first and second stage basic bootloader

Makefile

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+all : image
+
+compile :
+	nasm -f bin -o boot.bin boot.asm
+	nasm -f bin -o program.bin program.asm
+
+
+image : compile
+	sudo dd if=/dev/zero of=disk.img bs=1024 count=720
+	sudo dd if=boot.bin of=disk.img bs=512 count=1 conv=notrunc
+	sudo dd if=program.bin of=disk.img bs=512 seek=1 count=1 conv=notrunc
+
+
+flashusb : image
+        #sudo umount /dev/sdb
+	sudo dd if=boot.bin of=/dev/sdb bs=512 count=1
+	sudo dd if=program.bin of=/dev/sdb bs=512 seek=1 count=1
+
+run : image
+	qemu-system-x86_64 disk.img
+
+clean :
+	rm *.img
+	rm *.bin
+
+
+

README.md

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+#Useful resources
+
+
+
+##interrupts
+http://stanislavs.org/helppc/idx_interrupt.html
+
+##BIOS colors
+https://en.wikipedia.org/wiki/BIOS_color_attributes
+
+##Second stage bootloader booting from usb
+https://stackoverflow.com/questions/36044706/enable-the-boot-loader-to-load-the-second-sector-of-a-usb
+

boot.asm

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+[bits 16]
+[org 0x7c00]
+
+                   ; Use the boot drive number passed to us by BIOS in register DL
+start:
+    xor ax,ax      ; We want a segment of 0 for DS for this question
+    mov ds,ax      ;     Set AX to appropriate segment value for your situation
+    mov es,ax      ; In this case we'll default to ES=DS
+    mov bx,0x8000  ; Stack segment can be any usable memory
+
+    mov ss,bx      ; This places it with the top of the stack @ 0x80000.
+    mov sp,ax      ; Set SP=0 so the bottom of stack will be @ 0x8FFFF
+
+    cld            ; Set the direction flag to be positive direction
+
+    mov si, wolf_wel_msg
+    call wolf_print
+
+    mov si, wolf_kernel_load
+    call wolf_print
+
+    pushf
+    stc
+
+    mov ah,00
+    int 13h
+
+    read_sector:
+        mov ax, 0x0
+        mov es, ax      ; ES = 0
+        mov bx, 0x1000  ; BX = 0x1000. ES:BX=0x0:0x1000 
+                        ; ES:BX = starting address to read sector(s) into
+        mov ah, 02      ; Int 13h/AH=2 = Read Sectors From Drive
+        mov al, 01      ; Sectors to read = 1
+        mov ch, 00      ; CH=Cylinder. Second sector of disk
+                        ; is at Cylinder 0 not 1
+        mov cl, 02      ; Sector to read = 2
+        mov dh, 00      ; Head to read = 0
+                        ; DL hasn't been destroyed by our bootloader code and still
+                        ;     contains boot drive # passed to our bootloader by the BIOS
+        int 13h
+
+    jc wolf_error
+    popf
+    jmp 0x0:0x1000
+    cli
+    hlt
+
+    wolf_error:
+        mov si, wolf_error_msg
+        call wolf_print
+        mov si, wolf_error_msg1
+        call wolf_print
+        mov ah,00
+        int 16h
+        xor ax,ax
+        int 19h
+
+    wolf_print:
+        lodsb
+        or al,al
+        jz exit
+        mov ah,0x0e
+        int 10h
+        jmp wolf_print
+        exit:
+        ret
+
+; Moved the data before the boot signature but after the code
+wolf_wel_msg db 'Welcome to this publication...',0x0D,0x0A,0
+wolf_kernel_load db 'Loading program',0x0D,0x0A,0
+wolf_error_msg db 'Program not found!',0x0D,0x0A,0
+wolf_error_msg1 db 'Press any key to restart..',0
+
+times 510-($-$$) db 0
+dw 0xAA55

program.asm

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+[org 0x1000]
+
+jmp start
+data:
+   msg db 'program XPUB',0
+start:
+   MOV AH, 06h    ; Scroll up function
+   XOR AL, AL     ; Clear entire screen
+   XOR CX, CX     ; Upper left corner CH=row, CL=column
+   MOV DX, 184FH  ; lower right corner DH=row, DL=column 
+   MOV BH, 1Eh    ; YellowOnBlue
+   INT 10H
+
+   mov si, msg
+   call print      ; print is a function, use CALL instead of JMP
+
+   cli
+   hlt
+   print:
+      lodsb
+      or al, al
+      jz exit
+      mov ah,0x0e
+      int 10h
+      jmp print
+  exit:
+      ret
+