uprobes/powerpc: Add dependency on single step emulation

Uprobes uses emulate_step in sstep.c, but we haven't explicitly specified
the dependency. On pseries HAVE_HW_BREAKPOINT protects us, but 44x has no
such luxury.

Consolidate other users that depend on sstep and create a new config option.
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com>
Cc: linuxppc-dev@ozlabs.org
Cc: stable@vger.kernel.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/Kconfig

@@ -276,6 +276,10 @@ config PPC_ADV_DEBUG_DAC_RANGE
 	depends on PPC_ADV_DEBUG_REGS && 44x
 	default y
 
+config PPC_EMULATE_SSTEP
+	bool
+	default y if KPROBES || UPROBES || XMON || HAVE_HW_BREAKPOINT
+
 source "init/Kconfig"
 
 source "kernel/Kconfig.freezer"

arch/powerpc/lib/Makefile

@@ -19,9 +19,7 @@ obj-$(CONFIG_PPC64)	+= copypage_64.o copyuser_64.o \
 			   checksum_wrappers_64.o hweight_64.o \
 			   copyuser_power7.o string_64.o copypage_power7.o \
 			   memcpy_power7.o
-obj-$(CONFIG_XMON)	+= sstep.o ldstfp.o
-obj-$(CONFIG_KPROBES)	+= sstep.o ldstfp.o
-obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= sstep.o ldstfp.o
+obj-$(CONFIG_PPC_EMULATE_SSTEP)	+= sstep.o ldstfp.o
 
 ifeq ($(CONFIG_PPC64),y)
 obj-$(CONFIG_SMP)	+= locks.o