we need to support splitting these.

Detect endianness like this: if the kernel entity size
gets silly big (bigger than the flash memory) we are
probably using the wrong endianness.

Example: my kernel of 0x0067ff64 was switched around by
wrong endianness and detected as 0x64ff67a0 (the actual
size in swapped endianness + header 0xa0).

Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
 .../generic/files/drivers/mtd/mtdsplit/mtdsplit_wrgg.c      | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/target/linux/generic/files/drivers/mtd/mtdsplit/mtdsplit_wrgg.c b/target/linux/generic/files/drivers/mtd/mtdsplit/mtdsplit_wrgg.c
index 5ce7625731d6..dd98bee04f7b 100644
--- a/target/linux/generic/files/drivers/mtd/mtdsplit/mtdsplit_wrgg.c
+++ b/target/linux/generic/files/drivers/mtd/mtdsplit/mtdsplit_wrgg.c
@@ -72,6 +72,12 @@ static int mtdsplit_parse_wrgg(struct mtd_info *master,
 	/* sanity checks */
 	if (le32_to_cpu(hdr.magic1) == WRGG03_MAGIC) {
 		kernel_ent_size = hdr_len + be32_to_cpu(hdr.size);
+		/*
+		 * If this becomes silly big is is probably because the
+		 * WRGG image is little-endian.
+		 */
+		if (kernel_ent_size > master->size)
+			kernel_ent_size = hdr_len + le32_to_cpu(hdr.size);
 	} else if (le32_to_cpu(hdr.magic1) == WRG_MAGIC) {
 		kernel_ent_size = sizeof(struct wrg_header) + le32_to_cpu(
 		                  ((struct wrg_header*)&hdr)->size);

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