From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
Borislav Petkov <bp@suse.de>,
Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>
Subject: Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES
Date: Mon, 22 Feb 2016 12:48:29 -0800 [thread overview]
Message-ID: <20160222204828.GC4140@test-lenovo> (raw)
In-Reply-To: <56CB68C2.6010003@linux.intel.com>
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
next prev parent reply other threads:[~2016-02-22 20:50 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-22 19:00 [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES Yu-cheng Yu
2016-02-22 20:00 ` Dave Hansen
2016-02-22 20:48 ` Yu-cheng Yu [this message]
2016-02-22 22:19 ` Dave Hansen
2016-02-22 22:29 ` Yu-cheng Yu
2016-02-22 22:45 ` Andy Lutomirski
2016-02-22 22:50 ` Yu-cheng Yu
2016-02-22 22:53 ` Dave Hansen
2016-02-22 22:55 ` Andy Lutomirski
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