Basic Clang PGO support

kpatch-build/create-diff-object.c

@@ -454,6 +454,14 @@ static bool rela_equal(struct rela *rela1, struct rela *rela2)
 	    !strcmp(rela2->sym->name, ".altinstr_aux"))
 		return true;
 
+	/*
+	 * __llvm_prf_cnts is used by clang PGO to store counters. Ignore
+	 * these to void unnecessary "changed function".
+	 */
+	if (!strcmp(rela1->sym->name, "__llvm_prf_cnts") &&
+	    !strcmp(rela2->sym->name, "__llvm_prf_cnts"))
+		return true;
+
 	/*
 	 * With -mcmodel=large on ppc64le, GCC might generate entries in the .toc
 	 * section for relocation symbol references.   The .toc offsets may change
@@ -986,6 +994,8 @@ 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)
 {
@@ -995,8 +1005,9 @@ 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) ?

kpatch-build/kpatch-build

@@ -677,9 +677,10 @@ 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="$(getopt -o ha:r:s:c:v:j:t:n:o:dR -l "help,archversion:,sourcerpm:,sourcedir:,config:,vmlinux:,jobs:,target:,name:,output:,oot-module:,oot-module-src:,debug,skip-gcc-check,skip-compiler-check,skip-cleanup,non-replace" -- "$@")" || die "getopt failed"
+options="$(getopt -o ha:r:s:c:v:j:t:n:o:dRp: -l "help,archversion:,sourcerpm:,sourcedir:,config:,vmlinux:,jobs:,target:,name:,output:,oot-module:,oot-module-src:,debug,skip-gcc-check,skip-compiler-check,skip-cleanup,non-replace,profile-data" -- "$@")" || die "getopt failed"
 
 eval set -- "$options"
 
@@ -761,6 +762,10 @@ 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"
@@ -1056,6 +1061,16 @@ fi
 
 if [[ -n "$CONFIG_CC_IS_CLANG" ]]; then
 	echo "WARNING: Clang support is experimental"
+	if [[ -z "$PROFILE_DATA" ]] && [[ -n "$CONFIG_PGO_CLANG" ]]; then
+		die "Please specify profile-data for CONFIG_PGO_CLANG"
+	fi
+	if [[ -n "$PROFILE_DATA" ]] && [[ -z "$CONFIG_PGO_CLANG" ]]; then
+		echo "WARNING profile-data specified w/o CONFIG_PGO_CLANG, ignore it"
+	fi
+else
+	if [[ -n "$PROFILE_DATA" ]]; then
+		die "Only supports profile-data with Clang"
+	fi
 fi
 
 if [[ "$SKIPCOMPILERCHECK" -eq 0 ]]; then
@@ -1107,6 +1122,9 @@ declare -a MAKEVARS
 if [[ -n "$CONFIG_CC_IS_CLANG" ]]; then
 	MAKEVARS+=("CC=${KPATCH_CC_PREFIX}${CLANG}")
 	MAKEVARS+=("HOSTCC=clang")
+	if [[ -n "$CONFIG_PGO_CLANG" ]]; then
+		MAKEVARS+=("LLVM=1 CFLAGS_PGO_CLANG=-fprofile-use=$PROFILE_DATA")
+	fi
 else
 	MAKEVARS+=("CC=${KPATCH_CC_PREFIX}${GCC}")
 fi

kpatch-build/lookup.c

@@ -91,11 +91,13 @@ static bool maybe_discarded_sym(const char *name)
 }
 
 static bool locals_match(struct lookup_table *table, int idx,
-			struct symbol *file_sym, struct list_head *sym_list)
+			 struct symbol *file_sym, struct list_head *sym_list,
+			 int match_pct)
 {
 	struct symbol *sym;
 	struct object_symbol *table_sym;
 	int i, found;
+	int match_cnt = 0, mismatch_cnt = 0;
 
 	i = idx + 1;
 	for_each_obj_symbol_continue(i, table_sym, table) {
@@ -121,10 +123,18 @@ static bool locals_match(struct lookup_table *table, int idx,
 			}
 		}
 
-		if (!found)
-			return false;
+		if (found)
+			match_cnt++;
+		else
+			mismatch_cnt++;
 	}
 
+	if (match_cnt * 100 < (match_cnt + mismatch_cnt) * match_pct)
+		return false;
+
+	match_cnt = 0;
+	mismatch_cnt = 0;
+
 	sym = file_sym;
 	list_for_each_entry_continue(sym, sym_list, list) {
 		if (sym->type == STT_FILE)
@@ -157,11 +167,13 @@ static bool locals_match(struct lookup_table *table, int idx,
 			}
 		}
 
-		if (!found)
-			return false;
+		if (found)
+			match_cnt++;
+		else
+			mismatch_cnt++;
 	}
 
-	return true;
+	return match_cnt * 100 >= (match_cnt + mismatch_cnt) * match_pct;
 }
 
 static void find_local_syms(struct lookup_table *table, struct symbol *file_sym,
@@ -176,7 +188,7 @@ static void find_local_syms(struct lookup_table *table, struct symbol *file_sym,
 			continue;
 		if (strcmp(file_sym->name, sym->name))
 			continue;
-		if (!locals_match(table, i, file_sym, sym_list))
+		if (!locals_match(table, i, file_sym, sym_list, 90 /* match_pct */))
 			continue;
 		if (lookup_table_file_sym)
 			ERROR("found duplicate matches for %s local symbols in %s symbol table",