1// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 2// Copyright (c) 2020 Facebook
 3#include "vmlinux.h"
 4#include <bpf/bpf_helpers.h>
 5#include <bpf/bpf_tracing.h>
 6
 7/* map of perf event fds, num_cpu * num_metric entries */
 8struct {
 9	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
10	__uint(key_size, sizeof(__u32));
11	__uint(value_size, sizeof(int));
12} events SEC(".maps");
13
14/* readings at fentry */
15struct {
16	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
17	__uint(key_size, sizeof(__u32));
18	__uint(value_size, sizeof(struct bpf_perf_event_value));
19	__uint(max_entries, 1);
20} fentry_readings SEC(".maps");
21
22/* accumulated readings */
23struct {
24	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
25	__uint(key_size, sizeof(__u32));
26	__uint(value_size, sizeof(struct bpf_perf_event_value));
27	__uint(max_entries, 1);
28} accum_readings SEC(".maps");
29
30const volatile __u32 num_cpu = 1;
31
32SEC("fentry/XXX")
33int BPF_PROG(fentry_XXX)
34{
35	__u32 key = bpf_get_smp_processor_id();
36	struct bpf_perf_event_value *ptr;
37	__u32 zero = 0;
38	long err;
39
40	/* look up before reading, to reduce error */
41	ptr = bpf_map_lookup_elem(&fentry_readings, &zero);
42	if (!ptr)
43		return 0;
44
45	err = bpf_perf_event_read_value(&events, key, ptr, sizeof(*ptr));
46	if (err)
47		return 0;
48
49	return 0;
50}
51
52static inline void
53fexit_update_maps(struct bpf_perf_event_value *after)
54{
55	struct bpf_perf_event_value *before, diff;
56	__u32 zero = 0;
57
58	before = bpf_map_lookup_elem(&fentry_readings, &zero);
59	/* only account samples with a valid fentry_reading */
60	if (before && before->counter) {
61		struct bpf_perf_event_value *accum;
62
63		diff.counter = after->counter - before->counter;
64		diff.enabled = after->enabled - before->enabled;
65		diff.running = after->running - before->running;
66
67		accum = bpf_map_lookup_elem(&accum_readings, &zero);
68		if (accum) {
69			accum->counter += diff.counter;
70			accum->enabled += diff.enabled;
71			accum->running += diff.running;
72		}
73	}
74}
75
76SEC("fexit/XXX")
77int BPF_PROG(fexit_XXX)
78{
79	struct bpf_perf_event_value reading;
80	__u32 cpu = bpf_get_smp_processor_id();
81	int err;
82
83	/* read all events before updating the maps, to reduce error */
84	err = bpf_perf_event_read_value(&events, cpu, &reading, sizeof(reading));
85	if (err)
86		return 0;
87
88	fexit_update_maps(&reading);
89	return 0;
90}
91
92char LICENSE[] SEC("license") = "Dual BSD/GPL";