linux-kernel - [PATCH v2 0/3] livepatch: introduce atomic replace

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Date:   Wed, 30 Aug 2017 17:38:42 -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 v2 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 dynamic iterators
A prep patch for the 'atomic replace' feature such that dynamic objects
and functions can be allocated.

2) livepatch: add atomic replace
Core feature.

3) livepatch: Add a sysctl livepatch_mode for atomic replace
Introduces a knob for enabling atomic replace. This patch is really only
meant for testing purposes, and should not be considered for application.
The intention is for the livepatch module generator to set the 'replace'
field in the klp_patch structure such that the kernel knows to do the atomic
replace.

Thanks,

-Jason

v1-v2:                                                                                                          
-removed the func_iter and obj_iter (Petr Mladek)
-initialiing kobject structure for no_op functions using:
 klp_init_object() and klp_init_func()
-added a 'replace' field to klp_patch, similar to the immediate field
-a 'replace' patch now disables all previous patches
-tried to shorten klp_init_patch_no_ops()...
-Simplified logic klp_complete_transition (Petr Mladek)

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

 include/linux/livepatch.h     | 108 ++++++++++++++++++++++++-
 kernel/livepatch/core.c       | 182 +++++++++++++++++++++++++++++++++++++++---
 kernel/livepatch/core.h       |   5 ++
 kernel/livepatch/patch.c      |  19 +++--
 kernel/livepatch/patch.h      |   4 +-
 kernel/livepatch/transition.c |  47 ++++++++++-
 kernel/sysctl.c               |  12 +++
 7 files changed, 352 insertions(+), 25 deletions(-)

-- 
2.6.1