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[PATCH 5/8] objtool: Convert annotations to assembler macros

Josh Poimboeuf posted 8 patches 1 week, 5 days ago
[PATCH 5/8] objtool: Convert annotations to assembler macros
Posted by Josh Poimboeuf 1 week, 5 days ago 
Improve code generation readability by converting the objtool
annotations into assembler macros which are created when annotate.h is
included.

Before:

  .pushsection .discard.annotate_insn, "M", @progbits, 8; .long 1b - ., 8; .popsection

After:

  ANNOTATE_REACHABLE loc=1b

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/asm.h        |   8 +-
 arch/x86/include/asm/jump_label.h |   1 +
 include/linux/annotate.h          | 132 +++++++++++++++---------------
 3 files changed, 72 insertions(+), 69 deletions(-)

diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
index 0e8c611bc9e2..770321c908e5 100644
--- a/arch/x86/include/asm/asm.h
+++ b/arch/x86/include/asm/asm.h
@@ -2,15 +2,15 @@
 #ifndef _ASM_X86_ASM_H
 #define _ASM_X86_ASM_H
 
-#include <linux/annotate.h>
-
 #ifdef __ASSEMBLER__
+# define __ASM_C(a,b)			a
 # define __ASM_FORM(x, ...)		x,## __VA_ARGS__
 # define __ASM_FORM_RAW(x, ...)		x,## __VA_ARGS__
 # define __ASM_FORM_COMMA(x, ...)	x,## __VA_ARGS__,
 # define __ASM_REGPFX			%
 #else
 #include <linux/stringify.h>
+# define __ASM_C(a,b)			b
 # define __ASM_FORM(x, ...)		" " __stringify(x,##__VA_ARGS__) " "
 # define __ASM_FORM_RAW(x, ...)		    __stringify(x,##__VA_ARGS__)
 # define __ASM_FORM_COMMA(x, ...)	" " __stringify(x,##__VA_ARGS__) ","
@@ -115,6 +115,10 @@
 
 #endif
 
+#define DEFINE_MACRO(name)						\
+	__ASM_C(DEFINE_ ## name,					\
+		asm(__stringify(DEFINE_ ## name)))
+
 #ifndef __ASSEMBLER__
 static __always_inline __pure void *rip_rel_ptr(void *p)
 {
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index 05b16299588d..d34a16a4d305 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -11,6 +11,7 @@
 
 #include <linux/stringify.h>
 #include <linux/types.h>
+#include <linux/annotate.h>
 
 #define JUMP_TABLE_ENTRY(key, label)			\
 	".pushsection __jump_table,  \"aw\" \n\t"	\
diff --git a/include/linux/annotate.h b/include/linux/annotate.h
index 1678410efa1b..8b28f1a81ec4 100644
--- a/include/linux/annotate.h
+++ b/include/linux/annotate.h
@@ -3,53 +3,43 @@
 #define _LINUX_ANNOTATE_H
 
 #include <linux/objtool_types.h>
+#include <linux/stringify.h>
+#include <asm/asm.h>
+
+#define DEFINE___ANNOTATE						\
+	.macro __ANNOTATE sec, type, loc;				\
+	.pushsection __ASM_C(\sec, \\sec), "M", @progbits, 8;		\
+		.long __ASM_C(\loc, \\loc) - .;				\
+		.long __ASM_C(\type, \\type);				\
+	.popsection;							\
+	.endm
+
+#define __DEFINE_ANNOTATE(sec, name, type)				\
+	.macro name loc=910b;						\
+	910: __ANNOTATE sec, type, __ASM_C(\loc, \\loc);		\
+	.endm
+
+#define DEFINE_ANNOTATE(type)						\
+	__DEFINE_ANNOTATE(.discard.annotate_insn,			\
+			  ANNOTATE_ ## type, ANNOTYPE_ ## type)
+
+#define DEFINE_ANNOTATE_DATA(type)					\
+	__DEFINE_ANNOTATE(.discard.annotate_data,			\
+			  ANNOTATE_ ## type, ANNOTYPE_ ## type)
 
 #ifdef CONFIG_OBJTOOL
 
-#define __ASM_ANNOTATE(section, label, type)				\
-	.pushsection section, "M", @progbits, 8;			\
-	.long label - ., type;						\
-	.popsection
-
-#ifndef __ASSEMBLY__
-
-#define ASM_ANNOTATE_LABEL(label, type)					\
-	__stringify(__ASM_ANNOTATE(.discard.annotate_insn, label, type))
-
-#define ASM_ANNOTATE(type)						\
-	"911: "								\
-	__stringify(__ASM_ANNOTATE(.discard.annotate_insn, 911b, type))
-
-#define ASM_ANNOTATE_DATA(type)						\
-	"912: "								\
-	__stringify(__ASM_ANNOTATE(.discard.annotate_data, 912b, type))
-
-#else /* __ASSEMBLY__ */
-
-.macro ANNOTATE type
-.Lhere_\@:
-	__ASM_ANNOTATE(.discard.annotate_insn, .Lhere_\@, \type)
-.endm
-
-.macro ANNOTATE_DATA type
-.Lhere_\@:
-	__ASM_ANNOTATE(.discard.annotate_data, .Lhere_\@, \type)
-.endm
-
-#endif /* __ASSEMBLY__ */
-
-#else /* !CONFIG_OBJTOOL */
-#ifndef __ASSEMBLY__
-#define ASM_ANNOTATE_LABEL(label, type) ""
-#define ASM_ANNOTATE(type)
-#define ASM_ANNOTATE_DATA(type)
-#else /* __ASSEMBLY__ */
-.macro ANNOTATE type
-.endm
-.macro ANNOTATE_DATA type
-.endm
-#endif /* __ASSEMBLY__ */
-#endif /* !CONFIG_OBJTOOL */
+DEFINE_MACRO(__ANNOTATE);
+DEFINE_MACRO(ANNOTATE(NOENDBR));
+DEFINE_MACRO(ANNOTATE(RETPOLINE_SAFE));
+DEFINE_MACRO(ANNOTATE(INSTR_BEGIN));
+DEFINE_MACRO(ANNOTATE(INSTR_END));
+DEFINE_MACRO(ANNOTATE(IGNORE_ALTERNATIVE));
+DEFINE_MACRO(ANNOTATE(INTRA_FUNCTION_CALL));
+DEFINE_MACRO(ANNOTATE(UNRET_BEGIN));
+DEFINE_MACRO(ANNOTATE(REACHABLE));
+DEFINE_MACRO(ANNOTATE(NOCFI));
+DEFINE_MACRO(ANNOTATE_DATA(DATA_SPECIAL));
 
 #ifndef __ASSEMBLY__
 
@@ -57,30 +47,30 @@
  * Annotate away the various 'relocation to !ENDBR` complaints; knowing that
  * these relocations will never be used for indirect calls.
  */
-#define ANNOTATE_NOENDBR		ASM_ANNOTATE(ANNOTYPE_NOENDBR)
-#define ANNOTATE_NOENDBR_SYM(sym)	asm(ASM_ANNOTATE_LABEL(sym, ANNOTYPE_NOENDBR))
+#define ANNOTATE_NOENDBR		"ANNOTATE_NOENDBR"
+#define ANNOTATE_NOENDBR_SYM(sym)	asm("ANNOTATE_NOENDBR loc=" __stringify(sym))
 
 /*
  * This should be used immediately before an indirect jump/call. It tells
  * objtool the subsequent indirect jump/call is vouched safe for retpoline
  * builds.
  */
-#define ANNOTATE_RETPOLINE_SAFE		ASM_ANNOTATE(ANNOTYPE_RETPOLINE_SAFE)
+#define ANNOTATE_RETPOLINE_SAFE		"ANNOTATE_RETPOLINE_SAFE"
 /*
  * See linux/instrumentation.h
  */
-#define ANNOTATE_INSTR_BEGIN(label)	ASM_ANNOTATE_LABEL(label, ANNOTYPE_INSTR_BEGIN)
-#define ANNOTATE_INSTR_END(label)	ASM_ANNOTATE_LABEL(label, ANNOTYPE_INSTR_END)
+#define ANNOTATE_INSTR_BEGIN(label)	"ANNOTATE_INSTR_BEGIN loc=" __stringify(label)
+#define ANNOTATE_INSTR_END(label)	"ANNOTATE_INSTR_END loc=" __stringify(label)
 /*
  * objtool annotation to ignore the alternatives and only consider the original
  * instruction(s).
  */
-#define ANNOTATE_IGNORE_ALTERNATIVE	ASM_ANNOTATE(ANNOTYPE_IGNORE_ALTERNATIVE)
+#define ANNOTATE_IGNORE_ALTERNATIVE	"ANNOTATE_IGNORE_ALTERNATIVE"
 /*
  * This macro indicates that the following intra-function call is valid.
  * Any non-annotated intra-function call will cause objtool to issue a warning.
  */
-#define ANNOTATE_INTRA_FUNCTION_CALL	ASM_ANNOTATE(ANNOTYPE_INTRA_FUNCTION_CALL)
+#define ANNOTATE_INTRA_FUNCTION_CALL	"ANNOTATE_INTRA_FUNCTION_CALL"
 /*
  * Use objtool to validate the entry requirement that all code paths do
  * VALIDATE_UNRET_END before RET.
@@ -88,13 +78,13 @@
  * NOTE: The macro must be used at the beginning of a global symbol, otherwise
  * it will be ignored.
  */
-#define ANNOTATE_UNRET_BEGIN		ASM_ANNOTATE(ANNOTYPE_UNRET_BEGIN)
+#define ANNOTATE_UNRET_BEGIN		"ANNOTATE_UNRET_BEGIN"
 /*
  * This should be used to refer to an instruction that is considered
  * terminating, like a noreturn CALL or UD2 when we know they are not -- eg
  * WARN using UD2.
  */
-#define ANNOTATE_REACHABLE_LABEL(label)	ASM_ANNOTATE_LABEL(label, ANNOTYPE_REACHABLE)
+#define ANNOTATE_REACHABLE_LABEL(label)	"ANNOTATE_REACHABLE loc=" __stringify(label)
 /*
  * This should not be used; it annotates away CFI violations. There are a few
  * valid use cases like kexec handover to the next kernel image, and there is
@@ -103,25 +93,33 @@
  * There are also a few real issues annotated away, like EFI because we can't
  * control the EFI code.
  */
-#define ANNOTATE_NOCFI_SYM(sym)		asm(ASM_ANNOTATE_LABEL(sym, ANNOTYPE_NOCFI))
+#define ANNOTATE_NOCFI_SYM(sym)		asm("ANNOTATE_NOCFI loc=" __stringify(sym))
 
 /*
  * Annotate a special section entry.  This emables livepatch module generation
  * to find and extract individual special section entries as needed.
  */
-#define ANNOTATE_DATA_SPECIAL		ASM_ANNOTATE_DATA(ANNOTYPE_DATA_SPECIAL)
+#define ANNOTATE_DATA_SPECIAL		"ANNOTATE_DATA_SPECIAL"
 
-#else /* __ASSEMBLY__ */
-#define ANNOTATE_NOENDBR		ANNOTATE type=ANNOTYPE_NOENDBR
-#define ANNOTATE_RETPOLINE_SAFE		ANNOTATE type=ANNOTYPE_RETPOLINE_SAFE
-/*	ANNOTATE_INSTR_BEGIN		ANNOTATE type=ANNOTYPE_INSTR_BEGIN */
-/*	ANNOTATE_INSTR_END		ANNOTATE type=ANNOTYPE_INSTR_END */
-#define ANNOTATE_IGNORE_ALTERNATIVE	ANNOTATE type=ANNOTYPE_IGNORE_ALTERNATIVE
-#define ANNOTATE_INTRA_FUNCTION_CALL	ANNOTATE type=ANNOTYPE_INTRA_FUNCTION_CALL
-#define ANNOTATE_UNRET_BEGIN		ANNOTATE type=ANNOTYPE_UNRET_BEGIN
-#define ANNOTATE_REACHABLE		ANNOTATE type=ANNOTYPE_REACHABLE
-#define ANNOTATE_NOCFI			ANNOTATE type=ANNOTYPE_NOCFI
-#define ANNOTATE_DATA_SPECIAL		ANNOTATE_DATA type=ANNOTYPE_DATA_SPECIAL
-#endif /* __ASSEMBLY__ */
+#endif /* !__ASSEMBLY__ */
+
+#else /* !OBJTOOL */
+
+#define ANNOTATE_NOENDBR
+#define ANNOTATE_NOENDBR_SYM(sym)
+#define ANNOTATE_RETPOLINE_SAFE
+#define ANNOTATE_INSTR_BEGIN(label)
+#define ANNOTATE_INSTR_END(label)
+#define ANNOTATE_IGNORE_ALTERNATIVE
+#define ANNOTATE_INTRA_FUNCTION_CALL
+#define ANNOTATE_UNRET_BEGIN
+#define ANNOTATE_REACHABLE
+#define ANNOTATE_REACHABLE_LABEL(label)
+#define ANNOTATE_NOCFI
+#define ANNOTATE_NOCFI_SYM(sym)
+#define ANNOTATE_DATA_SPECIAL
+#define __ANNOTATE_DATA_SPECIAL(l)
+
+#endif /* !OBJTOOL */
 
 #endif /* _LINUX_ANNOTATE_H */
-- 
2.52.0
Re: [PATCH 5/8] objtool: Convert annotations to assembler macros
Posted by Peter Zijlstra 1 week, 4 days ago 
On Sat, Dec 06, 2025 at 01:41:12PM -0800, Josh Poimboeuf wrote:
> Improve code generation readability by converting the objtool
> annotations into assembler macros which are created when annotate.h is
> included.
> 
> Before:
> 
>   .pushsection .discard.annotate_insn, "M", @progbits, 8; .long 1b - ., 8; .popsection
> 
> After:
> 
>   ANNOTATE_REACHABLE loc=1b
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

> diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
> index 0e8c611bc9e2..770321c908e5 100644
> --- a/arch/x86/include/asm/asm.h
> +++ b/arch/x86/include/asm/asm.h
> @@ -2,15 +2,15 @@
>  #ifndef _ASM_X86_ASM_H
>  #define _ASM_X86_ASM_H
>  
> -#include <linux/annotate.h>
> -
>  #ifdef __ASSEMBLER__
> +# define __ASM_C(a,b)			a
>  # define __ASM_FORM(x, ...)		x,## __VA_ARGS__
>  # define __ASM_FORM_RAW(x, ...)		x,## __VA_ARGS__
>  # define __ASM_FORM_COMMA(x, ...)	x,## __VA_ARGS__,
>  # define __ASM_REGPFX			%
>  #else
>  #include <linux/stringify.h>
> +# define __ASM_C(a,b)			b
>  # define __ASM_FORM(x, ...)		" " __stringify(x,##__VA_ARGS__) " "
>  # define __ASM_FORM_RAW(x, ...)		    __stringify(x,##__VA_ARGS__)
>  # define __ASM_FORM_COMMA(x, ...)	" " __stringify(x,##__VA_ARGS__) ","
> @@ -115,6 +115,10 @@
>  
>  #endif
>  
> +#define DEFINE_MACRO(name)						\
> +	__ASM_C(DEFINE_ ## name,					\
> +		asm(__stringify(DEFINE_ ## name)))
> +
>  #ifndef __ASSEMBLER__
>  static __always_inline __pure void *rip_rel_ptr(void *p)
>  {

> diff --git a/include/linux/annotate.h b/include/linux/annotate.h
> index 1678410efa1b..8b28f1a81ec4 100644
> --- a/include/linux/annotate.h
> +++ b/include/linux/annotate.h
> @@ -3,53 +3,43 @@
>  #define _LINUX_ANNOTATE_H
>  
>  #include <linux/objtool_types.h>
> +#include <linux/stringify.h>
> +#include <asm/asm.h>
> +
> +#define DEFINE___ANNOTATE						\
> +	.macro __ANNOTATE sec, type, loc;				\
> +	.pushsection __ASM_C(\sec, \\sec), "M", @progbits, 8;		\
> +		.long __ASM_C(\loc, \\loc) - .;				\
> +		.long __ASM_C(\type, \\type);				\
> +	.popsection;							\
> +	.endm
> +
> +#define __DEFINE_ANNOTATE(sec, name, type)				\
> +	.macro name loc=910b;						\
> +	910: __ANNOTATE sec, type, __ASM_C(\loc, \\loc);		\
> +	.endm
> +
> +#define DEFINE_ANNOTATE(type)						\
> +	__DEFINE_ANNOTATE(.discard.annotate_insn,			\
> +			  ANNOTATE_ ## type, ANNOTYPE_ ## type)
> +
> +#define DEFINE_ANNOTATE_DATA(type)					\
> +	__DEFINE_ANNOTATE(.discard.annotate_data,			\
> +			  ANNOTATE_ ## type, ANNOTYPE_ ## type)
>  
>  #ifdef CONFIG_OBJTOOL
>  
> +DEFINE_MACRO(__ANNOTATE);
> +DEFINE_MACRO(ANNOTATE(NOENDBR));
> +DEFINE_MACRO(ANNOTATE(RETPOLINE_SAFE));
> +DEFINE_MACRO(ANNOTATE(INSTR_BEGIN));
> +DEFINE_MACRO(ANNOTATE(INSTR_END));
> +DEFINE_MACRO(ANNOTATE(IGNORE_ALTERNATIVE));
> +DEFINE_MACRO(ANNOTATE(INTRA_FUNCTION_CALL));
> +DEFINE_MACRO(ANNOTATE(UNRET_BEGIN));
> +DEFINE_MACRO(ANNOTATE(REACHABLE));
> +DEFINE_MACRO(ANNOTATE(NOCFI));
> +DEFINE_MACRO(ANNOTATE_DATA(DATA_SPECIAL));

Well, that took a bit this Monday morning... :-)

Clever.
Re: [PATCH 5/8] objtool: Convert annotations to assembler macros
Posted by Josh Poimboeuf 1 week, 4 days ago 
On Sat, Dec 06, 2025 at 01:41:12PM -0800, Josh Poimboeuf wrote:
> Improve code generation readability by converting the objtool
> annotations into assembler macros which are created when annotate.h is
> included.
> 
> Before:
> 
>   .pushsection .discard.annotate_insn, "M", @progbits, 8; .long 1b - ., 8; .popsection
> 
> After:
> 
>   ANNOTATE_REACHABLE loc=1b
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

This needs the following to build on non-x86:

diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
index 770321c908e5..e63810bfdc68 100644
--- a/arch/x86/include/asm/asm.h
+++ b/arch/x86/include/asm/asm.h
@@ -3,14 +3,12 @@
 #define _ASM_X86_ASM_H
 
 #ifdef __ASSEMBLER__
-# define __ASM_C(a,b)			a
 # define __ASM_FORM(x, ...)		x,## __VA_ARGS__
 # define __ASM_FORM_RAW(x, ...)		x,## __VA_ARGS__
 # define __ASM_FORM_COMMA(x, ...)	x,## __VA_ARGS__,
 # define __ASM_REGPFX			%
 #else
 #include <linux/stringify.h>
-# define __ASM_C(a,b)			b
 # define __ASM_FORM(x, ...)		" " __stringify(x,##__VA_ARGS__) " "
 # define __ASM_FORM_RAW(x, ...)		    __stringify(x,##__VA_ARGS__)
 # define __ASM_FORM_COMMA(x, ...)	" " __stringify(x,##__VA_ARGS__) ","
@@ -115,10 +113,6 @@
 
 #endif
 
-#define DEFINE_MACRO(name)						\
-	__ASM_C(DEFINE_ ## name,					\
-		asm(__stringify(DEFINE_ ## name)))
-
 #ifndef __ASSEMBLER__
 static __always_inline __pure void *rip_rel_ptr(void *p)
 {
diff --git a/include/linux/annotate.h b/include/linux/annotate.h
index a80fef36dc92..a099a1d5e410 100644
--- a/include/linux/annotate.h
+++ b/include/linux/annotate.h
@@ -4,7 +4,7 @@
 
 #include <linux/objtool_types.h>
 #include <linux/stringify.h>
-#include <asm/asm.h>
+#include <linux/asm.h>
 
 #define DEFINE___ANNOTATE						\
 	.macro __ANNOTATE sec, type, loc;				\
diff --git a/include/linux/asm.h b/include/linux/asm.h
new file mode 100644
index 000000000000..94836aa217b4
--- /dev/null
+++ b/include/linux/asm.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_ASM_H
+#define _LINUX_ASM_H
+
+#ifdef __ASSEMBLER__
+# define __ASM_C(a,b) a
+#else
+# define __ASM_C(a,b) b
+#endif
+
+#define DEFINE_MACRO(name)						\
+	__ASM_C(DEFINE_ ## name,					\
+		asm(__stringify(DEFINE_ ## name)))
+
+#endif /* _LINUX_ASM_H */

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