af21b8f3c7
It is not an external component, and it makes paths needlessly long. Ryan seemed amenable to this when we discussed on IRC earlier. Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
2.1 KiB
FEXCore custom CPU backends
Custom CPU backends can be useful for testing purposes or wanting to support situations that FEXCore doesn't currently understand.
The FEXCore::Context namespace provides a SetCustomCPUBackendFactory function for providing a factory function pointer to the core. This function will be used if the DEFAULTCORE configuration option is set to CUSTOM.
If the guest code creates more threads then the CPU factory function will be invoked for creating a CPUBackend per thread. If you don't want a unique CPUBackend object per thread then that needs to be handled by the user.
It's recommended to store the pointers provided to the factory function for later use.
FEXCore::Context::Context* - Is a pointer to previously generated context object
FEXCore::Core::ThreadState* - Is a pointer to a thread's state. Lives for as long as the guest thread is alive.
To use this factory, one must override the provided FEXCore::CPU::CPUBackend class with a custom one. This factory function then should return a newly allocated class.
FEXCore::CPU::CPUBackend::GetName - Returns an std::string for the name of this core
FEXCore::CPU::CPUBackend::CompileCode - Provides the CPUBackend with potentially an IR and DebugData for compiling code. Returns a pointer that needs to be long lasting to a piece of code that will be executed for the particular RIP.
Both IR and DebugData can be null if NeedsOpDispatch returns false
FEXCore::CPU::CPUBackend::MapRegion - This function needs to be implemented if the CPUBackend needs to map host facing memory in to the backend. Allows setting up virtual memory mapping if required
FEXCore::CPU::CPUBackend::Initialize - Called after the guest memory is initialized and all state is ready for the code to start initializing. Gets called just before the CPUBackend starts executing code for the first time.
FEXCore::CPU::CPUBackend::NeedsOpDispatch - Tells FEXCore if the backend needs the FEXCore IR and DebugData provided to it. This can be useful if FEXCore hits something it doesn't understand but it doesn't matter since the CPUBackend can still understand it from raw x86-64 (ex VM based CPU backend).