Re: [PATCH v3 2/8] xen/hypfs: switch write function handles to const

[Jan Beulich <jbeulich@xxxxxxxx>]

On 16.12.2020 17:17, Jürgen Groß wrote:
> On 16.12.20 17:08, Jan Beulich wrote:
>> On 09.12.2020 17:09, Juergen Gross wrote:
>>> --- a/xen/include/xen/guest_access.h
>>> +++ b/xen/include/xen/guest_access.h
>>> @@ -26,6 +26,11 @@
>>>       type *_x = (hnd).p;                         \
>>>       (XEN_GUEST_HANDLE_PARAM(type)) { _x };      \
>>>   })
>>> +/* Same for casting to a const type. */
>>> +#define guest_handle_const_cast(hnd, type) ({       \
>>> +    const type *_x = (const type *)((hnd).p);       \
>>> +    (XEN_GUEST_HANDLE_PARAM(const_##type)) { _x };  \
>>> +})
>>
>> Afaict this allow casting from e.g. uint to const_ulong. We
>> don't want to permit this (i.e. if really needed one is to
>> go through two steps). I think all it takes is dropping the
>> cast:
>>
>> #define guest_handle_const_cast(hnd, type) ({      \
>>      const type *_x = (hnd).p;                      \
>>      (XEN_GUEST_HANDLE_PARAM(const_##type)) { _x }; \
>> })
>>
>> With this
>> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
>> and I'd be okay making the adjustment while committing
>> (provided it works and I didn't overlook anything).
> 
> At least it is still compiling, and I guess that was the main
> concern.

Indeed. Thanks for checking.

Jan