linux-kernel - Re: [Ksummit-discuss] 2038 Kernel Summit Discussion Fodder

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Message-ID: <55FCA686.601@zytor.com>
Date:	Fri, 18 Sep 2015 17:04:22 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Arnd Bergmann <arnd@...db.de>,
	ksummit-discuss@...ts.linuxfoundation.org
Cc:	Ben Hutchings <ben@...adent.org.uk>,
	John Stultz <john.stultz@...aro.org>,
	"Joseph S. Myers" <joseph@...esourcery.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [Ksummit-discuss] 2038 Kernel Summit Discussion Fodder

On 08/13/2014 01:06 PM, Arnd Bergmann wrote:
> On Wednesday 13 August 2014 03:06:53 Ben Hutchings wrote:
>>> On the kernel side, it also adds more complexity, where we have to add
>>> even more complex compat support for 64bit systems to handle all the
>>> various 32bit applications possible.
>> [...]
>>
>> Didn't we need to do this already to support x32?  Have compat ioctls
>> involving time been botched?
> 
> AFAICT, every ioctl that involves passing a __kernel_ulong_t or
> __kernel_ulong_t is potentially broken on x32, and this includes
> everything passing a time_t or timespec.
> 
> The problem is that the libc ioctl() function ends up in the kernel's
> compat_ioctl handler, which expects the 32-bit ABI, not the 64-bit ABI.
> Most other syscalls in x32 however use the 64-bit ABI.
> 
> It works only for drivers that use the same function for .ioctl and
> .compat_ioctl, and that encode the size of the data structure correctly
> in the ioctl command code. I assume this is how we will do it for all
> 32-bit architectures with 64-bit time_t, but on x32 it also concerns
> other types that use __kernel_long_t.
> 

OK, super-late reply.

Actually we have by and large dealt with that.  Sadly this meant an
increase in the number of paths with conditional ABI.

	-hpa


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