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SubjectRe: [PATCH 1/1] ARM: compressed/head.S: fix __nop macro rept number for ARMv7M
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Hi Ard

On 05/18/2017 01:16 PM, Ard Biesheuvel wrote:
> On 12 May 2017 at 08:22, Patrice CHOTARD <patrice.chotard@st.com> wrote:
>> Hi all
>>
>> It's a gentle reminder to not forgot this patch.
>>
>> Thanks
>>
>> Patrice
>>
>> On 04/25/2017 11:01 AM, patrice.chotard@st.com wrote:
>>> From: Patrice Chotard <patrice.chotard@st.com>
>>>
>>> In zImage, _magic_sig is located at offset 0x24.
>>> But for ARMv7M architecture which enable CPU_THUMBONLY
>>> and !EFI_STUB kernel flag, _magic_sig is located at offset 0x14
>>>
>>> 00000000 00 46 00 46 00 46 00 46 00 46 00 46 00 46 0f f2 |.F.F.F.F.F.F.F.ò|
>>> 00000010 15 0c 60 47 18 28 6f 01 00 00 00 00 28 5c 0e 00 |..`G.(o.....(\..|
>>> 00000020 01 02 03 04 0f 46 90 46 00 00 00 00 00 00 00 00 |.....F.F........|
>>>
>>> Reproduced with stm32_defconfig with XIP_KERNEL flag disabled.
>>>
>>> To restore correct _magic_sig offset at 0x24, we add 8 additional
>>> "mov r0, r0" instruction.
>>>
>>> Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
>>> ---
>>> arch/arm/boot/compressed/head.S | 3 ++-
>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
>>> index 9150f97..5d9cda3 100644
>>> --- a/arch/arm/boot/compressed/head.S
>>> +++ b/arch/arm/boot/compressed/head.S
>>> @@ -127,7 +127,8 @@
>>> AR_CLASS( .arm )
>>> start:
>>> .type start,#function
>>> - .rept 7
>>> + ARM( .rept 7)
>>> + THUMB( .rept 15)
>>>
>
> Could you try using W(mov) instead of mov in the definition of __nop ?

If i use W(mov) instead of mov in __nop macro, i need to add one
additional "mov r0,r0" in THUMB case as following :


start:
.type start,#function
.rept 7
__nop
.endr
ARM( mov r0, r0 )
ARM( b 1f )
+ THUMB( mov r0, r0 )
THUMB( badr r12, 1f )
THUMB( bx r12 )

.word _magic_sig @ Magic numbers to help the loader
.word _magic_start @ absolute load/run zImage address
.word _magic_end @ zImage end address
.word 0x04030201 @ endianness flag


Which implementation do you prefer ?

Thanks

Patrice
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