linux-kernel - Re: [PATCH v6 14/21] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it

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Message-ID: <20160108111318.GA24066@yury-N73SV>
Date:	Fri, 8 Jan 2016 14:13:18 +0300
From:	Yury Norov <ynorov@...iumnetworks.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	<catalin.marinas@....com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <pinskia@...il.com>,
	<Prasun.Kapoor@...iumnetworks.com>, <schwab@...e.de>,
	<Nathan_Lynch@...tor.com>, <agraf@...e.de>,
	<klimov.linux@...il.com>, <broonie@...nel.org>,
	<jan.dakinevich@...il.com>, <ddaney.cavm@...il.com>,
	<bamvor.zhangjian@...wei.com>,
	<philipp.tomsich@...obroma-systems.com>, <joseph@...esourcery.com>,
	<christoph.muellner@...obroma-systems.com>,
	Andrew Pinski <apinski@...ium.com>,
	Andrew Pinski <Andrew.Pinski@...iumnetworks.com>
Subject: Re: [PATCH v6 14/21] arm64:ilp32: add sys_ilp32.c and a separate
 table (in entry.S) to use it

On Fri, Jan 08, 2016 at 10:21:06AM +0100, Arnd Bergmann wrote:
> On Friday 08 January 2016 02:34:32 Yury Norov wrote:
> 
> > @@ -688,6 +692,12 @@ ni_sys:
> >  	b	ret_fast_syscall
> >  ENDPROC(el0_svc)
> >  
> > +#ifdef CONFIG_ARM64_ILP32
> > +el0_ilp32_svc:
> > +	adrp	stbl, sys_call_ilp32_table // load syscall table pointer
> > +	b el0_svc_naked
> > +#endif
> 
> Don't we still need some code that clears the top halves of the 32-bit
> arguments? That thread has taken so many turns now that I'm confused
> about what we actually need, but I thought we had concluded that your
> current approach has at some some problems.

We are discussing how to do it better - make a generic solution from
s390 with individual syscall handling, or reproduce s390 solution for
ILP32, or zero top-half registers and not use top half of register at
all. As I understand, we stand on 1st option, and agreed to introduce
it separately.

> 
> > +#include <asm/syscall.h>
> > +
> > +#undef __SYSCALL
> > +#undef __SC_COMP
> > +#undef __SC_3264
> > +#undef __SC_COMP_3264
> 
> The four #undef are not needed, right?
> 
> 	Arnd