kernel debugging with gdb

kernel debugging with gdb

[Vasu S]

Hello all,

I am trying to use gdb for kernel debugging. I am getting the following error

# gdb vmlinux /proc/kcore

/proc/kcore: Operation not permitted.
(gdb)

I have compiled the kernel with debug options enabled.  I am on 2.6.5 kernel.
Can someone tell me what could be the problem here? Any help is appreciated.

Thanks,
Vasu

Re: kernel debugging with gdb

[Tigran Aivazian]

Hello Vasu,

First of all, access to /proc/kcore (and /dev/kmem) is explicitly disabled 
on some distributions (e.g. Red Hat) as they consider it a security issue.

Second, what you were trying to do wouldn't allow to debug the kernel 
anyway. At best (if the kernel was compiled with -g) you would get access 
to dump data variables like jiffies.

Third, to actually debug the kernel using gdb you need to go to kgdb 
homepage:

   http://kgdb.linsyssoft.com/

and download the bits and pieces you need. If you are running on x86_64 
architecture and wish to debug modules (as opposed to just statically 
linked kernel bits) then you will also need my fixes to the gdb patch 
which I can email you.

Kind regards
Tigran

On Fri, 27 May 2005, Vasu S wrote:

> Hello all,
>
> I am trying to use gdb for kernel debugging. I am getting the following error
>
> # gdb vmlinux /proc/kcore
>
> /proc/kcore: Operation not permitted.
> (gdb)
>
> I have compiled the kernel with debug options enabled.  I am on 2.6.5 kernel.
> Can someone tell me what could be the problem here? Any help is appreciated.
>
> Thanks,
> Vasu
>