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randomdude



Joined: 01 Jun 2012
Posts: 83
randomdude
i see in some hex edited files: 90h (NOPs) and 66h

what is the instruction 66h? ida doesnt translate it
Post 19 Feb 2014, 18:32
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shutdownall



Joined: 02 Apr 2010
Posts: 518
Location: Munich
shutdownall
66h is an operand size override (16/32 bit) to change default operand size for single instructions.

http://pdos.csail.mit.edu/6.893/2009/readings/i386/s17_01.htm
Post 19 Feb 2014, 20:44
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17287
Location: In your JS exploiting you and your system
revolution
AMD used to promote alignment code that was db 0x66,0x90 with varying amounts of the 0x66's from zero to three times.

It is basically a do-nothing space filler when used in that combination.
Post 19 Feb 2014, 21:10
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shutdownall



Joined: 02 Apr 2010
Posts: 518
Location: Munich
shutdownall
Yes - it is simply a 16-bit or 32-bit NOP. Laughing
Post 20 Feb 2014, 09:58
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randomdude



Joined: 01 Jun 2012
Posts: 83
randomdude
ok thx Very Happy
Post 20 Feb 2014, 18:39
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