linux-kernel - Re: [microblaze-linux] [RESEND PATCH] microblaze: Fix clone syscall

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Message-ID: <20130724065957.GR3249@brightrain.aerifal.cx>
Date:	Wed, 24 Jul 2013 02:59:57 -0400
From:	Rich Felker <dalias@...ifal.cx>
To:	Michal Simek <monstr@...str.eu>
Cc:	Michal Simek <michal.simek@...inx.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	James Hogan <james.hogan@...tec.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
	dholsgrove@...inx.com, Al Viro <viro@...IV.linux.org.uk>,
	microblaze-uclinux@...e.uq.edu.au,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [microblaze-linux] [RESEND PATCH] microblaze: Fix clone syscall

On Wed, Jul 24, 2013 at 08:48:27AM +0200, Michal Simek wrote:
> >> Create new CLONE_BACKWARDS3 type where stack_size is passed
> >> via 3rd argument, parent thread id pointer via 4th,
> >> child thread id pointer via 5th and tls value as 6th
> >> argument
> > 
> > I believe this also affects us in musl. What is the motivation for
> > making a configure option that results in there being two incompatible
> > syscall ABIs for the same arch?
> > This sounds like a really bad idea...
> 
> This patch fixes bug which was introduced by Al's patch where he moved
> clone implementation from microblaze folder to generic location.
> It means I am not creating two incompatible syscalls ABIs but fixing
> broken one.

So this patch is just fixing a regression in the kernel?

> > And how was glibc successfuly using a form that mismatched the
> > existing kernel? Did nobody ever use/test it?
> 
> We are running LTP syscall tests and there is not LTP test which
> was able to find out this mismatch in clone. That's why I haven't
> figure it out at that time and ACKed that origin patch.

I would think pthread_create would have broken pretty badly; I
remember early-on in porting musl to microblaze, we had the clone
arguments misordered, and it blew up badly. ;) Perhaps you could just
run some general libc/libpthread level tests to catch things like this
that are hard to measure at the syscall-test level with existing
tests.

Rich
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