UBUNTU: SAUCE: rfi-flush: Make DEBUG_RFI a CONFIG option

CVE-2017-5754

BugLink: http://bugs.launchpad.net/bugs/1742772Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>

arch/powerpc/Kconfig.debug

@@ -356,4 +356,14 @@ config FAIL_IOMMU
 
 	  If you are unsure, say N.
 
+config PPC_DEBUG_RFI
+	bool "Debug RFIs (Return From Interrupt)"
+	depends on PPC_BOOK3S_64
+	help
+	  The enables extra debug code in some RFI (Return From Interrupt)
+	  sequences, to detect that we are returning to the correct context
+	  (user, kernel or guest). This adds some performance overhead.
+
+	  If unsure, say N.
+
 endmenu

arch/powerpc/include/asm/exception-64s.h

@@ -64,9 +64,7 @@
 	RFI_FLUSH_FIXUP_SECTION;					\
 	nop
 
-#define DEBUG_RFI
-
-#ifdef DEBUG_RFI
+#ifdef CONFIG_PPC_DEBUG_RFI
 #define CHECK_TARGET_MSR_PR(srr_reg, expected_pr)			\
 	SET_SCRATCH0(r3);						\
 	mfspr	r3,srr_reg;						\