Masami Hiramatsu wrote:
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 follow up to:
http://lore.kernel.org/1664530538.ke6dp49pwh.naveen@xxxxxxxxxxxxx
The intent is to add consecutive probes covering KPROBES_ON_FTRACE,
vanilla trap-based kprobes as well as optprobes to ensure all of those
and their interactions are good.
- 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
The current test to add multiple kprobes within a function also falls
under the purview of multiple_kprobes.tc, but it can be split into a
separate multiple_kprobes_func.tc if you think that will be better.
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.
Indeed, I suppose that can be a separate test.
Thanks,
Naveen
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>
