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The BPS format allows distributing patches that are smaller and that do not contain copyrighted content if data is relocated (unlike non-trivial IPS patches). This is essential for games such as Majora's Mask 3D that have three barely different code revisions. Supporting all three versions would demand an unreasonable amount of work; with BPS patches only one version has to be supported. The patcher is written in C++ in order to make it possible to share the implementation with Citra and because a C version would be a lot more ugly and tedious to write. The patcher is non-intrusive for the rest of the codebase and self-contained so hopefully that isn't an issue. This adds roughly ~0x500 bytes of code to the loader sysmodule. Code looks reasonably optimised (in IDA). Tested and works on an o3DS. |
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| LICENSE | ||
| loader.rsf | ||
| Makefile | ||
| README.md | ||
3DS Loader Replacement
This is an open source implementation of 3DS loader system module--with
additional features. The current aim of the project is to provide a nice
entry point for patching 3DS modules.
Roadmap
Right now, this can serve as an open-source replacement for the built in loader.
There is additional support for patching any executable after it's loaded but
before it starts. For example, you can patch menu to skip region checks and
have region free game launching directly from the home menu. There is also
support for SDMC reading (not found in original loader implementation) which
means that patches can be loaded from the SD card. Ultimately, there would be
a patch system that supports easy loading of patches from the SD card.
Build
You need a working 3DS build environment with a fairly recent copy of devkitARM, ctrulib, and makerom. If you see any errors in the build process, it's likely that you're using an older version.
Currently, there is no support for FIRM building, so you need to do some steps manually. First, you have to add padding to make sure the NCCH is of the right size to drop in as a replacement. A hacky way is this patch which adds junk data. Play around with the size value to get the NCCH to be the exact same size as the one found in your decrypted FIRM dump.
Once you have a NCCH of the right size, just replace it in your decrypted FIRM and find a way to launch it (for example with ReiNAND).