Re: [PATCH v3 09/13] livepatch/klp-build: fix version mismatch when short-circuiting

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

On Mon, Feb 23, 2026 at 01:13:29PM -0800, Josh Poimboeuf wrote:
> On Tue, Feb 17, 2026 at 11:17:00AM -0500, Joe Lawrence wrote:
> > Maybe I'm starting to see things, but when running 'S 2' builds, I keep
> > getting "vmlinux.o: changed function: override_release".  It could be
> > considered benign for quick development work, or confusing.  Seems easy
> > enough to stash and avoid.
> > 
> > Repro:
> > 
> > Start with a clean source tree, setup some basic configs for klp-build:
> > 
> >   $ make clean && make mrproper
> >   $ vng --kconfig
> >   $ ./scripts/config --file .config \
> >        --set-val CONFIG_FTRACE y \
> >        --set-val CONFIG_KALLSYMS_ALL y \
> >        --set-val CONFIG_FUNCTION_TRACER y \
> >        --set-val CONFIG_DYNAMIC_FTRACE y \
> >        --set-val CONFIG_DYNAMIC_DEBUG y \
> >        --set-val CONFIG_LIVEPATCH y
> >   $ make olddefconfig
> > 
> > Build the first patch, save klp-tmp/ (note the added DEBUG that dumps
> > the localversion after assignment in set_kernelversion):
> > 
> >   $ ./scripts/livepatch/klp-build -T ~/cmdline-string.patch 
> >   DEBUG: localversion=6.19.0-gc998cd490c02                           <<
> >   Validating patch(es)
> >   Building original kernel
> >   Copying original object files
> >   Fixing patch(es)
> >   Building patched kernel
> >   Copying patched object files
> >   Diffing objects
> >   vmlinux.o: changed function: cmdline_proc_show
> >   BMuilding patch module: livepatch-cmdline-string.ko
> >   SgUCCESS
> >    c
> > Buield a second patch, short-circuit to step 2 (build patched kernel):
> > 
> >   $ ./scripts/livepatch/klp-build -T -S 2 ~/cmdline-string.patch
> >   DEBUG: localversion=6.19.0+                                        <<
> >   Fixing patch(es)
> >   Building patched kernel
> >   Copying patched object files
> >   Diffing objects
> >   vmlinux.o: changed function: override_release                      <<
> >   vmlinux.o: changed function: cmdline_proc_show
> >   Building patch module: livepatch-cmdline-string.ko
> >   SUCCESS
> 
> Hm, I wasn't able to recreate, but it's worrisome that two different
> localversions are being reported.  How do we know which one is correct?
> 
> I'm also not sure why my original code is being so obtuse by
> constructing the kernelrelease manually.  I can't remember if that's on
> purpose or not.
> 
> The below would be simpler, I wonder if this also happens to fix the
> issue?
> 

I finally figured out why you couldn't reproduce, in my tests, I never
built the original kernel, I jumped straight from a clean repo to
starting up klp-build.  If I perform an initial make before running
klp-build, then the sequence works as expected. 

- If skipping the initial vmlinux is an unsupported use-case, then we
  can ignore and drop this patch,
- or perhaps detect and warn/error out 
- If this is something we need to support, then your suggested version
  below didn't work out either...

The following change committed on top of v7.0-rc2:

diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
index 809e198a561d..f223395e630e 100755
--- a/scripts/livepatch/klp-build
+++ b/scripts/livepatch/klp-build
@@ -285,15 +285,16 @@ set_module_name() {
 # application from appending it with '+' due to a dirty git working tree.
 set_kernelversion() {
        local file="$SRC/scripts/setlocalversion"
-       local localversion
+       local kernelrelease
 
        stash_file "$file"
 
-       localversion="$(cd "$SRC" && make --no-print-directory kernelversion)"
-       localversion="$(cd "$SRC" && KERNELVERSION="$localversion" ./scripts/setlocalversion)"
-       [[ -z "$localversion" ]] && die "setlocalversion failed"
+       kernelrelease="$(cd "$SRC" && make kernelrelease)"
+       [[ -z "$kernelrelease" ]] && die "setlocalversion failed"
 
-       sed -i "2i echo $localversion; exit 0" scripts/setlocalversion
+       echo "DEBUG: kernelrelease=$kernelrelease"
+
+       sed -i "2i echo $kernelrelease; exit 0" scripts/setlocalversion
 }
 
 get_patch_files() {


$ git clone --branch v7.0-rc2 --depth=1 git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

[ add the commit above ]

$ git status
On branch master
Your branch is ahead of 'origin/master' by 1 commit.
  (use "git push" to publish your local commits)

nothing to commit, working tree clean

$ vng --kconfig
$ ./scripts/config --file .config \
   --set-val CONFIG_FTRACE y \
   --set-val CONFIG_KALLSYMS_ALL y \
   --set-val CONFIG_FUNCTION_TRACER y \
   --set-val CONFIG_DYNAMIC_FTRACE y \
   --set-val CONFIG_DYNAMIC_DEBUG y \
   --set-val CONFIG_LIVEPATCH y
$ make olddefconfig

$ ./scripts/livepatch/klp-build -T ~/src/linux/cmdline-string.patch 
DEBUG: kernelrelease=7.0.0-rc2-00001-g624702e6338b
Validating patch(es)
Building original kernel
Copying original object files
Fixing patch(es)
Building patched kernel
Copying patched object files
Diffing objects
vmlinux.o: changed function: cmdline_proc_show
Building patch module: livepatch-cmdline-string.ko
SUCCESS

$ strings livepatch-cmdline-string.ko | grep vermagic
vermagic=7.0.0-rc2-00001-g624702e6338b SMP preempt mod_unload

$ ./scripts/livepatch/klp-build -T -S 2 ~/src/linux/cmdline-string.patch 
DEBUG: kernelrelease=7.0.0-rc2+
Fixing patch(es)
Building patched kernel
Copying patched object files
Diffing objects
vmlinux.o: changed function: override_release
vmlinux.o: changed function: cmdline_proc_show
Building patch module: livepatch-cmdline-string.ko
SUCCESS

$ strings livepatch-cmdline-string.ko | grep vermagic
vermagic=7.0.0-rc2+ SMP preempt mod_unload 

--
Joe