linux-kernel - Re: [RFC 9/9] x86/mm: Implement PR_SET/GET_TAGGED_ADDR

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Message-ID: <CACT4Y+ZN_9QB1q9+TakyDz5O6M735S=1qWc+nXkgn30Hy7_9gw@mail.gmail.com>
Date:   Sun, 7 Feb 2021 15:11:39 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     "H.J. Lu" <hjl.tools@...il.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Andi Kleen <ak@...ux.intel.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        GNU C Library <libc-alpha@...rceware.org>,
        GCC Development <gcc@....gnu.org>
Subject: Re: [RFC 9/9] x86/mm: Implement PR_SET/GET_TAGGED_ADDR_CTRL with LAM

On Sun, Feb 7, 2021 at 3:09 PM Kirill A. Shutemov <kirill@...temov.name> wrote:
>
> On Sun, Feb 07, 2021 at 09:07:02AM +0100, Dmitry Vyukov wrote:
> > On Fri, Feb 5, 2021 at 4:43 PM H.J. Lu <hjl.tools@...il.com> wrote:
> > >
> > > On Fri, Feb 5, 2021 at 7:16 AM Kirill A. Shutemov
> > > <kirill.shutemov@...ux.intel.com> 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?
>
> Sure. In both cases it's still a syscall.

Oh, I meant just the naming scheme. The consts are declared in elf.h
and are prefixed with GNU_PROPERTY.