1// SPDX-License-Identifier: GPL-2.0
 2#include <linux/ptrace.h>
 3#include <linux/version.h>
 4#include <uapi/linux/bpf.h>
 5#include <bpf/bpf_helpers.h>
 6
 7#define SAMPLE_SIZE 64ul
 8
 9struct {
10	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
11	__uint(key_size, sizeof(int));
12	__uint(value_size, sizeof(u32));
13} my_map SEC(".maps");
14
15SEC("xdp_sample")
16int xdp_sample_prog(struct xdp_md *ctx)
17{
18	void *data_end = (void *)(long)ctx->data_end;
19	void *data = (void *)(long)ctx->data;
20
21	/* Metadata will be in the perf event before the packet data. */
22	struct S {
23		u16 cookie;
24		u16 pkt_len;
25	} __packed metadata;
26
27	if (data < data_end) {
28		/* The XDP perf_event_output handler will use the upper 32 bits
29		 * of the flags argument as a number of bytes to include of the
30		 * packet payload in the event data. If the size is too big, the
31		 * call to bpf_perf_event_output will fail and return -EFAULT.
32		 *
33		 * See bpf_xdp_event_output in net/core/filter.c.
34		 *
35		 * The BPF_F_CURRENT_CPU flag means that the event output fd
36		 * will be indexed by the CPU number in the event map.
37		 */
38		u64 flags = BPF_F_CURRENT_CPU;
39		u16 sample_size;
40		int ret;
41
42		metadata.cookie = 0xdead;
43		metadata.pkt_len = (u16)(data_end - data);
44		sample_size = min(metadata.pkt_len, SAMPLE_SIZE);
45		flags |= (u64)sample_size << 32;
46
47		ret = bpf_perf_event_output(ctx, &my_map, flags,
48					    &metadata, sizeof(metadata));
49		if (ret)
50			bpf_printk("perf_event_output failed: %d\n", ret);
51	}
52
53	return XDP_PASS;
54}
55
56char _license[] SEC("license") = "GPL";
57u32 _version SEC("version") = LINUX_VERSION_CODE;