On Tue, 04 Jun 2013 09:27:03 +0100
"Jan Beulich" <jbeul...@suse.com> wrote:
> >>> On 04.06.13 at 02:43, Mukesh Rathor <mukesh.rat...@oracle.com>
> >>> wrote:
> > @@ -1327,6 +1329,18 @@ static void __init
> > xen_setup_stackprotector(void) /* PVH TBD/FIXME: investigate
> > setup_stack_canary_segment */ if
> > (xen_feature(XENFEAT_auto_translated_physmap))
> > { switch_to_new_gdt(0); +
> > + /* xen started us with null selectors. load them
> > now */
> > + __asm__ __volatile__ (
> > + "movl %0,%%ds\n"
> > + "movl %0,%%ss\n"
> > + "pushq %%rax\n"
> > + "leaq 1f(%%rip),%%rax\n"
> > + "pushq %%rax\n"
> > + "retfq\n"
> > + "1:\n"
> > + : : "r" (__KERNEL_DS), "a" (__KERNEL_CS) :
> > "memory"); +
>
> I can see why you want CS to be reloaded (and CS, other than the
> comment says, clearly hasn't been holding a null selector up to here.
>
> I can't immediately see why you'd need SS to be other than null, and
> it completely escapes me why you'd need to DS (but not ES) to be
> non-null.
>
> Furthermore, is there any reason why you use "retfq" (Intel syntax)
> when all assembly code otherwise uses AT&T syntax (the proper
> equivalent here would be "lretq")?
>
> And finally, please consistently use %<number> (which, once
> fixed, will make clear that the second constraint really can be "r"),
> and avoid using suffixes on moves to/from selector registers
> (which, once fixed, will make clear that at least the first constraint
> really can be relaxed to "rm").
Following OK? :
if (xen_feature(XENFEAT_auto_translated_physmap)) {
switch_to_new_gdt(0);
asm volatile (
"pushq %%rax\n"
"leaq 1f(%%rip),%%rax\n"
"pushq %%rax\n"
"lretq\n"
"1:\n"
: : "a" (__KERNEL_CS) : "memory");
return;
}
thanks,
Mukesh
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
