[PATCH RFC 5/5] objtool: Improve code generation readability
From: Josh Poimboeuf
Date: Tue Apr 08 2025 - 04:22:31 EST
Improve the readability and compactness of the objtool annotations.
This makes it easier to see them and differentiate from other code.
Before:
-------
911:
.pushsection .discard.annotate_insn,"M",@progbits,8
.long 911b - .
.long 1
.popsection
After:
------
# <ANNOTATE_NOENDBR>
911: .pushsection .discard.annotate_insn,"M",@progbits,8; .long 911b - .; .long 1; .popsection
# </ANNOTATE_NOENDBR>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
include/linux/objtool.h | 97 ++++++++++++++++++++---------------------
1 file changed, 47 insertions(+), 50 deletions(-)
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 366ad004d794..66549603147e 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -8,19 +8,31 @@
#include <asm/asm.h>
+#define __UNWIND_HINT(label, type, sp_reg, sp_offset, signal) \
+ .pushsection .discard.unwind_hints; \
+ /* struct unwind_hint */ \
+ .long label - .; \
+ .short sp_offset; \
+ .byte sp_reg; \
+ .byte type; \
+ .byte signal; \
+ .balign 4; \
+ .popsection
+
+#define __ASM_ANNOTATE(label, type) \
+ .pushsection .discard.annotate_insn,"M",@progbits,8; \
+ .long label - .; \
+ .long type; \
+ .popsection
+
#ifndef __ASSEMBLY__
-#define UNWIND_HINT(type, sp_reg, sp_offset, signal) \
- "987: \n\t" \
- ".pushsection .discard.unwind_hints\n\t" \
- /* struct unwind_hint */ \
- ".long 987b - .\n\t" \
- ".short " __stringify(sp_offset) "\n\t" \
- ".byte " __stringify(sp_reg) "\n\t" \
- ".byte " __stringify(type) "\n\t" \
- ".byte " __stringify(signal) "\n\t" \
- ".balign 4 \n\t" \
- ".popsection\n\t"
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal) \
+ "\n# <UNWIND_HINT>\n" \
+ "987: " \
+ __stringify(__UNWIND_HINT(987b, type, sp_reg, \
+ sp_offset, signal)) \
+ "\n# </UNWIND_HINT>\n\t"
/*
* This macro marks the given function's stack frame as "non-standard", which
@@ -45,23 +57,18 @@
#define STACK_FRAME_NON_STANDARD_FP(func)
#endif
-#define ASM_REACHABLE \
- "998:\n\t" \
- ".pushsection .discard.reachable\n\t" \
- ".long 998b\n\t" \
- ".popsection\n\t"
-
#define __ASM_BREF(label) label ## b
-#define __ASM_ANNOTATE(label, type) \
- ".pushsection .discard.annotate_insn,\"M\",@progbits,8\n\t" \
- ".long " __stringify(label) " - .\n\t" \
- ".long " __stringify(type) "\n\t" \
- ".popsection\n\t"
-
#define ASM_ANNOTATE(type) \
- "911:\n\t" \
- __ASM_ANNOTATE(911b, type)
+ "\n# <ANNOTATE_" __stringify(type) ">\n" \
+ "911:\t" \
+ __stringify(__ASM_ANNOTATE(911b, __PASTE(ANNOTYPE_, type))) \
+ "\n# </ANNOTATE_" __stringify(type) ">\n\t"
+
+#define ASM_ANNOTATE_LABEL(label, type) \
+ "\n# BEGIN ANNOTATE_" __stringify(type) "\n" \
+ __stringify(__ASM_ANNOTATE(label, __PASTE(ANNOTYPE_, type))) \
+ "\n# </ANNOTATE_" __stringify(type) "\n\t"
#else /* __ASSEMBLY__ */
@@ -88,15 +95,7 @@
*/
.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0
.Lhere_\@:
- .pushsection .discard.unwind_hints
- /* struct unwind_hint */
- .long .Lhere_\@ - .
- .short \sp_offset
- .byte \sp_reg
- .byte \type
- .byte \signal
- .balign 4
- .popsection
+ __UNWIND_HINT(.Lhere_\@, \type, \sp_reg, \sp_offset, \signal)
.endm
.macro STACK_FRAME_NON_STANDARD func:req
@@ -113,10 +112,7 @@
.macro ANNOTATE type:req
.Lhere_\@:
- .pushsection .discard.annotate_insn,"M",@progbits,8
- .long .Lhere_\@ - .
- .long \type
- .popsection
+ __ASM_ANNOTATE(.Lhere_\@, \type)
.endm
#endif /* __ASSEMBLY__ */
@@ -125,11 +121,12 @@
#ifndef __ASSEMBLY__
-#define UNWIND_HINT(type, sp_reg, sp_offset, signal) "\n\t"
#define STACK_FRAME_NON_STANDARD(func)
#define STACK_FRAME_NON_STANDARD_FP(func)
-#define __ASM_ANNOTATE(label, type) ""
-#define ASM_ANNOTATE(type)
+
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal) ""
+#define ASM_ANNOTATE(type) ""
+#define ASM_ANNOTATE_LABEL(sym, type) ""
#else
.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0
.endm
@@ -146,30 +143,30 @@
* 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(sym, ANNOTYPE_NOENDBR))
+#define ANNOTATE_NOENDBR ASM_ANNOTATE(NOENDBR)
+#define ANNOTATE_NOENDBR_SYM(sym) asm(ASM_ANNOTATE_LABEL(sym, NOENDBR))
/*
* 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 ASM_ANNOTATE(RETPOLINE_SAFE)
/*
* See linux/instrumentation.h
*/
-#define ANNOTATE_INSTR_BEGIN(label) __ASM_ANNOTATE(label, ANNOTYPE_INSTR_BEGIN)
-#define ANNOTATE_INSTR_END(label) __ASM_ANNOTATE(label, ANNOTYPE_INSTR_END)
+#define ANNOTATE_INSTR_BEGIN(label) ASM_ANNOTATE_LABEL(label, INSTR_BEGIN)
+#define ANNOTATE_INSTR_END(label) ASM_ANNOTATE_LABEL(label, INSTR_END)
/*
* objtool annotation to ignore the alternatives and only consider the original
* instruction(s).
*/
-#define ANNOTATE_IGNORE_ALTERNATIVE ASM_ANNOTATE(ANNOTYPE_IGNORE_ALTS)
+#define ANNOTATE_IGNORE_ALTERNATIVE ASM_ANNOTATE(IGNORE_ALTS)
/*
* 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 ASM_ANNOTATE(INTRA_FUNCTION_CALL)
/*
* Use objtool to validate the entry requirement that all code paths do
* VALIDATE_UNRET_END before RET.
@@ -177,13 +174,13 @@
* 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 ASM_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) __ASM_ANNOTATE(label, ANNOTYPE_REACHABLE)
+#define ANNOTATE_REACHABLE(label) ASM_ANNOTATE_LABEL(label, REACHABLE)
#else
#define ANNOTATE_NOENDBR ANNOTATE type=ANNOTYPE_NOENDBR
--
2.49.0