Add current working directory to FDs

Author: fwsGonzo

lib/tinykvm/linux/fds.hpp

@@ -214,6 +214,20 @@ namespace tinykvm
 		/// @return True if the socket address is allowed, false otherwise.
 		bool validate_socket_address(const int socket_fd, struct sockaddr_storage& socket_address) const noexcept;
 
+		/// @brief Set the current working directory. This is used in a few system
+		/// calls, such as getcwd() and chdir().
+		/// @param path The path to set as the current working directory.
+		void set_current_working_directory(const std::string& path) noexcept {
+			m_current_working_directory = path;
+		}
+
+		/// @brief Get the current working directory. This is used in a few system
+		/// calls, such as getcwd() and chdir().
+		/// @return The current working directory.
+		const std::string& current_working_directory() const noexcept {
+			return m_current_working_directory;
+		}
+
 		/// @brief Set verbose mode. This will print out information about
 		/// file descriptor management.
 		/// @param verbose True to enable verbose mode, false to disable it.
@@ -238,6 +252,7 @@ namespace tinykvm
 		int m_next_file_fd = 0x1000;
 		int m_next_socket_fd = 0x1000 | SOCKET_BIT;
 		std::array<int, 3> m_stdout_redirects { 0, 1, 2 };
+		std::string m_current_working_directory;
 		bool m_verbose = false;
 		open_readable_t m_open_readable;
 		open_writable_t m_open_writable;

lib/tinykvm/linux/system_calls.cpp

@@ -1334,14 +1334,20 @@ void Machine::setup_linux_system_calls()
 	Machine::install_syscall_handler(
 		SYS_getcwd, [](vCPU& cpu) { // GETCWD
 			auto& regs = cpu.registers();
+			const uint64_t g_buf = regs.rdi;
+			const size_t buflen = regs.rsi;
 
-			const char fakepath[] = "/";
-			if (sizeof(fakepath) <= regs.rsi) {
-				cpu.machine().copy_to_guest(regs.rdi, fakepath, sizeof(fakepath));
-				regs.rax = regs.rdi;
+			const std::string& cwd = cpu.machine().fds().current_working_directory();
+			if (cwd.size()+1 <= buflen) {
+				// Copy the current working directory to the guest, including
+				// the null terminator.
+				cpu.machine().copy_to_guest(g_buf, cwd.c_str(), cwd.size()+1);
+				regs.rax = g_buf;
 			} else {
 				regs.rax = 0;
 			}
+			SYSPRINT("getcwd(buf=0x%lX (%s), buflen=%zu) = %lld\n",
+					 g_buf, cwd.c_str(), buflen, regs.rax);
 			cpu.set_registers(regs);
 		});
 	Machine::install_syscall_handler(