Added mising sections to the linker.ld file.

Added the bss, heap and stack sections.

linker.ld

@@ -10,6 +10,14 @@
  */
 ENTRY(Reset_Handler)
 
+/* Highest address of user mode stack */
+_estack  = ORIGIN(RAM) + LENGTH(RAM); /* end of "RAM" Ram type memory */
+
+/* Generate a link error if heap and stack don't fit into RAM */
+_Min_Heap_Size = 0x200; /* required amount of heap. */
+_Min_Stack_Size = 0x400; /* required amount of stack. */
+
+
 
 /*
  * FORMAT:
@@ -34,11 +42,14 @@ MEMORY
     SRAM(rwx): ORIGIN = 0x20000000, LENGTH = 20K
 }
 
+/* VMA: virtual memory address.*/
+/* LMA: Load memory address. */
+
 floating_point = 0;
 SECTIONS
 {
     /* Code section, mapped to Flash memory */
-    .tect :
+    .text :
     {
         KEEP(*(.isr_vector))    /* Vector table, which must be at the beginning of Flash*/
         *(.text)                /* All code goes here */
@@ -53,6 +64,36 @@ SECTIONS
         *(.data)                    /* Initialized data */
         _edata = .;                 /* End of data section */
     } > RAM AT > FLASH
+
+    /* BSS: Placed in SRAM memory types. */
+    .bss :
+    {
+        _sbss = .;                  /* */
+        *(.bss)                     /**/
+        *(COMMON)                   /**/
+        _ebss = .;                  /**/
+    } > RAM
+
+    /* Stack Section: */
+    ._stack :
+    {
+        . = ALIGN(8);               /**/
+        _estack = .;                /**/
+        . = . + 2048;               /**/
+        _sstack = .;                /**/
+    } > RAM
+
+    /* Heap Section: */
+    .heap :
+    {
+        _sheap = .;                 /**/
+        . = . + 2048;               /**/
+        _eheap = .;                 /**/
+    } > RAM
 }
 
-
+/* Provide symbols to be used in the startup code */
+PROVIDE(_stack_start = _sstack);
+PROVIDE(_stack_end = _estack);
+PROVIDE(_heap_start = _sheap);
+PROVIDE(_heap_end = _eheap);