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

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Message-Id: <20230530112806.404017-1-falcon@tinylab.org>
Date:   Tue, 30 May 2023 19:28:06 +0800
From:   Zhangjin Wu <falcon@...ylab.org>
To:     thomas@...ch.de
Cc:     arnd@...db.de, falcon@...ylab.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-riscv@...ts.infradead.org,
        w@....eu
Subject: Re: [PATCH 1/2] selftests/nolibc: add new gettimeofday test cases

> 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@...ylab.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.
>

In low level gettimeofday syscall, it should be ok, will check the non-vdso
code of glibc later. in musl, it returns 0 when it is NULL
(src/time/gettimeofday.c).

> I propose to avoid doing it :-)

Just checked it again, these two cases can also detect the issues (1):

    CASE_TEST(gettimeofday_tv);   EXPECT_SYSZR(1, gettimeofday(&tv, NULL)); break;
    CASE_TEST(gettimeofday_tv_tz);EXPECT_SYSZR(1, gettimeofday(&tv, &tz)); break;

    (1) nolibc-test.c:(.text.gettimeofday+0x54): undefined reference to `__aeabi_ldivmod'

we can directly remove the second one ;-)

> 
> Either we gate the existing test in #ifdef NOLIBC or we remove it.

so, we still need to check the original gettimeofday_null test case for glibc?

Thanks,
Zhangjin

> 
> > +		CASE_TEST(gettimeofday_tv_tz);EXPECT_SYSZR(1, gettimeofday(&tv, &tz)); break;
> >  		CASE_TEST(getpagesize);       EXPECT_SYSZR(1, test_getpagesize()); break;
> >  		CASE_TEST(ioctl_tiocinq);     EXPECT_SYSZR(1, ioctl(0, TIOCINQ, &tmp)); break;
> >  		CASE_TEST(ioctl_tiocinq);     EXPECT_SYSZR(1, ioctl(0, TIOCINQ, &tmp)); break;