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Old 04-18-2012, 06:44 AM
Mike Schmidt
 
Default How to handle kABI when patching kernel

Hi,

I've generated (via rpmbuild) a patched version of the latest CentoS 6.2 kernel (2.6.32-220.7.1)* with the imq patchset (http://www.linuximq.net/patches.html), but this causes the kABI to break. What can orshould I do about this, if anything?


What kinds of changes cause the kABI to break? Would it be reasonable to think I might be able to fix the patch to be kABI compliant?
Is the kABI for CentOS the same as the one for the upstream RHEL version?
Should I try to patch the kABI (as Oracle does in their unbreakable linux kernel)? What would be the procedure foir this?



I understand you can't help me with the patches or the kernel itself, but I was hoping you might help me understand the kABI well enough that I can handle things for there.
Thanks very much.



--
Mike SCHMIDT
CTO*


Intello Technologies Inc.
mike.schmidt@intello.com

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Old 04-18-2012, 10:43 AM
Giovanni Tirloni
 
Default How to handle kABI when patching kernel

On Wed, Apr 18, 2012 at 3:44 AM, Mike Schmidt <mike.schmidt@intello.com> wrote:


Hi,

I've generated (via rpmbuild) a patched version of the latest CentoS 6.2 kernel (2.6.32-220.7.1)* with the imq patchset (http://www.linuximq.net/patches.html), but this causes the kABI to break. What can orshould I do about this, if anything?




What kinds of changes cause the kABI to break? Would it be reasonable to think I might be able to fix the patch to be kABI compliant?
Is the kABI for CentOS the same as the one for the upstream RHEL version?
Should I try to patch the kABI (as Oracle does in their unbreakable linux kernel)? What would be the procedure foir this?




Yes, it's the same as the upstream's. You can either fix the code or disable the checks at your own risk.
http://wiki.centos.org/HowTos/Custom_Kernel#head-566abc4208fceb902d41ee82633f509dbf386a4d

http://elrepo.org/tiki/FAQhttps://bugzilla.redhat.com/show_bug.cgi?id=487763


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Old 04-18-2012, 09:32 PM
Mike Schmidt
 
Default How to handle kABI when patching kernel

On Wed, Apr 18, 2012 at 6:43 AM, Giovanni Tirloni <gtirloni@sysdroid.com> wrote:



Yes, it's the same as the upstream's. You can either fix the code or disable the checks at your own risk.
I read the information you provided, thank you very much. I as already familiar with all except the bugzilla entry. However, I still do not know exactly what kind of thing breaks the kABI, so I would not know how to identify the problem areas in the patch. Besides that, is updating the kABI a solution, or not? How the kABI mechanism works is not clearly explained from the documentation I have been able to find. Is there some documentation that describes it for kmod developers?



--
Mike SCHMIDT
CTO*


Intello Technologies Inc.
mike.schmidt@intello.com

Canada: 1-888-404-6261 x320
USA: 1-888-404-6268 x320

Mobile: 514-409-6898

www.intello.com




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Old 04-18-2012, 09:43 PM
Akemi Yagi
 
Default How to handle kABI when patching kernel

On Wed, Apr 18, 2012 at 2:32 PM, Mike Schmidt <mike.schmidt@intello.com> wrote:

> I read the information you provided, thank you very much. I as already
> familiar with all except the bugzilla entry. However, I still do not know
> exactly what kind of thing breaks the kABI, so I would not know how to
> identify the problem areas in the patch. Besides that, is updating the kABI
> a solution, or not? How the kABI mechanism works is not clearly explained
> from the documentation I have been able to find. Is there some documentation
> that describes it for kmod developers?

These documents written by Jon Masters are the best source:

http://dup.et.redhat.com/presentations/DriverUpdateProgramTechnical.pdf
http://people.redhat.com/jcm/el6/dup/docs/old/pre-release/whitepaper.pdf

Akemi

Akemi
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Old 04-18-2012, 10:33 PM
Ned Slider
 
Default How to handle kABI when patching kernel

On 18/04/12 07:44, Mike Schmidt wrote:
> Hi,
>
> I've generated (via rpmbuild) a patched version of the latest CentoS 6.2
> kernel (2.6.32-220.7.1) with the imq patchset (
> http://www.linuximq.net/patches.html), but this causes the kABI to break.
> What can orshould I do about this, if anything?

That all depends on whether a consistent kABI is important to you on
your system. It might be perfectly acceptable to you to just build your
new patched kernel and use it.

> What kinds of changes cause the kABI to break? Would it be reasonable to
> think I might be able to fix the patch to be kABI compliant?

Typically changes to whitelisted kernel interfaces (kernel symbols)
could break the kABI.

It is possible. It really depends what broke and why.

> Is the kABI for CentOS the same as the one for the upstream RHEL version?

Yes.

> Should I try to patch the kABI (as Oracle does in their unbreakable linux
> kernel)? What would be the procedure foir this?
>

Again, that depends (see above). You may be able to work around the
breakages. The first step is to identify which whitelisted interfaces
are affected.

> I understand you can't help me with the patches or the kernel itself, but I
> was hoping you might help me understand the kABI well enough that I can
> handle things for there.
>
> Thanks very much.
>

In addition to the reference material posted by Akemi, please also see
the docs here:

http://people.redhat.com/jcm/el6/dup/docs/

Hope that helps.

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Old 04-19-2012, 04:22 AM
Mike Schmidt
 
Default How to handle kABI when patching kernel

Thanks for the information. I've now read the first few documents, and they are very enlightening. I'm still working on understanding, but I believe I have a start at determining what makes the imq patch break the kabi. After I figure that out, I'll see what hte next steps might be. In the meantime, I do have a running kernel that works well, so the kABI is not a showstopper right now.


This is a fascinating subject. Thank you again for all your help.
--
Mike SCHMIDT


CTO*
Intello Technologies Inc.
mike.schmidt@intello.com

Canada: 1-888-404-6261 x320
USA: 1-888-404-6268 x320

Mobile: 514-409-6898

www.intello.com




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Old 04-19-2012, 09:52 AM
Karanbir Singh
 
Default How to handle kABI when patching kernel

Hi Mike

On 04/19/2012 05:22 AM, Mike Schmidt wrote:
> the meantime, I do have a running kernel that works well, so the kABI is
> not a showstopper right now.

Fancy contributing ( and maintaining that ) in the CentOS Plus repo ?

--
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Old 04-19-2012, 12:47 PM
Mike Schmidt
 
Default How to handle kABI when patching kernel

On Thu, Apr 19, 2012 at 5:52 AM, Karanbir Singh <mail-lists@karan.org> wrote:


Hi Mike




Fancy contributing ( and maintaining that ) in the CentOS Plus repo ?


I could do that. Even with a broken kABI?** I searched everywhere for a version of CentOS with IMQ installed, but only ClearOS had that. Having it in CentOS Plus would be cool. I'll let you know after I make a serious attempt at fixing the patch for the kABI.


*
--
Mike SCHMIDT
CTO*


Intello Technologies Inc.
mike.schmidt@intello.com

Canada: 1-888-404-6261 x320
USA: 1-888-404-6268 x320

Mobile: 514-409-6898

www.intello.com




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Old 04-19-2012, 12:53 PM
Karanbir Singh
 
Default How to handle kABI when patching kernel

On 04/19/2012 01:47 PM, Mike Schmidt wrote:
> Fancy contributing ( and maintaining that ) in the CentOS Plus repo ?
> I could do that. Even with a broken kABI? I searched everywhere for a
> version of CentOS with IMQ installed, but only ClearOS had that. Having
> it in CentOS Plus would be cool. I'll let you know after I make a
> serious attempt at fixing the patch for the kABI.
>

So, if you can get it to work with and in the plus kernel that is fine
and good - but if not, it can just go in as its own kernel as well ( it
just needs to be in the plus repo )

- KB

--
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Old 04-19-2012, 12:54 PM
Akemi Yagi
 
Default How to handle kABI when patching kernel

On Thu, Apr 19, 2012 at 5:47 AM, Mike Schmidt <mike.schmidt@intello.com> wrote:
>
>
> On Thu, Apr 19, 2012 at 5:52 AM, Karanbir Singh <mail-lists@karan.org>
> wrote:
>>
>> Hi Mike
>>
>>
>> Fancy contributing ( and maintaining that ) in the CentOS Plus repo ?
>>
>
> I could do that. Even with a broken kABI?** I searched everywhere for a
> version of CentOS with IMQ installed, but only ClearOS had that. Having it
> in CentOS Plus would be cool. I'll let you know after I make a serious
> attempt at fixing the patch for the kABI.

If no kABI breakage, the patch could easily be incorporated in the
centosplus kernel. But, yes, the kABI is a requirement for the cplus
kernel.

Akemi
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