Linkage: Put the stack at the end of the CCM

Makefile

@@ -21,7 +21,7 @@ test: test.elf
 	$(GDB) -x test/gdb_script.gdb test.elf
 
 test.elf: $(objs) test/runner.o
-	@$(LD) -T boot/stm32f429_flash.ld $(objs) test/runner.o -o $@
+	@$(LD) -T boot/stm32f429.ld $(objs) test/runner.o -o $@
 
 boot.hex: boot.elf
 	@echo "OBJCOPY $@"
@@ -33,7 +33,7 @@ boot.bin: boot.elf
 
 boot.elf: $(objs) src/freertos_blinky.o
 	@echo "LD      $@"
-	@$(LD) -T boot/stm32f429_flash.ld $(objs) src/freertos_blinky.o -o $@
+	@$(LD) -T boot/stm32f429.ld $(objs) src/freertos_blinky.o -o $@
 
 %.o: %.c
 	@echo "CC      $@"

boot/crt0.c

@@ -7,6 +7,8 @@ extern const void * _data_section_start_ram;
 extern const void * _data_section_end_ram;
 extern const void * _bss_section_start_ram;
 extern const void * _bss_section_end_ram;
+extern const void * _stack_start;
+extern const void * _stack_end;
 
 void _start(void);
 
@@ -24,7 +26,7 @@ typedef void(*ISR)(void);
 ISR InitialisationVector[INITIALISATION_VECTOR_SIZE]
   __attribute__((section(".isr_vector_table")))
   = {
-  0x2001FFF0, //FIXME: This is the stack pointer!
+  (ISR)&_stack_start,
   _start,
   0,
   0,

boot/stm32f429.ld

@@ -10,8 +10,11 @@
  * to be stored in Flash. */
 MEMORY {
   FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 2048K
-  RAM (rwx)  : ORIGIN = 0x20000000, LENGTH = 192K
-  CCM (rwx)  : ORIGIN = 0x10000000, LENGTH = 64K
+  RAM (rwx) : ORIGIN = 0x20000000, LENGTH = 192K
+  /* We're splitting the CCM in two, this way we're sure nothing will use the
+   * stack space. */
+  CCM (rwx) : ORIGIN = 0x10000000, LENGTH = 60K
+  CCM_STACK (rw) : ORIGIN = 0x1000F000, LENGTH = 4K
 }
 
 SECTIONS {
@@ -33,7 +36,6 @@ SECTIONS {
     *(.isr_vector_table)
   } >FLASH
 
-
   .text : {
     . = ALIGN(4);
     *(.text)
@@ -76,4 +78,12 @@ SECTIONS {
     *(.bss)
     _bss_section_end_ram = .;
   } >RAM
+
+  .ccm : {
+    . = ALIGN(8);
+    _stack_end = .;
+    . = . + LENGTH(CCM_STACK) - 8;
+    . = ALIGN(8);
+    _stack_start = .;
+  } >CCM_STACK
 }