This was a headache to work out, big thanks to the lack of documentation on .xexp files... a ton of guesswork was involved here but luckily it turned out well.
I did have to make some pretty major changes to the way XEX files are loaded though.
Previously it'd just load everything in one go: XEX headers -> decrypt/decompress data -> load imports/symbols -> set loader data table entries, etc...
Now it's changed to something like this:
- Load base XEX headers + decrypted/decompressed image data, return X_STATUS_PENDING
- In the LoadFromFile call used to load the XEX, search for XEXP patch file (only .xexp in same folder atm)
- If patch exists: load XEXP, decrypt headers/data, apply patch to base XEX, dispose of XEXP
- Finish XEX load via LoadXexContinue() (handles imports/symbols/loader data...)
This saves us from needing to reset the imports/function/symbol stuff after patching (since all the XEX code will be a lot different), but I'm not really sure if I went about it the best way.
Code is mainly just copy/pasted from kernel/util/xex2.cc, I've tried fixing it up to work better in a class, but there's probably some things I missed.
Also includes some minor improvements to the XEX loader, like being able to try both XEX keys (retail/devkit) automatically, and some fixes to how the base address is determined.
(Previously there was code that would get base address from optional header, code that'd get it from xex_security_info, code that'd use a stored base address value...
Now everything reads it from a single stored value instead, which is set either from the xex_security_info, or if it exists from the optional header instead.
Maybe this can help improve compatibility with any weird XEX's that don't have a base address optional header?)
Compressed XEX loader also has some extra checks to make sure the compressed data hash matches what's expected.
Might increase loading times by a fraction, but could save reports from people unknowingly using corrupt XEXs.
(still no checks for non-compressed data though, maybe need to compare data with xex_security_info->ImageHash?)
This is a regression in functionality and performance, but a much better
foundation for the future of the project (I think). It can run basic
apps under an SSA interpreter but doesn't support some of the features
required to do real 360 apps yet.
