linux-kernel - Re: [PATCH v2 17/31] arm64: System calls handling

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Message-Id: <201208221227.14274.arnd@arndb.de>
Date:	Wed, 22 Aug 2012 12:27:14 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Will Deacon <Will.Deacon@....com>
Subject: Re: [PATCH v2 17/31] arm64: System calls handling

On Wednesday 22 August 2012, Catalin Marinas wrote:
> But what's more important - moving this wrapper to glibc causes issues
> with the page size. We support both 4KB and 64KB pages on 64-bit systems
> (the latter without compat support). The kernel is in a better position
> to do the shift by a compile-time constant. Glibc would need to enquire
> the actual page size to do the shift before calling sys_mmap_pgoff. If
> we assume in glibc that the shift is always 12, we need another wrapper
> in the kernel anyway for 64KB page configuration. So passing the offset
> in bytes worked best for us.

Right, the kernel interface should really be independent of the page
size, as sys_mmap2 normally is, and sys_mmap2 is not provided here.

	Arnd
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