Re: [PATCH 1/2] selftests/nolibc: add new gettimeofday test cases

From: "Thomas Weißschuh" <thomas@t-8ch.de>
To: Willy Tarreau <w@1wt.eu>
Cc: Zhangjin Wu <falcon@tinylab.org>,
	arnd@arndb.de,  linux-kernel@vger.kernel.org,
	linux-kselftest@vger.kernel.org, linux-riscv@lists.infradead.org
Subject: Re: [PATCH 1/2] selftests/nolibc: add new gettimeofday test cases
Date: Tue, 30 May 2023 14:35:55 +0200	[thread overview]
Message-ID: <280867a8-7601-4a96-9b85-87668e1f1282@t-8ch.de> (raw)
In-Reply-To: <ZHXmbNg4BdJNd4cO@1wt.eu>

On 2023-05-30 14:05:00+0200, Willy Tarreau wrote:
> On Tue, May 30, 2023 at 12:59:31PM +0200, Thomas Weißschuh wrote:
> > On 2023-05-30 14:37:49+0800, Zhangjin Wu wrote:
> > > These 3 test cases are added to cover the normal using scenes of
> > > gettimeofday().
> > > 
> > > They have been used to trigger and fix up such issue:
> > > 
> > >     nolibc-test.c:(.text.gettimeofday+0x54): undefined reference to `__aeabi_ldivmod'
> > > 
> > > This issue happens while there is no "unsigned int" conversion in the
> > > new clock_gettime / clock_gettime64 syscall path of gettimeofday():
> > > 
> > >     tv->tv_usec = ts.tv_nsec / 1000;
> > > 
> > > Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
> > > ---
> > >  tools/testing/selftests/nolibc/nolibc-test.c | 5 +++++
> > >  1 file changed, 5 insertions(+)
> > > 
> > > diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
> > > index 8ba8c2fc71a0..20d184da9a2b 100644
> > > --- a/tools/testing/selftests/nolibc/nolibc-test.c
> > > +++ b/tools/testing/selftests/nolibc/nolibc-test.c
> > > @@ -533,6 +533,8 @@ static int test_stat_timestamps(void)
> > >   */
> > >  int run_syscall(int min, int max)
> > >  {
> > > +	struct timeval tv;
> > > +	struct timezone tz;
> > >  	struct stat stat_buf;
> > >  	int euid0;
> > >  	int proc;
> > > @@ -588,6 +590,9 @@ int run_syscall(int min, int max)
> > >  		CASE_TEST(getdents64_root);   EXPECT_SYSNE(1, test_getdents64("/"), -1); break;
> > >  		CASE_TEST(getdents64_null);   EXPECT_SYSER(1, test_getdents64("/dev/null"), -1, ENOTDIR); break;
> > >  		CASE_TEST(gettimeofday_null); EXPECT_SYSZR(1, gettimeofday(NULL, NULL)); break;
> > > +		CASE_TEST(gettimeofday_tv);   EXPECT_SYSZR(1, gettimeofday(&tv, NULL)); break;
> > > +		CASE_TEST(gettimeofday_tz);   EXPECT_SYSZR(1, gettimeofday(NULL, &tz)); break;
> > 
> > Calling gettimeofday(NULL, ...) will actually segfault on glibc.
> > It works when calling through the VDSO, but not the logic in glibc
> > itself, which is guess is allowed by POSIX.
> 
> Then that's shocking, because the man page says:
> 
>        If either tv or tz is NULL, the corresponding structure is not  set  or
>        returned.   (However, compilation warnings will result if tv is NULL.)
> 
> I'd expect glibc to at least support what'd documented in the man
> page :-/

That is gettimeofday(2), which comes from the Linux man-pages project.

gettimeofday(3p) which specifies the posix function does not have that wording.
It also specifies that there is no way to indicate errors...

Seems to be a weird situation.

> > I propose to avoid doing it :-)
> 
> If you're certain that's the case, then I agree.
> 
> > Either we gate the existing test in #ifdef NOLIBC or we remove it.
> 
> Better not keep tests specific to nolibc if they aim at verifying some
> compatibliity.

Thomas

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