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, error;
  17
  18         if (newflags == vma->vm_flags)
  19                 return 0;
  20
  21         if (start != vma->vm_start) {
  22                 error = split_vma(mm, vma, start, 1);
  23                 if (error)
  24                         return -EAGAIN;
  25         }
  26
  27         if (end != vma->vm_end) {
  28                 error = split_vma(mm, vma, end, 0);
  29                 if (error)
  30                         return -EAGAIN;
  31         }
  32
  33         spin_lock(&mm->page_table_lock);
  34         vma->vm_flags = newflags;
  35         spin_unlock(&mm->page_table_lock);
  36
  37         /*
  38          * Keep track of amount of locked VM.
  39          */
  40         pages = (end - start) >> PAGE_SHIFT;
  41         if (newflags & VM_LOCKED) {
  42                 pages = -pages;
  43                 make_pages_present(start, end);
  44         }
  45
  46         vma->vm_mm->locked_vm -= pages;
  47         return 0;
  48 }
  49
  50 static int do_mlock(unsigned long start, size_t len, int on)
  51 {
  52         unsigned long nstart, end, tmp;
  53         struct vm_area_struct * vma, * next;
  54         int error;
  55
  56         if (on && !capable(CAP_IPC_LOCK))
  57                 return -EPERM;
  58         len = PAGE_ALIGN(len);
  59         end = start + len;
  60         if (end < start)
  61                 return -EINVAL;
  62         if (end == start)
  63                 return 0;
  64         vma = find_vma(current->mm, start);
  65         if (!vma || vma->vm_start > start)
  66                 return -ENOMEM;
  67
  68         for (nstart = start ; ; ) {
  69                 unsigned int newflags;
  70
  71                 /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
  72
  73                 newflags = vma->vm_flags | VM_LOCKED;
  74                 if (!on)
  75                         newflags &= ~VM_LOCKED;
  76
  77                 if (vma->vm_end >= end) {
  78                         error = mlock_fixup(vma, nstart, end, newflags);
  79                         break;
  80                 }
  81
  82                 tmp = vma->vm_end;
  83                 next = vma->vm_next;
  84                 error = mlock_fixup(vma, nstart, tmp, newflags);
  85                 if (error)
  86                         break;
  87                 nstart = tmp;
  88                 vma = next;
  89                 if (!vma || vma->vm_start != nstart) {
  90                         error = -ENOMEM;
  91                         break;
  92                 }
  93         }
  94         return error;
  95 }
  96
  97 asmlinkage long sys_mlock(unsigned long start, size_t len)
  98 {
  99         unsigned long locked;
 100         unsigned long lock_limit;
 101         int error = -ENOMEM;
 102
 103         down_write(&current->mm->mmap_sem);
 104         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
 105         start &= PAGE_MASK;
 106
 107         locked = len >> PAGE_SHIFT;
 108         locked += current->mm->locked_vm;
 109
 110         lock_limit = current->rlim[RLIMIT_MEMLOCK].rlim_cur;
 111         lock_limit >>= PAGE_SHIFT;
 112
 113         /* check against resource limits */
 114         if (locked > lock_limit)
 115                 goto out;
 116
 117         /* we may lock at most half of physical memory... */
 118         /* (this check is pretty bogus, but doesn't hurt) */
 119         if (locked > num_physpages/2)
 120                 goto out;
 121
 122         error = do_mlock(start, len, 1);
 123 out:
 124         up_write(&current->mm->mmap_sem);
 125         return error;
 126 }
 127
 128 asmlinkage long sys_munlock(unsigned long start, size_t len)
 129 {
 130         int ret;
 131
 132         down_write(&current->mm->mmap_sem);
 133         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
 134         start &= PAGE_MASK;
 135         ret = do_mlock(start, len, 0);
 136         up_write(&current->mm->mmap_sem);
 137         return ret;
 138 }
 139
 140 static int do_mlockall(int flags)
 141 {
 142         int error;
 143         unsigned int def_flags;
 144         struct vm_area_struct * vma;
 145
 146         if (!capable(CAP_IPC_LOCK))
 147                 return -EPERM;
 148
 149         def_flags = 0;
 150         if (flags & MCL_FUTURE)
 151                 def_flags = VM_LOCKED;
 152         current->mm->def_flags = def_flags;
 153
 154         error = 0;
 155         for (vma = current->mm->mmap; vma ; vma = vma->vm_next) {
 156                 unsigned int newflags;
 157
 158                 newflags = vma->vm_flags | VM_LOCKED;
 159                 if (!(flags & MCL_CURRENT))
 160                         newflags &= ~VM_LOCKED;
 161                 error = mlock_fixup(vma, vma->vm_start, vma->vm_end, newflags);
 162                 if (error)
 163                         break;
 164         }
 165         return error;
 166 }
 167
 168 asmlinkage long sys_mlockall(int flags)
 169 {
 170         unsigned long lock_limit;
 171         int ret = -EINVAL;
 172
 173         down_write(&current->mm->mmap_sem);
 174         if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
 175                 goto out;
 176
 177         lock_limit = current->rlim[RLIMIT_MEMLOCK].rlim_cur;
 178         lock_limit >>= PAGE_SHIFT;
 179
 180         ret = -ENOMEM;
 181         if (current->mm->total_vm > lock_limit)
 182                 goto out;
 183
 184         /* we may lock at most half of physical memory... */
 185         /* (this check is pretty bogus, but doesn't hurt) */
 186         if (current->mm->total_vm > num_physpages/2)
 187                 goto out;
 188
 189         ret = do_mlockall(flags);
 190 out:
 191         up_write(&current->mm->mmap_sem);
 192         return ret;
 193 }
 194
 195 asmlinkage long sys_munlockall(void)
 196 {
 197         int ret;
 198
 199         down_write(&current->mm->mmap_sem);
 200         ret = do_mlockall(0);
 201         up_write(&current->mm->mmap_sem);
 202         return ret;
 203 }