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ARM: zImage: make sure appended DTB doesn't get overwritten by kernel .bss 

The appended DTB gets relocated with the decompressor code to get out
of the way of the decompressed kernel.  However the kernel's .bss section
may be larger than the relocated code and data, and then the DTB gets
overwritten.  Let's make sure the relocation takes care of moving zImage
far enough so no such conflict with .bss occurs.

Thanks to Tony Lindgren <tony@atomide.com> for figuring out this issue.

While at it, let's clean up the code a bit so that the wont_overwrite
symbol is used while determining if a conflict exists, making the above
change more precise as well as eliminating some ARM/THUMB alternates.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Tested-by: Dave Martin <dave.martin@linaro.org>
Tested-by: Thomas Abraham <thomas.abraham@linaro.org>
This commit is contained in:
Nicolas Pitre 2011-06-12 01:07:33 -04:00 committed by Nicolas Pitre
parent e2a6a3aafa
commit 5ffb04f669
2 changed files with 18 additions and 4 deletions
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3
arch/arm/boot/compressed/Makefile
View File

@ -104,6 +104,9 @@ endif
ccflags-y := -fpic -fno-builtin
asflags-y := -Wa,-march=all
# Supply kernel BSS size to the decompressor via a linker symbol.
KBSS_SZ = $(shell size $(obj)/../../../../vmlinux | awk 'END{print $$3}')
LDFLAGS_vmlinux = --defsym _kernel_bss_size=$(KBSS_SZ)
# Supply ZRELADDR to the decompressor via a linker symbol.
ifneq ($(CONFIG_AUTO_ZRELADDR),y)
LDFLAGS_vmlinux += --defsym zreladdr=$(ZRELADDR)

19
arch/arm/boot/compressed/head.S
View File

@ -248,6 +248,18 @@ restart: adr r0, LC0
mov r8, r6 @ use the appended device tree
/*
* Make sure that the DTB doesn't end up in the final
* kernel's .bss area. To do so, we adjust the decompressed
* kernel size to compensate if that .bss size is larger
* than the relocated code.
*/
ldr r5, =_kernel_bss_size
adr r1, wont_overwrite
sub r1, r6, r1
subs r1, r5, r1
addhi r9, r9, r1
/* Get the dtb's size */
ldr r5, [r6, #4]
#ifndef __ARMEB__
@ -276,15 +288,14 @@ dtb_check_done:
* r10 = end of this image, including bss/stack/malloc space if non XIP
* We basically want:
* r4 - 16k page directory >= r10 -> OK
* r4 + image length <= current position (pc) -> OK
* r4 + image length <= address of wont_overwrite -> OK
*/
add r10, r10, #16384
cmp r4, r10
bhs wont_overwrite
add r10, r4, r9
ARM( cmp r10, pc )
THUMB( mov lr, pc )
THUMB( cmp r10, lr )
adr r9, wont_overwrite
cmp r10, r9
bls wont_overwrite
/*