Re: [PATCH] x86/fpu: move FPU state into separate cache

From	Andy Lutomirski <luto@amacapital.net>
Newsgroups	linux.kernel
Subject	Re: [PATCH] x86/fpu: move FPU state into separate cache
Date	2017-03-29 23:40 +0200
Message-ID	<tqttV-4o9-41@gated-at.bofh.it> (permalink)
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On Wed, Mar 29, 2017 at 2:30 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Wed, Mar 29, 2017 at 2:09 PM, Kees Cook <keescook@chromium.org> wrote:
>>
>> They're adjacent already, which poses a problem for the struct layout
>> randomization plugin, since adjacency may no longer be true (after
>> layout randomization). T
>
> What?
>
> The layout randomization can't change anything, if you just make the
> adjacency be done explicitly instead of by having the thing be a fixed
> member.
>
> The trivial model might be to just declare the fpu part as an unsized
> array at the end:
>
>         /* Floating point and extended processor state */
>         struct fpu              fpu[];
>
> because there is no way in hell that any randomization code can move
> those kinds of unsized arrays around. If it does, the gcc plugin is
> such unbelievable garbage that it would be insane to depend on such
> shit in the first place.
>

Randomization also needs to leave thread_info at the beginning.  Can it do that?

Thread

[PATCH] x86/fpu: move FPU state into separate cache Kees Cook <keescook@chromium.org> - 2017-03-29 22:50 +0200
  Re: [PATCH] x86/fpu: move FPU state into separate cache "H. Peter Anvin" <hpa@zytor.com> - 2017-03-29 23:10 +0200
    Re: [PATCH] x86/fpu: move FPU state into separate cache Kees Cook <keescook@chromium.org> - 2017-03-29 23:20 +0200
      Re: [PATCH] x86/fpu: move FPU state into separate cache Dave Hansen <dave.hansen@linux.intel.com> - 2017-03-29 23:20 +0200
      Re: [PATCH] x86/fpu: move FPU state into separate cache Linus Torvalds <torvalds@linux-foundation.org> - 2017-03-29 23:40 +0200
        Re: [PATCH] x86/fpu: move FPU state into separate cache Andy Lutomirski <luto@amacapital.net> - 2017-03-29 23:40 +0200
          Re: [PATCH] x86/fpu: move FPU state into separate cache Linus Torvalds <torvalds@linux-foundation.org> - 2017-03-29 23:50 +0200
            Re: [PATCH] x86/fpu: move FPU state into separate cache hpa@zytor.com - 2017-03-30 00:50 +0200
              Re: [PATCH] x86/fpu: move FPU state into separate cache Linus Torvalds <torvalds@linux-foundation.org> - 2017-03-30 02:00 +0200
                Re: [PATCH] x86/fpu: move FPU state into separate cache Kees Cook <keescook@chromium.org> - 2017-03-30 04:00 +0200
        Re: [PATCH] x86/fpu: move FPU state into separate cache Linus Torvalds <torvalds@linux-foundation.org> - 2017-03-29 23:40 +0200

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