lkml.org 
[lkml]   [2018]   [May]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v4 1/2] xen/PVH: Set up GS segment for stack canary
>>> On 22.05.18 at 15:45, <brgerst@gmail.com> wrote:
> On Mon, May 21, 2018 at 11:54 PM, Boris Ostrovsky <boris.ostrovsky@oracle.com> wrote:
>> @@ -98,6 +101,12 @@ ENTRY(pvh_start_xen)
>> /* 64-bit entry point. */
>> .code64
>> 1:
>> + /* Set base address in stack canary descriptor. */
>> + mov $MSR_GS_BASE,%ecx
>> + mov $canary, %rax
>> + cdq
>> + wrmsr
>
> CDQ only sign-extends EAX to RAX. What you really want is to move the
> high 32-bits to EDX (or zero EDX if we can guarantee it is loaded
> below 4G).

What you describe is CDQE (AT&T name: CLTD); CDQ (AT&T: CLTQ)
sign-extends EAX to EDX:EAX.

Jan


\
 
 \ /
  Last update: 2018-05-22 15:58    [W:0.064 / U:1.552 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site