Linux Cross Reference
Linux-2.6.17/mm/mlock.c

   /*
    *      linux/mm/mlock.c
    *
    *  (C) Copyright 1995 Linus Torvalds
    *  (C) Copyright 2002 Christoph Hellwig
    */
   
   #include <linux/capability.h>
   #include <linux/mman.h>
  #include <linux/mm.h>
  #include <linux/mempolicy.h>
  #include <linux/syscalls.h>
  
  
  static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
          unsigned long start, unsigned long end, unsigned int newflags)
  {
          struct mm_struct * mm = vma->vm_mm;
          pgoff_t pgoff;
          int pages;
          int ret = 0;
  
          if (newflags == vma->vm_flags) {
                  *prev = vma;
                  goto out;
          }
  
          pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
          *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
                            vma->vm_file, pgoff, vma_policy(vma));
          if (*prev) {
                  vma = *prev;
                  goto success;
          }
  
          *prev = vma;
  
          if (start != vma->vm_start) {
                  ret = split_vma(mm, vma, start, 1);
                  if (ret)
                          goto out;
          }
  
          if (end != vma->vm_end) {
                  ret = split_vma(mm, vma, end, 0);
                  if (ret)
                          goto out;
          }
  
  success:
          /*
           * vm_flags is protected by the mmap_sem held in write mode.
           * It's okay if try_to_unmap_one unmaps a page just after we
           * set VM_LOCKED, make_pages_present below will bring it back.
           */
          vma->vm_flags = newflags;
  
          /*
           * Keep track of amount of locked VM.
           */
          pages = (end - start) >> PAGE_SHIFT;
          if (newflags & VM_LOCKED) {
                  pages = -pages;
                  if (!(newflags & VM_IO))
                          ret = make_pages_present(start, end);
          }
  
          vma->vm_mm->locked_vm -= pages;
  out:
          if (ret == -ENOMEM)
                  ret = -EAGAIN;
          return ret;
  }
  
  static int do_mlock(unsigned long start, size_t len, int on)
  {
          unsigned long nstart, end, tmp;
          struct vm_area_struct * vma, * prev;
          int error;
  
          len = PAGE_ALIGN(len);
          end = start + len;
          if (end < start)
                  return -EINVAL;
          if (end == start)
                  return 0;
          vma = find_vma_prev(current->mm, start, &prev);
          if (!vma || vma->vm_start > start)
                  return -ENOMEM;
  
          if (start > vma->vm_start)
                  prev = vma;
  
          for (nstart = start ; ; ) {
                  unsigned int newflags;
  
                  /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
  
                  newflags = vma->vm_flags | VM_LOCKED;
                 if (!on)
                         newflags &= ~VM_LOCKED;
 
                 tmp = vma->vm_end;
                 if (tmp > end)
                         tmp = end;
                 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
                 if (error)
                         break;
                 nstart = tmp;
                 if (nstart < prev->vm_end)
                         nstart = prev->vm_end;
                 if (nstart >= end)
                         break;
 
                 vma = prev->vm_next;
                 if (!vma || vma->vm_start != nstart) {
                         error = -ENOMEM;
                         break;
                 }
         }
         return error;
 }
 
 asmlinkage long sys_mlock(unsigned long start, size_t len)
 {
         unsigned long locked;
         unsigned long lock_limit;
         int error = -ENOMEM;
 
         if (!can_do_mlock())
                 return -EPERM;
 
         down_write(&current->mm->mmap_sem);
         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
         start &= PAGE_MASK;
 
         locked = len >> PAGE_SHIFT;
         locked += current->mm->locked_vm;
 
         lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
         lock_limit >>= PAGE_SHIFT;
 
         /* check against resource limits */
         if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
                 error = do_mlock(start, len, 1);
         up_write(&current->mm->mmap_sem);
         return error;
 }
 
 asmlinkage long sys_munlock(unsigned long start, size_t len)
 {
         int ret;
 
         down_write(&current->mm->mmap_sem);
         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
         start &= PAGE_MASK;
         ret = do_mlock(start, len, 0);
         up_write(&current->mm->mmap_sem);
         return ret;
 }
 
 static int do_mlockall(int flags)
 {
         struct vm_area_struct * vma, * prev = NULL;
         unsigned int def_flags = 0;
 
         if (flags & MCL_FUTURE)
                 def_flags = VM_LOCKED;
         current->mm->def_flags = def_flags;
         if (flags == MCL_FUTURE)
                 goto out;
 
         for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
                 unsigned int newflags;
 
                 newflags = vma->vm_flags | VM_LOCKED;
                 if (!(flags & MCL_CURRENT))
                         newflags &= ~VM_LOCKED;
 
                 /* Ignore errors */
                 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
         }
 out:
         return 0;
 }
 
 asmlinkage long sys_mlockall(int flags)
 {
         unsigned long lock_limit;
         int ret = -EINVAL;
 
         if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
                 goto out;
 
         ret = -EPERM;
         if (!can_do_mlock())
                 goto out;
 
         down_write(&current->mm->mmap_sem);
 
         lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
         lock_limit >>= PAGE_SHIFT;
 
         ret = -ENOMEM;
         if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
             capable(CAP_IPC_LOCK))
                 ret = do_mlockall(flags);
         up_write(&current->mm->mmap_sem);
 out:
         return ret;
 }
 
 asmlinkage long sys_munlockall(void)
 {
         int ret;
 
         down_write(&current->mm->mmap_sem);
         ret = do_mlockall(0);
         up_write(&current->mm->mmap_sem);
         return ret;
 }
 
 /*
  * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
  * shm segments) get accounted against the user_struct instead.
  */
 static DEFINE_SPINLOCK(shmlock_user_lock);
 
 int user_shm_lock(size_t size, struct user_struct *user)
 {
         unsigned long lock_limit, locked;
         int allowed = 0;
 
         locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
         lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
         lock_limit >>= PAGE_SHIFT;
         spin_lock(&shmlock_user_lock);
         if (locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
                 goto out;
         get_uid(user);
         user->locked_shm += locked;
         allowed = 1;
 out:
         spin_unlock(&shmlock_user_lock);
         return allowed;
 }
 
 void user_shm_unlock(size_t size, struct user_struct *user)
 {
         spin_lock(&shmlock_user_lock);
         user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
         spin_unlock(&shmlock_user_lock);
         free_uid(user);
 }