From 55a2d8096a799c682922b03bef7c0d4e4c1c8d7b Mon Sep 17 00:00:00 2001
From: Srinath Parvathaneni <srinath.parvathaneni@arm.com>
Date: Mon, 23 Jan 2023 11:13:18 +0000
Subject: [PATCH] arm: Add support for new frame unwinding instruction "0xb5".
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
libgcc/ChangeLog:
2022-11-09 Srinath Parvathaneni <srinath.parvathaneni@arm.com>
* config/arm/pr-support.c (__gnu_unwind_execute): Decode opcode
"0xb5".
---
libgcc/config/arm/pr-support.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/libgcc/config/arm/pr-support.c b/libgcc/config/arm/pr-support.c
index abacfb62212c..9c9d4eed85f3 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);
@@ -259,6 +262,14 @@ __gnu_unwind_execute (_Unwind_Context * context, __gnu_unwind_state * uws)
continue;
}
+ /* Use current VSP as modifier in PAC validation. */
+ if (op == 0xb5)
+ {
+ _Unwind_VRS_Get (context, _UVRSC_CORE, R_SP, _UVRSD_UINT32, &sp);
+ set_pac_sp = 1;
+ continue;
+ }
+
if ((op & 0xfc) == 0xb4) /* Obsolete FPA. */
return _URC_FAILURE;
--
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