linux-kernel - Re: gdb/scripts: Module symbol search paths

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Message-ID: <56E69438.3030407@siemens.com>
Date:	Mon, 14 Mar 2016 11:36:40 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Kieran Bingham <kieran.bingham@...aro.org>,
	Peter Griffin <peter.griffin@...aro.org>,
	Lee Jones <lee.jones@...aro.org>,
	Maxime Coquelin <maxime.coquelin@...com>,
	Russell Wayman <russell.wayman@...aro.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: gdb/scripts: Module symbol search paths

Hi Kieran,

On 2016-03-14 11:20, Kieran Bingham wrote:
> Hi Jan,
> 
> Whilst testing the modules update patch you sent, I discovered (due to
> having rebased to v4.5) that the module search path will end up picking
> an incorrect version of the .ko file if an earlier version exists.:
> 
> 
> (gdb) lx-symbols /opt/root/ubuntu-vivid.x86_64
> loading vmlinux
> (gdb) c
> Continuing.
> 	< load module helloworld.ko on target >
> scanning for modules in /opt/root/ubuntu-vivid.x86_64
> loading @0xffffffffa0000000:
> /opt/root/ubuntu-vivid.x86_64/lib/modules/4.4.0+/extra/helloworld.ko
> 
> Looking at the filesystem layout:
> 
> kbingham@...kieMonster:~$ sudo find /opt/root/ubuntu-vivid.x86_64/ -name
> helloworld.ko
> /opt/root/ubuntu-vivid.x86_64/lib/modules/4.4.0+/extra/helloworld.ko
> /opt/root/ubuntu-vivid.x86_64/lib/modules/4.5.0+/extra/helloworld.ko
> 

If there are multiple sets of modules underneath a path, you have to be
more precise, /opt/root/ubuntu-vivid.x86_64/lib/modules/4.5.0+ in this case.

> 
> Unfortunately I can't see any reference to a vfs path in:
>  print $lx_module("helloworld")
> 
> So we can't retrieve the exact path location from the kernel information
> Have you experienced this issue?

No, because I'm always using lx-symbols against the build output, not
against installed modules. But even then, see above, I don't see a
problem is the path is properly specified.

Jan

> 
> Perhaps we ought to prefix our search path with
> $(path_item)/lib/modules/`uname -r`
> 
> 
> ST's C implementation of module support can be seen at:
> 
> https://git.linaro.org/people/kieran.bingham/binutils-gdb.git/blob/e30a18cf086bd02c4ebb57f6f783fe2ad4af9c84:/gdb/stlinux/lkd-modules.c
> 
> They restrict the search paths, and parse expected
> lib/modules/{version}/ paths to ensure the correct modules are discovered.
> 
> --
> Regards
> 
> Kieran
> 


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