examples/bpf/5sec.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003     Description:
0004
0005     . Disable strace like syscall tracing (--no-syscalls), or try tracing
0006       just some (-e *sleep).
0007
0008     . Attach a filter function to a kernel function, returning when it should
0009       be considered, i.e. appear on the output.
0010
0011     . Run it system wide, so that any sleep of >= 5 seconds and < than 6
0012       seconds gets caught.
0013
0014     . Ask for callgraphs using DWARF info, so that userspace can be unwound
0015
0016     . While this is running, run something like "sleep 5s".
0017
0018     . If we decide to add tv_nsec as well, then it becomes:
0019
0020       int probe(hrtimer_nanosleep, rqtp->tv_sec rqtp->tv_nsec)(void *ctx, int err, long sec, long nsec)
0021
0022       I.e. add where it comes from (rqtp->tv_nsec) and where it will be
0023       accessible in the function body (nsec)
0024
0025     # perf trace --no-syscalls -e tools/perf/examples/bpf/5sec.c/call-graph=dwarf/
0026          0.000 perf_bpf_probe:func:(ffffffff9811b5f0) tv_sec=5
0027                                            hrtimer_nanosleep ([kernel.kallsyms])
0028                                            __x64_sys_nanosleep ([kernel.kallsyms])
0029                                            do_syscall_64 ([kernel.kallsyms])
0030                                            entry_SYSCALL_64 ([kernel.kallsyms])
0031                                            __GI___nanosleep (/usr/lib64/libc-2.26.so)
0032                                            rpl_nanosleep (/usr/bin/sleep)
0033                                            xnanosleep (/usr/bin/sleep)
0034                                            main (/usr/bin/sleep)
0035                                            __libc_start_main (/usr/lib64/libc-2.26.so)
0036                                            _start (/usr/bin/sleep)
0037     ^C#
0038
0039    Copyright (C) 2018 Red Hat, Inc., Arnaldo Carvalho de Melo <acme@redhat.com>
0040 */
0041
0042 #include <bpf.h>
0043
0044 #define NSEC_PER_SEC    1000000000L
0045
0046 int probe(hrtimer_nanosleep, rqtp)(void *ctx, int err, long long sec)
0047 {
0048     return sec / NSEC_PER_SEC == 5ULL;
0049 }
0050
0051 license(GPL);