Add lib/mem.*.

Makefile

@@ -59,8 +59,8 @@ image.bin: mbr.bin fs.img
 	cat $^ >$@
 
 kernel.bin: kernel.o console.o drivers/vga.o drivers/keyboard.o \
-	string.o drivers/ata.o cpu/vectors.o cpu/idt.o cpu/gdt.o drivers/uart.o \
-	fs/fs.o
+	drivers/ata.o cpu/vectors.o cpu/idt.o cpu/gdt.o drivers/uart.o \
+	fs/fs.o lib/mem.o lib/string.o
 	$(LD) $(LDFLAGS) -o $@ -Ttext 0x1000 $^
 
 %.o: %.c

drivers/keyboard.c

@@ -2,6 +2,7 @@
 #include "../cpu/isr.h"
 #include "../console.h"
 #include "port.h"
+#include "../lib/mem.h"
 
 static const char sc_ascii[] = {
     '?', '?', '1', '2', '3', '4', '5', '6',
@@ -11,11 +12,13 @@ static const char sc_ascii[] = {
     'b', 'n', 'm', ',', '.', '/', '?', '?', '?', ' ',
 };
 
+enum { kbd_buf_capacity = 1024 };
+
 static void interrupt_handler(registers_t *r) {
     uint8_t scancode = port_byte_in(0x60);
     if (scancode < sizeof(sc_ascii)) {
         char c = sc_ascii[scancode];
-        if (kbd_buf_size < 1024) {
+        if (kbd_buf_size < kbd_buf_capacity) {
             kbd_buf[kbd_buf_size++] = c;
         }
         char string[] = {c, '\0'};
@@ -27,7 +30,7 @@ char* kbd_buf;
 unsigned kbd_buf_size;
 
 void init_keyboard() {
-    kbd_buf = (char*)(1 << 20);
+    kbd_buf = kmalloc(kbd_buf_capacity);
 
     register_interrupt_handler(IRQ1, interrupt_handler);
 }

lib/mem.c

@@ -0,0 +1,12 @@
+#include "mem.h"
+
+static void* freeptr;
+
+void* kmalloc(size_t size) {
+    if (!freeptr) {
+        freeptr = (void*)(1<<20);
+    }
+    void* result = freeptr;
+    freeptr += size;
+    return result;
+}

lib/mem.h

@@ -0,0 +1,5 @@
+#pragma once
+
+typedef unsigned size_t;
+
+void* kmalloc(size_t size);