Re: [PATCH v18 24/25] x86/cet/shstk: Add arch_prctl functions for shadow stack

Yu, Yu-cheng
2021-01-29T19:55:46Z

On 1/29/2021 11:15 AM, Dave Hansen wrote:
> On 1/29/21 10:56 AM, Yu, Yu-cheng wrote:
>> On 1/29/2021 9:07 AM, Dave Hansen wrote:
>>> On 1/27/21 1:25 PM, Yu-cheng Yu wrote:
[...]
>>> What's the point of doing copy_status_to_user() if the processor doesn't
>>> support CET?  In other words, shouldn't this be below the CPU feature
>>> check?
>>
>> The thought was to tell the difference between the kernel itself does
>> not support CET and the system does not have CET.  And, if the kernel
>> supports it, show CET status of the thread.
>
> Why would that matter to userspace?
>
> If they want to know if the processor has CET support there are existing
> ways to do it. I don't think this should be part of the ABI.
>

Ok, I will make it:

if (!cpu_feature_enabled(X86_FEATURE_CET))
...