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

From "H. Peter Anvin" <hpa@zytor.com>
Newsgroups linux.kernel
Subject Re: [PATCH] x86/fpu: move FPU state into separate cache
Date 2017-03-29 23:10 +0200
Message-ID <tqt0S-4cP-13@gated-at.bofh.it> (permalink)
References <tqsHv-3Oj-9@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On 03/29/17 13:39, Kees Cook wrote:
> This removes ARCH_WANTS_DYNAMIC_TASK_STRUCT from x86, leaving only s390
> still defining this config.
> 
> In order to support future structure layout randomization of the
> task_struct, none of the structure fields are allowed to have a specific
> position or dynamic size. To enable randomization of task_struct on
> x86, the FPU state must be moved to its own dynamically sized cache,
> and dereferenced from the task_struct.
> 
> This change is nearly identical to what was done in grsecurity to support
> structure layout randomization. Hopefully I found all the needed changes.
> This passes allyesconfig, and boot tests.

Is this really what we want to happen?  It seems much more sane to
simply make them adjacent; they don't need to be part of the same
structure (in practice, there are three objects: thread_info,
task_struct, and the FPU state.)

	-hpa

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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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