From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Martin KaFai Lau <kafai@fb.com>
Cc: Andrii Nakryiko <andriin@fb.com>, bpf <bpf@vger.kernel.org>,
Networking <netdev@vger.kernel.org>,
Alexei Starovoitov <ast@fb.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Kernel Team <kernel-team@fb.com>
Subject: Re: [Potential Spoof] [PATCH bpf-next] selftests/bpf: fix nanosleep for real this time
Date: Fri, 13 Mar 2020 17:10:29 -0700 [thread overview]
Message-ID: <CAEf4BzbKAz699qu0ae=A_8WryUXWywXDJm17d4ogp8x=oHXa_Q@mail.gmail.com> (raw)
In-Reply-To: <20200314000510.cmsepdhnywtglrcm@kafai-mbp>
On Fri, Mar 13, 2020 at 5:05 PM Martin KaFai Lau <kafai@fb.com> wrote:
>
> On Fri, Mar 13, 2020 at 04:35:35PM -0700, Andrii Nakryiko wrote:
> > Amazingly, some libc implementations don't call __NR_nanosleep syscall from
> > their nanosleep() APIs. Hammer it down with explicit syscall() call and never
> > get back to it again. Also simplify code for timespec initialization.
> >
> > I verified that nanosleep is called w/ printk and in exactly same Linux image
> > that is used in Travis CI. So it should both sleep and call correct syscall.
> >
> > Fixes: 4e1fd25d19e8 ("selftests/bpf: Fix usleep() implementation")
> > Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> > ---
> > tools/testing/selftests/bpf/test_progs.c | 16 ++++++----------
> > 1 file changed, 6 insertions(+), 10 deletions(-)
> >
> > diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
> > index f85a06512541..6956d722a463 100644
> > --- a/tools/testing/selftests/bpf/test_progs.c
> > +++ b/tools/testing/selftests/bpf/test_progs.c
> > @@ -35,16 +35,12 @@ struct prog_test_def {
> > */
> > int usleep(useconds_t usec)
> > {
> > - struct timespec ts;
> > -
> > - if (usec > 999999) {
> > - ts.tv_sec = usec / 1000000;
> > - ts.tv_nsec = usec % 1000000;
> > - } else {
> > - ts.tv_sec = 0;
> > - ts.tv_nsec = usec;
> > - }
> > - return nanosleep(&ts, NULL);
> > + struct timespec ts = {
> > + .tv_sec = usec / 1000000,
> > + .tv_nsec = usec % 1000000,
> usec is in micro and tv_nsec is in nano?
>
Yes, this is implementation of usleep() (microsecond sleep), so usec
is microseconds. We call nanosleep internally, though, which accepts
seconds and nanoseconds units. Did I mess up math here?
But either way, sending v2, there is another place we explicitly are
calling nanosleep as well, fixing that one as well.
> > + };
> > +
> > + return syscall(__NR_nanosleep, &ts, NULL);
> > }
> >
prev parent reply other threads:[~2020-03-14 0:10 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-13 23:35 [PATCH bpf-next] selftests/bpf: fix nanosleep for real this time Andrii Nakryiko
2020-03-14 0:05 ` [Potential Spoof] " Martin KaFai Lau
2020-03-14 0:10 ` Andrii Nakryiko [this message]
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