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

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.comSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 4aae7e43
...@@ -248,6 +248,10 @@ config HAVE_INTEL_TXT ...@@ -248,6 +248,10 @@ config HAVE_INTEL_TXT
def_bool y def_bool y
depends on INTEL_IOMMU && ACPI depends on INTEL_IOMMU && ACPI
config X86_INTEL_MPX
def_bool y
depends on CPU_SUP_INTEL
config X86_32_SMP config X86_32_SMP
def_bool y def_bool y
depends on X86_32 && SMP depends on X86_32 && SMP
......
#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 */
...@@ -30,3 +30,5 @@ obj-$(CONFIG_ACPI_NUMA) += srat.o ...@@ -30,3 +30,5 @@ obj-$(CONFIG_ACPI_NUMA) += srat.o
obj-$(CONFIG_NUMA_EMU) += numa_emulation.o obj-$(CONFIG_NUMA_EMU) += numa_emulation.o
obj-$(CONFIG_MEMTEST) += memtest.o obj-$(CONFIG_MEMTEST) += memtest.o
obj-$(CONFIG_X86_INTEL_MPX) += mpx.o
/*
* 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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