Groups > linux.kernel > #1201564

Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation

From	Ingo Molnar <mingo@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation
Date	2015-08-06 10:30 +0200
Message-ID	<pUoIP-3l2-33@gated-at.bofh.it> (permalink)
References	(1 earlier) <pU4h3-75Y-5@gated-at.bofh.it> <pU81j-483-1@gated-at.bofh.it> <pUnD4-1Ok-13@gated-at.bofh.it> <pUoIP-3l2-25@gated-at.bofh.it> <pUoIP-3l2-23@gated-at.bofh.it>
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* Ingo Molnar <mingo@kernel.org> wrote:

> 
> * Linus Torvalds <torvalds@linux-foundation.org> wrote:
> 
> > On Aug 6, 2015 10:15 AM, "Ingo Molnar" <mingo@kernel.org> wrote:
> > >
> > > What sense does it make to have a blob we don't know the exact layout of? How 
> > > will debuggers or user-space in general be able to print (and change) the 
> > > register values if they don't know the layout?
> > 
> > The usage model is that you only use this for saving and restoring state.
> > 
> > If you look at the state, you restore the state and then you look at the 
> > registers. You never look at the blob itself.
> 
> So we are relying on the saved structure already in a couple of cases, such as MPX 
> exception handling:
> 
>         /*
>          * We need to look at BNDSTATUS to resolve this exception.
>          * A NULL here might mean that it is in its 'init state',
>          * which is all zeros which indicates MPX was not
>          * responsible for the exception.
>          */
>         bndcsr = get_xsave_field_ptr(XSTATE_BNDCSR);
>         if (!bndcsr)
>                 goto exit_trap;
> 
>         trace_bounds_exception_mpx(bndcsr);
> 
> get_xsave_field_ptr() very much knows about the structure.

Correction:

  get_xsave_field_ptr() users very much know about the structure.

Thanks,

	Ingo
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Thread

Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation Ingo Molnar <mingo@kernel.org> - 2015-08-05 12:40 +0200
  Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation Dave Hansen <dave@sr71.net> - 2015-08-05 16:40 +0200
    Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation Ingo Molnar <mingo@kernel.org> - 2015-08-06 09:20 +0200
      Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation Ingo Molnar <mingo@kernel.org> - 2015-08-06 10:30 +0200
        Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation Ingo Molnar <mingo@kernel.org> - 2015-08-06 10:30 +0200
        Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation Dave Hansen <dave@sr71.net> - 2015-08-06 17:00 +0200
          Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation Dave Hansen <dave.hansen@linux.intel.com> - 2015-08-06 18:10 +0200
          Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation Ingo Molnar <mingo@kernel.org> - 2015-08-08 11:20 +0200
      Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation Dave Hansen <dave@sr71.net> - 2015-08-06 19:20 +0200
        Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation Ingo Molnar <mingo@kernel.org> - 2015-08-08 11:10 +0200
          Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation Dave Hansen <dave@sr71.net> - 2015-08-10 23:20 +0200

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