Re: Is espfix64's double-fault thing OK on Xen?
From: Andy Lutomirski
Date: Mon Jul 14 2014 - 13:11:42 EST
On Mon, Jul 14, 2014 at 10:04 AM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 07/09/2014 04:17 PM, Andy Lutomirski wrote:
>> This part in __do_double_fault looks fishy:
>> cmpl $__KERNEL_CS,CS(%rdi)
>> jne do_double_fault
>> Shouldn't that be:
>> test $3,CS(%rdi)
>> jnz do_double_fault
> No, it should be fine. The *only* case where we need to do the espfix
> magic is when we are on __KERNEL_CS.
IIRC Xen has a somewhat different GDT, and at least the userspace CS
in IA32_STAR disagrees with normal Linux. If the kernel CS is also
strange, then there will be an extra possible CS value here.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/