Matthieu Longo <matthieu.lo...@arm.com> writes:
> On AArch64, the RA state informs the unwinder whether the return address
> is mangled and how, or not. This information is encoded in a boolean in
> the CFI row. This binary approach prevents from expressing more complex
> configuration, as it is the case with PAuth_LR introduced in Armv9.5-A.
>
> This patch addresses this limitation by replacing the boolean by an enum.
>
> gcc/ChangeLog:
>
> * dwarf2cfi.cc
> (struct dw_cfi_row): Declare a new enum type to replace ra_mangled.
> (cfi_row_equal_p): Use ra_state instead of ra_mangled.
> (dwarf2out_frame_debug_cfa_negate_ra_state): Same.
> (change_cfi_row): Same.
OK with the changes that Jakub pointed out.
Thanks,
Richard
> ---
> gcc/dwarf2cfi.cc | 24 ++++++++++++++++++------
> 1 file changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/gcc/dwarf2cfi.cc b/gcc/dwarf2cfi.cc
> index 6c80e0b17bd..023f61fb712 100644
> --- a/gcc/dwarf2cfi.cc
> +++ b/gcc/dwarf2cfi.cc
> @@ -57,6 +57,15 @@ along with GCC; see the file COPYING3. If not see
> #define DEFAULT_INCOMING_FRAME_SP_OFFSET INCOMING_FRAME_SP_OFFSET
> #endif
>
> +
> +/* Signing method used for return address authentication.
> + (AArch64 extension)*/
> +typedef enum
> +{
> + RA_no_signing = 0x0,
> + RA_signing_SP = 0x1,
> +} RA_signing_method_t;
> +
> /* A collected description of an entire row of the abstract CFI table. */
> struct GTY(()) dw_cfi_row
> {
> @@ -74,8 +83,8 @@ struct GTY(()) dw_cfi_row
> bool window_save;
>
> /* Aarch64 extension for DW_CFA_AARCH64_negate_ra_state.
> - True if the return address is in a mangled state. */
> - bool ra_mangled;
> + Enum which stores the return address state. */
> + RA_signing_method_t ra_state;
> };
>
> /* The caller's ORIG_REG is saved in SAVED_IN_REG. */
> @@ -859,7 +868,7 @@ cfi_row_equal_p (dw_cfi_row *a, dw_cfi_row *b)
> if (a->window_save != b->window_save)
> return false;
>
> - if (a->ra_mangled != b->ra_mangled)
> + if (a->ra_state != b->ra_state)
> return false;
>
> return true;
> @@ -1556,8 +1565,11 @@ dwarf2out_frame_debug_cfa_negate_ra_state (void)
> {
> dw_cfi_ref cfi = new_cfi ();
> cfi->dw_cfi_opc = DW_CFA_AARCH64_negate_ra_state;
> + cur_row->ra_state =
> + (cur_row->ra_state == RA_no_signing)
> + ? RA_signing_SP
> + : RA_no_signing;
> add_cfi (cfi);
> - cur_row->ra_mangled = !cur_row->ra_mangled;
> }
>
> /* Record call frame debugging information for an expression EXPR,
> @@ -2414,12 +2426,12 @@ change_cfi_row (dw_cfi_row *old_row, dw_cfi_row
> *new_row)
> {
> dw_cfi_ref cfi = new_cfi ();
>
> - gcc_assert (!old_row->ra_mangled && !new_row->ra_mangled);
> + gcc_assert (!old_row->ra_state && !new_row->ra_state);
> cfi->dw_cfi_opc = DW_CFA_GNU_window_save;
> add_cfi (cfi);
> }
>
> - if (old_row->ra_mangled != new_row->ra_mangled)
> + if (old_row->ra_state != new_row->ra_state)
> {
> dw_cfi_ref cfi = new_cfi ();
