linux-kernel - Re: 64-syscall args on 32-bit vs syscall()

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Message-Id: <1268931823.19726.127.camel@spokane1.rchland.ibm.com>
Date:	Thu, 18 Mar 2010 12:03:43 -0500
From:	Steven Munroe <munroesj@...ux.vnet.ibm.com>
To:	Andreas Schwab <schwab@...hat.com>
Cc:	munroesj@...ibm.com,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Ulrich Drepper <drepper@...hat.com>,
	David Miller <davem@...emloft.net>, ralf@...ux-mips.org,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel@...savvy.com, torvalds@...ux-foundation.org
Subject: Re: 64-syscall args on 32-bit vs syscall()

On Thu, 2010-03-18 at 17:21 +0100, Andreas Schwab wrote:
> Steven Munroe <munroesj@...ux.vnet.ibm.com> writes:
> 
> > extern long int syscall (long int __sysno, ...) __THROW;
> >
> > #endif	/* Use misc.  */
> >
> > Changing this would be an ABI change and would have to be versioned. It
> > would effect any one using syscall not just SYS_fallocate.
> >
> > the question is do programmers in practice include unistd.h when they
> > use syscall.
> >
> > If the changed prototype is not in scope then the 1st parm (__sysno)
> > defaults to int and is passed in on r3 which gets moved to r0.
> 
> int is incompatible with long, so you already get undefined behaviour
> anyway.
> 
Sorry in and long are compatible in 32-bit but not long long.

int and long are not compatible in 64-bit

It is hard the keep all the nodes and arguments straight.

But the concern about changing the prototype and are people actually
using the prototype are still valid.

> Andreas.
> 

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