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

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Message-Id: <201208212014.01837.arnd@arndb.de>
Date:	Tue, 21 Aug 2012 20:14:01 +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 Tuesday 21 August 2012, Catalin Marinas wrote:
> > > +asmlinkage long sys_mmap(unsigned long addr, unsigned long len,
> > > +                    unsigned long prot, unsigned long flags,
> > > +                    unsigned long fd, off_t off)
> > > +{
> > > +   if (offset_in_page(off) != 0)
> > > +           return -EINVAL;
> > > +
> > > +   return sys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
> > > +}
> > 
> > I think
> > 
> > #define sys_mmap sys_mmap_pgoff 
> 
> There are slightly different semantics with the last argument of
> sys_mmap() which takes a byte offset. The sys_mmap_pgoff() function
> takes the offset shifted by PAGE_SHIFT (which is the same as sys_mmap2).
> 
> Looking at the other architectures, it makes sense to use a generic
> sys_mmap() implementation similar to the one above (or the ia-64, seems
> to be the most complete).
> 

Why that? The generic sys_mmap_pgoff was specifically added so new architectures
could just use that instead of having their own wrappers, see f8b72560.

	Arnd
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