[Xen-devel] [PATCH 3/4] xen/PVH: Set up GS segment for stack canary

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

We are making calls to C code (e.g. xen_prepare_pvh()) which may use
stack canary (stored in GS segment).

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
 arch/x86/xen/xen-pvh.S | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/xen/xen-pvh.S b/arch/x86/xen/xen-pvh.S
index 373fef0..4eed586 100644
--- a/arch/x86/xen/xen-pvh.S
+++ b/arch/x86/xen/xen-pvh.S
@@ -54,6 +54,9 @@
  * charge of setting up it's own stack, GDT and IDT.
  */
 
+#define PVH_GDT_ENTRY_CANARY    4
+#define PVH_CANARY_SEL          (PVH_GDT_ENTRY_CANARY * 8)
+
 ENTRY(pvh_start_xen)
        cld
 
@@ -64,6 +67,9 @@ ENTRY(pvh_start_xen)
        mov %eax,%es
        mov %eax,%ss
 
+       mov $(PVH_CANARY_SEL),%eax
+       mov %eax,%gs
+
        /* Stash hvm_start_info. */
        mov $_pa(pvh_start_info), %edi
        mov %ebx, %esi
@@ -150,6 +156,7 @@ gdt_start:
        .quad 0x00cf9a000000ffff            /* __BOOT_CS */
 #endif
        .quad 0x00cf92000000ffff            /* __BOOT_DS */
+       .quad 0x0040900000000018            /* PVH_CANARY_SEL */
 gdt_end:
 
        .balign 4
-- 
2.9.3


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