[PATCH 29 of 36] Use __KERNEL_DS as SS when returning to a kernelthread (VERIFY)

[Jeremy Fitzhardinge]

    This is needed when the kernel is running on RING3, such as under Xen.
    x86_64 has a weird feature that makes it #GP on iret when SS is a null
    descriptor.

    This need to be tested on bare metal to make sure it doesn't cause any
    problems. AMD specs say SS is always ignored (except on iret?).

Signed-off-by: Eduardo Habkost <ehabkost@xxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/kernel/entry_64.S |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -212,7 +212,7 @@
 	.macro FAKE_STACK_FRAME child_rip
 	/* push in order ss, rsp, eflags, cs, rip */
 	xorl %eax, %eax
-	pushq %rax /* ss */
+	pushq $__KERNEL_DS /* ss */
 	CFI_ADJUST_CFA_OFFSET	8
 	/*CFI_REL_OFFSET	ss,0*/
 	pushq %rax /* rsp */


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