old_contents: #!/usr/bin/python
  #
  # urandomread-explicit  Example of instrumenting a kernel tracepoint.
  #                       For Linux, uses BCC, BPF. Embedded C.
  #
  # This is an older example of instrumenting a tracepoint, which defines
  # the argument struct and makes an explicit call to attach_tracepoint().
  # See urandomread for a newer version that uses TRACEPOINT_PROBE().
  #
  # REQUIRES: Linux 4.7+ (BPF_PROG_TYPE_TRACEPOINT support).
  #
  # Test by running this, then in another shell, run:
  #     dd if=/dev/urandom of=/dev/null bs=1k count=5
  #
  # Copyright 2016 Netflix, Inc.
  # Licensed under the Apache License, Version 2.0 (the "License")
  
  from __future__ import print_function
  from bcc import BPF
  
  # define BPF program
  bpf_text = """
  #include <uapi/linux/ptrace.h>
  
  struct urandom_read_args {
      // from /sys/kernel/debug/tracing/events/random/urandom_read/format
      u64 __unused__;
      u32 got_bits;
      u32 pool_left;
      u32 input_left;
  };
  
  int printarg(struct urandom_read_args *args) {
      bpf_trace_printk("%d\\n", args->got_bits);
      return 0;
  };
  """
  
  # load BPF program
  b = BPF(text=bpf_text)
  b.attach_tracepoint("random:urandom_read", "printarg")
  
  # header
  print("%-18s %-16s %-6s %s" % ("TIME(s)", "COMM", "PID", "GOTBITS"))
  
  # format output
  while 1:
      try:
          (task, pid, cpu, flags, ts, msg) = b.trace_fields()
      except ValueError:
          continue
      print("%-18.9f %-16s %-6d %s" % (ts, task, pid, msg))
  
new_contents: #!/usr/bin/python
  #
  # urandomread-explicit  Example of instrumenting a kernel tracepoint.
  #                       For Linux, uses BCC, BPF. Embedded C.
  #
  # This is an older example of instrumenting a tracepoint, which defines
  # the argument struct and makes an explicit call to attach_tracepoint().
  # See urandomread for a newer version that uses TRACEPOINT_PROBE().
  #
  # REQUIRES: Linux 4.7+ (BPF_PROG_TYPE_TRACEPOINT support).
  #
  # Test by running this, then in another shell, run:
  #     dd if=/dev/urandom of=/dev/null bs=1k count=5
  #
  # Copyright 2016 Netflix, Inc.
  # Licensed under the Apache License, Version 2.0 (the "License")
  
  from __future__ import print_function
  from bcc import BPF
  
  # define BPF program
  bpf_text = """
  #include <uapi/linux/ptrace.h>
  
  struct urandom_read_args {
      // from /sys/kernel/debug/tracing/events/random/urandom_read/format
      u64 __unused__;
      u32 got_bits;
      u32 pool_left;
      u32 input_left;
  };
  
  int printarg(struct urandom_read_args *args) {
      bpf_trace_printk("%d\\n", args->got_bits);
      return 0;
  };
  """
  
  # load BPF program
  b = BPF(text=bpf_text)
  b.attach_tracepoint(tp="random:urandom_read", fn_name="printarg")
  
  # header
  print("%-18s %-16s %-6s %s" % ("TIME(s)", "COMM", "PID", "GOTBITS"))
  
  # format output
  while 1:
      try:
          (task, pid, cpu, flags, ts, msg) = b.trace_fields()
      except ValueError:
          continue
      print("%-18.9f %-16s %-6d %s" % (ts, task, pid, msg))
  
subject: Fix Tracepoint example (#809)