From: "David S. Miller" <davem@davemloft.net>
To: torvalds@osdl.org
Cc: sfr@canb.auug.org.au, akpm@osdl.org,
linux-kernel@vger.kernel.org, drepper@redhat.com,
linux-arch@vger.kernel.org
Subject: Re: [PATCH] compat: fix compat_sys_openat and friends
Date: Wed, 01 Feb 2006 21:56:44 -0800 (PST) [thread overview]
Message-ID: <20060201.215644.116024082.davem@davemloft.net> (raw)
In-Reply-To: <Pine.LNX.4.64.0602012134150.21884@g5.osdl.org>
From: Linus Torvalds <torvalds@osdl.org>
Date: Wed, 1 Feb 2006 21:36:40 -0800 (PST)
> Wouldn't it be _much_ better to declare the argument as a "long", since
> some architectures (alpha, for example) may assume that 32-bit arguments
> have been _sign_extended, not zero-extended.
>
> Then, when the "compat_sys_xxxx()" function passes the "long" down to the
> _real_ function (which takes an "int"), those architectures (and only
> those architectures) that actually have assumptions about high bits will
> have the compiler automatically do the right zero- or sign-extensions at
> that call-site.
There is the convention that for the compat system calls all the args
will be 32-bit zero extended by the platform syscall entry code before
the C code is invoked. This topic used to come up a lot and finally
we all decided that was the thing to do.
It's important (at least I think so :-) for all of this generic compat
code to be able to have a well defined argument environment.
Anyways, I think that's how Stephen arrived at his patch.
next prev parent reply other threads:[~2006-02-02 5:56 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-02 5:11 [PATCH] compat: fix compat_sys_openat and friends Stephen Rothwell
2006-02-02 5:36 ` Linus Torvalds
2006-02-02 5:56 ` David S. Miller [this message]
2006-02-02 6:05 ` Stephen Rothwell
2006-02-02 6:11 ` Linus Torvalds
2006-02-02 12:01 ` Ralf Baechle
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