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From: Gerd Hoffmann <kraxel@redhat.com>
To: Matthew Wilcox <matthew@wil.cx>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	Ulrich Drepper <drepper@redhat.com>
Subject: Re: [PATCH v2] Add preadv and pwritev system calls.
Date: Fri, 12 Dec 2008 16:48:36 +0100	[thread overview]
Message-ID: <494287D4.2070909@redhat.com> (raw)
In-Reply-To: <20081212152929.GM26095@parisc-linux.org>

Matthew Wilcox wrote:
>> +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);

Hmm.  It is the argument ordering used by NetBSD, thats why I used that
too.  It certainly should be the application-visible ordering.  We'll
have glibc between apps and kernel though, so I think we can reorder the
arguments at syscall level if that helps on these archs.  Cc'ing Ulrich
Drepper for comments on that.

> By the way, why did you make 'fd' an unsigned long?  The rest of the
> kernel uses unsigned int.

sys_{readv,writev} have unsigned long too, this is where I got it from.
 Don't know what the reason for this is, it looks a bit odd indeed.

cheers,
  Gerd


  reply	other threads:[~2008-12-12 15:49 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 [this message]
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
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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