livepatch/klp-build: Add --show-first-changed option to show function divergence

Add a --show-first-changed option to identify where changed functions begin to diverge: - Parse 'objtool klp diff' output to find changed functions. - Run objtool again on each object with --debug-checksum=<funcs>. - Diff the per-instruction checksum debug output to locate the first differing instruction. This can be useful for quickly determining where and why a function changed.

Josh Poimboeuf committed 1 year ago

Commit 78be9fa1 parent 2c2f0b81 file · +78 −4Browse files

Showing the changes to scripts/livepatch (1 of 1 file). Show all

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scripts/livepatch/klp-build+78−4

@@ -20,7 +20,7 @@ set -o nounset · 19 unmodified lines
20	# This helps keep execution in pipes so pipefail+errexit can catch errors.	20	# This helps keep execution in pipes so pipefail+errexit can catch errors.
21	shopt -s lastpipe	21	shopt -s lastpipe
22		22
23	unset DEBUG_CLONE SKIP_CLEANUP XTRACE	23	unset DEBUG_CLONE DIFF_CHECKSUM SKIP_CLEANUP XTRACE
24		24
25	REPLACE=1	25	REPLACE=1
26	SHORT_CIRCUIT=0	26	SHORT_CIRCUIT=0
@@ -114,6 +114,7 @@ Usage: $SCRIPT [OPTIONS] PATCH_FILE(s) · 87 unmodified lines
114	Generate a livepatch module.	114	Generate a livepatch module.
115		115
116	Options:	116	Options:
		117	-f, --show-first-changed Show address of first changed instruction
117	-j, --jobs=<jobs> Build jobs to run simultaneously [default: $JOBS]	118	-j, --jobs=<jobs> Build jobs to run simultaneously [default: $JOBS]
118	-o, --output=<file.ko> Output file [default: livepatch-<patch-name>.ko]	119	-o, --output=<file.ko> Output file [default: livepatch-<patch-name>.ko]
119	--no-replace Disable livepatch atomic replace	120	--no-replace Disable livepatch atomic replace
@@ -141,8 +142,8 @@ process_args() { · 21 unmodified lines
141	local long	142	local long
142	local args	143	local args
143		144
144	short="hj:o:vdS:T"	145	short="hfj:o:vdS:T"
145	long="help,jobs:,output:,no-replace,verbose,debug,short-circuit:,keep-tmp"	146	long="help,show-first-changed,jobs:,output:,no-replace,verbose,debug,short-circuit:,keep-tmp"
146		147
147	args=$(getopt --options "$short" --longoptions "$long" -- "$@") \|\| {	148	args=$(getopt --options "$short" --longoptions "$long" -- "$@") \|\| {
148	echo; usage; exit	149	echo; usage; exit
@@ -155,6 +156,10 @@ process_args() { · 6 unmodified lines
155	usage	156	usage
156	exit 0	157	exit 0
157	;;	158	;;
		159	-f \| --show-first-changed)
		160	DIFF_CHECKSUM=1
		161	shift
		162	;;
158	-j \| --jobs)	163	-j \| --jobs)
159	JOBS="$2"	164	JOBS="$2"
160	shift 2	165	shift 2
@@ -618,6 +623,7 @@ diff_objects() { · 457 unmodified lines
618	local orig_file="$rel_file"	623	local orig_file="$rel_file"
619	local patched_file="$PATCHED_DIR/$rel_file"	624	local patched_file="$PATCHED_DIR/$rel_file"
620	local out_file="$DIFF_DIR/$rel_file"	625	local out_file="$DIFF_DIR/$rel_file"
		626	local filter=()
621	local cmd=()	627	local cmd=()
622		628
623	mkdir -p "$(dirname "$out_file")"	629	mkdir -p "$(dirname "$out_file")"
@@ -630,16 +636,80 @@ diff_objects() { · 6 unmodified lines
630	cmd+=("$patched_file")	636	cmd+=("$patched_file")
631	cmd+=("$out_file")	637	cmd+=("$out_file")
632		638
		639	if [[ -v DIFF_CHECKSUM ]]; then
		640	filter=("grep0")
		641	filter+=("-Ev")
		642	filter+=("DEBUG: .*checksum: ")
		643	else
		644	filter=("cat")
		645	fi
		646
633	(	647	(
634	cd "$ORIG_DIR"	648	cd "$ORIG_DIR"
635	"${cmd[@]}" \	649	"${cmd[@]}" \
636	1> >(tee -a "$log") \	650	1> >(tee -a "$log") \
637	2> >(tee -a "$log" >&2) \|\| \	651	2> >(tee -a "$log" \| "${filter[@]}" >&2) \|\| \
638	die "objtool klp diff failed"	652	die "objtool klp diff failed"
639	)	653	)
640	done	654	done
641	}	655	}
642		656
		657	# For each changed object, run objtool with --debug-checksum to get the
		658	# per-instruction checksums, and then diff those to find the first changed
		659	# instruction for each function.
		660	diff_checksums() {
		661	local orig_log="$ORIG_DIR/checksum.log"
		662	local patched_log="$PATCHED_DIR/checksum.log"
		663	local -A funcs
		664	local cmd=()
		665	local line
		666	local file
		667	local func
		668
		669	gawk '/\.o: changed function: / {
		670	sub(/:$/, "", $1)
		671	print $1, $NF
		672	}' "$KLP_DIFF_LOG" \| mapfile -t lines
		673
		674	for line in "${lines[@]}"; do
		675	read -r file func <<< "$line"
		676	if [[ ! -v funcs["$file"] ]]; then
		677	funcs["$file"]="$func"
		678	else
		679	funcs["$file"]+=" $func"
		680	fi
		681	done
		682
		683	cmd=("$SRC/tools/objtool/objtool")
		684	cmd+=("--checksum")
		685	cmd+=("--link")
		686	cmd+=("--dry-run")
		687
		688	for file in "${!funcs[@]}"; do
		689	local opt="--debug-checksum=${funcs[$file]// /,}"
		690
		691	(
		692	cd "$ORIG_DIR"
		693	"${cmd[@]}" "$opt" "$file" &> "$orig_log" \|\| \
		694	( cat "$orig_log" >&2; die "objtool --debug-checksum failed" )
		695
		696	cd "$PATCHED_DIR"
		697	"${cmd[@]}" "$opt" "$file" &> "$patched_log" \|\| \
		698	( cat "$patched_log" >&2; die "objtool --debug-checksum failed" )
		699	)
		700
		701	for func in ${funcs[$file]}; do
		702	diff <( grep0 -E "^DEBUG: .*checksum: $func " "$orig_log" \| sed "s\|$ORIG_DIR/\|\|") \
		703	<( grep0 -E "^DEBUG: .*checksum: $func " "$patched_log" \| sed "s\|$PATCHED_DIR/\|\|") \
		704	\| gawk '/^< DEBUG: / {
		705	gsub(/:/, "")
		706	printf "%s: %s: %s\n", $3, $5, $6
		707	exit
		708	}' \|\| true
		709	done
		710	done
		711	}
		712
643	# Build and post-process livepatch module in $KMOD_DIR	713	# Build and post-process livepatch module in $KMOD_DIR
644	build_patch_module() {	714	build_patch_module() {
645	local makefile="$KMOD_DIR/Kbuild"	715	local makefile="$KMOD_DIR/Kbuild"
@@ -743,6 +813,10 @@ fi · 97 unmodified lines
743	if (( SHORT_CIRCUIT <= 3 )); then	813	if (( SHORT_CIRCUIT <= 3 )); then
744	status "Diffing objects"	814	status "Diffing objects"
745	diff_objects	815	diff_objects
		816	if [[ -v DIFF_CHECKSUM ]]; then
		817	status "Finding first changed instructions"
		818	diff_checksums
		819	fi
746	fi	820	fi
747		821
748	if (( SHORT_CIRCUIT <= 4 )); then	822	if (( SHORT_CIRCUIT <= 4 )); then