netdev - [PATCH v4 bpf-next 10/13] bpf: test_run: add skb_shared_info pointer in bpf_test

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Date:   Fri,  2 Oct 2020 16:42:08 +0200
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     bpf@...r.kernel.org, netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, ast@...nel.org,
        daniel@...earbox.net, shayagr@...zon.com, sameehj@...zon.com,
        john.fastabend@...il.com, dsahern@...nel.org, brouer@...hat.com,
        lorenzo.bianconi@...hat.com, echaudro@...hat.com
Subject: [PATCH v4 bpf-next 10/13] bpf: test_run: add skb_shared_info pointer in bpf_test_finish signature

introduce skb_shared_info pointer in bpf_test_finish signature in order
to copy back paged data from a xdp multi-buff frame to userspace buffer

Tested-by: Eelco Chaudron <echaudro@...hat.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
---
 net/bpf/test_run.c | 58 ++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 51 insertions(+), 7 deletions(-)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index ec7286cd051b..7e33181f88ee 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -79,9 +79,23 @@ static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
 	return ret;
 }
 
+static int bpf_test_get_buff_data_len(struct skb_shared_info *sinfo)
+{
+	int i, size = 0;
+
+	if (likely(!sinfo))
+		return 0;
+
+	for (i = 0; i < sinfo->nr_frags; i++)
+		size += skb_frag_size(&sinfo->frags[i]);
+
+	return size;
+}
+
 static int bpf_test_finish(const union bpf_attr *kattr,
 			   union bpf_attr __user *uattr, const void *data,
-			   u32 size, u32 retval, u32 duration)
+			   struct skb_shared_info *sinfo, u32 size,
+			   u32 retval, u32 duration)
 {
 	void __user *data_out = u64_to_user_ptr(kattr->test.data_out);
 	int err = -EFAULT;
@@ -96,8 +110,35 @@ static int bpf_test_finish(const union bpf_attr *kattr,
 		err = -ENOSPC;
 	}
 
-	if (data_out && copy_to_user(data_out, data, copy_size))
-		goto out;
+	if (data_out) {
+		int len = copy_size - bpf_test_get_buff_data_len(sinfo);
+
+		if (copy_to_user(data_out, data, len))
+			goto out;
+
+		if (sinfo) {
+			int i, offset = len, data_len;
+
+			for (i = 0; i < sinfo->nr_frags; i++) {
+				skb_frag_t *frag = &sinfo->frags[i];
+
+				if (offset >= copy_size) {
+					err = -ENOSPC;
+					break;
+				}
+
+				data_len = min_t(int, copy_size - offset,
+						 skb_frag_size(frag));
+				if (copy_to_user(data_out + offset,
+						 skb_frag_address(frag),
+						 data_len))
+					goto out;
+
+				offset += data_len;
+			}
+		}
+	}
+
 	if (copy_to_user(&uattr->test.data_size_out, &size, sizeof(size)))
 		goto out;
 	if (copy_to_user(&uattr->test.retval, &retval, sizeof(retval)))
@@ -598,7 +639,8 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
 	/* bpf program can never convert linear skb to non-linear */
 	if (WARN_ON_ONCE(skb_is_nonlinear(skb)))
 		size = skb_headlen(skb);
-	ret = bpf_test_finish(kattr, uattr, skb->data, size, retval, duration);
+	ret = bpf_test_finish(kattr, uattr, skb->data, NULL, size, retval,
+			      duration);
 	if (!ret)
 		ret = bpf_ctx_finish(kattr, uattr, ctx,
 				     sizeof(struct __sk_buff));
@@ -683,7 +725,9 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
 	if (xdp.data != data + headroom || xdp.data_end != xdp.data + size)
 		size += xdp.data_end - xdp.data - data_len;
 
-	ret = bpf_test_finish(kattr, uattr, xdp.data, size, retval, duration);
+	ret = bpf_test_finish(kattr, uattr, xdp.data, sinfo, size, retval,
+			      duration);
+
 out:
 	bpf_prog_change_xdp(prog, NULL);
 	for (i = 0; i < sinfo->nr_frags; i++)
@@ -793,8 +837,8 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
 	do_div(time_spent, repeat);
 	duration = time_spent > U32_MAX ? U32_MAX : (u32)time_spent;
 
-	ret = bpf_test_finish(kattr, uattr, &flow_keys, sizeof(flow_keys),
-			      retval, duration);
+	ret = bpf_test_finish(kattr, uattr, &flow_keys, NULL,
+			      sizeof(flow_keys), retval, duration);
 	if (!ret)
 		ret = bpf_ctx_finish(kattr, uattr, user_ctx,
 				     sizeof(struct bpf_flow_keys));
-- 
2.26.2