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1/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com2 * Copyright (c) 2015 BMW Car IT GmbH3 *4 * This program is free software; you can redistribute it and/or5 * modify it under the terms of version 2 of the GNU General Public6 * 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 2014#define MAX_CPU 415 16/* We need to stick to static allocated memory (an array instead of17 * hash table) because managing dynamic memory from the18 * 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 else61 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;100