mm/mlock.c

   1 /*
   2  *      linux/mm/mlock.c
   3  *
   4  *  (C) Copyright 1995 Linus Torvalds
   5  *  (C) Copyright 2002 Christoph Hellwig
   6  */
   7
   8 #include <linux/mman.h>
   9 #include <linux/mm.h>
  10
  11
  12 static int mlock_fixup(struct vm_area_struct * vma,
  13         unsigned long start, unsigned long end, unsigned int newflags)
  14 {
  15         struct mm_struct * mm = vma->vm_mm;
  16         int pages;
  17         int ret = 0;
  18
  19         if (newflags == vma->vm_flags)
  20                 goto out;
  21
  22         if (start != vma->vm_start) {
  23                 if (split_vma(mm, vma, start, 1)) {
  24                         ret = -EAGAIN;
  25                         goto out;
  26                 }
  27         }
  28
  29         if (end != vma->vm_end) {
  30                 if (split_vma(mm, vma, end, 0)) {
  31                         ret = -EAGAIN;
  32                         goto out;
  33                 }
  34         }
  35
  36         /*
  37          * vm_flags is protected by the mmap_sem held in write mode.
  38          * It's okay if try_to_unmap_one unmaps a page just after we
  39          * set VM_LOCKED, make_pages_present below will bring it back.
  40          */
  41         vma->vm_flags = newflags;
  42
  43         /*
  44          * Keep track of amount of locked VM.
  45          */
  46         pages = (end - start) >> PAGE_SHIFT;
  47         if (newflags & VM_LOCKED) {
  48                 pages = -pages;
  49                 ret = make_pages_present(start, end);
  50         }
  51
  52         vma->vm_mm->locked_vm -= pages;
  53 out:
  54         return ret;
  55 }
  56
  57 static int do_mlock(unsigned long start, size_t len, int on)
  58 {
  59         unsigned long nstart, end, tmp;
  60         struct vm_area_struct * vma, * next;
  61         int error;
  62
  63         if (on && !capable(CAP_IPC_LOCK))
  64                 return -EPERM;
  65         len = PAGE_ALIGN(len);
  66         end = start + len;
  67         if (end < start)
  68                 return -EINVAL;
  69         if (end == start)
  70                 return 0;
  71         vma = find_vma(current->mm, start);
  72         if (!vma || vma->vm_start > start)
  73                 return -ENOMEM;
  74
  75         for (nstart = start ; ; ) {
  76                 unsigned int newflags;
  77
  78                 /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
  79
  80                 newflags = vma->vm_flags | VM_LOCKED;
  81                 if (!on)
  82                         newflags &= ~VM_LOCKED;
  83
  84                 if (vma->vm_end >= end) {
  85                         error = mlock_fixup(vma, nstart, end, newflags);
  86                         break;
  87                 }
  88
  89                 tmp = vma->vm_end;
  90                 next = vma->vm_next;
  91                 error = mlock_fixup(vma, nstart, tmp, newflags);
  92                 if (error)
  93                         break;
  94                 nstart = tmp;
  95                 vma = next;
  96                 if (!vma || vma->vm_start != nstart) {
  97                         error = -ENOMEM;
  98                         break;
  99                 }
 100         }
 101         return error;
 102 }
 103
 104 asmlinkage long sys_mlock(unsigned long start, size_t len)
 105 {
 106         unsigned long locked;
 107         unsigned long lock_limit;
 108         int error = -ENOMEM;
 109
 110         down_write(&current->mm->mmap_sem);
 111         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
 112         start &= PAGE_MASK;
 113
 114         locked = len >> PAGE_SHIFT;
 115         locked += current->mm->locked_vm;
 116
 117         lock_limit = current->rlim[RLIMIT_MEMLOCK].rlim_cur;
 118         lock_limit >>= PAGE_SHIFT;
 119
 120         /* check against resource limits */
 121         if (locked <= lock_limit)
 122                 error = do_mlock(start, len, 1);
 123         up_write(&current->mm->mmap_sem);
 124         return error;
 125 }
 126
 127 asmlinkage long sys_munlock(unsigned long start, size_t len)
 128 {
 129         int ret;
 130
 131         down_write(&current->mm->mmap_sem);
 132         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
 133         start &= PAGE_MASK;
 134         ret = do_mlock(start, len, 0);
 135         up_write(&current->mm->mmap_sem);
 136         return ret;
 137 }
 138
 139 static int do_mlockall(int flags)
 140 {
 141         int error;
 142         unsigned int def_flags;
 143         struct vm_area_struct * vma;
 144
 145         if (!capable(CAP_IPC_LOCK))
 146                 return -EPERM;
 147
 148         def_flags = 0;
 149         if (flags & MCL_FUTURE)
 150                 def_flags = VM_LOCKED;
 151         current->mm->def_flags = def_flags;
 152
 153         error = 0;
 154         for (vma = current->mm->mmap; vma ; vma = vma->vm_next) {
 155                 unsigned int newflags;
 156
 157                 newflags = vma->vm_flags | VM_LOCKED;
 158                 if (!(flags & MCL_CURRENT))
 159                         newflags &= ~VM_LOCKED;
 160
 161                 /* Ignore errors */
 162                 mlock_fixup(vma, vma->vm_start, vma->vm_end, newflags);
 163         }
 164         return error;
 165 }
 166
 167 asmlinkage long sys_mlockall(int flags)
 168 {
 169         unsigned long lock_limit;
 170         int ret = -EINVAL;
 171
 172         down_write(&current->mm->mmap_sem);
 173         if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
 174                 goto out;
 175
 176         lock_limit = current->rlim[RLIMIT_MEMLOCK].rlim_cur;
 177         lock_limit >>= PAGE_SHIFT;
 178
 179         ret = -ENOMEM;
 180         if (current->mm->total_vm <= lock_limit)
 181                 ret = do_mlockall(flags);
 182 out:
 183         up_write(&current->mm->mmap_sem);
 184         return ret;
 185 }
 186
 187 asmlinkage long sys_munlockall(void)
 188 {
 189         int ret;
 190
 191         down_write(&current->mm->mmap_sem);
 192         ret = do_mlockall(0);
 193         up_write(&current->mm->mmap_sem);
 194         return ret;
 195 }