The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     d4888d58041d1a61d66f2c81cb398f9685bc7576
Gitweb:        https://git.kernel.org/tip/d4888d58041d1a61d66f2c81cb398f9685bc7576
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Fri, 03 Apr 2026 13:09:34 -07:00
Committer:     Josh Poimboeuf <jpoimboe@kernel.org>
CommitterDate: Mon, 04 May 2026 21:16:05 -07:00

klp-build: Use "objtool klp checksum" subcommand

Use the new "objtool klp checksum" subcommand instead of injecting
--checksum into every objtool invocation via OBJTOOL_ARGS during the
kernel build.

This decouples checksum generation from the build, running it in
separate post-build passes, making the code (and the patch generation
pipeline itself) more modular.

Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 scripts/livepatch/klp-build | 95 ++++++++++++++++++++++++------------
 1 file changed, 65 insertions(+), 30 deletions(-)

diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
index 215d230..6103345 100755
--- a/scripts/livepatch/klp-build
+++ b/scripts/livepatch/klp-build
@@ -37,10 +37,12 @@ OBJTOOL="$PWD/tools/objtool/objtool"
 CONFIG="$PWD/.config"
 TMP_DIR="$PWD/klp-tmp"
 
-ORIG_DIR="$TMP_DIR/orig"
-PATCHED_DIR="$TMP_DIR/patched"
-DIFF_DIR="$TMP_DIR/diff"
-KMOD_DIR="$TMP_DIR/kmod"
+ORIG_DIR="$TMP_DIR/1-orig"
+PATCHED_DIR="$TMP_DIR/2-patched"
+ORIG_CSUM_DIR="$TMP_DIR/3-checksum-orig"
+PATCHED_CSUM_DIR="$TMP_DIR/3-checksum-patched"
+DIFF_DIR="$TMP_DIR/4-diff"
+KMOD_DIR="$TMP_DIR/5-kmod"
 
 STASH_DIR="$TMP_DIR/stash"
 TIMESTAMP="$TMP_DIR/timestamp"
@@ -136,10 +138,11 @@ Options:
 Advanced Options:
    -d, --debug			Show symbol/reloc cloning decisions
    -S, --short-circuit=STEP	Start at build step (requires prior --keep-tmp)
-				   1|orig	Build original kernel (default)
-				   2|patched	Build patched kernel
-				   3|diff	Diff objects
-				   4|kmod	Build patch module
+				   1|orig		Build original kernel (default)
+				   2|patched		Build patched kernel
+				   3|checksum		Generate checksums
+				   4|diff		Diff objects
+				   5|kmod		Build patch module
    -T, --keep-tmp		Preserve tmp dir on exit
 
 EOF
@@ -203,10 +206,11 @@ process_args() {
 				[[ ! -d "$TMP_DIR" ]] && die "--short-circuit requires preserved klp-tmp dir"
 				keep_tmp=1
 				case "$2" in
-					1 | orig)	SHORT_CIRCUIT=1; ;;
-					2 | patched)	SHORT_CIRCUIT=2; ;;
-					3 | diff)	SHORT_CIRCUIT=3; ;;
-					4 | mod)	SHORT_CIRCUIT=4; ;;
+					1 | orig)		SHORT_CIRCUIT=1; ;;
+					2 | patched)		SHORT_CIRCUIT=2; ;;
+					3 | checksum)		SHORT_CIRCUIT=3; ;;
+					4 | diff)		SHORT_CIRCUIT=4; ;;
+					5 | kmod)		SHORT_CIRCUIT=5; ;;
 					*)		die "invalid short-circuit step '$2'" ;;
 				esac
 				shift 2
@@ -513,11 +517,8 @@ clean_kernel() {
 build_kernel() {
 	local build="$1"
 	local log="$TMP_DIR/build.log"
-	local objtool_args=()
 	local cmd=()
 
-	objtool_args=("--checksum")
-
 	cmd=("make")
 
 	# When a patch to a kernel module references a newly created unexported
@@ -544,7 +545,6 @@ build_kernel() {
 	fi
 	cmd+=("-j$JOBS")
 	cmd+=("KCFLAGS=-ffunction-sections -fdata-sections")
-	cmd+=("OBJTOOL_ARGS=${objtool_args[*]}")
 	cmd+=("vmlinux")
 	cmd+=("modules")
 
@@ -574,7 +574,7 @@ copy_orig_objects() {
 
 	find_objects | mapfile -t files
 
-	xtrace_save "copying orig objects"
+	xtrace_save "copying original objects"
 	for _file in "${files[@]}"; do
 		local rel_file="${_file/.ko/.o}"
 		local file="$PWD/$rel_file"
@@ -630,6 +630,35 @@ copy_patched_objects() {
 	mv -f "$TMP_DIR/build.log" "$PATCHED_DIR"
 }
 
+# Copy .o files to a separate directory and run "objtool klp checksum" on each
+# copy.  The checksums are written to a .discard.sym_checksum section.
+#
+# If match_dir is given, only process files which also exist there.
+generate_checksums() {
+	local src_dir="$1"
+	local dest_dir="$2"
+	local match_dir="${3:-}"
+	local files=()
+	local file
+
+	rm -rf "$dest_dir"
+	mkdir -p "$dest_dir"
+
+	find "$src_dir" -type f -name "*.o" | mapfile -t files
+	for file in "${files[@]}"; do
+		local rel="${file#"$src_dir"/}"
+		local dest="$dest_dir/$rel"
+
+		[[ -n "$match_dir" && ! -f "$match_dir/$rel" ]] && continue
+
+		mkdir -p "$(dirname "$dest")"
+		cp -f "$file" "$dest"
+		"$OBJTOOL" klp checksum "$dest"
+	done
+
+	touch "$dest_dir/.complete"
+}
+
 # Diff changed objects, writing output object to $DIFF_DIR
 diff_objects() {
 	local log="$KLP_DIFF_LOG"
@@ -639,16 +668,16 @@ diff_objects() {
 	rm -rf "$DIFF_DIR"
 	mkdir -p "$DIFF_DIR"
 
-	find "$PATCHED_DIR" -type f -name "*.o" | mapfile -t files
+	find "$PATCHED_CSUM_DIR" -type f -name "*.o" | mapfile -t files
 	[[ ${#files[@]} -eq 0 ]] && die "no changes detected"
 
 	[[ -v DEBUG_CLONE ]] && opts=("--debug")
 
 	# Diff all changed objects
 	for file in "${files[@]}"; do
-		local rel_file="${file#"$PATCHED_DIR"/}"
+		local rel_file="${file#"$PATCHED_CSUM_DIR"/}"
 		local orig_file="$rel_file"
-		local patched_file="$PATCHED_DIR/$rel_file"
+		local patched_file="$PATCHED_CSUM_DIR/$rel_file"
 		local out_file="$DIFF_DIR/$rel_file"
 		local filter=()
 		local cmd=()
@@ -672,8 +701,8 @@ diff_objects() {
 		fi
 
 		(
-			cd "$ORIG_DIR"
-			[[ -v VERBOSE ]] && echo "cd $ORIG_DIR && ${cmd[*]}"
+			cd "$ORIG_CSUM_DIR"
+			[[ -v VERBOSE ]] && echo "cd $ORIG_CSUM_DIR && ${cmd[*]}"
 			"${cmd[@]}"							\
 				1> >(tee -a "$log")					\
 				2> >(tee -a "$log" | "${filter[@]}" >&2) ||		\
@@ -682,9 +711,9 @@ diff_objects() {
 	done
 }
 
-# For each changed object, run objtool with --debug-checksum to get the
-# per-instruction checksums, and then diff those to find the first changed
-# instruction for each function.
+# For each changed object, run "objtool klp checksum" with --debug-checksum to
+# get the per-instruction checksums, and then diff those to find the first
+# changed instruction for each function.
 diff_checksums() {
 	local orig_log="$ORIG_DIR/checksum.log"
 	local patched_log="$PATCHED_DIR/checksum.log"
@@ -709,8 +738,7 @@ diff_checksums() {
 	done
 
 	cmd=("$OBJTOOL")
-	cmd+=("--checksum")
-	cmd+=("--link")
+	cmd+=("klp" "checksum")
 	cmd+=("--dry-run")
 
 	for file in "${!funcs[@]}"; do
@@ -719,11 +747,11 @@ diff_checksums() {
 		(
 			cd "$ORIG_DIR"
 			"${cmd[@]}" "$opt" "$file" &> "$orig_log" || \
-				( cat "$orig_log" >&2; die "objtool --debug-checksum failed" )
+				( cat "$orig_log" >&2; die "objtool klp checksum failed" )
 
 			cd "$PATCHED_DIR"
 			"${cmd[@]}" "$opt" "$file" &> "$patched_log" ||	\
-				( cat "$patched_log" >&2; die "objtool --debug-checksum failed" )
+				( cat "$patched_log" >&2; die "objtool klp checksum failed" )
 		)
 
 		for func in ${funcs[$file]}; do
@@ -861,6 +889,13 @@ if (( SHORT_CIRCUIT <= 2 )); then
 fi
 
 if (( SHORT_CIRCUIT <= 3 )); then
+	status "Generating original checksums"
+	generate_checksums "$ORIG_DIR" "$ORIG_CSUM_DIR" "$PATCHED_DIR"
+	status "Generating patched checksums"
+	generate_checksums "$PATCHED_DIR" "$PATCHED_CSUM_DIR"
+fi
+
+if (( SHORT_CIRCUIT <= 4 )); then
 	status "Diffing objects"
 	diff_objects
 	if [[ -v DIFF_CHECKSUM ]]; then
@@ -869,7 +904,7 @@ if (( SHORT_CIRCUIT <= 3 )); then
 	fi
 fi
 
-if (( SHORT_CIRCUIT <= 4 )); then
+if (( SHORT_CIRCUIT <= 5 )); then
 	status "Building patch module: $OUTFILE"
 	build_patch_module
 fi