[PATCH 2/4] x86/asm: Remove ANNOTATE_DATA_SPECIAL usage

Josh Poimboeuf
2025-11-26T06:07:36Z

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@kernel.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