Messages in this thread | | | Date | Mon, 11 Jun 2018 10:17:04 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 02/10] x86/cet: Introduce WRUSS instruction |
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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@intel.com> 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.
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