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From: Steven Rostedt <>
To: Frederic Weisbecker <>
Cc: Ingo Molnar <>,
Subject: Re: [RFC][PATCH] Make ftrace able to trace function return
Date: Thu, 30 Oct 2008 16:30:12 -0400 (EDT)	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Thu, 30 Oct 2008, Frederic Weisbecker wrote:
> So the idea is to allocate a general set of slots on which we can save our original
> return address and the call time. After that we change the return address of the
> hooked function to jump on a trampoline which will push the offset for us
> to retrieve the slot on the set for this function call. Then the trampoline
> will call a return handler that will trace the return time and send all of these
> informations to a specific tracer. And then the return handler will return to the
> original return address.
> To determine quickly which slot is free, I use a bitmap of 32 bits. 
> Perhaps it is a bad assumption but I could enlarge it and there is an overrun
> counter. This is the only point which needs to be protected against 
> concurrent access.

What about storing the return addresses on the bottom of the stack?
That is, start at task->stack + sizeof(thread_info), and stack up on that. 
Be careful, there might already be users of that area. This will also need 
to be arch dependent.

Note, more is needed than what I wrote above, I'm just suggesting another 

-- Steve

  parent reply	other threads:[~2008-10-30 20:30 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-30 19:20 Frederic Weisbecker
2008-10-30 18:20 ` Ingo Molnar
2008-10-30 18:30   ` Frédéric Weisbecker
2008-10-30 18:37     ` Ingo Molnar
2008-10-30 19:17       ` Steven Rostedt
2008-10-30 19:26         ` Ingo Molnar
2008-11-03 11:16           ` Ananth N Mavinakayanahalli
2008-11-03 13:32             ` Frédéric Weisbecker
2008-10-31  1:35       ` Frédéric Weisbecker
2008-10-30 20:30 ` Steven Rostedt [this message]
2008-10-31  0:05   ` Frédéric Weisbecker
2008-10-31  2:43     ` Steven Rostedt
2008-10-31 20:18       ` Frederic Weisbecker
2008-11-03 10:06         ` Ingo Molnar
2008-11-03 13:11           ` Frédéric Weisbecker

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