text: /*
   *  linux/fs/readdir.c
   *
   *  Copyright (C) 1995  Linus Torvalds
   */
  
  #include <linux/stddef.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/time.h>
  #include <linux/mm.h>
  #include <linux/errno.h>
  #include <linux/stat.h>
  #include <linux/file.h>
  #include <linux/fs.h>
  #include <linux/dirent.h>
  #include <linux/security.h>
  #include <linux/syscalls.h>
  #include <linux/unistd.h>
  
  #include <asm/uaccess.h>
  
  int vfs_readdir(struct file *file, filldir_t filler, void *buf)
  {
  	struct inode *inode = file->f_path.dentry->d_inode;
  	int res = -ENOTDIR;
  	if (!file->f_op || !file->f_op->readdir)
  		goto out;
  
  	res = security_file_permission(file, MAY_READ);
  	if (res)
  		goto out;
  
  	res = mutex_lock_killable(&inode->i_mutex);
  	if (res)
  		goto out;
  
  	res = -ENOENT;
  	if (!IS_DEADDIR(inode)) {
  		res = file->f_op->readdir(file, buf, filler);
  		file_accessed(file);
  	}
  	mutex_unlock(&inode->i_mutex);
  out:
  	return res;
  }
  
  EXPORT_SYMBOL(vfs_readdir);
  
  /*
   * Traditional linux readdir() handling..
   *
   * "count=1" is a special case, meaning that the buffer is one
   * dirent-structure in size and that the code can't handle more
   * anyway. Thus the special "fillonedir()" function for that
   * case (the low-level handlers don't need to care about this).
   */
  
  #ifdef __ARCH_WANT_OLD_READDIR
  
  struct old_linux_dirent {
  	unsigned long	d_ino;
  	unsigned long	d_offset;
  	unsigned short	d_namlen;
  	char		d_name[1];
  };
  
  struct readdir_callback {
  	struct old_linux_dirent __user * dirent;
  	int result;
  };
  
  static int fillonedir(void * __buf, const char * name, int namlen, loff_t offset,
  		      u64 ino, unsigned int d_type)
  {
  	struct readdir_callback * buf = (struct readdir_callback *) __buf;
  	struct old_linux_dirent __user * dirent;
  	unsigned long d_ino;
  
  	if (buf->result)
  		return -EINVAL;
  	d_ino = ino;
  	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
  		buf->result = -EOVERFLOW;
  		return -EOVERFLOW;
  	}
  	buf->result++;
  	dirent = buf->dirent;
  	if (!access_ok(VERIFY_WRITE, dirent,
  			(unsigned long)(dirent->d_name + namlen + 1) -
  				(unsigned long)dirent))
  		goto efault;
  	if (	__put_user(d_ino, &dirent->d_ino) ||
  		__put_user(offset, &dirent->d_offset) ||
  		__put_user(namlen, &dirent->d_namlen) ||
  		__copy_to_user(dirent->d_name, name, namlen) ||
  		__put_user(0, dirent->d_name + namlen))
  		goto efault;
  	return 0;
  efault:
  	buf->result = -EFAULT;
  	return -EFAULT;
  }
  
  SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
  		struct old_linux_dirent __user *, dirent, unsigned int, count)
  {
  	int error;
  	struct file * file;
  	struct readdir_callback buf;
  
  	error = -EBADF;
  	file = fget(fd);
  	if (!file)
  		goto out;
  
  	buf.result = 0;
  	buf.dirent = dirent;
  
  	error = vfs_readdir(file, fillonedir, &buf);
  	if (buf.result)
  		error = buf.result;
  
  	fput(file);
  out:
  	return error;
  }
  
  #endif /* __ARCH_WANT_OLD_READDIR */
  
  /*
   * New, all-improved, singing, dancing, iBCS2-compliant getdents()
   * interface. 
   */
  struct linux_dirent {
  	unsigned long	d_ino;
  	unsigned long	d_off;
  	unsigned short	d_reclen;
  	char		d_name[1];
  };
  
  struct getdents_callback {
  	struct linux_dirent __user * current_dir;
  	struct linux_dirent __user * previous;
  	int count;
  	int error;
  };
  
  static int filldir(void * __buf, const char * name, int namlen, loff_t offset,
  		   u64 ino, unsigned int d_type)
  {
  	struct linux_dirent __user * dirent;
  	struct getdents_callback * buf = (struct getdents_callback *) __buf;
  	unsigned long d_ino;
  	int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
  		sizeof(long));
  
  	buf->error = -EINVAL;	/* only used if we fail.. */
  	if (reclen > buf->count)
  		return -EINVAL;
  	d_ino = ino;
  	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
  		buf->error = -EOVERFLOW;
  		return -EOVERFLOW;
  	}
  	dirent = buf->previous;
  	if (dirent) {
  		if (__put_user(offset, &dirent->d_off))
  			goto efault;
  	}
  	dirent = buf->current_dir;
  	if (__put_user(d_ino, &dirent->d_ino))
  		goto efault;
  	if (__put_user(reclen, &dirent->d_reclen))
  		goto efault;
  	if (copy_to_user(dirent->d_name, name, namlen))
  		goto efault;
  	if (__put_user(0, dirent->d_name + namlen))
  		goto efault;
  	if (__put_user(d_type, (char __user *) dirent + reclen - 1))
  		goto efault;
  	buf->previous = dirent;
  	dirent = (void __user *)dirent + reclen;
  	buf->current_dir = dirent;
  	buf->count -= reclen;
  	return 0;
  efault:
  	buf->error = -EFAULT;
  	return -EFAULT;
  }
  
  SYSCALL_DEFINE3(getdents, unsigned int, fd,
  		struct linux_dirent __user *, dirent, unsigned int, count)
  {
  	struct file * file;
  	struct linux_dirent __user * lastdirent;
  	struct getdents_callback buf;
  	int error;
  
  	error = -EFAULT;
  	if (!access_ok(VERIFY_WRITE, dirent, count))
  		goto out;
  
  	error = -EBADF;
  	file = fget(fd);
  	if (!file)
  		goto out;
  
  	buf.current_dir = dirent;
  	buf.previous = NULL;
  	buf.count = count;
  	buf.error = 0;
  
  	error = vfs_readdir(file, filldir, &buf);
  	if (error >= 0)
  		error = buf.error;
  	lastdirent = buf.previous;
  	if (lastdirent) {
  		if (put_user(file->f_pos, &lastdirent->d_off))
  			error = -EFAULT;
  		else
  			error = count - buf.count;
  	}
  	fput(file);
  out:
  	return error;
  }
  
  struct getdents_callback64 {
  	struct linux_dirent64 __user * current_dir;
  	struct linux_dirent64 __user * previous;
  	int count;
  	int error;
  };
  
  static int filldir64(void * __buf, const char * name, int namlen, loff_t offset,
  		     u64 ino, unsigned int d_type)
  {
  	struct linux_dirent64 __user *dirent;
  	struct getdents_callback64 * buf = (struct getdents_callback64 *) __buf;
  	int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
  		sizeof(u64));
  
  	buf->error = -EINVAL;	/* only used if we fail.. */
  	if (reclen > buf->count)
  		return -EINVAL;
  	dirent = buf->previous;
  	if (dirent) {
  		if (__put_user(offset, &dirent->d_off))
  			goto efault;
  	}
  	dirent = buf->current_dir;
  	if (__put_user(ino, &dirent->d_ino))
  		goto efault;
  	if (__put_user(0, &dirent->d_off))
  		goto efault;
  	if (__put_user(reclen, &dirent->d_reclen))
  		goto efault;
  	if (__put_user(d_type, &dirent->d_type))
  		goto efault;
  	if (copy_to_user(dirent->d_name, name, namlen))
  		goto efault;
  	if (__put_user(0, dirent->d_name + namlen))
  		goto efault;
  	buf->previous = dirent;
  	dirent = (void __user *)dirent + reclen;
  	buf->current_dir = dirent;
  	buf->count -= reclen;
  	return 0;
  efault:
  	buf->error = -EFAULT;
  	return -EFAULT;
  }
  
  SYSCALL_DEFINE3(getdents64, unsigned int, fd,
  		struct linux_dirent64 __user *, dirent, unsigned int, count)
  {
  	struct file * file;
  	struct linux_dirent64 __user * lastdirent;
  	struct getdents_callback64 buf;
  	int error;
  
  	error = -EFAULT;
  	if (!access_ok(VERIFY_WRITE, dirent, count))
  		goto out;
  
  	error = -EBADF;
  	file = fget(fd);
  	if (!file)
  		goto out;
  
  	buf.current_dir = dirent;
  	buf.previous = NULL;
  	buf.count = count;
  	buf.error = 0;
  
  	error = vfs_readdir(file, filldir64, &buf);
  	if (error >= 0)
  		error = buf.error;
  	lastdirent = buf.previous;
  	if (lastdirent) {
  		typeof(lastdirent->d_off) d_off = file->f_pos;
  		if (__put_user(d_off, &lastdirent->d_off))
  			error = -EFAULT;
  		else
  			error = count - buf.count;
  	}
  	fput(file);
  out:
  	return error;
  }
  