[PATCH v4 00/13] arm64: debug: remove hook registration, split exception entry

[Ada Couprie Diaz]

Hi Will,

On 27/06/2025 16:48, Will Deacon wrote:
> Hi Ada,
>
> On Fri, Jun 20, 2025 at 10:11:54PM +0100, Ada Couprie Diaz wrote:
>> This series simplifies the debug exception entry path by removing handler
>> registration mechanisms for the debug exception handlers, a holdover from
>> the arm kernel, as well as the break and stepping handlers.
>> This moves much of the code related to debug exceptions outside of
>> `mm/fault.c` where it didn't make much sense.
>> This allows us to split the debug exception entries: going from one common
>> path per EL for all debug exceptions to a unique one per exception and EL.
>>
>> The result is a much simpler and fully static exception entry path, which
>> we tailor to the different exceptions and their constraints.
> I think this looks great, thanks. I've left Reviewed-bys on everything
> and a minor nit on the last patch.
Thanks ! Added your tag and applied the nit, I raised the possibility 
earlier
so absolutely fine with it.
> However, the linker is less
> enthusiastic than me because it fails with this series and 'allnoconfig':
>
>    ld.lld: error: undefined symbol: do_breakpoint
>    >>> referenced by entry-common.c
>    >>>               arch/arm64/kernel/entry-common.o:(el1_breakpt) in archive vmlinux.a
>    >>> referenced by entry-common.c
>    >>>               arch/arm64/kernel/entry-common.o:(el0_breakpt) in archive vmlinux.a
>
>    ld.lld: error: undefined symbol: do_watchpoint
>    >>> referenced by entry-common.c
>    >>>               arch/arm64/kernel/entry-common.o:(el1_watchpt) in archive vmlinux.a
>    >>> referenced by entry-common.c
>    >>>               arch/arm64/kernel/entry-common.o:(el0_watchpt) in archive vmlinux.a
>    make[2]: *** [scripts/Makefile.vmlinux:91: vmlinux] Error 1
>
> Please can you take a look?
Apologies, I knew exactly what that was : hardware breakpoints being 
behind a config,
which I failed to consider when exposing the handlers in 
`include/asm/exception.h`.

I added a static inline stub for this case for both and built 
successfully with `allnoconfig`.
> Will

I sent a v5 with the changes mentioned here and the fix for `allnoconfig`.

Thanks,
Ada