[PATCH 04/14] ARM: set BE8 if LE in head code

Ben Dooks
2013-07-24T15:55:05Z

On 24/07/13 15:41, Will Deacon wrote:
> On Wed, Jul 24, 2013 at 11:27:52AM +0100, Ben Dooks wrote:
>> If we are booting in LE and compiled for BE8, then add code to
>> set the state to bE8. Since the instruction stream is always LE,
>> we do not need to do anything special to the instruction.
>>
>> Also ensure that the secondary processors are started in the same mode.
>>
>> Note, we do add about 20 bytes to the kernel image, but it seems easier
>> to do this than adding another configuration to change.
>>
>> Signed-off-by: Ben Dooks<ben.dooks@codethink.co.uk>
>> ---
>> arch/arm/boot/compressed/head.S | 1 +
>> arch/arm/kernel/head.S | 4 ++++
>> arch/arm/kernel/sleep.S | 1 +
>> 3 files changed, 6 insertions(+)
>>
>> diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
>> index 4eb8364..4d83bfd 100644
>> --- a/arch/arm/boot/compressed/head.S
>> +++ b/arch/arm/boot/compressed/head.S
>> @@ -135,6 +135,7 @@ start:
>> .word _edata @ zImage end address
>> THUMB( .thumb )
>> 1:
>> + ARM_BE8( setend be ) @ go BE8 if LE, no-op if BE8
>
> I find the comment here slightly confusing as it makes it sound like the
> macro expands to nothing if we're BE8 (which is clearly not the case).

I've changed it to "go BE8 if compiled for BE8"

>> mrs r9, cpsr
>> #ifdef CONFIG_ARM_VIRT_EXT
>> bl __hyp_stub_install @ get into SVC mode, reversibly
>> diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
>> index e40c0b3b..706c441 100644
>> --- a/arch/arm/kernel/head.S
>> +++ b/arch/arm/kernel/head.S
>> @@ -77,6 +77,7 @@
>>
>> __HEAD
>> ENTRY(stext)
>> + ARM_BE8(setend be ) @ ensure we are in BE8 mode
>
> Alignment issue here -- please try to align the instruction with the
> instructions below (it's awkward to read with all the brackets).

If I move it one to the left, then it gets coloured blue by
my editor, as it is the first thing on the line like the
ENTRY() macro.

>>
>> THUMB( adr r9, BSYM(1f) ) @ Kernel is always entered in ARM.
>> THUMB( bx r9 ) @ If this is a Thumb-2 kernel,
>> @@ -351,6 +352,9 @@ ENTRY(secondary_startup)
>> * the processor type - there is no need to check the machine type
>> * as it has already been validated by the primary processor.
>> */
>> +
>> + ARM_BE8(setend be) @ if system starts LE, go BE8
>> +
>> #ifdef CONFIG_ARM_VIRT_EXT
>> bl __hyp_stub_install_secondary
>> #endif
>> diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S
>> index 987dcf3..954c28a 100644
>> --- a/arch/arm/kernel/sleep.S
>> +++ b/arch/arm/kernel/sleep.S
>> @@ -81,6 +81,7 @@ ENDPROC(cpu_resume_after_mmu)
>> .data
>> .align
>> ENTRY(cpu_resume)
>> +ARM_BE8(setend be) @ ensure we are in BE mode
>
> Any reason to have three different comments for the same thing? I think you
> probably just need to comment the one in head.S.

I've changed the comments to match in.

--
Ben Dooks http://www.codethink.co.uk/
Senior Engineer Codethink - Providing Genius