From: Arnd Bergmann <arnd@arndb.de>
To: Andreas Schwab <schwab@suse.de>
Cc: linux-arm-kernel@lists.infradead.org,
        Yury Norov <ynorov@caviumnetworks.com>, pinskia@gmail.com,
        Prasun.Kapoor@caviumnetworks.com, catalin.marinas@arm.com,
        Nathan_Lynch@mentor.com, linux-kernel@vger.kernel.org, agraf@suse.de,
        klimov.linux@gmail.com,
        Andrew Pinski <Andrew.Pinski@caviumnetworks.com>, broonie@kernel.org,
        jan.dakinevich@gmail.com, Andrew Pinski <apinski@cavium.com>,
        ddaney.cavm@gmail.com, bamvor.zhangjian@huawei.com,
        philipp.tomsich@theobroma-systems.com, andrey.konovalov@linaro.org,
        christoph.muellner@theobroma-systems.com
Subject: Re: [PATCH v6 13/17] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it
Date: Thu, 12 Nov 2015 14:24:57 +0100
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On Thursday 12 November 2015 10:44:55 Andreas Schwab wrote:
> Arnd Bergmann <arnd@arndb.de> writes:
> 
> > What do you mean with 32-bit off_t?
> 
> An ABI with 32-bit off_t, ie. all currently implemented 32-bit ABIs.
> 
> > Do you mean that glibc emulates a 32-bit off_t on top of the 64-bit
> > __kernel_loff_t?
> 
> Glibc is bridging the user-space ABI to the kernel ABI.

Ok, but why?

The kernel headers for all recent architectures (arc, c6x, h8300,
hexagon, metag, nios2, openrisc, tile and unicore32) deliberately
leave out the __kernel_off_t based system calls to simplify the
ABI in a way that we never have to support a 32-bit off_t
in user space.

Are there programs that require using a 32-bit off_t by default
on 32-bit architectures but not on 64-bit architectures?
Did the previous version of the ilp32 patch set also emulate
this the same way?

	Arnd
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