Messages in this thread | | | Date | Wed, 23 Oct 2019 16:15:28 -0500 | From | Josh Poimboeuf <> | Subject | Re: [PATCH v3 3/5] livepatch: Allow to distinguish different version of system state changes |
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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
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