Re: [Xen-devel] [PATCH V4 6/8] iommu/arm: Add lightweight iommu_fwspec support

[Oleksandr <olekstysh@xxxxxxxxx>]

On 16.09.19 13:40, Jan Beulich wrote:

Hi, Jan

> > +
> > +/* per-device IOMMU instance data */
> > +struct iommu_fwspec {
> > +    /* this device's IOMMU */
> > +    struct device *iommu_dev;
> > +    /* IOMMU driver private data for this device */
> > +    void *iommu_priv;
> > +    /* number of associated device IDs */
> > +    unsigned int num_ids;
> > +    /* IDs which this device may present to the IOMMU */
> > +    uint32_t ids[1];
> > +};
> Note that you abuse xrealloc_flex_struct() when using it with such
> a type: The last field is _not_ a flexible array member. Compilers
> might legitimately warn if they can prove that you access
> p->ids[1] anywhere, despite you (presumably) having allocated enough
> space. (I haven't been able to think of a way for the macro to
> actually detect and hence refuse such wrong uses.)
Indeed, you are right. I am in doubt, whether to retain ported from 
Linux code (ids[1])
and mention about such abuse or change it to deal with real flexible 
array member (ids[]). Any thoughts?
--
Regards,

Oleksandr Tyshchenko


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