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NASM Forum => Using NASM => Topic started by: nobody on June 21, 2007, 07:51:48 PM

Title: Jump Instructions
Post by: nobody on June 21, 2007, 07:51:48 PM

I entered the following code in nasm version 0.98.39:

BITS 32
        jz h
        add eax,byte +0x4
h       add eax,byte +0x4

Running through 'ndisasm -u' produced this:

00000000  7403              jz 0x5
00000002  83C004            add eax,byte +0x4
00000005  83C004            add eax,byte +0x4

Is that right that a jump three bytes forward should be 'jz 0x5'?

I then ran that output through nasm and disassembled the output:

00000000  0F84FFFFFFFF      jz dword 0xffffffff
00000006  83C004            add eax,byte +0x4
00000009  83C004            add eax,byte +0x4

It doesn't seem to be correct.

My question is, how do I write a 'jz' instruction that jumps three bytes forward using a one byte immediate.

Thanks,
Edwin

Title: Re: Jump Instructions
Post by: nobody on June 21, 2007, 07:59:59 PM

Some additional information.

I expected this to work:

jz short 3

but I get:

c.asm:2: error: short relative jump outside segment

Title: Re: Jump Instructions
Post by: nobody on June 21, 2007, 11:26:17 PM

jz $ + 3

Best,
Frank