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 
21 struct {
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 
28 SEC("kprobe/trace_preempt_off")
bpf_prog1(struct pt_regs * ctx)29 int 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 
log2(unsigned int v)40 static 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 
log2l(unsigned long v)54 static 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 
64 struct {
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 
71 SEC("kprobe/trace_preempt_on")
bpf_prog2(struct pt_regs * ctx)72 int 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 
98 char _license[] SEC("license") = "GPL";
99 u32 _version SEC("version") = LINUX_VERSION_CODE;
100