text: /*
   *	linux/mm/mlock.c
   *
   *  (C) Copyright 1995 Linus Torvalds
   */
  #include <linux/slab.h>
  #include <linux/shm.h>
  #include <linux/mman.h>
  #include <linux/smp_lock.h>
  #include <linux/pagemap.h>
  
  #include <asm/uaccess.h>
  #include <asm/pgtable.h>
  
  static inline int mlock_fixup_all(struct vm_area_struct * vma, int newflags)
  {
  	spin_lock(&vma->vm_mm->page_table_lock);
  	vma->vm_flags = newflags;
  	spin_unlock(&vma->vm_mm->page_table_lock);
  	return 0;
  }
  
  static inline int mlock_fixup_start(struct vm_area_struct * vma,
  	unsigned long end, int newflags)
  {
  	struct vm_area_struct * n;
  
  	n = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
  	if (!n)
  		return -EAGAIN;
  	*n = *vma;
  	n->vm_end = end;
  	n->vm_flags = newflags;
  	n->vm_raend = 0;
  	if (n->vm_file)
  		get_file(n->vm_file);
  	if (n->vm_ops && n->vm_ops->open)
  		n->vm_ops->open(n);
  	vma->vm_pgoff += (end - vma->vm_start) >> PAGE_SHIFT;
  	lock_vma_mappings(vma);
  	spin_lock(&vma->vm_mm->page_table_lock);
  	vma->vm_start = end;
  	__insert_vm_struct(current->mm, n);
  	spin_unlock(&vma->vm_mm->page_table_lock);
  	unlock_vma_mappings(vma);
  	return 0;
  }
  
  static inline int mlock_fixup_end(struct vm_area_struct * vma,
  	unsigned long start, int newflags)
  {
  	struct vm_area_struct * n;
  
  	n = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
  	if (!n)
  		return -EAGAIN;
  	*n = *vma;
  	n->vm_start = start;
  	n->vm_pgoff += (n->vm_start - vma->vm_start) >> PAGE_SHIFT;
  	n->vm_flags = newflags;
  	n->vm_raend = 0;
  	if (n->vm_file)
  		get_file(n->vm_file);
  	if (n->vm_ops && n->vm_ops->open)
  		n->vm_ops->open(n);
  	lock_vma_mappings(vma);
  	spin_lock(&vma->vm_mm->page_table_lock);
  	vma->vm_end = start;
  	__insert_vm_struct(current->mm, n);
  	spin_unlock(&vma->vm_mm->page_table_lock);
  	unlock_vma_mappings(vma);
  	return 0;
  }
  
  static inline int mlock_fixup_middle(struct vm_area_struct * vma,
  	unsigned long start, unsigned long end, int newflags)
  {
  	struct vm_area_struct * left, * right;
  
  	left = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
  	if (!left)
  		return -EAGAIN;
  	right = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
  	if (!right) {
  		kmem_cache_free(vm_area_cachep, left);
  		return -EAGAIN;
  	}
  	*left = *vma;
  	*right = *vma;
  	left->vm_end = start;
  	right->vm_start = end;
  	right->vm_pgoff += (right->vm_start - left->vm_start) >> PAGE_SHIFT;
  	vma->vm_flags = newflags;
  	left->vm_raend = 0;
  	right->vm_raend = 0;
  	if (vma->vm_file)
  		atomic_add(2, &vma->vm_file->f_count);
  
  	if (vma->vm_ops && vma->vm_ops->open) {
  		vma->vm_ops->open(left);
  		vma->vm_ops->open(right);
  	}
  	vma->vm_raend = 0;
  	vma->vm_pgoff += (start - vma->vm_start) >> PAGE_SHIFT;
  	lock_vma_mappings(vma);
  	spin_lock(&vma->vm_mm->page_table_lock);
  	vma->vm_start = start;
  	vma->vm_end = end;
  	vma->vm_flags = newflags;
  	__insert_vm_struct(current->mm, left);
  	__insert_vm_struct(current->mm, right);
  	spin_unlock(&vma->vm_mm->page_table_lock);
  	unlock_vma_mappings(vma);
  	return 0;
  }
  
  static int mlock_fixup(struct vm_area_struct * vma, 
  	unsigned long start, unsigned long end, unsigned int newflags)
  {
  	int pages, retval;
  
  	if (newflags == vma->vm_flags)
  		return 0;
  
  	if (start == vma->vm_start) {
  		if (end == vma->vm_end)
  			retval = mlock_fixup_all(vma, newflags);
  		else
  			retval = mlock_fixup_start(vma, end, newflags);
  	} else {
  		if (end == vma->vm_end)
  			retval = mlock_fixup_end(vma, start, newflags);
  		else
  			retval = mlock_fixup_middle(vma, start, end, newflags);
  	}
  	if (!retval) {
  		/* keep track of amount of locked VM */
  		pages = (end - start) >> PAGE_SHIFT;
  		if (newflags & VM_LOCKED) {
  			pages = -pages;
  			make_pages_present(start, end);
  		}
  		vma->vm_mm->locked_vm -= pages;
  	}
  	return retval;
  }
  
  static int do_mlock(unsigned long start, size_t len, int on)
  {
  	unsigned long nstart, end, tmp;
  	struct vm_area_struct * vma, * next;
  	int error;
  
  	if (on && !capable(CAP_IPC_LOCK))
  		return -EPERM;
  	len = PAGE_ALIGN(len);
  	end = start + len;
  	if (end < start)
  		return -EINVAL;
  	if (end == start)
  		return 0;
  	vma = find_vma(current->mm, start);
  	if (!vma || vma->vm_start > start)
  		return -ENOMEM;
  
  	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;
  
  		if (vma->vm_end >= end) {
  			error = mlock_fixup(vma, nstart, end, newflags);
  			break;
  		}
  
  		tmp = vma->vm_end;
  		next = vma->vm_next;
  		error = mlock_fixup(vma, nstart, tmp, newflags);
  		if (error)
  			break;
  		nstart = tmp;
  		vma = 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;
  
  	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->rlim[RLIMIT_MEMLOCK].rlim_cur;
  	lock_limit >>= PAGE_SHIFT;
  
  	/* check against resource limits */
  	if (locked > lock_limit)
  		goto out;
  
  	/* we may lock at most half of physical memory... */
  	/* (this check is pretty bogus, but doesn't hurt) */
  	if (locked > num_physpages/2)
  		goto out;
  
  	error = do_mlock(start, len, 1);
  out:
  	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)
  {
  	int error;
  	unsigned int def_flags;
  	struct vm_area_struct * vma;
  
  	if (!capable(CAP_IPC_LOCK))
  		return -EPERM;
  
  	def_flags = 0;
  	if (flags & MCL_FUTURE)
  		def_flags = VM_LOCKED;
  	current->mm->def_flags = def_flags;
  
  	error = 0;
  	for (vma = current->mm->mmap; vma ; vma = vma->vm_next) {
  		unsigned int newflags;
  
  		newflags = vma->vm_flags | VM_LOCKED;
  		if (!(flags & MCL_CURRENT))
  			newflags &= ~VM_LOCKED;
  		error = mlock_fixup(vma, vma->vm_start, vma->vm_end, newflags);
  		if (error)
  			break;
  	}
  	return error;
  }
  
  asmlinkage long sys_mlockall(int flags)
  {
  	unsigned long lock_limit;
  	int ret = -EINVAL;
  
  	down_write(&current->mm->mmap_sem);
  	if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
  		goto out;
  
  	lock_limit = current->rlim[RLIMIT_MEMLOCK].rlim_cur;
  	lock_limit >>= PAGE_SHIFT;
  
  	ret = -ENOMEM;
  	if (current->mm->total_vm > lock_limit)
  		goto out;
  
  	/* we may lock at most half of physical memory... */
  	/* (this check is pretty bogus, but doesn't hurt) */
  	if (current->mm->total_vm > num_physpages/2)
  		goto out;
  
  	ret = do_mlockall(flags);
  out:
  	up_write(&current->mm->mmap_sem);
  	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;
  }
  