[tip: objtool/urgent] x86/alternative: Remove ANNOTATE_DATA_SPECIAL usage

["tip-bot2 for Josh Poimboeuf" <tip-bot2@linutronix.de>]

The following commit has been merged into the objtool/urgent branch of tip:

Commit-ID:     a818f28f017b23cfe830dd82e89b5aa6b0fea8e5
Gitweb:        https://git.kernel.org/tip/a818f28f017b23cfe830dd82e89b5aa6b0fea8e5
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Tue, 02 Dec 2025 09:59:36 -08:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 03 Dec 2025 16:53:19 +01:00

x86/alternative: Remove ANNOTATE_DATA_SPECIAL usage

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>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://patch.msgid.link/5ac04e6db5be6453dce8003a771ebb0c47b4cd7a.1764694625.git.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 8ca66a1..4e19103 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 b14c045..df2c870 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 32ba599..db3bb51 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));
 }