[PATCH v4 bpf-next 09/13] bpf: introduce multibuff support to bpf_prog_test_run_xdp()

[Lorenzo Bianconi <lorenzo@xxxxxxxxxx>]

Introduce the capability to allocate a xdp multi-buff in
bpf_prog_test_run_xdp routine. This is a preliminary patch to introduce
the selftests for new xdp multi-buff ebpf helpers

Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
---
 net/bpf/test_run.c | 51 ++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 43 insertions(+), 8 deletions(-)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index bd291f5f539c..ec7286cd051b 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -617,44 +617,79 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
 {
 	u32 tailroom = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
 	u32 headroom = XDP_PACKET_HEADROOM;
-	u32 size = kattr->test.data_size_in;
 	u32 repeat = kattr->test.repeat;
 	struct netdev_rx_queue *rxqueue;
+	struct skb_shared_info *sinfo;
 	struct xdp_buff xdp = {};
+	u32 max_data_sz, size;
 	u32 retval, duration;
-	u32 max_data_sz;
+	int i, ret, data_len;
 	void *data;
-	int ret;
 
 	if (kattr->test.ctx_in || kattr->test.ctx_out)
 		return -EINVAL;
 
-	/* XDP have extra tailroom as (most) drivers use full page */
 	max_data_sz = 4096 - headroom - tailroom;
+	size = min_t(u32, kattr->test.data_size_in, max_data_sz);
+	data_len = size;
 
-	data = bpf_test_init(kattr, kattr->test.data_size_in,
-			     max_data_sz, headroom, tailroom);
+	data = bpf_test_init(kattr, size, max_data_sz, headroom, tailroom);
 	if (IS_ERR(data))
 		return PTR_ERR(data);
 
 	xdp.data_hard_start = data;
 	xdp.data = data + headroom;
 	xdp.data_meta = xdp.data;
-	xdp.data_end = xdp.data + size;
+	xdp.data_end = xdp.data + data_len;
 	xdp.frame_sz = headroom + max_data_sz + tailroom;
 
+	sinfo = xdp_get_shared_info_from_buff(&xdp);
+	if (unlikely(kattr->test.data_size_in > size)) {
+		void __user *data_in = u64_to_user_ptr(kattr->test.data_in);
+
+		while (size < kattr->test.data_size_in) {
+			skb_frag_t *frag = &sinfo->frags[sinfo->nr_frags];
+			struct page *page;
+			int data_len;
+
+			page = alloc_page(GFP_KERNEL);
+			if (!page) {
+				ret = -ENOMEM;
+				goto out;
+			}
+
+			__skb_frag_set_page(frag, page);
+			data_len = min_t(int, kattr->test.data_size_in - size,
+					 PAGE_SIZE);
+			skb_frag_size_set(frag, data_len);
+			if (copy_from_user(page_address(page), data_in + size,
+					   data_len)) {
+				ret = -EFAULT;
+				goto out;
+			}
+			sinfo->nr_frags++;
+			size += data_len;
+		}
+		xdp.mb = 1;
+	}
+
 	rxqueue = __netif_get_rx_queue(current->nsproxy->net_ns->loopback_dev, 0);
 	xdp.rxq = &rxqueue->xdp_rxq;
 	bpf_prog_change_xdp(NULL, prog);
 	ret = bpf_test_run(prog, &xdp, repeat, &retval, &duration, true);
 	if (ret)
 		goto out;
+
 	if (xdp.data != data + headroom || xdp.data_end != xdp.data + size)
-		size = xdp.data_end - xdp.data;
+		size += xdp.data_end - xdp.data - data_len;
+
 	ret = bpf_test_finish(kattr, uattr, xdp.data, size, retval, duration);
 out:
 	bpf_prog_change_xdp(prog, NULL);
+	for (i = 0; i < sinfo->nr_frags; i++)
+		__free_page(skb_frag_page(&sinfo->frags[i]));
 	kfree(data);
+
 	return ret;
 }
 
-- 
2.26.2