start of page allocation

src/drivers/uart.h

@@ -4,6 +4,7 @@
 #define UART_ADDRESS 0x10000000
 void uart_put(size_t base_addr, uint8_t data);
 int kputchar(int ch);
+void knewline();
 void kputs(const char *str);
 void kprint(const char *str);
 #endif

src/kernel/kernel.c

@@ -3,8 +3,12 @@
 #include <drivers/uart.h>
 #include <syscon/syscon.h>
 #include <kernel/panic.h>
+#include <kernel/memory.h>
 
 void kmain() {
-    kprint("Hello, OS World!\n");
+    kputs("Hello, OS World!");
+    kputs("-------------------");
+    knewline();
+    page_init();
     poweroff();
 }

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;
+}

src/kernel/memory.h

@@ -0,0 +1,7 @@
+#ifndef KMEMORY_H
+#define KMEMORY_H
+
+void page_init();
+void page_free(void *addr);
+
+#endif

src/syscon/syscon.c

@@ -4,11 +4,17 @@
 #include "drivers/uart.h"
 
 void poweroff(void) {
+	knewline();
+	kputs("-------");
+	knewline();
   	kputs("Poweroff requested");
 	*(volatile uint32_t *)SYSCON_ADDR = SYSCON_POWEROFF;
 }
 
 void reboot(void) {
+	knewline();
+	kputs("-------");
+	knewline();
   	kputs("Reboot requested");
 	*(volatile uint32_t *)SYSCON_ADDR = SYSCON_REBOOT;
 }