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

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Date:   Tue, 30 May 2023 14:31:33 +0200
From:   Andreas Schwab <schwab@...e.de>
To:     Willy Tarreau <w@....eu>
Cc:     Thomas Weißschuh <thomas@...ch.de>,
        Zhangjin Wu <falcon@...ylab.org>, arnd@...db.de,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH 1/2] selftests/nolibc: add new gettimeofday test cases

On Mai 30 2023, 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@...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.
>
> 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 :-/

The manual page is not part of glibc.  Neither the glibc documentation
nor the POSIX spec has ever supported NULL for the first argument.  The
generic POSIX implementation in glibc originally returned EINVAL for
that case, though.

-- 
Andreas Schwab, SUSE Labs, schwab@...e.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."