Linux kernel crash dumps for ARM

Linux kernel crash dumps for ARM

[Venkappa Mala]

Hi,

With respect to "Linux kernel crash dumps for ARM", i have some doubts which are described as below.

If the machine has crashed so badly that you cannot enter commands or
the disk is not available then you have three options :-

(1) Hand copy the text from the screen

(2) capture crash logs using Minicom.

(3) save the crash data to a floppy disk or video rom or a swap partition or reserved memory.

In the above three options, 1 & 2 are known and works as well.

Regarding 3 option,
----------------------------
i would like to support for ARM11.

As far as i know, the supported linux kernel crash dumps are
"lkcd, netdump,diskdump, mini kernel dump and kdump/kexec".
These are supported for x86 and PowerPC architectures with some constrains.

i have some queries with respect to ARM supports, these are

1.) kexec is supported in latest kernels
        example: 2.6.29 kernel
        File: arch/arm/kernel/machine_kexec.c

    - is this working well or is there any constraints?

2) As per kexec supports, kexec-tool is required and this allows you to load directly
   to a new kernel from the currently running one

    As from my side, i am not able to find arm implementation support in kexec-tools/crash sources.

   - is kexce-tool supported for ARM or not?

3) In lkcd, netdump,diskdump, mini kernel dump and kdump/kexec tools,

   - which is the best choice for ARM or are there any best crash dump tool for ARM?

Please clarify my queries.

Best Regards,
Venkappa


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______________________________________________________________________

Re: Linux kernel crash dumps for ARM

[Eric W. Biederman]

Venkappa Mala <Venkappa.Mala@lntinfotech.com> writes:

I have added the kexec list and corrected the lkml addresses.
In principle it should not be too hard to use kexec on panic
support on arm.

I don't do any arm development so I don't have a clue what the status
of the support is on arm.

> Hi,
>
> With respect to "Linux kernel crash dumps for ARM", i have some doubts which are described as below.
>
> If the machine has crashed so badly that you cannot enter commands or
> the disk is not available then you have three options :-
>
> (1) Hand copy the text from the screen
>
> (2) capture crash logs using Minicom.
>
> (3) save the crash data to a floppy disk or video rom or a swap partition or reserved memory.
>
> In the above three options, 1 & 2 are known and works as well.
>
> Regarding 3 option,
> ----------------------------
> i would like to support for ARM11.
>
> As far as i know, the supported linux kernel crash dumps are
> "lkcd, netdump,diskdump, mini kernel dump and kdump/kexec".
> These are supported for x86 and PowerPC architectures with some constrains.
>
> i have some queries with respect to ARM supports, these are
>
> 1.) kexec is supported in latest kernels
>         example: 2.6.29 kernel
>         File: arch/arm/kernel/machine_kexec.c
>
>     - is this working well or is there any constraints?
>
> 2) As per kexec supports, kexec-tool is required and this allows you to load directly
>    to a new kernel from the currently running one
>
>     As from my side, i am not able to find arm implementation support in kexec-tools/crash sources.
>
>    - is kexce-tool supported for ARM or not?
>
> 3) In lkcd, netdump,diskdump, mini kernel dump and kdump/kexec tools,
>
>    - which is the best choice for ARM or are there any best crash dump tool for ARM?
>
> Please clarify my queries.
>
> Best Regards,
> Venkappa

Eric

Re: Linux kernel crash dumps for ARM

[Bernhard Walle]

Am 05.01.2010 06:20, schrieb Eric W. Biederman:
>>
>> 3) In lkcd, netdump,diskdump, mini kernel dump and kdump/kexec tools,
>>
>>    - which is the best choice for ARM or are there any best crash
dump tool for ARM?

LKCD is more or less dead (in favour of kdump) on any plattform. It
doesn't work with recent kernels.


Regards,
Bernhard

Re: Linux kernel crash dumps for ARM

[Paul Mundt]

On Mon, Jan 04, 2010 at 09:20:23PM -0800, Eric W. Biederman wrote:
> Venkappa Mala <Venkappa.Mala@lntinfotech.com> writes:
> >
> > 2) As per kexec supports, kexec-tool is required and this allows you to load directly
> >    to a new kernel from the currently running one
> >
> >     As from my side, i am not able to find arm implementation support in kexec-tools/crash sources.
> >
> >    - is kexce-tool supported for ARM or not?
> >
It would be rather counterintuitive for the kernel to support kexec and
the necessary userspace components not to.

The MAINTAINERS file says:

KEXEC
M:      Eric Biederman <ebiederm@xmission.com>
W:      http://ftp.kernel.org/pub/linux/kernel/people/horms/kexec-tools/
L:      kexec@lists.infradead.org
S:      Maintained
F:      include/linux/kexec.h
F:      kernel/kexec.c

While the above URL redirects to gitweb, resulting in:

http://git.kernel.org/?p=linux/kernel/git/horms/kexec-tools.git;a=summary

A peripheral grep of the kexec-tools source results in:

$ git grep kdump | grep arm
kexec/arch/arm/kexec-arm.c:     return 0; /* kdump is not supported on this platform (yet) */

So one could infer that kexec is supported on ARM whilst kdump is not. Adding
crashdump support requires both some kernel and kexec-tools glue, but is fairly
straightforward, just look at the other ports.

Re: Linux kernel crash dumps for ARM

[Simon Horman]

On Tue, Jan 05, 2010 at 05:48:51PM +0900, Paul Mundt wrote:
> On Mon, Jan 04, 2010 at 09:20:23PM -0800, Eric W. Biederman wrote:
> > Venkappa Mala <Venkappa.Mala@lntinfotech.com> writes:
> > >
> > > 2) As per kexec supports, kexec-tool is required and this allows you to load directly
> > >    to a new kernel from the currently running one
> > >
> > >     As from my side, i am not able to find arm implementation support in kexec-tools/crash sources.
> > >
> > >    - is kexce-tool supported for ARM or not?
> > >
> It would be rather counterintuitive for the kernel to support kexec and
> the necessary userspace components not to.
> 
> The MAINTAINERS file says:
> 
> KEXEC
> M:      Eric Biederman <ebiederm@xmission.com>
> W:      http://ftp.kernel.org/pub/linux/kernel/people/horms/kexec-tools/
> L:      kexec@lists.infradead.org
> S:      Maintained
> F:      include/linux/kexec.h
> F:      kernel/kexec.c
> 
> While the above URL redirects to gitweb, resulting in:
> 
> http://git.kernel.org/?p=linux/kernel/git/horms/kexec-tools.git;a=summary
> 
> A peripheral grep of the kexec-tools source results in:
> 
> $ git grep kdump | grep arm
> kexec/arch/arm/kexec-arm.c:     return 0; /* kdump is not supported on this platform (yet) */
> 
> So one could infer that kexec is supported on ARM whilst kdump is not.
> Adding crashdump support requires both some kernel and kexec-tools glue,
> but is fairly straightforward, just look at the other ports.

To add to this, my understanding is that kexec support varies across
different ARM platforms - that is to say, it works on some and fails on
others. While this seems to be slowly improving, I'm also aware of any list
of what is supported and what isn't.

Re: Linux kernel crash dumps for ARM

[Russell King]

On Tue, Jan 05, 2010 at 08:16:28PM +1100, Simon Horman wrote:
> To add to this, my understanding is that kexec support varies across
> different ARM platforms - that is to say, it works on some and fails on
> others. While this seems to be slowly improving, I'm also aware of any list
> of what is supported and what isn't.

I'm unaware of that; the only area of weakness with kexec that I'm
aware of is when the ARMv7 processor support didn't implement the
necessary code to bring the caches/mmu/tlbs into a safe state for
software-reboot, which is also what's required by kexec.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:

Re: Linux kernel crash dumps for ARM

[Simon Horman]

On Tue, Jan 05, 2010 at 07:00:47PM +0000, Russell King wrote:
> On Tue, Jan 05, 2010 at 08:16:28PM +1100, Simon Horman wrote:
> > To add to this, my understanding is that kexec support varies across
> > different ARM platforms - that is to say, it works on some and fails on
> > others. While this seems to be slowly improving, I'm also aware of any list
> > of what is supported and what isn't.
> 
> I'm unaware of that; the only area of weakness with kexec that I'm
> aware of is when the ARMv7 processor support didn't implement the
> necessary code to bring the caches/mmu/tlbs into a safe state for
> software-reboot, which is also what's required by kexec.

Ok, I could well be mistaken and its just ARMv7 that has a few issues
at this time.