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 Some MIPS definitions

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PostSubject: Some MIPS definitions   Thu Dec 02, 2010 5:01 am

Originally Posted by Team Unknown Zecaxao so all thanks goes to him Very Happy

I wanted to give some definitions of what you might find in psplink, so next time you see a crash, you know if it's exploitable or not. I also thought of making some instruction definitions, but that would be too long. Maybe i'll put a spoiler with those, if someone wants them. I wrote Exception Types from my learning experience, so I could be wrong about some of them, so feel free to tell me if that's the case.

Code:
$zr -> Constant zero
$at -> Assembler temporary
$v0-v1 -> Function return
$a0-a3 -> Incoming arguments
$t0-t9 -> Temporaries
$s0-s7 -> Saved temporaries
$k0-k1 -> Exception handling <- Defines the exception handling
$gp -> Global data pointer
$sp -> Stack pointer
$fp -> Saved temporary
$ra -> Return address <- GOAL

CoProcessor Registers:
Code:
BADVAddr -> Bad Virtual Address
Status -> Status Register
Cause -> Cause Register
EPC -> Exception Program Counter Register

Exception Types:
Code:
0->External Interrupt (useless)
1-3->Reserved (most likely FPU exception) (useless)
4->Address error (load or instruction fetch)(BINGO!!! Available in Davee's Tiff Exploit)
5->Address error (data store) (useless, unless you control some registers' values)
6->Bus error (instruction fetch) (BINGO!!! Available in ALL game exploits)
7->Bus error (data load or store) (useless, unless you control some register's values)
8-Syscall instruction (useless)
9-Breakpoint (useless, BUT a very rare case where $ra was totally overwritten appeared, still it's very very rare that this happens)
10-Reserved instruction (useless)
11- Coprocessor unusable (useless)
12- Arithmetic overflow (useless)
13-15- Not used

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