On Thu, Jan 03, 2019 at 02:52:15PM +0100, Thomas Huth wrote:
> On 2019-01-03 11:08, Janosch Frank wrote:
> > +/*
> > + * STCKE returns 16 bytes, which include the epoch, tod value and a
> > + * programmable field. The value has to be trimmed to be able to work
> > + * with it. As there's still some time to 2042, this code is not ready
> > + * for multi epoch values.
> > + */
> > +static inline void stcke(char *tod)
> > +{
> > + asm volatile(
> > + " stcke %[tod]\n"
> > + : [tod] "=Q" (tod)
> > + : : "cc");
> > +}
>
> I'm not an inline-assembly wizzard, but the "=Q" constraint looks wrong
> to me here. Are you sure that this is working as expected?
Yes, this is wrong. That's the reason why the kernel variant has the
typedef + cast (see get_tod_clock_ext() in arch/s390/include/asm/timex.h).
The variant above tells the compiler that only a single byte is written to.
