xen64: implement failsafe callback

Implement the failsafe callback, so that iret and segment register
load exceptions are reported to the kernel.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 9 insertions, 7 deletions

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 7cc2de796146..6aa6932e21b1 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1365,10 +1365,8 @@ END(do_hypervisor_callback)
 # with its current contents: any discrepancy means we in category 1.
 */
 ENTRY(xen_failsafe_callback)
-#if 1
-        ud2a
-#else
-        _frame (RIP-0x30)
+        framesz = (RIP-0x30)    /* workaround buggy gas */
+        _frame framesz
         CFI_REL_OFFSET rcx, 0
         CFI_REL_OFFSET r11, 8
         movw %ds,%cx
@@ -1391,8 +1389,13 @@ ENTRY(xen_failsafe_callback)
         CFI_RESTORE r11
         addq $0x30,%rsp
         CFI_ADJUST_CFA_OFFSET -0x30
-        movq $11,%rdi   /* SIGSEGV */
-        jmp do_exit
+        pushq $0
+        CFI_ADJUST_CFA_OFFSET 8
+        pushq %r11
+        CFI_ADJUST_CFA_OFFSET 8
+        pushq %rcx
+        CFI_ADJUST_CFA_OFFSET 8
+        jmp general_protection
         CFI_RESTORE_STATE
 1:      /* Segment mismatch => Category 1 (Bad segment). Retry the IRET. */
         movq (%rsp),%rcx
@@ -1406,7 +1409,6 @@ ENTRY(xen_failsafe_callback)
         SAVE_ALL
         jmp error_exit
         CFI_ENDPROC
-#endif
 END(xen_failsafe_callback)
 
 #endif /* CONFIG_XEN */