[PATCH v6 4/7] Add markers for text_unlikely and text_hot sections

Rong Xu
2024-10-26T05:14:22Z

Add markers like __hot_text_start, __hot_text_end, __unlikely_text_start,
and __unlikely_text_end which will be included in System.map. These markers
indicate how the compiler groups functions, providing valuable information
to developers about the layout and optimization of the code.

Co-developed-by: Han Shen <shenhan@google.com>
Signed-off-by: Han Shen <shenhan@google.com>
Signed-off-by: Rong Xu <xur@google.com>
Suggested-by: Sriraman Tallam <tmsriram@google.com>
Tested-by: Yonghong Song <yonghong.song@linux.dev>
Tested-by: Yabin Cui <yabinc@google.com>
Change-Id: Ie7688587adf89a14661ceca108680903b546d5d9
---
include/asm-generic/vmlinux.lds.h | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index fd901951549c0..e02973f3b4189 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -549,6 +549,16 @@
__cpuidle_text_end = .; \
__noinstr_text_end = .;

+#define TEXT_UNLIKELY \
+ __unlikely_text_start = .; \
+ *(.text.unlikely .text.unlikely.*) \
+ __unlikely_text_end = .;
+
+#define TEXT_HOT \
+ __hot_text_start = .; \
+ *(.text.hot .text.hot.*) \
+ __hot_text_end = .;
+
/*
* .text section. Map to function alignment to avoid address changes
* during second ld run in second ld pass when generating System.map
@@ -565,9 +575,9 @@
ALIGN_FUNCTION(); \
*(.text.asan.* .text.tsan.*) \
*(.text.unknown .text.unknown.*) \
- *(.text.unlikely .text.unlikely.*) \
+ TEXT_UNLIKELY \
. = ALIGN(PAGE_SIZE); \
- *(.text.hot .text.hot.*) \
+ TEXT_HOT \
*(TEXT_MAIN .text.fixup) \
NOINSTR_TEXT \
*(.ref.text)
--
2.47.0.163.g1226f6d8fa-goog