asembly time bug/typo

[davidv1992]

somehow nasm doesn't want to compile this bit of code:

Code: Select all

_isr8:
cli
mov [isr_temp],eax
mov eax, 0
pop al ; this goes wrong
mov [isr_temp2],eax
mov eax,[isr_temp]
pusha
mov eax, [isr_temp2]
push byte 8
jmp isr_common

this is quite a critical bit (part of the way i handle exceptions)

[tgo]

you cant push a byte

must be two or four on 32 bit systems

[davidv1992]

okay, so what is pushed by the cpu when an exception happens which has an error code?

[frank]

okay, so what is pushed by the cpu when an exception happens which has an error code?

It pushes a DWORD.

[XCHG]

You sure can push a BYTE value onto the stack as long as BIT#7 of it is not set so in other words, you can push an unsigned value and not a signed. However, when you push a BYTE value, the stack pointer will be decremented 4 bytes (like a DWORD) and Byte2, 3 and 4 of the DWORD will be set to zero. The problem is when you try to POP a byte value when you do this:

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pop al ; this goes wrong 

What you have to do is to access the pushed byte using either the stack pointer or the base pointer (EBP). If I were you, I would choose the latter.