14:27 <tester_perf> Hello im trying to hook sys_perf_event_open calls using systemtap. I got this error http://pastebin.com/9uwLGCUH. I tried looking inside the stp files inside tapset and could not find anything related to the syscall -- is that why I'm unable to hook that?

14:27 <tester_perf> I tried looking into the tapset of 3.0 as well but thta does not seem to have it eithre

14:27 <tester_perf> (sorry about the typos).

14:27 <tester_perf> Is it possible to hook sys_perf_event_open using systemtap?

14:28 <fche> hm, I'm having no problem here

14:28 <fche> stap -L syscall.perf_event_open

14:28 <fche> syscall.perf_event_open name:string attr_uaddr:long pid:long cpu:long group_fd:long flags:long flags_str:string argstr:string $attr_uptr:long int $pid:long int $cpu:long int $group_fd:long int $flags:long int $ret:long int

14:29 <fche> try also % stap -L 'kernel.function("*perf_event_open")'

14:29 <tester_perf> ok

14:31 <tester_perf> in both cases nothing is printed out

14:32 <fche> ok try stap -L nd_syscall.perf_event_open

14:32 <fche> nd_ == non-dwarf, i.e., without requiring kernel debuginfo

14:32 <fche> (see [man stapprobes])

14:34 <tester_perf> let me check that thx. using nd_ did not help though. i rechecked with sys_open to confirm and that does work.

14:35 <fche> weird. maybe your kernel lacks that piece? try grep perf_event_open /proc/kallsyms

14:37 <tester_perf> c0036184 W sys_perf_event_open

14:43 <tester_perf> so the stap errors.html says "SystemTap did not understand what the event or SystemTap function foo refers to. This usually means that SystemTap could not find a match for foo in the tapset library. N refers to the line and column of the error."

14:43 <tester_perf> do you have anything in tapset/ related to sys_perf_event_open?

14:43 <tester_perf> I seem to have a few entries related to sys_pipe, sys_open etc but I don't see anything related to perf -- could that be the reason?

14:44 <fche> the [nd_]syscall.perf_event_open refer to that

14:44 <fche> hm, i386

14:46 <fche> so stap >= version 2.8 contains syscall.perf_event_open in the tapset

14:47 <fche> it maps to kernel.function("sys_perf_event_open")

14:47 <tester_perf> I see

14:47 <fche> what kernel/distro etc. are you using?

14:49 <fche> might as well stap-report and paste the output someplace

14:57 <tester_perf> :q

14:57 <tester_perf> (oops sorry)

14:57 <tester_perf> im trying it on arm cross compiled kernel

14:58 <fche> ahhh.