On Thu, 20 Jun 2019 00:07:09 +0900 Masami Hiramatsu <mhira...@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 > > Hi Masami, I applied this patch set to my queue. Nice feature! I'll probably be testing it a bit more. I wont be pushing it to my repo until v5.3-rc3 comes out, as I'll plan on rebasing my for-next branch on that. Thanks! -- Steve
