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

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Message-ID: <56E69067.1020909@linaro.org>
Date:	Mon, 14 Mar 2016 10:20:23 +0000
From:	Kieran Bingham <kieran.bingham@...aro.org>
To:	Jan Kiszka <jan.kiszka@...mens.com>,
	Peter Griffin <peter.griffin@...aro.org>,
	Lee Jones <lee.jones@...aro.org>,
	Lee Jones <lee.jones@...aro.org>,
	Peter Griffin <peter.griffin@...aro.org>,
	Maxime Coquelin <maxime.coquelin@...com>,
	Russell Wayman <russell.wayman@...aro.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: gdb/scripts: Module symbol search paths

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


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?

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