linux-kernel - [PATCH 2/4] x86/asm: Remove ANNOTATE_DATA

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Message-ID: <ae2dfc967f372fa21e78e7ef2b89389789a42e70.1764137163.git.jpoimboe@kernel.org>
Date: Tue, 25 Nov 2025 22:06:58 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH 2/4] x86/asm: Remove ANNOTATE_DATA_SPECIAL usage

Instead of manually annotating each __ex_table entry, just make the
section mergeable and store the entry size in the ELF section header.

Either way works for objtool create_fake_symbols(), this way produces
cleaner code generation.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 arch/um/include/asm/Kbuild                 |  1 -
 arch/um/include/shared/common-offsets.h    |  1 +
 arch/x86/include/asm/asm.h                 | 25 ++++++++++++----------
 arch/x86/kernel/asm-offsets.c              |  1 +
 arch/x86/um/shared/sysdep/kernel-offsets.h |  2 ++
 kernel/bounds.c                            |  1 +
 scripts/mod/devicetable-offsets.c          |  1 +
 7 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/arch/um/include/asm/Kbuild b/arch/um/include/asm/Kbuild
index b6810db24ca4..1b9b82bbe322 100644
--- a/arch/um/include/asm/Kbuild
+++ b/arch/um/include/asm/Kbuild
@@ -5,7 +5,6 @@ generic-y += device.h
 generic-y += dma-mapping.h
 generic-y += emergency-restart.h
 generic-y += exec.h
-generic-y += extable.h
 generic-y += ftrace.h
 generic-y += hw_irq.h
 generic-y += irq_regs.h
diff --git a/arch/um/include/shared/common-offsets.h b/arch/um/include/shared/common-offsets.h
index 4e19103afd71..a6f77cb6aa7e 100644
--- a/arch/um/include/shared/common-offsets.h
+++ b/arch/um/include/shared/common-offsets.h
@@ -20,3 +20,4 @@ DEFINE(UM_KERN_GDT_ENTRY_TLS_ENTRIES, GDT_ENTRY_TLS_ENTRIES);
 DEFINE(UM_SECCOMP_ARCH_NATIVE, SECCOMP_ARCH_NATIVE);
 
 DEFINE(ALT_INSTR_SIZE, sizeof(struct alt_instr));
+DEFINE(EXTABLE_SIZE,   sizeof(struct exception_table_entry));
diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
index bd62bd87a841..0e8c611bc9e2 100644
--- a/arch/x86/include/asm/asm.h
+++ b/arch/x86/include/asm/asm.h
@@ -126,18 +126,21 @@ static __always_inline __pure void *rip_rel_ptr(void *p)
 
 #ifdef __KERNEL__
 
+#ifndef COMPILE_OFFSETS
+#include <asm/asm-offsets.h>
+#endif
+
 # include <asm/extable_fixup_types.h>
 
 /* Exception table entry */
 #ifdef __ASSEMBLER__
 
-# define _ASM_EXTABLE_TYPE(from, to, type)			\
-	.pushsection "__ex_table","a" ;				\
-	.balign 4 ;						\
-	ANNOTATE_DATA_SPECIAL ;					\
-	.long (from) - . ;					\
-	.long (to) - . ;					\
-	.long type ;						\
+# define _ASM_EXTABLE_TYPE(from, to, type)				\
+	.pushsection "__ex_table", "aM", @progbits, EXTABLE_SIZE ;	\
+	.balign 4 ;							\
+	.long (from) - . ;						\
+	.long (to) - . ;						\
+	.long type ;							\
 	.popsection
 
 # ifdef CONFIG_KPROBES
@@ -180,18 +183,18 @@ static __always_inline __pure void *rip_rel_ptr(void *p)
 	".purgem extable_type_reg\n"
 
 # define _ASM_EXTABLE_TYPE(from, to, type)			\
-	" .pushsection \"__ex_table\",\"a\"\n"			\
+	" .pushsection __ex_table, \"aM\", @progbits, "		\
+		       __stringify(EXTABLE_SIZE) "\n"		\
 	" .balign 4\n"						\
-	ANNOTATE_DATA_SPECIAL					\
 	" .long (" #from ") - .\n"				\
 	" .long (" #to ") - .\n"				\
 	" .long " __stringify(type) " \n"			\
 	" .popsection\n"
 
 # define _ASM_EXTABLE_TYPE_REG(from, to, type, reg)				\
-	" .pushsection \"__ex_table\",\"a\"\n"					\
+	" .pushsection __ex_table, \"aM\", @progbits, "				\
+		       __stringify(EXTABLE_SIZE) "\n"				\
 	" .balign 4\n"								\
-	ANNOTATE_DATA_SPECIAL							\
 	" .long (" #from ") - .\n"						\
 	" .long (" #to ") - .\n"						\
 	DEFINE_EXTABLE_TYPE_REG							\
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index db3bb5143329..25fcde525c68 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -126,4 +126,5 @@ static void __used common(void)
 
 	BLANK();
 	DEFINE(ALT_INSTR_SIZE,	sizeof(struct alt_instr));
+	DEFINE(EXTABLE_SIZE,	sizeof(struct exception_table_entry));
 }
diff --git a/arch/x86/um/shared/sysdep/kernel-offsets.h b/arch/x86/um/shared/sysdep/kernel-offsets.h
index 6fd1ed400399..8215a0200ddd 100644
--- a/arch/x86/um/shared/sysdep/kernel-offsets.h
+++ b/arch/x86/um/shared/sysdep/kernel-offsets.h
@@ -1,4 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+#define COMPILE_OFFSETS
 #include <linux/stddef.h>
 #include <linux/sched.h>
 #include <linux/elf.h>
@@ -7,6 +8,7 @@
 #include <linux/audit.h>
 #include <asm/mman.h>
 #include <asm/seccomp.h>
+#include <asm/extable.h>
 
 /* workaround for a warning with -Wmissing-prototypes */
 void foo(void);
diff --git a/kernel/bounds.c b/kernel/bounds.c
index 29b2cd00df2c..02b619eb6106 100644
--- a/kernel/bounds.c
+++ b/kernel/bounds.c
@@ -6,6 +6,7 @@
  */
 
 #define __GENERATING_BOUNDS_H
+#define COMPILE_OFFSETS
 /* Include headers that define the enum constants of interest */
 #include <linux/page-flags.h>
 #include <linux/mmzone.h>
diff --git a/scripts/mod/devicetable-offsets.c b/scripts/mod/devicetable-offsets.c
index d3d00e85edf7..ef2ffb68f69d 100644
--- a/scripts/mod/devicetable-offsets.c
+++ b/scripts/mod/devicetable-offsets.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
+#define COMPILE_OFFSETS
 #include <linux/kbuild.h>
 #include <linux/mod_devicetable.h>
 
-- 
2.51.1