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Allegrex opcodes

 
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gauri



Joined: 20 Jan 2008
Posts: 35
Location: Belarus
PostPosted: Sun Jan 27, 2008 9:55 pm    Post subject: Allegrex opcodes Reply with quote
When going thru interruptman code with IDA, I've noticed some unknown opcodes here and there.

The first ones seem to map to COP0 family, but they are marked reserved in MIPS docs. These insns seem all to be R-types and use rs=0x04 or 0x06 or 0x00.

The second ones appear to be SPECIAL3-BSHFL insns, but also they are not marked in MIPS docs. These are:
Code:
0x7C171D20
0x7C0F7D20
0x7C063520
0x7C1A2D20


Any suggestions what these might be?

And the third thing is, I see dsrlv insn used here and there, but, as we know, SC is 32-bit and there's no way dsrlv will ever be implemented there.
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moonlight



Joined: 26 Oct 2005
Posts: 567
PostPosted: Sun Jan 27, 2008 10:17 pm    Post subject: Reply with quote
0x7C171D20: bitrev $v1, $s7
0x7C0F7D20: bitrev $t7, $t7
0x7C063520: bitrev $a2, $a2
0x7C1A2D20: bitrev $a1, $k0

It converts input "01010001" into output "10001010"

Anyways, if you want to see the rest of opcodes, get prxtool ;)
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gauri



Joined: 20 Jan 2008
Posts: 35
Location: Belarus
PostPosted: Sun Jan 27, 2008 11:32 pm    Post subject: Reply with quote
moonlight wrote:
Anyways, if you want to see the rest of opcodes, get prxtool ;)

Hmmm. Didn't think about that. Thanks for the advice!
An updated IDA Pro plugin will be completed in a day or two. :-)
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