Gabriel Paubert writes:

On Fri, Nov 21, 2008 at 10:52:14AM +1100, Paul Mackerras wrote:

quoted

Joakim Tjernlund writes:

quoted

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.