On Wed 2019-10-23 16:15:28, Josh Poimboeuf wrote:
> 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.
Exactly. At least one struct member must be non-zero to differentiate
the array terminator.
I do not mind to allow zero version. Will do so in v4.
> > +/* 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;
-> v4
> > +
> > +/*
> > + * 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'.
Makes sense. I'll make the names consistent also in klp_is_state_compatible():
/* 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 *old_state)
{
struct klp_state *state = klp_get_state(patch, state->id);
if (!state) {
/*
* A cumulative livepatch must handle all already
* modified states.
*/
return !patch->replace;
}
return state->version >= old_state->version;
}
Best Regards,
Petr
