/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com * Copyright (c) 2015 BMW Car IT GmbH * * This program is free software; you can redistribute it and/or * modify it under the terms of version 2 of the GNU General Public * License as published by the Free Software Foundation. */ #include <linux/version.h> #include <linux/ptrace.h> #include <uapi/linux/bpf.h> #include <bpf/bpf_helpers.h> #define MAX_ENTRIES 20 #define MAX_CPU 4 /* We need to stick to static allocated memory (an array instead of * hash table) because managing dynamic memory from the * trace_preempt_[on|off] tracepoints hooks is not supported. */ struct { __uint(type, BPF_MAP_TYPE_ARRAY); __type(key, int); __type(value, u64); __uint(max_entries, MAX_CPU); } my_map SEC(".maps"); SEC("kprobe/trace_preempt_off") int bpf_prog1(struct pt_regs *ctx) { int cpu = bpf_get_smp_processor_id(); u64 *ts = bpf_map_lookup_elem(&my_map, &cpu); if (ts) *ts = bpf_ktime_get_ns(); return 0; } static unsigned int log2(unsigned int v) { unsigned int r; unsigned int shift; r = (v > 0xFFFF) << 4; v >>= r; shift = (v > 0xFF) << 3; v >>= shift; r |= shift; shift = (v > 0xF) << 2; v >>= shift; r |= shift; shift = (v > 0x3) << 1; v >>= shift; r |= shift; r |= (v >> 1); return r; } static unsigned int log2l(unsigned long v) { unsigned int hi = v >> 32; if (hi) return log2(hi) + 32; else return log2(v); } struct { __uint(type, BPF_MAP_TYPE_ARRAY); __type(key, int); __type(value, long); __uint(max_entries, MAX_CPU * MAX_ENTRIES); } my_lat SEC(".maps"); SEC("kprobe/trace_preempt_on") int bpf_prog2(struct pt_regs *ctx) { u64 *ts, cur_ts, delta; int key, cpu; long *val; cpu = bpf_get_smp_processor_id(); ts = bpf_map_lookup_elem(&my_map, &cpu); if (!ts) return 0; cur_ts = bpf_ktime_get_ns(); delta = log2l(cur_ts - *ts); if (delta > MAX_ENTRIES - 1) delta = MAX_ENTRIES - 1; key = cpu * MAX_ENTRIES + delta; val = bpf_map_lookup_elem(&my_lat, &key); if (val) __sync_fetch_and_add((long *)val, 1); return 0; } char _license[] SEC("license") = "GPL"; u32 _version SEC("version") = LINUX_VERSION_CODE;