Commit 7e6b9db2 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Peter Zijlstra
Browse files

jump_label: make initial NOP patching the special case 



Instead of defaulting to patching NOP opcodes at init time, and leaving
it to the architectures to override this if this is not needed, switch
to a model where doing nothing is the default. This is the common case
by far, as only MIPS requires NOP patching at init time. On all other
architectures, the correct encodings are emitted by the compiler and so
no initial patching is needed.

Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220615154142.1574619-4-ardb@kernel.org
parent fdfd4289

Documentation/staging/static-keys.rst

+0 −3
Original line number Diff line number Diff line
@@ -201,9 +201,6 @@ static_key->entry field makes use of the two least significant bits. 
* ``void arch_jump_label_transform(struct jump_entry *entry, enum jump_label_type type)``,

    see: arch/x86/kernel/jump_label.c



* ``__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry, enum jump_label_type type)``,

    see: arch/x86/kernel/jump_label.c



* ``struct jump_entry``,

    see: arch/x86/include/asm/jump_label.h

arch/arc/kernel/jump_label.c

+0 −13
Original line number Diff line number Diff line
@@ -96,19 +96,6 @@ void arch_jump_label_transform(struct jump_entry *entry, 
	flush_icache_range(entry->code, entry->code + JUMP_LABEL_NOP_SIZE);

}



void arch_jump_label_transform_static(struct jump_entry *entry,

				      enum jump_label_type type)

{

	/*

	 * We use only one NOP type (1x, 4 byte) in arch_static_branch, so

	 * there's no need to patch an identical NOP over the top of it here.

	 * The generic code calls 'arch_jump_label_transform' if the NOP needs

	 * to be replaced by a branch, so 'arch_jump_label_transform_static' is

	 * never called with type other than JUMP_LABEL_NOP.

	 */

	BUG_ON(type != JUMP_LABEL_NOP);

}



#ifdef CONFIG_ARC_DBG_JUMP_LABEL

#define SELFTEST_MSG	"ARC: instruction generation self-test: "

arch/arm/kernel/jump_label.c

+0 −6
Original line number Diff line number Diff line
@@ -27,9 +27,3 @@ void arch_jump_label_transform(struct jump_entry *entry, 
{

	__arch_jump_label_transform(entry, type, false);

}
 


void arch_jump_label_transform_static(struct jump_entry *entry,

				      enum jump_label_type type)

{

	__arch_jump_label_transform(entry, type, true);

}

arch/arm64/kernel/jump_label.c

+0 −11
Original line number Diff line number Diff line
@@ -26,14 +26,3 @@ void arch_jump_label_transform(struct jump_entry *entry, 


	aarch64_insn_patch_text_nosync(addr, insn);

}
 


void arch_jump_label_transform_static(struct jump_entry *entry,

				      enum jump_label_type type)

{

	/*

	 * We use the architected A64 NOP in arch_static_branch, so there's no

	 * need to patch an identical A64 NOP over the top of it here. The core

	 * will call arch_jump_label_transform from a module notifier if the

	 * NOP needs to be replaced by a branch.

	 */

}

arch/mips/include/asm/jump_label.h

+2 −0
Original line number Diff line number Diff line
@@ -8,6 +8,8 @@ 
#ifndef _ASM_MIPS_JUMP_LABEL_H

#define _ASM_MIPS_JUMP_LABEL_H



#define arch_jump_label_transform_static arch_jump_label_transform



#ifndef __ASSEMBLY__



#include <linux/types.h>