Re: module: preserve Elf information for livepatch modules

Path	csiph.com!feeder.erje.net!2.us.feeder.erje.net!newsfeed.fsmpi.rwth-aachen.de!newsfeed.straub-nv.de!news.mixmin.net!aioe.org!gothmog.csi.it!bofh.it!news.nic.it!robomod
From	Jessica Yu <jeyu@redhat.com>
Newsgroups	linux.kernel
Subject	Re: module: preserve Elf information for livepatch modules
Date	Mon, 08 Feb 2016 21:40:04 +0100
Message-ID	<r00Li-1TO-57@gated-at.bofh.it> (permalink)
References	<qYgKt-1Kh-7@gated-at.bofh.it> <qYgKt-1Kh-5@gated-at.bofh.it> <r00rT-1Mq-3@gated-at.bofh.it>
X-Original-To	Josh Poimboeuf <jpoimboe@redhat.com>
MIME-Version	1.0
Content-Type	text/plain; charset=us-ascii; format=flowed
Content-Disposition	inline
X-Os	Linux eisen.io 3.16.0-4-amd64 x86_64
User-Agent	Mutt/1.5.23 (2014-03-12)
X-Scanned-By	MIMEDefang 2.68 on 10.5.11.26
Sender	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	33
Organization	linux.* mail to news gateway
X-Original-Cc	Rusty Russell <rusty@rustcorp.com.au>, Seth Jennings <sjenning@redhat.com>, Jiri Kosina <jikos@kernel.org>, Vojtech Pavlik <vojtech@suse.com>, Jonathan Corbet <corbet@lwn.net>, Miroslav Benes <mbenes@suse.cz>, linux-api@vger.kernel.org, live-patching@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, linux-doc@vger.kernel.org
X-Original-Date	Mon, 8 Feb 2016 15:34:42 -0500
X-Original-Message-ID	<20160208203441.GB27290@packer-debian-8-amd64.digitalocean.com>
X-Original-References	<1454548271-24923-1-git-send-email-jeyu@redhat.com> <1454548271-24923-3-git-send-email-jeyu@redhat.com> <20160208201039.GC23106@treble.redhat.com>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	csiph.com linux.kernel:1329545

Show key headers only | View raw

+++ Josh Poimboeuf [08/02/16 14:10 -0600]:
>On Wed, Feb 03, 2016 at 08:11:07PM -0500, Jessica Yu wrote:
>> For livepatch modules, copy Elf section, symbol, and string information
>> from the load_info struct in the module loader. Persist copies of the
>> original symbol table and string table.
>>
>> Livepatch manages its own relocation sections in order to reuse module
>> loader code to write relocations. Livepatch modules must preserve Elf
>> information such as section indices in order to apply livepatch relocation
>> sections using the module loader's apply_relocate_add() function.
>>
>> In order to apply livepatch relocation sections, livepatch modules must
>> keep a complete copy of their original symbol table in memory. Normally, a
>> stripped down copy of a module's symbol table (containing only "core"
>> symbols) is made available through module->core_symtab. But for livepatch
>> modules, the symbol table copied into memory on module load must be exactly
>> the same as the symbol table produced when the patch module was compiled.
>> This is because the relocations in each livepatch relocation section refer
>> to their respective symbols with their symbol indices, and the original
>> symbol indices (and thus the symtab ordering) must be preserved in order
>> for apply_relocate_add() to find the right symbol.
>
>This patch didn't apply clean to linux-next/master.  I didn't
>investigate why, but maybe it depends on the other patch set which
>removes the notifiers?  (If so, that should be mentioned in the cover
>letter.)

A very recent commit (8244062ef) introduced some changes
kernel/module.c that intersect with this patch, so I think this is why
the patch didn't apply cleanly to today's tree...Anyhow I will rebase
again before sending out v5. Thanks for the comments :-)

Jessica

Thread

[RFC PATCH v4 2/6] module: preserve Elf information for livepatch modules Jessica Yu <jeyu@redhat.com> - 2016-02-04 02:20 +0100
  Re: [RFC PATCH v4 2/6] module: preserve Elf information for  livepatch modules Josh Poimboeuf <jpoimboe@redhat.com> - 2016-02-08 21:20 +0100
    Re: module: preserve Elf information for livepatch modules Jessica Yu <jeyu@redhat.com> - 2016-02-08 21:40 +0100
  Re: [RFC PATCH v4 2/6] module: preserve Elf information for  livepatch modules Petr Mladek <pmladek@suse.com> - 2016-02-09 09:50 +0100
    Re: [RFC PATCH v4 2/6] module: preserve Elf information for livepatch  modules Jiri Kosina <jikos@kernel.org> - 2016-02-09 11:40 +0100
      Re: [RFC PATCH v4 2/6] module: preserve Elf information for  livepatch modules Petr Mladek <pmladek@suse.com> - 2016-02-09 13:40 +0100
        Re: [RFC PATCH v4 2/6] module: preserve Elf information for livepatch modules Rusty Russell <rusty@rustcorp.com.au> - 2016-02-10 01:30 +0100
  Re: [RFC PATCH v4 2/6] module: preserve Elf information for  livepatch modules Petr Mladek <pmladek@suse.com> - 2016-02-10 17:00 +0100

csiph-web