arch/x86/mm/mpx.c

   1 /*
   2  * mpx.c - Memory Protection eXtensions
   3  *
   4  * Copyright (c) 2014, Intel Corporation.
   5  * Qiaowei Ren <qiaowei.ren@intel.com>
   6  * Dave Hansen <dave.hansen@intel.com>
   7  */
   8 #include <linux/kernel.h>
   9 #include <linux/syscalls.h>
  10 #include <linux/sched/sysctl.h>
  11
  12 #include <asm/mman.h>
  13 #include <asm/mpx.h>
  14
  15 static const char *mpx_mapping_name(struct vm_area_struct *vma)
  16 {
  17         return "[mpx]";
  18 }
  19
  20 static struct vm_operations_struct mpx_vma_ops = {
  21         .name = mpx_mapping_name,
  22 };
  23
  24 /*
  25  * This is really a simplified "vm_mmap". it only handles MPX
  26  * bounds tables (the bounds directory is user-allocated).
  27  *
  28  * Later on, we use the vma->vm_ops to uniquely identify these
  29  * VMAs.
  30  */
  31 static unsigned long mpx_mmap(unsigned long len)
  32 {
  33         unsigned long ret;
  34         unsigned long addr, pgoff;
  35         struct mm_struct *mm = current->mm;
  36         vm_flags_t vm_flags;
  37         struct vm_area_struct *vma;
  38
  39         /* Only bounds table and bounds directory can be allocated here */
  40         if (len != MPX_BD_SIZE_BYTES && len != MPX_BT_SIZE_BYTES)
  41                 return -EINVAL;
  42
  43         down_write(&mm->mmap_sem);
  44
  45         /* Too many mappings? */
  46         if (mm->map_count > sysctl_max_map_count) {
  47                 ret = -ENOMEM;
  48                 goto out;
  49         }
  50
  51         /* Obtain the address to map to. we verify (or select) it and ensure
  52          * that it represents a valid section of the address space.
  53          */
  54         addr = get_unmapped_area(NULL, 0, len, 0, MAP_ANONYMOUS | MAP_PRIVATE);
  55         if (addr & ~PAGE_MASK) {
  56                 ret = addr;
  57                 goto out;
  58         }
  59
  60         vm_flags = VM_READ | VM_WRITE | VM_MPX |
  61                         mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
  62
  63         /* Set pgoff according to addr for anon_vma */
  64         pgoff = addr >> PAGE_SHIFT;
  65
  66         ret = mmap_region(NULL, addr, len, vm_flags, pgoff);
  67         if (IS_ERR_VALUE(ret))
  68                 goto out;
  69
  70         vma = find_vma(mm, ret);
  71         if (!vma) {
  72                 ret = -ENOMEM;
  73                 goto out;
  74         }
  75         vma->vm_ops = &mpx_vma_ops;
  76
  77         if (vm_flags & VM_LOCKED) {
  78                 up_write(&mm->mmap_sem);
  79                 mm_populate(ret, len);
  80                 return ret;
  81         }
  82
  83 out:
  84         up_write(&mm->mmap_sem);
  85         return ret;
  86 }