linux-kernel - Re: [PATCH] introduce kernel_execve function to replace __KERNEL_SYSCALLS_

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Date:	Tue, 22 Aug 2006 10:00:46 +0200
From:	Björn Steinbrink <B.Steinbrink@....de>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Arnd Bergmann <arnd@...db.de>, Paul Mackerras <paulus@...ba.org>,
	Russell King <rmk+lkml@....linux.org.uk>,
	Andrew Morton <akpm@...l.org>, rusty@...tcorp.com.au,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH] introduce kernel_execve function to replace __KERNEL_SYSCALLS__

On 2006.08.22 17:29:02 +1000, Benjamin Herrenschmidt wrote:
> On Mon, 2006-08-21 at 17:12 +0200, Arnd Bergmann wrote:
> > On Monday 21 August 2006 02:36, Paul Mackerras wrote:
> > > > Iit turned out most of the architectures that already implement
> > > > their own execve() call instead of using the _syscall3 function
> > > > for it end up passing the return value of sys_execve down, 
> > > > instead of setting errno.
> > > 
> > > I really don't like having an "errno" variable in the kernel.  What if
> > > two processes are doing an execve concurrently?
> > 
> > The point is that we have two different schemes in the kernel that
> > conflict:
> > 
> > alpha, arm{,26}, ia64, parisc, powerpc and x86_64 pass the error
> > code from execve, all others pass -1 and set the global errno.
> 
> All other need to be fixed then... having an errno is just plain wrong.

I'm working on a patch loosely based on Arnd's that changes the
in-kernel syscall macros to directly return the error codes. Once
kernel_execve is implemented for each arch, only um should remain as a
user and I found only two calls there that care about the exact
non-zero return value, both are simple to adapt.
That should allow to get rid of errno completely. If someone knows a
reason why this is destined to fail (maybe syscalls returning char?!),
please let me know before I waste too much time on it ;)

Björn
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