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Date: Sat, 9 May 2009 16:47:48 +0200
Message-ID: <c62985530905090747y14629237p2ad9ea5b10ce0126@mail.gmail.com>
Subject: Re: [RFC] convert ftrace syscall tracer to TRACE_EVENT()
From: =?ISO-8859-1?Q?Fr=E9d=E9ric_Weisbecker?= <fweisbec@gmail.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
       Jason Baron <jbaron@redhat.com>, Tom Zanussi <tzanussi@gmail.com>,
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       peterz@infradead.org, jiayingz@google.com, mbligh@google.com,
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Le 9 mai 2009 16:15, Ingo Molnar <mingo@elte.hu> a écrit :
>
> * Frédéric Weisbecker <fweisbec@gmail.com> wrote:
>
>> > I would expect to use copy_string_from_user (for strings) and
>> > copy_from_user for structures, because without any strings
>> > (especially), the trace information become much less useful.
>>
>> Yeah, for structures we would just need the copy_from_user.
>
> There's just a few places (mainly related to VFS APIs) where we
> really want to do that, and there we want to do it a bit later, not
> at syscall time: we want to do it after the getname(), to output a
> stable (and already copied to kernel space) copy of the file name.
>
> So the right solution there would be to add special, case by case
> tracepoints to those few places. We dont need strings for the
> majority of the 300+ system calls that exist on Linux.



Yeah, let's start with something generic. We'll be able to treat the particular
cases later, using types encoding and complex types description.


>
>        Ingo
>