[PATCH bpf-next] bpf: allow bpf_skb_load_bytes in tracing prog

[Philo Lu <lulie@linux.alibaba.com>]

Allow using helper bpf_skb_load_bytes with BPF_PROG_TYPE_TRACING, which
is useful for skb parsing in raw_tp/fentry/fexit, especially for
non-linear paged skb data.

Selftests will be added if this patch is acceptable.

Signed-off-by: Philo Lu <lulie@linux.alibaba.com>
---
 kernel/trace/bpf_trace.c |  3 +++
 net/core/filter.c        | 13 +++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 241ddf5e3895..4b928d929962 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1945,6 +1945,7 @@ static const struct bpf_func_proto bpf_perf_event_output_proto_raw_tp = {
 extern const struct bpf_func_proto bpf_skb_output_proto;
 extern const struct bpf_func_proto bpf_xdp_output_proto;
 extern const struct bpf_func_proto bpf_xdp_get_buff_len_trace_proto;
+extern const struct bpf_func_proto bpf_skb_load_bytes_trace_proto;
 
 BPF_CALL_3(bpf_get_stackid_raw_tp, struct bpf_raw_tracepoint_args *, args,
 	   struct bpf_map *, map, u64, flags)
@@ -2048,6 +2049,8 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_get_socket_ptr_cookie_proto;
 	case BPF_FUNC_xdp_get_buff_len:
 		return &bpf_xdp_get_buff_len_trace_proto;
+	case BPF_FUNC_skb_load_bytes:
+		return &bpf_skb_load_bytes_trace_proto;
 #endif
 	case BPF_FUNC_seq_printf:
 		return prog->expected_attach_type == BPF_TRACE_ITER ?
diff --git a/net/core/filter.c b/net/core/filter.c
index 9f806cfbc654..ec5622ae8770 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1764,6 +1764,19 @@ static const struct bpf_func_proto bpf_skb_load_bytes_proto = {
 	.arg4_type	= ARG_CONST_SIZE,
 };
 
+BTF_ID_LIST_SINGLE(bpf_skb_load_bytes_btf_ids, struct, sk_buff)
+
+const struct bpf_func_proto bpf_skb_load_bytes_trace_proto = {
+	.func		= bpf_skb_load_bytes,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_BTF_ID,
+	.arg1_btf_id	= &bpf_skb_load_bytes_btf_ids[0],
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_PTR_TO_UNINIT_MEM,
+	.arg4_type	= ARG_CONST_SIZE,
+};
+
 int __bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset, void *to, u32 len)
 {
 	return ____bpf_skb_load_bytes(skb, offset, to, len);
-- 
2.32.0.3.g01195cf9f