Messages in this thread | | | Date | Mon, 5 May 2008 07:30:57 -0400 | From | Mathieu Desnoyers <> | Subject | Re: System call instrumentation |
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* Ingo Molnar (mingo@elte.hu) wrote: > > * Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote: > > > > hm, i'm not sure about this. I've implemented system call tracing in > > > -rt [embedded in the latency tracer] and it only needed changes in > > > entry.S, not in every system call site. Now, granted, that tracer > > > was simpler than what LTTng tries to do, but do we _really_ need > > > more complexity? A trace point that simply expresses: > > > > > > sys_call_event(int sysno, long param1, long param2, long param3, > > > long param4, long param5, long param6); > > > > > > > That would work for all system calls that doesn't have parameters like > > "const char __user *filename". > > what's the problem with them? Do you want to follow those parameters? > > Ingo
Ideally, I'd like to have this kind of high-level information :
event name : kernel syscall syscall name : open arg1 (%s) : "somefile" <----- arg2 (%d) : flags arg3 (%d) : mode
However, "somefile" has to be read from userspace. With the protection involved, it would cause a performance impact to read it a second time rather than tracing the string once it's been copied to kernel-space.
Mathieu
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