Re: [PATCH v3 1/7] x86/sgx: Provide indication of life-cycle of EPC pages

[Dave Hansen]

On 7/28/21 3:57 PM, Luck, Tony wrote:
>> Wouldn't it be safer to do something like:
>>
>> 	page->owner = owner ? owner : (void *)-1;
>>
>> -1 is non-NULL, but also invalid, which makes it harder for us to poke
>> ourselves in the eye.
> Does Linux have some #define INVALID_POINTER thing that
> provides a guaranteed bad (e.g. non-canonical) value?
> 
> (void *)-1 seems hacky.

ERR_PTR(-SOMETHING) wouldn't be too bad.  I guess it could even be:

	page->owner = ERR_PTR(SGX_EPC_PAGE_VA);

and then:

#define SGX_EPC_PAGE_VA 0xffff...something...greppable

I *thought* we had a file full of these magic values, but maybe I'm
misremembering the uapi magic header.