JIT is a sysmodule for run-time code generation (allowing for overlapping R-X and RW- views of memory). This was added to retail with [10.0.0+]. This was also supported in sdknso for a number of versions prior.
nnMain just initializes ro:1, then starts hosting the service from the main-thread with max_sessions=1 (threads are not created for service-hosting).
This is intended to only be used by Applications. The initialization in sdknso uses PrepareForJit at the start. sdknso later uses svcCreateCodeMemory.
This loads the user-specified NRO into sysmodule-context ("DllPlugin"), and calls various symbols from that NRO. It seems the code writing (in cmd GenerateCode) is done via symbol-calling, allowing the NRO to handle input_buffer->code translation+writing.
jit:u
This is "nn::jitsrv::IJitService".
| Cmd | Name | Notes |
|---|---|---|
| 0 | CreateJitEnvironment | Returns an #IJitEnvironment |
IJitEnvironment
This is "nn::jitsrv::IJitEnvironment".
| Cmd | Name |
|---|---|
| 0 | GenerateCode |
| 1 | Control |
| 1000 | LoadPlugin |
| 1001 | GetCodeAddress |