# Re: \[PATCH v19 24/25\] x86/cet/shstk: Add arch\_prctl functions for shadow stack

- From: Yu, Yu-cheng \<hidden\>
- Date: 2021-02-04 23:44:41 
- List: linux-doc
- Page: https://ratatoskr.run/linux-doc/2021/02/6259311
- Thread: https://ratatoskr.run/linux-doc/2021/02/6257763/t.md

```text
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
```