Eric Lee / smarc-fsl-linux-kernel

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samples/bpf/lathist_kern.c 2.09 KB
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0fb1170ee   Daniel Wagner   bpf: BPF based la... 
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  /* 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>
7cf245a37   Toke Høiland-Jørgensen   samples/bpf: Use ... 
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  #include <bpf/bpf_helpers.h>
0fb1170ee   Daniel Wagner   bpf: BPF based la... 
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  #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.
   */
3677d0a13   Daniel T. Lee   samples: bpf: Ref... 
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  struct {
  	__uint(type, BPF_MAP_TYPE_ARRAY);
  	__type(key, int);
  	__type(value, u64);
  	__uint(max_entries, MAX_CPU);
  } my_map SEC(".maps");
0fb1170ee   Daniel Wagner   bpf: BPF based la... 
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  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);
  }
3677d0a13   Daniel T. Lee   samples: bpf: Ref... 
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  struct {
  	__uint(type, BPF_MAP_TYPE_ARRAY);
  	__type(key, int);
  	__type(value, long);
  	__uint(max_entries, MAX_CPU * MAX_ENTRIES);
  } my_lat SEC(".maps");
0fb1170ee   Daniel Wagner   bpf: BPF based la... 
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  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;