Commit 26e5ca93 authored Nov 29, 2010 by Dave Martin Committed by Russell King Nov 30, 2010

ARM: 6503/1: Thumb-2: Restore sensible zImage header layout for CONFIG_THUMB2_KERNEL



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 address.

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 point.

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.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

parent bfa64c4a

arch/arm/boot/Makefile

+0 −5

Original line number	Diff line number	Diff line
		@@ -70,12 +70,7 @@ else
		$(obj)/uImage: LOADADDR=$(ZRELADDR)
		endif

		ifeq ($(CONFIG_THUMB2_KERNEL),y)
		# Set bit 0 to 1 so that "mov pc, rx" switches to Thumb-2 mode
		$(obj)/uImage: STARTADDR=$(shell echo $(LOADADDR) \| sed -e "s/.$$/1/")
		else
		$(obj)/uImage: STARTADDR=$(LOADADDR)
		endif

		$(obj)/uImage: $(obj)/zImage FORCE
		$(call if_changed,uimage)

arch/arm/boot/compressed/head.S

+6 −1

Original line number	Diff line number	Diff line
		@@ -125,9 +125,13 @@ wait: mrc p14, 0, pc, c0, c1, 0
		* sort out different calling conventions
		*/
		.align
		.arm @ Always enter in ARM state
		start:
		.type start,#function
		.rept 8
		THUMB( adr r12, BSYM(1f) )
		THUMB( bx r12 )
		THUMB( .rept 6 )
		ARM( .rept 8 )
		mov r0, r0
		.endr

		@@ -135,6 +139,7 @@ start:
		.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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