linux-kernel - Re: [RFC PATCH v2 03/11] time: Add rtc_tm_to_time64() safe version(using time64

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Date:	Thu, 30 Oct 2014 14:55:13 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"pang.xunlei" <pang.xunlei@...aro.org>
cc:	linux-kernel@...r.kernel.org, rtc-linux@...glegroups.com,
	xen-devel@...ts.xenproject.org,
	John Stultz <john.stultz@...aro.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>
Subject: Re: [RFC PATCH v2 03/11] time: Add rtc_tm_to_time64() safe version(using
 time64_t)

On Thu, 30 Oct 2014, pang.xunlei wrote:

Same $subject issue.

> As part of addressing 2038 saftey for in-kernel uses, this patch
> adds safe rtc_tm_to_time64() using time64_t. After this patch,
> rtc_tm_to_time() should be replaced by rtc_tm_to_time64() one by
> one. Eventually, rtc_tm_to_time() will be removed from the kernel
> when it has no users.
> 
> Signed-off-by: pang.xunlei <pang.xunlei@...aro.org>
> ---
>  drivers/rtc/rtc-lib.c |   15 ++++++++++++++-
>  include/linux/rtc.h   |    1 +
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/rtc/rtc-lib.c b/drivers/rtc/rtc-lib.c
> index c4cf057..6948cbd 100644
> --- a/drivers/rtc/rtc-lib.c
> +++ b/drivers/rtc/rtc-lib.c
> @@ -110,10 +110,23 @@ EXPORT_SYMBOL(rtc_valid_tm);
>  
>  /*
>   * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
> + * Safe version for 2038 safety.

Docbook comment missing. See the previous replies.

> + */
> +int rtc_tm_to_time64(struct rtc_time *tm, time64_t *time)

What's the point of the return value? Just because rtc_tm_to_time()
has one? 

Yes it does, but that does not mean that we blindly copy the existing
nonsense when we implement a replacement interface.

What's wrong with changing it to:

time64_t rtc_tm_to_time64(struct rtc_time *tm)
{
	return mktime64(......);
}

> +/*
> + * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
> + * TODO: [2038 safety] should be replaced by rtc_tm_to_time64.

Groan.

>   */
>  int rtc_tm_to_time(struct rtc_time *tm, unsigned long *time)
>  {
> -       *time = mktime(tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
> +       *time = (unsigned long) mktime64(tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
>                         tm->tm_hour, tm->tm_min, tm->tm_sec);

And that would become

    	 *time = rtc_time_to_time64(tm);

>         return 0;
>  }

Please stop doing purely mechanical changes. Just blindly copying
stuff and make it take time64_t instead of unsigned long can be done
with a script as well.

Thanks,

	tglx
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