[PATCH v1 3/4] aarch64 DWARF: add new CFI directive for PAuth_LR

[Matthieu Longo]

On 2024-11-25 16:42, Jan Beulich wrote:
> On 25.11.2024 17:28, Matthieu Longo wrote:
>> --- a/gas/dw2gencfi.c
>> +++ b/gas/dw2gencfi.c
>> @@ -718,6 +718,7 @@ const pseudo_typeS cfi_pseudo_table[] =
>>       { "cfi_restore_state", dot_cfi, DW_CFA_restore_state },
>>       { "cfi_window_save", dot_cfi, DW_CFA_GNU_window_save },
>>       { "cfi_negate_ra_state", dot_cfi, DW_CFA_AARCH64_negate_ra_state },
>> +    { "cfi_negate_ra_state_with_pc", dot_cfi, DW_CFA_AARCH64_negate_ra_state_with_pc },
>>       { "cfi_escape", dot_cfi_escape, 0 },
>>       { "cfi_signal_frame", dot_cfi, CFI_signal_frame },
>>       { "cfi_personality", dot_cfi_personality, 0 },
>> @@ -918,6 +919,10 @@ dot_cfi (int arg)
>>         cfi_add_CFA_insn (DW_CFA_GNU_window_save);
>>         break;
>>   
>> +    case DW_CFA_AARCH64_negate_ra_state_with_pc:
>> +      cfi_add_CFA_insn (DW_CFA_AARCH64_negate_ra_state_with_pc);
>> +      break;
> 
> Oh, and: Shouldn't we learn from the confusion about the two other,
> aliasing directives? IOW - what if this new directive is used on other
> than Aarch64? Imo that would better be refused, to avoid ending up with
> a similar problem again.
> 
> Jan

I agree with you, that would be the best approach.
That's what I did recently in GCC by moving architecture extension to 
the backend: 
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=9e1c71bab50d51a1a8ec1a75080ffde6ca3d854c
Unfortunately, from my understanding, this requires a major refactoring 
of the current implementation.