From: Wilco Dijkstra <wilco.dijkstra@arm.com>
Date: Tue, 26 Sep 2023 15:27:38 +0000 (+0100)
Subject: AArch64: Remove BTI from outline atomics
X-Git-Tag: basepoints/gcc-15~5858
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e1e18ea0defe9e1ee35abbbe5279028ecf786957;p=thirdparty%2Fgcc.git

AArch64: Remove BTI from outline atomics

The outline atomic functions have hidden visibility and can only be called
directly.  Therefore we can remove the BTI at function entry.  This improves
security by reducing the number of indirect entry points in a binary.
The BTI markings on the objects are still emitted.

libgcc/ChangeLog:
	* config/aarch64/lse.S (BTI_C): Remove define.
---

diff --git a/libgcc/config/aarch64/lse.S b/libgcc/config/aarch64/lse.S
index dde3a28e07b1..f64a3e98bfae 100644
--- a/libgcc/config/aarch64/lse.S
+++ b/libgcc/config/aarch64/lse.S
@@ -46,6 +46,9 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  * direct branch.  The choice of LSE vs non-LSE is done via one byte load
  * followed by a well-predicted direct branch.  The functions are compiled
  * separately to minimize code size.
+ *
+ * Since these functions have hidden visibility and are never called
+ * indirectly, they do not need to start with a BTI instruction.
  */
 
 #include "auto-target.h"
@@ -161,8 +164,6 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define tmp1	17
 #define tmp2	15
 
-#define BTI_C	hint	34
-
 /* Start and end a function.  */
 .macro	STARTFN name
 	.text
@@ -172,7 +173,6 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 	.type	\name, %function
 	.cfi_startproc
 \name:
-	BTI_C
 .endm
 
 .macro	ENDFN name