linux-kernel - [RFC][PATCH 1/9] jump_label, x86: Strip ASM jump

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Date:   Mon, 07 Oct 2019 10:44:44 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     peterz@...radead.org, linux-kernel@...r.kernel.org,
        rostedt@...dmis.org, mhiramat@...nel.org, bristot@...hat.com,
        jbaron@...mai.com, torvalds@...ux-foundation.org,
        tglx@...utronix.de, mingo@...nel.org, namit@...are.com,
        hpa@...or.com, luto@...nel.org, ard.biesheuvel@...aro.org,
        jpoimboe@...hat.com, hjl.tools@...il.com
Subject: [RFC][PATCH 1/9] jump_label, x86: Strip ASM jump_label support

In prepration for variable size jump_label support; remove all ASM
bits that are not used.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/entry/calling.h          |    2 +-
 arch/x86/include/asm/jump_label.h |   28 ++++------------------------
 2 files changed, 5 insertions(+), 25 deletions(-)

--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -337,7 +337,7 @@ For 32-bit we have the following convent
 .macro CALL_enter_from_user_mode
 #ifdef CONFIG_CONTEXT_TRACKING
 #ifdef CONFIG_JUMP_LABEL
-	STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0
+	STATIC_BRANCH_FALSE_LIKELY .Lafter_call_\@, context_tracking_enabled
 #endif
 	call enter_from_user_mode
 .Lafter_call_\@:
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -55,36 +55,16 @@ static __always_inline bool arch_static_
 
 #else	/* __ASSEMBLY__ */
 
-.macro STATIC_JUMP_IF_TRUE target, key, def
+.macro STATIC_BRANCH_FALSE_LIKELY target, key
 .Lstatic_jump_\@:
-	.if \def
 	/* Equivalent to "jmp.d32 \target" */
 	.byte		0xe9
-	.long		\target - .Lstatic_jump_after_\@
-.Lstatic_jump_after_\@:
-	.else
-	.byte		STATIC_KEY_INIT_NOP
-	.endif
-	.pushsection __jump_table, "aw"
-	_ASM_ALIGN
-	.long		.Lstatic_jump_\@ - ., \target - .
-	_ASM_PTR	\key - .
-	.popsection
-.endm
+	.long		\target - (. + 4)
 
-.macro STATIC_JUMP_IF_FALSE target, key, def
-.Lstatic_jump_\@:
-	.if \def
-	.byte		STATIC_KEY_INIT_NOP
-	.else
-	/* Equivalent to "jmp.d32 \target" */
-	.byte		0xe9
-	.long		\target - .Lstatic_jump_after_\@
-.Lstatic_jump_after_\@:
-	.endif
 	.pushsection __jump_table, "aw"
 	_ASM_ALIGN
-	.long		.Lstatic_jump_\@ - ., \target - .
+	.long		.Lstatic_jump_\@ - .
+	.long		\target - .
 	_ASM_PTR	\key + 1 - .
 	.popsection
 .endm