[PATCH 1/4] x86/alternative: Remove ANNOTATE_DATA_SPECIAL usage

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

Instead of manually annotating each .altinstructions 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/shared/common-offsets.h | 2 ++
arch/x86/include/asm/alternative.h | 7 +++----
arch/x86/kernel/asm-offsets.c | 2 ++
3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/um/include/shared/common-offsets.h b/arch/um/include/shared/common-offsets.h
index 8ca66a1918c3..4e19103afd71 100644
--- a/arch/um/include/shared/common-offsets.h
+++ b/arch/um/include/shared/common-offsets.h
@@ -18,3 +18,5 @@ DEFINE(UM_NSEC_PER_USEC, NSEC_PER_USEC);
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));
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index b14c045679e1..df2c8705e17b 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -197,8 +197,8 @@ static inline int alternatives_text_reserved(void *start, void *end)
"773:\n"

#define ALTINSTR_ENTRY(ft_flags) \
- ".pushsection .altinstructions,\"a\"\n" \
- ANNOTATE_DATA_SPECIAL \
+ ".pushsection .altinstructions, \"aM\", @progbits, " \
+ __stringify(ALT_INSTR_SIZE) "\n" \
" .long 771b - .\n" /* label */ \
" .long 774f - .\n" /* new instruction */ \
" .4byte " __stringify(ft_flags) "\n" /* feature + flags */ \
@@ -339,7 +339,6 @@ void nop_func(void);
* instruction. See apply_alternatives().
*/
.macro altinstr_entry orig alt ft_flags orig_len alt_len
- ANNOTATE_DATA_SPECIAL
.long \orig - .
.long \alt - .
.4byte \ft_flags
@@ -363,7 +362,7 @@ void nop_func(void);
741: \
.skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90 ;\
742: \
- .pushsection .altinstructions,"a" ; \
+ .pushsection .altinstructions, "aM", @progbits, ALT_INSTR_SIZE ;\
altinstr_entry 740b,743f,flag,742b-740b,744f-743f ; \
.popsection ; \
.pushsection .altinstr_replacement,"ax" ; \
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index 32ba599a51f8..db3bb5143329 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -124,4 +124,6 @@ static void __used common(void)
OFFSET(ARIA_CTX_rounds, aria_ctx, rounds);
#endif

+ BLANK();
+ DEFINE(ALT_INSTR_SIZE, sizeof(struct alt_instr));
}
--
2.51.1