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 */
8 struct {
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 */
15 struct {
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 */
23 struct {
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
30 const volatile __u32 num_cpu = 1;
31
32 SEC("fentry/XXX")
BPF_PROG(fentry_XXX)33 int 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
52 static inline void
fexit_update_maps(struct bpf_perf_event_value * after)53 fexit_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
76 SEC("fexit/XXX")
BPF_PROG(fexit_XXX)77 int 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
92 char LICENSE[] SEC("license") = "Dual BSD/GPL";
93