added bad malloc

Makefile

@@ -3,7 +3,7 @@ GCCPATH = /opt/gcc-arm/bin
 CC 			= $(GCCPATH)/aarch64-none-elf-gcc
 LD 			= $(GCCPATH)/aarch64-none-elf-ld
 OBJCOPY 	= $(GCCPATH)/aarch64-none-elf-objcopy
-GCCFLAGS 	= -Wall -O2 -ffreestanding -nostdinc -nostdlib -nostartfiles
+GCCFLAGS 	= -Wall -O2 -ffreestanding -fno-builtin -nostdinc -nostdlib -nostartfiles 
 
 OUTDIR = ./out/bin
 

include/memory.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#define NULL ((void*)0)
+
+void heap_init();
+
+void* malloc();
+void free(void* ptr);

src/convert.c

@@ -1,5 +1,6 @@
 #include "convert.h"
 #include "io.h"
+#include "memory.h"
 
 int stoi(const char* string)
 {
@@ -29,7 +30,9 @@ char* ultoa(unsigned long number, char* string, int base)
         return string;
     }
 
-    volatile char* temp = (volatile char*)0x40000000;
+    char* buffer = (char*)malloc();
+    char* temp = buffer;
+
     int i = 0;
     if(number == 0)
     {
@@ -39,7 +42,12 @@ char* ultoa(unsigned long number, char* string, int base)
     {
         for(; number > 0; number /= base)
         {
-            temp[i++] = '0' + (number % base);
+            uint8_t digit = number % base;
+
+            if(digit < 10)
+                temp[i++] = '0' + digit;
+            else
+                temp[i++] = 'A' + digit;
         }
     }
 
@@ -51,6 +59,7 @@ char* ultoa(unsigned long number, char* string, int base)
         string[--i] = *temp++;
     }
 
+    free(buffer);
     return string;
 }
 

src/kernel.c

@@ -1,6 +1,7 @@
 #include "io.h"
 #include "convert.h"
 #include "string.h"
+#include "memory.h"
 
 void print_clippy();
 char* get_user_input(char* buffer);
@@ -12,7 +13,8 @@ void main()
     char buffer[1024];
 
     uart_init();
-    
+    heap_init();
+
     print_clippy();
     uart_puts("Boot successful! \n");
     uart_puts("Started execution at 0x");

src/memory.c

@@ -0,0 +1,70 @@
+#include "memory.h"
+
+#include "stdint.h"
+#include "io.h"
+#include "convert.h"
+
+struct FreeBlock
+{
+    struct FreeBlock* next;
+};
+
+#define HEAP_BASE ((void*)0x40000000)
+#define BLOCK_SIZE 4096
+#define MAGIC_NUMBER 0xDEADBEEF
+
+static struct FreeBlock* head = (struct FreeBlock*)HEAP_BASE;
+
+void heap_init()
+{
+    head->next = NULL;
+}
+
+void* malloc()
+{
+    void* block = (void*)head;
+
+    if(head->next == NULL)
+    {
+        head += BLOCK_SIZE;
+        head->next = NULL;
+    }
+    else
+    {
+        head = head->next;
+    }
+
+    *(uint32_t*)block = MAGIC_NUMBER;
+    return block + sizeof(uint32_t);
+}
+
+void free(void* ptr)
+{
+    void* blockStart = ptr - sizeof(uint32_t);
+    if(*(uint32_t*)blockStart != MAGIC_NUMBER)
+        return;
+
+    if((struct FreeBlock*)blockStart < head)
+    {
+        struct FreeBlock* nextBlock = head->next;
+        head = blockStart;
+        head->next = nextBlock;
+        return;
+    }
+
+    struct FreeBlock* block = head;
+
+    while(block)
+    {
+        if(block < (struct FreeBlock*)blockStart && (struct FreeBlock*)blockStart < block->next)
+        {
+            struct FreeBlock* newBlock = (struct FreeBlock*)blockStart;
+            newBlock->next = block->next;
+            block->next = newBlock;
+
+            return;
+        }
+
+        block = block->next;
+    }
+}