How to share skb with user-space in kprobe

[xd121614]

I want to capture traffic from unix socket and print skb in user-space.
When I use bpf_perf_event_output(), error occurs:
///////////////////////////////////////////////////////////////////////
root@ebpf:~# ./kprobe
libbpf: loading object 'kprobe_bpf' from buffer
...
libbpf: prog 'do_unixsocket': BPF program load failed: Permission denied
libbpf: prog 'do_unixsocket': -- BEGIN PROG LOAD LOG --
R1 type=ctx expected=fp
; struct sk_buff* skb = (struct sk_buff *)PT_REGS_PARM1(ctx);
0: (79) r2 = *(u64 *)(r1 +112)
; if (!skb) {
1: (15) if r2 == 0x0 goto pc+11
R1=ctx(id=0,off=0,imm=0) R2_w=inv(id=0) R10=fp0
; ((__u64) data_len << 32) |
2: (61) r3 = *(u32 *)(r2 +116)
R2 invalid mem access 'inv'
processed 3 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
-- END PROG LOAD LOG --
libbpf: prog 'do_unixsocket': failed to load: -13
libbpf: failed to load object 'kprobe_bpf'
libbpf: failed to load BPF skeleton 'kprobe_bpf': -13
Failed to open BPF skeleton
///////////////////////////////////////////////////////////////////////

The code is as follows.
`#ifndef __packed
#define __packed attribute((packed))
#endif

#define MAX_CPUS 256

struct pkt_trace_metadata {
__u16 pkt_len;
__u16 cap_len;
unsigned char packet[];
} __packed;
struct {
__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
__uint(max_entries, MAX_CPUS);
__type(key, int);
__type(value, __u32);
} pb SEC(".maps");

char LICENSE[] SEC("license") = "Dual BSD/GPL";

SEC("kprobe/unix_stream_read_actor")
int BPF_KPROBE(do_unixsocket)
{
void* data;
int data_len;
struct pkt_trace_metadata metadata;
struct sk_buff* skb = (struct sk_buff *)PT_REGS_PARM1(ctx);
data = skb->data;
data_len = skb->data_len;
bpf_perf_event_output(ctx, &pb,
((__u64) data_len << 32) |
BPF_F_CURRENT_CPU,
&metadata, sizeof(metadata));
return 0;
}`