linux-kernel - [PATCH 2/5] x86/mpx: remove build infrastructure

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Message-Id: <20200123190500.9119F8F4@viggo.jf.intel.com>
Date:   Thu, 23 Jan 2020 11:05:00 -0800
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     linux-kernel@...r.kernel.org
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>, peterz@...radead.org,
        luto@...nel.org, x86@...nel.org, torvalds@...ux-foundation.org,
        akpm@...ux-foundation.org
Subject: [PATCH 2/5] x86/mpx: remove build infrastructure


From: Dave Hansen <dave.hansen@...ux.intel.com>

MPX is being removed from the kernel due to a lack of support
in the toolchain going forward (gcc).

Remove the Kconfig option and the Makefile line.  This makes
arch/x86/mm/mpx.c and anything under an #ifdef for
X86_INTEL_MPX dead code.

Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: x86@...nel.org
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
---

 b/arch/x86/Kconfig     |   28 ----------------------------
 b/arch/x86/mm/Makefile |    1 -
 2 files changed, 29 deletions(-)

diff -puN arch/x86/Kconfig~mpx-remove-build arch/x86/Kconfig
--- a/arch/x86/Kconfig~mpx-remove-build	2020-01-23 10:41:04.863942440 -0800
+++ b/arch/x86/Kconfig	2020-01-23 10:41:04.869942440 -0800
@@ -1896,34 +1896,6 @@ config X86_INTEL_UMIP
 	  specific cases in protected and virtual-8086 modes. Emulated
 	  results are dummy.
 
-config X86_INTEL_MPX
-	prompt "Intel MPX (Memory Protection Extensions)"
-	def_bool n
-	# Note: only available in 64-bit mode due to VMA flags shortage
-	depends on CPU_SUP_INTEL && X86_64
-	select ARCH_USES_HIGH_VMA_FLAGS
-	---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.rst
-
-	  If unsure, say N.
-
 config X86_INTEL_MEMORY_PROTECTION_KEYS
 	prompt "Intel Memory Protection Keys"
 	def_bool y
diff -puN arch/x86/mm/Makefile~mpx-remove-build arch/x86/mm/Makefile
--- a/arch/x86/mm/Makefile~mpx-remove-build	2020-01-23 10:41:04.865942440 -0800
+++ b/arch/x86/mm/Makefile	2020-01-23 10:41:04.870942440 -0800
@@ -45,7 +45,6 @@ obj-$(CONFIG_AMD_NUMA)		+= amdtopology.o
 obj-$(CONFIG_ACPI_NUMA)		+= srat.o
 obj-$(CONFIG_NUMA_EMU)		+= numa_emulation.o
 
-obj-$(CONFIG_X86_INTEL_MPX)			+= mpx.o
 obj-$(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS)	+= pkeys.o
 obj-$(CONFIG_RANDOMIZE_MEMORY)			+= kaslr.o
 obj-$(CONFIG_PAGE_TABLE_ISOLATION)		+= pti.o
_