linux-kernel - Re: [GIT pull] x86 mpx support for 3.19

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Date:	Fri, 12 Dec 2014 07:47:32 -0800
From:	Dave Hansen <dave.hansen@...ux.intel.com>
To:	Pavel Machek <pavel@....cz>
CC:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [GIT pull] x86 mpx support for 3.19

On 12/12/2014 04:30 AM, Pavel Machek wrote:
>> +	depends on CPU_SUP_INTEL
>> +	---help---
>> +	  MPX provides hardware features that can be used in
>> +	  conjunction with compiler-instrumented code to check
>> +	  memory references.  It is designed to detect buffer
>> +	  overflow or underflow bugs.
>> +
>> +	  This option enables running applications which are
>> +	  instrumented or otherwise use MPX.  It does not use MPX
>> +	  itself inside the kernel or to protect the kernel
>> +	  against bad memory references.
>> +
>> +	  Enabling this option will make the kernel larger:
>> +	  ~8k of kernel text and 36 bytes of data on a 64-bit
>> +	  defconfig.  It adds a long to the 'mm_struct' which
>> +	  will increase the kernel memory overhead of each
>> +	  process and adds some branches to paths used during
>> +	  exec() and munmap().
> 
> Should you explain what kind of CPUs support it? Basically "the kind
> you don't have, yet"?

On a practical level, you can look for mpx in cpuinfo a la:

	cat /proc/cpuinfo  | grep ' mpx '

to see if your CPU supports it.  I will mention that in the the
Documentation/ and also point folks there from the Kconfig text.


View attachment "x86-mpx-real-config-option-v4.patch" of type "text/x-patch" (3053 bytes)