DevHeads.net

How to handle kABI when patching kernel

By Mike Schmidt at 04/18/2012 - 02:44

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 (
<a href="http://www.linuximq.net/patches.html" title="http://www.linuximq.net/patches.html">http://www.linuximq.net/patches.html</a>), 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.

Comments

Re: How to handle kABI when patching kernel

By Ned Slider at 04/18/2012 - 18:33

On 18/04/12 07:44, Mike Schmidt wrote:
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.

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

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

Yes.

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.

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

<a href="http://people.redhat.com/jcm/el6/dup/docs/" title="http://people.redhat.com/jcm/el6/dup/docs/">http://people.redhat.com/jcm/el6/dup/docs/</a>

Hope that helps.

Re: How to handle kABI when patching kernel

By Mike Schmidt at 04/19/2012 - 00:22

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.

Re: How to handle kABI when patching kernel

By Karanbir Singh at 04/19/2012 - 05:52

Hi Mike

On 04/19/2012 05:22 AM, Mike Schmidt wrote:
Fancy contributing ( and maintaining that ) in the CentOS Plus repo ?

Re: How to handle kABI when patching kernel

By Mike Schmidt at 04/19/2012 - 08:47

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

Re: How to handle kABI when patching kernel

By Akemi Yagi at 04/19/2012 - 08:54

On Thu, Apr 19, 2012 at 5:47 AM, Mike Schmidt <mike. ... at intello dot com> wrote:
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

Re: How to handle kABI when patching kernel

By Karanbir Singh at 04/19/2012 - 08:53

On 04/19/2012 01:47 PM, Mike Schmidt wrote:
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

Re: How to handle kABI when patching kernel

By Giovanni Tirloni at 04/18/2012 - 06:43

On Wed, Apr 18, 2012 at 3:44 AM, Mike Schmidt <mike. ... at intello dot 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.

<a href="http://wiki.centos.org/HowTos/Custom_Kernel#head-566abc4208fceb902d41ee82633f509dbf386a4d" title="http://wiki.centos.org/HowTos/Custom_Kernel#head-566abc4208fceb902d41ee82633f509dbf386a4d">http://wiki.centos.org/HowTos/Custom_Kernel#head-566abc4208fceb902d41ee8...</a>
<a href="http://elrepo.org/tiki/FAQ" title="http://elrepo.org/tiki/FAQ">http://elrepo.org/tiki/FAQ</a>
<a href="https://bugzilla.redhat.com/show_bug.cgi?id=487763" title="https://bugzilla.redhat.com/show_bug.cgi?id=487763">https://bugzilla.redhat.com/show_bug.cgi?id=487763</a>

Re: How to handle kABI when patching kernel

By Mike Schmidt at 04/18/2012 - 17:32

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

Re: How to handle kABI when patching kernel

By Akemi Yagi at 04/18/2012 - 17:43

These documents written by Jon Masters are the best source:

<a href="http://dup.et.redhat.com/presentations/DriverUpdateProgramTechnical.pdf" title="http://dup.et.redhat.com/presentations/DriverUpdateProgramTechnical.pdf">http://dup.et.redhat.com/presentations/DriverUpdateProgramTechnical.pdf</a>
<a href="http://people.redhat.com/jcm/el6/dup/docs/old/pre-release/whitepaper.pdf" title="http://people.redhat.com/jcm/el6/dup/docs/old/pre-release/whitepaper.pdf">http://people.redhat.com/jcm/el6/dup/docs/old/pre-release/whitepaper.pdf</a>

Akemi

Akemi