On Fri, 2008-11-21 at 20:03 +1100, Paul Mackerras wrote:
> 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.
With your patch:
t1 = times((void*) 1);
if (t1 == -1) {
my_err = errno;
printf("Errno:%d, %s\n", my_err, strerror(my_err));
}
prints:
Errno:14, Bad address
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