Re: [PATCH/RFC 7/7] kernel: Force ACCESS_ONCE to work only on scalar types

[Alexei Starovoitov]

On Mon, Nov 24, 2014 at 5:30 AM, David Howells <dhowells@xxxxxxxxxx> wrote:
> Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote:
>
>> +#define get_scalar_volatile_pointer(x) ({ \
>> +     typeof(x) *__p = &(x); \
>> +     volatile typeof(x) *__vp = __p; \
>> +     (void)(long)*__p; __vp; })
>> +#define ACCESS_ONCE(x) (*get_scalar_volatile_pointer(x))

If the goal is to catch non-scalar users, the following is shorter:
#define ACCESS_ONCE(x) (((typeof(x))0) + *(volatile typeof(x) *)&(x))

it will block union and struct accesses.
If you want to allow union and disallow struct, then replace + with ,
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