stacktrace_map.c

 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
11struct {
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
18struct {
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
25typedef __u64 stack_trace_t[PERF_MAX_STACK_DEPTH];
26
27struct {
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
34struct {
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 */
42struct 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__u32 stack_id;
54SEC("tracepoint/sched/sched_switch")
55int oncpu(struct sched_switch_args *ctx)
56{
57	__u32 max_len = PERF_MAX_STACK_DEPTH * sizeof(__u64);
58	__u32 key = 0, val = 0, *value_p;
59	void *stack_p;
60
61	value_p = bpf_map_lookup_elem(&control_map, &key);
62	if (value_p && *value_p)
63		return 0; /* skip if non-zero *value_p */
64
65	/* The size of stackmap and stackid_hmap should be the same */
66	key = bpf_get_stackid(ctx, &stackmap, 0);
67	if ((int)key >= 0) {
68		stack_id = key;
69		bpf_map_update_elem(&stackid_hmap, &key, &val, 0);
70		stack_p = bpf_map_lookup_elem(&stack_amap, &key);
71		if (stack_p)
72			bpf_get_stack(ctx, stack_p, max_len, 0);
73	}
74
75	return 0;
76}
77
78char _license[] SEC("license") = "GPL";