Implement reporting current file path to GDB

README.md

@@ -55,7 +55,6 @@ The program would load, and stop at first instruction. It will then prompt you t
 Then run `riscv32-none-elf-gdb`, and in the gdb prompt, type:
 
 ```
-file ../example/example
 target remote :1234
 ```
 

src/debug.cpp

@@ -196,7 +196,24 @@ void GDBStub::handle_packet(const std::string &packet) {
 
     case 'q':
       if (packet.find("qSupported") == 0) {
-        send_packet("PacketSize=4096");  // Example capability
+        send_packet("PacketSize=4096;qXfer:exec-file:read+");
+      } else if (packet.find("qXfer:exec-file:read:") == 0) {
+        size_t start = packet.find("::") + 2;
+        size_t end = packet.find(",", start);
+        size_t offset =
+            std::stoul(packet.substr(start, end - start), nullptr, 16);
+        size_t length = std::stoul(packet.substr(end + 1), nullptr, 16);
+
+        std::string exec_file_path = vm.get_file_path();
+
+        std::string response;
+        if (offset < exec_file_path.size()) {
+          size_t read_length = std::min(length, exec_file_path.size() - offset);
+          response = "m" + exec_file_path.substr(offset, read_length);
+        } else {
+          response = "l";  // No more data
+        }
+        send_packet(response);
       } else {
         send_packet("");  // Empty response
       }

src/rve.cpp

@@ -1,6 +1,7 @@
 #include <cassert>
 #include <cstdlib>
 #include <cstring>
+#include <filesystem>
 #include <fstream>
 #include <iostream>
 
@@ -18,7 +19,7 @@ int main(int argc, char *argv[]) {
     if (std::string(argv[i]) == "--debug")
       debug = true;
     else
-      program_filename = argv[i];
+      program_filename = std::filesystem::absolute(argv[i]);
   }
   if (program_filename == "") {
     std::cerr << "Expected filename of program to execute" << std::endl;
@@ -35,7 +36,7 @@ int main(int argc, char *argv[]) {
 
   memory.resize(MEMORY_SIZE, 0);
 
-  VM vm(memory);
+  VM vm(memory, program_filename);
 
   if (!debug) {
     try {

src/vm.cpp

@@ -12,7 +12,8 @@ inline int32_t sign_extend(int32_t value, int bits) {
   return (value ^ mask) - mask;
 }
 
-VM::VM(std::vector<uint8_t> memory) : memory_(memory) {}
+VM::VM(const std::vector<uint8_t>& memory, const std::string& file_path)
+    : memory_(memory), file_path(file_path) {}
 
 std::vector<uint8_t> VM::read_memory(size_t start, size_t size) {
   if (start + size > memory_.size()) {
@@ -38,6 +39,8 @@ uint32_t VM::read_register(size_t regnum) {
   return registers[regnum];
 }
 
+const std::string& VM::get_file_path() { return file_path; }
+
 void VM::step() {
   size_t memory_size = memory_.size();
   uint8_t* memory = &memory_[0];

src/vm.hpp

@@ -11,7 +11,7 @@ const int NUM_REGISTERS = 32;  // Standard RISC-V has 32 registers
 
 class VM {
  public:
-  VM(std::vector<uint8_t> memory);
+  VM(const std::vector<uint8_t> &memory, const std::string &file_path);
 
   void step();
   void eval();
@@ -22,9 +22,12 @@ class VM {
 
   uint32_t read_register(size_t regnum);
 
+  const std::string &get_file_path();
+
  private:
   std::vector<uint8_t> memory_;
 
   uint32_t registers[NUM_REGISTERS] = {0};
   uint32_t pc = 0;
+  std::string file_path;
 };