Re: [PATCH v3 12/13] livepatch/klp-build: report patch validation drift

[Joe Lawrence <joe.lawrence@redhat.com>]

On Mon, Feb 23, 2026 at 01:40:14PM -0800, Josh Poimboeuf wrote:
> On Tue, Feb 17, 2026 at 11:06:43AM -0500, Joe Lawrence wrote:
> > Capture the output of the patch command to detect when a patch applies
> > with fuzz or line offsets.
> > 
> > If such "drift" is detected during the validation phase, warn the user
> > and display the details.  This helps identify input patches that may need
> > refreshing against the target source tree.
> > 
> > Ensure that internal patch operations (such as those in refresh_patch or
> > during the final build phase) can still run quietly.
> > 
> > Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
> > ---
> >  scripts/livepatch/klp-build | 24 +++++++++++++++++++-----
> >  1 file changed, 19 insertions(+), 5 deletions(-)
> > 
> > diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
> > index fd104ace29e6..5367d573b94b 100755
> > --- a/scripts/livepatch/klp-build
> > +++ b/scripts/livepatch/klp-build
> > @@ -369,11 +369,24 @@ check_unsupported_patches() {
> >  
> >  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"
> > -	patch -d "$SRC" -p1 --dry-run --silent --no-backup-if-mismatch -r /dev/null < "$patch"
> > -	patch -d "$SRC" -p1 --silent --no-backup-if-mismatch -r /dev/null < "$patch"
> > +	status=0
> > +	output=$(patch -d "$SRC" -p1 --dry-run --no-backup-if-mismatch -r /dev/null "${extra_args[@]}" < "$patch" 2>&1) || status=$?
> > +	if [[ "$status" -ne 0 ]]; then
> > +		echo "$output"
> > +		die "$patch did not apply"
> > +	elif [[ "$output" =~ $drift_regex ]]; then
> > +		warn "$patch applied with drift"
> > +		echo "$output"
> 
> Just for consistency with the output ordering of the "patch did not
> apply" error, I think the "$output" should be printed *before* the
> "$patch applied with drift".
> 
> Also, should $output be printed to stderr?
> 

Will adjust both ^^ for v4.

> Also, I've not heard of patch "drift", is "fuzz" better?
> 

Ah, I was trying to figure what word would include both offset and fuzz.
I /think/ "fuzz" may be used for both, so I can just use that for v4.

--
Joe