linux-kernel - Re: [PATCH -v4 9/9] tracing: add function graph tracer support for MIPS

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Message-Id: <1256227916.20866.784.camel@gandalf.stny.rr.com>
Date:	Thu, 22 Oct 2009 12:11:56 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	David Daney <ddaney@...iumnetworks.com>
Cc:	wuzhangjin@...il.com, linux-kernel@...r.kernel.org,
	linux-mips@...ux-mips.org, Thomas Gleixner <tglx@...utronix.de>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Nicholas Mc Guire <der.herr@...r.at>
Subject: Re: [PATCH -v4 9/9] tracing: add function graph tracer support for
 MIPS

On Thu, 2009-10-22 at 08:59 -0700, David Daney wrote:

> This is what I was talking about up-thread.  Leaf functions may have no 
> function prolog.  If you do code scanning you will fail.  While scanning 
> backwards, there is no way to know when you have entered a new function. 
>   Looking for function return sequences 'jr ra' doesn't work as there 
> may be functions with multiple return sites, functions that never 
> return, or arbitrary data before the function.  I think you have to 
> force a frame pointer to be established if you want this to work.

Functions that run off into another function?? I guess the compiler
could do that, but with -pg enable, I would think is broken.

-- Steve


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