1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2018 Facebook
3
4 #include <vmlinux.h>
5 #include <bpf/bpf_helpers.h>
6
7 #ifndef PERF_MAX_STACK_DEPTH
8 #define PERF_MAX_STACK_DEPTH 127
9 #endif
10
11 struct {
12 __uint(type, BPF_MAP_TYPE_ARRAY);
13 __uint(max_entries, 1);
14 __type(key, __u32);
15 __type(value, __u32);
16 } control_map SEC(".maps");
17
18 struct {
19 __uint(type, BPF_MAP_TYPE_HASH);
20 __uint(max_entries, 16384);
21 __type(key, __u32);
22 __type(value, __u32);
23 } stackid_hmap SEC(".maps");
24
25 typedef __u64 stack_trace_t[PERF_MAX_STACK_DEPTH];
26
27 struct {
28 __uint(type, BPF_MAP_TYPE_STACK_TRACE);
29 __uint(max_entries, 16384);
30 __type(key, __u32);
31 __type(value, stack_trace_t);
32 } stackmap SEC(".maps");
33
34 struct {
35 __uint(type, BPF_MAP_TYPE_ARRAY);
36 __uint(max_entries, 16384);
37 __type(key, __u32);
38 __type(value, stack_trace_t);
39 } stack_amap SEC(".maps");
40
41 /* taken from /sys/kernel/tracing/events/sched/sched_switch/format */
42 struct sched_switch_args {
43 unsigned long long pad;
44 char prev_comm[TASK_COMM_LEN];
45 int prev_pid;
46 int prev_prio;
47 long long prev_state;
48 char next_comm[TASK_COMM_LEN];
49 int next_pid;
50 int next_prio;
51 };
52
53 SEC("tracepoint/sched/sched_switch")
54 int oncpu(struct sched_switch_args *ctx)
55 {
56 __u32 max_len = PERF_MAX_STACK_DEPTH * sizeof(__u64);
57 __u32 key = 0, val = 0, *value_p;
58 void *stack_p;
59
60 value_p = bpf_map_lookup_elem(&control_map, &key);
61 if (value_p && *value_p)
62 return 0; /* skip if non-zero *value_p */
63
64 /* The size of stackmap and stackid_hmap should be the same */
65 key = bpf_get_stackid(ctx, &stackmap, 0);
66 if ((int)key >= 0) {
67 bpf_map_update_elem(&stackid_hmap, &key, &val, 0);
68 stack_p = bpf_map_lookup_elem(&stack_amap, &key);
69 if (stack_p)
70 bpf_get_stack(ctx, stack_p, max_len, 0);
71 }
72
73 return 0;
74 }
75
76 char _license[] SEC("license") = "GPL";
77
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