On Mon, 2018-06-11 at 10:17 +0200, Peter Zijlstra wrote:
> On Thu, Jun 07, 2018 at 09:40:02AM -0700, Andy Lutomirski wrote:
> > On Thu, Jun 7, 2018 at 7:41 AM Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx> wrote:
>
> > Peterz, isn't there some fancy better way we're supposed to handle the
> > error return these days?
>
> > > + asm volatile("1:.byte 0x66, 0x0f, 0x38, 0xf5, 0x37\n"
> > > + "xor %[err],%[err]\n"
> > > + "2:\n"
> > > + ".section .fixup,\"ax\"\n"
> > > + "3: mov $-1,%[err]; jmp 2b\n"
> > > + ".previous\n"
> > > + _ASM_EXTABLE(1b, 3b)
> > > + : [err] "=a" (err)
> > > + : [val] "S" (val), [addr] "D" (addr)
> > > + : "memory");
>
> So the alternative is something like:
>
> __visible bool ex_handler_wuss(const struct exception_table_entry *fixup,
> struct pt_regs *regs, int trapnr)
> {
> regs->ip = ex_fixup_addr(fixup);
> regs->ax = -1L;
>
> return true;
> }
>
>
> int err = 0;
>
> asm volatile("1: INSN_WUSS\n"
> "2:\n"
> _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_wuss)
> : "=a" (err)
> : "S" (val), "D" (addr));
>
> But I'm not at all sure that's actually better.
Thanks! I will fix it.
Yu-cheng
