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klp-build: Use "objtool klp checksum" subcommand

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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>
This commit is contained in:
Josh Poimboeuf
2026-04-03 13:09:34 -07:00
parent e10764614a
commit d4888d5804
1 changed files with 65 additions and 30 deletions
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95
scripts/livepatch/klp-build
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@@ -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