Re: [PATCH v2 00/12] tracing/probe: Add multi-probes per event support

Steven Rostedt
2019-07-04T11:28:39Z

On Thu, 4 Jul 2019 15:39:58 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Hi Steve,
>
> Would you have any comment on this?
>

Hi Masami,

It's on my todo list. As today is a US holiday, I'll look at this on
Monday.

Thanks for the reminder!

-- Steve

> Thank you,
>
> On Thu, 20 Jun 2019 00:07:09 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > Hello,
> >
> > This is the 2nd version of multi-probes per event support on ftrace
> > and perf-tools.
> >
> > Previous version is here;
> > https://lkml.org/lkml/2019/5/31/573
> >
> > >From this version, I omitted first 9 patches which has been picked
> > to Steve's tree.
> > In this version, I've fixed some bugs and hardened some unexpected
> > error cases according to Steve's comment.
> > Here are changes in this version:
> >
> > - [1/12] This have below changes.
> > - Warn if the primary trace_probe does not exist.
> > - Fix enable_trace_kprobe() to not return error if the any probes
> > are "gone" state. If all probes have gone or any other error
> > reason, the event can not be enabled and return error.
> > - Fix trace_probe_enable() to roll back all enabled uprobe if
> > any one of uprobe is failed to enable.
> > - [7/12] Swap the checking order of filename for avoiding unexpected
> > memory access.
> >
> >
> > ====
> > For trace-event, we can insert same trace-event on several places
> > on the code, and those can record similar information as a same event
> > with same format.
> >
> > This series implements similar feature on probe-event. Since the probe
> > event is based on the compiled binary, sometimes we find that the target
> > source line is complied into several different addresses, e.g. inlined
> > function, unrolled loop, etc. In those cases, it is useful to put a
> > same probe-event on different addresses.
> >
> > With this series, we can append multi probes on one event as below
> >
> > # echo p:testevent _do_fork r1=%ax r2=%dx > kprobe_events
> > # echo p:testevent fork_idle r1=%ax r2=%cx >> kprobe_events
> > # kprobe_events
> > p:kprobes/testevent _do_fork r1=%ax r2=%dx
> > p:kprobes/testevent fork_idle r1=%ax r2=%cx
> >
> > This means testevent is hit on both of _do_fork and fork_idle.
> > As you can see, the appended event must have same number of arguments
> > and those must have same 'type' and 'name' as original one. This is like
> > a function signature, it checks whether the appending event has the same
> > type and name of event arguments and same probe type, but doesn't care
> > about the assignment.
> >
> > So, below appending commands will be rejected.
> >
> > # echo p:testevent _do_fork r1=%ax r2=%dx > kprobe_events
> > # echo p:testevent fork_idle r1=%ax >> kprobe_events
> > (No 2nd argument)
> > # echo p:testevent fork_idle r1=%ax r2=%ax:x8 >> kprobe_events
> > (The type of 2nd argument is different)
> >
> > If one inlined code has an argument on a register, but another
> > inlined code has fixed value (as a result of optimization),
> > you can also specify the fixed immediate value, e.g.
> >
> > # echo p:testevent _do_fork r1=%ax r2=%dx > kprobe_events
> > # echo p:testevent fork_idle r1=%ax r2=\1 >> kprobe_events
> >
> >
> > Thank you,
> >
> > ---
> >
> > Masami Hiramatsu (12):
> > tracing/probe: Split trace_event related data from trace_probe
> > tracing/dynevent: Delete all matched events
> > tracing/dynevent: Pass extra arguments to match operation
> > tracing/kprobe: Add multi-probe per event support
> > tracing/uprobe: Add multi-probe per uprobe event support
> > tracing/kprobe: Add per-probe delete from event
> > tracing/uprobe: Add per-probe delete from event
> > tracing/probe: Add immediate parameter support
> > tracing/probe: Add immediate string parameter support
> > selftests/ftrace: Add a testcase for kprobe multiprobe event
> > selftests/ftrace: Add syntax error test for immediates
> > selftests/ftrace: Add syntax error test for multiprobe
> >
> >
> > Documentation/trace/kprobetrace.rst | 1
> > Documentation/trace/uprobetracer.rst | 1
> > kernel/trace/trace.c | 8 -
> > kernel/trace/trace_dynevent.c | 10 +
> > kernel/trace/trace_dynevent.h | 7 -
> > kernel/trace/trace_events_hist.c | 4
> > kernel/trace/trace_kprobe.c | 241 ++++++++++++++----
> > kernel/trace/trace_probe.c | 176 +++++++++++--
> > kernel/trace/trace_probe.h | 67 ++++-
> > kernel/trace/trace_uprobe.c | 263 +++++++++++++++-----
> > tools/testing/selftests/ftrace/test.d/functions | 2
> > .../ftrace/test.d/kprobe/kprobe_multiprobe.tc | 35 +++
> > .../ftrace/test.d/kprobe/kprobe_syntax_errors.tc | 15 +
> > 13 files changed, 665 insertions(+), 165 deletions(-)
> > create mode 100644 tools/testing/selftests/ftrace/test.d/kprobe/kprobe_multiprobe.tc
> >
> > --
> > Masami Hiramatsu (Linaro) <mhiramat@kernel.org>
>
>