Update the linker file to support single and multiple heap banks

Author: Deepika

targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L475xG/device/TOOLCHAIN_GCC_ARM/STM32L475XX.ld

@@ -6,14 +6,14 @@
   #define MBED_APP_SIZE 1024k
 #endif
 
+M_CRASH_DATA_RAM_SIZE = 0x100;
+
 #if !defined(MBED_BOOT_STACK_SIZE)
     #define MBED_BOOT_STACK_SIZE 0x400
 #endif
 
 STACK_SIZE = MBED_BOOT_STACK_SIZE;
 
-M_CRASH_DATA_RAM_SIZE = 0x100;
-
 /* Linker script to configure memory regions. */
 MEMORY
 {
@@ -106,7 +106,7 @@ SECTIONS
         __CRASH_DATA_RAM_END__ = .; /* Define a global symbol at data end */
     } > SRAM2
 
-     /* .stack section doesn't contains any symbols. It is only
+    /* .stack section doesn't contains any symbols. It is only
      * used for linker to reserve space for the isr stack section
      * WARNING: .stack should come immediately after the last secure memory
      * section.  This provides stack overflow detection. */
@@ -124,6 +124,17 @@ SECTIONS
     __StackLimit = ADDR(.stack);
     PROVIDE(__stack = __StackTop);
 
+    /* Place holder for additional heap */
+    .heap_0 (COPY):
+    {
+        __mbed_sbrk_start_0 = .;
+        . += (ORIGIN(SRAM2) + LENGTH(SRAM2) - .);
+        __mbed_krbs_start_0 = .;
+    } > SRAM2
+
+    /* Check if heap exceeds SRAM2 */
+    ASSERT(__mbed_krbs_start_0 <= (ORIGIN(SRAM2)+LENGTH(SRAM2)), "Heap is too big for SRAM2")
+
     .data : AT (__etext)
     {
         __data_start__ = .;
@@ -144,6 +155,7 @@ SECTIONS
         KEEP(*(.init_array))
         PROVIDE_HIDDEN (__init_array_end = .);
 
+
         . = ALIGN(8);
         /* finit data */
         PROVIDE_HIDDEN (__fini_array_start = .);
@@ -156,6 +168,7 @@ SECTIONS
         /* All data end */
         __data_end__ = .;
         _edata = .;
+
     } > SRAM1
 
     /* Check if bss exceeds SRAM1 */
@@ -176,17 +189,18 @@ SECTIONS
     /* Check if bss exceeds SRAM1 */
     ASSERT(__bss_end__ <= (ORIGIN(SRAM1)+LENGTH(SRAM1)), "BSS is too big for SRAM1")
 
+    /* Placeholder for default single heap */
     .heap (COPY):
     {
         __end__ = .;
-        __mbed_sbrk_start_0 = .;
         end = __end__;
+        __mbed_sbrk_start = .;
         *(.heap*)
-        . = (ORIGIN(SRAM2) + LENGTH(SRAM2));
-        __mbed_krbs_start_0 = .;
-        __mbed_sbrk_start = __bss_end__;
-        . = (ORIGIN(SRAM1) + LENGTH(SRAM1));
+        . += (ORIGIN(SRAM1) + LENGTH(SRAM1) - .);
         __mbed_krbs_start = .;
         __HeapLimit = .;
-    } > SRAM2
+    } > SRAM1
+
+    /* Check if heap exceeds SRAM1 */
+    ASSERT(__HeapLimit <= (ORIGIN(SRAM1)+LENGTH(SRAM1)), "Heap is too big for SRAM1")
 }