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Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES

From Yu-cheng Yu <yu-cheng.yu@intel.com>
Newsgroups linux.kernel
Subject Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES
Date 2016-02-22 22:00 +0100
Message-ID <r55Kj-2Wr-23@gated-at.bofh.it> (permalink)
References <r541P-1YW-7@gated-at.bofh.it> <r54XU-2FL-9@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Mon, Feb 22, 2016 at 12:00:02PM -0800, Dave Hansen wrote:
> On 02/22/2016 11:00 AM, Yu-cheng Yu wrote:
> > +	if (xsave->header.xfeatures & XFEATURE_MASK_SUPERVISOR)
> > +		xsave->header.xfeatures = xfeatures | XFEATURE_MASK_SUPERVISOR;
> > +	else
> > +		xsave->header.xfeatures = xfeatures;
> 
> This is dangerous.  It says, "if any supervisor feature bit is set, then
> set *ALL* of the known bits".  There's no way that can work.
> 
> Don't you just want to or in the new bits that were in the passed-in
> 'xfeatures':
> 
> 	xsave->header.xfeatures |= xfeatures;
> 
> 'xfeatures' is known not to contain any supervisor bits.
> 

It should have been:

	xsave->header.xfeatures = xfeatures |
		(xsave->header.xfeatures & XFEATURE_MASK_SUPERVISOR);

I'll fix it.

--Yu-cheng

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Thread

[PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-02-22 20:10 +0100
  Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES Dave Hansen <dave.hansen@linux.intel.com> - 2016-02-22 21:10 +0100
    Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-02-22 22:00 +0100
      Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES Dave Hansen <dave.hansen@linux.intel.com> - 2016-02-22 23:20 +0100
        Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-02-22 23:40 +0100
  Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES Andy Lutomirski <luto@amacapital.net> - 2016-02-22 23:50 +0100
    Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES Andy Lutomirski <luto@amacapital.net> - 2016-02-23 00:00 +0100
    Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-02-23 00:00 +0100
    Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES Dave Hansen <dave.hansen@linux.intel.com> - 2016-02-23 00:00 +0100

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