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From: Heiko Carstens <heiko.carstens@de.ibm.com>
To: Matthew Wilcox <matthew@wil.cx>
Cc: Gerd Hoffmann <kraxel@redhat.com>,
	linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: [PATCH v2] Add preadv and pwritev system calls.
Date: Sun, 14 Dec 2008 12:49:31 +0100	[thread overview]
Message-ID: <20081214114931.GA4556@osiris.boeblingen.de.ibm.com> (raw)
In-Reply-To: <20081212152929.GM26095@parisc-linux.org>

On Fri, Dec 12, 2008 at 08:29:29AM -0700, Matthew Wilcox wrote:
> On Fri, Dec 12, 2008 at 03:00:40PM +0100, Gerd Hoffmann wrote:
> > The patch sports the actual system call implementation and the windup in
> > the x86 system call tables.  Other archs are TBD.
> 
> > +asmlinkage ssize_t sys_preadv(unsigned long fd, const struct iovec __user *vec,
> > +                              unsigned long vlen, loff_t pos)
> > +asmlinkage ssize_t sys_pwritev(unsigned long fd, const struct iovec __user *vec,
> > +                               unsigned long vlen, loff_t pos)
> 
> Are these prototypes required?  MIPS and PARISC will need wrappers to
> fix them if they are.  These two architectures have an ABI which
> requires 64-bit arguments to be passed in aligned pairs of registers,
> but glibc doesn't know that (and given the existence of syscall(3),
> can't do much about it even if it knew), so some of the arguments end up
> in the wrong registers.
> 
> Things will go much better if we can prototype these as:
> 
> asmlinkage ssize_t sys_preadv(unsigned int fd, const struct iovec __user *vec,
> 				loff_t pos, unsigned long vlen);
> asmlinkage ssize_t sys_pwritev(unsigned int fd, const struct iovec __user *vec,
> 				loff_t pos, unsigned long vlen);
> 
> That way 'pos' ends up split between arg2 and arg3 and vlen ends up in
> arg4 instead of having vlen in arg2 and pos in arg3 and arg4 which then
> have to be munged to be in arg4 and arg5 by a compat wrapper.
> 
> I seem to recall the s390 folks having some concerns with this kind of
> thing too, but I forget what they are, so I'll let them weigh in on
> this.

I think a lot of stuff that needs to be known for new system calls was
written up with these two postings:

http://marc.info/?l=linux-arch&m=118277150812137&w=2
http://lkml.org/lkml/2007/8/1/354

  parent reply	other threads:[~2008-12-14 11:49 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-12-12 14:00 Gerd Hoffmann
2008-12-12 15:29 ` Matthew Wilcox
2008-12-12 15:48   ` Gerd Hoffmann
2008-12-12 15:51     ` Matthew Wilcox
2008-12-12 16:02       ` Gerd Hoffmann
2008-12-12 17:03         ` Matthew Wilcox
2008-12-12 18:21           ` Alan Cox
2008-12-12 19:02             ` Russell King
2008-12-12 18:29         ` Scott Lurndal
2008-12-12 19:07           ` Russell King
2008-12-12 19:56             ` Gerd Hoffmann
2008-12-12 19:56               ` Gerd Hoffmann
2008-12-12 20:12               ` Russell King
2008-12-12 20:39                 ` Gerd Hoffmann
2008-12-12 20:39                   ` Gerd Hoffmann
2008-12-14 18:19               ` Pavel Machek
2008-12-15 16:37         ` Jennifer Pioch
2008-12-15 20:43           ` Gerd Hoffmann
2008-12-16  9:57             ` Arnd Bergmann
2008-12-17  1:45               ` [osol-code] " Dan Mick
2008-12-17  1:45                 ` Dan Mick
2008-12-12 19:47   ` Arnd Bergmann
2008-12-12 20:02     ` Gerd Hoffmann
2008-12-14 11:49   ` Heiko Carstens [this message]
2008-12-15  4:14   ` Paul Mackerras
2008-12-15  6:20     ` David Miller
2008-12-12 15:40 ` Ralf Baechle
2008-12-12 16:59 ` Russell King
2008-12-13  1:18 ` Michael Kerrisk

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