powerpc: Enable GCOV

Make it possible to enable GCOV code coverage measurement on powerpc.

Lightly tested on 64-bit, seems to work as expected.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 035946f..720e8c3 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -115,6 +115,13 @@
 obj-y				+= ppc_save_regs.o
 endif
 
+# Disable GCOV in odd or sensitive code
+GCOV_PROFILE_prom_init.o := n
+GCOV_PROFILE_ftrace.o := n
+GCOV_PROFILE_machine_kexec_64.o := n
+GCOV_PROFILE_machine_kexec_32.o := n
+GCOV_PROFILE_kprobes.o := n
+
 extra-$(CONFIG_PPC_FPU)		+= fpu.o
 extra-$(CONFIG_ALTIVEC)		+= vector.o
 extra-$(CONFIG_PPC64)		+= entry_64.o