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