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

[Indu Bhagat]

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

> 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 ?

>       { "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

> +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)