From cd2c4e4a25cb41ca6fe622f0ccf1b1a3dd9d5660 Mon Sep 17 00:00:00 2001
From: Carlos Maiolino <cem@toxiclabs.cc>
Date: Sun, 14 Sep 2025 14:18:41 +0200
Subject: Add a kernel heap

Use the heap API to implement a 100MiB heap to
be used by the kernel code.

Add example usage to src/kernel.c

Signed-off-by: Carlos Maiolino <cem@toxiclabs.cc>
---
 src/include/mm/kernel_heap.h | 20 ++++++++++++++++++++
 src/kernel.c                 | 15 +++++++++++++++
 src/mm/kernel_heap.c         | 35 +++++++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+)
 create mode 100644 src/include/mm/kernel_heap.h
 create mode 100644 src/mm/kernel_heap.c

diff --git a/src/include/mm/kernel_heap.h b/src/include/mm/kernel_heap.h
new file mode 100644
index 0000000..4527a11
--- /dev/null
+++ b/src/include/mm/kernel_heap.h
@@ -0,0 +1,20 @@
+#ifndef KERNEL_HEAP_H
+#define KERNEL_HEAP_H
+
+#include <mm/heap.h>
+
+#define KERNEL_HEAP_SIZE_BYTES	(1024 * 1024 * 100)  /* 100 MiB */
+#define KERNEL_HEAP_ENTRIES (KERNEL_HEAP_SIZE_BYTES / PAGE_SIZE)
+
+/* Addresses taken from OSDev x86 memory map */
+#define KERNEL_HEAP_ADDR	(0x01000000)
+
+/* This should give us 480.5 kiB, enough for the current table size */
+#define KERNEL_HEAP_TBL_ADDR	(0x00007E00)
+
+
+void kernel_heap_init();
+void * kmalloc(size_t size);
+void kfree(void *ptr);
+
+#endif /* KERNEL_HEAP_H */
diff --git a/src/kernel.c b/src/kernel.c
index 8a8bd61..cd9f9d7 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -5,6 +5,7 @@
 #include <toxic/kernel.h>
 #include <toxic/idt.h>
 #include <toxic/io.h>
+#include <mm/kernel_heap.h>
 
 void start_kernel()
 {
@@ -12,6 +13,20 @@ void start_kernel()
 	vprintl("Hello World!!!\n");
 	vprintl("Testing it!!!\n");
 
+	kernel_heap_init();
 	interrupts_init();
 
+
+	void *ptr = kmalloc(50);
+	void *ptr2 = kmalloc(5000);
+	void *ptr3 = kmalloc(5600);
+
+	*((int *)ptr) = 11;
+	kfree(ptr);
+	void *ptr4 = kmalloc(50);
+
+	*((int *)ptr2) = 22;
+	*((int *)ptr3) = 33;
+	*((int *)ptr4) = 44;
+	if (ptr || ptr2 || ptr3 || ptr4) {}
 }
diff --git a/src/mm/kernel_heap.c b/src/mm/kernel_heap.c
new file mode 100644
index 0000000..e53057c
--- /dev/null
+++ b/src/mm/kernel_heap.c
@@ -0,0 +1,35 @@
+#include <mm/kernel_heap.h>
+#include <mm/heap.h>
+#include <toxic/config.h>
+#include <toxic/vga.h>
+
+struct heap kernel_heap;
+
+struct heap_table kernel_heap_table;
+
+void
+kernel_heap_init()
+{
+	int ret;
+	void *end = (void *)(KERNEL_HEAP_ADDR + KERNEL_HEAP_SIZE_BYTES);
+
+	kernel_heap_table.entries = (unsigned char *)KERNEL_HEAP_TBL_ADDR;
+	kernel_heap_table.count = KERNEL_HEAP_ENTRIES;
+
+	ret = heap_create(&kernel_heap,
+			  (void *)KERNEL_HEAP_ADDR,
+			  end,
+			  &kernel_heap_table);
+
+	if (ret < 0)
+		vprintl("Failed to create kernel's heap\n");
+}
+
+void * kmalloc(size_t size)
+{
+	return heap_malloc(&kernel_heap, size);
+}
+
+void kfree(void *ptr) {
+	heap_free(&kernel_heap, ptr);
+}
-- 
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