linux-kernel - Re: [PATCH v6 13/17] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it

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Message-ID: <16446627.b0Lo936ZJj@wuerfel>
Date:	Thu, 12 Nov 2015 14:24:57 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Andreas Schwab <schwab@...e.de>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Yury Norov <ynorov@...iumnetworks.com>, pinskia@...il.com,
	Prasun.Kapoor@...iumnetworks.com, catalin.marinas@....com,
	Nathan_Lynch@...tor.com, linux-kernel@...r.kernel.org,
	agraf@...e.de, klimov.linux@...il.com,
	Andrew Pinski <Andrew.Pinski@...iumnetworks.com>,
	broonie@...nel.org, jan.dakinevich@...il.com,
	Andrew Pinski <apinski@...ium.com>, ddaney.cavm@...il.com,
	bamvor.zhangjian@...wei.com, philipp.tomsich@...obroma-systems.com,
	andrey.konovalov@...aro.org,
	christoph.muellner@...obroma-systems.com
Subject: Re: [PATCH v6 13/17] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it

On Thursday 12 November 2015 10:44:55 Andreas Schwab wrote:
> Arnd Bergmann <arnd@...db.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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