1// SPDX-License-Identifier: GPL-2.0
2// Copyright (c) 2019 Facebook
3
4#include <stddef.h>
5#include <linux/ptrace.h>
6#include <linux/bpf.h>
7#include <bpf/bpf_helpers.h>
8#include <bpf/bpf_tracing.h>
9
10int valid = 0;
11int required_size_out = 0;
12int written_stack_out = 0;
13int written_global_out = 0;
14
15struct {
16	__u64 _a;
17	__u64 _b;
18	__u64 _c;
19} fpbe[30] = {0};
20
21SEC("perf_event")
22int perf_branches(void *ctx)
23{
24	__u64 entries[4 * 3] = {0};
25	int required_size, written_stack, written_global;
26
27	/* write to stack */
28	written_stack = bpf_read_branch_records(ctx, entries, sizeof(entries), 0);
29	/* ignore spurious events */
30	if (!written_stack)
31		return 1;
32
33	/* get required size */
34	required_size = bpf_read_branch_records(ctx, NULL, 0,
35						BPF_F_GET_BRANCH_RECORDS_SIZE);
36
37	written_global = bpf_read_branch_records(ctx, fpbe, sizeof(fpbe), 0);
38	/* ignore spurious events */
39	if (!written_global)
40		return 1;
41
42	required_size_out = required_size;
43	written_stack_out = written_stack;
44	written_global_out = written_global;
45	valid = 1;
46
47	return 0;
48}
49
50char _license[] SEC("license") = "GPL";
51