rpi3: Add support for the stack protector

It uses the hardware RNG in a similar way as Juno (it gets 128 bits of
entropy and does xor on them).

It is disabled by default.

Change-Id: I8b3adb61f5a5623716e0e8b6799404c68dd94c60
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/plat/rpi3/platform.mk b/plat/rpi3/platform.mk
index 3ad7114..2f18af6 100644
--- a/plat/rpi3/platform.mk
+++ b/plat/rpi3/platform.mk
@@ -90,6 +90,9 @@
 # Disable the PSCI platform compatibility layer by default
 ENABLE_PLAT_COMPAT		:= 0
 
+# Disable stack protector by default
+ENABLE_STACK_PROTECTOR	 	:= 0
+
 # Reset to BL31 isn't supported
 RESET_TO_BL31			:= 0
 
@@ -146,6 +149,11 @@
   $(error Error: AArch32 not supported on rpi3)
 endif
 
+ifneq ($(ENABLE_STACK_PROTECTOR), 0)
+PLAT_BL_COMMON_SOURCES	+=	plat/rpi3/rpi3_rng.c			\
+				plat/rpi3/rpi3_stack_protector.c
+endif
+
 ifeq (${SPD},opteed)
 BL2_SOURCES	+=							\
 		lib/optee/optee_utils.c