From 9633ff14e80449b2001d6e49884fce896e1ffd41 Mon Sep 17 00:00:00 2001

From: Song Liu <songliubraving@fb.com>

Date: Wed, 13 Oct 2021 00:10:20 -0700

Subject: [PATCH 109/118] create-diff-object: compare section name with

 kpatch_section_function_name

Profile-Guided Optimization (PGO) uses profiling data to help the compiler

to evaluate the properties of a function, and thus adds different prefixes

to the section/function. For example, with -ffunction-sections, the

compiler will prefix some sectiones with .text.unlikely. However, if a

function changes from the version in the profiling data, the compiler may

ignore the profiling data. This often happens to the patched function

when kpatch-build builds the patch. As a result, the original function

and the patch function may have different prefix, i.e., one of them has

.text, the other has .text.unlikely.

To correlate these functions properly, use kpatch_section_function_name()

in kpatch_correlate_sections() to find matching sections.

Signed-off-by: Song Liu <songliubraving@fb.com>

(cherry picked from commit 47d1b39ba7686e2368c1ad24af274dfd9f54ecf9)

---

 kpatch-build/create-diff-object.c | 7 +++++--

 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c

index 22a0155..61e1477 100644

--- a/kpatch-build/create-diff-object.c

+++ b/kpatch-build/create-diff-object.c

@@ -1101,6 +1101,8 @@ static void kpatch_correlate_section(struct section *sec_orig,

 		kpatch_correlate_symbol(sec_orig->sym, sec_patched->sym);

 }

+static char *kpatch_section_function_name(struct section *sec);

+

 static void kpatch_correlate_sections(struct list_head *seclist_orig,

 		struct list_head *seclist_patched)

 {

@@ -1110,8 +1112,9 @@ static void kpatch_correlate_sections(struct list_head *seclist_orig,

 		if (sec_orig->twin)

 			continue;

 		list_for_each_entry(sec_patched, seclist_patched, list) {

-			if (kpatch_mangled_strcmp(sec_orig->name, sec_patched->name) ||

-			    sec_patched->twin)

+			if (sec_patched->twin ||

+			    kpatch_mangled_strcmp(kpatch_section_function_name(sec_orig),

+						  kpatch_section_function_name(sec_patched)))

 				continue;

 			if (is_ubsan_sec(sec_orig->name))

-- 

2.48.1