Improve vmem handling a bit

example/example.c

@@ -1,5 +1,21 @@
 #include "printf.h"
 
+typedef unsigned long long uint64_t;
+typedef unsigned long uint32_t;
+#define MTIME_BASE 0x0200BFF8
+
+uint64_t read_mtime_atomic() {
+  uint32_t upper1, lower, upper2;
+
+  do {
+    upper1 = *(uint32_t*)(MTIME_BASE + 4);
+    lower = *(uint32_t*)(MTIME_BASE);
+    upper2 = *(uint32_t*)(MTIME_BASE + 4);
+  } while (upper1 != upper2); // Repeat if upper changed during the process
+
+  return ((uint64_t)upper1 << 32) | lower;
+}
+
 int fact(int n) {
   if (n == 0)
     return 1;
@@ -11,6 +27,7 @@ int main() {
   int n = 8;
   int res = fact(8);
 
+  printf("sizeof(long) = %d\n", sizeof(long long));
   printf("%d! = %d\n", n, res);
 
   return 0;

src/debug.cpp

@@ -228,9 +228,11 @@ void GDBStub::handle_packet(const std::string &packet) {
             std::stoul(packet.substr(3, packet.find(',', 3)), nullptr, 16);
 
         if (breakpoints.count(addr) == 0) {
-          uint32_t original_instr = vm.read_memory_word(addr);
+          uint32_t original_instr;
+          vm.read_mem((uint8_t *)&original_instr, addr, 4);
           breakpoints[addr] = original_instr;
-          vm.write_memory_word(addr, 0x00100073);  // 0x00100073 is EBREAK
+          uint32_t debug_instr = 0x00100073;  // 0x00100073 is EBREAK
+          vm.write_mem((uint8_t *)&debug_instr, addr, 4);
         }
       }
       send_packet("OK");
@@ -244,7 +246,7 @@ void GDBStub::handle_packet(const std::string &packet) {
 
         if (breakpoints.count(addr) > 0) {
           // Restore the original instruction
-          vm.write_memory_word(addr, breakpoints[addr]);
+          vm.write_mem((uint8_t *)&breakpoints[addr], addr, 4);
           breakpoints.erase(addr);
         }
       }

src/vm.cpp

@@ -12,26 +12,8 @@ inline int32_t sign_extend(int32_t value, int bits) {
   return (value ^ mask) - mask;
 }
 
-uint8_t UART::read_register(uint32_t address) {
-  switch (address) {
-    case UART_LSR:
-      // Always ready to transmit
-      return LSR_TRANSMITTER_EMPTY;
-    default:
-      return 0;
-  }
-}
-
-void UART::write_register(uint32_t address, uint8_t value) {
-  switch (address) {
-    case UART_THR:
-      std::cout.put(static_cast<char>(value));
-      break;
-  }
-}
-
 bool UART::is_transmitter_ready() {
-  return read_register(UART_LSR) & LSR_TRANSMITTER_EMPTY;
+  return registers[UART_LSR] & LSR_TRANSMITTER_EMPTY;
 }
 
 VM::VM(const std::vector<uint8_t>& memory, const std::string& file_path)
@@ -45,96 +27,84 @@ void VM::setreg(int regnum, uint32_t value) {
   registers[regnum] = value;
 }
 
+void UART::read_mem(uint8_t* dst, size_t addr, size_t size) {
+  if (addr < UART_ADDR || addr + size > UART_ADDR + 8) {
+    throw std::runtime_error("Memory access out of bounds");
+  }
+  addr -= UART_ADDR;
+  for (size_t i = 0; i < size; i++) {
+    switch (addr + i) {
+      case UART_LSR:
+        // Always ready to transmit
+        dst[i] = LSR_TRANSMITTER_EMPTY;
+      default:
+        dst[i] = 0;
+    }
+  }
+}
+
+void UART::write_mem(uint8_t* src, size_t addr, size_t size) {
+  if (addr < UART_ADDR || addr + size > UART_ADDR + 8) {
+    throw std::runtime_error("Memory access out of bounds");
+  }
+  addr -= UART_ADDR;
+  for (size_t i = 0; i < size; i++) {
+    switch (addr + i) {
+      case UART_THR:
+        std::cout.put(static_cast<char>(*src));
+        break;
+    }
+  }
+}
+
+void VM::read_mem(uint8_t* dst, size_t addr, size_t size) {
+  if (addr >= PROGRAM_ADDR) {
+    addr -= PROGRAM_ADDR;
+    if (addr + size > memory_.size()) {
+      throw std::runtime_error("Memory access out of bounds");
+    }
+    std::memcpy(dst, &memory_[addr], size);
+  }
+}
+
+void VM::write_mem(uint8_t* src, size_t addr, size_t size) {
+  if (addr >= PROGRAM_ADDR) {
+    addr -= PROGRAM_ADDR;
+    if (addr + size > memory_.size()) {
+      throw std::runtime_error("Memory access out of bounds");
+    }
+    std::memcpy(&memory_[addr], src, size);
+    return;
+  }
+
+  if (is_mmap(addr, size)) {
+    if (addr >= UART_ADDR && addr < UART_ADDR + 8) {
+      uart.write_mem(src, addr, size);
+    }
+    return;
+  }
+}
+
 std::vector<uint8_t> VM::read_memory(size_t start, size_t size) {
-  if (start >= PROGRAM_ADDR) {
+  std::vector<uint8_t> res(size, 0);
-    start -= PROGRAM_ADDR;
-    if (start + size > memory_.size()) {
-      return std::vector<uint8_t>(size, 0);
-    }
-    return std::vector<uint8_t>(memory_.begin() + start,
-                                memory_.begin() + start + size);
-  } else {
-    return std::vector<uint8_t>(size, 0);
-  }
-}
 
-uint32_t VM::read_memory_word(size_t pos) {
+  size_t i = start;
-  if (pos >= PROGRAM_ADDR) {
+  size_t end = start + size;
-    pos -= PROGRAM_ADDR;
-    if (pos + 3 >= memory_.size()) {
-      throw std::runtime_error("Memory access out of bounds");
-    }
-    return *(uint32_t*)&memory_[pos];
-  } else {
-    throw std::runtime_error("Memory access out of bounds");
-  }
-}
 
-uint16_t VM::read_memory_half_word(size_t pos) {
+  while (i < end) {
-  if (pos >= PROGRAM_ADDR) {
+    if (i % 4 == 0 && end - i >= 4) {
-    pos -= PROGRAM_ADDR;
+      read_mem(&res[i - start], i, 4);
-    if (pos + 1 >= memory_.size()) {
+      i += 4;
-      throw std::runtime_error("Memory access out of bounds");
+    } else if (i % 2 == 0 && end - i >= 2) {
-    }
+      read_mem(&res[i - start], i, 2);
-
+      i += 2;
-    return *(uint16_t*)&memory_[pos];
+    } else {
-  } else {
+      read_mem(&res[i - start], i, 1);
-    throw std::runtime_error("Memory access out of bounds");
+      i += 1;
-  }
-}
-
-uint8_t VM::read_memory_byte(size_t pos) {
-  if (pos >= PROGRAM_ADDR) {
-    pos -= PROGRAM_ADDR;
-    if (pos >= memory_.size()) {
-      throw std::runtime_error("Memory access out of bounds");
-    }
-
-    return memory_[pos];
-  } else {
-    throw std::runtime_error("Memory access out of bounds");
-  }
-}
-
-void VM::write_memory_word(size_t pos, uint32_t value) {
-  if (pos >= PROGRAM_ADDR) {
-    pos -= PROGRAM_ADDR;
-    if (pos + 1 >= memory_.size()) {
-      throw std::runtime_error("Memory access out of bounds");
-    }
-    *(uint32_t*)&memory_[pos] = value;
-  } else {
-    throw std::runtime_error("Memory access out of bounds");
-  }
-}
-
-void VM::write_memory_half_word(size_t pos, uint16_t value) {
-  if (pos >= PROGRAM_ADDR) {
-    pos -= PROGRAM_ADDR;
-    if (pos + 3 >= memory_.size()) {
-      throw std::runtime_error("Memory access out of bounds");
-    }
-    *(uint16_t*)&memory_[pos] = value;
-  } else {
-    throw std::runtime_error("Memory access out of bounds");
-  }
-}
-
-void VM::write_memory_byte(size_t pos, uint8_t value) {
-  if (pos >= PROGRAM_ADDR) {
-    pos -= PROGRAM_ADDR;
-    if (pos >= memory_.size()) {
-      throw std::runtime_error("Memory access out of bounds");
-    }
-    memory_[pos] = value;
-  } else {
-    if (is_mmap(pos, 1)) {
-      if (pos >= UART_ADDR && pos < UART_ADDR + 8) {
-        uart.write_register(pos - UART_ADDR, value);
-      }
-      return;
     }
   }
+
+  return res;
 }
 
 bool VM::is_mmap(size_t pos, size_t size) {
@@ -353,19 +323,29 @@ void VM::step() {
       imm = sign_extend(instr >> 20, 12);  // Extract 12-bit immediate
       if (funct3 == 0x00) {                // LB
         uint32_t addr = registers[rs1] + imm;
-        setreg(rd, sign_extend(read_memory_byte(addr), 8));
+        uint8_t val;
+        read_mem(&val, addr, 1);
+        setreg(rd, sign_extend(val, 8));
       } else if (funct3 == 0x01) {  // LH
         uint32_t addr = registers[rs1] + imm;
-        setreg(rd, sign_extend(read_memory_half_word(addr), 16));
+        uint16_t val;
+        read_mem((uint8_t*)&val, addr, 2);
+        setreg(rd, sign_extend(val, 16));
       } else if (funct3 == 0x2) {  // LW
         uint32_t addr = registers[rs1] + imm;
-        setreg(rd, read_memory_word(addr));
+        uint32_t val;
+        read_mem((uint8_t*)&val, addr, 4);
+        setreg(rd, val);
       } else if (funct3 == 0x4) {  // LBU
         uint32_t addr = registers[rs1] + imm;
-        setreg(rd, read_memory_byte(addr));
+        uint8_t val;
+        read_mem(&val, addr, 1);
+        setreg(rd, val);
       } else if (funct3 == 0x5) {  // LHU
         uint32_t addr = registers[rs1] + imm;
-        setreg(rd, read_memory_half_word(addr));
+        uint16_t val;
+        read_mem((uint8_t*)&val, addr, 2);
+        setreg(rd, val);
       } else {
         throw std::runtime_error("Unknown load instruction");
       }
@@ -376,13 +356,13 @@ void VM::step() {
       imm = sign_extend(imm, 12);  // Sign-extend 12-bit immediate
       if (funct3 == 0x0) {         // SB
         uint32_t addr = registers[rs1] + imm;
-        write_memory_byte(addr, registers[rs2]);
+        write_mem((uint8_t*)&registers[rs2], addr, 1);
       } else if (funct3 == 0x1) {  // SH
         uint32_t addr = registers[rs1] + imm;
-        write_memory_half_word(addr, registers[rs2]);
+        write_mem((uint8_t*)&registers[rs2], addr, 2);
       } else if (funct3 == 0x2) {  // SW
         uint32_t addr = registers[rs1] + imm;
-        write_memory_word(addr, registers[rs2]);
+        write_mem((uint8_t*)&registers[rs2], addr, 4);
       } else {
         throw std::runtime_error("Unknown store instruction");
       }

src/vm.hpp

@@ -2,6 +2,7 @@
 
 #include <cstddef>
 #include <cstdint>
+#include <stdexcept>
 #include <string>
 #include <vector>
 
@@ -13,11 +14,11 @@ const uint32_t PROGRAM_ADDR = 0x80000000;
 
 class UART {
  public:
-  uint8_t read_register(uint32_t address);
-  void write_register(uint32_t address, uint8_t value);
-
   bool is_transmitter_ready();
 
+  void write_mem(uint8_t *src, size_t addr, size_t size);
+  void read_mem(uint8_t *dst, size_t addr, size_t size);
+
  private:
   enum Registers {
     UART_RBR = 0x00,  // Receiver Buffer Register
@@ -40,13 +41,8 @@ class VM {
 
   std::vector<uint8_t> read_memory(size_t start, size_t size);
 
-  uint32_t read_memory_word(size_t pos);
+  void read_mem(uint8_t *dst, size_t addr, size_t size);
-  uint16_t read_memory_half_word(size_t pos);
+  void write_mem(uint8_t *src, size_t addr, size_t size);
-  uint8_t read_memory_byte(size_t pos);
-
-  void write_memory_word(size_t pos, uint32_t value);
-  void write_memory_half_word(size_t pos, uint16_t value);
-  void write_memory_byte(size_t pos, uint8_t value);
 
   bool is_mmap(size_t pos, size_t size);