Function extattr_get_vp

freebsd/kern/vfs_extattr.c:328–386

- * Get a named extended attribute on a file or directory * * Arguments: unlocked vnode "vp", attribute namespace "attrnamespace", * kernelspace string pointer "attrname", userspace buffer * pointer "data", buffer length "nbytes", thread "td". * Returns: 0 on success, an error number otherwise * Locks: none * References: vp must be a valid reference for the duration o

 * References: vp must be a valid reference for the duration of the call
 */
static int
extattr_get_vp(struct vnode *vp, int attrnamespace, const char *attrname,
    void *data, size_t nbytes, struct thread *td)
{
	struct uio auio, *auiop;
	struct iovec aiov;
	ssize_t cnt;
	size_t size, *sizep;
	int error;

	if (nbytes > IOSIZE_MAX)
		return (EINVAL);

	vn_lock(vp, LK_SHARED | LK_RETRY);

	/*
	 * Slightly unusual semantics: if the user provides a NULL data
	 * pointer, they don't want to receive the data, just the maximum
	 * read length.
	 */
	auiop = NULL;
	sizep = NULL;
	cnt = 0;
	if (data != NULL) {
		aiov.iov_base = data;
		aiov.iov_len = nbytes;
		auio.uio_iov = &aiov;
		auio.uio_iovcnt = 1;
		auio.uio_offset = 0;
		auio.uio_resid = nbytes;
		auio.uio_rw = UIO_READ;
		auio.uio_segflg = UIO_USERSPACE;
		auio.uio_td = td;
		auiop = &auio;
		cnt = nbytes;
	} else
		sizep = &size;

#ifdef MAC
	error = mac_vnode_check_getextattr(td->td_ucred, vp, attrnamespace,
	    attrname);
	if (error)
		goto done;
#endif

	error = VOP_GETEXTATTR(vp, attrnamespace, attrname, auiop, sizep,
	    td->td_ucred, td);

	if (auiop != NULL) {
		cnt -= auio.uio_resid;
		td->td_retval[0] = cnt;
	} else
		td->td_retval[0] = size;
#ifdef MAC
done:
#endif
	VOP_UNLOCK(vp);
	return (error);