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

[H.J. Lu]

On Thu, Aug 27, 2020 at 6:36 AM Florian Weimer <fweimer@xxxxxxxxxx> wrote:
>
> * H. J. Lu:
>
> > On Thu, Aug 27, 2020 at 6:19 AM Florian Weimer <fweimer@xxxxxxxxxx> 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).

It should read:

arch_prctl(ARCH_X86_CET_DISABLE, unsigned long features)

-- 
H.J.