From 3b4c6c6acfd781f34ce6318b1a80a800dd5c11ad Mon Sep 17 00:00:00 2001
From: Song Liu <songliubraving@fb.com>
Date: Wed, 13 Oct 2021 00:10:20 -0700
Subject: [PATCH 1/2] 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>
---
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 6a4848a2..c3b37dc3 100644
--- a/kpatch-build/create-diff-object.c
+++ b/kpatch-build/create-diff-object.c
@@ -957,6 +957,8 @@ 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)
{
@@ -966,8 +968,9 @@ 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_special_static(is_rela_section(sec_orig) ?
From 6d93e41500959170ca222cd17362a5dcfe2945f6 Mon Sep 17 00:00:00 2001
From: Song Liu <songliubraving@fb.com>
Date: Wed, 13 Oct 2021 01:03:55 -0700
Subject: [PATCH 2/2] kpatch-build: add support for clang pgo
For clang with Profile-Guided Optimization (PGO), profile data is needed
to compile the livepatch properly. Add option -p|--profile-data, which
specifies the profile data file. This option is only valid with
CONFIG_CC_IS_CLANG and CONFIG_PGO_CLANG.
Signed-off-by: Song Liu <songliubraving@fb.com>
---
kpatch-build/kpatch-build | 22 +++++++++++++++++++++-
1 file changed, 21 insertions(+), 1 deletion(-)
diff --git a/kpatch-build/kpatch-build b/kpatch-build/kpatch-build
index 3a9902e5..d8bee557 100755
--- a/kpatch-build/kpatch-build
+++ b/kpatch-build/kpatch-build
@@ -538,9 +538,10 @@ usage() {
echo " --skip-cleanup Skip post-build cleanup" >&2
echo " --skip-compiler-check Skip compiler version matching check" >&2
echo " (not recommended)" >&2
+ echo " -p, --profile-data specify profile data for PGO (clang only)" >&2
}
-options="$(getopt -o ha:r:s:c:v:j:t:n:o:de:R -l "help,archversion:,sourcerpm:,sourcedir:,config:,vmlinux:,jobs:,target:,name:,output:,oot-module:,debug,skip-gcc-check,skip-compiler-check,skip-cleanup,non-replace" -- "$@")" || die "getopt failed"
+options="$(getopt -o ha:r:s:c:v:j:t:n:o:de:Rp: -l "help,archversion:,sourcerpm:,sourcedir:,config:,vmlinux:,jobs:,target:,name:,output:,oot-module:,debug,skip-gcc-check,skip-compiler-check,skip-cleanup,non-replace,profile-data" -- "$@")" || die "getopt failed"
eval set -- "$options"
@@ -617,6 +618,10 @@ while [[ $# -gt 0 ]]; do
echo "WARNING: Skipping compiler version matching check (not recommended)"
SKIPCOMPILERCHECK=1
;;
+ -p|--profile-data)
+ PROFILE_DATA="$(readlink -f "$2")"
+ shift
+ ;;
*)
[[ "$1" = "--" ]] && shift && continue
[[ ! -f "$1" ]] && die "patch file '$1' not found"
@@ -835,6 +840,7 @@ CONFIG_JUMP_LABEL=0
CONFIG_MODVERSIONS=0
CONFIG_CC_IS_CLANG=0
CONFIG_LD_IS_LLD=0
+CONFIG_PGO_CLANG=0
if grep -q "CONFIG_LIVEPATCH=y" "$CONFIGFILE" && (kernel_is_rhel || kernel_version_gte 4.9.0); then
@@ -869,6 +875,7 @@ grep -q "CONFIG_JUMP_LABEL=y" "$CONFIGFILE" && CONFIG_JUMP_LABEL=1
grep -q "CONFIG_MODVERSIONS=y" "$CONFIGFILE" && CONFIG_MODVERSIONS=1
grep -q "CONFIG_CC_IS_CLANG=y" "$CONFIGFILE" && CONFIG_CC_IS_CLANG=1
grep -q "CONFIG_LD_IS_LLD=y" "$CONFIGFILE" && CONFIG_LD_IS_LLD=1
+grep -q "CONFIG_PGO_CLANG=y" "$CONFIGFILE" && CONFIG_PGO_CLANG=1
# unsupported kernel option checking
grep -q "CONFIG_DEBUG_INFO_SPLIT=y" "$CONFIGFILE" && die "kernel option 'CONFIG_DEBUG_INFO_SPLIT' not supported"
@@ -891,6 +898,16 @@ fi
if [[ "$CONFIG_CC_IS_CLANG" -eq 1 ]]; then
echo "WARNING: Clang support is experimental"
+ if [[ -z "$PROFILE_DATA" ]] && [[ "$CONFIG_PGO_CLANG" -eq 1 ]]; then
+ die "Please specify profile-data for CONFIG_PGO_CLANG"
+ fi
+ if [[ -n "$PROFILE_DATA" ]] && [[ "$CONFIG_PGO_CLANG" -eq 0 ]]; then
+ echo "WARNING profile-data specified w/o CONFIG_PGO_CLANG, ignore it"
+ fi
+else
+ if [[ -n "$PROFILE_DATA" ]]; then
+ die "Only supports profile-data with Clang"
+ fi
fi
if [[ "$SKIPCOMPILERCHECK" -eq 0 ]]; then
@@ -937,6 +954,9 @@ declare -a MAKEVARS
if [ "$CONFIG_CC_IS_CLANG" -eq 1 ]; then
MAKEVARS+=("CC=${KPATCH_CC_PREFIX}clang")
MAKEVARS+=("HOSTCC=clang")
+ if [[ "$CONFIG_PGO_CLANG" -eq 1 ]]; then
+ MAKEVARS+=("CFLAGS_PGO_CLANG=-fprofile-use=$PROFILE_DATA")
+ fi
else
MAKEVARS+=("CC=${KPATCH_CC_PREFIX}gcc")
fi