Re: [RFC 9/9] x86/mm: Implement PR_SET/GET_TAGGED_ADDR_CTRL with LAM

[Dmitry Vyukov]

On Fri, Feb 5, 2021 at 4:43 PM H.J. Lu <hjl.tools@xxxxxxxxx> wrote:
>
> On Fri, Feb 5, 2021 at 7:16 AM Kirill A. Shutemov
> <kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
> >
> > Provide prctl() interface to enabled LAM for user addresses. Depending
> > how many tag bits requested it may result in enabling LAM_U57 or
> > LAM_U48.
>
> I prefer the alternate kernel interface based on CET arch_prctl interface which
> is implemented in glibc on users/intel/lam/master branch:
>
> https://gitlab.com/x86-glibc/glibc/-/tree/users/intel/lam/master
>
> and in GCC on users/intel/lam/master branch:
>
> https://gitlab.com/x86-gcc/gcc/-/tree/users/intel/lam/master

Hi Kirill, H.J.,

I don't have strong preference for PR_SET/GET_TAGGED_ADDR_CTRL vs
ARCH_X86_FEATURE_1_ENABLE itself, but tying LAM to ELF and
GNU_PROPERTY in the second option looks strange. LAM can be used
outside of ELF/GNU, right?