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

Matthieu Longo matthieu.longo@arm.com
Mon Nov 25 17:33:14 GMT 2024 
On 2024-11-25 16:40, Jan Beulich wrote:
> On 25.11.2024 17:28, Matthieu Longo wrote:
>> --- a/include/dwarf2.def
>> +++ b/include/dwarf2.def
>> @@ -788,9 +788,11 @@ DW_CFA (DW_CFA_MIPS_advance_loc8, 0x1d)
>>   /* GNU extensions.
>>      NOTE: DW_CFA_GNU_window_save is multiplexed on Sparc and AArch64.  */
>>   DW_CFA (DW_CFA_GNU_window_save, 0x2d)
>> -DW_CFA_DUP (DW_CFA_AARCH64_negate_ra_state, 0x2d)
>>   DW_CFA (DW_CFA_GNU_args_size, 0x2e)
>>   DW_CFA (DW_CFA_GNU_negative_offset_extended, 0x2f)
>> +/* AArch64 extensions. */
>> +DW_CFA (DW_CFA_AARCH64_negate_ra_state_with_pc, 0x2c)
>> +DW_CFA_DUP (DW_CFA_AARCH64_negate_ra_state, 0x2d)
> 
> While I understand an important aspect here is to stay in sync with the
> gcc incarnation of this file, I don't think it's a good idea to re-order
> things. Instead 0x2c should go further up, such that all of these entries
> remain numerically sorted. Only then will the 2nd line of the comment
> actually remain directly next to _both_ values it applies to.
> 
> Jan

The numeric sorting does not seem to be always respected when it makes 
sense to group the entries.
For instance, line 783, a few line above:

  DW_CFA (DW_CFA_lo_user, 0x1c)
  DW_CFA (DW_CFA_hi_user, 0x3f)

I can do as you proposed, I could move the AArch64 extensions between 
the SGI/MIPS entries and GNU ones.
Something like:

   /* SGI/MIPS specific.  */
   DW_CFA (DW_CFA_MIPS_advance_loc8, 0x1d)
   /* AArch64 extensions. */
   DW_CFA (DW_CFA_AARCH64_negate_ra_state_with_pc, 0x2c)
   DW_CFA_DUP (DW_CFA_AARCH64_negate_ra_state, 0x2d)
   /* GNU extensions.
    NOTE: DW_CFA_GNU_window_save is multiplexed on Sparc and AArch64.  */
   DW_CFA (DW_CFA_GNU_window_save, 0x2d)
   DW_CFA (DW_CFA_GNU_args_size, 0x2e)

Do you think it looks better ?
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