linux-kernel - [PATCH 0/3] livepatch: introduce atomic replace

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Date:   Wed, 19 Jul 2017 13:18:04 -0400
From:   Jason Baron <jbaron@...mai.com>
To:     linux-kernel@...r.kernel.org, live-patching@...r.kernel.org
Cc:     jpoimboe@...hat.com, jeyu@...nel.org, jikos@...nel.org,
        mbenes@...e.cz, pmladek@...e.com
Subject: [PATCH 0/3] livepatch: introduce atomic replace

Hi,

In testing livepatch, I found that when doing cumulative patches, if a patched
function is completed reverted by a subsequent patch (back to its original state)
livepatch does not revert the funtion to its original state. Specifically, if
patch A introduces a change to function 1, and patch B reverts the change to
function 1 and introduces changes to say function 2 and 3 as well, the change
that patch A introducd to function 1 is still present. This could be addressed
by first completely removing patch A (disable and then rmmod) and then inserting
patch B (insmod and enable), but this leaves an unpatched window. In discussing
this issue with Josh on the kpatch mailing list, he mentioned that we could get
'atomic replace working properly', and that is the direction of this patchset:
https://www.redhat.com/archives/kpatch/2017-June/msg00005.html

Patches:

1) livepatch: Add klp_object and klp_func iterators
	Just a prep patch for the 'atomic revert' feature

2) livepatch: add atomic replace
	Core feature

3) livepatch: Add a sysctl livepatch_mode for atomic replace
	Introduces a knob for enabling atomic replace. I hate knobs and perhaps
	its possible to default to cumulative replace? Although I suspect there
	are workflows relying on the existing behavior - I'm not sure. It may
	be desirable to associate the knob with the patch itself as in the
	'immediate' flag, such that we don't introduce a global sysctl that
	likely would also need to built-in, if there are patches in the initrd.

Thanks,

-Jason

Jason Baron (3):
  livepatch: Add klp_object and klp_func iterators
  livepatch: add atomic replace
  livepatch: Add a sysctl livepatch_mode for atomic revert

 include/linux/livepatch.h     | 118 ++++++++++++++++++++++++++++++--
 kernel/livepatch/core.c       | 154 ++++++++++++++++++++++++++++++++++++++++--
 kernel/livepatch/core.h       |   4 ++
 kernel/livepatch/patch.c      |  23 ++++---
 kernel/livepatch/patch.h      |   1 +
 kernel/livepatch/transition.c |  79 +++++++++++++++++++---
 kernel/sysctl.c               |  12 ++++
 7 files changed, 362 insertions(+), 29 deletions(-)

-- 
2.6.1