From d0f42d43ae9afe9ea4084afd030045a3b6484cc4 Mon Sep 17 00:00:00 2001
From: Matte23 <matteo.schiff23@gmail.com>
Date: Sun, 3 Nov 2024 19:41:58 +0100
Subject: [PATCH] Define heap in linker and place other sections correctly

---
 linker.ld  | 45 +++++++++++++++++++++++++++++++++++----------
 os/alloc.c | 10 ++++++----
 os/alloc.h |  5 +++++
 3 files changed, 46 insertions(+), 14 deletions(-)

diff --git a/linker.ld b/linker.ld
index 8b92698..de6a3a2 100644
--- a/linker.ld
+++ b/linker.ld
@@ -1,15 +1,40 @@
 ENTRY(_start)
 
+MEMORY
+{
+    FLASH  (rx)  : ORIGIN = 0x00000000, LENGTH = 1M
+    RAM  (rwx) : ORIGIN = 0x20000000, LENGTH = 128K
+}
+
+_Min_Heap_Size = 0x200 ;
+_Min_Stack_Size = 0x200 ;       /* Required amount of stack.  Used by main(), then re-used as the interrupt stack after the kernel starts. */
+_estack = ORIGIN(RAM) + LENGTH(RAM);
+
+
 SECTIONS
 {
-    /* text section (code)*/
-    .text : { *(.text*) }
-    /* data section, initialized variables */
-    .data : { *(.data) }
-    ram_start = 0x20000000;
-    /* bss section, uninitialized variables */
-    .bss : { *(.bss*) }
-    /* stack section */
-    /* The stack is placed at the end of the RAM */
-    stack_top = 0x2001ffff;
+	.text : { *(.text*) } 		> FLASH
+	.rodata  : { *(.rodata*) }	> FLASH
+	.bss  : { *(.bss*) }		> RAM
+	.data  : { *(.data*) }		> RAM
+	.heap : {
+		. = ALIGN(8);
+        PROVIDE ( end = . );
+        PROVIDE ( _end = . );
+        _heap_bottom = .;
+        . = . + _Min_Heap_Size;
+        _heap_top = .;
+        . = . + _Min_Stack_Size;
+		. = ALIGN(8);
+	} >RAM
+
+	.stack (NOLOAD) :  {
+		. = ORIGIN(RAM) + LENGTH(RAM);
+		stack_top = .;
+	} > RAM
+
+	__StackLimit = stack_top - _Min_Stack_Size;
+
+	/* Check if data + heap + stack exceeds RAM limit */
+	ASSERT(__StackLimit >= _heap_top, "region RAM overflowed with stack")
 }
diff --git a/os/alloc.c b/os/alloc.c
index c2af1b5..b874543 100644
--- a/os/alloc.c
+++ b/os/alloc.c
@@ -1,14 +1,16 @@
 #include "alloc.h"
 #include "stdint.h"
 
-void* *first_mem_avail = (void*) 0x20000000;
+HeapArena heap_arena;
+
+extern void * _heap_top;
 
 void init_allocator() {
-    *first_mem_avail = (void*) 0x20000000 +sizeof(void*);
+    heap_arena.wilderness = &_heap_top;
 }
 
 void* malloc(size_t size) {
-    void* block = *first_mem_avail;
-    *first_mem_avail += size;
+    void* block = heap_arena.wilderness;
+    heap_arena.wilderness += size;
     return block;
 }
diff --git a/os/alloc.h b/os/alloc.h
index bfe4861..9b29577 100644
--- a/os/alloc.h
+++ b/os/alloc.h
@@ -1,4 +1,9 @@
 #include <stddef.h>
+#include <stdint.h>
+
+typedef struct {
+    void * wilderness;
+} HeapArena;
 
 void init_allocator();
 void* malloc (size_t size);