[PATCH 7/7 v1.1] ARM: Thumb-2: Restore sensible zImage header layout for CONFIG_THUMB2_KERNEL
nicolas.pitre at linaro.org
Wed Nov 17 11:17:01 EST 2010
On Wed, 17 Nov 2010, Dave Martin wrote:
> The code which makes up the zImage header intends to leave a
> 32-byte gap followed by a branch to the real entry point, a
> magic number, and a word containing the absolute entry point
> This gets messed up with with CONFIG_THUMB2_KERNEL, because the
> size of the initial padding NOPs changes.
> Instead, the header can be made fully compatible by restoring
> it to ARM.
> In the Thumb-2 case, we can replace the initial NOPs with a
> sequence which switches to Thumb and jumps to the real entry
> As a consequence, the zImage entry point is now always ARM, so
> no special magic is needed any more for the uImage rules in the
> Thumb-2 case.
> Applies cleanly on v2.6.37-rc2.
> Signed-off-by: Dave Martin <dave.martin at linaro.org>
> Acked-by: Catalin Marinas <catalin.marinas at arm.com>
Acked-by: Nicolas Pitre <nicolas.pitre at linaro.org>
Only a nanonit below that is not that important.
> index 1f65080..ab95391 100644
> --- a/arch/arm/boot/compressed/head.S
> +++ b/arch/arm/boot/compressed/head.S
> @@ -125,16 +125,21 @@ wait: mrc p14, 0, pc, c0, c1, 0
> * sort out different calling conventions
> + THUMB( .arm )
Maybe the THUMB() can be omitted here and .arm be unconditional?
> .type start,#function
> - .rept 8
> + THUMB( adr r12, BSYM(1f) )
> + THUMB( bx r12 )
> + THUMB( .rept 6 )
> + ARM( .rept 8 )
> mov r0, r0
> - b 1f
> + nop @ Pad magic number to 0x24
> .word 0x016f2818 @ Magic numbers to help the loader
> .word start @ absolute load/run zImage address
> .word _edata @ zImage end address
> + THUMB( .thumb )
> 1: mov r7, r1 @ save architecture ID
> mov r8, r2 @ save atags pointer
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