linux-kernel - [PATCH v3 43/64] x86/alternative: Define ELF section entry size for alternatives

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <e048e6afcb2022114ea908205f4e81b7a53eba48.1750980517.git.jpoimboe@kernel.org>
Date: Thu, 26 Jun 2025 16:55:30 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
	Petr Mladek <pmladek@...e.com>,
	Miroslav Benes <mbenes@...e.cz>,
	Joe Lawrence <joe.lawrence@...hat.com>,
	live-patching@...r.kernel.org,
	Song Liu <song@...nel.org>,
	laokz <laokz@...mail.com>,
	Jiri Kosina <jikos@...nel.org>,
	Marcos Paulo de Souza <mpdesouza@...e.com>,
	Weinan Liu <wnliu@...gle.com>,
	Fazla Mehrab <a.mehrab@...edance.com>,
	Chen Zhongjin <chenzhongjin@...wei.com>,
	Puranjay Mohan <puranjay@...nel.org>,
	Dylan Hatch <dylanbhatch@...gle.com>
Subject: [PATCH v3 43/64] x86/alternative: Define ELF section entry size for alternatives

In preparation for the objtool klp diff subcommand, define the entry
size for the .altinstructions section in its ELF header.  This will
allow tooling to extract individual entries.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 arch/um/include/shared/common-offsets.h    | 2 ++
 arch/x86/include/asm/alternative.h         | 5 +++--
 arch/x86/include/asm/asm.h                 | 4 ++++
 arch/x86/kernel/asm-offsets.c              | 2 ++
 arch/x86/um/shared/sysdep/kernel-offsets.h | 1 +
 kernel/bounds.c                            | 1 +
 scripts/mod/devicetable-offsets.c          | 1 +
 7 files changed, 14 insertions(+), 2 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 15bc07a5ebb3..eb24d9ba30d7 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -197,7 +197,8 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	"773:\n"
 
 #define ALTINSTR_ENTRY(ft_flags)					      \
-	".pushsection .altinstructions,\"a\"\n"				      \
+	".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 */ \
@@ -360,7 +361,7 @@ 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/include/asm/asm.h b/arch/x86/include/asm/asm.h
index f963848024a5..1f26f90a57ce 100644
--- a/arch/x86/include/asm/asm.h
+++ b/arch/x86/include/asm/asm.h
@@ -136,6 +136,10 @@ 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 */
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index 6259b474073b..b51625c3f64c 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -123,4 +123,6 @@ static void __used common(void)
 	OFFSET(ARIA_CTX_rounds, aria_ctx, rounds);
 #endif
 
+	BLANK();
+	DEFINE(ALT_INSTR_SIZE,	 sizeof(struct alt_instr));
 }
diff --git a/arch/x86/um/shared/sysdep/kernel-offsets.h b/arch/x86/um/shared/sysdep/kernel-offsets.h
index 6fd1ed400399..9f6d3d1a248c 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>
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>
 
-- 
2.49.0