fvp: Reuse BL1 and BL2 memory through image overlaying

This patch re-organizes the memory layout on FVP as to give the
BL3-2 image as much memory as possible.

Considering these two facts:
 - not all images need to live in memory at the same time. Once
   in BL3-1, the memory used by BL1 and BL2 can be reclaimed.
 - when BL2 loads the BL3-1 and BL3-2 images, it only considers the
   PROGBITS sections of those 2 images. The memory occupied by the
   NOBITS sections will be touched only at execution of the BL3-x
   images;
Then it is possible to choose the different base addresses such that
the NOBITS sections of BL3-1 and BL3-2 overlay BL1 and BL2.

On FVP we choose to put:
 - BL1 and BL3-1 at the top of the Trusted RAM, with BL3-1 NOBITS
   sections overlaying BL1;
 - BL3-2 at the bottom of the Trusted RAM, with its NOBITS sections
   overlaying BL2;

This is illustrated by the following diagram:

0x0404_0000 ------------    ------------------
            |   BL1    | <= |  BL3-1 NOBITS  |
            ---...

bl31/bl31.ld.S

@@ -75,6 +75,10 @@ SECTIONS
         __DATA_END__ = .;
     } >RAM
 
+#ifdef BL31_PROGBITS_LIMIT
+    ASSERT(. <= BL31_PROGBITS_LIMIT, "BL3-1 progbits has exceeded its limit.")
+#endif
+
     stacks (NOLOAD) : {
         __STACKS_START__ = .;
         *(tzfw_normal_stacks)

bl32/tsp/tsp.ld.S

@@ -68,6 +68,10 @@ SECTIONS
         __DATA_END__ = .;
     } >RAM
 
+#ifdef BL32_PROGBITS_LIMIT
+    ASSERT(. <= BL32_PROGBITS_LIMIT, "BL3-2 progbits has exceeded its limit.")
+#endif
+
     stacks (NOLOAD) : {
         __STACKS_START__ = .;
         *(tzfw_normal_stacks)

plat/fvp/include/platform_def.h

@@ -101,24 +101,33 @@
  ******************************************************************************/
 #define BL1_RO_BASE			TZROM_BASE
 #define BL1_RO_LIMIT			(TZROM_BASE + TZROM_SIZE)
-#define BL1_RW_BASE			TZRAM_BASE
-#define BL1_RW_LIMIT			BL31_BASE
+/*
+ * Put BL1 RW at the top of the Trusted SRAM. BL1_RW_BASE is calculated using
+ * the current BL1 RW debug size plus a little space for growth.
+ */
+#define BL1_RW_BASE			(TZRAM_BASE + TZRAM_SIZE - 0x6000)
+#define BL1_RW_LIMIT			(TZRAM_BASE + TZRAM_SIZE)
 
 /*******************************************************************************
  * BL2 specific defines.
  ******************************************************************************/
-#define BL2_BASE			(TZRAM_BASE + TZRAM_SIZE - 0xc000)
-#define BL2_LIMIT			(TZRAM_BASE + TZRAM_SIZE)
+/*
+ * Put BL2 just below BL3-1. BL2_BASE is calculated using the current BL2 debug
+ * size plus a little space for growth.
+ */
+#define BL2_BASE			(BL31_BASE - 0xC000)
+#define BL2_LIMIT			BL31_BASE
 
 /*******************************************************************************
  * BL31 specific defines.
  ******************************************************************************/
-#define BL31_BASE			(TZRAM_BASE + 0x6000)
-#if TSP_RAM_LOCATION_ID == TSP_IN_TZRAM
-#define BL31_LIMIT			BL32_BASE
-#elif TSP_RAM_LOCATION_ID == TSP_IN_TZDRAM
-#define BL31_LIMIT			BL2_BASE
-#endif
+/*
+ * Put BL3-1 at the top of the Trusted SRAM. BL31_BASE is calculated using the
+ * current BL3-1 debug size plus a little space for growth.
+ */
+#define BL31_BASE			(TZRAM_BASE + TZRAM_SIZE - 0x1D000)
+#define BL31_PROGBITS_LIMIT		BL1_RW_BASE
+#define BL31_LIMIT			(TZRAM_BASE + TZRAM_SIZE)
 
 /*******************************************************************************
  * BL32 specific defines.
@@ -132,8 +141,9 @@
 #if TSP_RAM_LOCATION_ID == TSP_IN_TZRAM
 # define TSP_SEC_MEM_BASE		TZRAM_BASE
 # define TSP_SEC_MEM_SIZE		TZRAM_SIZE
-# define BL32_BASE			(TZRAM_BASE + TZRAM_SIZE - 0x1c000)
-# define BL32_LIMIT			BL2_BASE
+# define BL32_BASE			TZRAM_BASE
+# define BL32_PROGBITS_LIMIT		BL2_BASE
+# define BL32_LIMIT			BL31_BASE
 #elif TSP_RAM_LOCATION_ID == TSP_IN_TZDRAM
 # define TSP_SEC_MEM_BASE		TZDRAM_BASE
 # define TSP_SEC_MEM_SIZE		TZDRAM_SIZE