Message-ID: <52D975A9.7050201@zytor.com>
Date: Fri, 17 Jan 2014 10:25:45 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Borislav Petkov <bp@alien8.de>
CC: Ren Qiaowei <qiaowei.ren@intel.com>, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/5] x86, mpx: hook #BR exception handler to allocate
 bound tables
References: <20140112092019.GA3664@pd.tnic> <52D35ABB.8070904@intel.com> <20140113103808.GC5388@pd.tnic> <52D95AD4.6060603@zytor.com> <20140117164855.GF8715@pd.tnic> <52D95F93.3030000@zytor.com> <20140117165656.GA9024@pd.tnic> <52D96149.8070706@zytor.com> <20140117170410.GH8715@pd.tnic> <52D968C5.9080102@zytor.com> <20140117182321.GJ8715@pd.tnic>
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On 01/17/2014 10:23 AM, Borislav Petkov wrote:
> On Fri, Jan 17, 2014 at 09:30:45AM -0800, H. Peter Anvin wrote:
>> Yes. It would take some serious effort to get BOUND or MPX
>> instructions into the kernel -- you'd have to put them in inline
>> assembly, and BOUND doesn't even exist in 64-bit mode.
> 
> Which reminds me - we will have to explicitly turn off any compiler
> switches that utilize MPX insns so that they don't get issued when
> building the kernel. Provided there will be compiler support, that is.
> 

There will be, whether or not it will be on by default is another matter.

Either way, the kernel would have to explicitly enable the use MPX
instructions in kernel space or they are simply treated as NOPs.

	-hpa

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