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    SubjectRe: NOP instruction
    On Wed, Dec 16, 1998 at 11:36:00AM +1030, Mofeed Shahin wrote:

    > Ummm, I was under the impression that NOP under the intel was 0x90...


    > I am pretty sure the intel does have a real NOP.

    don't think so:

    [me:1] caffeine:~$ cat nop.S

    _start: .globl _start

    xchg %eax,%eax

    movl $0x01,%eax
    movl $0x00,%ebx
    int $0x80
    [me:1] caffeine:~$ as -Qy -o nop.o nop.S
    [me:1] caffeine:~$ objdump -d -S nop.o

    nop.o: file format elf32-i386

    Disassembly of section .text:

    00000000 <_start>:
    0: 90 nop
    1: 0f a2 cpuid
    3: 90 nop
    4: b8 01 00 00 00 movl $0x1,%eax
    9: bb 00 00 00 00 movl $0x0,%ebx
    e: cd 80 int $0x80

    As you can see -- gas treats nop as xchg %eax,%eax.


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