Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls

From	Ingo Molnar <mingo@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls
Date	2016-07-18 12:00 +0200
Message-ID	<rWdvb-4xq-1@gated-at.bofh.it> (permalink)
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* Andy Lutomirski <luto@amacapital.net> wrote:

> On Thu, Jul 14, 2016 at 1:07 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > * Andy Lutomirski <luto@amacapital.net> wrote:
> >
> >> On Wed, Jul 13, 2016 at 12:56 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >> >
> >> > * Andy Lutomirski <luto@amacapital.net> wrote:
> >> >
> >> >> > If we push a PKRU value into a thread between the rdpkru() and wrpkru(), we'll
> >> >> > lose the content of that "push".  I'm not sure there's any way to guarantee
> >> >> > this with a user-controlled register.
> >> >>
> >> >> We could try to insist that user code uses some vsyscall helper that tracks
> >> >> which bits are as-yet-unassigned.  That's quite messy, though.
> >> >
> >> > Actually, if we turned the vDSO into something more like a minimal user-space
> >> > library with the ability to run at process startup as well to prepare stuff
> >> > then it's painful to get right only *once*, and there will be tons of other
> >> > areas where a proper per thread data storage on the user-space side would be
> >> > immensely useful!
> >>
> >> Doing this could be tricky: how exactly is the vDSO supposed to find per-thread
> >> data without breaking existing glibc?
> >
> > So I think the way this could be done is by allocating it itself. The vDSO vma
> > itself is 'external' to glibc as well to begin with - this would be a small
> > extension to that concept.
> 
> But how does the vdso code find it?  FS and GS are both spoken for by existing 
> userspace.

Minimally relinking itself on a per mm basis?

Thanks,

	Ingo

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Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Andy Lutomirski <luto@amacapital.net> - 2016-07-11 06:30 +0200
  Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Ingo Molnar <mingo@kernel.org> - 2016-07-11 09:40 +0200
    Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Dave Hansen <dave@sr71.net> - 2016-07-11 16:30 +0200
      Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Ingo Molnar <mingo@kernel.org> - 2016-07-12 09:20 +0200
        Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Dave Hansen <dave@sr71.net> - 2016-07-12 17:40 +0200
    Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Andy Lutomirski <luto@amacapital.net> - 2016-07-11 17:00 +0200
  Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Dave Hansen <dave@sr71.net> - 2016-07-11 16:40 +0200
    Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Andy Lutomirski <luto@amacapital.net> - 2016-07-11 16:50 +0200
      Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Dave Hansen <dave.hansen@intel.com> - 2016-07-11 17:50 +0200
        Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Andy Lutomirski <luto@amacapital.net> - 2016-07-12 18:40 +0200
          Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Dave Hansen <dave.hansen@intel.com> - 2016-07-12 19:20 +0200
            Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Andy Lutomirski <luto@amacapital.net> - 2016-07-13 01:00 +0200
          Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Ingo Molnar <mingo@kernel.org> - 2016-07-13 10:00 +0200
            Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Andy Lutomirski <luto@amacapital.net> - 2016-07-13 20:50 +0200
              Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Ingo Molnar <mingo@kernel.org> - 2016-07-14 10:10 +0200
                Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Andy Lutomirski <luto@amacapital.net> - 2016-07-18 06:50 +0200
                Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls Ingo Molnar <mingo@kernel.org> - 2016-07-18 12:00 +0200

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