1/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
 2 * Copyright (c) 2015 BMW Car IT GmbH
 3 *
 4 * This program is free software; you can redistribute it and/or
 5 * modify it under the terms of version 2 of the GNU General Public
 6 * License as published by the Free Software Foundation.
 7 */
 8#include <linux/version.h>
 9#include <linux/ptrace.h>
10#include <uapi/linux/bpf.h>
11#include <bpf/bpf_helpers.h>
12
13#define MAX_ENTRIES	20
14#define MAX_CPU		4
15
16/* We need to stick to static allocated memory (an array instead of
17 * hash table) because managing dynamic memory from the
18 * trace_preempt_[on|off] tracepoints hooks is not supported.
19 */
20
21struct {
22	__uint(type, BPF_MAP_TYPE_ARRAY);
23	__type(key, int);
24	__type(value, u64);
25	__uint(max_entries, MAX_CPU);
26} my_map SEC(".maps");
27
28SEC("kprobe/trace_preempt_off")
29int bpf_prog1(struct pt_regs *ctx)
30{
31	int cpu = bpf_get_smp_processor_id();
32	u64 *ts = bpf_map_lookup_elem(&my_map, &cpu);
33
34	if (ts)
35		*ts = bpf_ktime_get_ns();
36
37	return 0;
38}
39
40static unsigned int log2(unsigned int v)
41{
42	unsigned int r;
43	unsigned int shift;
44
45	r = (v > 0xFFFF) << 4; v >>= r;
46	shift = (v > 0xFF) << 3; v >>= shift; r |= shift;
47	shift = (v > 0xF) << 2; v >>= shift; r |= shift;
48	shift = (v > 0x3) << 1; v >>= shift; r |= shift;
49	r |= (v >> 1);
50
51	return r;
52}
53
54static unsigned int log2l(unsigned long v)
55{
56	unsigned int hi = v >> 32;
57
58	if (hi)
59		return log2(hi) + 32;
60	else
61		return log2(v);
62}
63
64struct {
65	__uint(type, BPF_MAP_TYPE_ARRAY);
66	__type(key, int);
67	__type(value, long);
68	__uint(max_entries, MAX_CPU * MAX_ENTRIES);
69} my_lat SEC(".maps");
70
71SEC("kprobe/trace_preempt_on")
72int bpf_prog2(struct pt_regs *ctx)
73{
74	u64 *ts, cur_ts, delta;
75	int key, cpu;
76	long *val;
77
78	cpu = bpf_get_smp_processor_id();
79	ts = bpf_map_lookup_elem(&my_map, &cpu);
80	if (!ts)
81		return 0;
82
83	cur_ts = bpf_ktime_get_ns();
84	delta = log2l(cur_ts - *ts);
85
86	if (delta > MAX_ENTRIES - 1)
87		delta = MAX_ENTRIES - 1;
88
89	key = cpu * MAX_ENTRIES + delta;
90	val = bpf_map_lookup_elem(&my_lat, &key);
91	if (val)
92		__sync_fetch_and_add((long *)val, 1);
93
94	return 0;
95
96}
97
98char _license[] SEC("license") = "GPL";
99u32 _version SEC("version") = LINUX_VERSION_CODE;