1 files changed, 259 insertions, 0 deletions
diff --git a/website-emu/src/lib.rs b/website-emu/src/lib.rs
new file mode 100644
index 0000000..7c1a285
--- /dev/null
+++ b/website-emu/src/lib.rs
@@ -0,0 +1,259 @@
+mod core;
+mod mem;
+mod state;
+
+use wasm_bindgen::prelude::wasm_bindgen;
+use crate::core::*;
+use crate::mem::*;
+use crate::state::CpuState;
+
+const REGISTER_NAME_WIDTH: u32 = 0b11111;
+
+const DRAM_LOAD: u32 = 0x20000000;
+const OS_LOAD: u32 = 0x80000000;
+const INITRD_LOAD: u32 = 0;
+
+#[wasm_bindgen]
+pub fn boot(image: &[u8], initrd: &[u8], memory: &[u8]) {
+    let mut cpu_memory = CpuMemory {
+        devices: Vec::new(),
+    };
+
+    let memory_len = memory.len();
+    let os_size = image.len();
+    let initrd_size = initrd.len();
+
+    let ram_device = LogicalMemory {
+        base: DRAM_LOAD,
+        size: memory_len as u32,
+        dram: memory.to_vec().into_boxed_slice(),
+    };
+
+    let os_image = LogicalMemory {
+        base: OS_LOAD,
+        size: os_size as u32,
+        dram: image.to_vec().into_boxed_slice(),
+    };
+
+    let initrd_image = LogicalMemory {
+        base: INITRD_LOAD,
+        size: initrd_size as u32,
+        dram: initrd.to_vec().into_boxed_slice(),
+    };
+
+    cpu_memory.register_device(
+        DRAM_LOAD..DRAM_LOAD + memory_len as u32,
+        Box::new(ram_device)
+    );
+
+    let mut state = CpuState::new(cpu_memory);
+
+    state.pc = 0x80000000;
+    state.registers[10] = 0;
+    state.registers[2] = DRAM_LOAD + memory_len as u32;
+
+    loop {
+        {
+            handle_instruction(&mut state);
+            state.registers[0] = 0;
+        }
+    }
+}
+
+fn handle_instruction(state: &mut CpuState) {
+    let pc = state.pc;
+    let word = state.memory.read_instruction(pc).expect(format!("pc {:x} does not map to valid memory", pc).as_str());
+    let opcode = word & 0x7f;
+    match opcode {
+        0b0110011 => {
+            let f7 = word >> 25;
+            let f3 = (word >> 12) & 0b111;
+
+            let rs2 = ((word >> 20) & REGISTER_NAME_WIDTH) as usize;
+            let rs1 = ((word >> 15) & REGISTER_NAME_WIDTH) as usize;
+            let rd = ((word >> 7) & REGISTER_NAME_WIDTH) as usize;
+
+            match (f7 << 3) | f3 {
+                0 => add(state, rd, rs1, rs2),
+                256 => sub(state, rd, rs1, rs2),
+                4 => xor(state, rd, rs1, rs2),
+                6 => or(state, rd, rs1, rs2),
+                7 => and(state, rd, rs1, rs2),
+                1 => sll(state, rd, rs1, rs2),
+                5 => srl(state, rd, rs1, rs2),
+                261 => sra(state, rd, rs1, rs2),
+                2 => slt(state, rd, rs1, rs2),
+                3 => sltu(state, rd, rs1, rs2),
+                8 => mul(state, rd, rs1, rs2),
+                9 => mulh(state, rd, rs1, rs2),
+                10 => mulhsu(state, rd, rs1, rs2),
+                11 => mulhu(state, rd, rs1, rs2),
+                12 => div(state, rd, rs1, rs2),
+                13 => divu(state, rd, rs1, rs2),
+                14 => rem(state, rd, rs1, rs2),
+                15 => remu(state, rd, rs1, rs2),
+                _ => panic!("Illegal instruction: {:x}", word),
+            }
+        }
+        0b0010011 => {
+            let imm = ((word as i32) >> 20) as u32;
+            let f3 = (word >> 12) & 0b111;
+
+            let rs1 = ((word >> 15) & 0b11111) as usize;
+            let rd = ((word >> 7) & 0b11111) as usize;
+
+            match f3 {
+                0 => addi(state, rd, rs1, imm),
+                4 => xori(state, rd, rs1, imm),
+                6 => ori(state, rd, rs1, imm),
+                7 => andi(state, rd, rs1, imm),
+                1 => {
+                    if (imm >> 5) != 0 {
+                        panic!("Illegal instruction: {:x}", word);
+                    }
+                    slli(state, rd, rs1, imm);
+                }
+                5 => {
+                    if (imm >> 5) != 0 {
+                        panic!("Illegal instruction: {:x}", word);
+                    }
+                    if (imm >> 5) & 0b1111111 == 0 {
+                        srli(state, rd, rs1, imm);
+                    } else {
+                        srai(state, rd, rs1, imm);
+                    }
+                }
+                2 => slti(state, rd, rs1, imm),
+                3 => sltiu(state, rd, rs1, imm),
+                _ => panic!("Illegal instruction: {:x}", word),
+            }
+        }
+        0b0000011 => {
+            let imm = ((word as i32) >> 20) as u32;
+            let f3 = (word >> 12) & 0b111;
+
+            let rs1 = ((word >> 15) & 0b11111) as usize;
+            let rd = ((word >> 7) & 0b11111) as usize;
+
+            match f3 {
+                0 => lb(state, rd, rs1, imm),
+                1 => lh(state, rd, rs1, imm),
+                2 => lw(state, rd, rs1, imm),
+                4 => lbu(state, rd, rs1, imm),
+                5 => lhu(state, rd, rs1, imm),
+                _ => panic!("Illegal instruction: {:x}", word),
+            }
+        }
+        0b0100011 => {
+            let imm_low = (word >> 7) & 0b11111;
+            let imm_high = (word >> 25) & 0b1111111;
+            let f3 = (word >> 12) & 0b111;
+            let rs1 = ((word >> 15) & REGISTER_NAME_WIDTH) as usize;
+            let rs2 = ((word >> 20) & REGISTER_NAME_WIDTH) as usize;
+
+            let imm = ((((imm_high << 5) | imm_low) as i32) << 20 >> 20) as u32;
+
+            match f3 {
+                0 => sb(state, rs1, rs2, imm),
+                1 => sh(state, rs1, rs2, imm),
+                2 => sw(state, rs1, rs2, imm),
+                _ => panic!("Illegal instruction: {:x}", word),
+            };
+        }
+        0b1100011 => {
+            let f3 = (word >> 12) & 0b111;
+            let rs1 = ((word >> 15) & REGISTER_NAME_WIDTH) as usize;
+            let rs2 = ((word >> 20) & REGISTER_NAME_WIDTH) as usize;
+
+            let imm = (((word >> 31) & 0x1) << 12)
+                | (((word >> 7) & 0x1) << 11)
+                | (((word >> 25) & 0x3f) << 5)
+                | (((word >> 8) & 0xf) << 1);
+
+            let imm = ((imm as i32) << 19 >> 19) as u32;
+
+            match f3 {
+                0 => beq(state, rs1, rs2, imm),
+                1 => bne(state, rs1, rs2, imm),
+                4 => blt(state, rs1, rs2, imm),
+                5 => bge(state, rs1, rs2, imm),
+                6 => bltu(state, rs1, rs2, imm),
+                7 => bgeu(state, rs1, rs2, imm),
+                _ => panic!("Illegal instruction: {:x}", word),
+            }
+            return;
+        }
+        0b1101111 => {
+            let rd = (word >> 7) & REGISTER_NAME_WIDTH;
+            let imm = (((word >> 31) & 0x1) << 20)
+                | (((word >> 12) & 0xFF) << 12)
+                | (((word >> 20) & 0x1) << 11)
+                | (((word >> 21) & 0x3FF) << 1);
+            let imm = ((imm as i32) << 11 >> 11) as u32;
+            jal(state, rd as usize, imm);
+            return;
+        }
+        0b1100111 => {
+            let rs1 = (word >> 15) & REGISTER_NAME_WIDTH;
+            let rd = (word >> 7) & REGISTER_NAME_WIDTH;
+            let imm = word >> 20;
+
+            let sentinel = (word >> 12) & 0b111;
+            if sentinel != 0 {
+                panic!("Illegal instruction: {:x}", word);
+            }
+
+            jalr(state, rd as usize, rs1 as usize, imm);
+            return;
+        }
+        0b0110111 => {
+            let imm = word >> 12;
+            let rd = ((word >> 7) & 0b11111) as usize;
+            lui(state, rd, imm);
+        }
+        0b0010111 => {
+            let imm = word >> 12;
+            let rd = (word >> 7) & REGISTER_NAME_WIDTH;
+            auipc(state, rd as usize, imm);
+        }
+        0b1110011 => {
+            let imm = word >> 20;
+            let rd = ((word >> 7) & REGISTER_NAME_WIDTH) as usize;
+            let rs1 = ((word >> 15) & REGISTER_NAME_WIDTH) as usize;
+            let f3 = (word >> 12) & 0b111;
+
+            match f3 {
+                0 => {
+                    match imm {
+                        0 => trap_to_kernel(state),        // ecall
+                        258 => return_to_userspace(state), // sret
+                        261 => {
+                            println!("wfi");
+                        }
+                        _ => panic!("Illegal instruction: {:x}", word),
+                    }
+                } // ecall
+                1 => csrrw(state, rd, rs1, imm as usize),
+                2 => csrrs(state, rd, rs1, imm as usize),
+                3 => csrrc(state, rd, rs1, imm as usize),
+                5 => csrrwi(state, rd, rs1 as u32, imm as usize),
+                6 => csrrsi(state, rd, rs1 as u32, imm as usize),
+                7 => csrrci(state, rd, rs1 as u32, imm as usize),
+
+                _ => panic!("Illegal instruction: {:x}", word),
+            }
+        } // ecall (ebreak not implemented)
+        _ => panic!("Illegal instruction or todo: {:032b}", word),
+    }
+
+    state.pc += 4;
+}
+
+fn trap_to_kernel(state: &mut CpuState) {
+    state.csr[0x341 /* mepc */] = state.pc;
+    state.pc = state.csr[0x305 /* mtvec */];
+}
+
+fn return_to_userspace(state: &mut CpuState) {
+    state.pc = state.csr[0x341 /* mepc */] + 4;
+}