From 6e7a6563d53261846665b4738e76b9b2b7744df3 Mon Sep 17 00:00:00 2001
From: Ain <41307858+nero@users.noreply.github.com>
Date: Sun, 29 Sep 2019 21:33:28 +0000
Subject: [PATCH] Improve register hygiene

---
 kernel/bpb.asm | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/kernel/bpb.asm b/kernel/bpb.asm
index e3b70c5..f0213e5 100644
--- a/kernel/bpb.asm
+++ b/kernel/bpb.asm
@@ -1,16 +1,31 @@
 ; IN	DL	drive number
 ;	BP	ptr to bpb_size'd buffer
 bpb_load:
+  push ax
+  push dx
+
   mov [bp+(bpb_size-1)], dl
 
+  ; load first sector
   xor dx, dx
   xor ax, ax
   call drive_read
 
+  push cx
+  push si
+  push di
+
+  ; copy BPB to BP
   mov si, (diskbuf+0x0B)
   mov di, bp
   mov cx, (bpb_size-1)
   rep movsb
 
+  pop di
+  pop si
+  pop cx
+
+  pop dx
+  pop ax
   ret