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dragonfire353 wrote:Ok, more problems.... so I'm having an issue with the cursor going down on consecutive calls to print string, i'm trying to get the cursor to only go down after the first call to print_string using the get cursor position function of the BIOS. I've even tried using a local boolean variable but that didn't even work. I'm using test dl, dl and je. I've tried cmp dl, 0 and je but that doesn't work either.

dragonfire353 wrote:Oh, and also trying to hard code fat32 partition for virtualbox for now till I understand it enough to write an installer from usb. I have the BPB and EBPB I believe but not the partition listings at the end of the 512 bytes if anyone has any hints.....

egos wrote:No, your "jmp start" isn't short jump because "start" is too far. Here is short jump:

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  jmp short @f
  nop
  rb BS_SIZE-3
@@:

When you use "teletype function" in stage 1 you can forget about other video functions (including function 0). Here is one of my putstr modifications:

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@@:
        mov bx,7
        mov ah,0Eh
        push si
        int 10h
        pop si
putstr:
        mov al,[si]
        inc si
        and al,al
        jg short @b
        ret

Use CR-LF (13, 10) to move cursor to the beginning of the next line.

Now you should read sector 2 (c:h:s=0:0:3), not 1 (c:h:s=0:0:2). Moreover if your image is in partition you should add its starting sector number to 2 and convert result to CHS before reading, or use "extended read" function. You can use some foreign first stage boot loaders, e.g. Yoda's fat32/"rawfs" stage 1.

mov ah, 02h		; code for the read disk command
	mov al, 3		; how many sectors to read?
	mov ch, 0		; which cylnder?
	mov cl, 2		; which sector do we start reading from?
	mov dh, 0		; which head?
	mov bx, 7E00h	; es:bx where we loading this stuff? in this case, we're loading directly after the first 512 bytes that were loaded by the BIOS, so we get the rest of the bootloader
	int 13h			; BIOS disk operation interrupt

push si ; the BIOS call(s) may destroy the si register
	call get_cursor_position
	test dl, dl			; is dl (column) 0? If not we should move the cursor down
	je .pre_repeat
	call move_cursor_down

...

get_cursor_position:
	xor bh, bh
	mov ah, 3
	int 10h
	ret

; returns with carry set if finished
	.is_finished:
		jc conditional_return		; carry set means "end of list already reached"
		stc
		cmp ebx, 0					; ebx 0 means that we've reached the end of the list
		je conditional_return
		clc
		ret

...

conditional_return:
	ret ; this is used since there is no "return if equal/ne" instruction

dragonfire353 wrote:Also about your suggestion for using teletype... the problem I'm having is determining when I should move the cursor down, not how to.

dragonfire353 wrote:

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		stc
		cmp ebx, 0

Is there something obviously wrong with the way I'm doing things?

dragonfire353 wrote:Ok, so teletype automatically moves the cursor for me when the end of the screen is reached, so does regular printing, from my experience so far, does it not?

dragonfire353 wrote:I want to move the cursor down before reaching the end of the screen, after each line, so I need to manually call it, or print CR+LF if using teletype?

dragonfire353 wrote:Sorry if I'm not being clear, I'm trying to tell on each call to the print_string function, if the cursor is not in the far left most column, column 0, and if it is not, then I should move the cursor down; because that means something was already printed on that line, and I don't want to print something else on that line or I should print a space before printing the next string.

db "CPU Signature: ",0
db "Feature flags:",0
db " APIC",0
db " CMOV",0
db " MMX",0

dragonfire353 wrote:Mac still doesn't recognize it, how come it worked when there were no partition tables? Do you not need partition tables if there's only one partition?

Octocontrabass wrote:

dragonfire353 wrote:Ok, so teletype automatically moves the cursor for me when the end of the screen is reached, so does regular printing, from my experience so far, does it not?

Teletype always moves the cursor for you; regular printing does not.

dragonfire353 wrote:I want to move the cursor down before reaching the end of the screen, after each line, so I need to manually call it, or print CR+LF if using teletype?

Printing CR+LF using teletype guarantees that the screen will scroll if you've reached the bottom, so that's what you should do.

dragonfire353 wrote:Sorry if I'm not being clear, I'm trying to tell on each call to the print_string function, if the cursor is not in the far left most column, column 0, and if it is not, then I should move the cursor down; because that means something was already printed on that line, and I don't want to print something else on that line or I should print a space before printing the next string.

Several of my strings include a space at the beginning or end so that formatting will be correct for all combinations I'd want to print them in. For example:

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db "CPU Signature: ",0
db "Feature flags:",0
db " APIC",0
db " CMOV",0
db " MMX",0

dragonfire353 wrote:Mac still doesn't recognize it, how come it worked when there were no partition tables? Do you not need partition tables if there's only one partition?

You're confusing the MBR (Master Boot Record) with the VBR (Volume/partition Boot Record).

The MBR, if you have one, goes at the very beginning of the disk. It contains the partition table and a small amount of code to load the VBR of the active partition, or complain if there is no active partition.

The VBR is the first sector of the partition. It's where your BPB/EBPB and boot code goes.

http://home.teleport.com/~brainy/fat32.htm wrote:Master Boot Record

The Master Boot Record is the same for pretty much all Operating Systems. It is located on the first Sector of the Hard Drive, at Cylinder 0, Head 0, Sector 1. It is the first piece of code that your computer runs after it has checked all of your hardware (POST) and turned control of loading software over the hard drive. It also contains the partition table, which defines the different sections of your hard drive. Basically if anything happens to this little 512 byte section, your hard drive is brain dead. Kinda scary, eh?

Offset Description Size
000h Executable Code (Boots Computer) 446 Bytes
1BEh 1st Partition Entry (See Next Table) 16 Bytes
1CEh 2nd Partition Entry 16 Bytes
1DEh 3rd Partition Entry 16 Bytes
1EEh 4th Partition Entry 16 Bytes
1FEh Boot Record Signature (55h AAh) 2 Bytes

dragonfire353 wrote:Is 255/265.9 MB the min fat32 size?

I'm confused what you mean by I should be reading from sector 2? I have here:

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mov ah, 02h		; code for the read disk command
	mov al, 3		; how many sectors to read?
	mov ch, 0		; which cylnder?
	mov cl, 2		; which sector do we start reading from?
	mov dh, 0		; which head?
	mov bx, 7E00h	; es:bx where we loading this stuff? in this case, we're loading directly after the first 512 bytes that were loaded by the BIOS, so we get the rest of the bootloader
	int 13h			; BIOS disk operation interrupt

That we start reading from sector 2? Is this not correct?

Reason I'm trying to do this complicatedly is so that it only moves the cursor down if it's not at the first column, meaning it's at the end of an already printed string simply because I don't want the cursor blinking below the last printed line, OCD much? But it's more frustrating that I can't get this seemingly simple thing to work.

        call putstr
        nb 13,10,"Disk error",0
...
        call putstr
        nb ".",13,10,"Press Ctrl-Alt-Del to restart...",32,128

Could you help clarify what's going on then?