From 3efbcf24f4e7f5a0c84bce563d9af645d5134e19 Mon Sep 17 00:00:00 2001
From: Liam Kerr <liam.d.kerr@protonmail.com>
Date: Mon, 9 Feb 2026 00:13:00 +0000
Subject: [PATCH] page allocation

---
 linker.ld           |  3 +++
 src/kernel/kernel.c |  9 +++++++++
 src/kernel/memory.c | 29 ++++++++++++++++++++++++++---
 src/kernel/memory.h |  1 +
 src/kernel/panic.c  |  1 +
 5 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/linker.ld b/linker.ld
index 98a4528..f33640c 100644
--- a/linker.ld
+++ b/linker.ld
@@ -30,4 +30,7 @@ SECTIONS
     PROVIDE(_stack_bottom = .);
     . += 4096; 
     PROVIDE(stack_top = .);
+
+   . = ALIGN(4K);
+   _heap_start =.;
 }
diff --git a/src/kernel/kernel.c b/src/kernel/kernel.c
index f9b4f56..5765f87 100644
--- a/src/kernel/kernel.c
+++ b/src/kernel/kernel.c
@@ -10,5 +10,14 @@ void kmain() {
     kputs("-------------------");
     knewline();
     page_init();
+
+    kprint("Stress testing memory...\n");
+    while(1) {
+        void *p = page_alloc();
+        if (p == NULL) {
+            kpanic("Expected OOM reached!");
+        }
+    }
+
     poweroff();
 }
diff --git a/src/kernel/memory.c b/src/kernel/memory.c
index e28f57b..aaedabb 100644
--- a/src/kernel/memory.c
+++ b/src/kernel/memory.c
@@ -2,6 +2,7 @@
 #include <stddef.h>
 #include "drivers/uart.h"
 #include "memory.h"
+#include "panic.h"
 
 #define PAGE_SIZE 4096
 
@@ -9,13 +10,19 @@ struct Page {
 	struct Page *next;
 };
 
-static struct Page *free_list;
+struct HeapHeader {
+	size_t size;
+	int is_free;
+	struct HeapHeader *next;
+};
 
-extern uint8_t _bss_end[]; // named in the linker script
+static struct Page *free_list = NULL;
+
+extern uint8_t _heap_start[]; // named in the linker script
 
 void page_init() {
 	kprint("Initialising page allocator.\n");
-	uintptr_t start = ((uintptr_t)_bss_end + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1);
+	uintptr_t start = ((uintptr_t)_heap_start + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1);
 	uintptr_t end = 0x88000000; // Default QEMU RAM limit
 
 	for (uintptr_t addr = start; addr + PAGE_SIZE <= end; addr += PAGE_SIZE) {
@@ -30,4 +37,20 @@ void page_free(void *addr) {
 
 	p->next = free_list;
 	free_list = p;
+}
+
+void *page_alloc() { {
+	if (free_list == NULL) {
+		kpanic("No free pages!");
+	}
+	struct Page *p = free_list;
+	free_list = free_list->next;
+
+	//zero out the page
+	for (int i = 0; i < (PAGE_SIZE/8); i++) {
+		((uint8_t *)p)[i] = 0;
+	}
+
+	return (void *)p;
+}
 }
\ No newline at end of file
diff --git a/src/kernel/memory.h b/src/kernel/memory.h
index 943bbe9..dcee87b 100644
--- a/src/kernel/memory.h
+++ b/src/kernel/memory.h
@@ -3,5 +3,6 @@
 
 void page_init();
 void page_free(void *addr);
+void *page_alloc();
 
 #endif
diff --git a/src/kernel/panic.c b/src/kernel/panic.c
index fe203c4..5c60da0 100644
--- a/src/kernel/panic.c
+++ b/src/kernel/panic.c
@@ -4,6 +4,7 @@
 #include <syscon/syscon.h>
 
 void kpanic(const char *reason){
+    kprint("\n!!! PANIC!!!\n");
 	kprint(reason);
 	poweroff();
 }