Commit 72e9b5fe authored by Dave Hansen's avatar Dave Hansen Committed by Thomas Gleixner
Browse files

x86, mpx: Give MPX a real config option prompt 

Give MPX a real config option. The CPUs that support it (referenced
here):

  https://software.intel.com/en-us/forums/topic/402393



are not available publicly yet. Right now only the software emulator
provides MPX for the general public.

[ tglx: Make it default off. There is no point in having it on right
        now as no hardware and no proper tooling support are available ]

Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Hansen <dave@sr71.net>
Link: http://lkml.kernel.org/r/20141212183836.2569D58D@viggo.jf.intel.com


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 010e593b

Documentation/x86/intel_mpx.txt

+5 −1
Original line number Diff line number Diff line
@@ -7,11 +7,15 @@ that can be used in conjunction with compiler changes to check memory 
references, for those references whose compile-time normal intentions are

usurped at runtime due to buffer overflow or underflow.



You can tell if your CPU supports MPX by looking in /proc/cpuinfo:



	cat /proc/cpuinfo  | grep ' mpx '



For more information, please refer to Intel(R) Architecture Instruction

Set Extensions Programming Reference, Chapter 9: Intel(R) Memory Protection

Extensions.



Note: Currently no hardware with MPX ISA is available but it is always

Note: As of December 2014, no hardware with MPX is available but it is

possible to use SDE (Intel(R) Software Development Emulator) instead, which

can be downloaded from

http://software.intel.com/en-us/articles/intel-software-development-emulator

arch/x86/Kconfig

+26 −4
Original line number Diff line number Diff line
@@ -248,10 +248,6 @@ config HAVE_INTEL_TXT 
	def_bool y

	depends on INTEL_IOMMU && ACPI



config X86_INTEL_MPX

	def_bool y

	depends on CPU_SUP_INTEL



config X86_32_SMP

	def_bool y

	depends on X86_32 && SMP
@@ -1575,6 +1571,32 @@ config X86_SMAP 


	  If unsure, say Y.



config X86_INTEL_MPX

	prompt "Intel MPX (Memory Protection Extensions)"

	def_bool n

	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().



	  For details, see Documentation/x86/intel_mpx.txt



	  If unsure, say N.



config EFI

	bool "EFI runtime service support"

	depends on ACPI

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