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
  46 int probe(hrtimer_nanosleep, rqtp)(void *ctx, int err, long long sec)
  47 {
  48         return sec / NSEC_PER_SEC == 5ULL;
  49 }
  50
  51 license(GPL);