Messages in this thread | | | Date | Sat, 23 Sep 2006 11:50:06 -0400 | From | Mathieu Desnoyers <> | Subject | Re: LTTng and SystemTAP (Everyone who is scared to read this huge thread, skip to here) |
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* Ingo Molnar (mingo@elte.hu) wrote: > > * Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote: > > > > Some of the extensive hooking you do in LTT could be aleviated to a > > > great degree if you used dynamic probes. For example the syscall > > > entry hackery in LTT looks truly scary. > > > > Yes, agreed. The last time I checked, I thought about moving this > > tracing code to the syscall_trace_entry/exit (used for security hooks > > and ptrace if I remember well). I just didn't have the time to do it > > yet. > > correct, that's where all such things (auditing, seccomp, ptrace, > sigstop, freezing, etc.) hook into. Much (all?) of the current entry.S > hacks can go away in favor of a much easier .c patch to > do_syscall_trace() and this would reduce a significantion portion of the > present intrusiveness of LTTng. >
Hi Ingo,
The only problem with do_syscall_trace is that it is only called at the beginning of the system call. LTT also needs a marker at the end of the system call to know when the control went back to user space.
Any idea of a nice location (in C code preferably) for such a marker ?
Mathieu
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