1/* Copyright (c) 2016 Facebook
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 */
7#include <uapi/linux/bpf.h>
8#include <uapi/linux/ptrace.h>
9#include <uapi/linux/perf_event.h>
10#include <linux/version.h>
11#include <linux/sched.h>
12#include <bpf/bpf_helpers.h>
13#include <bpf/bpf_tracing.h>
14
15#define _(P)                                                                   \
16	({                                                                     \
17		typeof(P) val;                                                 \
18		bpf_probe_read_kernel(&val, sizeof(val), &(P));                \
19		val;                                                           \
20	})
21
22#define MINBLOCK_US	1
23
24struct key_t {
25	char waker[TASK_COMM_LEN];
26	char target[TASK_COMM_LEN];
27	u32 wret;
28	u32 tret;
29};
30
31struct {
32	__uint(type, BPF_MAP_TYPE_HASH);
33	__type(key, struct key_t);
34	__type(value, u64);
35	__uint(max_entries, 10000);
36} counts SEC(".maps");
37
38struct {
39	__uint(type, BPF_MAP_TYPE_HASH);
40	__type(key, u32);
41	__type(value, u64);
42	__uint(max_entries, 10000);
43} start SEC(".maps");
44
45struct wokeby_t {
46	char name[TASK_COMM_LEN];
47	u32 ret;
48};
49
50struct {
51	__uint(type, BPF_MAP_TYPE_HASH);
52	__type(key, u32);
53	__type(value, struct wokeby_t);
54	__uint(max_entries, 10000);
55} wokeby SEC(".maps");
56
57struct {
58	__uint(type, BPF_MAP_TYPE_STACK_TRACE);
59	__uint(key_size, sizeof(u32));
60	__uint(value_size, PERF_MAX_STACK_DEPTH * sizeof(u64));
61	__uint(max_entries, 10000);
62} stackmap SEC(".maps");
63
64#define STACKID_FLAGS (0 | BPF_F_FAST_STACK_CMP)
65
66SEC("kprobe/try_to_wake_up")
67int waker(struct pt_regs *ctx)
68{
69	struct task_struct *p = (void *) PT_REGS_PARM1(ctx);
70	struct wokeby_t woke;
71	u32 pid;
72
73	pid = _(p->pid);
74
75	bpf_get_current_comm(&woke.name, sizeof(woke.name));
76	woke.ret = bpf_get_stackid(ctx, &stackmap, STACKID_FLAGS);
77
78	bpf_map_update_elem(&wokeby, &pid, &woke, BPF_ANY);
79	return 0;
80}
81
82static inline int update_counts(void *ctx, u32 pid, u64 delta)
83{
84	struct wokeby_t *woke;
85	u64 zero = 0, *val;
86	struct key_t key;
87
88	__builtin_memset(&key.waker, 0, sizeof(key.waker));
89	bpf_get_current_comm(&key.target, sizeof(key.target));
90	key.tret = bpf_get_stackid(ctx, &stackmap, STACKID_FLAGS);
91	key.wret = 0;
92
93	woke = bpf_map_lookup_elem(&wokeby, &pid);
94	if (woke) {
95		key.wret = woke->ret;
96		__builtin_memcpy(&key.waker, woke->name, sizeof(key.waker));
97		bpf_map_delete_elem(&wokeby, &pid);
98	}
99
100	val = bpf_map_lookup_elem(&counts, &key);
101	if (!val) {
102		bpf_map_update_elem(&counts, &key, &zero, BPF_NOEXIST);
103		val = bpf_map_lookup_elem(&counts, &key);
104		if (!val)
105			return 0;
106	}
107	(*val) += delta;
108	return 0;
109}
110
111#if 1
112/* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
113struct sched_switch_args {
114	unsigned long long pad;
115	char prev_comm[16];
116	int prev_pid;
117	int prev_prio;
118	long long prev_state;
119	char next_comm[16];
120	int next_pid;
121	int next_prio;
122};
123SEC("tracepoint/sched/sched_switch")
124int oncpu(struct sched_switch_args *ctx)
125{
126	/* record previous thread sleep time */
127	u32 pid = ctx->prev_pid;
128#else
129SEC("kprobe/finish_task_switch")
130int oncpu(struct pt_regs *ctx)
131{
132	struct task_struct *p = (void *) PT_REGS_PARM1(ctx);
133	/* record previous thread sleep time */
134	u32 pid = _(p->pid);
135#endif
136	u64 delta, ts, *tsp;
137
138	ts = bpf_ktime_get_ns();
139	bpf_map_update_elem(&start, &pid, &ts, BPF_ANY);
140
141	/* calculate current thread's delta time */
142	pid = bpf_get_current_pid_tgid();
143	tsp = bpf_map_lookup_elem(&start, &pid);
144	if (!tsp)
145		/* missed start or filtered */
146		return 0;
147
148	delta = bpf_ktime_get_ns() - *tsp;
149	bpf_map_delete_elem(&start, &pid);
150	delta = delta / 1000;
151	if (delta < MINBLOCK_US)
152		return 0;
153
154	return update_counts(ctx, pid, delta);
155}
156char _license[] SEC("license") = "GPL";
157u32 _version SEC("version") = LINUX_VERSION_CODE;
158