Re: 16 bit jumps in pmode linux

From: Tim Roberts (timr_at_probo.com)
Date: 05/14/04

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    Date: Fri, 14 May 2004 06:20:43 +0000 (UTC)

    sekibkert@yahoo.com (No Spam) wrote:
    >
    >I am hardcoding transition tables of a trie into p4 machine code. 95%
    >of it is near jmp immediates. Since the overall size of the state
    >table is less than 5k, I hoped I could use 16 bit offset jumps and
    >cache a few more states. However, I think it was the gas manual that
    >said that eip was masked to 16 bits when this is tried. Is that what
    >I'm seeing when the following code segs?
    >##########################
    > .globl _start
    >_start:
    > .code16
    > jmp Lab
    > nop
    >Lab:
    > xorl %ebx,%ebx
    > movl $1,%eax
    > int $0x80
    >##########################

    No, the seg fault comes because you've told the assembler you are building
    a 16-bit code segment, but you REALLY have a 32-bit code segment. 

    -- 
- Tim Roberts, timr@probo.com
  Providenza & Boekelheide, Inc.
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