Commit 57319d80 authored by Qiaowei Ren's avatar Qiaowei Ren Committed by Thomas Gleixner
Browse files

x86, mpx: Add MPX-specific mmap interface 



We have chosen to perform the allocation of bounds tables in
kernel (See the patch "on-demand kernel allocation of bounds
tables") and to mark these VMAs with VM_MPX.

However, there is currently no suitable interface to actually do
this.  Existing interfaces, like do_mmap_pgoff(), have no way to
set a modified ->vm_ops or ->vm_flags and don't hold mmap_sem
long enough to let a caller do it.

This patch wraps mmap_region() and hold mmap_sem long enough to
make the modifications to the VMA which we need.

Also note the 32/64-bit #ifdef in the header.  We actually need
to do this at runtime eventually.  But, for now, we don't support
running 32-bit binaries on 64-bit kernels.  Support for this will
come in later patches.

Signed-off-by: default avatarQiaowei Ren <qiaowei.ren@intel.com>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Cc: linux-mm@kvack.org
Cc: linux-mips@linux-mips.org
Cc: Dave Hansen <dave@sr71.net>
Link: http://lkml.kernel.org/r/20141114151827.CE440F67@viggo.jf.intel.com


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 4aae7e43

arch/x86/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -248,6 +248,10 @@ 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

arch/x86/include/asm/mpx.h

0 → 100644
+36 −0
Original line number Diff line number Diff line 
#ifndef _ASM_X86_MPX_H

#define _ASM_X86_MPX_H



#include <linux/types.h>

#include <asm/ptrace.h>



#ifdef CONFIG_X86_64



/* upper 28 bits [47:20] of the virtual address in 64-bit used to

 * index into bounds directory (BD).

 */

#define MPX_BD_ENTRY_OFFSET	28

#define MPX_BD_ENTRY_SHIFT	3

/* bits [19:3] of the virtual address in 64-bit used to index into

 * bounds table (BT).

 */

#define MPX_BT_ENTRY_OFFSET	17

#define MPX_BT_ENTRY_SHIFT	5

#define MPX_IGN_BITS		3



#else



#define MPX_BD_ENTRY_OFFSET	20

#define MPX_BD_ENTRY_SHIFT	2

#define MPX_BT_ENTRY_OFFSET	10

#define MPX_BT_ENTRY_SHIFT	4

#define MPX_IGN_BITS		2



#endif



#define MPX_BD_SIZE_BYTES (1UL<<(MPX_BD_ENTRY_OFFSET+MPX_BD_ENTRY_SHIFT))

#define MPX_BT_SIZE_BYTES (1UL<<(MPX_BT_ENTRY_OFFSET+MPX_BT_ENTRY_SHIFT))



#define MPX_BNDSTA_ERROR_CODE	0x3



#endif /* _ASM_X86_MPX_H */

arch/x86/mm/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -30,3 +30,5 @@ obj-$(CONFIG_ACPI_NUMA) += srat.o 
obj-$(CONFIG_NUMA_EMU)		+= numa_emulation.o



obj-$(CONFIG_MEMTEST)		+= memtest.o



obj-$(CONFIG_X86_INTEL_MPX)	+= mpx.o

arch/x86/mm/mpx.c

0 → 100644
+86 −0
Original line number Diff line number Diff line 
/*

 * mpx.c - Memory Protection eXtensions

 *

 * Copyright (c) 2014, Intel Corporation.

 * Qiaowei Ren <qiaowei.ren@intel.com>

 * Dave Hansen <dave.hansen@intel.com>

 */

#include <linux/kernel.h>

#include <linux/syscalls.h>

#include <linux/sched/sysctl.h>



#include <asm/mman.h>

#include <asm/mpx.h>



static const char *mpx_mapping_name(struct vm_area_struct *vma)

{

	return "[mpx]";

}



static struct vm_operations_struct mpx_vma_ops = {

	.name = mpx_mapping_name,

};



/*

 * This is really a simplified "vm_mmap". it only handles MPX

 * bounds tables (the bounds directory is user-allocated).

 *

 * Later on, we use the vma->vm_ops to uniquely identify these

 * VMAs.

 */

static unsigned long mpx_mmap(unsigned long len)

{

	unsigned long ret;

	unsigned long addr, pgoff;

	struct mm_struct *mm = current->mm;

	vm_flags_t vm_flags;

	struct vm_area_struct *vma;



	/* Only bounds table and bounds directory can be allocated here */

	if (len != MPX_BD_SIZE_BYTES && len != MPX_BT_SIZE_BYTES)

		return -EINVAL;



	down_write(&mm->mmap_sem);



	/* Too many mappings? */

	if (mm->map_count > sysctl_max_map_count) {

		ret = -ENOMEM;

		goto out;

	}



	/* Obtain the address to map to. we verify (or select) it and ensure

	 * that it represents a valid section of the address space.

	 */

	addr = get_unmapped_area(NULL, 0, len, 0, MAP_ANONYMOUS | MAP_PRIVATE);

	if (addr & ~PAGE_MASK) {

		ret = addr;

		goto out;

	}



	vm_flags = VM_READ | VM_WRITE | VM_MPX |

			mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;



	/* Set pgoff according to addr for anon_vma */

	pgoff = addr >> PAGE_SHIFT;



	ret = mmap_region(NULL, addr, len, vm_flags, pgoff);

	if (IS_ERR_VALUE(ret))

		goto out;



	vma = find_vma(mm, ret);

	if (!vma) {

		ret = -ENOMEM;

		goto out;

	}

	vma->vm_ops = &mpx_vma_ops;



	if (vm_flags & VM_LOCKED) {

		up_write(&mm->mmap_sem);

		mm_populate(ret, len);

		return ret;

	}



out:

	up_write(&mm->mmap_sem);

	return ret;

}

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