| Daniel Wagner | 0fb1170 | 2015-06-19 16:00:44 +0200 | [diff] [blame] | 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") |
| 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(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") |
| 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; |