[PATCH 00/14] objtool/arm64: Port klp-build to arm64

[PATCH 00/14] objtool/arm64: Port klp-build to arm64

[Josh Poimboeuf]

Port objtool and the klp-build tooling (for building livepatch modules)
to arm64.

Note this doesn't bring all the objtool bells and whistles to arm64, nor
any of the CFG reverse engineering.  This only adds the bare minimum
needed for 'objtool --checksum'.

And note that objtool still doesn't get enabled at all for normal arm64
kernel builds, so this doesn't affect any users other than those running
klp-build directly.

Josh Poimboeuf (14):
  objtool: Fix data alignment in elf_add_data()
  objtool: Fix ERROR_INSN() error message
  arm64: Annotate intra-function calls
  arm64: head: Move boot header to .head.data
  arm64: Fix EFI linking with -fdata-sections
  crypto: arm64: Move data to .rodata
  objtool: Extricate checksum calculation from validate_branch()
  objtool: Allow setting --mnop without --mcount
  kbuild: Only run objtool if there is at least one command
  objtool: Ignore jumps to the end of the function for non-CFG arches
  objtool: Allow empty alternatives
  objtool: Reuse consecutive string references
  objtool: Introduce objtool for arm64
  klp-build: Support cross-compilation

 arch/arm64/Kconfig                            |   2 +
 arch/arm64/kernel/entry.S                     |   2 +
 arch/arm64/kernel/head.S                      |   2 +-
 arch/arm64/kernel/proton-pack.c               |  12 +-
 arch/arm64/kernel/vmlinux.lds.S               |   2 +-
 arch/x86/boot/startup/Makefile                |   2 +-
 include/asm-generic/vmlinux.lds.h             |   2 +-
 include/linux/init.h                          |   1 +
 lib/crypto/arm64/sha2-armv8.pl                |  11 +-
 scripts/Makefile.build                        |   4 +-
 scripts/Makefile.lib                          |  46 +++----
 scripts/Makefile.vmlinux_o                    |  15 +--
 scripts/livepatch/klp-build                   |  11 +-
 tools/objtool/Makefile                        |   4 +
 tools/objtool/arch/arm64/Build                |   2 +
 tools/objtool/arch/arm64/decode.c             | 116 ++++++++++++++++++
 .../arch/arm64/include/arch/cfi_regs.h        |  11 ++
 tools/objtool/arch/arm64/include/arch/elf.h   |  13 ++
 .../objtool/arch/arm64/include/arch/special.h |  21 ++++
 tools/objtool/arch/arm64/special.c            |  21 ++++
 tools/objtool/builtin-check.c                 |   5 -
 tools/objtool/check.c                         |  83 +++++++++----
 tools/objtool/elf.c                           |  11 +-
 tools/objtool/include/objtool/checksum.h      |   6 +-
 tools/objtool/include/objtool/warn.h          |   2 +-
 25 files changed, 323 insertions(+), 84 deletions(-)
 create mode 100644 tools/objtool/arch/arm64/Build
 create mode 100644 tools/objtool/arch/arm64/decode.c
 create mode 100644 tools/objtool/arch/arm64/include/arch/cfi_regs.h
 create mode 100644 tools/objtool/arch/arm64/include/arch/elf.h
 create mode 100644 tools/objtool/arch/arm64/include/arch/special.h
 create mode 100644 tools/objtool/arch/arm64/special.c

-- 
2.53.0

[PATCH 01/14] objtool: Fix data alignment in elf_add_data()

[Josh Poimboeuf]

Any data added to a section needs to be aligned in accordance with the
section's sh_addralign value.  Particularly strings added to a .str1.8
section.  Otherwise you may get some funky strings.

Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 tools/objtool/elf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 2c02c7b49265..3da90686350d 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -1375,7 +1375,7 @@ void *elf_add_data(struct elf *elf, struct section *sec, const void *data, size_
 		memcpy(sec->data->d_buf, data, size);
 
 	sec->data->d_size = size;
-	sec->data->d_align = 1;
+	sec->data->d_align = sec->sh.sh_addralign;
 
 	offset = ALIGN(sec->sh.sh_size, sec->sh.sh_addralign);
 	sec->sh.sh_size = offset + size;
-- 
2.53.0

[tip: objtool/urgent] objtool: Fix data alignment in elf_add_data()

[tip-bot2 for Josh Poimboeuf]

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

Commit-ID:     356e4b2f5b80f757965f3f4d0219c81fca91b6f2
Gitweb:        https://git.kernel.org/tip/356e4b2f5b80f757965f3f4d0219c81fca91b6f2
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Wed, 04 Mar 2026 19:31:20 -08:00
Committer:     Josh Poimboeuf <jpoimboe@kernel.org>
CommitterDate: Fri, 06 Mar 2026 07:53:36 -08:00

objtool: Fix data alignment in elf_add_data()

Any data added to a section needs to be aligned in accordance with the
section's sh_addralign value.  Particularly strings added to a .str1.8
section.  Otherwise you may get some funky strings.

Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Link: https://patch.msgid.link/d962fc0ca24fa0825cca8dad71932dccdd9312a9.1772681234.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 tools/objtool/elf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 2c02c7b..3da9068 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -1375,7 +1375,7 @@ void *elf_add_data(struct elf *elf, struct section *sec, const void *data, size_
 		memcpy(sec->data->d_buf, data, size);
 
 	sec->data->d_size = size;
-	sec->data->d_align = 1;
+	sec->data->d_align = sec->sh.sh_addralign;
 
 	offset = ALIGN(sec->sh.sh_size, sec->sh.sh_addralign);
 	sec->sh.sh_size = offset + size;

[PATCH 02/14] objtool: Fix ERROR_INSN() error message

[Josh Poimboeuf]

Confusingly, ERROR_INSN() shows "warning:" instead of "error:".  Fix that.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 tools/objtool/include/objtool/warn.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/include/objtool/warn.h b/tools/objtool/include/objtool/warn.h
index 2b27b54096b8..fa8b7d292e83 100644
--- a/tools/objtool/include/objtool/warn.h
+++ b/tools/objtool/include/objtool/warn.h
@@ -107,7 +107,7 @@ static inline char *offstr(struct section *sec, unsigned long offset)
 #define ERROR_ELF(format, ...) __WARN_ELF(ERROR_STR, format, ##__VA_ARGS__)
 #define ERROR_GLIBC(format, ...) __WARN_GLIBC(ERROR_STR, format, ##__VA_ARGS__)
 #define ERROR_FUNC(sec, offset, format, ...) __WARN_FUNC(ERROR_STR, sec, offset, format, ##__VA_ARGS__)
-#define ERROR_INSN(insn, format, ...) WARN_FUNC(insn->sec, insn->offset, format, ##__VA_ARGS__)
+#define ERROR_INSN(insn, format, ...) ERROR_FUNC(insn->sec, insn->offset, format, ##__VA_ARGS__)
 
 extern bool debug;
 extern int indent;
-- 
2.53.0

[tip: objtool/urgent] objtool: Fix ERROR_INSN() error message

[tip-bot2 for Josh Poimboeuf]

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

Commit-ID:     1fd1dc41724319406b0aff221a352a400b0ddfc5
Gitweb:        https://git.kernel.org/tip/1fd1dc41724319406b0aff221a352a400b0ddfc5
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Wed, 04 Mar 2026 19:31:21 -08:00
Committer:     Josh Poimboeuf <jpoimboe@kernel.org>
CommitterDate: Fri, 06 Mar 2026 07:53:37 -08:00

objtool: Fix ERROR_INSN() error message

Confusingly, ERROR_INSN() shows "warning:" instead of "error:".  Fix that.

Link: https://patch.msgid.link/c4fe793bb3d23fac2c636b2511059af1158410e2.1772681234.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 tools/objtool/include/objtool/warn.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/include/objtool/warn.h b/tools/objtool/include/objtool/warn.h
index 2b27b54..fa8b7d2 100644
--- a/tools/objtool/include/objtool/warn.h
+++ b/tools/objtool/include/objtool/warn.h
@@ -107,7 +107,7 @@ static inline char *offstr(struct section *sec, unsigned long offset)
 #define ERROR_ELF(format, ...) __WARN_ELF(ERROR_STR, format, ##__VA_ARGS__)
 #define ERROR_GLIBC(format, ...) __WARN_GLIBC(ERROR_STR, format, ##__VA_ARGS__)
 #define ERROR_FUNC(sec, offset, format, ...) __WARN_FUNC(ERROR_STR, sec, offset, format, ##__VA_ARGS__)
-#define ERROR_INSN(insn, format, ...) WARN_FUNC(insn->sec, insn->offset, format, ##__VA_ARGS__)
+#define ERROR_INSN(insn, format, ...) ERROR_FUNC(insn->sec, insn->offset, format, ##__VA_ARGS__)
 
 extern bool debug;
 extern int indent;

[PATCH 03/14] arm64: Annotate intra-function calls

[Josh Poimboeuf]

In preparation for enabling objtool on arm64, annotate intra-function
calls.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/arm64/kernel/entry.S       |  2 ++
 arch/arm64/kernel/proton-pack.c | 12 +++++++-----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index f8018b5c1f9a..cf808bb2abc0 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -10,6 +10,7 @@
 #include <linux/arm-smccc.h>
 #include <linux/init.h>
 #include <linux/linkage.h>
+#include <linux/annotate.h>
 
 #include <asm/alternative.h>
 #include <asm/assembler.h>
@@ -707,6 +708,7 @@ alternative_else_nop_endif
 	 * entry onto the return stack and using a RET instruction to
 	 * enter the full-fat kernel vectors.
 	 */
+	ANNOTATE_INTRA_FUNCTION_CALL
 	bl	2f
 	b	.
 2:
diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c
index b3801f532b10..b63887a1b823 100644
--- a/arch/arm64/kernel/proton-pack.c
+++ b/arch/arm64/kernel/proton-pack.c
@@ -24,6 +24,7 @@
 #include <linux/nospec.h>
 #include <linux/prctl.h>
 #include <linux/sched/task_stack.h>
+#include <linux/annotate.h>
 
 #include <asm/debug-monitors.h>
 #include <asm/insn.h>
@@ -245,11 +246,12 @@ static noinstr void qcom_link_stack_sanitisation(void)
 {
 	u64 tmp;
 
-	asm volatile("mov	%0, x30		\n"
-		     ".rept	16		\n"
-		     "bl	. + 4		\n"
-		     ".endr			\n"
-		     "mov	x30, %0		\n"
+	asm volatile("mov	%0, x30			\n"
+		     ".rept	16			\n"
+		     ANNOTATE_INTRA_FUNCTION_CALL "	\n"
+		     "bl	. + 4			\n"
+		     ".endr				\n"
+		     "mov	x30, %0			\n"
 		     : "=&r" (tmp));
 }
 
-- 
2.53.0

Re: [PATCH 03/14] arm64: Annotate intra-function calls

[Song Liu]

On Wed, Mar 4, 2026 at 7:31 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> In preparation for enabling objtool on arm64, annotate intra-function
> calls.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Acked-by: Song Liu <song@kernel.org>

[PATCH 04/14] arm64: head: Move boot header to .head.data

[Josh Poimboeuf]

The arm64 boot header is mostly data.  Move it to a data section to
prevent objtool and other tools from trying to disassemble it.  The
final linked result is the same.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/arm64/kernel/head.S          | 2 +-
 include/asm-generic/vmlinux.lds.h | 2 +-
 include/linux/init.h              | 1 +
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 87a822e5c4ca..0681c6e50859 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -54,7 +54,7 @@
  * that are useful before the MMU is enabled. The allocations are described
  * in the entry routines.
  */
-	__HEAD
+	__HEADDATA
 	/*
 	 * DO NOT MODIFY. Image header expected by Linux boot-loaders.
 	 */
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index eeb070f330bd..51a0e5974f41 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -663,7 +663,7 @@
 		__static_call_text_end = .;
 
 /* Section used for early init (in .S files) */
-#define HEAD_TEXT  KEEP(*(.head.text))
+#define HEAD_TEXT  KEEP(*(.head.data .head.text))
 
 #define HEAD_TEXT_SECTION							\
 	.head.text : AT(ADDR(.head.text) - LOAD_OFFSET) {		\
diff --git a/include/linux/init.h b/include/linux/init.h
index 40331923b9f4..91e16f3205e2 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -90,6 +90,7 @@
 
 /* For assembly routines */
 #define __HEAD		.section	".head.text","ax"
+#define __HEADDATA	.section	".head.data","aw"
 #define __INIT		.section	".init.text","ax"
 #define __FINIT		.previous
 
-- 
2.53.0

Re: [PATCH 04/14] arm64: head: Move boot header to .head.data

[Song Liu]

On Wed, Mar 4, 2026 at 7:31 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> The arm64 boot header is mostly data.  Move it to a data section to
> prevent objtool and other tools from trying to disassemble it.  The
> final linked result is the same.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Acked-by: Song Liu <song@kernel.org>

[PATCH 05/14] arm64: Fix EFI linking with -fdata-sections

[Josh Poimboeuf]

When building with func-fdata-sections, the .init.bss section gets split
up into a bunch of .init.bss.<var> sections.  Make sure they get linked
into .init.data.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/arm64/kernel/vmlinux.lds.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index ad6133b89e7a..1f5e4f996a21 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -269,7 +269,7 @@ SECTIONS
 		INIT_CALLS
 		CON_INITCALL
 		INIT_RAM_FS
-		*(.init.altinstructions .init.bss)	/* from the EFI stub */
+		*(.init.altinstructions .init.bss .init.bss.*)	/* from the EFI stub */
 	}
 	.exit.data : {
 		EXIT_DATA
-- 
2.53.0

Re: [PATCH 05/14] arm64: Fix EFI linking with -fdata-sections

[Song Liu]

On Wed, Mar 4, 2026 at 7:31 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> When building with func-fdata-sections, the .init.bss section gets split
> up into a bunch of .init.bss.<var> sections.  Make sure they get linked
> into .init.data.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Acked-by: Song Liu <song@kernel.org>

[PATCH 06/14] crypto: arm64: Move data to .rodata

[Josh Poimboeuf]

Data embedded in .text pollutes i-cache and confuses objtool and other
tools that try to disassemble it.  Move it to .rodata.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 lib/crypto/arm64/sha2-armv8.pl | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/lib/crypto/arm64/sha2-armv8.pl b/lib/crypto/arm64/sha2-armv8.pl
index 35ec9ae99fe1..8cd86768bf5c 100644
--- a/lib/crypto/arm64/sha2-armv8.pl
+++ b/lib/crypto/arm64/sha2-armv8.pl
@@ -237,7 +237,8 @@ $code.=<<___;
 	ldp	$E,$F,[$ctx,#4*$SZ]
 	add	$num,$inp,$num,lsl#`log(16*$SZ)/log(2)`	// end of input
 	ldp	$G,$H,[$ctx,#6*$SZ]
-	adr	$Ktbl,.LK$BITS
+	adrp	$Ktbl,.LK$BITS
+	add	$Ktbl,$Ktbl,:lo12:.LK$BITS
 	stp	$ctx,$num,[x29,#96]
 
 .Loop:
@@ -286,6 +287,7 @@ $code.=<<___;
 	ret
 .size	$func,.-$func
 
+.pushsection .rodata
 .align	6
 .type	.LK$BITS,%object
 .LK$BITS:
@@ -365,6 +367,7 @@ $code.=<<___;
 #endif
 .asciz	"SHA$BITS block transform for ARMv8, CRYPTOGAMS by <appro\@openssl.org>"
 .align	2
+.popsection
 ___
 
 if ($SZ==4) {
@@ -385,7 +388,8 @@ sha256_block_armv8:
 	add		x29,sp,#0
 
 	ld1.32		{$ABCD,$EFGH},[$ctx]
-	adr		$Ktbl,.LK256
+	adrp		$Ktbl,.LK256
+	add		$Ktbl,$Ktbl,:lo12:.LK256
 
 .Loop_hw:
 	ld1		{@MSG[0]-@MSG[3]},[$inp],#64
@@ -648,7 +652,8 @@ sha256_block_neon:
 	mov	x29, sp
 	sub	sp,sp,#16*4
 
-	adr	$Ktbl,.LK256
+	adrp	$Ktbl,.LK256
+	add	$Ktbl,$Ktbl,:lo12:.LK256
 	add	$num,$inp,$num,lsl#6	// len to point at the end of inp
 
 	ld1.8	{@X[0]},[$inp], #16
-- 
2.53.0

[PATCH 07/14] objtool: Extricate checksum calculation from validate_branch()

[Josh Poimboeuf]

In preparation for porting the checksum code to other arches, make its
functionality independent from validate_branch().

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 tools/objtool/check.c                    | 71 +++++++++++++++++-------
 tools/objtool/include/objtool/checksum.h |  6 +-
 2 files changed, 53 insertions(+), 24 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index a30379e4ff97..f73cf1382e5c 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2633,8 +2633,7 @@ static bool validate_branch_enabled(void)
 {
 	return opts.stackval ||
 	       opts.orc ||
-	       opts.uaccess ||
-	       opts.checksum;
+	       opts.uaccess;
 }
 
 static int decode_sections(struct objtool_file *file)
@@ -3649,6 +3648,7 @@ static bool skip_alt_group(struct instruction *insn)
 	return alt_insn->type == INSN_CLAC || alt_insn->type == INSN_STAC;
 }
 
+#ifdef BUILD_KLP
 static int checksum_debug_init(struct objtool_file *file)
 {
 	char *dup, *s;
@@ -3691,9 +3691,30 @@ static void checksum_update_insn(struct objtool_file *file, struct symbol *func,
 				 struct instruction *insn)
 {
 	struct reloc *reloc = insn_reloc(file, insn);
+	struct alternative *alt;
 	unsigned long offset;
 	struct symbol *sym;
 
+	for (alt = insn->alts; alt; alt = alt->next) {
+		struct alt_group *alt_group = alt->insn->alt_group;
+
+		checksum_update(func, insn, &alt->type, sizeof(alt->type));
+
+		if (alt_group && alt_group->orig_group) {
+			struct instruction *alt_insn;
+
+			checksum_update(func, insn, &alt_group->feature, sizeof(alt_group->feature));
+
+			for (alt_insn = alt->insn; alt_insn; alt_insn = next_insn_same_sec(file, alt_insn)) {
+				checksum_update_insn(file, func, alt_insn);
+				if (alt_insn == alt_group->last_insn)
+					break;
+			}
+		} else {
+			checksum_update(func, insn, &alt->insn->offset, sizeof(alt->insn->offset));
+		}
+	}
+
 	if (insn->fake)
 		return;
 
@@ -3702,9 +3723,11 @@ static void checksum_update_insn(struct objtool_file *file, struct symbol *func,
 	if (!reloc) {
 		struct symbol *call_dest = insn_call_dest(insn);
 
-		if (call_dest)
+		if (call_dest) {
+			/* intra-TU call without reloc */
 			checksum_update(func, insn, call_dest->demangled_name,
 					strlen(call_dest->demangled_name));
+		}
 		return;
 	}
 
@@ -3731,6 +3754,29 @@ static void checksum_update_insn(struct objtool_file *file, struct symbol *func,
 	checksum_update(func, insn, &offset, sizeof(offset));
 }
 
+static int calculate_checksums(struct objtool_file *file)
+{
+	struct instruction *insn;
+	struct symbol *func;
+
+	if (checksum_debug_init(file))
+		return -1;
+
+	for_each_sym(file->elf, func) {
+		if (!is_func_sym(func))
+			continue;
+
+		checksum_init(func);
+
+		func_for_each_insn(file, func, insn)
+			checksum_update_insn(file, func, insn);
+
+		checksum_finish(func);
+	}
+	return 0;
+}
+#endif /* BUILD_KLP */
+
 static int validate_branch(struct objtool_file *file, struct symbol *func,
 			   struct instruction *insn, struct insn_state state);
 static int do_validate_branch(struct objtool_file *file, struct symbol *func,
@@ -4012,9 +4058,6 @@ static int do_validate_branch(struct objtool_file *file, struct symbol *func,
 		insn->trace = 0;
 		next_insn = next_insn_to_validate(file, insn);
 
-		if (opts.checksum && func && insn->sec)
-			checksum_update_insn(file, func, insn);
-
 		if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
 			/* Ignore KCFI type preambles, which always fall through */
 			if (is_prefix_func(func))
@@ -4080,9 +4123,6 @@ static int validate_unwind_hint(struct objtool_file *file,
 		struct symbol *func = insn_func(insn);
 		int ret;
 
-		if (opts.checksum)
-			checksum_init(func);
-
 		ret = validate_branch(file, func, insn, *state);
 		if (ret)
 			BT_INSN(insn, "<=== (hint)");
@@ -4525,9 +4565,6 @@ static int validate_symbol(struct objtool_file *file, struct section *sec,
 
 	func = insn_func(insn);
 
-	if (opts.checksum)
-		checksum_init(func);
-
 	if (opts.trace && !fnmatch(opts.trace, sym->name, 0)) {
 		trace_enable();
 		TRACE("%s: validation begin\n", sym->name);
@@ -4540,9 +4577,6 @@ static int validate_symbol(struct objtool_file *file, struct section *sec,
 	TRACE("%s: validation %s\n\n", sym->name, ret ? "failed" : "end");
 	trace_disable();
 
-	if (opts.checksum)
-		checksum_finish(func);
-
 	return ret;
 }
 
@@ -4997,10 +5031,6 @@ int check(struct objtool_file *file)
 	cfi_hash_add(&init_cfi);
 	cfi_hash_add(&func_cfi);
 
-	ret = checksum_debug_init(file);
-	if (ret)
-		goto out;
-
 	ret = decode_sections(file);
 	if (ret)
 		goto out;
@@ -5091,6 +5121,9 @@ int check(struct objtool_file *file)
 		warnings += check_abs_references(file);
 
 	if (opts.checksum) {
+		ret = calculate_checksums(file);
+		if (ret)
+			goto out;
 		ret = create_sym_checksum_section(file);
 		if (ret)
 			goto out;
diff --git a/tools/objtool/include/objtool/checksum.h b/tools/objtool/include/objtool/checksum.h
index 7fe21608722a..36a17688c716 100644
--- a/tools/objtool/include/objtool/checksum.h
+++ b/tools/objtool/include/objtool/checksum.h
@@ -32,11 +32,7 @@ static inline void checksum_finish(struct symbol *func)
 
 #else /* !BUILD_KLP */
 
-static inline void checksum_init(struct symbol *func) {}
-static inline void checksum_update(struct symbol *func,
-				   struct instruction *insn,
-				   const void *data, size_t size) {}
-static inline void checksum_finish(struct symbol *func) {}
+static inline int calculate_checksums(struct objtool_file *file) { return -ENOSYS; }
 
 #endif /* !BUILD_KLP */
 
-- 
2.53.0

Re: [PATCH 07/14] objtool: Extricate checksum calculation from validate_branch()

[Miroslav Benes]

Hi,

> @@ -3691,9 +3691,30 @@ static void checksum_update_insn(struct objtool_file *file, struct symbol *func,
>  				 struct instruction *insn)
>  {
>  	struct reloc *reloc = insn_reloc(file, insn);
> +	struct alternative *alt;
>  	unsigned long offset;
>  	struct symbol *sym;
>  
> +	for (alt = insn->alts; alt; alt = alt->next) {
> +		struct alt_group *alt_group = alt->insn->alt_group;
> +
> +		checksum_update(func, insn, &alt->type, sizeof(alt->type));
> +
> +		if (alt_group && alt_group->orig_group) {
> +			struct instruction *alt_insn;
> +
> +			checksum_update(func, insn, &alt_group->feature, sizeof(alt_group->feature));
> +
> +			for (alt_insn = alt->insn; alt_insn; alt_insn = next_insn_same_sec(file, alt_insn)) {
> +				checksum_update_insn(file, func, alt_insn);
> +				if (alt_insn == alt_group->last_insn)
> +					break;
> +			}
> +		} else {
> +			checksum_update(func, insn, &alt->insn->offset, sizeof(alt->insn->offset));
> +		}
> +	}
> +

does this hunk belong to the patch? Unless I am missing something, it 
might be worth a separate one.

Miroslav

Re: [PATCH 07/14] objtool: Extricate checksum calculation from validate_branch()

[Josh Poimboeuf]

On Tue, Mar 10, 2026 at 11:47:41AM +0100, Miroslav Benes wrote:
> Hi,
> 
> > @@ -3691,9 +3691,30 @@ static void checksum_update_insn(struct objtool_file *file, struct symbol *func,
> >  				 struct instruction *insn)
> >  {
> >  	struct reloc *reloc = insn_reloc(file, insn);
> > +	struct alternative *alt;
> >  	unsigned long offset;
> >  	struct symbol *sym;
> >  
> > +	for (alt = insn->alts; alt; alt = alt->next) {
> > +		struct alt_group *alt_group = alt->insn->alt_group;
> > +
> > +		checksum_update(func, insn, &alt->type, sizeof(alt->type));
> > +
> > +		if (alt_group && alt_group->orig_group) {
> > +			struct instruction *alt_insn;
> > +
> > +			checksum_update(func, insn, &alt_group->feature, sizeof(alt_group->feature));
> > +
> > +			for (alt_insn = alt->insn; alt_insn; alt_insn = next_insn_same_sec(file, alt_insn)) {
> > +				checksum_update_insn(file, func, alt_insn);
> > +				if (alt_insn == alt_group->last_insn)
> > +					break;
> > +			}
> > +		} else {
> > +			checksum_update(func, insn, &alt->insn->offset, sizeof(alt->insn->offset));
> > +		}
> > +	}
> > +
> 
> does this hunk belong to the patch? Unless I am missing something, it 
> might be worth a separate one.

It belongs, but I should have clarified that in the patch description.

This hunk wasn't needed before because validate_branch() already
iterates all the alternatives, so it was calling checksum_update_insn()
for every instruction in the function, including the alternatives.

Now that it's no longer called by validate_branch(),
checksum_update_insn() has to manually iterate the alternatives.

-- 
Josh

Re: [PATCH 07/14] objtool: Extricate checksum calculation from validate_branch()

[Miroslav Benes]

On Tue, 10 Mar 2026, Josh Poimboeuf wrote:

> On Tue, Mar 10, 2026 at 11:47:41AM +0100, Miroslav Benes wrote:
> > Hi,
> > 
> > > @@ -3691,9 +3691,30 @@ static void checksum_update_insn(struct objtool_file *file, struct symbol *func,
> > >  				 struct instruction *insn)
> > >  {
> > >  	struct reloc *reloc = insn_reloc(file, insn);
> > > +	struct alternative *alt;
> > >  	unsigned long offset;
> > >  	struct symbol *sym;
> > >  
> > > +	for (alt = insn->alts; alt; alt = alt->next) {
> > > +		struct alt_group *alt_group = alt->insn->alt_group;
> > > +
> > > +		checksum_update(func, insn, &alt->type, sizeof(alt->type));
> > > +
> > > +		if (alt_group && alt_group->orig_group) {
> > > +			struct instruction *alt_insn;
> > > +
> > > +			checksum_update(func, insn, &alt_group->feature, sizeof(alt_group->feature));
> > > +
> > > +			for (alt_insn = alt->insn; alt_insn; alt_insn = next_insn_same_sec(file, alt_insn)) {
> > > +				checksum_update_insn(file, func, alt_insn);
> > > +				if (alt_insn == alt_group->last_insn)
> > > +					break;
> > > +			}
> > > +		} else {
> > > +			checksum_update(func, insn, &alt->insn->offset, sizeof(alt->insn->offset));
> > > +		}
> > > +	}
> > > +
> > 
> > does this hunk belong to the patch? Unless I am missing something, it 
> > might be worth a separate one.
> 
> It belongs, but I should have clarified that in the patch description.
> 
> This hunk wasn't needed before because validate_branch() already
> iterates all the alternatives, so it was calling checksum_update_insn()
> for every instruction in the function, including the alternatives.
> 
> Now that it's no longer called by validate_branch(),
> checksum_update_insn() has to manually iterate the alternatives.

After writing the email I had a suspicion it must have been something like 
above but failed to find it. Now I see that next_insn_to_validate() called 
in do_validate_branch() handles exactly that. Thanks for the pointer. The 
patch looks good to me then (and the rest as well as far as I can judge).

I must admit that objtool has gotten so complex that I have a hard time to 
track everything in the code :).

Regards
Miroslav

Re: [PATCH 07/14] objtool: Extricate checksum calculation from validate_branch()

[Josh Poimboeuf]

On Wed, Mar 11, 2026 at 09:24:22AM +0100, Miroslav Benes wrote:
> On Tue, 10 Mar 2026, Josh Poimboeuf wrote:
> 
> > On Tue, Mar 10, 2026 at 11:47:41AM +0100, Miroslav Benes wrote:
> > > Hi,
> > > 
> > > > @@ -3691,9 +3691,30 @@ static void checksum_update_insn(struct objtool_file *file, struct symbol *func,
> > > >  				 struct instruction *insn)
> > > >  {
> > > >  	struct reloc *reloc = insn_reloc(file, insn);
> > > > +	struct alternative *alt;
> > > >  	unsigned long offset;
> > > >  	struct symbol *sym;
> > > >  
> > > > +	for (alt = insn->alts; alt; alt = alt->next) {
> > > > +		struct alt_group *alt_group = alt->insn->alt_group;
> > > > +
> > > > +		checksum_update(func, insn, &alt->type, sizeof(alt->type));
> > > > +
> > > > +		if (alt_group && alt_group->orig_group) {
> > > > +			struct instruction *alt_insn;
> > > > +
> > > > +			checksum_update(func, insn, &alt_group->feature, sizeof(alt_group->feature));
> > > > +
> > > > +			for (alt_insn = alt->insn; alt_insn; alt_insn = next_insn_same_sec(file, alt_insn)) {
> > > > +				checksum_update_insn(file, func, alt_insn);
> > > > +				if (alt_insn == alt_group->last_insn)
> > > > +					break;
> > > > +			}
> > > > +		} else {
> > > > +			checksum_update(func, insn, &alt->insn->offset, sizeof(alt->insn->offset));
> > > > +		}
> > > > +	}
> > > > +
> > > 
> > > does this hunk belong to the patch? Unless I am missing something, it 
> > > might be worth a separate one.
> > 
> > It belongs, but I should have clarified that in the patch description.
> > 
> > This hunk wasn't needed before because validate_branch() already
> > iterates all the alternatives, so it was calling checksum_update_insn()
> > for every instruction in the function, including the alternatives.
> > 
> > Now that it's no longer called by validate_branch(),
> > checksum_update_insn() has to manually iterate the alternatives.
> 
> After writing the email I had a suspicion it must have been something like 
> above but failed to find it. Now I see that next_insn_to_validate() called 
> in do_validate_branch() handles exactly that. Thanks for the pointer. The 
> patch looks good to me then (and the rest as well as far as I can judge).

Actually, next_insn_to_validate() helps with an edge case for directing
code flow from the end of an alternative back to the original code.

The code which traverses the alternatives is in validate_insn():

	if (insn->alts) {
		for (alt = insn->alts; alt; alt = alt->next) {
			TRACE_ALT_BEGIN(insn, alt, alt_name);
			ret = validate_branch(file, func, alt->insn, *statep);
			TRACE_ALT_END(insn, alt, alt_name);
			if (ret) {
				BT_INSN(insn, "(alt)");
				return ret;
			}
		}
		TRACE_ALT_INFO_NOADDR(insn, "/ ", "DEFAULT");
	}

> I must admit that objtool has gotten so complex that I have a hard time to 
> track everything in the code :).

The code hasn't changed *too* much, it's just that validate_branch() got
split up more when the tracing code went in, so things are organized a
bit differently.  Most of that code is now in validate_insn().

-- 
Josh

[PATCH 08/14] objtool: Allow setting --mnop without --mcount

[Josh Poimboeuf]

Instead of returning an error for --mnop without --mcount, just silently
ignore it.  This will help simplify kbuild's handling of objtool args.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 tools/objtool/builtin-check.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index b780df513715..f528a58aca74 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -145,11 +145,6 @@ int cmd_parse_options(int argc, const char **argv, const char * const usage[])
 
 static bool opts_valid(void)
 {
-	if (opts.mnop && !opts.mcount) {
-		ERROR("--mnop requires --mcount");
-		return false;
-	}
-
 	if (opts.noinstr && !opts.link) {
 		ERROR("--noinstr requires --link");
 		return false;
-- 
2.53.0

Re: [PATCH 08/14] objtool: Allow setting --mnop without --mcount

[Song Liu]

On Wed, Mar 4, 2026 at 7:31 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> Instead of returning an error for --mnop without --mcount, just silently
> ignore it.  This will help simplify kbuild's handling of objtool args.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Acked-by: Song Liu <song@kernel.org>

[PATCH 09/14] kbuild: Only run objtool if there is at least one command

[Josh Poimboeuf]

Split the objtool args into commands and options, such that if no
commands have been enabled, objtool doesn't run.

This is in preparation in enabling objtool and klp-build for arm64.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/boot/startup/Makefile |  2 +-
 scripts/Makefile.build         |  4 +--
 scripts/Makefile.lib           | 46 ++++++++++++++++++----------------
 scripts/Makefile.vmlinux_o     | 15 ++++-------
 4 files changed, 33 insertions(+), 34 deletions(-)

diff --git a/arch/x86/boot/startup/Makefile b/arch/x86/boot/startup/Makefile
index 5e499cfb29b5..a08297829fc6 100644
--- a/arch/x86/boot/startup/Makefile
+++ b/arch/x86/boot/startup/Makefile
@@ -36,7 +36,7 @@ $(patsubst %.o,$(obj)/%.o,$(lib-y)): OBJECT_FILES_NON_STANDARD := y
 # relocations, even if other objtool actions are being deferred.
 #
 $(pi-objs): objtool-enabled	= 1
-$(pi-objs): objtool-args	= $(if $(delay-objtool),--dry-run,$(objtool-args-y)) --noabs
+$(pi-objs): objtool-args	= $(if $(delay-objtool),--dry-run,$(objtool-cmds-y) $(objtool-opts-y)) --noabs
 
 #
 # Confine the startup code by prefixing all symbols with __pi_ (for position
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 32e209bc7985..d2d0776df947 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -277,7 +277,7 @@ endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
 is-standard-object = $(if $(filter-out y%, $(OBJECT_FILES_NON_STANDARD_$(target-stem).o)$(OBJECT_FILES_NON_STANDARD)n),$(is-kernel-object))
 
 ifdef CONFIG_OBJTOOL
-$(obj)/%.o: private objtool-enabled = $(if $(is-standard-object),$(if $(delay-objtool),$(is-single-obj-m),y))
+$(obj)/%.o: private objtool-enabled = $(if $(is-standard-object),$(if $(objtool-cmds-y),$(if $(delay-objtool),$(is-single-obj-m),y)))
 endif
 
 ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
@@ -499,7 +499,7 @@ define rule_ld_multi_m
 	$(call cmd,gen_objtooldep)
 endef
 
-$(multi-obj-m): private objtool-enabled := $(delay-objtool)
+$(multi-obj-m): private objtool-enabled := $(if $(objtool-cmds-y),$(delay-objtool))
 $(multi-obj-m): private part-of-module := y
 $(multi-obj-m): %.o: %.mod FORCE
 	$(call if_changed_rule,ld_multi_m)
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 0718e39cedda..40a462581666 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -183,27 +183,31 @@ ifdef CONFIG_OBJTOOL
 
 objtool := $(objtree)/tools/objtool/objtool
 
-objtool-args-$(CONFIG_HAVE_JUMP_LABEL_HACK)		+= --hacks=jump_label
-objtool-args-$(CONFIG_HAVE_NOINSTR_HACK)		+= --hacks=noinstr
-objtool-args-$(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)	+= --hacks=skylake
-objtool-args-$(CONFIG_X86_KERNEL_IBT)			+= --ibt
-objtool-args-$(CONFIG_FINEIBT)				+= --cfi
-objtool-args-$(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL)	+= --mcount
-ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
-objtool-args-$(CONFIG_HAVE_OBJTOOL_NOP_MCOUNT)		+= --mnop
-endif
-objtool-args-$(CONFIG_UNWINDER_ORC)			+= --orc
-objtool-args-$(CONFIG_MITIGATION_RETPOLINE)		+= --retpoline
-objtool-args-$(CONFIG_MITIGATION_RETHUNK)		+= --rethunk
-objtool-args-$(CONFIG_MITIGATION_SLS)			+= --sls
-objtool-args-$(CONFIG_STACK_VALIDATION)			+= --stackval
-objtool-args-$(CONFIG_HAVE_STATIC_CALL_INLINE)		+= --static-call
-objtool-args-$(CONFIG_HAVE_UACCESS_VALIDATION)		+= --uaccess
-objtool-args-$(or $(CONFIG_GCOV_KERNEL),$(CONFIG_KCOV))	+= --no-unreachable
-objtool-args-$(CONFIG_PREFIX_SYMBOLS)			+= --prefix=$(CONFIG_FUNCTION_PADDING_BYTES)
-objtool-args-$(CONFIG_OBJTOOL_WERROR)			+= --werror
+# objtool commands
+objtool-cmds-$(CONFIG_HAVE_JUMP_LABEL_HACK)		+= --hacks=jump_label
+objtool-cmds-$(CONFIG_HAVE_NOINSTR_HACK)		+= --hacks=noinstr
+objtool-cmds-$(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)	+= --hacks=skylake
+objtool-cmds-$(CONFIG_X86_KERNEL_IBT)			+= --ibt
+objtool-cmds-$(CONFIG_FINEIBT)				+= --cfi
+objtool-cmds-$(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL)	+= --mcount
+objtool-cmds-$(CONFIG_UNWINDER_ORC)			+= --orc
+objtool-cmds-$(CONFIG_MITIGATION_RETPOLINE)		+= --retpoline
+objtool-cmds-$(CONFIG_MITIGATION_RETHUNK)		+= --rethunk
+objtool-cmds-$(CONFIG_MITIGATION_SLS)			+= --sls
+objtool-cmds-$(CONFIG_STACK_VALIDATION)			+= --stackval
+objtool-cmds-$(CONFIG_HAVE_STATIC_CALL_INLINE)		+= --static-call
+objtool-cmds-$(CONFIG_HAVE_UACCESS_VALIDATION)		+= --uaccess
+objtool-cmds-$(CONFIG_PREFIX_SYMBOLS)			+= --prefix=$(CONFIG_FUNCTION_PADDING_BYTES)
+objtool-cmds-y						+= $(OBJTOOL_ARGS)
 
-objtool-args = $(objtool-args-y)					\
+# objtool options
+ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
+objtool-opts-$(CONFIG_HAVE_OBJTOOL_NOP_MCOUNT)		+= --mnop
+endif
+objtool-opts-$(or $(CONFIG_GCOV_KERNEL),$(CONFIG_KCOV))	+= --no-unreachable
+objtool-opts-$(CONFIG_OBJTOOL_WERROR)			+= --werror
+
+objtool-args = $(objtool-cmds-y) $(objtool-opts-y)			\
 	$(if $(delay-objtool), --link)					\
 	$(if $(part-of-module), --module)
 
@@ -212,7 +216,7 @@ delay-objtool := $(or $(CONFIG_LTO_CLANG),$(CONFIG_X86_KERNEL_IBT),$(CONFIG_KLP_
 cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool-args) $@)
 cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
 
-objtool-enabled := y
+objtool-enabled = $(if $(objtool-cmds-y),y)
 
 endif # CONFIG_OBJTOOL
 
diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o
index 527352c222ff..09af33203bd8 100644
--- a/scripts/Makefile.vmlinux_o
+++ b/scripts/Makefile.vmlinux_o
@@ -36,18 +36,13 @@ endif
 # For !delay-objtool + CONFIG_NOINSTR_VALIDATION, it runs on both translation
 # units and vmlinux.o, with the latter only used for noinstr/unret validation.
 
-objtool-enabled := $(or $(delay-objtool),$(CONFIG_NOINSTR_VALIDATION))
-
-ifeq ($(delay-objtool),y)
-vmlinux-objtool-args-y					+= $(objtool-args-y)
-else
-vmlinux-objtool-args-$(CONFIG_OBJTOOL_WERROR)		+= --werror
+ifneq ($(delay-objtool),y)
+objtool-cmds-y					 =
+objtool-opts-y					+= --link
 endif
 
-vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr \
-							   $(if $(or $(CONFIG_MITIGATION_UNRET_ENTRY),$(CONFIG_MITIGATION_SRSO)), --unret)
-
-objtool-args = $(vmlinux-objtool-args-y) --link
+objtool-cmds-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr \
+						   $(if $(or $(CONFIG_MITIGATION_UNRET_ENTRY),$(CONFIG_MITIGATION_SRSO)), --unret)
 
 # Link of vmlinux.o used for section mismatch analysis
 # ---------------------------------------------------------------------------
-- 
2.53.0

Re: [PATCH 09/14] kbuild: Only run objtool if there is at least one command

[Nathan Chancellor]

On Wed, Mar 04, 2026 at 07:31:28PM -0800, Josh Poimboeuf wrote:
> Split the objtool args into commands and options, such that if no
> commands have been enabled, objtool doesn't run.
> 
> This is in preparation in enabling objtool and klp-build for arm64.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>

I assume this will go with the rest of the series.

> ---
>  arch/x86/boot/startup/Makefile |  2 +-
>  scripts/Makefile.build         |  4 +--
>  scripts/Makefile.lib           | 46 ++++++++++++++++++----------------
>  scripts/Makefile.vmlinux_o     | 15 ++++-------
>  4 files changed, 33 insertions(+), 34 deletions(-)
> 
> diff --git a/arch/x86/boot/startup/Makefile b/arch/x86/boot/startup/Makefile
> index 5e499cfb29b5..a08297829fc6 100644
> --- a/arch/x86/boot/startup/Makefile
> +++ b/arch/x86/boot/startup/Makefile
> @@ -36,7 +36,7 @@ $(patsubst %.o,$(obj)/%.o,$(lib-y)): OBJECT_FILES_NON_STANDARD := y
>  # relocations, even if other objtool actions are being deferred.
>  #
>  $(pi-objs): objtool-enabled	= 1
> -$(pi-objs): objtool-args	= $(if $(delay-objtool),--dry-run,$(objtool-args-y)) --noabs
> +$(pi-objs): objtool-args	= $(if $(delay-objtool),--dry-run,$(objtool-cmds-y) $(objtool-opts-y)) --noabs
>  
>  #
>  # Confine the startup code by prefixing all symbols with __pi_ (for position
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 32e209bc7985..d2d0776df947 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -277,7 +277,7 @@ endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
>  is-standard-object = $(if $(filter-out y%, $(OBJECT_FILES_NON_STANDARD_$(target-stem).o)$(OBJECT_FILES_NON_STANDARD)n),$(is-kernel-object))
>  
>  ifdef CONFIG_OBJTOOL
> -$(obj)/%.o: private objtool-enabled = $(if $(is-standard-object),$(if $(delay-objtool),$(is-single-obj-m),y))
> +$(obj)/%.o: private objtool-enabled = $(if $(is-standard-object),$(if $(objtool-cmds-y),$(if $(delay-objtool),$(is-single-obj-m),y)))
>  endif
>  
>  ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
> @@ -499,7 +499,7 @@ define rule_ld_multi_m
>  	$(call cmd,gen_objtooldep)
>  endef
>  
> -$(multi-obj-m): private objtool-enabled := $(delay-objtool)
> +$(multi-obj-m): private objtool-enabled := $(if $(objtool-cmds-y),$(delay-objtool))
>  $(multi-obj-m): private part-of-module := y
>  $(multi-obj-m): %.o: %.mod FORCE
>  	$(call if_changed_rule,ld_multi_m)
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 0718e39cedda..40a462581666 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -183,27 +183,31 @@ ifdef CONFIG_OBJTOOL
>  
>  objtool := $(objtree)/tools/objtool/objtool
>  
> -objtool-args-$(CONFIG_HAVE_JUMP_LABEL_HACK)		+= --hacks=jump_label
> -objtool-args-$(CONFIG_HAVE_NOINSTR_HACK)		+= --hacks=noinstr
> -objtool-args-$(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)	+= --hacks=skylake
> -objtool-args-$(CONFIG_X86_KERNEL_IBT)			+= --ibt
> -objtool-args-$(CONFIG_FINEIBT)				+= --cfi
> -objtool-args-$(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL)	+= --mcount
> -ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
> -objtool-args-$(CONFIG_HAVE_OBJTOOL_NOP_MCOUNT)		+= --mnop
> -endif
> -objtool-args-$(CONFIG_UNWINDER_ORC)			+= --orc
> -objtool-args-$(CONFIG_MITIGATION_RETPOLINE)		+= --retpoline
> -objtool-args-$(CONFIG_MITIGATION_RETHUNK)		+= --rethunk
> -objtool-args-$(CONFIG_MITIGATION_SLS)			+= --sls
> -objtool-args-$(CONFIG_STACK_VALIDATION)			+= --stackval
> -objtool-args-$(CONFIG_HAVE_STATIC_CALL_INLINE)		+= --static-call
> -objtool-args-$(CONFIG_HAVE_UACCESS_VALIDATION)		+= --uaccess
> -objtool-args-$(or $(CONFIG_GCOV_KERNEL),$(CONFIG_KCOV))	+= --no-unreachable
> -objtool-args-$(CONFIG_PREFIX_SYMBOLS)			+= --prefix=$(CONFIG_FUNCTION_PADDING_BYTES)
> -objtool-args-$(CONFIG_OBJTOOL_WERROR)			+= --werror
> +# objtool commands
> +objtool-cmds-$(CONFIG_HAVE_JUMP_LABEL_HACK)		+= --hacks=jump_label
> +objtool-cmds-$(CONFIG_HAVE_NOINSTR_HACK)		+= --hacks=noinstr
> +objtool-cmds-$(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)	+= --hacks=skylake
> +objtool-cmds-$(CONFIG_X86_KERNEL_IBT)			+= --ibt
> +objtool-cmds-$(CONFIG_FINEIBT)				+= --cfi
> +objtool-cmds-$(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL)	+= --mcount
> +objtool-cmds-$(CONFIG_UNWINDER_ORC)			+= --orc
> +objtool-cmds-$(CONFIG_MITIGATION_RETPOLINE)		+= --retpoline
> +objtool-cmds-$(CONFIG_MITIGATION_RETHUNK)		+= --rethunk
> +objtool-cmds-$(CONFIG_MITIGATION_SLS)			+= --sls
> +objtool-cmds-$(CONFIG_STACK_VALIDATION)			+= --stackval
> +objtool-cmds-$(CONFIG_HAVE_STATIC_CALL_INLINE)		+= --static-call
> +objtool-cmds-$(CONFIG_HAVE_UACCESS_VALIDATION)		+= --uaccess
> +objtool-cmds-$(CONFIG_PREFIX_SYMBOLS)			+= --prefix=$(CONFIG_FUNCTION_PADDING_BYTES)
> +objtool-cmds-y						+= $(OBJTOOL_ARGS)
>  
> -objtool-args = $(objtool-args-y)					\
> +# objtool options
> +ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
> +objtool-opts-$(CONFIG_HAVE_OBJTOOL_NOP_MCOUNT)		+= --mnop
> +endif
> +objtool-opts-$(or $(CONFIG_GCOV_KERNEL),$(CONFIG_KCOV))	+= --no-unreachable
> +objtool-opts-$(CONFIG_OBJTOOL_WERROR)			+= --werror
> +
> +objtool-args = $(objtool-cmds-y) $(objtool-opts-y)			\
>  	$(if $(delay-objtool), --link)					\
>  	$(if $(part-of-module), --module)
>  
> @@ -212,7 +216,7 @@ delay-objtool := $(or $(CONFIG_LTO_CLANG),$(CONFIG_X86_KERNEL_IBT),$(CONFIG_KLP_
>  cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool-args) $@)
>  cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
>  
> -objtool-enabled := y
> +objtool-enabled = $(if $(objtool-cmds-y),y)
>  
>  endif # CONFIG_OBJTOOL
>  
> diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o
> index 527352c222ff..09af33203bd8 100644
> --- a/scripts/Makefile.vmlinux_o
> +++ b/scripts/Makefile.vmlinux_o
> @@ -36,18 +36,13 @@ endif
>  # For !delay-objtool + CONFIG_NOINSTR_VALIDATION, it runs on both translation
>  # units and vmlinux.o, with the latter only used for noinstr/unret validation.
>  
> -objtool-enabled := $(or $(delay-objtool),$(CONFIG_NOINSTR_VALIDATION))
> -
> -ifeq ($(delay-objtool),y)
> -vmlinux-objtool-args-y					+= $(objtool-args-y)
> -else
> -vmlinux-objtool-args-$(CONFIG_OBJTOOL_WERROR)		+= --werror
> +ifneq ($(delay-objtool),y)
> +objtool-cmds-y					 =
> +objtool-opts-y					+= --link
>  endif
>  
> -vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr \
> -							   $(if $(or $(CONFIG_MITIGATION_UNRET_ENTRY),$(CONFIG_MITIGATION_SRSO)), --unret)
> -
> -objtool-args = $(vmlinux-objtool-args-y) --link
> +objtool-cmds-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr \
> +						   $(if $(or $(CONFIG_MITIGATION_UNRET_ENTRY),$(CONFIG_MITIGATION_SRSO)), --unret)
>  
>  # Link of vmlinux.o used for section mismatch analysis
>  # ---------------------------------------------------------------------------
> -- 
> 2.53.0
> 

[PATCH 10/14] objtool: Ignore jumps to the end of the function for non-CFG arches

[Josh Poimboeuf]

Sometimes Clang arm64 code jumps to the end of the function for UB.
No need to make that an error, arm64 doesn't reverse engineer the CFG
anyway.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 tools/objtool/check.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index f73cf1382e5c..23cde2de66b9 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1630,10 +1630,12 @@ static int add_jump_destinations(struct objtool_file *file)
 			/*
 			 * GCOV/KCOV dead code can jump to the end of
 			 * the function/section.
+			 *
+			 * Clang on arm64 also does this sometimes for
+			 * undefined behavior.
 			 */
-			if (file->ignore_unreachables && func &&
-			    dest_sec == insn->sec &&
-			    dest_off == func->offset + func->len)
+			if ((file->ignore_unreachables || (!opts.stackval && !opts.orc)) &&
+			    func && dest_sec == insn->sec && dest_off == func->offset + func->len)
 				continue;
 
 			ERROR_INSN(insn, "can't find jump dest instruction at %s",
-- 
2.53.0

Re: [PATCH 10/14] objtool: Ignore jumps to the end of the function for non-CFG arches

[Song Liu]

On Wed, Mar 4, 2026 at 7:31 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> Sometimes Clang arm64 code jumps to the end of the function for UB.
> No need to make that an error, arm64 doesn't reverse engineer the CFG
> anyway.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Acked-by: Song Liu <song@kernel.org>

[PATCH 11/14] objtool: Allow empty alternatives

[Josh Poimboeuf]

arm64 can have empty alternatives, which are effectively no-ops.  Ignore
them.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 tools/objtool/check.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 23cde2de66b9..036adbd67488 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1994,10 +1994,8 @@ static int add_special_section_alts(struct objtool_file *file)
 		}
 
 		if (special_alt->group) {
-			if (!special_alt->orig_len) {
-				ERROR_INSN(orig_insn, "empty alternative entry");
+			if (!special_alt->orig_len)
 				continue;
-			}
 
 			if (handle_group_alt(file, special_alt, orig_insn, &new_insn))
 				return -1;
-- 
2.53.0

Re: [PATCH 11/14] objtool: Allow empty alternatives

[Song Liu]

On Wed, Mar 4, 2026 at 7:31 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> arm64 can have empty alternatives, which are effectively no-ops.  Ignore
> them.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Acked-by: Song Liu <song@kernel.org>

[PATCH 12/14] objtool: Reuse consecutive string references

[Josh Poimboeuf]

For duplicate strings, elf_add_string() just blindly adds duplicates.

That can be a problem for arm64 which often uses two consecutive
instructions (and corresponding relocations) to put an address into a
register, like:

  d8:   90000001        adrp    x1, 0 <meminfo_proc_show>       d8: R_AARCH64_ADR_PREL_PG_HI21  .rodata.meminfo_proc_show.str1.8
  dc:   91000021        add     x1, x1, #0x0    dc: R_AARCH64_ADD_ABS_LO12_NC   .rodata.meminfo_proc_show.str1.8

Referencing two different string addresses in the adrp+add pair can
result in a corrupt string addresses.  Detect such consecutive reuses
and force them to use the same string.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 tools/objtool/elf.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 3da90686350d..52ef991115fc 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -1321,6 +1321,8 @@ struct elf *elf_create_file(GElf_Ehdr *ehdr, const char *name)
 
 unsigned int elf_add_string(struct elf *elf, struct section *strtab, const char *str)
 {
+	static unsigned int last_off;
+	static const char *last_str;
 	unsigned int offset;
 
 	if (!strtab)
@@ -1329,17 +1331,22 @@ unsigned int elf_add_string(struct elf *elf, struct section *strtab, const char
 		ERROR("can't find .strtab section");
 		return -1;
 	}
-
 	if (!strtab->sh.sh_addralign) {
 		ERROR("'%s': invalid sh_addralign", strtab->name);
 		return -1;
 	}
 
+	if (last_str && !strcmp(last_str, str))
+		return last_off;
+
 	offset = ALIGN(strtab->sh.sh_size, strtab->sh.sh_addralign);
 
 	if (!elf_add_data(elf, strtab, str, strlen(str) + 1))
 		return -1;
 
+	last_str = str;
+	last_off = offset;
+
 	return offset;
 }
 
-- 
2.53.0

Re: [PATCH 12/14] objtool: Reuse consecutive string references

[Song Liu]

On Wed, Mar 4, 2026 at 7:31 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> For duplicate strings, elf_add_string() just blindly adds duplicates.
>
> That can be a problem for arm64 which often uses two consecutive
> instructions (and corresponding relocations) to put an address into a
> register, like:
>
>   d8:   90000001        adrp    x1, 0 <meminfo_proc_show>       d8: R_AARCH64_ADR_PREL_PG_HI21  .rodata.meminfo_proc_show.str1.8
>   dc:   91000021        add     x1, x1, #0x0    dc: R_AARCH64_ADD_ABS_LO12_NC   .rodata.meminfo_proc_show.str1.8
>
> Referencing two different string addresses in the adrp+add pair can
> result in a corrupt string addresses.  Detect such consecutive reuses
> and force them to use the same string.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Acked-by: Song Liu <song@kernel.org>

[PATCH 13/14] objtool: Introduce objtool for arm64

[Josh Poimboeuf]

Add basic support for arm64 on objtool.  Only --checksum is currently
supported.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/arm64/Kconfig                            |   2 +
 tools/objtool/Makefile                        |   4 +
 tools/objtool/arch/arm64/Build                |   2 +
 tools/objtool/arch/arm64/decode.c             | 116 ++++++++++++++++++
 .../arch/arm64/include/arch/cfi_regs.h        |  11 ++
 tools/objtool/arch/arm64/include/arch/elf.h   |  13 ++
 .../objtool/arch/arm64/include/arch/special.h |  21 ++++
 tools/objtool/arch/arm64/special.c            |  21 ++++
 8 files changed, 190 insertions(+)
 create mode 100644 tools/objtool/arch/arm64/Build
 create mode 100644 tools/objtool/arch/arm64/decode.c
 create mode 100644 tools/objtool/arch/arm64/include/arch/cfi_regs.h
 create mode 100644 tools/objtool/arch/arm64/include/arch/elf.h
 create mode 100644 tools/objtool/arch/arm64/include/arch/special.h
 create mode 100644 tools/objtool/arch/arm64/special.c

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 38dba5f7e4d2..354aa80c5b4b 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -236,9 +236,11 @@ config ARM64
 	select HAVE_HW_BREAKPOINT if PERF_EVENTS
 	select HAVE_IOREMAP_PROT
 	select HAVE_IRQ_TIME_ACCOUNTING
+	select HAVE_KLP_BUILD
 	select HAVE_LIVEPATCH
 	select HAVE_MOD_ARCH_SPECIFIC
 	select HAVE_NMI
+	select HAVE_OBJTOOL
 	select HAVE_PERF_EVENTS
 	select HAVE_PERF_EVENTS_NMI if ARM64_PSEUDO_NMI
 	select HAVE_PERF_REGS
diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 6964175abdfd..288db5bc3002 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -11,6 +11,10 @@ ifeq ($(SRCARCH),loongarch)
 	BUILD_ORC	   := y
 endif
 
+ifeq ($(SRCARCH),arm64)
+	ARCH_HAS_KLP := y
+endif
+
 ifeq ($(ARCH_HAS_KLP),y)
 	HAVE_XXHASH = $(shell printf "$(pound)include <xxhash.h>\nXXH3_state_t *state;int main() {}" | \
 		      $(HOSTCC) -xc - -o /dev/null -lxxhash 2> /dev/null && echo y || echo n)
diff --git a/tools/objtool/arch/arm64/Build b/tools/objtool/arch/arm64/Build
new file mode 100644
index 000000000000..d24d5636a5b8
--- /dev/null
+++ b/tools/objtool/arch/arm64/Build
@@ -0,0 +1,2 @@
+objtool-y += decode.o
+objtool-y += special.o
diff --git a/tools/objtool/arch/arm64/decode.c b/tools/objtool/arch/arm64/decode.c
new file mode 100644
index 000000000000..ee93c096243f
--- /dev/null
+++ b/tools/objtool/arch/arm64/decode.c
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <objtool/check.h>
+#include <objtool/disas.h>
+#include <objtool/elf.h>
+#include <objtool/arch.h>
+#include <objtool/warn.h>
+#include <objtool/builtin.h>
+
+const char *arch_reg_name[CFI_NUM_REGS] = {};
+
+int arch_ftrace_match(const char *name)
+{
+	return 0;
+}
+
+s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
+{
+	return reloc_addend(reloc);
+}
+
+bool arch_callee_saved_reg(unsigned char reg)
+{
+	return false;
+}
+
+int arch_decode_hint_reg(u8 sp_reg, int *base)
+{
+	exit(-1);
+}
+
+const char *arch_nop_insn(int len)
+{
+	exit(-1);
+}
+
+const char *arch_ret_insn(int len)
+{
+	exit(-1);
+}
+
+int arch_decode_instruction(struct objtool_file *file, const struct section *sec,
+			    unsigned long offset, unsigned int maxlen,
+			    struct instruction *insn)
+{
+	u32 i = *((u32 *)(sec->data->d_buf + offset));
+
+	insn->len = 4;
+
+	/*
+	 * These are the bare minimum needed for static branch detection and
+	 * checksum calculations.
+	 */
+	if (i == 0xd503201f || i == 0x2a1f03f7) {
+		/* For static branches */
+		insn->type = INSN_NOP;
+	} else if ((i & 0xfc000000) == 0x14000000) {
+		/* For static branches and intra-TU sibling calls */
+		insn->type = INSN_JUMP_UNCONDITIONAL;
+		insn->immediate = sign_extend64(i & 0x03ffffff, 25);
+	} else if ((i & 0xfc000000) == 0x94000000) {
+		/* For intra-TU calls */
+		insn->type = INSN_CALL;
+		insn->immediate = sign_extend64(i & 0x03ffffff, 25);
+	} else if ((i & 0xff000000) == 0x54000000) {
+		/* For intra-TU conditional sibling calls */
+		insn->type = INSN_JUMP_CONDITIONAL;
+		insn->immediate = sign_extend64((i & 0xffffe0) >> 5, 18);
+	} else {
+		insn->type = INSN_OTHER;
+	}
+
+	return 0;
+}
+
+u64 arch_adjusted_addend(struct reloc *reloc)
+{
+	return reloc_addend(reloc);
+}
+
+unsigned long arch_jump_destination(struct instruction *insn)
+{
+	return insn->offset + (insn->immediate << 2);
+}
+
+bool arch_pc_relative_reloc(struct reloc *reloc)
+{
+	return false;
+}
+
+void arch_initial_func_cfi_state(struct cfi_init_state *state)
+{
+	state->cfa.base = CFI_UNDEFINED;
+}
+
+unsigned int arch_reloc_size(struct reloc *reloc)
+{
+	switch (reloc_type(reloc)) {
+	case R_AARCH64_ABS64:
+	case R_AARCH64_PREL64:
+		return 8;
+	default:
+		return 4;
+	}
+}
+
+#ifdef DISAS
+int arch_disas_info_init(struct disassemble_info *dinfo)
+{
+	return disas_info_init(dinfo, bfd_arch_aarch64,
+			       bfd_mach_arm_unknown, bfd_mach_aarch64,
+			       NULL);
+}
+#endif /* DISAS */
diff --git a/tools/objtool/arch/arm64/include/arch/cfi_regs.h b/tools/objtool/arch/arm64/include/arch/cfi_regs.h
new file mode 100644
index 000000000000..49c81cbb6646
--- /dev/null
+++ b/tools/objtool/arch/arm64/include/arch/cfi_regs.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _OBJTOOL_ARCH_CFI_REGS_H
+#define _OBJTOOL_ARCH_CFI_REGS_H
+
+/* These aren't actually used for arm64 */
+#define CFI_BP 0
+#define CFI_SP 0
+#define CFI_RA 0
+#define CFI_NUM_REGS 2
+
+#endif /* _OBJTOOL_ARCH_CFI_REGS_H */
diff --git a/tools/objtool/arch/arm64/include/arch/elf.h b/tools/objtool/arch/arm64/include/arch/elf.h
new file mode 100644
index 000000000000..80a1bc479930
--- /dev/null
+++ b/tools/objtool/arch/arm64/include/arch/elf.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _OBJTOOL_ARCH_ELF_H
+#define _OBJTOOL_ARCH_ELF_H
+
+#define R_NONE		R_AARCH64_NONE
+#define R_ABS64		R_AARCH64_ABS64
+#define R_ABS32		R_AARCH64_ABS32
+#define R_DATA32	R_AARCH64_PREL32
+#define R_DATA64	R_AARCH64_PREL64
+#define R_TEXT32	R_AARCH64_PREL32
+#define R_TEXT64	R_AARCH64_PREL64
+
+#endif /* _OBJTOOL_ARCH_ELF_H */
diff --git a/tools/objtool/arch/arm64/include/arch/special.h b/tools/objtool/arch/arm64/include/arch/special.h
new file mode 100644
index 000000000000..8ae804a83ea4
--- /dev/null
+++ b/tools/objtool/arch/arm64/include/arch/special.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _OBJTOOL_ARCH_SPECIAL_H
+#define _OBJTOOL_ARCH_SPECIAL_H
+
+#define EX_ENTRY_SIZE 12
+#define EX_ORIG_OFFSET 0
+#define EX_NEW_OFFSET 4
+
+#define JUMP_ENTRY_SIZE 16
+#define JUMP_ORIG_OFFSET 0
+#define JUMP_NEW_OFFSET 4
+#define JUMP_KEY_OFFSET 8
+
+#define ALT_ENTRY_SIZE 12
+#define ALT_ORIG_OFFSET 0
+#define ALT_NEW_OFFSET 4
+#define ALT_FEATURE_OFFSET 8
+#define ALT_ORIG_LEN_OFFSET 10
+#define ALT_NEW_LEN_OFFSET 11
+
+#endif /* _OBJTOOL_ARCH_SPECIAL_H */
diff --git a/tools/objtool/arch/arm64/special.c b/tools/objtool/arch/arm64/special.c
new file mode 100644
index 000000000000..3c2b83d94939
--- /dev/null
+++ b/tools/objtool/arch/arm64/special.c
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <objtool/special.h>
+
+bool arch_support_alt_relocation(struct special_alt *special_alt,
+				 struct instruction *insn,
+				 struct reloc *reloc)
+{
+	return false;
+}
+
+struct reloc *arch_find_switch_table(struct objtool_file *file,
+				     struct instruction *insn,
+				     unsigned long *table_size)
+{
+	return NULL;
+}
+
+const char *arch_cpu_feature_name(int feature_number)
+{
+	return NULL;
+}
-- 
2.53.0

[PATCH 14/14] klp-build: Support cross-compilation

[Josh Poimboeuf]

Add support for cross-compilation.  The user must export ARCH, and
either CROSS_COMPILE or LLVM.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 scripts/livepatch/klp-build | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
index 809e198a561d..b6c057e2120f 100755
--- a/scripts/livepatch/klp-build
+++ b/scripts/livepatch/klp-build
@@ -404,6 +404,14 @@ validate_patches() {
 	revert_patches
 }
 
+cross_compile_init() {
+	if [[ -v LLVM ]]; then
+		OBJCOPY=llvm-objcopy
+	else
+		OBJCOPY="${CROSS_COMPILE:-}objcopy"
+	fi
+}
+
 do_init() {
 	# We're not yet smart enough to handle anything other than in-tree
 	# builds in pwd.
@@ -420,6 +428,7 @@ do_init() {
 	validate_config
 	set_module_name
 	set_kernelversion
+	cross_compile_init
 }
 
 # Refresh the patch hunk headers, specifically the line numbers and counts.
@@ -783,7 +792,7 @@ build_patch_module() {
 	cp -f "$kmod_file" "$kmod_file.orig"
 
 	# Work around issue where slight .config change makes corrupt BTF
-	objcopy --remove-section=.BTF "$kmod_file"
+	"$OBJCOPY" --remove-section=.BTF "$kmod_file"
 
 	# Fix (and work around) linker wreckage for klp syms / relocs
 	"$SRC/tools/objtool/objtool" klp post-link "$kmod_file" || die "objtool klp post-link failed"
-- 
2.53.0

Re: [PATCH 14/14] klp-build: Support cross-compilation

[Song Liu]

On Wed, Mar 4, 2026 at 7:32 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> Add support for cross-compilation.  The user must export ARCH, and
> either CROSS_COMPILE or LLVM.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> ---
>  scripts/livepatch/klp-build | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
> index 809e198a561d..b6c057e2120f 100755
> --- a/scripts/livepatch/klp-build
> +++ b/scripts/livepatch/klp-build
> @@ -404,6 +404,14 @@ validate_patches() {
>         revert_patches
>  }
>
> +cross_compile_init() {
> +       if [[ -v LLVM ]]; then
> +               OBJCOPY=llvm-objcopy
> +       else
> +               OBJCOPY="${CROSS_COMPILE:-}objcopy"
> +       fi
> +}

Shall we show a specific warning if
  - ARCH is set; and
  - ARCH is not the same as (uname -m); and
  - neither LLVM nor CROSS_COMPILE is set.

Thanks,
Song

Re: [PATCH 14/14] klp-build: Support cross-compilation

[Josh Poimboeuf]

On Wed, Mar 11, 2026 at 04:18:40PM -0700, Song Liu wrote:
> On Wed, Mar 4, 2026 at 7:32 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
> >
> > Add support for cross-compilation.  The user must export ARCH, and
> > either CROSS_COMPILE or LLVM.
> >
> > Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> > ---
> >  scripts/livepatch/klp-build | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
> > index 809e198a561d..b6c057e2120f 100755
> > --- a/scripts/livepatch/klp-build
> > +++ b/scripts/livepatch/klp-build
> > @@ -404,6 +404,14 @@ validate_patches() {
> >         revert_patches
> >  }
> >
> > +cross_compile_init() {
> > +       if [[ -v LLVM ]]; then
> > +               OBJCOPY=llvm-objcopy
> > +       else
> > +               OBJCOPY="${CROSS_COMPILE:-}objcopy"
> > +       fi
> > +}
> 
> Shall we show a specific warning if
>   - ARCH is set; and
>   - ARCH is not the same as (uname -m); and
>   - neither LLVM nor CROSS_COMPILE is set.

Yeah, I think that would be a good idea.  Will do that for v2.

-- 
Josh

Re: [PATCH 14/14] klp-build: Support cross-compilation

[Josh Poimboeuf]

On Mon, Mar 16, 2026 at 12:15:28PM -0700, Josh Poimboeuf wrote:
> On Wed, Mar 11, 2026 at 04:18:40PM -0700, Song Liu wrote:
> > On Wed, Mar 4, 2026 at 7:32 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
> > >
> > > Add support for cross-compilation.  The user must export ARCH, and
> > > either CROSS_COMPILE or LLVM.
> > >
> > > Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> > > ---
> > >  scripts/livepatch/klp-build | 11 ++++++++++-
> > >  1 file changed, 10 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
> > > index 809e198a561d..b6c057e2120f 100755
> > > --- a/scripts/livepatch/klp-build
> > > +++ b/scripts/livepatch/klp-build
> > > @@ -404,6 +404,14 @@ validate_patches() {
> > >         revert_patches
> > >  }
> > >
> > > +cross_compile_init() {
> > > +       if [[ -v LLVM ]]; then
> > > +               OBJCOPY=llvm-objcopy
> > > +       else
> > > +               OBJCOPY="${CROSS_COMPILE:-}objcopy"
> > > +       fi
> > > +}
> > 
> > Shall we show a specific warning if
> >   - ARCH is set; and
> >   - ARCH is not the same as (uname -m); and
> >   - neither LLVM nor CROSS_COMPILE is set.
> 
> Yeah, I think that would be a good idea.  Will do that for v2.

So, in general ARCH is complicated.  For example:

 - ARCH=arm64 would never match "uname -m" (aarch64)
 - ARCH=i386 would use the same gcc binary (no cross-compiler needed)
 - I'm sure there are many other edge cases...

Instead of a manual error, it may be simpler to just let the build fail
naturally if the user doesn't set the right ARCH.

Though, I think the check can be improved slightly, as ARCH is a
reasonably good indicator that cross-compiling is happening.  So I can
at least add an ARCH check at the beginning like so?

cross_compile_init() {
	if [[ ! -v ARCH ]]; then
		OBJCOPY=objcopy
		return 0
	fi

	if [[ -v LLVM ]]; then
		OBJCOPY=llvm-objcopy
	else
		OBJCOPY="${CROSS_COMPILE:-}objcopy"
	fi
}

-- 
Josh

Re: [PATCH 14/14] klp-build: Support cross-compilation

[Song Liu]

On Tue, Mar 17, 2026 at 10:52 AM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
[...]
> >
> > Yeah, I think that would be a good idea.  Will do that for v2.
>
> So, in general ARCH is complicated.  For example:
>
>  - ARCH=arm64 would never match "uname -m" (aarch64)
>  - ARCH=i386 would use the same gcc binary (no cross-compiler needed)
>  - I'm sure there are many other edge cases...

Agreed. I haven't worked with i386 for a long time, but I did notice
the arm64 vs. aarch64 difference.

> Instead of a manual error, it may be simpler to just let the build fail
> naturally if the user doesn't set the right ARCH.
>
> Though, I think the check can be improved slightly, as ARCH is a
> reasonably good indicator that cross-compiling is happening.  So I can
> at least add an ARCH check at the beginning like so?
>
> cross_compile_init() {
>         if [[ ! -v ARCH ]]; then
>                 OBJCOPY=objcopy
>                 return 0
>         fi
>
>         if [[ -v LLVM ]]; then
>                 OBJCOPY=llvm-objcopy
>         else
>                 OBJCOPY="${CROSS_COMPILE:-}objcopy"
>         fi
> }

Do we need ARCH when CROSS_COMPILE is set? I was
under the impression that CROSS_COMPILE doesn't require
ARCH.

Thanks,
Song

Re: [PATCH 14/14] klp-build: Support cross-compilation

[Josh Poimboeuf]

On Tue, Mar 17, 2026 at 11:21:43AM -0700, Song Liu wrote:
> On Tue, Mar 17, 2026 at 10:52 AM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
> [...]
> > >
> > > Yeah, I think that would be a good idea.  Will do that for v2.
> >
> > So, in general ARCH is complicated.  For example:
> >
> >  - ARCH=arm64 would never match "uname -m" (aarch64)
> >  - ARCH=i386 would use the same gcc binary (no cross-compiler needed)
> >  - I'm sure there are many other edge cases...
> 
> Agreed. I haven't worked with i386 for a long time, but I did notice
> the arm64 vs. aarch64 difference.
> 
> > Instead of a manual error, it may be simpler to just let the build fail
> > naturally if the user doesn't set the right ARCH.
> >
> > Though, I think the check can be improved slightly, as ARCH is a
> > reasonably good indicator that cross-compiling is happening.  So I can
> > at least add an ARCH check at the beginning like so?
> >
> > cross_compile_init() {
> >         if [[ ! -v ARCH ]]; then
> >                 OBJCOPY=objcopy
> >                 return 0
> >         fi
> >
> >         if [[ -v LLVM ]]; then
> >                 OBJCOPY=llvm-objcopy
> >         else
> >                 OBJCOPY="${CROSS_COMPILE:-}objcopy"
> >         fi
> > }
> 
> Do we need ARCH when CROSS_COMPILE is set? I was
> under the impression that CROSS_COMPILE doesn't require
> ARCH.

If CROSS_COMPILE is used without ARCH, it will just try to use the host
arch.  I'm not sure if that's considered cross-compiling?   I suppose it
should use the CROSS_COMPILE version of objcopy in that case?  Though in
practice it probably doesn't matter.

I guess the original version of the function is probably fine and we
don't need to complicate matters.

-- 
Josh

Re: [PATCH 14/14] klp-build: Support cross-compilation

[Song Liu]

On Tue, Mar 17, 2026 at 11:53 AM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
[...]
> >
> > Do we need ARCH when CROSS_COMPILE is set? I was
> > under the impression that CROSS_COMPILE doesn't require
> > ARCH.
>
> If CROSS_COMPILE is used without ARCH, it will just try to use the host
> arch.  I'm not sure if that's considered cross-compiling?   I suppose it
> should use the CROSS_COMPILE version of objcopy in that case?  Though in
> practice it probably doesn't matter.
>
> I guess the original version of the function is probably fine and we
> don't need to complicate matters.

Agreed that the original version works fine. Thanks for bearing with my
nitpick on this.

Song

Re: [PATCH 00/14] objtool/arm64: Port klp-build to arm64

[Song Liu]

On Wed, Mar 4, 2026 at 7:31 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> Port objtool and the klp-build tooling (for building livepatch modules)
> to arm64.
>
> Note this doesn't bring all the objtool bells and whistles to arm64, nor
> any of the CFG reverse engineering.  This only adds the bare minimum
> needed for 'objtool --checksum'.
>
> And note that objtool still doesn't get enabled at all for normal arm64
> kernel builds, so this doesn't affect any users other than those running
> klp-build directly.

I run this test [1] with this set on arm64. Everything works as expected.

Thanks for enabling this.
Song

[1] https://lore.kernel.org/live-patching/20260212192201.3593879-9-song@kernel.org/