Merge branch 'x86-mpx-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip (a5445576) · Commits · 戴 / test

Documentation/x86/intel_mpx.txt

+14 −4

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
		@@ -30,9 +34,15 @@ is how we expect the compiler, application and kernel to work together.
		instrumentation as well as some setup code called early after the app
		starts. New instruction prefixes are noops for old CPUs.
		2) That setup code allocates (virtual) space for the "bounds directory",
		points the "bndcfgu" register to the directory and notifies the kernel
		(via the new prctl(PR_MPX_ENABLE_MANAGEMENT)) that the app will be using
		MPX.
		points the "bndcfgu" register to the directory (must also set the valid
		bit) and notifies the kernel (via the new prctl(PR_MPX_ENABLE_MANAGEMENT))
		that the app will be using MPX. The app must be careful not to access
		the bounds tables between the time when it populates "bndcfgu" and
		when it calls the prctl(). This might be hard to guarantee if the app
		is compiled with MPX. You can add "__attribute__((bnd_legacy))" to
		the function to disable MPX instrumentation to help guarantee this.
		Also be careful not to call out to any other code which might be
		MPX-instrumented.
		3) The kernel detects that the CPU has MPX, allows the new prctl() to
		succeed, and notes the location of the bounds directory. Userspace is
		expected to keep the bounds directory at that locationWe note it

arch/x86/Kconfig

+26 −4

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		@@ -249,10 +249,6 @@ 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
		@@ -1594,6 +1590,32 @@ 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

arch/x86/kernel/traps.c

+1 −1

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		@@ -331,7 +331,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code)
		break; /* Success, it was handled */
		case 1: /* Bound violation. */
		info = mpx_generate_siginfo(regs, xsave_buf);
		if (PTR_ERR(info)) {
		if (IS_ERR(info)) {
		/*
		* We failed to decode the MPX instruction. Act as if
		* the exception was not caused by MPX.

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