no one will know the pain i go through

.clang-format

@@ -22,7 +22,7 @@ BinPackParameters: true
 BreakConstructorInitializers: BeforeColon
 BreakStringLiterals: false
 
-ColumnLimit: 100
+ColumnLimit: 150
 CompactNamespaces: false
 
 ConstructorInitializerAllOnOneLineOrOnePerLine: true

native/projects/lucore/include/lucore/Types.hpp

@@ -2,14 +2,14 @@
 
 //namespace lucore {
 	using u8 = std::uint8_t;
-	using s8 = std::int8_t;
+	using i8 = std::int8_t;
 	using u16 = std::uint16_t;
-	using s16 = std::int16_t;
+	using i16 = std::int16_t;
 	using u32 = std::uint32_t;
-	using s32 = std::int32_t;
+	using i32 = std::int32_t;
 	using u64 = std::uint64_t;
-	using s64 = std::int64_t;
+	using i64 = std::int64_t;
 	using usize = std::size_t;
-	using ssize = std::intptr_t;
+	using isize = std::intptr_t;
 
 //} // namespace lucore

native/projects/riscv/include/riscv/Bus.hpp

@@ -74,21 +74,21 @@ namespace riscv {
 
 			virtual BasicType Type() const override { return BasicType::PlainMemory; }
 
-			virtual AddressT Base() const = 0;
+			virtual Address Base() const = 0;
 			
 			/// How many bytes does this device occupy of address space? 
 			/// This should not change during execution.
-			virtual AddressT Size() const = 0;
+			virtual Address Size() const = 0;
 
 			/// Peek() -> reads a value from this device.
-			virtual u8 PeekByte(AddressT address) = 0;
+			virtual u8 PeekByte(Address address) = 0;
-			virtual u16 PeekShort(AddressT address) = 0;
+			virtual u16 PeekShort(Address address) = 0;
-			virtual u32 PeekWord(AddressT address) = 0;
+			virtual u32 PeekWord(Address address) = 0;
 
 			/// Poke() -> Writes a value to this device's space in memory
-			virtual void PokeByte(AddressT address, u8 value) = 0;
+			virtual void PokeByte(Address address, u8 value) = 0;
-			virtual void PokeShort(AddressT address, u16 value) = 0;
+			virtual void PokeShort(Address address, u16 value) = 0;
-			virtual void PokeWord(AddressT address, u32 value) = 0;
+			virtual void PokeWord(Address address, u32 value) = 0;
 		};
 
 		/// A device in the MMIO region.
@@ -98,14 +98,14 @@ namespace riscv {
 
 			virtual BasicType Type() const override { return BasicType::Mmio; }
 
-			virtual AddressT Base() const;
+			virtual Address Base() const = 0;
 
 			/// How many bytes does this device occupy of address space? 
 			/// This should not change during execution.
-			virtual AddressT Size() const = 0;
+			virtual Address Size() const = 0;
 
-			virtual u32 Peek(AddressT address) = 0;
+			virtual u32 Peek(Address address) = 0;
-			virtual void Poke(AddressT address, u32 value) = 0;
+			virtual void Poke(Address address, u32 value) = 0;
 		};
 
 		/// Bus destructor.
@@ -128,20 +128,20 @@ namespace riscv {
 		/// Clock all clocked devices mapped onto the bus..
 		void Clock();
 
-		u8 PeekByte(AddressT address);
+		u8 PeekByte(Address address);
-		u16 PeekShort(AddressT address);
+		u16 PeekShort(Address address);
-		u32 PeekWord(AddressT address);
+		u32 PeekWord(Address address);
 
-		void PokeByte(AddressT address, u8 value);
+		void PokeByte(Address address, u8 value);
-		void PokeShort(AddressT address, u16 value);
+		void PokeShort(Address address, u16 value);
-		void PokeWord(AddressT address, u32 value);
+		void PokeWord(Address address, u32 value);
 
 		CPU* GetCPU() { return cpu; }
 
 	   private:
 
 	   	// TODO: version which takes Device::BasicType
-		Bus::Device* FindDeviceForAddress(AddressT address) const;
+		Bus::Device* FindDeviceForAddress(Address address) const;
 
 		CPU* cpu;
 
@@ -150,8 +150,8 @@ namespace riscv {
 
 		// TODO: if these end up being a hotpath replace with ankerl::unordered_dense
 		// (or just use the [devices] vector, probably.)
-		std::unordered_map<AddressT, MemoryDevice*> mapped_devices;
+		std::unordered_map<Address, MemoryDevice*> mapped_devices;
-		std::unordered_map<AddressT, MmioDevice*> mmio_devices;
+		std::unordered_map<Address, MmioDevice*> mmio_devices;
 	};
 
 } // namespace riscv

native/projects/riscv/include/riscv/CPU.hpp

@@ -9,6 +9,7 @@ namespace riscv {
 		bool Clocked() const override { return true; }
 		void Clock() override;
 
+		/// Trap the CPU. Bus devices can call this.
 		void Trap(u32 trapCode);
 		inline void Trap(TrapCode trapCode) { Trap(static_cast<u32>(trapCode)); }
 
@@ -16,6 +17,7 @@ namespace riscv {
 
 		// TODO: Handlers for CSR read/write (if we need it?)
 
+		/// CPU state
 		GeneralPurposeRegisters gpr;
 		u32 pc;
 		u32 mstatus;
@@ -38,9 +40,9 @@ namespace riscv {
 
 	   private:
 		/// Set by [CPU::Trap] to tell the CPU it was trapped.
-		/// Codes with the sign bit set are actually interrupts,
-		/// and are processed first.
 		bool trapped { false };
+
+		/// Set by [CPU::Trap] for the trap code.
 		u32 trapCode { 0 };
 
 		u32 Step(u32 instCount);

native/projects/riscv/include/riscv/CPUTypes.hpp

@@ -3,10 +3,10 @@
 
 namespace riscv {
 
-	// Note that
+	/// Most possible trap codes.
 	enum class TrapCode : u32 {
 		InstructionAddressMisaligned,
-		InstructionAddressFault,
+		InstructionAccessFault,
 		IllegalInstruction,
 		Breakpoint, // I see what you did there ;)
 		LoadAddressMisaligned,

native/projects/riscv/include/riscv/Devices/ClntDevice.hpp

@@ -7,17 +7,17 @@ namespace riscv::devices {
 	/// Partial implementation of a CLINT.
 	/// The timer device is implemented, SIP is not.
 	struct ClntDevice : public Bus::MmioDevice {
-		constexpr static AddressT BASE_ADDRESS = 0x11000000;
+		constexpr static Address BASE_ADDRESS = 0x11000000;
 
-		AddressT Base() const override { return BASE_ADDRESS; }
+		Address Base() const override { return BASE_ADDRESS; }
-		AddressT Size() const override { return 0xbfff; }
+		Address Size() const override { return 0xbfff; }
 
 		bool Clocked() const override { return true; } 
 		void Clock() override;
 
 
-		u32 Peek(AddressT address) override;
+		u32 Peek(Address address) override;
-		void Poke(AddressT address, u32 value) override;
+		void Poke(Address address, u32 value) override;
 
 	private:
 		u32 timerCountHigh;

native/projects/riscv/include/riscv/Devices/RamDevice.hpp

@@ -6,31 +6,31 @@ namespace riscv::devices {
 
 	/// A block of RAM which can be used by the CPU.
 	struct RamDevice : public Bus::MemoryDevice {
-		RamDevice(AddressT base, AddressT size);
+		RamDevice(Address base, Address size);
 		virtual ~RamDevice();
 
 		// Implementation of Device interface
 
-		AddressT Base() const override;
+		Address Base() const override;
-		AddressT Size() const override;
+		Address Size() const override;
 
 
-		u8 PeekByte(AddressT address) override;
+		u8 PeekByte(Address address) override;
-		u16 PeekShort(AddressT address) override;
+		u16 PeekShort(Address address) override;
-		u32 PeekWord(AddressT address) override;
+		u32 PeekWord(Address address) override;
 
-		void PokeByte(AddressT address, u8 value) override;
+		void PokeByte(Address address, u8 value) override;
-		void PokeShort(AddressT address, u16 value) override;
+		void PokeShort(Address address, u16 value) override;
-		void PokeWord(AddressT address, u32 value) override;
+		void PokeWord(Address address, u32 value) override;
 
 	   private:
 		/// helper used for implementing Peek/Poke API
 		template <class T>
-		constexpr usize AddressToIndex(AddressT address) {
+		constexpr usize AddressToIndex(Address address) {
 			return ((address - memoryBase) % memorySize) / sizeof(T);
 		}
 
-		AddressT memoryBase {};
+		Address memoryBase {};
 
 		u8* memory {};
 		usize memorySize {};

native/projects/riscv/include/riscv/Devices/SysconDevice.hpp

@@ -7,14 +7,14 @@ namespace riscv { struct System; }
 namespace riscv::devices {
 	/// RISC-V SYSCON device. This will later talk to the system to tell it things.
 	struct SysconDevice : public Bus::MmioDevice {
-		constexpr static AddressT BASE_ADDRESS = 0x11100000;
+		constexpr static Address BASE_ADDRESS = 0x11100000;
 
 		SysconDevice(System* system);
 
-		AddressT Size() const override { return sizeof(u32); } // I think this is right?
+		Address Size() const override { return sizeof(u32); } // I think this is right?
 
-		u32 Peek(AddressT address) override;
+		u32 Peek(Address address) override;
-		void Poke(AddressT address, u32 value) override;
+		void Poke(Address address, u32 value) override;
 	private:
 		System* system;
 	};

native/projects/riscv/include/riscv/System.hpp

@@ -10,7 +10,7 @@ namespace riscv {
 	struct System {
 		/// Create a basic system with the basic periphials created.
 		/// All other periphials should be managed by the creator of this System
-		static System* WithMemory(AddressT ramSize);
+		static System* WithMemory(Address ramSize);
 
 		~System();
 

native/projects/riscv/include/riscv/Types.hpp

@@ -6,8 +6,8 @@
 namespace riscv {
 
 	/// A type that can repressent address space or address space offsets.
-	using AddressT = u32;
+	using Address = u32;
+
 
-	
 
 } // namespace riscv

native/projects/riscv/src/Bus.cpp

@@ -61,7 +61,7 @@ namespace riscv {
 		cpu->Clock();
 	}
 
-	u8 Bus::PeekByte(AddressT address) {
+	u8 Bus::PeekByte(Address address) {
 		if(auto dev = FindDeviceForAddress(address); dev)
 			return dev->Upcast<MemoryDevice*>()->PeekByte(address);
 		else {
@@ -70,7 +70,7 @@ namespace riscv {
 		}
 	}
 
-	u16 Bus::PeekShort(AddressT address) {
+	u16 Bus::PeekShort(Address address) {
 		if(auto dev = FindDeviceForAddress(address); dev)
 			return dev->Upcast<MemoryDevice*>()->PeekShort(address);
 		else {
@@ -79,7 +79,7 @@ namespace riscv {
 		}
 	}
 
-	u32 Bus::PeekWord(AddressT address) {
+	u32 Bus::PeekWord(Address address) {
 		if(auto dev = FindDeviceForAddress(address); dev) {
 			if(dev->IsA<MmioDevice*>())
 				return dev->Upcast<MmioDevice*>()->Peek(address);
@@ -91,7 +91,7 @@ namespace riscv {
 		}
 	}
 
-	void Bus::PokeByte(AddressT address, u8 value) {
+	void Bus::PokeByte(Address address, u8 value) {
 		if(auto dev = FindDeviceForAddress(address); dev)
 			return dev->Upcast<MemoryDevice*>()->PokeByte(address, value);
 		else {
@@ -99,7 +99,7 @@ namespace riscv {
 		}
 	}
 
-	void Bus::PokeShort(AddressT address, u16 value) {
+	void Bus::PokeShort(Address address, u16 value) {
 		if(auto dev = FindDeviceForAddress(address); dev)
 			return dev->Upcast<MemoryDevice*>()->PokeShort(address, value);
 		else {
@@ -107,7 +107,7 @@ namespace riscv {
 		}
 	}
 
-	void Bus::PokeWord(AddressT address, u32 value) {
+	void Bus::PokeWord(Address address, u32 value) {
 		if(auto dev = FindDeviceForAddress(address); dev) {
 			if(dev->IsA<MmioDevice*>())
 				dev->Upcast<MmioDevice*>()->Poke(address, value);
@@ -118,8 +118,8 @@ namespace riscv {
 		}
 	}
 
-	Bus::Device* Bus::FindDeviceForAddress(AddressT address) const {
+	Bus::Device* Bus::FindDeviceForAddress(Address address) const {
-		auto try_find_device = [&](auto container, AddressT address) {
+		auto try_find_device = [&](auto container, Address address) {
 			return std::find_if(container.begin(), container.end(), [&](const auto& pair) {
 				return
 				// We can shorcut region checking if the requested addess matches base address.

native/projects/riscv/src/CPU.cpp

@@ -1,8 +1,14 @@
-#include <riscv/CPU.hpp>
+//! Portions of this code are copyright 2022 Charles Lohr (CNLohr).
+
 #include <riscv/Bus.hpp>
+#include <riscv/CPU.hpp>
+
+#include "riscv/CPUTypes.hpp"
 
 namespace riscv {
 
+	constexpr static Address RamImageOffset = 0x80000000;
+
 	void CPU::Clock() {
 		// do the thing
 		Step(1024);
@@ -16,66 +22,547 @@ namespace riscv {
 		// If this is because of an interrupt
 		if(trapCode & 0x80000000) {
 			// Set MIP.MEIP.
-			//mip |= 1 << 11;
+			// mip |= 1 << 11;
 			// Always clear WFI bit.
-			extraflags &= ~4; 
+			extraflags &= ~4;
 		}
 	}
 
 	void CPU::TimerInterrupt() {
 		// Set MIP.MTIP.
 		mip |= 1 << 7;
-		//extraflags &= ~4; 
+		// extraflags &= ~4;
-		//trapped = true;
+		// trapped = true;
-		//trapCode = 0x80000007;
+		// trapCode = 0x80000007;
 	}
 
 	u32 CPU::Step(u32 instCount) {
 		auto interruptsInFlight = [&]() {
-			return 
+			return (mip & (1 << 7) /*|| mip & (1 << 11)*/) && (mie & (1 << 7) /*|| mie & (1 << 11)*/) && (mstatus & 0x8 /*mie*/);
-				(mip & (1 << 7) /*|| mip & (1 << 11)*/) &&
-				(mie & (1 << 7) /*|| mie & (1 << 11)*/) &&
-				(mstatus & 0x8 /*mie*/);
 		};
 
 		// Don't run if waiting for an interrupt
 		if(extraflags & 4)
 			return 1;
 
+		u32 rdid = 0;
+		u32 rval = 0;
+		u32 pc = this->pc;
+		u32 cycle = this->cyclel;
+
 		if(interruptsInFlight()) {
 			Trap(0x80000007);
 		} else {
-			u32 rval = 0;
-			u32 pc = this->pc;
-			u32 cycle = this->cyclel;
-
 			for(u32 iInst = 0; iInst < instCount; ++iInst) {
-				
+				auto ofs_pc = pc - RamImageOffset;
 				cycle++;
 
-				if(pc & 3) {
+				if(ofs_pc & 3) {
 					Trap(TrapCode::InstructionAddressMisaligned);
 					break;
 				} else {
-					auto ir = bus->PeekWord(pc);
+					auto ir = bus->PeekWord(ofs_pc);
-					auto rdid = (ir >> 7) & 0x1f;
+					if(trapped) {
-					//switch(ir & 0x7f) {
+						// Overwrite the trap that the bus generated. This might not really work out
+						// in practice but should at least kind-of replicate behaviour (our address
+						// space is emulated using the [Bus] class, so there is no heap write issue
+						// that could be caused by leaving it unbound).
+						Trap(TrapCode::InstructionAccessFault);
+						rval = ofs_pc + RamImageOffset;
+						break;
+					}
 
-					//}
+					rdid = (ir >> 7) & 0x1f;
+
+					// Do the thing!
+					switch(ir & 0x7f) {
+						case 0x37: // lui
+							rval = (ir & 0xfffff000);
+							break;
+
+						case 0x17: // auipc
+							rval = pc + (ir & 0xfffff000);
+							break;
+
+						case 0x6f: { // jal
+							i32 reladdy = ((ir & 0x80000000) >> 11) | ((ir & 0x7fe00000) >> 20) | ((ir & 0x00100000) >> 9) | ((ir & 0x000ff000));
+
+							// Sign extend in this case
+							if(reladdy & 0x00100000)
+								reladdy |= 0xffe00000;
+							rval = pc + 4;
+							pc = pc + reladdy - 4;
+							break;
+						}
+
+						case 0x67: { // jalr
+							u32 imm = ir >> 20;
+							i32 imm_se = imm | ((imm & 0x800) ? 0xfffff000 : 0);
+							rval = pc + 4;
+							pc = ((gpr[((ir >> 15) & 0x1f)] + imm_se) & ~1) - 4;
+							break;
+						}
+
+						case 0x63: { // branch
+							u32 immm4 = ((ir & 0xf00) >> 7) | ((ir & 0x7e000000) >> 20) | ((ir & 0x80) << 4) | ((ir >> 31) << 12);
+							if(immm4 & 0x1000)
+								immm4 |= 0xffffe000;
+							i32 rs1 = gpr[(ir >> 15) & 0x1f];
+							i32 rs2 = gpr[(ir >> 20) & 0x1f];
+							immm4 = pc + immm4 - 4;
+							rdid = 0;
+							switch((ir >> 12) & 0x7) {
+								// BEQ, BNE, BLT, BGE, BLTU, BGEU
+								case 0: // BEQ
+									if(rs1 == rs2)
+										pc = immm4;
+									break;
+								case 1: // BNE
+									if(rs1 != rs2)
+										pc = immm4;
+									break;
+
+								case 4: // BLT
+									if(rs1 < rs2)
+										pc = immm4;
+									break;
+
+								case 5: // BGE
+									if(rs1 >= rs2)
+										pc = immm4;
+									break;
+
+								case 6: // BLTU
+									if((uint32_t)rs1 < (uint32_t)rs2)
+										pc = immm4;
+									break;
+
+								case 7: // BGEU
+									if((uint32_t)rs1 >= (uint32_t)rs2)
+										pc = immm4;
+									break;
+								default:
+									Trap(TrapCode::IllegalInstruction);
+							}
+							break;
+						}
+
+						case 0x03: { // load
+							u32 rs1 = gpr[(ir >> 15) & 0x1f];
+							u32 imm = ir >> 20;
+							i32 imm_se = imm | ((imm & 0x800) ? 0xfffff000 : 0);
+							u32 rsval = rs1 + imm_se;
+
+							rsval -= RamImageOffset;
+
+							switch((ir >> 12) & 0x7) {
+								// LB, LH, LW, LBU, LHU
+								case 0:
+									rval = (i8)bus->PeekByte(rsval);
+									break;
+								case 1:
+									rval = (i16)bus->PeekShort(rsval);
+									break;
+								case 2:
+									rval = bus->PeekWord(rsval);
+									break;
+								case 4:
+									rval = bus->PeekByte(rsval);
+									break;
+								case 5:
+									rval = bus->PeekShort(rsval);
+									break;
+								default:
+									Trap(TrapCode::IllegalInstruction);
+									break;
+							}
+
+							if(trapped) {
+								rval = rsval + RamImageOffset;
+							}
+							break;
+						}
+						case 0x23: { // store
+							u32 rs1 = gpr[(ir >> 15) & 0x1f];
+							u32 rs2 = gpr[(ir >> 20) & 0x1f];
+							u32 addy = ((ir >> 7) & 0x1f) | ((ir & 0xfe000000) >> 20);
+							if(addy & 0x800)
+								addy |= 0xfffff000;
+							addy += rs1 - RamImageOffset;
+							rdid = 0;
+
+							switch((ir >> 12) & 0x7) {
+								// SB, SH, SW
+								case 0:
+									bus->PokeByte(addy, rs2);
+									break;
+								case 1:
+									bus->PokeShort(addy, rs2);
+									break;
+								case 2:
+									bus->PokeWord(addy, rs2);
+									break;
+								default:
+									Trap(TrapCode::IllegalInstruction);
+							}
+
+							if(trapped) {
+								rval = addy + RamImageOffset;
+							}
+							break;
+						}
+
+						case 0x13:	 // op-imm
+						case 0x33: { // op
+							u32 imm = ir >> 20;
+							imm = imm | ((imm & 0x800) ? 0xfffff000 : 0);
+							u32 rs1 = gpr[(ir >> 15) & 0x1f];
+							u32 is_reg = !!(ir & 0x20);
+							u32 rs2 = is_reg ? gpr[imm & 0x1f] : imm;
+
+							if(is_reg && (ir & 0x02000000)) {
+								switch((ir >> 12) & 7) // 0x02000000 = RV32M
+								{
+									case 0:
+										rval = rs1 * rs2;
+										break; // MUL
+
+									case 1:
+										rval = ((i64)((i32)rs1) * (i64)((i32)rs2)) >> 32;
+										break; // MULH
+									case 2:
+										rval = ((i64)((i32)rs1) * (u64)rs2) >> 32;
+										break; // MULHSU
+									case 3:
+										rval = ((u64)rs1 * (u64)rs2) >> 32;
+										break; // MULHU
+
+									case 4:
+										if(rs2 == 0)
+											rval = -1;
+										else
+											rval = ((i32)rs1 == INT32_MIN && (i32)rs2 == -1) ? rs1 : ((i32)rs1 / (i32)rs2);
+										break; // DIV
+									case 5:
+										if(rs2 == 0)
+											rval = 0xffffffff;
+										else
+											rval = rs1 / rs2;
+										break; // DIVU
+									case 6:
+										if(rs2 == 0)
+											rval = rs1;
+										else
+											rval = ((i32)rs1 == INT32_MIN && (i32)rs2 == -1) ? 0 : ((u32)((i32)rs1 % (i32)rs2));
+										break; // REM
+									case 7:
+										if(rs2 == 0)
+											rval = rs1;
+										else
+											rval = rs1 % rs2;
+										break; // REMU
+								}
+							} else {
+								// These could be either op-immediate or op commands.  Be careful.
+								switch((ir >> 12) & 7) {
+									case 0:
+										rval = (is_reg && (ir & 0x40000000)) ? (rs1 - rs2) : (rs1 + rs2);
+										break;
+									case 1:
+										rval = rs1 << (rs2 & 0x1F);
+										break;
+									case 2:
+										rval = (i32)rs1 < (i32)rs2;
+										break;
+									case 3:
+										rval = rs1 < rs2;
+										break;
+									case 4:
+										rval = rs1 ^ rs2;
+										break;
+									case 5:
+										rval = (ir & 0x40000000) ? (((i32)rs1) >> (rs2 & 0x1F)) : (rs1 >> (rs2 & 0x1F));
+										break;
+									case 6:
+										rval = rs1 | rs2;
+										break;
+									case 7:
+										rval = rs1 & rs2;
+										break;
+								}
+							}
+							break;
+						}
+
+						case 0x0f:	  // 0b0001111 (ifenze?)
+							rdid = 0; // fencetype = (ir >> 12) & 0b111; We ignore fences in this impl.
+							break;
+
+						case 0x73: { // Zifencei+Zicsr  (0b1110011)
+
+							u32 csrno = ir >> 20;
+							u32 microop = (ir >> 12) & 0x7;
+							// Zicsr
+							if((microop & 3)) {
+								int rs1imm = (ir >> 15) & 0x1f;
+								u32 rs1 = gpr[rs1imm];
+								u32 writeval = rs1;
+
+								// https://raw.githubusercontent.com/riscv/virtual-memory/main/specs/663-Svpbmt.pdf
+								// Generally, support for Zicsr
+								switch(csrno) {
+									case 0x340:
+										rval = mscratch;
+										break;
+									case 0x305:
+										rval = mtvec;
+										break;
+									case 0x304:
+										rval = mie;
+										break;
+									case 0xC00:
+										rval = cycle;
+										break;
+									case 0x344:
+										rval = mip;
+										break;
+									case 0x341:
+										rval = mepc;
+										break;
+									case 0x300:
+										rval = mstatus;
+										break; // mstatus
+									case 0x342:
+										rval = mcause;
+										break;
+									case 0x343:
+										rval = mtval;
+										break;
+									case 0xf11:
+										rval = 0xff0ff0ff;
+										break; // mvendorid
+									case 0x301:
+										rval = 0x40401101;
+										break; // misa (XLEN=32, IMA+X)
+									// case 0x3B0: rval = 0; break; //pmpaddr0
+									// case 0x3a0: rval = 0; break; //pmpcfg0
+									// case 0xf12: rval = 0x00000000; break; //marchid
+									// case 0xf13: rval = 0x00000000; break; //mimpid
+									// case 0xf14: rval = 0x00000000; break; //mhartid
+									default:
+										// MINIRV32_OTHERCSR_READ(csrno, rval);
+										break;
+								}
+
+								switch(microop) {
+									case 1:
+										writeval = rs1;
+										break; // CSRRW
+									case 2:
+										writeval = rval | rs1;
+										break; // CSRRS
+									case 3:
+										writeval = rval & ~rs1;
+										break; // CSRRC
+									case 5:
+										writeval = rs1imm;
+										break; // CSRRWI
+									case 6:
+										writeval = rval | rs1imm;
+										break; // CSRRSI
+									case 7:
+										writeval = rval & ~rs1imm;
+										break; // CSRRCI
+								}
+
+								switch(csrno) {
+									case 0x340:
+										mscratch = writeval;
+										break;
+									case 0x305:
+										mtvec = writeval;
+										break;
+									case 0x304:
+										mie = writeval;
+										break;
+									case 0x344:
+										mip = writeval;
+										break;
+									case 0x341:
+										mepc = writeval;
+										break;
+									case 0x300:
+										mstatus = writeval;
+										break; // mstatus
+									case 0x342:
+										mcause = writeval;
+										break;
+									case 0x343:
+										mtval = writeval;
+										break;
+									// case 0x3a0: break; //pmpcfg0
+									// case 0x3B0: break; //pmpaddr0
+									// case 0xf11: break; //mvendorid
+									// case 0xf12: break; //marchid
+									// case 0xf13: break; //mimpid
+									// case 0xf14: break; //mhartid
+									// case 0x301: break; //misa
+									default:
+										// MINIRV32_OTHERCSR_WRITE(csrno, writeval);
+										break;
+								}
+							} else if(microop == 0x0) { // "SYSTEM" 0b000
+								rdid = 0;
+								if(csrno == 0x105) { // WFI (Wait for interrupts)
+									mstatus |= 8;	 // Enable interrupts
+									extraflags |= 4; // Set inernal WFI bit
+									this->pc = pc + 4;
+									return 1;
+								} else if(((csrno & 0xff) == 0x02)) { // MRET
+									// https://raw.githubusercontent.com/riscv/virtual-memory/main/specs/663-Svpbmt.pdf
+									// Table 7.6. MRET then in mstatus/mstatush sets MPV=0, MPP=0,
+									// MIE=MPIE, and MPIE=1. La
+									//  Should also update mstatus to reflect correct mode.
+									u32 startmstatus = mstatus;
+									u32 startextraflags = extraflags;
+									mstatus = ((startmstatus & 0x80) >> 4) | ((startextraflags & 3) << 11) | 0x80;
+									extraflags = (startextraflags & ~3) | ((startmstatus >> 11) & 3);
+									pc = mepc - 4;
+								} else {
+									switch(csrno) {
+										case 0:
+											if(extraflags & 3) {
+												Trap(TrapCode::EnvCallMMode);
+											} else {
+												Trap(TrapCode::EnvCallUMode);
+											}
+											break;
+										case 1: // breakpoint
+											Trap(TrapCode::Breakpoint);
+											break;
+										default:
+											Trap(TrapCode::IllegalInstruction);
+											break;
+									}
+								}
+							} else
+								Trap(TrapCode::IllegalInstruction);
+							break;
+						}
+						case 0x2f: // RV32A (0b00101111)
+						{
+							u32 rs1 = gpr[(ir >> 15) & 0x1f];
+							u32 rs2 = gpr[(ir >> 20) & 0x1f];
+							u32 irmid = (ir >> 27) & 0x1f;
+
+							// rs1 -= MINIRV32_RAM_IMAGE_OFFSET;
+
+							rs1 -= RamImageOffset;
+
+							// We don't implement load/store from UART or CLNT with RV32A here.
+
+							rval = bus->PeekWord(rs1);
+							if(trapped) {
+								rval = rs1 + RamImageOffset;
+								break;
+							}
+
+							u32 dowrite = 1;
+							switch(irmid) {
+								case 2: // LR.W (0b00010)
+									dowrite = 0;
+									extraflags = (extraflags & 0x07) | (rs1 << 3);
+									break;
+								case 3:												// SC.W (0b00011) (Make sure we have a slot, and, it's
+																					// valid)
+									rval = (extraflags >> 3 != (rs1 & 0x1fffffff)); // Validate that our reservation slot is OK.
+									dowrite = !rval;								// Only write if slot is valid.
+									break;
+								case 1:
+									break; // AMOSWAP.W (0b00001)
+								case 0:
+									rs2 += rval;
+									break; // AMOADD.W (0b00000)
+								case 4:
+									rs2 ^= rval;
+									break; // AMOXOR.W (0b00100)
+								case 12:
+									rs2 &= rval;
+									break; // AMOAND.W (0b01100)
+								case 8:
+									rs2 |= rval;
+									break; // AMOOR.W (0b01000)
+								case 16:
+									rs2 = ((i32)rs2 < (i32)rval) ? rs2 : rval;
+									break; // AMOMIN.W (0b10000)
+								case 20:
+									rs2 = ((i32)rs2 > (i32)rval) ? rs2 : rval;
+									break; // AMOMAX.W (0b10100)
+								case 24:
+									rs2 = (rs2 < rval) ? rs2 : rval;
+									break; // AMOMINU.W (0b11000)
+								case 28:
+									rs2 = (rs2 > rval) ? rs2 : rval;
+									break; // AMOMAXU.W (0b11100)
+								default:
+									Trap(TrapCode::IllegalInstruction);
+									dowrite = 0;
+									break; // Not supported.
+							}
+							if(dowrite)
+								bus->PokeWord(rs1, rs2);
+							break;
+						}
+						default:
+							Trap(TrapCode::IllegalInstruction);
+					}
 				}
 
+				// If some operation caused a trap break out after executing the instruction
+				if(trapped)
+					break;
+
+				if(rdid) {
+					gpr[rdid] = rval;
+				}
+
+				pc += 4;
 			}
 		}
 
 		if(trapped) {
 			mcause = trapCode;
+
+			// If prefixed with 1 in MSB, it's an interrupt, not a trap.
 			if(trapCode & 0x80000000) {
 				mtval = 0;
-				// pc -= 4
+				pc += 4; // PC needs to point to where the PC will return to.
 			} else {
-
+				if(trapCode > 5 && trapCode <= 8)
+					mtval = rval;
+				else
+					mtval = pc;
 			}
+			mepc = pc; // TRICKY: The kernel advances mepc automatically.
+			// CSR( mstatus ) & 8 = MIE, & 0x80 = MPIE
+			//  On an interrupt, the system moves current MIE into MPIE
+			mstatus = (mstatus & 0x08) << 4 | ((extraflags)&3) << 11;
+			pc = (mtvec - 4);
+
+			// If trapping, always enter machine mode.
+			extraflags |= 3;
+
+			// Reset trap flags
+			trapped = false;
+			trapCode = 0;
+			pc += 4;
 		}
+
+		if(cyclel > cycle)
+			cycleh++;
+		cyclel = cycle;
+		pc = pc;
+		return 0;
 	}
 
 } // namespace riscv

native/projects/riscv/src/Devices/ClntDevice.cpp

@@ -4,7 +4,7 @@
 
 namespace riscv::devices {
 
-	constexpr static AddressT MSIP_ADDRESS = ClntDevice::BASE_ADDRESS,
+	constexpr static Address MSIP_ADDRESS = ClntDevice::BASE_ADDRESS,
 							  MATCHL_ADDRESS = ClntDevice::BASE_ADDRESS + 0x4000,
 							  MATCHH_ADDRESS = ClntDevice::BASE_ADDRESS + 0x4004,
 							  TIMERL_ADDRESS = ClntDevice::BASE_ADDRESS + 0xbff8,
@@ -28,7 +28,7 @@ namespace riscv::devices {
 		}
 	}
 
-	u32 ClntDevice::Peek(AddressT address) {
+	u32 ClntDevice::Peek(Address address) {
 		switch(address) {
 			case TIMERL_ADDRESS:
 				return timerCountLow;
@@ -47,7 +47,7 @@ namespace riscv::devices {
 		}
 	}
 
-	void ClntDevice::Poke(AddressT address, u32 value) {
+	void ClntDevice::Poke(Address address, u32 value) {
 		switch(address) {
 			case MATCHL_ADDRESS:
 				timerMatchLow = value;

native/projects/riscv/src/Devices/RamDevice.cpp

@@ -4,7 +4,7 @@
 
 namespace riscv::devices {
 
-	RamDevice::RamDevice(AddressT base, AddressT size) : memoryBase(base), memorySize(size) {
+	RamDevice::RamDevice(Address base, Address size) : memoryBase(base), memorySize(size) {
 		memory = new u8[size];
 		LUCORE_CHECK(memory, "Could not allocate buffer for memory device with size 0x{:08x}.",
 					 size);
@@ -14,35 +14,35 @@ namespace riscv::devices {
 		delete[] memory;
 	}
 
-	AddressT RamDevice::Base() const {
+	Address RamDevice::Base() const {
 		return memoryBase;
 	}
 
-	AddressT RamDevice::Size() const {
+	Address RamDevice::Size() const {
 		return memorySize;
 	}
 
-	u8 RamDevice::PeekByte(AddressT address) {
+	u8 RamDevice::PeekByte(Address address) {
 		return memory[AddressToIndex<u8>(address)];
 	}
 
-	u16 RamDevice::PeekShort(AddressT address) {
+	u16 RamDevice::PeekShort(Address address) {
 		return std::bit_cast<u16*>(memory)[AddressToIndex<u16>(address)];
 	}
 
-	u32 RamDevice::PeekWord(AddressT address) {
+	u32 RamDevice::PeekWord(Address address) {
 		return std::bit_cast<u32*>(memory)[AddressToIndex<u32>(address)];
 	}
 
-	void RamDevice::PokeByte(AddressT address, u8 value) {
+	void RamDevice::PokeByte(Address address, u8 value) {
 		memory[AddressToIndex<u8>(address)] = value;
 	}
 
-	void RamDevice::PokeShort(AddressT address, u16 value) {
+	void RamDevice::PokeShort(Address address, u16 value) {
 		std::bit_cast<u16*>(memory)[AddressToIndex<u16>(address)] = value;
 	}
 
-	void RamDevice::PokeWord(AddressT address, u32 value) {
+	void RamDevice::PokeWord(Address address, u32 value) {
 		std::bit_cast<u32*>(memory)[AddressToIndex<u32>(address)] = value;
 	}
 

native/projects/riscv/src/Devices/SysconDevice.cpp

@@ -1,21 +1,22 @@
+#include <lucore/Logger.hpp>
 #include <riscv/Devices/SysconDevice.hpp>
 #include <riscv/System.hpp>
 
-#include <lucore/Logger.hpp>
+// TODO: This device is largely a stub. It needs to be implemented!
 
 namespace riscv::devices {
 
 	SysconDevice::SysconDevice(System* system) : system(system) {
 	}
 
-	u32 SysconDevice::Peek(AddressT address) {
+	u32 SysconDevice::Peek(Address address) {
-
 		lucore::LogInfo("SYSCON({}) Peek @ 0x{:08x}", static_cast<void*>(this), address);
 		return -1;
 	}
 
-	void SysconDevice::Poke(AddressT address, u32 value) {
+	void SysconDevice::Poke(Address address, u32 value) {
-		lucore::LogInfo("SYSCON({}) Poke @ 0x{:08x}: 0x{:08x}", static_cast<void*>(this), address, value);
+		lucore::LogInfo("SYSCON({}) Poke @ 0x{:08x}: 0x{:08x}", static_cast<void*>(this), address,
+						value);
 		/*
 			if(address == BASE_ADDRESS) {
 				if(value == 0x5555)

native/projects/riscv_test_harness/main.cpp

@@ -1,19 +1,16 @@
-#include <riscv/Bus.hpp>
+//! A test harness for testing the riscv library.
-#include <riscv/CPU.hpp>
+#include <riscv/System.hpp>
-#include <riscv/Devices/RamDevice.hpp>
-
-#include "riscv/Types.hpp"
 
 /// simple 16550 UART implementation
 struct SimpleUartDevice : public riscv::Bus::MmioDevice {
-	constexpr static riscv::AddressT BASE_ADDRESS = 0x10000000;
+	constexpr static riscv::Address BASE_ADDRESS = 0x10000000;
 
-	riscv::AddressT Base() const override { return BASE_ADDRESS; }
+	riscv::Address Base() const override { return BASE_ADDRESS; }
 
-	riscv::AddressT Size() const override { return 5; }
+	riscv::Address Size() const override { return 5; }
 
 	// TODO: emulate properly
-	u32 Peek(riscv::AddressT address) override {
+	u32 Peek(riscv::Address address) override {
 		switch(address) {
 			case BASE_ADDRESS:
 				break;
@@ -24,7 +21,7 @@ struct SimpleUartDevice : public riscv::Bus::MmioDevice {
 		return 0;
 	}
 
-	void Poke(riscv::AddressT address, u32 value) override {
+	void Poke(riscv::Address address, u32 value) override {
 		if(address == BASE_ADDRESS) { // write to data buffer
 			printf("%c\n", value);
 		}
@@ -32,5 +29,7 @@ struct SimpleUartDevice : public riscv::Bus::MmioDevice {
 };
 
 int main() {
+	auto system = riscv::System::WithMemory(128 * 1024);
+	system->AddDeviceToBus(new SimpleUartDevice);
 	return 0;
 }