linux-kernel - [PATCH 0/2] Fix ordering of ftrace + livepatch module notifier callbacks

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Date:	Fri, 29 Jan 2016 01:43:45 -0500
From:	Jessica Yu <jeyu@...hat.com>
To:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Seth Jennings <sjenning@...hat.com>,
	Jiri Kosina <jikos@...nel.org>,
	Vojtech Pavlik <vojtech@...e.com>,
	Miroslav Benes <mbenes@...e.cz>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>
Cc:	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jessica Yu <jeyu@...hat.com>
Subject: [PATCH 0/2] Fix ordering of ftrace + livepatch module notifier callbacks

As explained here [1], livepatch modules are failing to initialize properly
because the ftrace coming module notifier (which calls
ftrace_module_enable()) runs after the livepatch module notifier (which
enables the patch(es)). Thus livepatch attempts to apply patches to modules
before ftrace_module_enable() is even called for the corresponding
module(s). Separate klp_module_notify() into coming and going notifiers
and tweak the priorities to fix the order in which the ftrace and livepatch
notifiers are called.

Tested the changes with a test livepatch module that patches 9p and nilfs2,
and verified that the issue is fixed.

Patch 1/2 based on the 'for-next' branch in livepatching -
git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching.git

Patch 2/2 based on the 'ftrace/core' branch in linux-trace -
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git

[1] http://lkml.kernel.org/g/20160128204033.GA32131@packer-debian-8-amd64.digitalocean.com

Jessica Yu (2):
  livepatch: Implement separate coming and going module notifiers
  ftrace: Adjust priority of ftrace module notifier

 kernel/livepatch/core.c | 128 +++++++++++++++++++++++++++---------------------
 kernel/trace/ftrace.c   |   7 ++-
 2 files changed, 79 insertions(+), 56 deletions(-)

-- 
2.4.3