From 5becc898723511e03f0f42ef6d1ba5e34ded9622 Mon Sep 17 00:00:00 2001
From: Ain <41307858+nero@users.noreply.github.com>
Date: Sat, 23 Mar 2019 20:37:18 +0000
Subject: [PATCH] Instead of adjusting CS, always relocate NBP to 0x00500

---
 nbp.asm | 40 +++++++++++++++-------------------------
 1 file changed, 15 insertions(+), 25 deletions(-)

diff --git a/nbp.asm b/nbp.asm
index 5192e68..ff97f54 100644
--- a/nbp.asm
+++ b/nbp.asm
@@ -1,38 +1,26 @@
 ; assumptions about the starting envionment
 cpu 8086
 org 0x0000
-; dl		probable drive number
-; ds:si		probable pointer to partition structure
-; es:bx		probable pxeenv+ structure
+; es:bx		pxeenv+ structure
 ; ss:sp		functional stack
 
-_startup:
 ; during PXE, CS=0000 and IP=7C00
-; adjust CS so our offsets match org setting above
-mov ax, _exit
-push ax ; store exit addr on stack so main will return to it
-push bx ; backup bx
-call near .push_ip
-.push_ip:
-pop bx
-sub bx, .push_ip ; subtract expected value ...
-shr bx,1 ; shift it to 4 bits to the right
-shr bx,1
-shr bx,1
-shr bx,1
-mov ax,cs
-add ax,bx ; so we can add it to cs
-pop bx ; restore bx
-push ax ; cs
-mov ax, main
-push ax ; ip
-sti
-retf ; jump
+_startup:
+  xor ax, ax
+  mov ss, ax
+  mov sp, 0x0000
+  mov ds, ax
+  mov es, ax
+
+  mov si, 0x7C00
+  mov di, 0x0500
+  mov cx, (_reloc_end)
+  rep movsb
+  jmp 0x0050:main
 
 _exit:
   mov si, .message
   call kprintf
-  int 0x20
 .loop:
   hlt
   jmp .loop
@@ -40,3 +28,5 @@ _exit:
   db "Halted: Waiting for poweroff...", 0
 
 %include "kernel/main.asm"
+
+_reloc_end: