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SubjectRe: [RFC v5 47/57] arm64: assembler: Add macro to annotate asm function having non standard stack-frame.
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?

Will

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