linux-kernel - Re: [PATCH 3/6] y2038: linux: Provide __clock

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Message-ID: <20190420002009.l65upn2t3qqoj5uy@sghpc.golosunov.pp.ru>
Date:   Sat, 20 Apr 2019 04:20:10 +0400
From:   Stepan Golosunov <stepan@...osunov.pp.ru>
To:     Lukasz Majewski <lukma@...x.de>, Arnd Bergmann <arnd@...db.de>,
        Deepa Dinamani <deepa.kernel@...il.com>
Cc:     libc-alpha@...rceware.org, Paul Eggert <eggert@...ucla.edu>,
        Joseph Myers <joseph@...esourcery.com>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] y2038: linux: Provide __clock_settime64
 implementation

15.04.2019 в 00:08:38 +0200 Lukasz Majewski написал:
> +# if defined __NR_clock_settime64
> +  /* Make sure that passed __timespec64 struct pad is 0.  */
> +  struct __timespec64 ts = *tp;
> +  ts.tv_pad = 0;
> +  return INLINE_SYSCALL_CALL (clock_settime64, clock_id, &ts);

Isn't kernel supposed to zero out padding on its own?
At least comment in kernel's get_timespec64 says so:

	/* Zero out the padding for 32 bit systems or in compat mode */
	if (IS_ENABLED(CONFIG_64BIT_TIME) && in_compat_syscall())
		kts.tv_nsec &= 0xFFFFFFFFUL;

The code looks buggy though. It fails to zero out the padding in
32-bit kernels. That part is probably broken since
98f76206b3350 ("compat: Cleanup in_compat_syscall() callers").

And, hmm, is CONFIG_64BIT_TIME enabled anywhere?