From mboxrd@z Thu Jan 1 00:00:00 1970 From: dave.martin@linaro.org (Dave Martin) Date: Tue, 16 Nov 2010 13:14:37 +0000 Subject: [PATCH 7/7] ARM: Thumb-2: Restore sensible zImage header layout for CONFIG_THUMB2_KERNEL In-Reply-To: <1289913277-8822-1-git-send-email-dave.martin@linaro.org> References: <1289913277-8822-1-git-send-email-dave.martin@linaro.org> Message-ID: <1289913277-8822-7-git-send-email-dave.martin@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org The code which makes up the zImage header clearly intends to leave a vector-table-sized gap of 8 words (NOPs, in fact), followed by a branch to the real entry point, a magic number, and a word containing the absolute entry point address. This gets messed up with with CONFIG_THUMB2_KERNEL: * The NOPs making up the vector table become halfword- sized. * The magic number and absolute entry point occur too early and become misaligned. * The absolute entry point fails to indicate that the entry point is Thumb code, which will cause incorrect execution if the bootloader uses this to enter the kernel. This patch makes sure the same layout is generated in the CONFIG_THUMB2_KERNEL case as in the traditional ARM case, and sets the Thumb bit (bit 0) in the entry point field. The ARM case is unaffected. This is my best guess as to how the zImage should be laid out for Thumb-2. U-Boot in particular uses its own metadata and ignores the zImage header fields. If someone knows of a bootloader or other utility which relies on the strange existing Thumb-2 zImage header layout then this may require more careful thought. Applies cleanly on v2.6.37-rc1. Signed-off-by: Dave Martin Acked-by: Catalin Marinas Reviewed-by: Will Deacon --- arch/arm/boot/compressed/head.S | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S index 1f65080..1e36e2a 100644 --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -128,12 +128,12 @@ wait: mrc p14, 0, pc, c0, c1, 0 start: .type start,#function .rept 8 - mov r0, r0 + W(nop) @ use 32-bit NOPs for correct padding .endr - b 1f + W(b) 1f .word 0x016f2818 @ Magic numbers to help the loader - .word start @ absolute load/run zImage address + .word BSYM(start) @ absolute load/run zImage address .word _edata @ zImage end address 1: mov r7, r1 @ save architecture ID mov r8, r2 @ save atags pointer -- 1.7.1