linux-kernel - Re: [PATCH 25/25] arm64:ilp32: add ARM64

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Date:	Fri, 29 Apr 2016 19:26:12 +0300
From:	Yury Norov <ynorov@...iumnetworks.com>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	<linux-arch@...r.kernel.org>, <linux-s390@...r.kernel.org>,
	<arnd@...db.de>, <pinskia@...il.com>,
	<Prasun.Kapoor@...iumnetworks.com>, <schwab@...e.de>,
	<joseph@...esourcery.com>, <linux-doc@...r.kernel.org>,
	<heiko.carstens@...ibm.com>, <linux-kernel@...r.kernel.org>,
	<agraf@...e.de>, <klimov.linux@...il.com>,
	Andrew Pinski <Andrew.Pinski@...iumnetworks.com>,
	<broonie@...nel.org>, <bamvor.zhangjian@...wei.com>,
	Andrew Pinski <apinski@...ium.com>, <schwidefsky@...ibm.com>,
	<Nathan_Lynch@...tor.com>,
	Philipp Tomsich <philipp.tomsich@...obroma-systems.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<christoph.muellner@...obroma-systems.com>
Subject: Re: [PATCH 25/25] arm64:ilp32: add ARM64_ILP32 to Kconfig

On Fri, Apr 29, 2016 at 05:14:46PM +0100, Catalin Marinas wrote:
> On Fri, Apr 29, 2016 at 07:08:55PM +0300, Yury Norov wrote:
> > On Fri, Apr 29, 2016 at 05:03:34PM +0100, Catalin Marinas wrote:
> > > On Wed, Apr 06, 2016 at 01:08:47AM +0300, Yury Norov wrote:
> > > > +config ARM64_ILP32
> > > > +	bool "Kernel support for ILP32"
> > > > +	select COMPAT_WRAPPER
> > > > +	help
> > > > +	  This option enables support for AArch64 ILP32 user space.  ILP32
> > > > +	  is an ABI where long and pointers are 32bits but it uses the AARCH64
> > > > +	  instruction set.
> > > 
> > > Is there any penalty for AArch32 tasks when selecting COMPAT_WRAPPER?
> > 
> > No. AARCH32 doesn't define __SC_WRAP and so __SYSCALL macro is used,
> > which fills syscall table with sys_xxx versions, not compat_sys_xxx.
> 
> Ah, I forgot it has its own unistd32.h.
> 
> Thanks.

Even if it was sharing generic unistd,h, it's OK as well. To use
wrappers, you have to enable COMPAT_WRAPPER (which is enabled even if
only a single ABI needs it) *and* define  __SC_WRAP in corresponding
sys_xxx.c, which is individual for each abi, of course.

> 
> -- 
> Catalin