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SubjectRe: [RFC v5 47/57] arm64: assembler: Add macro to annotate asm function having non standard stack-frame.
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On 1/21/20 10:30 AM, Will Deacon wrote:
> On Thu, Jan 09, 2020 at 04:02:50PM +0000, Julien Thierry wrote:
>> From: Raphael Gault <raphael.gault@arm.com>
>>
>> Some functions don't have standard stack-frames but are intended
>> this way. In order for objtool to ignore those particular cases
>> we add a macro that enables us to annotate the cases we chose
>> to mark as particular.
>>
>> Signed-off-by: Raphael Gault <raphael.gault@arm.com>
>> Signed-off-by: Julien Thierry <jthierry@redhat.com>
>> ---
>> include/linux/frame.h | 19 ++++++++++++++++++-
>> 1 file changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/frame.h b/include/linux/frame.h
>> index 02d3ca2d9598..1e35e58ab259 100644
>> --- a/include/linux/frame.h
>> +++ b/include/linux/frame.h
>> @@ -11,14 +11,31 @@
>> *
>> * For more information, see tools/objtool/Documentation/stack-validation.txt.
>> */
>> +#ifndef __ASSEMBLY__
>> #define STACK_FRAME_NON_STANDARD(func) \
>> static void __used __section(.discard.func_stack_frame_non_standard) \
>> *__func_stack_frame_non_standard_##func = func
>> +#else
>> + /*
>> + * This macro is the arm64 assembler equivalent of the
>> + * macro STACK_FRAME_NON_STANDARD define at
>> + * ~/include/linux/frame.h
>> + */
>> + .macro asm_stack_frame_non_standard func
>> + .pushsection ".discard.func_stack_frame_non_standard"
>> + .quad \func
>> + .popsection
>> + .endm
>>
>> +#endif /* __ASSEMBLY__ */
>> #else /* !CONFIG_STACK_VALIDATION */
>>
>> +#ifndef __ASSEMBLY__
>> #define STACK_FRAME_NON_STANDARD(func)
>> -
>> +#else
>> + .macro asm_stack_frame_non_standard func
>> + .endm
>> +#endif /* __ASSEMBLY__ */
>
> Hmm. Given that we're currently going through the exercise of converting
> a bunch of ENTRY/ENDPROC macros to use the new SYM_{CODE,FUNC}_{START,END}
> macros, I would much prefer for this to be a new flavour of those.
>
> In fact, can you just use SYM_CODE_* for this?
>

You mean to not introduce the STACK_FRAME_NON_STANDARD() macro and just
mark the asm callable symbols that don't set up a stackframe as SYM_CODE_* ?

--
Julien Thierry

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