[PATCH RFC 3/5] noinstr: Use asm_inline() in instrumentation_{begin,end}()

From: Josh Poimboeuf
Date: Tue Apr 08 2025 - 04:23:53 EST


Use asm_inline() to prevent the compiler from making poor inlining
decisions based on the length of the objtool annotations.

For a defconfig kernel built with GCC 14.2.1, bloat-o-meter reports a
0.18% text size increase:

add/remove: 88/433 grow/shrink: 967/487 up/down: 87579/-52630 (34949)
Total: Before=19448407, After=19483356, chg +0.18%

Presumably the text growth is due to increased inlining. A net total of
345 functions were removed.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
include/linux/instrumentation.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/instrumentation.h b/include/linux/instrumentation.h
index bf675a8aef8a..b1007407d272 100644
--- a/include/linux/instrumentation.h
+++ b/include/linux/instrumentation.h
@@ -9,7 +9,7 @@

/* Begin/end of an instrumentation safe region */
#define __instrumentation_begin(c) ({ \
- asm volatile(__stringify(c) ": nop\n\t" \
+ asm_inline volatile(__stringify(c) ": nop\n\t" \
ANNOTATE_INSTR_BEGIN(__ASM_BREF(c)) \
: : "i" (c)); \
})
@@ -47,7 +47,7 @@
* part of the condition block and does not escape.
*/
#define __instrumentation_end(c) ({ \
- asm volatile(__stringify(c) ": nop\n\t" \
+ asm_inline volatile(__stringify(c) ": nop\n\t" \
ANNOTATE_INSTR_END(__ASM_BREF(c)) \
: : "i" (c)); \
})
--
2.49.0