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The atomic replace runs pre/post (un)install callbacks only from the new
livepatch. There are several reasons for this:
+ Simplicity: clear ordering of operations, no interactions between
old and new callbacks.
+ Reliability: only new livepatch knows what changes can already be made
by older livepatches and how to take over the state.
+ Testing: the atomic replace can be properly tested only when a newer
livepatch is available. It might be too late to fix unwanted effect
of callbacks from older livepatches.
It might happen that an older change is not enough and the same system
state has to be modified another way. Different changes need to get
distinguished by a version number added to struct klp_state.
The version can also be used to prevent loading incompatible livepatches.
The check is done when the livepatch is enabled. The rules are:
+ Any completely new system state modification is allowed.
+ System state modifications with the same or higher version are allowed
for already modified system states.
+ Cumulative livepatches must handle all system state modifications from
already installed livepatches.
+ Non-cumulative livepatches are allowed to touch already modified
system states.
Link: http://lkml.kernel.org/r/[email protected]
To: Jiri Kosina <[email protected]>
Cc: Kamalesh Babulal <[email protected]>
Cc: Nicolai Stange <[email protected]>
Cc: [email protected]
Cc: [email protected]
Acked-by: Miroslav Benes <[email protected]>
Acked-by: Joe Lawrence <[email protected]>
Acked-by: Josh Poimboeuf <[email protected]>
Signed-off-by: Petr Mladek <[email protected]>
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