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
7struct bpf_perf_event_value___local {
8	__u64 counter;
9	__u64 enabled;
10	__u64 running;
11} __attribute__((preserve_access_index));
12
13/* map of perf event fds, num_cpu * num_metric entries */
14struct {
15	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
16	__uint(key_size, sizeof(u32));
17	__uint(value_size, sizeof(int));
18} events SEC(".maps");
19
20/* readings at fentry */
21struct {
22	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
23	__uint(key_size, sizeof(u32));
24	__uint(value_size, sizeof(struct bpf_perf_event_value___local));
25} fentry_readings SEC(".maps");
26
27/* accumulated readings */
28struct {
29	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
30	__uint(key_size, sizeof(u32));
31	__uint(value_size, sizeof(struct bpf_perf_event_value___local));
32} accum_readings SEC(".maps");
33
34/* sample counts, one per cpu */
35struct {
36	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
37	__uint(key_size, sizeof(u32));
38	__uint(value_size, sizeof(u64));
39} counts SEC(".maps");
40
41const volatile __u32 num_cpu = 1;
42const volatile __u32 num_metric = 1;
43#define MAX_NUM_MATRICS 4
44
45SEC("fentry/XXX")
46int BPF_PROG(fentry_XXX)
47{
48	struct bpf_perf_event_value___local *ptrs[MAX_NUM_MATRICS];
49	u32 key = bpf_get_smp_processor_id();
50	u32 i;
51
52	/* look up before reading, to reduce error */
53	for (i = 0; i < num_metric && i < MAX_NUM_MATRICS; i++) {
54		u32 flag = i;
55
56		ptrs[i] = bpf_map_lookup_elem(&fentry_readings, &flag);
57		if (!ptrs[i])
58			return 0;
59	}
60
61	for (i = 0; i < num_metric && i < MAX_NUM_MATRICS; i++) {
62		struct bpf_perf_event_value___local reading;
63		int err;
64
65		err = bpf_perf_event_read_value(&events, key, (void *)&reading,
66						sizeof(reading));
67		if (err)
68			return 0;
69		*(ptrs[i]) = reading;
70		key += num_cpu;
71	}
72
73	return 0;
74}
75
76static inline void
77fexit_update_maps(u32 id, struct bpf_perf_event_value___local *after)
78{
79	struct bpf_perf_event_value___local *before, diff;
80
81	before = bpf_map_lookup_elem(&fentry_readings, &id);
82	/* only account samples with a valid fentry_reading */
83	if (before && before->counter) {
84		struct bpf_perf_event_value___local *accum;
85
86		diff.counter = after->counter - before->counter;
87		diff.enabled = after->enabled - before->enabled;
88		diff.running = after->running - before->running;
89
90		accum = bpf_map_lookup_elem(&accum_readings, &id);
91		if (accum) {
92			accum->counter += diff.counter;
93			accum->enabled += diff.enabled;
94			accum->running += diff.running;
95		}
96	}
97}
98
99SEC("fexit/XXX")
100int BPF_PROG(fexit_XXX)
101{
102	struct bpf_perf_event_value___local readings[MAX_NUM_MATRICS];
103	u32 cpu = bpf_get_smp_processor_id();
104	u32 i, zero = 0;
105	int err;
106	u64 *count;
107
108	/* read all events before updating the maps, to reduce error */
109	for (i = 0; i < num_metric && i < MAX_NUM_MATRICS; i++) {
110		err = bpf_perf_event_read_value(&events, cpu + i * num_cpu,
111						(void *)(readings + i),
112						sizeof(*readings));
113		if (err)
114			return 0;
115	}
116	count = bpf_map_lookup_elem(&counts, &zero);
117	if (count) {
118		*count += 1;
119		for (i = 0; i < num_metric && i < MAX_NUM_MATRICS; i++)
120			fexit_update_maps(i, &readings[i]);
121	}
122	return 0;
123}
124
125char LICENSE[] SEC("license") = "Dual BSD/GPL";
126