FVP: Enable PIE for RESET_TO_BL31=1

This patch enabled PIE for FVP when RESET_TO_BL31=1. The references
to BL31_BASE are replaced by BL31_START as being a symbol exported by
the linker, will create a dynamic relocation entry in .rela.dyn and
hence will be fixed up by dynamic linker at runtime. Also, we disable
RECLAIM_INIT_CODE when PIE is enabled as the init section overlay
creates some static relocations which cannot be handled by the
dynamic linker currently.

Change-Id: I86df1b0a8b2a8bbbe7c3f3c0b9a08c86c2963ec0
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

plat/arm/board/fvp/platform.mk

@@ -202,7 +202,9 @@ ENABLE_AMU			:=	1
 DYNAMIC_WORKAROUND_CVE_2018_3639	:=	1
 
 # Enable reclaiming of BL31 initialisation code for secondary cores stacks for FVP
+ifneq (${RESET_TO_BL31},1)
 RECLAIM_INIT_CODE	:=	1
+endif
 
 ifeq (${ENABLE_AMU},1)
 BL31_SOURCES		+=	lib/cpus/aarch64/cortex_a75_pubsub.c	\

plat/arm/common/arm_bl31_setup.c

@@ -25,11 +25,13 @@
 static entry_point_info_t bl32_image_ep_info;
 static entry_point_info_t bl33_image_ep_info;
 
+#if !RESET_TO_BL31
 /*
  * Check that BL31_BASE is above ARM_TB_FW_CONFIG_LIMIT. The reserved page
  * is required for SOC_FW_CONFIG/TOS_FW_CONFIG passed from BL2.
  */
 CASSERT(BL31_BASE >= ARM_TB_FW_CONFIG_LIMIT, assert_bl31_base_overflows);
+#endif
 
 /* Weak definitions may be overridden in specific ARM standard platform */
 #pragma weak bl31_early_platform_setup2
@@ -38,8 +40,8 @@ CASSERT(BL31_BASE >= ARM_TB_FW_CONFIG_LIMIT, assert_bl31_base_overflows);
 #pragma weak bl31_plat_get_next_image_ep_info
 
 #define MAP_BL31_TOTAL		MAP_REGION_FLAT(			\
-					BL31_BASE,			\
-					BL31_END - BL31_BASE,		\
+					BL31_START,			\
+					BL31_END - BL31_START,		\
 					MT_MEMORY | MT_RW | MT_SECURE)
 #if RECLAIM_INIT_CODE
 IMPORT_SYM(unsigned long, __INIT_CODE_START__, BL_INIT_CODE_BASE);

plat/arm/common/arm_common.mk

@@ -130,6 +130,11 @@ ARM_CRYPTOCELL_INTEG		:=	0
 $(eval $(call assert_boolean,ARM_CRYPTOCELL_INTEG))
 $(eval $(call add_define,ARM_CRYPTOCELL_INTEG))
 
+# Enable PIE support for RESET_TO_BL31 case
+ifeq (${RESET_TO_BL31},1)
+    ENABLE_PIE			:=	1
+endif
+
 # CryptoCell integration relies on coherent buffers for passing data from
 # the AP CPU to the CryptoCell
 ifeq (${ARM_CRYPTOCELL_INTEG},1)