bpf: Switch to offsetofend in BPF_PROG_TEST_RUN

Switch existing pattern of "offsetof(..., member) + FIELD_SIZEOF(...,
member)' to "offsetofend(..., member)" which does exactly what
we need without all the copy-paste.
Suggested-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191210191933.105321-1-sdf@google.com

net/bpf/test_run.c

@@ -252,22 +252,19 @@ static int convert___skb_to_skb(struct sk_buff *skb, struct __sk_buff *__skb)
 
 	/* priority is allowed */
 
-	if (!range_is_zero(__skb, offsetof(struct __sk_buff, priority) +
-			   FIELD_SIZEOF(struct __sk_buff, priority),
+	if (!range_is_zero(__skb, offsetofend(struct __sk_buff, priority),
 			   offsetof(struct __sk_buff, cb)))
 		return -EINVAL;
 
 	/* cb is allowed */
 
-	if (!range_is_zero(__skb, offsetof(struct __sk_buff, cb) +
-			   FIELD_SIZEOF(struct __sk_buff, cb),
+	if (!range_is_zero(__skb, offsetofend(struct __sk_buff, cb),
 			   offsetof(struct __sk_buff, tstamp)))
 		return -EINVAL;
 
 	/* tstamp is allowed */
 
-	if (!range_is_zero(__skb, offsetof(struct __sk_buff, tstamp) +
-			   FIELD_SIZEOF(struct __sk_buff, tstamp),
+	if (!range_is_zero(__skb, offsetofend(struct __sk_buff, tstamp),
 			   sizeof(struct __sk_buff)))
 		return -EINVAL;
 
@@ -437,8 +434,7 @@ static int verify_user_bpf_flow_keys(struct bpf_flow_keys *ctx)
 
 	/* flags is allowed */
 
-	if (!range_is_zero(ctx, offsetof(struct bpf_flow_keys, flags) +
-			   FIELD_SIZEOF(struct bpf_flow_keys, flags),
+	if (!range_is_zero(ctx, offsetofend(struct bpf_flow_keys, flags),
 			   sizeof(struct bpf_flow_keys)))
 		return -EINVAL;