On Thu, 19 Jun 2014, Kevin Hilman wrote:
> I think this should probably be officialized since we've taken away the
> ability for magic-number checking tools (like 'file') to distinguish
> between big- and little-endian zImages.
>
> For now, I've updated my tools to check for 'setend be' in ARM and
> Thumb2 mode, but if this does get officialized, I'll gladly move over to
> it.
Would you ACK this patch?
----- >8
ARM: zImage: identify kernel endianness
With patch #8067/1 applied, it is no longer possible to determine the
endianness of a compiled kernel image. This normally shouldn't matter
to the boot environment, except for those cases where the selection of
a ramdisk or root filesystem with a matching endianness has to be
automated.
Let's add a flag to the zImage header indicating the actual endianness.
Four bytes from offset 0x30 can be interpreted as follows:
04 03 02 01 big endian kernel
01 02 03 04 little endian kernel
Anything else should be interpreted as "unknown", in which case it is
most likely that patch #8067/1 was not applied either and the zImage
magic number at offset 0x24 could be used instead to determine
endianness. No zImage before this patch ever produced 0x01020304 nor
0x04030201 at offset 0x30 so there is no confusion possible.
Signed-off-by: Nicolas Pitre <[email protected]>
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index c95feab6ce..413fd94b53 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -128,6 +128,7 @@ start:
.word _magic_sig @ Magic numbers to help the loader
.word _magic_start @ absolute load/run zImage address
.word _magic_end @ zImage end address
+ .word 0x04030201 @ endianness flag
THUMB( .thumb )
1:
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