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/capability.h>
   9 #include <linux/mman.h>
  10 #include <linux/mm.h>
  11 #include <linux/mempolicy.h>
  12 #include <linux/syscalls.h>
  13
  14
  15 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
  16         unsigned long start, unsigned long end, unsigned int newflags)
  17 {
  18         struct mm_struct * mm = vma->vm_mm;
  19         pgoff_t pgoff;
  20         int pages;
  21         int ret = 0;
  22
  23         if (newflags == vma->vm_flags) {
  24                 *prev = vma;
  25                 goto out;
  26         }
  27
  28         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
  29         *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
  30                           vma->vm_file, pgoff, vma_policy(vma));
  31         if (*prev) {
  32                 vma = *prev;
  33                 goto success;
  34         }
  35
  36         *prev = vma;
  37
  38         if (start != vma->vm_start) {
  39                 ret = split_vma(mm, vma, start, 1);
  40                 if (ret)
  41                         goto out;
  42         }
  43
  44         if (end != vma->vm_end) {
  45                 ret = split_vma(mm, vma, end, 0);
  46                 if (ret)
  47                         goto out;
  48         }
  49
  50 success:
  51         /*
  52          * vm_flags is protected by the mmap_sem held in write mode.
  53          * It's okay if try_to_unmap_one unmaps a page just after we
  54          * set VM_LOCKED, make_pages_present below will bring it back.
  55          */
  56         vma->vm_flags = newflags;
  57
  58         /*
  59          * Keep track of amount of locked VM.
  60          */
  61         pages = (end - start) >> PAGE_SHIFT;
  62         if (newflags & VM_LOCKED) {
  63                 pages = -pages;
  64                 if (!(newflags & VM_IO))
  65                         ret = make_pages_present(start, end);
  66         }
  67
  68         vma->vm_mm->locked_vm -= pages;
  69 out:
  70         if (ret == -ENOMEM)
  71                 ret = -EAGAIN;
  72         return ret;
  73 }
  74
  75 static int do_mlock(unsigned long start, size_t len, int on)
  76 {
  77         unsigned long nstart, end, tmp;
  78         struct vm_area_struct * vma, * prev;
  79         int error;
  80
  81         len = PAGE_ALIGN(len);
  82         end = start + len;
  83         if (end < start)
  84                 return -EINVAL;
  85         if (end == start)
  86                 return 0;
  87         vma = find_vma_prev(current->mm, start, &prev);
  88         if (!vma || vma->vm_start > start)
  89                 return -ENOMEM;
  90
  91         if (start > vma->vm_start)
  92                 prev = vma;
  93
  94         for (nstart = start ; ; ) {
  95                 unsigned int newflags;
  96
  97                 /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
  98
  99                 newflags = vma->vm_flags | VM_LOCKED;
 100                 if (!on)
 101                         newflags &= ~VM_LOCKED;
 102
 103                 tmp = vma->vm_end;
 104                 if (tmp > end)
 105                         tmp = end;
 106                 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
 107                 if (error)
 108                         break;
 109                 nstart = tmp;
 110                 if (nstart < prev->vm_end)
 111                         nstart = prev->vm_end;
 112                 if (nstart >= end)
 113                         break;
 114
 115                 vma = prev->vm_next;
 116                 if (!vma || vma->vm_start != nstart) {
 117                         error = -ENOMEM;
 118                         break;
 119                 }
 120         }
 121         return error;
 122 }
 123
 124 asmlinkage long sys_mlock(unsigned long start, size_t len)
 125 {
 126         unsigned long locked;
 127         unsigned long lock_limit;
 128         int error = -ENOMEM;
 129
 130         if (!can_do_mlock())
 131                 return -EPERM;
 132
 133         down_write(&current->mm->mmap_sem);
 134         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
 135         start &= PAGE_MASK;
 136
 137         locked = len >> PAGE_SHIFT;
 138         locked += current->mm->locked_vm;
 139
 140         lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 141         lock_limit >>= PAGE_SHIFT;
 142
 143         /* check against resource limits */
 144         if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
 145                 error = do_mlock(start, len, 1);
 146         up_write(&current->mm->mmap_sem);
 147         return error;
 148 }
 149
 150 asmlinkage long sys_munlock(unsigned long start, size_t len)
 151 {
 152         int ret;
 153
 154         down_write(&current->mm->mmap_sem);
 155         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
 156         start &= PAGE_MASK;
 157         ret = do_mlock(start, len, 0);
 158         up_write(&current->mm->mmap_sem);
 159         return ret;
 160 }
 161
 162 static int do_mlockall(int flags)
 163 {
 164         struct vm_area_struct * vma, * prev = NULL;
 165         unsigned int def_flags = 0;
 166
 167         if (flags & MCL_FUTURE)
 168                 def_flags = VM_LOCKED;
 169         current->mm->def_flags = def_flags;
 170         if (flags == MCL_FUTURE)
 171                 goto out;
 172
 173         for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
 174                 unsigned int newflags;
 175
 176                 newflags = vma->vm_flags | VM_LOCKED;
 177                 if (!(flags & MCL_CURRENT))
 178                         newflags &= ~VM_LOCKED;
 179
 180                 /* Ignore errors */
 181                 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
 182         }
 183 out:
 184         return 0;
 185 }
 186
 187 asmlinkage long sys_mlockall(int flags)
 188 {
 189         unsigned long lock_limit;
 190         int ret = -EINVAL;
 191
 192         if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
 193                 goto out;
 194
 195         ret = -EPERM;
 196         if (!can_do_mlock())
 197                 goto out;
 198
 199         down_write(&current->mm->mmap_sem);
 200
 201         lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 202         lock_limit >>= PAGE_SHIFT;
 203
 204         ret = -ENOMEM;
 205         if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
 206             capable(CAP_IPC_LOCK))
 207                 ret = do_mlockall(flags);
 208         up_write(&current->mm->mmap_sem);
 209 out:
 210         return ret;
 211 }
 212
 213 asmlinkage long sys_munlockall(void)
 214 {
 215         int ret;
 216
 217         down_write(&current->mm->mmap_sem);
 218         ret = do_mlockall(0);
 219         up_write(&current->mm->mmap_sem);
 220         return ret;
 221 }
 222
 223 /*
 224  * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
 225  * shm segments) get accounted against the user_struct instead.
 226  */
 227 static DEFINE_SPINLOCK(shmlock_user_lock);
 228
 229 int user_shm_lock(size_t size, struct user_struct *user)
 230 {
 231         unsigned long lock_limit, locked;
 232         int allowed = 0;
 233
 234         locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 235         lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 236         lock_limit >>= PAGE_SHIFT;
 237         spin_lock(&shmlock_user_lock);
 238         if (locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
 239                 goto out;
 240         get_uid(user);
 241         user->locked_shm += locked;
 242         allowed = 1;
 243 out:
 244         spin_unlock(&shmlock_user_lock);
 245         return allowed;
 246 }
 247
 248 void user_shm_unlock(size_t size, struct user_struct *user)
 249 {
 250         spin_lock(&shmlock_user_lock);
 251         user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 252         spin_unlock(&shmlock_user_lock);
 253         free_uid(user);
 254 }