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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>
This commit is contained in:
Dave Martin 2010-11-29 19:43:27 +01:00 committed by Russell King
parent bfa64c4ab1
commit 26e5ca93dd
2 changed files with 6 additions and 6 deletions
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5
arch/arm/boot/Makefile
View File

@ -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)

7
arch/arm/boot/compressed/head.S
View File

@ -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