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

Florian Weimer
2020-08-27T13:44:02Z

* H. J. Lu:

> On Thu, Aug 27, 2020 at 6:19 AM Florian Weimer <fweimer@redhat.com> wrote:
>>
>> * Dave Martin:
>>
>> > You're right that this has implications: for i386, libc probably pulls
>> > more arguments off the stack than are really there in some situations.
>> > This isn't a new problem though. There are already generic prctls with
>> > fewer than 4 args that are used on x86.
>>
>> As originally posted, glibc prctl would have to know that it has to pull
>> an u64 argument off the argument list for ARCH_X86_CET_DISABLE. But
>> then the u64 argument is a problem for arch_prctl as well.
>>
>
> Argument of ARCH_X86_CET_DISABLE is int and passed in register.

The commit message and the C source say otherwise, I think (not sure
about the C source, not a kernel hacker).

Thanks,
Florian