feat(plat/arm): enable PIE when RESET_TO_SP_MIN=1

For Arm platforms PIE is enabled when RESET_TO_BL31=1 in aarch64 mode on
the similar lines enable PIE when RESET_TO_SP_MIN=1 in aarch32 mode.
The underlying changes for enabling PIE in aarch32 is submitted in
commit 4324a14bf

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: Ib8bb860198b3f97cdc91005503a3184d63e15469

docs/plat/arm/fvp/index.rst

@@ -526,8 +526,8 @@ with 8 CPUs using the AArch64 build of TF-A.
 
 Notes:
 
--  If Position Independent Executable (PIE) support is enabled for BL31
-   in this config, it can be loaded at any valid address for execution.
+-  Position Independent Executable (PIE) support is enabled in this
+   config allowing BL31 to be loaded at any valid address for execution.
 
 -  Since a FIP is not loaded when using BL31 as reset entrypoint, the
    ``--data="<path-to><bl31|bl32|bl33-binary>"@<base-address-of-binary>``
@@ -588,8 +588,8 @@ with 8 CPUs using the AArch32 build of TF-A.
     --data cluster0.cpu0="<path-to>/<ramdisk>"@0x84000000
 
 .. note::
-   The load address of ``<bl32-binary>`` depends on the value ``BL32_BASE``.
-   It should match the address programmed into the RVBAR register as well.
+   Position Independent Executable (PIE) support is enabled in this
+   config allowing SP_MIN to be loaded at any valid address for execution.
 
 Running on the Cortex-A57-A53 Base FVP with reset to BL31 entrypoint
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

include/plat/arm/common/arm_def.h

@@ -465,12 +465,16 @@
  * BL32 specific defines for EL3 runtime in AArch32 mode
  ******************************************************************************/
 # if RESET_TO_SP_MIN && !JUNO_AARCH32_EL3_RUNTIME
+/* Ensure Position Independent support (PIE) is enabled for this config.*/
+# if !ENABLE_PIE
+#  error "BL32 must be a PIE if RESET_TO_SP_MIN=1."
+#endif
 /*
- * SP_MIN is the only BL image in SRAM. Allocate the whole of SRAM (excluding
- * the page reserved for fw_configs) to BL32
+ * Since this is PIE, we can define BL32_BASE to 0x0 since this macro is solely
+ * used for building BL32 and not used for loading BL32.
  */
-#  define BL32_BASE			ARM_FW_CONFIGS_LIMIT
-#  define BL32_LIMIT			(ARM_BL_RAM_BASE + ARM_BL_RAM_SIZE)
+#  define BL32_BASE			0x0
+#  define BL32_LIMIT			PLAT_ARM_MAX_BL32_SIZE
 # else
 /* Put BL32 below BL2 in the Trusted SRAM.*/
 #  define BL32_BASE			((ARM_BL_RAM_BASE + ARM_BL_RAM_SIZE)\

plat/arm/board/fvp/include/platform_def.h

@@ -150,12 +150,18 @@
 #endif /* RESET_TO_BL31 */
 
 #ifndef __aarch64__
+#if RESET_TO_SP_MIN
+/* Size of Trusted SRAM - the first 4KB of shared memory */
+#define PLAT_ARM_MAX_BL32_SIZE		(PLAT_ARM_TRUSTED_SRAM_SIZE - \
+					 ARM_SHARED_RAM_SIZE)
+#else
 /*
  * Since BL32 NOBITS overlays BL2 and BL1-RW, PLAT_ARM_MAX_BL32_SIZE is
  * calculated using the current SP_MIN PROGBITS debug size plus the sizes of
  * BL2 and BL1-RW
  */
 # define PLAT_ARM_MAX_BL32_SIZE		UL(0x3B000)
+#endif /* RESET_TO_SP_MIN */
 #endif
 
 /*

plat/arm/common/arm_common.mk

@@ -154,9 +154,9 @@ 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 (${RESET_TO_BL31},1)
-    ENABLE_PIE			:=	1
+# Enable PIE support for RESET_TO_BL31/RESET_TO_SP_MIN case
+ifneq ($(filter 1,${RESET_TO_BL31} ${RESET_TO_SP_MIN}),)
+	ENABLE_PIE			:=	1
 endif
 
 # CryptoCell integration relies on coherent buffers for passing data from

plat/arm/common/sp_min/arm_sp_min_setup.c

@@ -32,7 +32,9 @@ static entry_point_info_t bl33_image_ep_info;
  * Check that BL32_BASE is above ARM_FW_CONFIG_LIMIT. The reserved page
  * is required for SOC_FW_CONFIG/TOS_FW_CONFIG passed from BL2.
  */
+#if !RESET_TO_SP_MIN
 CASSERT(BL32_BASE >= ARM_FW_CONFIG_LIMIT, assert_bl32_base_overflows);
+#endif
 
 /*******************************************************************************
  * Return a pointer to the 'entry_point_info' structure of the next image for the