linux-kernel - Re: BISECTED: Re: source line numbers with x86

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Date:	Tue, 27 Jan 2009 17:20:45 -0500 (EST)
From:	Dave Anderson <anderson@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Andi Kleen <andi@...stfloor.org>, Bernhard Walle <bwalle@...e.de>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	crash-utility@...hat.com, Mike Snitzer <snitzer@...il.com>
Subject: Re: BISECTED: Re: source line numbers with x86_64 modules?


----- "Eric W. Biederman" <ebiederm@...ssion.com> wrote:

> Dave Anderson <anderson@...hat.com> writes:
> 
> > Actually it's not a problem with the vmlinux file, but rather with kernel
> > module object files.  The crash utility has an embedded gdb module which
> > is invoked as "gdb vmlinux", and to get line numbers, the crash utility
> > simply uses the relevant built-in gdb function to get them.  And line
> > numbers work fine with the base kernel code from the vmlinux file.
> >
> > The debuginfo data of kernel modules can be subsequently added to the
> > crash session by doing a gdb "add-symbol-file" command for any or all
> > kernel modules.  But getting correct line number information for kernel
> > modules has been a crap-shoot in the past, depending upon architecture
> > and/or kernel version.  For example, they don't work with 2.6.9-based
> > RHEL4 x86_64 kernel modules, but work fine with 2.6.18-based RHEL5 x86_64
> > kernels.
> >
> > Looking at Mike's suspect kernel patch list, I don't see anything that
> > would have any relationship to the issue.  Perhaps there was a build tool
> > change during the same timeframe? 
> 
> It look like Mike just built a series of kernels and had a problem,
> which should preclude a tool change.
> 
> That said.  Does this feature of crash work in 2.6.29?  If not is
> there enough interest to track this down, and fix it if it is a
> kernel bug?
> 
> If we are going to be using these tools we need them working on the
> latest and greatest kernels, not some weird enterprise branch, for
> fuddy duddies.

Personally I don't know -- I am a fuddy duddy.  

I have tinkered with at least 2.6.28-era vmlinux/vmcore pairs, but never
with any kernel modules thereof.

Dave

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