linux-kernel - [PATCH v3 44/64] x86/jump_label: Define ELF section entry size for jump labels

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Message-ID: <7217634a8158e56703dfe22199f1b9c08c501ae3.1750980517.git.jpoimboe@kernel.org>
Date: Thu, 26 Jun 2025 16:55:31 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
	Petr Mladek <pmladek@...e.com>,
	Miroslav Benes <mbenes@...e.cz>,
	Joe Lawrence <joe.lawrence@...hat.com>,
	live-patching@...r.kernel.org,
	Song Liu <song@...nel.org>,
	laokz <laokz@...mail.com>,
	Jiri Kosina <jikos@...nel.org>,
	Marcos Paulo de Souza <mpdesouza@...e.com>,
	Weinan Liu <wnliu@...gle.com>,
	Fazla Mehrab <a.mehrab@...edance.com>,
	Chen Zhongjin <chenzhongjin@...wei.com>,
	Puranjay Mohan <puranjay@...nel.org>,
	Dylan Hatch <dylanbhatch@...gle.com>
Subject: [PATCH v3 44/64] x86/jump_label: Define ELF section entry size for jump labels

In preparation for the objtool klp diff subcommand, define the entry
size for the __jump_table section in its ELF header.  This will allow
tooling to extract individual entries.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 arch/x86/include/asm/jump_label.h | 17 +++++++++++------
 kernel/bounds.c                   |  4 ++++
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index cd21554b3675..7a6b0e5d85c1 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -12,12 +12,17 @@
 #include <linux/stringify.h>
 #include <linux/types.h>
 
-#define JUMP_TABLE_ENTRY(key, label)			\
-	".pushsection __jump_table,  \"a\"\n\t"		\
-	_ASM_ALIGN "\n\t"				\
-	".long 1b - . \n\t"				\
-	".long " label " - . \n\t"			\
-	_ASM_PTR " " key " - . \n\t"			\
+#ifndef COMPILE_OFFSETS
+#include <generated/bounds.h>
+#endif
+
+#define JUMP_TABLE_ENTRY(key, label)				\
+	".pushsection __jump_table,  \"aM\", @progbits, "	\
+	__stringify(JUMP_ENTRY_SIZE) "\n\t"			\
+	_ASM_ALIGN "\n\t"					\
+	".long 1b - . \n\t"					\
+	".long " label " - . \n\t"				\
+	_ASM_PTR " " key " - . \n\t"				\
 	".popsection \n\t"
 
 /* This macro is also expanded on the Rust side. */
diff --git a/kernel/bounds.c b/kernel/bounds.c
index 02b619eb6106..e4c7ded3dc48 100644
--- a/kernel/bounds.c
+++ b/kernel/bounds.c
@@ -13,6 +13,7 @@
 #include <linux/kbuild.h>
 #include <linux/log2.h>
 #include <linux/spinlock_types.h>
+#include <linux/jump_label.h>
 
 int main(void)
 {
@@ -29,6 +30,9 @@ int main(void)
 #else
 	DEFINE(LRU_GEN_WIDTH, 0);
 	DEFINE(__LRU_REFS_WIDTH, 0);
+#endif
+#if defined(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE) && defined(CONFIG_JUMP_LABEL)
+	DEFINE(JUMP_ENTRY_SIZE, sizeof(struct jump_entry));
 #endif
 	/* End of constants */
 
-- 
2.49.0