linux-kernel - Re: [PATCH 3/3] tracing: add latency format to function

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Message-ID: <20090912102506.GC21695@console-pimps.org>
Date:	Sat, 12 Sep 2009 11:25:07 +0100
From:	Matt Fleming <matt@...sole-pimps.org>
To:	Török Edwin <edwintorok@...il.com>
Cc:	rostedt@...dmis.org, Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Li Zefan <lizf@...fujitsu.com>,
	Mathieu Desnoyers <compudj@...stal.dyndns.org>,
	Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [PATCH 3/3] tracing: add latency format to function_graph
 tracer

On Fri, Sep 11, 2009 at 07:08:00PM +0300, Török Edwin wrote:
> 
> BTW any plans on integrating an in-kernel unwinder like systemtap has?
> 
> Even if I build libc with framepointers, a userspace stacktrace on
> x86-64 can't go beyond most pthreads routines, like __read_nocancel
> (they're written in asm maybe?).
> 

fyi SH has an in-kernel DWARF unwinder. It was my intention to shake out
most of the bugs (of which there have been a few) by having it in the SH
tree and then submit it for generic inclusion.

So by carefully placing .cfi_* directives in assembly, you can get
stacktraces for assembly routines in the kernel.

The branch containing the latest code is here,
http://git.kernel.org/?p=linux/kernel/git/lethal/sh-2.6.git;a=shortlog;h=sh/dwarf-unwinder
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