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

[Masami Hiramatsu]

Hi Steve,

Would you have any comment on this?

Thank you,

On Thu, 20 Jun 2019 00:07:09 +0900
Masami Hiramatsu <mhiramat@xxxxxxxxxx> 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@xxxxxxxxxx>


-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>