Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / arch / x86 / kernel / entry_64.S

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index bcf28e1ce1a700a0300d352a5aaf22bb5b70edad..69babd8c834f920b4d54c48e1f41a08d4f7fef6f 100644 (file)
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1740,10 +1740,30 @@ end_repeat_nmi:
         */
        call save_paranoid
        DEFAULT_FRAME 0
+
+       /*
+        * Save off the CR2 register. If we take a page fault in the NMI then
+        * it could corrupt the CR2 value. If the NMI preempts a page fault
+        * handler before it was able to read the CR2 register, and then the
+        * NMI itself takes a page fault, the page fault that was preempted
+        * will read the information from the NMI page fault and not the
+        * origin fault. Save it off and restore it if it changes.
+        * Use the r12 callee-saved register.
+        */
+       movq %cr2, %r12
+
        /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
        movq %rsp,%rdi
        movq $-1,%rsi
        call do_nmi
+
+       /* Did the NMI take a page fault? Restore cr2 if it did */
+       movq %cr2, %rcx
+       cmpq %rcx, %r12
+       je 1f
+       movq %r12, %cr2
+1:
+       
        testl %ebx,%ebx                         /* swapgs needed? */
        jnz nmi_restore
 nmi_swapgs: