1 files changed, 106 insertions, 0 deletions

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index ae63e584c340..80d5663db3bc 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1189,6 +1189,7 @@ END(device_not_available)
         /* runs on exception stack */
 KPROBE_ENTRY(debug)
         INTR_FRAME
+        PARAVIRT_ADJUST_EXCEPTION_FRAME
         pushq $0
         CFI_ADJUST_CFA_OFFSET 8         
         paranoidentry do_debug, DEBUG_STACK
@@ -1198,6 +1199,7 @@ KPROBE_END(debug)
         /* runs on exception stack */   
 KPROBE_ENTRY(nmi)
         INTR_FRAME
+        PARAVIRT_ADJUST_EXCEPTION_FRAME
         pushq $-1
         CFI_ADJUST_CFA_OFFSET 8
         paranoidentry do_nmi, 0, 0
@@ -1211,6 +1213,7 @@ KPROBE_END(nmi)
 
 KPROBE_ENTRY(int3)
         INTR_FRAME
+        PARAVIRT_ADJUST_EXCEPTION_FRAME
         pushq $0
         CFI_ADJUST_CFA_OFFSET 8
         paranoidentry do_int3, DEBUG_STACK
@@ -1237,6 +1240,7 @@ END(coprocessor_segment_overrun)
         /* runs on exception stack */
 ENTRY(double_fault)
         XCPT_FRAME
+        PARAVIRT_ADJUST_EXCEPTION_FRAME
         paranoidentry do_double_fault
         jmp paranoid_exit1
         CFI_ENDPROC
@@ -1253,6 +1257,7 @@ END(segment_not_present)
         /* runs on exception stack */
 ENTRY(stack_segment)
         XCPT_FRAME
+        PARAVIRT_ADJUST_EXCEPTION_FRAME
         paranoidentry do_stack_segment
         jmp paranoid_exit1
         CFI_ENDPROC
@@ -1278,6 +1283,7 @@ END(spurious_interrupt_bug)
         /* runs on exception stack */
 ENTRY(machine_check)
         INTR_FRAME
+        PARAVIRT_ADJUST_EXCEPTION_FRAME
         pushq $0
         CFI_ADJUST_CFA_OFFSET 8 
         paranoidentry do_machine_check
@@ -1312,3 +1318,103 @@ KPROBE_ENTRY(ignore_sysret)
         sysret
         CFI_ENDPROC
 ENDPROC(ignore_sysret)
+
+#ifdef CONFIG_XEN
+ENTRY(xen_hypervisor_callback)
+        zeroentry xen_do_hypervisor_callback
+END(xen_hypervisor_callback)
+
+/*
+# A note on the "critical region" in our callback handler.
+# We want to avoid stacking callback handlers due to events occurring
+# during handling of the last event. To do this, we keep events disabled
+# until we've done all processing. HOWEVER, we must enable events before
+# popping the stack frame (can't be done atomically) and so it would still
+# be possible to get enough handler activations to overflow the stack.
+# Although unlikely, bugs of that kind are hard to track down, so we'd
+# like to avoid the possibility.
+# So, on entry to the handler we detect whether we interrupted an
+# existing activation in its critical region -- if so, we pop the current
+# activation and restart the handler using the previous one.
+*/
+ENTRY(xen_do_hypervisor_callback)   # do_hypervisor_callback(struct *pt_regs)
+        CFI_STARTPROC
+/* Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will
+   see the correct pointer to the pt_regs */
+        movq %rdi, %rsp            # we don't return, adjust the stack frame
+        CFI_ENDPROC
+        CFI_DEFAULT_STACK
+11:     incl %gs:pda_irqcount
+        movq %rsp,%rbp
+        CFI_DEF_CFA_REGISTER rbp
+        cmovzq %gs:pda_irqstackptr,%rsp
+        pushq %rbp                      # backlink for old unwinder
+        call xen_evtchn_do_upcall
+        popq %rsp
+        CFI_DEF_CFA_REGISTER rsp
+        decl %gs:pda_irqcount
+        jmp  error_exit
+        CFI_ENDPROC
+END(do_hypervisor_callback)
+
+/*
+# Hypervisor uses this for application faults while it executes.
+# We get here for two reasons:
+#  1. Fault while reloading DS, ES, FS or GS
+#  2. Fault while executing IRET
+# Category 1 we do not need to fix up as Xen has already reloaded all segment
+# registers that could be reloaded and zeroed the others.
+# Category 2 we fix up by killing the current process. We cannot use the
+# normal Linux return path in this case because if we use the IRET hypercall
+# to pop the stack frame we end up in an infinite loop of failsafe callbacks.
+# We distinguish between categories by comparing each saved segment register
+# with its current contents: any discrepancy means we in category 1.
+*/
+ENTRY(xen_failsafe_callback)
+        framesz = (RIP-0x30)    /* workaround buggy gas */
+        _frame framesz
+        CFI_REL_OFFSET rcx, 0
+        CFI_REL_OFFSET r11, 8
+        movw %ds,%cx
+        cmpw %cx,0x10(%rsp)
+        CFI_REMEMBER_STATE
+        jne 1f
+        movw %es,%cx
+        cmpw %cx,0x18(%rsp)
+        jne 1f
+        movw %fs,%cx
+        cmpw %cx,0x20(%rsp)
+        jne 1f
+        movw %gs,%cx
+        cmpw %cx,0x28(%rsp)
+        jne 1f
+        /* All segments match their saved values => Category 2 (Bad IRET). */
+        movq (%rsp),%rcx
+        CFI_RESTORE rcx
+        movq 8(%rsp),%r11
+        CFI_RESTORE r11
+        addq $0x30,%rsp
+        CFI_ADJUST_CFA_OFFSET -0x30
+        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
+        CFI_RESTORE rcx
+        movq 8(%rsp),%r11
+        CFI_RESTORE r11
+        addq $0x30,%rsp
+        CFI_ADJUST_CFA_OFFSET -0x30
+        pushq $0
+        CFI_ADJUST_CFA_OFFSET 8
+        SAVE_ALL
+        jmp error_exit
+        CFI_ENDPROC
+END(xen_failsafe_callback)
+
+#endif /* CONFIG_XEN */