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Date: Sat, 12 Sep 2009 11:25:07 +0100
From: Matt Fleming <matt@console-pimps.org>
To: =?iso-8859-1?B?VPZy9ms=?= Edwin <edwintorok@gmail.com>
Cc: rostedt@goodmis.org, Frederic Weisbecker <fweisbec@gmail.com>,
       linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
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       Mathieu Desnoyers <compudj@krystal.dyndns.org>,
       Paul Mundt <lethal@linux-sh.org>
Subject: Re: [PATCH 3/3] tracing: add latency format to function_graph
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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