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>

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 7cc2de7..6aa6932 100644 (file)
--- 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 */