Snake

A Gecko Code Assembler written in Rust

Gecko is a cheat-code specification popularized by modchips and Action Replay for the Nintendo Wii and Gamecube It has since been made freely aviable for use in the Dolphin Emulator allow users to easily achive ACE in their favorite games Why use an assembler? Because I'm not writting my code with just numbers bro

Gecko is fundementally a bootloader that implements 4 registers Base Addresses, Pointer Offsets, Gecko Registers, & Counter Registers

Base Addresses (BA) can be thought of as analagous to rbp or ebp in ARM or x86 respectively By controlling the Base Address we can controll the execution flow and achive ACE. How we achieve ACE can vary from game-to-game. When using a gecko "return" rip = $ba

Pointers Offsets (PO) are required to index beyond 0x01000000

Gecko Registers (g[0-15]) General Purpose Registers (16)

Counter Registers ('c[0-255]) unaccessible and counts stuff depending on the Comparison Register

Comparision Register - unaccessible and typically called the execution register. Store's the result of comparisons

Keep in mind that $BA instructions can only be indexed until 0x01000000

This Gecko code specification can be expanded upon to create consumer focused applications for all platforms

Gecko is best thought of as a Runtime similar to that of the C standard library for PowerPC architectures. Its primary purpose is cheating however a memory allocator can be added via snake install reed

Usage

snake build <project root> snake clean <project root> snake release <project root> snake publish <project root> snake install <project root>

Snake -> Gecko Mapping

This is a reference to all opcode instructions for Gecko

Symbols Sheet

Y       = length
X       = value / memory address
T       = type (byte/half-word/word) (8/16/32)
C       = constants
______  = register offset / pointer offset to RAM
 ...    = Arbitrary Data
{...}   = PowerPC Assembly (default assembler: `gas`)
{#asd}  = Includes `asd.ppc` from `powerpc/` folder
p <XXXX> =   PO+XXXX  | Scalar
b <XXXX> =   BA+XXXX  | Scalar
b [XXXX] =  [BA+XXXX] | Map
p [XXXX] =  [PO+XXXX] | Map
g$[XXXX] =  [g$+XXXX]

Assembler Format

- Text Sections are seperated by `:`
- arguments follow `<src> -> <dest>` format
- Registers are formated as `$`
- Constants can be previewed by `L'..', 0x, 0b`

Instructions

Instruction Format <verb> (:<class>)+ <size of op> <p/b> args...

Each Instruction has a different OpCode ``

Tips

1. When writting ASM use BA instructions for tmp values and PO instructions for values in RAM