lewisakura / powerpc

simple PowerPC instruction encoder, and binary patcher

powerpc

A simple library to handle PowerPC instruction encoding, and to enable patching ranges of a binary. This allows simple reproduction of patches to a channel - perhaps ones downloaded via NUS.

Consider this example of a patch:

example := PatchSet{
	// A name describing this patch.
	Name: "Nullify access check",
	// The offset of the function in the binary - i.e. the DOL.
	AtOffset: 57236,

	// Instructions present previously.
	// In this example, we have a generic function prolog.
	Before: Instructions{
		STWU(R1, R1, 0xFC10),
	}.Bytes(),
	// Instructions present afterwards.
	// They must match the same length as what they are replacing.
	// In this example, we immediately return.
	After: Instructions{
		BLR(),
	}.Bytes(),
}
patched, err := ApplyPatch(example, binary)

You additionally have the option to use PatchSets, collections of patches that may be related to each other. Consider the following scenario:

example := PatchSet{
	Name: "Change domains",

	Patches: []Patch{
		Patch{
			Name: "Remove domain whitelist",
				// [...]
			},
			Patch{
				Name: "Use custom domain",
				// [...]
			},
		},
}
patched, err := ApplyPatchSet(example, binary)

It is recommended to import this package without a prefix in order to permit easier usage of instruction types. An example doing this is as follows:

import (
	. "github.com/wii-tools/powerpc"
)

Wishlist

• Implement more instructions forms.
• Use type constraints within structs to allow both byte and Instruction slices.

Resources

• PowerPC mnemonics/instruction forms via NXP
• WSC-Patcher, the original use case for encoding