On Thu, Nov 10, 2022 at 10:38 AM Srinath Parvathaneni via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Hi,
>
> This patch adds support for Arm frame unwinding instruction "0xb5" [1]. When
> an exception is taken and "0xb5" instruction is encounter during runtime
> stack-unwinding, we use effective vsp as modifier in pointer authentication.
> On completion of stack unwinding if "0xb5" instruction is not encountered
> then CFA will be used as modifier in pointer authentication.
>
> [1]
> https://github.com/ARM-software/abi-aa/releases/download/2022Q3/ehabi32.pdf
>
> Regression tested on arm-none-eabi target and found no regressions.
>
> Ok for master?
>
No, not yet.
Presumably the logic to produce 0xb5 is in the source base and this
was tested with suitable options that produce said opcode ? I see no
logic in place to produce the said opcode in the backend in a quick
read as the pacbti patches still seem to be in review. ?
So what was the test suite run actually testing ?
regards
Ramana
> Regards,
> Srinath.
>
> gcc/ChangeLog:
>
> 2022-11-09 Srinath Parvathaneni <srinath.parvathan...@arm.com>
>
> * libgcc/config/arm/pr-support.c (__gnu_unwind_execute): Decode opcode
> "0xb5".
>
>
> ############### Attachment also inlined for ease of reply
> ###############
>
>
> diff --git a/libgcc/config/arm/pr-support.c b/libgcc/config/arm/pr-support.c
> index
> e48854587c667a959aa66ccc4982231f63333ecc..73e4942a39b34a83c2da85def6b13e82ec501552
> 100644
> --- a/libgcc/config/arm/pr-support.c
> +++ b/libgcc/config/arm/pr-support.c
> @@ -107,7 +107,9 @@ __gnu_unwind_execute (_Unwind_Context * context,
> __gnu_unwind_state * uws)
> _uw op;
> int set_pc;
> int set_pac = 0;
> + int set_pac_sp = 0;
> _uw reg;
> + _uw sp;
>
> set_pc = 0;
> for (;;)
> @@ -124,10 +126,11 @@ __gnu_unwind_execute (_Unwind_Context * context,
> __gnu_unwind_state * uws)
> #if defined(TARGET_HAVE_PACBTI)
> if (set_pac)
> {
> - _uw sp;
> _uw lr;
> _uw pac;
> - _Unwind_VRS_Get (context, _UVRSC_CORE, R_SP, _UVRSD_UINT32,
> &sp);
> + if (!set_pac_sp)
> + _Unwind_VRS_Get (context, _UVRSC_CORE, R_SP, _UVRSD_UINT32,
> + &sp);
> _Unwind_VRS_Get (context, _UVRSC_CORE, R_LR, _UVRSD_UINT32,
> &lr);
> _Unwind_VRS_Get (context, _UVRSC_PAC, R_IP,
> _UVRSD_UINT32, &pac);
> @@ -259,7 +262,19 @@ __gnu_unwind_execute (_Unwind_Context * context,
> __gnu_unwind_state * uws)
> continue;
> }
>
> - if ((op & 0xfc) == 0xb4) /* Obsolete FPA. */
> + /* Use current VSP as modifier in PAC validation. */
> + if (op == 0xb5)
> + {
> + if (set_pac)
> + _Unwind_VRS_Get (context, _UVRSC_CORE, R_SP, _UVRSD_UINT32,
> + &sp);
> + else
> + return _URC_FAILURE;
> + set_pac_sp = 1;
> + continue;
> + }
> +
> + if ((op & 0xfd) == 0xb6) /* Obsolete FPA. */
> return _URC_FAILURE;
>
> /* op & 0xf8 == 0xb8. */
>
>
>
