On Thu, 12 Jan 2023 18:51:14 +0530 "Naveen N. Rao" naveen.n.rao@linux.vnet.ibm.com 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/166792255429.919356.1411609026905...) that test case may be update to check fprobe events.
Thank you,
Signed-off-by: Akanksha J N akanksha@linux.ibm.com
.../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@linux.vnet.ibm.com
- Naveen