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

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Date:   Tue, 30 May 2023 12:59:31 +0200
From:   Thomas Weißschuh <thomas@...ch.de>
To:     Zhangjin Wu <falcon@...ylab.org>
Cc:     w@....eu, 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 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.

I propose to avoid doing it :-)

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

> +		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;
> -- 
> 2.25.1
>