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

[Lorenzo Bianconi]

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 <echau...@redhat.com>
Signed-off-by: Lorenzo Bianconi <lore...@kernel.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