Re: [PATCH v19 24/25] x86/cet/shstk: Add arch_prctl functions for shadow stack

Yu, Yu-cheng
2021-02-04T23:42:07Z

On 2/4/2021 12:35 PM, Kees Cook wrote:
> On Wed, Feb 03, 2021 at 02:55:46PM -0800, Yu-cheng Yu wrote:
>> arch_prctl(ARCH_X86_CET_STATUS, u64 *args)
>> Get CET feature status.
>>
>> The parameter 'args' is a pointer to a user buffer. The kernel returns
>> the following information:
>>
>> *args = shadow stack/IBT status
>> *(args + 1) = shadow stack base address
>> *(args + 2) = shadow stack size
>
> What happens if this needs to grow in the future? Should the first u64
> contain the array size?
>
> Otherwise, looks sensible.
>
> -Kees
>

The first item is a bitmap, and there are two possible bits. Should
there be a need, we can then do things about it. My thought at the
moment is, we may not meet the situation. Can we keep this for now?

--
Yu-cheng