From c5fb41ceb4edaee21ddbe208e43262093628a7b6 Mon Sep 17 00:00:00 2001
From: HimbeerserverDE <himbeerserverde@gmail.com>
Date: Sun, 11 Sep 2022 23:17:44 +0200
Subject: [PATCH] Broken stage 2 loader

---
 Makefile        |  4 ++--
 stage1/boot.asm | 29 +++++++++++++++++++++++++++--
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/Makefile b/Makefile
index 9856b63..d6a4fe5 100644
--- a/Makefile
+++ b/Makefile
@@ -11,9 +11,9 @@ stage2/target/x86_64-loadnothing/debug/stage2: stage2/src/main.rs
 	cd stage2 && cargo build
 
 nothing.img: magic.bin stage1/boot.bin stage2/target/x86_64-loadnothing/debug/stage2
-	dd if=/dev/zero of=nothing.img bs=32M count=1
+	dd if=/dev/zero of=nothing.img bs=16M count=1
 	parted -s nothing.img mklabel msdos
-	parted -s -a optimal nothing.img mkpart primary fat32 16M 100%
+	parted -s -a optimal nothing.img mkpart primary fat32 256s 100%
 	doas losetup /dev/loop1 nothing.img
 	doas mkfs.fat /dev/loop1p1
 	doas losetup -d /dev/loop1
diff --git a/stage1/boot.asm b/stage1/boot.asm
index 096a401..9848469 100644
--- a/stage1/boot.asm
+++ b/stage1/boot.asm
@@ -1,6 +1,9 @@
 [bits 16]
 [org 0x7c00]
 
+%define STAGE2START 0x7e00
+%define STAGE2SIZE 0xFF
+
 ; Initialize registers
 xor ax, ax
 mov ds, ax
@@ -33,6 +36,13 @@ print_bytes_si_loop:
 
 	ret
 
+stage2_error:
+	mov ch, 33          ; Our string is 33 characters long
+	mov si, error
+	call print_bytes_si
+
+	jmp $               ; Infinite loop
+
 ; Main
 boot:
 	; Clear the screen
@@ -56,8 +66,23 @@ boot:
 	mov si, hello
 	call print_bytes_si
 
-	jmp $               ; Infinite loop
+	mov ah, 0x02        ; Read sectors
+	mov al, STAGE2SIZE  ; Stage 2 size (16 MiB) in sectors
+	xor ch, ch          ; Cylinder 0
+	mov cl, 2           ; Second sector, they start at 1
+	xor dh, dh          ; Head 0
+	xor dl, dl          ; Drive 0
+	mov bx, STAGE2START ; Memory address to load stage 2 into
+	int 0x13
+
+	jc stage2_error     ; Carry flag is set if there was an error
+
+	cmp al, STAGE2SIZE  ; Have we read as many sectors as we requested?
+	jne stage2_error
+
+	jmp STAGE2START     ; Hand over control to stage 2
 
-hello db 'Welcome to loadnothing stage 1!', 13, 10                   ; \r\n
+hello db 'Welcome to loadnothing stage 1!', 13, 10 ; \r\n
+error db 'Error reading stage 2 from disk', 13, 10 ; \r\n
 
 times (446 - ($ - $$)) db 0x00
-- 
2.44.0