linux-kernel - [PATCH 4/5] x86/alternative: make .altinstr

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Date:   Fri, 11 Mar 2022 17:43:11 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     x86@...nel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com,
        linux-kernel@...r.kernel.org, adobriyan@...il.com
Subject: [PATCH 4/5] x86/alternative: make .altinstr_replacement section non-executable

Instructions in .altinstr_replacement section aren't meant to be
executed by CPU directly, only after being copied to the real
instruction stream in .text/.init_text.

Signed-off-by: Alexey Dobriyan (CloudLinux) <adobriyan@...il.com>
---
 arch/x86/include/asm/alternative.h | 10 +++++-----
 tools/objtool/check.c              |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index cf7722a106b3..d754a18edc99 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -165,7 +165,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	".pushsection .altinstructions,\"aM\",@progbits," __stringify(sizeof_struct_alt_instr) "\n"\
 	ALTINSTR_ENTRY(feature, 1)					\
 	".popsection\n"							\
-	".pushsection .altinstr_replacement, \"ax\"\n"			\
+	".pushsection .altinstr_replacement, \"a\"\n"			\
 	ALTINSTR_REPLACEMENT(newinstr, 1)				\
 	".popsection\n"
 
@@ -175,7 +175,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	ALTINSTR_ENTRY(feature1, 1)					\
 	ALTINSTR_ENTRY(feature2, 2)					\
 	".popsection\n"							\
-	".pushsection .altinstr_replacement, \"ax\"\n"			\
+	".pushsection .altinstr_replacement, \"a\"\n"			\
 	ALTINSTR_REPLACEMENT(newinstr1, 1)				\
 	ALTINSTR_REPLACEMENT(newinstr2, 2)				\
 	".popsection\n"
@@ -192,7 +192,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	ALTINSTR_ENTRY(feat2, 2)						\
 	ALTINSTR_ENTRY(feat3, 3)						\
 	".popsection\n"								\
-	".pushsection .altinstr_replacement, \"ax\"\n"				\
+	".pushsection .altinstr_replacement, \"a\"\n"				\
 	ALTINSTR_REPLACEMENT(newinsn1, 1)					\
 	ALTINSTR_REPLACEMENT(newinsn2, 2)					\
 	ALTINSTR_REPLACEMENT(newinsn3, 3)					\
@@ -338,7 +338,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f
 	.popsection
 
-	.pushsection .altinstr_replacement,"ax"
+	.pushsection .altinstr_replacement,"a"
 143:
 	\newinstr
 144:
@@ -376,7 +376,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f
 	.popsection
 
-	.pushsection .altinstr_replacement,"ax"
+	.pushsection .altinstr_replacement,"a"
 143:
 	\newinstr1
 144:
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 7c33ec67c4a9..18c32035f41c 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -359,7 +359,7 @@ static int decode_instructions(struct objtool_file *file)
 
 	for_each_sec(file, sec) {
 
-		if (!(sec->sh.sh_flags & SHF_EXECINSTR))
+		if (!(sec->sh.sh_flags & SHF_EXECINSTR) && strcmp(sec->name, ".altinstr_replacement"))
 			continue;
 
 		if (strcmp(sec->name, ".altinstr_replacement") &&
-- 
2.34.1