> > > +/** > > > + * _klp_shadow_attach() - allocate and add a new shadow variable > > > + * @obj: pointer to original data > > > + * @num: numerical description of new data > > > + * @new_data: pointer to new data > > > + * @new_size: size of new data > > > + * @gfp_flags: GFP mask for allocation > > > + * @lock: take klp_shadow_lock during klp_shadow_hash operations > > > > I am not sure about lock argument. Do we need it? Common practice is to > > have function foo() which takes a lock, and function __foo() which does > > not. > > > > In klp_shadow_get_or_attach(), you use it as I'd expect. You take the > > spinlock, call this function and release the spinlock. Is it possible > > to do the same in klp_shadow_attach() and have __klp_shadow_attach() > > without lock argument? > > Yes, this would be possible, though it would restrict > klp_shadow_attach() from accepting gfp_flags that might allow for > sleeping. More on that below ...
Ok, that is a good remark. The problem is that it applies to klp_shadow_get_or_attach() too. There you acquire a spin_lock and call _klp_shadow_attach() with gfp_flags, which are then used for kzalloc. I might misread the code. It is getting late here. > > > + * > > > + * Note: allocates @new_size space for shadow variable data and copies > > > + * @new_size bytes from @new_data into the shadow varaible's own > > > @new_data > > > + * space. If @new_data is NULL, @new_size is still allocated, but no > > > + * copy is performed. > > > > I must say I'm not entirely happy with this. I don't know if this is what > > Petr had in mind (I'm sure he'll get to the patch set soon). Calling > > memcpy instead of a simple assignment in v1 seems worse. > > This change was a bit of a experiment on my part in reaction to > adding klp_shadow_get_or_attach(). > > I like the simplicity of v1's pointer assignment -- in fact, moving all > allocation responsiblity (klp_shadow meta-data and data[] area) out to > the caller is doable, though implementing klp_shadow_get_or_attach() and > and klp_shadow_detach_all() complicates matters, for example, adding an > alloc/release callback. I originally attempted this for v2, but turned > back when the API and implementation grew complicated. If the memcpy > and gfp_flag restrictions are too ugly, I can try revisting that > approach. Ideas welcome :) Well, I didn't like callbacks either :). And no, I do not have a better idea. I still need to think about it. Miroslav
