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From: Arnd Bergmann <arnd@arndb.de>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"open list:BROADCOM NVRAM DRIVER" <linux-mips@vger.kernel.org>,
	Paul Burton <paulburton@kernel.org>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Christian Brauner <christian.brauner@canonical.com>
Subject: Re: [PATCH] mips: vdso: conditionalize 32-bit time functions on COMPAT_32BIT_TIME
Date: Mon, 30 Dec 2019 16:47:37 +0100	[thread overview]
Message-ID: <CAK8P3a0NBuqDX63+920q7Q+yO2xCoSd0O7xUDJv6BBoco2kVOg@mail.gmail.com> (raw)
In-Reply-To: <CAHmME9pnBtjJ86gsWgK8DCYKo_HFpyViHoGpJPTrYBONT01YVA@mail.gmail.com>

On Mon, Dec 30, 2019 at 4:39 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>
> On Mon, Dec 30, 2019 at 4:37 PM Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > On Mon, Dec 30, 2019 at 3:37 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> > >
> > > On Mon, Dec 30, 2019 at 1:34 PM Arnd Bergmann <arnd@arndb.de> wrote:

> > Returning success from clock_gettime() on a kernel with only
> > time64 support and a libc with only time32 support (or vice
> > versa) would be a bug.
>
> Ah, right, hence why the 32-bit compat code is behind a
> still-on-by-default-but-not-for-long menu option.

I expect this to remain on-by-default for a rather long time, as we still
to run old binaries well into 2030s. Making it configurable is done for
two reasons:

- on embedded systems that have all user space built with time64,
  turning this off can make the kernel slightly smaller

- turning it off lets you check that no code relies on calling the old
  interfaces internally, bypassing the C library, in a way that works
  at the moment but may break after 2038.

         Arnd

  reply	other threads:[~2019-12-30 15:47 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-23 13:08 vdso-related userspace crashes on 5.5 mips64 Jason A. Donenfeld
2019-12-23 21:44 ` Jason A. Donenfeld
2019-12-23 23:29 ` Paul Burton
2019-12-24 13:37   ` Jason A. Donenfeld
2019-12-30 15:58     ` Arnd Bergmann
2019-12-24 14:19   ` Jason A. Donenfeld
2019-12-24 13:54 ` [PATCH] mips: vdso: conditionalize 32-bit time functions on COMPAT_32BIT_TIME Jason A. Donenfeld
2019-12-30 11:57   ` Arnd Bergmann
2019-12-30 12:26     ` Jason A. Donenfeld
2019-12-30 12:34       ` Arnd Bergmann
2019-12-30 14:37         ` Jason A. Donenfeld
2019-12-30 15:10           ` Jason A. Donenfeld
2019-12-30 15:37           ` Arnd Bergmann
2019-12-30 15:39             ` Jason A. Donenfeld
2019-12-30 15:47               ` Arnd Bergmann [this message]
2019-12-30 15:58                 ` Jason A. Donenfeld
2019-12-30 17:33                   ` Arnd Bergmann
2019-12-30 21:09                     ` Jason A. Donenfeld
2019-12-30 21:42                       ` Jason A. Donenfeld
2019-12-31 16:14                         ` Jason A. Donenfeld
2020-01-01  4:10                           ` Paul Burton
2020-01-01  4:25                             ` Paul Burton
2020-01-01  9:47                               ` Jason A. Donenfeld
2020-01-01  9:47                             ` Jason A. Donenfeld

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