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.h>
43
44 int probe(hrtimer_nanosleep, rqtp->tv_sec)(void *ctx, int err, long sec)
45 {
46 return sec == 5;
47 }
48
49 license(GPL);