[PATCH v3] ARM: kprobes: move __kretprobe_trampoline to out of line assembler

[Nick Desaulniers]

On Fri, Sep 30, 2022 at 2:15 PM Nick Desaulniers
<ndesaulniers at google.com> wrote:
>
> commit 1069c1dd20a3 ("ARM: 9231/1: Recover kretprobes return address for
> EABI stack unwinder")
> tickled a bug in clang's integrated assembler where the .save and .pad
> directives must have corresponding .fnstart directives. The integrated
> assembler is unaware that the compiler will be generating the .fnstart
> directive.
>
>   arch/arm/probes/kprobes/core.c:409:30: error: .fnstart must precede
>   .save or .vsave directives
>   <inline asm>:3:2: note: instantiated into assembly here
>   .save   {sp, lr, pc}
>   ^
>   arch/arm/probes/kprobes/core.c:412:29: error: .fnstart must precede
>   .pad directive
>   <inline asm>:6:2: note: instantiated into assembly here
>   .pad    #52
>   ^
>

Chen, I noticed that your patch was discarded; it's not in linux-next today.
https://lore.kernel.org/linux-arm-kernel/YzHPGvhLkdQcDYzx@shell.armlinux.org.uk/
https://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=9231/1
How would you like to proceed here?

I think moving this out of line, incorporating Ard's feedback, then
putting the UNWIND directives on top might be the way to go. What do
you think?
-- 
Thanks,
~Nick Desaulniers