linux-kernel - Re: module: s390: keep mod_arch_specific for livepatch modules

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Date:	Fri, 5 Feb 2016 16:32:05 +0100 (CET)
From:	Miroslav Benes <mbenes@...e.cz>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
cc:	Jessica Yu <jeyu@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Seth Jennings <sjenning@...hat.com>,
	Jiri Kosina <jikos@...nel.org>,
	Vojtech Pavlik <vojtech@...e.com>,
	Jonathan Corbet <corbet@....net>, linux-api@...r.kernel.org,
	live-patching@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: Re: module: s390: keep mod_arch_specific for livepatch modules

On Thu, 4 Feb 2016, Josh Poimboeuf wrote:

> On Wed, Feb 03, 2016 at 08:37:52PM -0500, Jessica Yu wrote:
> > +++ Jessica Yu [03/02/16 20:11 -0500]:
> > >Livepatch needs to utilize the symbol information contained in the
> > >mod_arch_specific struct in order to be able to call the s390
> > >apply_relocate_add() function to apply relocations. Keep a reference to
> > >syminfo if the module is a livepatch module. Remove the redundant vfree()
> > >in module_finalize() since module_arch_freeing_init() (which also frees
> > >those structures) is called in do_init_module(). If the module isn't a
> > >livepatch module, we free the structures in module_arch_freeing_init() as
> > >usual.
> > >
> > >Signed-off-by: Jessica Yu <jeyu@...hat.com>
> > >---
> > >arch/s390/kernel/module.c | 7 +++++--
> > >1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > I must note that I have verified that the patchset boots on s390 and
> > that the sample livepatch module still works ...so that's good, but
> > not saying much since what we really want is to test the relocation
> > code. The kpatch build scripts however currently only support x86, so
> > the next step is for me to port the kpatch scripts to s390 before I
> > can really test this patchset. This in itself might take a while, so
> > in the meantime I'd like to just collect another round of comments and
> > feedback for v4.
> 
> I haven't reviewed the code yet, but otherwise I'm thinking it would
> actually be fine to merge this patch set before testing with s390
> relocations.  They aren't implemented on s390 today anyway, so there
> can't be a regression if nobody is using it.

I asked Jessica to test it with s390 relocations. It would be great to 
know it works on an architecture which originally inspired this patch set. 
However it should not be a blocker. There are advantages apart from this 
and we can happily merge it before testing.

I am going to review the patch set early next week...

Miroslav