linux-kernel - [tip: x86/core] x86/asm: Differentiate between code and function alignment

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Date:   Mon, 17 Oct 2022 14:54:23 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/core] x86/asm: Differentiate between code and function alignment

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     8eb5d34e77c63fde8af21c691bcf6e3cd87f7829
Gitweb:        https://git.kernel.org/tip/8eb5d34e77c63fde8af21c691bcf6e3cd87f7829
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Thu, 15 Sep 2022 13:10:48 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 17 Oct 2022 16:40:58 +02:00

x86/asm: Differentiate between code and function alignment

Create SYM_F_ALIGN to differentiate alignment requirements between
SYM_CODE and SYM_FUNC.

This distinction is useful later when adding padding in front of
functions; IOW this allows following the compiler's
patchable-function-entry option.

[peterz: Changelog]

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lore.kernel.org/r/20220915111143.824822743@infradead.org
---
 arch/x86/include/asm/linkage.h | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h
index 9ee0e28..c2d6e27 100644
--- a/arch/x86/include/asm/linkage.h
+++ b/arch/x86/include/asm/linkage.h
@@ -12,11 +12,15 @@
 #define asmlinkage CPP_ASMLINKAGE __attribute__((regparm(0)))
 #endif /* CONFIG_X86_32 */
 
-#ifdef __ASSEMBLY__
-
 #define __ALIGN		.balign CONFIG_FUNCTION_ALIGNMENT, 0x90;
 #define __ALIGN_STR	__stringify(__ALIGN)
 
+#define ASM_FUNC_ALIGN		__ALIGN_STR
+#define __FUNC_ALIGN		__ALIGN
+#define SYM_F_ALIGN		__FUNC_ALIGN
+
+#ifdef __ASSEMBLY__
+
 #if defined(CONFIG_RETHUNK) && !defined(__DISABLE_EXPORTS) && !defined(BUILD_VDSO)
 #define RET	jmp __x86_return_thunk
 #else /* CONFIG_RETPOLINE */
@@ -55,7 +59,7 @@
 
 /* SYM_FUNC_START -- use for global functions */
 #define SYM_FUNC_START(name)				\
-	SYM_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)	\
+	SYM_START(name, SYM_L_GLOBAL, SYM_F_ALIGN)	\
 	ENDBR
 
 /* SYM_FUNC_START_NOALIGN -- use for global functions, w/o alignment */
@@ -65,7 +69,7 @@
 
 /* SYM_FUNC_START_LOCAL -- use for local functions */
 #define SYM_FUNC_START_LOCAL(name)			\
-	SYM_START(name, SYM_L_LOCAL, SYM_A_ALIGN)	\
+	SYM_START(name, SYM_L_LOCAL, SYM_F_ALIGN)	\
 	ENDBR
 
 /* SYM_FUNC_START_LOCAL_NOALIGN -- use for local functions, w/o alignment */
@@ -75,7 +79,7 @@
 
 /* SYM_FUNC_START_WEAK -- use for weak functions */
 #define SYM_FUNC_START_WEAK(name)			\
-	SYM_START(name, SYM_L_WEAK, SYM_A_ALIGN)	\
+	SYM_START(name, SYM_L_WEAK, SYM_F_ALIGN)	\
 	ENDBR
 
 /* SYM_FUNC_START_WEAK_NOALIGN -- use for weak functions, w/o alignment */