[PATCH v3 3/4] aarch64 DWARF: add new CFI directive for PAuth_LR

[Matthieu Longo]

On 2025-01-13 23:29, Indu Bhagat wrote:
> On 1/13/25 3:22 AM, Matthieu Longo wrote:
>> This patch adds a new CFI directive (cfi_negate_ra_state_with_pc) which
>> set an additional bit in the RA state to inform that RA was signed with
>> SP but also PC as an additional diversifier.
>>
>> RA state | Description
>> 0b00     | Return address not signed (default if no cfi_negate_ra_state*)
>> 0b01     | Return address signed with SP (cfi_negate_ra_state)
>> 0b10     | Invalid state
>> 0b11     | Return address signed with SP+PC (cfi_negate_ra_state_with_pc)
>> ---
>>   bfd/elf-eh-frame.c |  1 +
>>   binutils/dwarf.c   |  5 +++++
>>   gas/dw2gencfi.c    | 10 ++++++++++
>>   gas/scfidw2gen.c   |  1 +
>>   include/dwarf2.def |  2 ++
>>   5 files changed, 19 insertions(+)
>>
> 
> Comments below. The changes look OK to me for the scfi*; I cannot 
> approve the other components.
> 
> Thanks

Jan Beulich also approved the changes in v2: 
https://inbox.sourceware.org/binutils/ddbf42f2-2b19-4faa-84d1-5f2a77b31a50@suse.com/

Thanks.

>> diff --git a/bfd/elf-eh-frame.c b/bfd/elf-eh-frame.c
>> index d903e27a676..b6f5078bb33 100644
>> --- a/bfd/elf-eh-frame.c
>> +++ b/bfd/elf-eh-frame.c
>> @@ -359,6 +359,7 @@ skip_cfa_op (bfd_byte **iter, bfd_byte *end, 
>> unsigned int encoded_ptr_width)
>>       case DW_CFA_remember_state:
>>       case DW_CFA_restore_state:
>>       case DW_CFA_GNU_window_save:
>> +    case DW_CFA_AARCH64_negate_ra_state_with_pc:
>>         /* No arguments.  */
>>         return true;
>> diff --git a/binutils/dwarf.c b/binutils/dwarf.c
>> index 626efb2eb9a..8e004cea839 100644
>> --- a/binutils/dwarf.c
>> +++ b/binutils/dwarf.c
>> @@ -10408,6 +10408,11 @@ display_debug_frames (struct dwarf_section 
>> *section,
>>             fc->pc_begin += ofs;
>>             break;
>> +        case DW_CFA_AARCH64_negate_ra_state_with_pc:
>> +          if (! do_debug_frames_interp)
>> +        printf ("  DW_CFA_AARCH64_negate_ra_state_with_pc\n");
>> +          break;
>> +
>>           case DW_CFA_GNU_window_save:
>>             if (! do_debug_frames_interp)
>>           printf ("  %s\n", DW_CFA_GNU_window_save_name[is_aarch64]);
>> diff --git a/gas/dw2gencfi.c b/gas/dw2gencfi.c
>> index fbeb697af09..c984d8326d0 100644
>> --- a/gas/dw2gencfi.c
>> +++ b/gas/dw2gencfi.c
>> @@ -714,6 +714,7 @@ 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 },
> 
> Also keep the cfi_pseudo_table[] for the case when "#else /* 
> TARGET_USE_CFIPOP */" in the file in sync ?

Fixed. Thanks for catching this. cfi_negate_ra_state was also absent, so 
I added it along cfi_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 },
>> @@ -914,6 +915,10 @@ 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;
>> +
>>       case CFI_signal_frame:
>>         frchain_now->frch_cfi_data->cur_fde_data->signal_frame = 1;
>>         break;
>> @@ -1754,6 +1759,10 @@ output_cfi_insn (struct cfi_insn_data *insn)
>>         out_one (DW_CFA_GNU_window_save);
>>         break;
>> +    case DW_CFA_AARCH64_negate_ra_state_with_pc:
>> +      out_one (DW_CFA_AARCH64_negate_ra_state_with_pc);
>> +      break;
>> +
>>       case CFI_escape:
>>         {
>>       struct cfi_escape_data *e;
>> @@ -2212,6 +2221,7 @@ cfi_change_reg_numbers (struct cfi_insn_data 
>> *insn, segT ccseg)
>>       case DW_CFA_remember_state:
>>       case DW_CFA_restore_state:
>>       case DW_CFA_GNU_window_save:
>> +    case DW_CFA_AARCH64_negate_ra_state_with_pc:
>>       case CFI_escape:
>>       case CFI_label:
>>         break;
>> diff --git a/gas/scfidw2gen.c b/gas/scfidw2gen.c
>> index 7463207e170..9b3ad4b13e0 100644
>> --- a/gas/scfidw2gen.c
>> +++ b/gas/scfidw2gen.c
>> @@ -113,6 +113,7 @@ const pseudo_typeS scfi_pseudo_table[] =
>>       { "cfi_restore_state", dot_scfi_ignore, 0 },
>>       { "cfi_window_save", dot_scfi_ignore, 0 },
>>       { "cfi_negate_ra_state", dot_scfi_ignore, 0 },
>> +    { "cfi_negate_ra_state_with_pc", dot_scfi_ignore, 0 },
>>       { "cfi_escape", dot_scfi_ignore, 0 },
>>       { "cfi_personality", dot_scfi_ignore, 0 },
>>       { "cfi_personality_id", dot_scfi_ignore, 0 },
>> diff --git a/include/dwarf2.def b/include/dwarf2.def
>> index 63cb35560e7..477b2ca20c0 100644
>> --- a/include/dwarf2.def
>> +++ b/include/dwarf2.def
>> @@ -785,6 +785,8 @@ DW_CFA (DW_CFA_hi_user, 0x3f)
>>   /* SGI/MIPS specific.  */
>>   DW_CFA (DW_CFA_MIPS_advance_loc8, 0x1d)
>> +/* AArch64 extensions. */
> 
> Nit: dot, space, space, end of comment

Fixed.

>> +DW_CFA (DW_CFA_AARCH64_negate_ra_state_with_pc, 0x2c)
>>   /* GNU extensions.
>>      NOTE: DW_CFA_GNU_window_save is multiplexed on Sparc and 
>> AArch64.  */
>>   DW_CFA (DW_CFA_GNU_window_save, 0x2d)
>