start of page allocation

src/kernel/memory.c

@@ -0,0 +1,33 @@
+#include <stdint.h>
+#include <stddef.h>
+#include "drivers/uart.h"
+#include "memory.h"
+
+#define PAGE_SIZE 4096
+
+struct Page {
+	struct Page *next;
+};
+
+static struct Page *free_list;
+
+extern uint8_t _bss_end[]; // 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 end = 0x88000000; // Default QEMU RAM limit
+
+	for (uintptr_t addr = start; addr + PAGE_SIZE <= end; addr += PAGE_SIZE) {
+		page_free((void *)addr);
+	}
+}
+
+void page_free(void *addr) {
+	if (addr == NULL) return;
+
+	struct Page *p = (struct Page *)addr;
+
+	p->next = free_list;
+	free_list = p;
+}