Hi Petr,
Sorry for taking so long...
On Thu, Oct 03, 2019 at 11:01:35AM +0200, Petr Mladek wrote:
> diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
> index 726947338fd5..42907c4a0ce8 100644
> --- a/include/linux/livepatch.h
> +++ b/include/linux/livepatch.h
> @@ -133,10 +133,12 @@ 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)
Is it necessary to assume that 'version' is non-zero? It would be easy
for a user to not realize that and start with version 0. Then the patch
state would be silently ignored.
I have the same concern about 'id', but I guess at least one of them has
to be non-zero to differentiate valid entries from the array terminator.
> +/* Check if the patch is able to deal with the given system state. */
> +static bool klp_is_state_compatible(struct klp_patch *patch,
> + struct klp_state *state)
> +{
> + struct klp_state *new_state;
> +
> + new_state = klp_get_state(patch, state->id);
> +
> + if (new_state)
> + return new_state->version >= state->version;
> +
> + /* Cumulative livepatch must handle all already modified states. */
> + return !patch->replace;
> +}
>From my perspective I view '!new_state' as an error condition. I'd find
it easier to read if the ordering were changed to check for the error
first:
if (!new_state) {
/*
* A cumulative livepatch must handle all already
* modified states.
*/
return !patch->replace;
}
return new_state->version >= state->version;
> +
> +/*
> + * Check that the new livepatch will not break the existing system states.
> + * Cumulative patches must handle all already modified states.
> + * Non-cumulative patches can touch already modified states.
> + */
> +bool klp_is_patch_compatible(struct klp_patch *patch)
> +{
> + struct klp_patch *old_patch;
> + struct klp_state *state;
> +
> +
> + klp_for_each_patch(old_patch) {
Extra newline above.
> + klp_for_each_state(old_patch, state) {
> + if (!klp_is_state_compatible(patch, state))
> + return false;
> + }
> + }
I think renaming 'state' to 'old_state' would make the intention a
little clearer, and would be consistent with 'old_patch'.
--
Josh
