Make malloc actually use the correct region

arch/at91sam3x8e/config.ld

@@ -2,10 +2,10 @@
 /* See the end of this file for copyright, licensing, and warranty information. */
 
 /*
- * stack size is 32K (uses the entire sram1 bank)
+ * stack size is 8K
  * TODO: modify flash.ld to actually align this properly
  */
-STACK_SIZE = 0x8000;
+STACK_SIZE = 0x2000;
 
 /*
  * Copyright (c) 2020 Felix Kopp <sandtler@sandtler.club>

arch/at91sam3x8e/flash.ld

@@ -141,4 +141,7 @@ SECTIONS
 
     . = ALIGN(4);
     _end = . ;
+
+    _sheap = .;
+    _eheap = ORIGIN(ram) + LENGTH(ram) - 4;
 }

arch/at91sam3x8e/startup.c

@@ -16,9 +16,10 @@ extern uint32_t _srelocate;	/* relocate (.data) start */
 extern uint32_t _erelocate;	/* relocate end */
 extern uint32_t _szero;		/* zero area (.bss) start */
 extern uint32_t _ezero;		/* zero area end */
-/* the entire heap sits in between _ezero and _sstack */
 extern uint32_t _sstack;	/* stack start */
 extern uint32_t _estack;	/* stack end */
+extern uint32_t _sheap;		/* heap start */
+extern uint32_t _eheap;		/* heap end */
 
 /* implementation in init/main.c */
 void do_bootstrap(void);
@@ -38,8 +39,8 @@ void irq_reset(void)
 
 	/* There is no userspace yet, so the Kernel gets the entire heap for now */
 	malloc_init(
-		&_ezero + sizeof(void *),
-		(size_t)(&_sstack) - (size_t)(&_ezero) - sizeof(void *)
+		&_sheap,
+		(size_t)(&_sheap) - (size_t)(&_sheap)
 	);
 
 	/* start the Kernel */