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         return ret;
  82 }
  83
  84 static int do_mlock(unsigned long start, size_t len, int on)
  85 {
  86         unsigned long nstart, end, tmp;
  87         struct vm_area_struct * vma, * prev;
  88         int error;
  89
  90         len = PAGE_ALIGN(len);
  91         end = start + len;
  92         if (end < start)
  93                 return -EINVAL;
  94         if (end == start)
  95                 return 0;
  96         vma = find_vma_prev(current->mm, start, &prev);
  97         if (!vma || vma->vm_start > start)
  98                 return -ENOMEM;
  99
 100         if (start > vma->vm_start)
 101                 prev = vma;
 102
 103         for (nstart = start ; ; ) {
 104                 unsigned int newflags;
 105
 106                 /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
 107
 108                 newflags = vma->vm_flags | VM_LOCKED;
 109                 if (!on)
 110                         newflags &= ~VM_LOCKED;
 111
 112                 tmp = vma->vm_end;
 113                 if (tmp > end)
 114                         tmp = end;
 115                 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
 116                 if (error)
 117                         break;
 118                 nstart = tmp;
 119                 if (nstart < prev->vm_end)
 120                         nstart = prev->vm_end;
 121                 if (nstart >= end)
 122                         break;
 123
 124                 vma = prev->vm_next;
 125                 if (!vma || vma->vm_start != nstart) {
 126                         error = -ENOMEM;
 127                         break;
 128                 }
 129         }
 130         return error;
 131 }
 132
 133 asmlinkage long sys_mlock(unsigned long start, size_t len)
 134 {
 135         unsigned long locked;
 136         unsigned long lock_limit;
 137         int error = -ENOMEM;
 138
 139         if (!can_do_mlock())
 140                 return -EPERM;
 141
 142         down_write(&current->mm->mmap_sem);
 143         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
 144         start &= PAGE_MASK;
 145
 146         locked = len >> PAGE_SHIFT;
 147         locked += current->mm->locked_vm;
 148
 149         lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 150         lock_limit >>= PAGE_SHIFT;
 151
 152         /* check against resource limits */
 153         if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
 154                 error = do_mlock(start, len, 1);
 155         up_write(&current->mm->mmap_sem);
 156         return error;
 157 }
 158
 159 asmlinkage long sys_munlock(unsigned long start, size_t len)
 160 {
 161         int ret;
 162
 163         down_write(&current->mm->mmap_sem);
 164         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
 165         start &= PAGE_MASK;
 166         ret = do_mlock(start, len, 0);
 167         up_write(&current->mm->mmap_sem);
 168         return ret;
 169 }
 170
 171 static int do_mlockall(int flags)
 172 {
 173         struct vm_area_struct * vma, * prev = NULL;
 174         unsigned int def_flags = 0;
 175
 176         if (flags & MCL_FUTURE)
 177                 def_flags = VM_LOCKED;
 178         current->mm->def_flags = def_flags;
 179         if (flags == MCL_FUTURE)
 180                 goto out;
 181
 182         for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
 183                 unsigned int newflags;
 184
 185                 newflags = vma->vm_flags | VM_LOCKED;
 186                 if (!(flags & MCL_CURRENT))
 187                         newflags &= ~VM_LOCKED;
 188
 189                 /* Ignore errors */
 190                 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
 191         }
 192 out:
 193         return 0;
 194 }
 195
 196 asmlinkage long sys_mlockall(int flags)
 197 {
 198         unsigned long lock_limit;
 199         int ret = -EINVAL;
 200
 201         if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
 202                 goto out;
 203
 204         ret = -EPERM;
 205         if (!can_do_mlock())
 206                 goto out;
 207
 208         down_write(&current->mm->mmap_sem);
 209
 210         lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 211         lock_limit >>= PAGE_SHIFT;
 212
 213         ret = -ENOMEM;
 214         if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
 215             capable(CAP_IPC_LOCK))
 216                 ret = do_mlockall(flags);
 217         up_write(&current->mm->mmap_sem);
 218 out:
 219         return ret;
 220 }
 221
 222 asmlinkage long sys_munlockall(void)
 223 {
 224         int ret;
 225
 226         down_write(&current->mm->mmap_sem);
 227         ret = do_mlockall(0);
 228         up_write(&current->mm->mmap_sem);
 229         return ret;
 230 }
 231
 232 /*
 233  * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
 234  * shm segments) get accounted against the user_struct instead.
 235  */
 236 static DEFINE_SPINLOCK(shmlock_user_lock);
 237
 238 int user_shm_lock(size_t size, struct user_struct *user)
 239 {
 240         unsigned long lock_limit, locked;
 241         int allowed = 0;
 242
 243         locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 244         lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 245         if (lock_limit == RLIM_INFINITY)
 246                 allowed = 1;
 247         lock_limit >>= PAGE_SHIFT;
 248         spin_lock(&shmlock_user_lock);
 249         if (!allowed &&
 250             locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
 251                 goto out;
 252         get_uid(user);
 253         user->locked_shm += locked;
 254         allowed = 1;
 255 out:
 256         spin_unlock(&shmlock_user_lock);
 257         return allowed;
 258 }
 259
 260 void user_shm_unlock(size_t size, struct user_struct *user)
 261 {
 262         spin_lock(&shmlock_user_lock);
 263         user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 264         spin_unlock(&shmlock_user_lock);
 265         free_uid(user);
 266 }