diff --git a/Makefile b/Makefile
index 97b38ad..eedb0fe 100644
--- a/Makefile
+++ b/Makefile
@@ -37,8 +37,8 @@ ASMFLAGS = -target elf-i386 -ffreestanding -c -g
 LDKERNELFLAGS = --script=script.ld
 endif
 
-OBJECTS = ./kernel.o ./console.o ./drivers/vga.o ./drivers/uart.o ./drivers/keyboard.o \
-	./cpu/idt.o ./cpu/gdt.o ./cpu/swtch.o ./cpu/vectors.o ./lib/mem.o ./proc.o ./lib/string.o \
+OBJECTS = ./kernel/kstart.o ./kernel.o ./console.o ./drivers/vga.o ./drivers/uart.o ./drivers/keyboard.o \
+	./cpu/idt.o ./cpu/gdt.o ./cpu/swtch.o ./cpu/vectors.o ./kernel/mem.o ./proc.o ./lib/string.o \
 	./fs/fs.o ./drivers/ata.o ./lib/string.o ./proc.o ./drivers/pit.o ./kernel/vm.o
 
 run: image.bin
diff --git a/cpu/idt.c b/cpu/idt.c
index 91d8d02..06669df 100644
--- a/cpu/idt.c
+++ b/cpu/idt.c
@@ -1,5 +1,6 @@
 #include "isr.h"
 #include "gdt.h"
+#include "memlayout.h"
 #include "../syscall.h"
 #include "../proc.h"
 #include "../drivers/port.h"
@@ -117,10 +118,11 @@ void trap(registers_t *r) {
 }
 
 static void* get_userspace_ptr(uint32_t ptr) {
-    if (ptr >= 0xffffffff - USER_BASE) {
+    if (ptr > KERNBASE) {
         return 0;
     }
-    return (void*)(ptr + USER_BASE);
+    // FIXME: check if ptr is mapped and a valid 0-terminated string
+    return (void*)(ptr);
 }
 
 static int handle_puts(const char* s) {