On Tue 2019-06-11 15:56:25, Petr Mladek wrote:
> 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.
>
> Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
> ---
> include/linux/livepatch.h | 2 ++
> kernel/livepatch/core.c | 8 ++++++++
> kernel/livepatch/state.c | 40 +++++++++++++++++++++++++++++++++++++++-
> kernel/livepatch/state.h | 9 +++++++++
> 4 files changed, 58 insertions(+), 1 deletion(-)
> create mode 100644 kernel/livepatch/state.h
>
> diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
> index 591abdee30d7..8bc4c6cc3f3f 100644
> --- a/include/linux/livepatch.h
> +++ b/include/linux/livepatch.h
> @@ -135,10 +135,12 @@ struct klp_object {
> /**
> * struct klp_state - state of the system modified by the livepatch
> * @id: system state identifier (non zero)
> + * @version: version of the change (non-zero)
> * @data: custom data
> */
> struct klp_state {
> int id;
As suggested by Nicolay, there will be in v2:
unsigned long id;
> + int version;
It would make sense to make "version" unsigned as well.
I am just unsure about the size:
+ "unsigned long" looks like an overhead to me
+ "u8" might be enough
But I would stay on the safe side and use:
unsigned int version;
Is anyone against?
Best Regards,
Petr
