Map kernel high

Very important to give qemu memory through PHYSTOP :(

console.c

@@ -9,6 +9,7 @@
 #include "spinlock.h"
 #include "fs.h"
 #include "file.h"
+#include "memlayout.h"
 #include "mmu.h"
 #include "proc.h"
 #include "x86.h"
@@ -60,6 +61,9 @@ cprintf(char *fmt, ...)
   if(locking)
     acquire(&cons.lock);
 
+  if (fmt == 0)
+    panic("null fmt");
+
   argp = (uint*)(void*)(&fmt + 1);
   state = 0;
   for(i = 0; (c = fmt[i] & 0xff) != 0; i++){
@@ -121,7 +125,7 @@ panic(char *s)
 //PAGEBREAK: 50
 #define BACKSPACE 0x100
 #define CRTPORT 0x3d4
-static ushort *crt = (ushort*)0xb8000;  // CGA memory
+static ushort *crt = (ushort*)P2V(0xb8000);  // CGA memory
 
 static void
 cgaputc(int c)