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);