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 #include <linux/sched.h>
  14 #include <linux/module.h>
  15
  16 int can_do_mlock(void)
  17 {
  18         if (capable(CAP_IPC_LOCK))
  19                 return 1;
  20         if (current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur != 0)
  21                 return 1;
  22         return 0;
  23 }
  24 EXPORT_SYMBOL(can_do_mlock);
  25
  26 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
  27         unsigned long start, unsigned long end, unsigned int newflags)
  28 {
  29         struct mm_struct * mm = vma->vm_mm;
  30         pgoff_t pgoff;
  31         int pages;
  32         int ret = 0;
  33
  34         if (newflags == vma->vm_flags) {
  35                 *prev = vma;
  36                 goto out;
  37         }
  38
  39         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
  40         *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
  41                           vma->vm_file, pgoff, vma_policy(vma));
  42         if (*prev) {
  43                 vma = *prev;
  44                 goto success;
  45         }
  46
  47         *prev = vma;
  48
  49         if (start != vma->vm_start) {
  50                 ret = split_vma(mm, vma, start, 1);
  51                 if (ret)
  52                         goto out;
  53         }
  54
  55         if (end != vma->vm_end) {
  56                 ret = split_vma(mm, vma, end, 0);
  57                 if (ret)
  58                         goto out;
  59         }
  60
  61 success:
  62         /*
  63          * vm_flags is protected by the mmap_sem held in write mode.
  64          * It's okay if try_to_unmap_one unmaps a page just after we
  65          * set VM_LOCKED, make_pages_present below will bring it back.
  66          */
  67         vma->vm_flags = newflags;
  68
  69         /*
  70          * Keep track of amount of locked VM.
  71          */
  72         pages = (end - start) >> PAGE_SHIFT;
  73         if (newflags & VM_LOCKED) {
  74                 pages = -pages;
  75                 if (!(newflags & VM_IO))
  76                         ret = make_pages_present(start, end);
  77         }
  78
  79         mm->locked_vm -= pages;
  80 out:
  81         if (ret == -ENOMEM)
  82                 ret = -EAGAIN;
  83         return ret;
  84 }
  85
  86 static int do_mlock(unsigned long start, size_t len, int on)
  87 {
  88         unsigned long nstart, end, tmp;
  89         struct vm_area_struct * vma, * prev;
  90         int error;
  91
  92         len = PAGE_ALIGN(len);
  93         end = start + len;
  94         if (end < start)
  95                 return -EINVAL;
  96         if (end == start)
  97                 return 0;
  98         vma = find_vma_prev(current->mm, start, &prev);
  99         if (!vma || vma->vm_start > start)
 100                 return -ENOMEM;
 101
 102         if (start > vma->vm_start)
 103                 prev = vma;
 104
 105         for (nstart = start ; ; ) {
 106                 unsigned int newflags;
 107
 108                 /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
 109
 110                 newflags = vma->vm_flags | VM_LOCKED;
 111                 if (!on)
 112                         newflags &= ~VM_LOCKED;
 113
 114                 tmp = vma->vm_end;
 115                 if (tmp > end)
 116                         tmp = end;
 117                 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
 118                 if (error)
 119                         break;
 120                 nstart = tmp;
 121                 if (nstart < prev->vm_end)
 122                         nstart = prev->vm_end;
 123                 if (nstart >= end)
 124                         break;
 125
 126                 vma = prev->vm_next;
 127                 if (!vma || vma->vm_start != nstart) {
 128                         error = -ENOMEM;
 129                         break;
 130                 }
 131         }
 132         return error;
 133 }
 134
 135 asmlinkage long sys_mlock(unsigned long start, size_t len)
 136 {
 137         unsigned long locked;
 138         unsigned long lock_limit;
 139         int error = -ENOMEM;
 140
 141         if (!can_do_mlock())
 142                 return -EPERM;
 143
 144         down_write(&current->mm->mmap_sem);
 145         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
 146         start &= PAGE_MASK;
 147
 148         locked = len >> PAGE_SHIFT;
 149         locked += current->mm->locked_vm;
 150
 151         lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 152         lock_limit >>= PAGE_SHIFT;
 153
 154         /* check against resource limits */
 155         if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
 156                 error = do_mlock(start, len, 1);
 157         up_write(&current->mm->mmap_sem);
 158         return error;
 159 }
 160
 161 asmlinkage long sys_munlock(unsigned long start, size_t len)
 162 {
 163         int ret;
 164
 165         down_write(&current->mm->mmap_sem);
 166         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
 167         start &= PAGE_MASK;
 168         ret = do_mlock(start, len, 0);
 169         up_write(&current->mm->mmap_sem);
 170         return ret;
 171 }
 172
 173 static int do_mlockall(int flags)
 174 {
 175         struct vm_area_struct * vma, * prev = NULL;
 176         unsigned int def_flags = 0;
 177
 178         if (flags & MCL_FUTURE)
 179                 def_flags = VM_LOCKED;
 180         current->mm->def_flags = def_flags;
 181         if (flags == MCL_FUTURE)
 182                 goto out;
 183
 184         for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
 185                 unsigned int newflags;
 186
 187                 newflags = vma->vm_flags | VM_LOCKED;
 188                 if (!(flags & MCL_CURRENT))
 189                         newflags &= ~VM_LOCKED;
 190
 191                 /* Ignore errors */
 192                 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
 193         }
 194 out:
 195         return 0;
 196 }
 197
 198 asmlinkage long sys_mlockall(int flags)
 199 {
 200         unsigned long lock_limit;
 201         int ret = -EINVAL;
 202
 203         if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
 204                 goto out;
 205
 206         ret = -EPERM;
 207         if (!can_do_mlock())
 208                 goto out;
 209
 210         down_write(&current->mm->mmap_sem);
 211
 212         lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 213         lock_limit >>= PAGE_SHIFT;
 214
 215         ret = -ENOMEM;
 216         if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
 217             capable(CAP_IPC_LOCK))
 218                 ret = do_mlockall(flags);
 219         up_write(&current->mm->mmap_sem);
 220 out:
 221         return ret;
 222 }
 223
 224 asmlinkage long sys_munlockall(void)
 225 {
 226         int ret;
 227
 228         down_write(&current->mm->mmap_sem);
 229         ret = do_mlockall(0);
 230         up_write(&current->mm->mmap_sem);
 231         return ret;
 232 }
 233
 234 /*
 235  * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
 236  * shm segments) get accounted against the user_struct instead.
 237  */
 238 static DEFINE_SPINLOCK(shmlock_user_lock);
 239
 240 int user_shm_lock(size_t size, struct user_struct *user)
 241 {
 242         unsigned long lock_limit, locked;
 243         int allowed = 0;
 244
 245         locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 246         lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 247         lock_limit >>= PAGE_SHIFT;
 248         spin_lock(&shmlock_user_lock);
 249         if (locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
 250                 goto out;
 251         get_uid(user);
 252         user->locked_shm += locked;
 253         allowed = 1;
 254 out:
 255         spin_unlock(&shmlock_user_lock);
 256         return allowed;
 257 }
 258
 259 void user_shm_unlock(size_t size, struct user_struct *user)
 260 {
 261         spin_lock(&shmlock_user_lock);
 262         user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 263         spin_unlock(&shmlock_user_lock);
 264         free_uid(user);
 265 }