linux-kernel - Re: [PATCH 11/23] y2038: rusage: use __kernel_old

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Message-ID: <20191112210915.GD5130@uranus>
Date:   Wed, 13 Nov 2019 00:09:15 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     y2038@...ts.linaro.org, Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>, linux-kernel@...r.kernel.org,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>,
        Michal Koutný <mkoutny@...e.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-alpha@...r.kernel.org
Subject: Re: [PATCH 11/23] y2038: rusage: use __kernel_old_timeval

On Fri, Nov 08, 2019 at 10:12:10PM +0100, Arnd Bergmann wrote:
> There are two 'struct timeval' fields in 'struct rusage'.
> 
> Unfortunately the definition of timeval is now ambiguous when used in
> user space with a libc that has a 64-bit time_t, and this also changes
> the 'rusage' definition in user space in a way that is incompatible with
> the system call interface.
> 
> While there is no good solution to avoid all ambiguity here, change
> the definition in the kernel headers to be compatible with the kernel
> ABI, using __kernel_old_timeval as an unambiguous base type.
> 
> In previous discussions, there was also a plan to add a replacement
> for rusage based on 64-bit timestamps and nanosecond resolution,
> i.e. 'struct __kernel_timespec'. I have patches for that as well,
> if anyone thinks we should do that.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> Question: should we also rename 'struct rusage' into 'struct __kernel_rusage'
> here, to make them completely unambiguous?

The patch looks ok to me. I must confess I looked into rusage long ago
so __kernel_timespec type used in uapi made me nervious at first,
but then i found that we've this type defined in time_types.h uapi
so userspace should be safe. I also like the idea of __kernel_rusage
but definitely on top of the series.

Reviewed-by: Cyrill Gorcunov <gorcunov@...il.com>