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From ce97c8ef720bd288fbc53aad51969571a1c2c1e6 Mon Sep 17 00:00:00 2001
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From: Song Liu <songliubraving@fb.com>
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Date: Wed, 13 Oct 2021 00:10:20 -0700
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Subject: [PATCH 107/108] create-diff-object: compare section name with
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kpatch_section_function_name
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Profile-Guided Optimization (PGO) uses profiling data to help the compiler
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to evaluate the properties of a function, and thus adds different prefixes
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to the section/function. For example, with -ffunction-sections, the
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compiler will prefix some sectiones with .text.unlikely. However, if a
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function changes from the version in the profiling data, the compiler may
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ignore the profiling data. This often happens to the patched function
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when kpatch-build builds the patch. As a result, the original function
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and the patch function may have different prefix, i.e., one of them has
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.text, the other has .text.unlikely.
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To correlate these functions properly, use kpatch_section_function_name()
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in kpatch_correlate_sections() to find matching sections.
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Signed-off-by: Song Liu <songliubraving@fb.com>
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---
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kpatch-build/create-diff-object.c | 7 +++++--
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1 file changed, 5 insertions(+), 2 deletions(-)
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diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c
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index 1967bd8..6f08c4d 100644
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--- a/kpatch-build/create-diff-object.c
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+++ b/kpatch-build/create-diff-object.c
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@@ -986,6 +986,8 @@ static void kpatch_correlate_section(struct section *sec_orig,
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kpatch_correlate_symbol(sec_orig->sym, sec_patched->sym);
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}
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+static char *kpatch_section_function_name(struct section *sec);
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+
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static void kpatch_correlate_sections(struct list_head *seclist_orig,
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struct list_head *seclist_patched)
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{
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@@ -995,8 +997,9 @@ static void kpatch_correlate_sections(struct list_head *seclist_orig,
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if (sec_orig->twin)
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continue;
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list_for_each_entry(sec_patched, seclist_patched, list) {
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- if (kpatch_mangled_strcmp(sec_orig->name, sec_patched->name) ||
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- sec_patched->twin)
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+ if (sec_patched->twin ||
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+ kpatch_mangled_strcmp(kpatch_section_function_name(sec_orig),
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+ kpatch_section_function_name(sec_patched)))
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continue;
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if (is_special_static(is_rela_section(sec_orig) ?
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--
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2.37.3
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