On Sat, Feb 14, 2004 at 07:28:49AM +0100, Thiemo Seufer wrote:
> Jun Sun wrote:
> > On Sat, Feb 14, 2004 at 03:17:40AM +0100, Thiemo Seufer wrote:
> > > Ralf Baechle wrote:
> > > [snip]
> > > > Anyway, gcc could load next weeks lucky lottery numbers into the
> > > > s-registers after saving them. That'd break save_static but not the
> > > > ABI which only promises to restore the old values in s-registers on
> > > > return.
> > >
> > > Ok, it could, but adding such insns to the prologue wouldn't make
> > > sense at all, so this is unlikely to happen.
> > >
> >
> > OS people who have been around long enough know "unlikely" things
> > always end up happening. :)
> [snip]
> > sys_sigsuspend(struct pt_regs regs)
> > {
> > 8008e280: 27bdffc0 addiu $sp,$sp,-64
> > 8008e284: afb00030 sw $s0,48($sp)
> > sigset_t *uset, saveset, newset;
> >
> > save_static(®s);
>
> Which is a compiler bug, because it schedules around __asm__ __volatile__,
> but not a breakage caused by the prologue.
>
> There's no way to be safe from broken compilers.
Not at all. It's not code being scheduled around the asm - it's _part
of the prologue_ to save $s0 to the stack. Register saves are
considered part of the prologue.
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer
