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>

arch/powerpc/kernel/Makefile

@@ -115,6 +115,13 @@ ifneq ($(CONFIG_XMON)$(CONFIG_KEXEC),)
 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

arch/powerpc/kernel/vdso32/Makefile

@@ -12,6 +12,7 @@ endif
 targets := $(obj-vdso32) vdso32.so vdso32.so.dbg
 obj-vdso32 := $(addprefix $(obj)/, $(obj-vdso32))
 
+GCOV_PROFILE := n
 
 EXTRA_CFLAGS := -shared -fno-common -fno-builtin
 EXTRA_CFLAGS += -nostdlib -Wl,-soname=linux-vdso32.so.1 \

arch/powerpc/kernel/vdso64/Makefile

@@ -7,6 +7,8 @@ obj-vdso64 = sigtramp.o gettimeofday.o datapage.o cacheflush.o note.o
 targets := $(obj-vdso64) vdso64.so vdso64.so.dbg
 obj-vdso64 := $(addprefix $(obj)/, $(obj-vdso64))
 
+GCOV_PROFILE := n
+
 EXTRA_CFLAGS := -shared -fno-common -fno-builtin
 EXTRA_CFLAGS += -nostdlib -Wl,-soname=linux-vdso64.so.1 \
 		$(call ld-option, -Wl$(comma)--hash-style=sysv)

arch/powerpc/xmon/Makefile

@@ -2,6 +2,8 @@
 
 subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror
 
+GCOV_PROFILE := n
+
 ifdef CONFIG_PPC64
 EXTRA_CFLAGS += -mno-minimal-toc
 endif

kernel/gcov/Kconfig

@@ -34,7 +34,7 @@ config GCOV_KERNEL
 config GCOV_PROFILE_ALL
 	bool "Profile entire Kernel"
 	depends on GCOV_KERNEL
-	depends on S390 || X86
+	depends on S390 || X86 || (PPC && EXPERIMENTAL)
 	default n
 	---help---
 	This options activates profiling for the entire kernel.