[Xen-changelog] [xen-unstable] xen: prevent a 64 bit guest setting reserved bits in DR7

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
# Date 1346844445 -3600
# Node ID 4f1c696482016e7ba76f222c5875618c37680286
# Parent  9dc729b7559535af78209f325c76b16c767ef7bf
xen: prevent a 64 bit guest setting reserved bits in DR7

The upper 32 bits of this register are reserved and should be written as
zero.

This is XSA-12 / CVE-2012-3494

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---


diff -r 9dc729b75595 -r 4f1c69648201 xen/include/asm-x86/debugreg.h
--- a/xen/include/asm-x86/debugreg.h    Mon Sep 03 11:22:02 2012 +0100
+++ b/xen/include/asm-x86/debugreg.h    Wed Sep 05 12:27:25 2012 +0100
@@ -58,7 +58,7 @@
    We can slow the instruction pipeline for instructions coming via the
    gdt or the ldt if we want to.  I am not sure why this is an advantage */
 
-#define DR_CONTROL_RESERVED_ZERO (0x0000d800ul) /* Reserved, read as zero */
+#define DR_CONTROL_RESERVED_ZERO (~0xffff27fful) /* Reserved, read as zero */
 #define DR_CONTROL_RESERVED_ONE  (0x00000400ul) /* Reserved, read as one */
 #define DR_LOCAL_EXACT_ENABLE    (0x00000100ul) /* Local exact enable */
 #define DR_GLOBAL_EXACT_ENABLE   (0x00000200ul) /* Global exact enable */

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