LXR linux/tools/perf/examples/bpf/5sec.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3    Description:
   4
   5    . Disable strace like syscall tracing (--no-syscalls), or try tracing
   6      just some (-e *sleep).
   7
   8    . Attach a filter function to a kernel function, returning when it should
   9      be considered, i.e. appear on the output.
  10
  11    . Run it system wide, so that any sleep of >= 5 seconds and < than 6
  12      seconds gets caught.
  13
  14    . Ask for callgraphs using DWARF info, so that userspace can be unwound
  15
  16    . While this is running, run something like "sleep 5s".
  17
  18    . If we decide to add tv_nsec as well, then it becomes:
  19
  20      int probe(hrtimer_nanosleep, rqtp->tv_sec rqtp->tv_nsec)(void *ctx, int err, long sec, long nsec)
  21
  22      I.e. add where it comes from (rqtp->tv_nsec) and where it will be
  23      accessible in the function body (nsec)
  24
  25    # perf trace --no-syscalls -e tools/perf/examples/bpf/5sec.c/call-graph=dwarf/
  26         0.000 perf_bpf_probe:func:(ffffffff9811b5f0) tv_sec=5
  27                                           hrtimer_nanosleep ([kernel.kallsyms])
  28                                           __x64_sys_nanosleep ([kernel.kallsyms])
  29                                           do_syscall_64 ([kernel.kallsyms])
  30                                           entry_SYSCALL_64 ([kernel.kallsyms])
  31                                           __GI___nanosleep (/usr/lib64/libc-2.26.so)
  32                                           rpl_nanosleep (/usr/bin/sleep)
  33                                           xnanosleep (/usr/bin/sleep)
  34                                           main (/usr/bin/sleep)
  35                                           __libc_start_main (/usr/lib64/libc-2.26.so)
  36                                           _start (/usr/bin/sleep)
  37    ^C#
  38
  39   Copyright (C) 2018 Red Hat, Inc., Arnaldo Carvalho de Melo <acme@redhat.com>
  40*/
  41
  42#include <bpf/bpf.h>
  43
  44#define NSEC_PER_SEC    1000000000L
  45
  46int probe(hrtimer_nanosleep, rqtp)(void *ctx, int err, long long sec)
  47{
  48        return sec / NSEC_PER_SEC == 5ULL;
  49}
  50
  51license(GPL);
  52