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From:   Alexey Dobriyan <adobriyan@gmail.com>
To:     x86@kernel.org
Cc:     tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        dave.hansen@linux.intel.com, hpa@zytor.com,
        linux-kernel@vger.kernel.org, adobriyan@gmail.com
Subject: [PATCH 3/5] x86/alternative: record .altinstructions section entity size
Date:   Fri, 11 Mar 2022 17:43:10 +0300
Message-Id: <20220311144312.88466-3-adobriyan@gmail.com>
In-Reply-To: <20220311144312.88466-1-adobriyan@gmail.com>
References: <20220311144312.88466-1-adobriyan@gmail.com>
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.altinstructions entry was 12 bytes in size, then it was 13 bytes,
now it is 12 again. It was 24 bytes on some distros as well.
Record this information as section sh_entsize value so that tools
which parse .altinstructions have easier time.

Signed-off-by: Alexey Dobriyan (CloudLinux) <adobriyan@gmail.com>
---
 arch/x86/include/asm/alternative.h | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 58eee6402832..cf7722a106b3 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -9,6 +9,8 @@
 #define ALTINSTR_FLAG_INV	(1 << 15)
 #define ALT_NOT(feat)		((feat) | ALTINSTR_FLAG_INV)
 
+#define sizeof_struct_alt_instr 12
+
 #ifndef __ASSEMBLY__
 
 #include <linux/stddef.h>
@@ -66,6 +68,7 @@ struct alt_instr {
 	u8  instrlen;		/* length of original instruction */
 	u8  replacementlen;	/* length of new instruction */
 } __packed;
+_Static_assert(sizeof(struct alt_instr) == sizeof_struct_alt_instr, "");
 
 /*
  * Debug flag that can be tested to see whether alternative
@@ -159,7 +162,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
 /* alternative assembly primitive: */
 #define ALTERNATIVE(oldinstr, newinstr, feature)			\
 	OLDINSTR(oldinstr, 1)						\
-	".pushsection .altinstructions,\"a\"\n"				\
+	".pushsection .altinstructions,\"aM\",@progbits," __stringify(sizeof_struct_alt_instr) "\n"\
 	ALTINSTR_ENTRY(feature, 1)					\
 	".popsection\n"							\
 	".pushsection .altinstr_replacement, \"ax\"\n"			\
@@ -168,7 +171,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
 
 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
 	OLDINSTR_2(oldinstr, 1, 2)					\
-	".pushsection .altinstructions,\"a\"\n"				\
+	".pushsection .altinstructions,\"aM\",@progbits," __stringify(sizeof_struct_alt_instr) "\n"\
 	ALTINSTR_ENTRY(feature1, 1)					\
 	ALTINSTR_ENTRY(feature2, 2)					\
 	".popsection\n"							\
@@ -184,7 +187,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
 
 #define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \
 	OLDINSTR_3(oldinsn, 1, 2, 3)						\
-	".pushsection .altinstructions,\"a\"\n"					\
+	".pushsection .altinstructions,\"aM\",@progbits," __stringify(sizeof_struct_alt_instr) "\n"\
 	ALTINSTR_ENTRY(feat1, 1)						\
 	ALTINSTR_ENTRY(feat2, 2)						\
 	ALTINSTR_ENTRY(feat3, 3)						\
@@ -331,7 +334,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	.skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
 142:
 
-	.pushsection .altinstructions,"a"
+	.pushsection .altinstructions,"aM",@progbits,sizeof_struct_alt_instr
 	altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f
 	.popsection
 
@@ -368,7 +371,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
 		(alt_max_short(new_len1, new_len2) - (old_len)),0x90
 142:
 
-	.pushsection .altinstructions,"a"
+	.pushsection .altinstructions,"aM",@progbits,sizeof_struct_alt_instr
 	altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f
 	altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f
 	.popsection
-- 
2.34.1