Assembly errors in my boot loader code

[chris]

Hi,

In the process of creating my boot loader I've come upon a few Assembly errors that I don't know how to fix. Any help would be appreciated.

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pmode.s:7: error: invalid combination of opcode and operands
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        mov     ss, 08000h

This one is weird. It tells me that a symbol isn't defined when I do define it. It is called before it's defined though, but I though this was OK?

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pmode.s:38: error: symbol `.empty_8024_end_loop' undefined
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No idea for this one. I'm assuming the line of code it points to has nothing to do with the error.

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pmode.s:180: error: phase error detected at end of assembly.
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        dw 0AA55h

----

I'm also wondering what I need to do after setting the bit in cr0 for protected mode. Currently I just make a "jmp main32".

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BITS 32

main32:
        jmp main32

[bakery2k]

Which assembler are you using?

[Dreamsmith]

First of all, there is no such instruction on Intel processors as "move an immediate value into the SS register", thus that error. Do something like this instead:

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    mov ax,0x8000
    mov ss,ax

As far as your undefined reference and your phase error, you didn't list the code where you define the reference, so we can't possibly say for sure what the problem is. However, although labels can be forward referenced, equates cannot, IIRC. Is it possible that's your problem?

[chris]

Which assembler are you using?

NASM. Sorry, should have mentioned that in my OP.

I fixed the first problem with Dreamsmith's solution. As for the other two, I still don't know what's going on. Here is the code:

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.empty_8042_loop:
        dec     cx
        jz      .empty_8024_end_loop ***

        mov     dx, 064h
        in      al, dx
        test    al, 01h
        jz      .no_output

        mov     dx, 064h
        in      al, dx
        jmp     .empty_8042_loop

.no_output:
        test    al, 02h
        jnz     .empty_8042_loop

.empty_8042_end_loop:
        pop     cx
        ret

And I don't know what to give you for the phase thing? It just points me to the last line in the boot loader, which I gave in my OP.

[Dreamsmith]

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        jz      .empty_8024_end_loop
        ...
.empty_8042_end_loop:

And I don't know what to give you for the phase thing? It just points me to the last line in the boot loader, which I gave in my OP.

Fixing the undefined reference should fix the phase error. As for the undefined reference, do you see it now? 8024 vs. 8042?

[bakery2k]

I'm also wondering what I need to do after setting the bit in cr0 for protected mode. Currently I just make a "jmp main32".

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BITS 32

main32:
        jmp main32

You need to make a far jump, setting CS to the value for your code segment. Since you want a 32-bit jump offset from 16-bit code, you need a "jmp dword". You then need to load all of the other segment registers. Eg

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BITS 16

mov eax, cr0
or eax, 1
mov cr0, eax

jmp dword 0x08:main32

BITS 32

main32:

mov ax, 0x10
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax

[chris]

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        jz      .empty_8024_end_loop
        ...
.empty_8042_end_loop:

And I don't know what to give you for the phase thing? It just points me to the last line in the boot loader, which I gave in my OP.

Fixing the undefined reference should fix the phase error. As for the undefined reference, do you see it now? 8024 vs. 8042?

Oh man, I can't beleive I missed that. I looked at those two labels hard too! Thank you Dreamsmith.

And thanks to bakery2k for the others