Messages in this thread | | | Date | Sat, 9 May 2009 15:33:06 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC] convert ftrace syscall tracer to TRACE_EVENT() |
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* Frédéric Weisbecker <fweisbec@gmail.com> wrote:
> > Secondly, we should reuse the information we get in > > SYSCALL_DEFINE, to construct the TRACE_EVENT tracepoints > > directly - without having to list all syscalls again in a > > separate file. > > Indeed, that's not trivial though, but feasible. I'm not sure we > can reuse the TRACE_EVENT macro directly inside SYSCALL_DEFINE. > The resulting macro tempest effect that would occur confuses me > and I have troubles to imagine the result.
Lets take an example. This syscall:
SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param)
Is equivalent to:
SYSCALL_DEFINE3(name, t1, v1, t2, v2, t3, v3)
('t' for type, 'v' for variable/value).
This would transform into the following TRACE_EVENT() construct:
TRACE_EVENT_SYSCALL2():
TRACE_EVENT(sys_##name, TP_PROTO(t1 v1, t2 v2), TP_ARGS(v1, v2), TP_STRUCT__entry( __field(t1, v1) __field(t2, v2) ), TP_fast_assign( __entry->v1 = v1; __entry->v2 = v2; ), TP_printk("%016Lx %016Lx", (u64)__entry->v1, (u64)__entry->v2) );
We need TRACE_EVENT_SYSCALL[123456] definitions, and that's it.
The only place where we lose type information is the printk format - but that's not a big issue, as i'd expect the event record to be the main user of this.
[ In addition to this, we could extend DEFINE_SYSCALL[1..6] with a (optional) format string definition field, and fill that in for anything that matters. ]
Note, this assumes that all syscall types can be described via __field() - i think that's correct. (we dont want to deref strings as they are untrusted, and there are no arrays in syscall parameters)
Can you see any complication?
Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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