On Thu, 12 Jan 2023 18:51:14 +0530
"Naveen N. Rao" <naveen.n.rao@xxxxxxxxxxxxxxxxxx> wrote:
> Akanksha J N wrote:
> > Commit 97f88a3d723162 ("powerpc/kprobes: Fix null pointer reference in
> > arch_prepare_kprobe()") fixed a recent kernel oops that was caused as
> > ftrace-based kprobe does not generate kprobe::ainsn::insn and it gets
> > set to NULL.
> > Extend multiple kprobes test to add kprobes on first 256 bytes within a
> > function, to be able to test potential issues with kprobes on
> > successive instructions.
What is the purpose of that test? If you intended to add a kprobe events
with some offset so that it becomes ftrace-based kprobe, it should be
a different test case, because
- This is a test case for checking multiple (at least 256) kprobe events
can be defined and enabled.
- If you want to check the ftrace-based kprobe, it should be near the
function entry, maybe within 16 bytes or so.
- Also, you don't need to enable it at once (and should not for this case).
> > The '|| true' is added with the echo statement to ignore errors that are
> > caused by trying to add kprobes to non probeable lines and continue with
> > the test.
Can you add another test case for that? (and send it to the MLs which Cc'd
to this mail)
e.g.
for i in `seq 0 16`; do
echo p:testprobe $FUNCTION_FORK+${i} >> kprobe_events || continue
echo 1 > events/kprobes/testprobe/enable
( echo "forked" )
echo 0 > events/kprobes/testprobe/enable
echo > kprobe_events
done
BTW, after we introduce the fprobe event (https://lore.kernel.org/linux-trace-kernel/166792255429.919356.14116090269057513181.stgit@devnote3/) that test case may be
update to check fprobe events.
Thank you,
> >
> > Signed-off-by: Akanksha J N <akanksha@xxxxxxxxxxxxx>
> > ---
> > .../selftests/ftrace/test.d/kprobe/multiple_kprobes.tc | 4 ++++
> > 1 file changed, 4 insertions(+)
>
> Thanks for adding this test!
>
> >
> > diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/multiple_kprobes.tc b/tools/testing/selftests/ftrace/test.d/kprobe/multiple_kprobes.tc
> > index be754f5bcf79..f005c2542baa 100644
> > --- a/tools/testing/selftests/ftrace/test.d/kprobe/multiple_kprobes.tc
> > +++ b/tools/testing/selftests/ftrace/test.d/kprobe/multiple_kprobes.tc
> > @@ -25,6 +25,10 @@ if [ $L -ne 256 ]; then
> > exit_fail
> > fi
> >
> > +for i in `seq 0 255`; do
> > + echo p $FUNCTION_FORK+${i} >> kprobe_events || true
> > +done
> > +
> > cat kprobe_events >> $testlog
> >
> > echo 1 > events/kprobes/enable
>
> Thinking about this more, I wonder if we should add an explicit fork
> after enabling the events, similar to kprobe_args.tc:
> ( echo "forked" )
>
> That will ensure we hit all the probes we added. With that change:
> Acked-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
>
>
> - Naveen
--
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
