Re: [PATCH v11 25/25] x86/cet/shstk: Add arch_prctl functions for shadow stack

Yu, Yu-cheng
2020-08-25T18:43:55Z

On 8/24/2020 5:36 PM, Andy Lutomirski wrote:
> On Mon, Aug 24, 2020 at 5:30 PM Yu-cheng Yu <yu-cheng.yu@intel.com> wrote:
>
>> arch_prctl(ARCH_X86_CET_MMAP_SHSTK, u64 *args)
>> Allocate a new shadow stack.
>>
>> The parameter 'args' is a pointer to a user buffer.
>>
>> *args = desired size
>> *(args + 1) = MAP_32BIT or MAP_POPULATE
>>
>> On returning, *args is the allocated shadow stack address.
>
> This is hideous. Would this be better as a new syscall?

Could you point out why this is hideous, so that I can modify the
arch_prctl?

I think this is more arch-specific. Even if it becomes a new syscall,
we still need to pass the same parameters.

Yu-cheng