linux-kernel - Re: [PATCH 20/25] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it

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Message-ID: <4876119.A8fbdncu9Z@wuerfel>
Date:	Wed, 11 May 2016 10:09:52 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	"Zhangjian (Bamvor)" <bamvor.zhangjian@...wei.com>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
	Andrew Pinski <Andrew.Pinski@...iumnetworks.com>,
	catalin.marinas@....com, heiko.carstens@...ibm.com,
	Yury Norov <ynorov@...iumnetworks.com>,
	Hanjun Guo <guohanjun@...wei.com>, joseph@...esourcery.com,
	linux-arch@...r.kernel.org, linux-s390@...r.kernel.org,
	"jijun (D)" <jijun2@...wei.com>, Prasun.Kapoor@...iumnetworks.com,
	schwab@...e.de, agraf@...e.de, pinskia@...il.com,
	klimov.linux@...il.com, broonie@...nel.org,
	Nathan_Lynch@...tor.com, linux-kernel@...r.kernel.org,
	Andrew Pinski <apinski@...ium.com>, schwidefsky@...ibm.com,
	christoph.muellner@...obroma-systems.com
Subject: Re: [PATCH 20/25] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it

On Wednesday 11 May 2016 10:04:16 Zhangjian wrote:
> > I don't remember. It's probably not important whether we have the shift
> > in there, as long as it's independent of the actual kernel page size and
> > user space and kernel agree on the calling conventions.
> Well. I am ok with where to shift the pages size because we get the same
> result. I was just thinking if we should get rid of the name of mmap2 in our
> ILP32 porting. Actually, it is mmap but we name it as mmap2. User may confused
> if they do not know the implementations.

That is a good point: If the implementation matches the mmap() behavior rather than
mmap2(), we should rename the macro by doing

#undef __NR_mmap2
#define __NR_mmap 222

in the uapi/asm/unistd.h file for ilp32 mode. Alternatively we can keep the
__NR_mmap2 definition but then we need to pass the pgoff (value shifted by
12 bits) argument rather than the size in bytes.

	Arnd