implement ptrace monitoring loop for watchpoint events

src/tracer.cpp

@@ -53,3 +53,65 @@ void Tracer::handle_watchpoint_hit(pid_t pid, uint64_t address) {
   std::cout << std::format("Variable accessed at RIP: 0x{:x}", regs.rip)
             << std::endl;
 }
+
+void Tracer::watch_variable(const std::string &exec_path, uint64_t address, size_t size) {
+  pid_t pid = fork();
+
+  if (pid == 0) {
+    // Child process: execute the target binary
+    ptrace(PTRACE_TRACEME, 0, 0, 0);
+    execl(exec_path.c_str(), exec_path.c_str(), nullptr);
+    std::cerr << "Error: Failed to execute " << exec_path << std::endl;
+    exit(1);
+  } else if (pid > 0) {
+    // Parent process: set up watchpoint and monitor
+    int status;
+    waitpid(pid, &status, 0);
+
+    if (!WIFSTOPPED(status)) {
+      std::cerr << "Error: Child process not stopped" << std::endl;
+      return;
+    }
+
+    // Set up hardware watchpoint
+    setup_hardware_watchpoint(pid, address, size);
+
+    // Continue execution and monitor for watchpoint hits
+    ptrace(PTRACE_CONT, pid, 0, 0);
+
+    while (true) {
+      waitpid(pid, &status, 0);
+
+      if (WIFEXITED(status)) {
+        std::cout << "Process exited with status " << WEXITSTATUS(status)
+                  << std::endl;
+        break;
+      }
+
+      if (WIFSTOPPED(status)) {
+        int sig = WSTOPSIG(status);
+
+        if (sig == SIGTRAP) {
+          // Check if it's a watchpoint hit
+          uint64_t dr6 = ptrace(PTRACE_PEEKUSER, pid,
+                               offsetof(struct user, u_debugreg[6]), 0);
+
+          if (dr6 & 0x1) {  // DR0 triggered
+            handle_watchpoint_hit(pid, address);
+
+            // Clear DR6
+            ptrace(PTRACE_POKEUSER, pid,
+                   offsetof(struct user, u_debugreg[6]), 0);
+          }
+
+          ptrace(PTRACE_CONT, pid, 0, 0);
+        } else {
+          // Forward other signals
+          ptrace(PTRACE_CONT, pid, 0, sig);
+        }
+      }
+    }
+  } else {
+    std::cerr << "Error: fork() failed" << std::endl;
+  }
+}