Re: [PATCH v2 03/12] klp-build: Move patch processing to klp-prepare-patch

[Josh Poimboeuf <jpoimboe@kernel.org>]

On Wed, Oct 28, 2026 at 02:45:25PM -0700, Song Liu wrote:
> -apply_patches() {
> -	local patch
> -
> -	for patch in "${PATCHES[@]}"; do
> -		apply_patch "$patch"
> -	done
> -}
> -
>  revert_patches() {
>  	local patches=("${APPLIED_PATCHES[@]}")
>  

I think we can remove even more cruft:

diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
index 4796b36b5cc8e..b93e1227b4c03 100755
--- a/scripts/livepatch/klp-build
+++ b/scripts/livepatch/klp-build
@@ -19,7 +19,7 @@ set -o nounset
 # This helps keep execution in pipes so pipefail+ERR trap can catch errors.
 shopt -s lastpipe
 
-unset DEBUG_CLONE DIFF_CHECKSUM SKIP_CLEANUP VERBOSE XTRACE
+unset DEBUG_CLONE DIFF_CHECKSUM PATCH_APPLIED SKIP_CLEANUP VERBOSE XTRACE
 
 REPLACE=1
 SHORT_CIRCUIT=0
@@ -110,7 +110,7 @@ restore_files() {
 
 cleanup() {
 	set +o nounset
-	revert_patches
+	revert_patch
 	restore_files
 	[[ "$KEEP_TMP" -eq 0 ]] && rm -rf "$TMP_DIR"
 	return 0
@@ -329,50 +329,14 @@ set_kernelversion() {
 }
 
 apply_patch() {
-	local patch="$1"
-	shift
-	local extra_args=("$@")
-	local drift_regex="with fuzz|offset [0-9]+ line"
-	local output
-	local status
-
-	[[ ! -f "$patch" ]] && die "$patch doesn't exist"
-	status=0
-	output=$(patch -p1 --dry-run --no-backup-if-mismatch -r /dev/null "${extra_args[@]}" < "$patch" 2>&1) || status=$?
-	if [[ "$status" -ne 0 ]]; then
-		echo "$output" >&2
-		die "$patch did not apply"
-	elif [[ "$output" =~ $drift_regex ]]; then
-		[[ -v VERBOSE ]] && echo "$output" >&2
-		warn "${patch} applied with fuzz"
-	fi
-
-	APPLIED_PATCHES+=("$patch")
-	patch -p1 --no-backup-if-mismatch -r /dev/null "${extra_args[@]}" --silent < "$patch"
+	PATCH_APPLIED=1
+	patch -p1 --no-backup-if-mismatch -r /dev/null --silent < "$COMBINED_PATCH"
 }
 
 revert_patch() {
-	local patch="$1"
-	local tmp=()
-
-	patch -p1 -R --force --no-backup-if-mismatch -r /dev/null &> /dev/null < "$patch" || true
-
-	for p in "${APPLIED_PATCHES[@]}"; do
-		[[ "$p" == "$patch" ]] && continue
-		tmp+=("$p")
-	done
-
-	APPLIED_PATCHES=("${tmp[@]}")
-}
-
-revert_patches() {
-	local patches=("${APPLIED_PATCHES[@]}")
-
-	for (( i=${#patches[@]}-1 ; i>=0 ; i-- )) ; do
-		revert_patch "${patches[$i]}"
-	done
-
-	APPLIED_PATCHES=()
+	[[ -v PATCH_APPLIED ]] || return 0
+	patch -p1 -R --force --no-backup-if-mismatch -r /dev/null &> /dev/null < "$COMBINED_PATCH" || true
+	unset PATCH_APPLIED
 }
 
 do_init() {
@@ -397,8 +361,6 @@ do_init() {
 	(( SHORT_CIRCUIT <= 1 )) && rm -rf "$TMP_DIR"
 	mkdir -p "$TMP_DIR"
 
-	APPLIED_PATCHES=()
-
 	[[ -x "$PREPARE_PATCH" ]] || die "can't find klp-prepare-patch"
 
 	validate_config
@@ -806,10 +768,10 @@ if (( SHORT_CIRCUIT <= 1 )); then
 fi
 
 if (( SHORT_CIRCUIT <= 2 )); then
-	apply_patch "$COMBINED_PATCH" "--silent"
+	apply_patch
 	status "Building patched kernel"
 	build_kernel "patched"
-	revert_patches
+	revert_patch
 	status "Copying patched object files"
 	copy_patched_objects
 fi