Re: [PATCH v1 04/14] tee: shm: add page accessor functions

[Volodymyr Babchuk]

Hi Yury,

On 29.09.17 01:14, Yury Norov wrote:
> Hi Volodymyr,
>
> On Thu, Sep 28, 2017 at 09:04:01PM +0300, Volodymyr Babchuk wrote:
> > From: Volodymyr Babchuk <vlad.babchuk@xxxxxxxxx>
> >
> > In order to register a shared buffer in TEE, we need accessor
> > function that return list of pages for that buffer.
> >
> > Signed-off-by: Volodymyr Babchuk <vlad.babchuk@xxxxxxxxx>
> > ---
> >   include/linux/tee_drv.h | 14 ++++++++++++++
> >   1 file changed, 14 insertions(+)
> >
> > diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
> > index 6ba8b76..d773827 100644
> > --- a/include/linux/tee_drv.h
> > +++ b/include/linux/tee_drv.h
> > @@ -394,6 +394,20 @@ static inline size_t tee_shm_get_size(struct tee_shm *shm)
> >   }
> >   
> >   /**
> > + * tee_shm_get_pages() - Get list of pages that hold shared buffer
> > + * @shm:	Shared memory handle
> > + * @num_pages:	Number of pages will be stored there
> > + * @returns pointer to pages array
> > + */
> > +static inline struct page **tee_shm_get_pages(struct tee_shm *shm,
> > +					      size_t *num_pages)
> > +{
> > +	if (num_pages)
> > +		*num_pages = shm->num_pages;
>
> My concern is about this check
>
> The only use of the tee_shm_get_pages() I found is in patch #9:
> +               size_t page_num;
> +
> +               pages = tee_shm_get_pages(shm, &page_num);
>
> So there's no any valid scenario where you should pass NULL to the
> function. And I don't understand why you do this check.
>
> Even more, if in future there will be an occasion when function will
> be passed with NULL, the error will become hidden by this code.
Yes, I think you are right. I added that check in case someone want
to get only pointer to pages. But this is semantically invalid.
I'll remove that check. Thank you for review.