Wiinject

Wiinject is a cross-platform tool for injecting ASM hacks into Wii games using Riivolution memory patches. Pass it a folder containing .s PowerPC assembly files (and, if you'd like, .c C files) and a series of injection sites and it will assemble the files and give you a memory file and a series of Riivolution XML memory patches.

Wiinject relies on the Keystone Engine to assemble code and devkitPro to compile C code.

Usage

Prerequisites

Wiinject requires the following to run:

• The .NET 6.0 runtime
• devkitPro if compiling C code

CLI Options

• -f|--folder – The folder where your source files live
• -m|--dolphin-map|--map|--symbols – A Dolphin symbols map for any built-in functions you want to reference by name
• -i|--injection-addresses – The addresses to inject function code at, comma delimited. The code at these addresses should be safe to overwrite.
• -e|--injection-ends – The addresses at which the above injection sites end (are no longer safe to overwrite), comma delimited. If the code is unable to fit in any of these injection sites, an error will be thrown.
• -o|--output-folder – The folder to output the Riivolution patch.xml & assembled ASM bin file to.
• -n|--patch-name – The name of the patch to output. The patch will be output to {output_folder}/Riivolution/{patch_name}.xml and the ASM bin will be output to {output_folder}/{patch_name}/patch.bin.
• -p|--input-patch – The base Riivolution patch that will be modified by Wiinject to contain the memory patches. A blank base template will be created if this is not provided.
• d|devkitpro-path= ‐ The path to a devkitPro installation containing devkitPPC (e.g. C:\devkitPro or /opt/devkitpro)
• --console-output – Rather than producing an ASM patch, simply output the XML to the console. This will still save the ASM bin, however.
• --emit-c – Emits assembled C functions to the console so you can modify your assembly calls to those functions to work with the registries used by the compiler.

Structuring Your Source Code and Preparing Your Initial Patch

Wiinject expects the folder where your source lives to have one subdirectory for each patch element you wish to generate. For example, if you'd like your final Riivolution patch to contain one optional patch for translating the game and another for reducing monster spawns, name one subdirectory something like Translation and the other ReduceMonsterSpawns. Then, place your source files relevant to those patches in those directories.

When preparing your input patch, make sure you set up the options yourself and ensure that the patch names in the options match the names of the subdirectories in your source folder. Finally, add any patch elements that have non-memory patches. Wiinject will automatically create patch elements that don't exist and append to ones that do.

If you've followed along, your input patch should look something like this:

<wiidisc version="1">
  <id game="R42069" />
  <options>
    <section name="Translation">
      <option name="Translation">
        <choice name="Enabled">
          <patch id="Translation" />
        </choice>
      </option>
    </section>
    <section name="Quality of Life">
      <option name="Reduce Monster Spawns">
        <choice name="Enabled">
          <patch id="ReduceMonsterSpawns" />
        </choice>
      </option>
    </section>
  </options>
  <patch id="Translation">
    <folder external="/Game/files" recursive="true" disc="/" />
    <folder external="/Game/files" />
  </patch>
</wiidisc>

Writing ASM

Wiinject uses the Keystone Engine to assemble standard PowerPC assembly. To write an assembly file that Wiinject can parse, however, you need to use special function names.

Here is a sample Wiinject-compatible assembly file:

hook_80017250:
    start:
        add 5,5,0
        mr 26,3
        cmpwi 5,3
        beq end
        li 5,2
    end:
        blr

hook_80017254:
    mr 3,26
    blr

repl_80017260:
    mr 5,25
    li 6,7

ref_801BBB38:
    li 6,7
    blr

The hooks indicate which instructions to replace with a branch instruction to the function provided. The repl indicates a location to start overwriting instructions directly with the instructions provided. The ref indicates a location to write a reference to the function provided (useful for hooking into functions that use bctrl, etc.).

Using Variables in ASM

Wiinject allows for a special notation to store and interact with variables. Variables can be defined anywhere in an ASM file with $variable:, e.g. $array: .skip 16. You can then load that variable into memory with the lv command. lv is resolved to an lis followed by an addi in the assembling process.

Example:

$variable: .int 0
$array: .skip 16

hook_80017250:
    lv 2,$variable
    lv 3,$array
    blr

Writing C

For each ASM file, you may also provide a companion C file to compile and inject methods which may then be called from the ASM. In order to use this functionality, you must install devkitPro and provide Wiinject with the path to the devkitPro installation (e.g. C:\devkitPro or /opt/devkitpro).

Injected C methods are called from the ASM via bl =method_name. The assembly function caller will need to handle stack manipulation and inputs itself. You can expect a compiled C method to accept inputs sequentially starting with r3 and to place its return value in r3. However, in order to verify this, you can use the --emit-c flag while calling Wiinject to view the compiled C code's assembly so you can adjust your assembly caller appropriately.

Here is a sample Wiinject-compatible C file named font_hack.c:

int font_offset(char character)
{
    switch (character)
    {
        case 'A':
            return 0x180;
        case 'I':
        case 'i':
        case 'l':
        case '!':
            return 0x48;
        default:
            return 0x90;
    }
}

And here is its companion ASM file named font_hack.s:

hook_8001726C:
    stwu 1,-24(1)
    mflr 0
    stw 0,20(1)
    stw 31,16(1)
    mr 31,1
    stw 9,12(1)
    stw 3,8(1)
    mr 3,26
    cmpwi 3,75
    bl =font_offset
    lwz 0,20(1)
    mtlr 0
    mr 0,3
    lwz 9,12(1)
    lwz 3,8(1)
    addi 11,31,24
    lwz 31,-4(11)
    mr 1,11
    blr

Using Symbols

You can provide Wiinject with a Dolphin symbols map and use that to reference functions existing in the ASM in the same way you would reference C functions.

Map file:

.text section layout
80004000 00000050 80004000 0 memcpy

Assembly:

hook_8001726C:
    stwu 1,-24(1)
    mflr 0
    stw 0,20(1)
    bl =memcpy
    lwz 0,20(1)
    mtlr 0
    addi 1,24
    blr

Limitations

• Wiinject only supports the bl command for C functions or functions defined in your Dolphin symbols map; functions defined in assembly cannot currently be branched to.
• The paired single operators are not available.

Source & Building

Wiinject.sln can be opened in Visual Studio 2022 or (presumably) later and built from there. You can also build Wiinject.sln from the command line on any platform that supports .NET 6.0 with dotnet build in the root directory. If you're struggling to get Wiinject to run properly after compilation, try explicitly running with the RID of the platform you're building for (e.g. dotnet build -r osx-64 Wiinject/Wiinject.csproj).