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Index > Main > Undocumented Instruction Mnemonics

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pal



Joined: 26 Aug 2008
Posts: 227
pal
Hey I am customizing SciTE and I am making an autocomplete with all of the instruction mnemonics I can find. I so far have all of the ones that are in the Intel manuals that are relevant to today's computers (i.e. no AVX, AES etc.).

I was wondering what instruction mnemonics are not in the manuals. I recall MazeGen saying that there are some not in there, one specifically being set* but I cannot remember the condition.

Any ideas on what undocumented instructions there are?

Cheers, pal.

P.S. I will post my properties files on request if someone wants them Smile


Last edited by pal on 16 Oct 2009, 19:34; edited 1 time in total
Post 15 Oct 2009, 22:59
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edfed



Joined: 20 Feb 2006
Posts: 4242
Location: 2018
edfed
by memory, i remember theses instructions to be undocumented:
Code:
burncpu (system instruction)
crashdisk dest (output instruction)
fishin dest,scr (misc instruction)
troll dest,scr (string instruction)
geek dest,scr (assign instruction)
win98 (french instruction to optimise football, obsolete)
inop (nop from interrupts)
    
Post 15 Oct 2009, 23:11
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LocoDelAssembly
Your code has a bug


Joined: 06 May 2005
Posts: 4633
Location: Argentina
LocoDelAssembly
salc, loadall, are the ones that come quick to my mind.

I suggest you to give a look at TABLES.INC from fasm's sources, starting from label instructions_2. Make sure to skip things that are not CPU instructions like 'if', though.
Post 15 Oct 2009, 23:16
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pete



Joined: 20 Apr 2009
Posts: 110
pete
Aha, thanks for the info about the undocumented instructions, edfed. "burncpu" and "crashdisk" will save me a lot of physical work in the future.
Post 16 Oct 2009, 06:05
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pal



Joined: 26 Aug 2008
Posts: 227
pal
Cheers Loco. From the tables.inc file I found lots of instruction mnemonics that are not documented, I was surprised there were that many! I'll post up my list when I am done Smile

edfed: Pointless.
Post 16 Oct 2009, 13:07
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MazeGen



Joined: 06 Oct 2003
Posts: 977
Location: Czechoslovakia
MazeGen
As for Intel undocumented instructions, download http://ref.x86asm.net/x86reference.xml and search for doc="u". If it won't be clear from the XML, try to find the same entry in http://ref.x86asm.net/geek.html
Post 16 Oct 2009, 13:15
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Borsuc



Joined: 29 Dec 2005
Posts: 2466
Location: Bucharest, Romania
Borsuc
edfed wrote:
by memory, i remember theses instructions to be undocumented:
Code:
burncpu (system instruction)
crashdisk dest (output instruction)
fishin dest,scr (misc instruction)
troll dest,scr (string instruction)
geek dest,scr (assign instruction)
win98 (french instruction to optimise football, obsolete)
inop (nop from interrupts)
    
you forgot
Code:
bsod imm  (immediate operand for error code)    
Laughing

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Previously known as The_Grey_Beast
Post 16 Oct 2009, 15:34
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pal



Joined: 26 Aug 2008
Posts: 227
pal
MazeGen: Cheers, I found a few on there I didn't have.

In reference to one such as:

Code:
fcom2
fcomp3
fxch4
fcomp5
fxch7
fstp8
fstp9
fstp1 
    


Are they all just alias' for their counter parts (i.e. fstp* -> fstp)? As I cannot assembly the instructions.

I also didn't realise there was an ffreep mnemonic, I could have really used that in the past few days, I have been using ffree and fincstp. Although I am surprised you have to specify a FPR for it, rather than it no doing st0 as it also pops the stack.
Post 16 Oct 2009, 17:59
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MazeGen



Joined: 06 Oct 2003
Posts: 977
Location: Czechoslovakia
MazeGen
Except for fstp1, they are just aliases. Most (if not all) assemblers don't support them because they are not documented since 80287 (and they never had mnemonics; the mnemonics were "invented").
Post 18 Oct 2009, 14:36
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kohlrak



Joined: 21 Jul 2006
Posts: 1421
Location: Uncle Sam's Pad
kohlrak
what's fstp9 do? There's no st9 that i know of...
Post 19 Oct 2009, 00:03
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MazeGen



Joined: 06 Oct 2003
Posts: 977
Location: Czechoslovakia
MazeGen
ftstp9 is just a (suggested) mnemonic like fld1, the number has nothing to do with operands.
Post 19 Oct 2009, 06:33
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kohlrak



Joined: 21 Jul 2006
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kohlrak
What's it suggesting?
Post 19 Oct 2009, 11:08
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17669
Location: In your JS exploiting you and your system
revolution
It is a suggested mnemonic for the sequence of bytes portrayed by fstp9.

I don't know who first suggested it but it seems that no one else has suggested another mnemonic for that byte sequence so it will probably stick (that is, until Intel say otherwise and suggest a different mnemonic).
Post 19 Oct 2009, 11:44
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MazeGen



Joined: 06 Oct 2003
Posts: 977
Location: Czechoslovakia
MazeGen
The numbers came from i287 manual:
Code:
D9   1101  1001   1101   1REG                         (1)
The marked encodings are not generated by the language translators. If,
however, the 80287 encounters one of these encodings in the instruction
stream, it will execute it as follows: FSTP ST(i)
    

The mnemonic is FSTP1 because Intel marked this encoding using (1).

And this was de facto standardized by www.sandpile.org later.
Post 19 Oct 2009, 12:30
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