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
10 int valid = 0;
11 int required_size_out = 0;
12 int written_stack_out = 0;
13 int written_global_out = 0;
14
15 struct {
16 __u64 _a;
17 __u64 _b;
18 __u64 _c;
19 } fpbe[30] = {0};
20
21 SEC("perf_event")
22 int 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
50 char _license[] SEC("license") = "GPL";
51
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