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

["Jürgen Groß" <jgross@suse.com>]

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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@suse.com>
> 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.


Juergen

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