linux-kernel - [PATCH v3 48/64] x86/orc: Define ELF section entry size for unwind hints

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Message-ID: <edd9abc04a63d009d527a3dd69ebeb040236afb2.1750980517.git.jpoimboe@kernel.org>
Date: Thu, 26 Jun 2025 16:55:35 -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 48/64] x86/orc: Define ELF section entry size for unwind hints

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

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 include/linux/objtool.h | 11 ++++++++---
 kernel/bounds.c         |  4 ++++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 366ad004d794..c7a3851ae4ae 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -2,6 +2,10 @@
 #ifndef _LINUX_OBJTOOL_H
 #define _LINUX_OBJTOOL_H
 
+#ifndef COMPILE_OFFSETS
+#include <generated/bounds.h>
+#endif
+
 #include <linux/objtool_types.h>
 
 #ifdef CONFIG_OBJTOOL
@@ -10,9 +14,10 @@
 
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(type, sp_reg, sp_offset, signal)	\
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal)		\
 	"987: \n\t"						\
-	".pushsection .discard.unwind_hints\n\t"		\
+	".pushsection .discard.unwind_hints, \"M\", @progbits, "\
+		      __stringify(UNWIND_HINT_SIZE) "\n\t"	\
 	/* struct unwind_hint */				\
 	".long 987b - .\n\t"					\
 	".short " __stringify(sp_offset) "\n\t"			\
@@ -88,7 +93,7 @@
  */
 .macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0
 .Lhere_\@:
-	.pushsection .discard.unwind_hints
+	.pushsection .discard.unwind_hints, "M", @progbits, UNWIND_HINT_SIZE
 		/* struct unwind_hint */
 		.long .Lhere_\@ - .
 		.short \sp_offset
diff --git a/kernel/bounds.c b/kernel/bounds.c
index 21c37e3ea629..f9bc13727721 100644
--- a/kernel/bounds.c
+++ b/kernel/bounds.c
@@ -15,6 +15,7 @@
 #include <linux/spinlock_types.h>
 #include <linux/jump_label.h>
 #include <linux/static_call_types.h>
+#include <linux/objtool_types.h>
 
 int main(void)
 {
@@ -37,6 +38,9 @@ int main(void)
 #endif
 #ifdef CONFIG_HAVE_STATIC_CALL_INLINE
 	DEFINE(STATIC_CALL_TRAMP_KEY_SIZE, sizeof(struct static_call_tramp_key));
+#endif
+#ifdef CONFIG_OBJTOOL
+	DEFINE(UNWIND_HINT_SIZE, sizeof(struct unwind_hint));
 #endif
 	/* End of constants */
 
-- 
2.49.0