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_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 bpf_map_def SEC("maps") my_map = {
22 .type = BPF_MAP_TYPE_ARRAY,
23 .key_size = sizeof(int),
24 .value_size = sizeof(u64),
25 .max_entries = MAX_CPU,
26 };
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 bpf_map_def SEC("maps") my_lat = {
65 .type = BPF_MAP_TYPE_ARRAY,
66 .key_size = sizeof(int),
67 .value_size = sizeof(long),
68 .max_entries = MAX_CPU * MAX_ENTRIES,
69 };
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
