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Message-ID: <20090308112840.GC5000@nowhere>
Date: Sun, 8 Mar 2009 12:28:41 +0100
From: Frederic Weisbecker <fweisbec@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
Lai Jiangshan <laijs@...fujitsu.com>,
Steven Rostedt <rostedt@...dmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
Jiaying Zhang <jiayingz@...gle.com>,
Martin Bligh <mbligh@...gle.com>,
Arjan van de Ven <arjan@...radead.org>
Subject: Re: [RFC][PATCH 0/2] Syscalls tracing
On Sun, Mar 08, 2009 at 12:24:41PM +0100, Frederic Weisbecker wrote:
> On Sat, Mar 07, 2009 at 05:02:47PM +0100, Frederic Weisbecker wrote:
> > On Sat, Mar 07, 2009 at 01:15:18PM +0100, Peter Zijlstra wrote:
> > > On Sat, 2009-03-07 at 05:52 +0100, Frederic Weisbecker wrote:
> > > > Here is a first attempt, quick one-shot, to provide a syscall tracing
> > > > infrastructure on ftrace.
> > > >
> > > > The RFC prefix is here to reflect its ugliness on various parts.
> > > > The compromise between tracing reliabilty and speed is hard to balance.
> > > > For example I guess the basic and horrid string mask should be dropped in favour
> > > > of something else, which takes care of the volatile strings from the userspace.
> > > >
> > > > But I hope a lot of ideas to make it better will come along this discussion.
> > >
> > > Can't you abuse the SYSCALL_DEFINE macros? This current approach looks
> > > like it will replicate the syscall table.
> > >
> >
> >
> > Ah, I did not even think about it.
> > I will be able to get the number of parameters. Sounds good. But I will
> > still need a way to store their format somewhere.
> >
>
> Ok, we can iterate through sections datas for each one and then generate the format string
> depending of the types of the parameters. We can even to it once at boot time.
> The last thing is the need to match the exact syscall entry from this section when we enter
> a syscall. Don't know yet how I will do that but I will think about it.
>
Ah and the string mask is actually useful to determine if we one parameter is a string.
If so we can decide to save it on tracing time or not.
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