Function zbuf_setup

freebsd/net/bpf_zerocopy.c:178–234

* Create a zbuf describing a range of user address space memory. Validate * page alignment, size requirements, etc. */

 * page alignment, size requirements, etc.
 */
static int
zbuf_setup(struct thread *td, vm_offset_t uaddr, size_t len,
    struct zbuf **zbp)
{
	struct zbuf *zb;
	struct vm_map *map;
	int error, i;

	*zbp = NULL;

	/*
	 * User address must be page-aligned.
	 */
	if (uaddr & PAGE_MASK)
		return (EINVAL);

	/*
	 * Length must be an integer number of full pages.
	 */
	if (len & PAGE_MASK)
		return (EINVAL);

	/*
	 * Length must not exceed per-buffer resource limit.
	 */
	if ((len / PAGE_SIZE) > BPF_MAX_PAGES)
		return (EINVAL);

	/*
	 * Allocate the buffer and set up each page with is own sf_buf.
	 */
	error = 0;
	zb = malloc(sizeof(*zb), M_BPF, M_ZERO | M_WAITOK);
	zb->zb_uaddr = uaddr;
	zb->zb_size = len;
	zb->zb_numpages = len / PAGE_SIZE;
	zb->zb_pages = malloc(sizeof(struct sf_buf *) *
	    zb->zb_numpages, M_BPF, M_ZERO | M_WAITOK);
	map = &td->td_proc->p_vmspace->vm_map;
	for (i = 0; i < zb->zb_numpages; i++) {
		zb->zb_pages[i] = zbuf_sfbuf_get(map,
		    uaddr + (i * PAGE_SIZE));
		if (zb->zb_pages[i] == NULL) {
			error = EFAULT;
			goto error;
		}
	}
	zb->zb_header =
	    (struct bpf_zbuf_header *)sf_buf_kva(zb->zb_pages[0]);
	bzero(zb->zb_header, sizeof(*zb->zb_header));
	*zbp = zb;
	return (0);

error:
	zbuf_free(zb);
	return (error);
}