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Date: Fri, 21 Nov 2008 20:03:06 +1100
From: Paul Mackerras <paulus@samba.org>
To: Gabriel Paubert <paubert@iram.es>
Subject: Re: times(2) sys call bug?
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Gabriel Paubert writes:

> On Fri, Nov 21, 2008 at 10:52:14AM +1100, Paul Mackerras wrote:
> > Joakim Tjernlund writes:
> > 
> > > This little hack changes the kernel sys call handling in an crude
> > > way and then it works. Apperently the kernel thinks is an error if the
> > > syscall returns a value between -_LAST_ERRNO and -1.
> > 
> > Try this patch and let me if it fixes it.  If it does I'll push it
> > upstream.
> 
> With your patch, you won't get EFAULT if you pass a bad
> address, but a constant, time independent value, unless
> I miss something. 

I think you are missing something, namely that I put the call to
force_successful_syscall_return() AFTER the return -EFAULT.

You should get an EFAULT error if the address is bad, i.e. on return
to userspace with cr0.SO = 1 and r3 = EFAULT (note, not -EFAULT).  On
a non-error return you should get cr0.SO = 0 and r3 containing the
return value (even if it's -EFAULT).  It's possible that glibc will
stuff it up again after that but I hope not.

Paul.