nxnative-easy/docs/agents

Porting a Switch title: agent guide

These pages are for an agent asked to analyse a Switch NSP and port it with the native-execution approach of this repository and d2r-mobile: the game's own aarch64 code runs natively on Apple hardware, a rewriter patches only the instructions Apple's kernel cannot run, the host replaces Horizon system services, and NVN is reimplemented on Metal.

Everything here was learned on two titles: Diablo II: Resurrected (SDK ~12, NVN 53, the original target of d2r-mobile) and Super Mario Bros. Wonder (SDK 16.2.0, NVN 55, this repository; its update 1.2.1 uses SDK 16.2.12). Where the two differed, both are given; a third title will differ again, so treat every number below as "measure it, don't assume it".

Page	Covers
01-extract.md	Keys, NSP → NCA → ExeFS / RomFS, update NSPs, the workspace layout
02-survey.md	Static survey of a new title before touching the host: SDK version, imports vs. host hooks, SVCs, instructions to rewrite, NVN surface, data containers, Ghidra / REA setup
03-bringup.md	Getting the host to boot the game: the run loop, how to read the log, and a catalogue of every failure pattern met so far with its root cause and fix
04-graphics.md	NVN on Metal for a new title: object sizes, shader containers and keys, binding layouts, bindless textures, depth mode, index sizes, swizzle, transient render targets, the diagnostic switches
05-debugging.md	Recipes: crash reports, lldb scripts, Ghidra headless decompilation, objdump, memory growth, render-pass and texture dumps, on-device diagnostics, offline pipeline link checks

Ground rules

• Bring your own files. Keys, NSPs and anything extracted from them stay in the user's workspace (~/<title>-work), never in the repository, never in a commit, never printed. Print key names and lengths only.
• Measure, then change. Each fix in this repository started from a concrete observation (a crash address and its decompilation, a census over all shaders, a memory profile). Write the evidence into the code comment next to the fix, the way the existing code does; the next title will need it.
• One repository, one profile per title. smbw-mobile started as a copy of d2r-mobile's generic parts. Title- or SDK-specific constants live in the game profile dm/games/<id>/ (dm/games/README.md). That covers program ID, known builds, modules, address-space partition, NVN driver tables, the shader tables and the app identity. The code reads the profile through game_profile.h (host) or dm/games/game.py (tools). Behaviour that fits only one title's code is gated by that title's build ID (dm_main_build()), never left on for every title. Some things are still built into the translator: the texture / sampler handle bases and the depth mode (see 04). dmsh_build.py refuses a profile whose bases differ from the translator's.
• Keep the bilingual comment style of the code base (Chinese line, then the English line), and the 【红】 prefix for red log lines that mark something unimplemented or wrong.
• Test where it runs. The Mac host (dm/host/dmhost) is the development loop; the iOS app reuses the same host and graphics code. Never claim something works on iOS without running it there.

Checklist for a new title

1. Run dm/ios/tools/build_ipa_from_nsp.py on the title's NSP folder. With no profile for its title ID, it writes <NSP folder>/<title ID>_survey/survey.md:

   • modules and build IDs, SDK version and components, engine and graphics API markers;
   • RomFS containers;
   • the rewrite-site census and imports vs. host hooks.

   It extracts only the code modules plus a RomFS list.

2. Extract base (and update, if in scope) — 01. Finish the survey — 02. Write down: SDK version, NVN API version, module list, imports the host lacks, SVCs, instruction census, NVN loader pattern, shader containers.

3. Add a game profile dm/games/<id>/game.tsv (start from smbw/game.tsv: identity, build rows, modules; keep the memory / NVN values until they are measured) and build the host for it with make -C dm/host GAME=<id>.

4. Run the rewriter (DM_RULESET=native) and check its counts against insn_census.py.

5. Boot on the Mac and iterate on the failure catalogue in 03 until the game reaches its frame loop.

6. Extract and translate the shaders, find the binding layout by census, and get the first frame — 04.

7. Check memory over a minute of running (footprint, the host's memory report line); fix growth before moving on.

8. Input, audio, then the iOS bundle (d2r-mobile's dm/ios, RomFS inside the app).

9. Test on a phone: an unsigned IPA the user sideloads, switches through env.txt, results through Documents/log.txt (05). Several bugs only showed there (the command-buffer byte and the audio buffer size in 03, pipeline link failures in later levels in 04).

10. For a game update: extract it over the base game, diff the imports, carry the per-build addresses over, and rebuild the shader tables for both versions (01).