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" ) |
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 | |
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 | |
54 | static unsigned int log2l(unsigned long v) |
55 | { |
56 | unsigned int hi = v >> 32; |
57 | |
58 | if (hi) |
59 | return log2(v: 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" ) |
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 | |