On Thu, Aug 6, 2026 at 8:30 AM Andrey Grodzovsky <[email protected]> wrote: > > kernel.ftrace_enabled=0 is now refused on kernels that deprecate the > knob, so the old disable/reload flow no longer applies there. Probe > for this with ftrace_disable_supported() and keep the full original > scenario (disable, fail to load a livepatch, re-enable, load, confirm > disable is refused while loaded) on kernels where it still works; > otherwise just confirm the write is refused. > > Suggested-by: Steven Rostedt <[email protected]> > Suggested-by: Joe Lawrence <[email protected]> > Assisted-by: Claude:claude-sonnet-5 > Signed-off-by: Andrey Grodzovsky <[email protected]> > --- > .../testing/selftests/livepatch/functions.sh | 14 ++++++ > .../selftests/livepatch/test-ftrace.sh | 45 ++++++++++++------- > 2 files changed, 42 insertions(+), 17 deletions(-) > > diff --git a/tools/testing/selftests/livepatch/functions.sh > b/tools/testing/selftests/livepatch/functions.sh > index 30dc677b2f45..a65b7b1ac8ad 100644 > --- a/tools/testing/selftests/livepatch/functions.sh > +++ b/tools/testing/selftests/livepatch/functions.sh > @@ -126,6 +126,20 @@ function set_ftrace_enabled() { > echo "livepatch: kernel.ftrace_enabled = $result" > /dev/kmsg > } > > +# ftrace_disable_supported() - probe whether kernel.ftrace_enabled=0 > +# can still disable ftrace on this kernel. Newer kernels deprecate > +# the knob and always refuse the write with -EOPNOTSUPP. > +function ftrace_disable_supported() { > + local orig result > + > + orig=$(sysctl --values kernel.ftrace_enabled) > + sysctl -q kernel.ftrace_enabled=0 &> /dev/null > + result=$(sysctl --values kernel.ftrace_enabled) > + sysctl -q "kernel.ftrace_enabled=$orig" &> /dev/null > + > + [[ "$result" == "0" ]] > +}
Since the selftests are shipped with the kernel code, I think we don't need to handle backward compatibility here. Instead, we can just assume disabling ftrace is no longer supported. Thanks, Song [...]
