From 1376ad96d41b271555aca3c5b260ea7e480b495c Mon Sep 17 00:00:00 2001
From: vanten-s <vanten-s@vanten-s.com>
Date: Sat, 10 Aug 2024 03:49:28 +0200
Subject: [PATCH] Added a simple malloc/free

---
 Makefile              |  1 +
 include/kernel/heap.h | 19 +++++++++++++
 kernel/heap.c         | 65 ++++++++++++++++++++++++++++++++++++++++++-
 kernel/kernel.c       |  6 +++-
 4 files changed, 89 insertions(+), 2 deletions(-)
 create mode 100644 include/kernel/heap.h

diff --git a/Makefile b/Makefile
index 2c06c83..680ec92 100644
--- a/Makefile
+++ b/Makefile
@@ -24,6 +24,7 @@ kernel/debugging.o \
 kernel/elf.o \
 kernel/syscall.o \
 kernel/keyboard.o \
+kernel/heap.o \
 
 LIB_OBJS=\
 $(ARCHDIR)/bootstrap.o \
diff --git a/include/kernel/heap.h b/include/kernel/heap.h
new file mode 100644
index 0000000..3a3ae47
--- /dev/null
+++ b/include/kernel/heap.h
@@ -0,0 +1,19 @@
+#include <stddef.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+struct Heap_Metadata {
+    struct Heap_Block* start;
+    size_t size;
+};
+
+struct Heap_Block {
+    struct Heap_Block* next;
+    size_t size;
+    bool used;
+    void* data;
+};
+
+void heap_init();
+void* malloc(size_t size);
+void free(void *ptr);
diff --git a/kernel/heap.c b/kernel/heap.c
index 6518014..3ec7641 100644
--- a/kernel/heap.c
+++ b/kernel/heap.c
@@ -1,3 +1,66 @@
 #include <stdint.h>
 
-uint8_t heap[2000];
+#include <kernel/heap.h>
+#include <debugging.h>
+
+#define HEAP_SIZE (256 * 4096)
+
+uint8_t* global_heap_data[HEAP_SIZE];
+struct Heap_Metadata global_heap;
+
+void heap_init() 
+{
+    global_heap.size = HEAP_SIZE;
+    global_heap.start = (struct Heap_Block*) global_heap_data;
+
+    struct Heap_Block* start = global_heap.start;
+    start->size = HEAP_SIZE;
+    start->used = false;
+    start->data = start + 1;
+    start->next = 0;
+}
+
+void* malloc(size_t size)
+{
+    struct Heap_Block* current = global_heap.start;
+    
+    while (true) {
+        if (current->used || current->size < size) { 
+            current = current->next; 
+            continue; 
+        }
+
+        if (current == 0) {
+            return 0;
+        }
+
+        struct Heap_Block* next = current->data + size;
+
+        next->next = current->next;
+        next->size = current->size - size - sizeof(struct Heap_Block);
+        next->data = next + 1;
+
+        current->next = next;
+        current->size = size;
+        current->used = true;
+
+        return current->data;
+    }
+}
+
+void free(void *ptr)
+{
+    struct Heap_Block* current = global_heap.start;
+    while (current->data != ptr) { current = current->next; }
+
+    struct Heap_Block* start = current;
+
+    current->used = false;
+
+    while (current->used == false) {
+        current = current->next;
+    }
+    start->next = current;
+    start->size = (uint32_t)start->next - (uint32_t)start->data;
+}
+
diff --git a/kernel/kernel.c b/kernel/kernel.c
index 1f9e0d1..ca324a5 100644
--- a/kernel/kernel.c
+++ b/kernel/kernel.c
@@ -1,8 +1,10 @@
 #include <kernel/tty.h>
 #include <kernel/idt.h>
-#include <debugging.h>
 #include <kernel/elf.h>
 #include <kernel/pic.h>
+#include <kernel/heap.h>
+
+#include <debugging.h>
 
 /* Check if the compiler thinks you are targeting the wrong operating system. */
 #if defined(__linux__)
@@ -25,5 +27,7 @@ void kernel_main(void)
 
     init_pic();
     idt_init();
+    heap_init();
+
     run_program(program, sizeof(program));
 }