Use Machine cwd for readlinkat /proc/self/exe, fix getcwd return value

fwsGonzo · Jun 28, 2024 · b65ac4d · b65ac4d
1 parent fa9f605
commit b65ac4d
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Showing 2 changed files with 15 additions and 16 deletions.
diff --git a/emulator/src/main.cpp b/emulator/src/main.cpp
@@ -165,9 +165,9 @@ static void run_program(
 		machine.fds().permit_filesystem = !cli_args.sandbox;
 		machine.fds().permit_sockets    = !cli_args.sandbox;
 		// Rewrite certain links to masquerade and simplify some interactions (eg. /proc/self/exe)
-		machine.fds().filter_readlink = [=] (void* user, std::string& path) {
+		machine.fds().filter_readlink = [&] (void* user, std::string& path) {
 			if (path == "/proc/self/exe") {
-				path = "/program";
+				path = machine.fds().cwd + "/program";
 				return true;
 			}
 			fprintf(stderr, "Guest wanted to readlink: %s (denied)\n", path.c_str());
@@ -189,11 +189,6 @@ static void run_program(
 				path = args.at(0); // Sneakily open the real program instead
 				return true;
 			}
-			if (path == "/home"
-				|| path == "lib"
-				|| path == "lib/zig"
-				|| path == "std/std.zig"
-			) return true;
 			if (path == "/etc/ssl/certs/ca-certificates.crt")
 				return true;
 			// ld-linux

diff --git a/lib/libriscv/linux/system_calls.cpp b/lib/libriscv/linux/system_calls.cpp
@@ -337,6 +337,8 @@ static void syscall_openat(Machine<W>& machine)
 			// filter_open() can modify the path
 			if (!machine.fds().filter_open(machine.template get_userdata<void>(), path)) {
 				machine.set_result(-EPERM);
+				SYSPRINT("SYSCALL openat(path: %s) => %d\n",
+					path.c_str(), machine.template return_value<int>());
 				return;
 			}
 		}
@@ -493,15 +495,17 @@ void syscall_readlinkat(Machine<W>& machine)
 			SYSPRINT("SYSCALL readlinkat, fd: %d path: %s (filter => %s) buffer: 0x%lX size: %zu >= %ld\n",
 					 vfd, original_path.c_str(), path.c_str(), (long)g_buf, (size_t)bufsize, (long)machine.return_value());
 		}
-		const int real_fd = machine.fds().translate(vfd);
+		else
+		{
+			const int real_fd = machine.fds().translate(vfd);
 
-		const int res = readlinkat(real_fd, original_path.c_str(), buffer, bufsize);
-		if (res > 0) {
-			// TODO: Only necessary if g_buf is not sequential.
-			machine.copy_to_guest(g_buf, buffer, res);
+			const int res = readlinkat(real_fd, original_path.c_str(), buffer, bufsize);
+			if (res > 0) {
+				// TODO: Only necessary if g_buf is not sequential.
+				machine.copy_to_guest(g_buf, buffer, res);
+			}
+			machine.set_result_or_error(res);
 		}
-
-		machine.set_result_or_error(res);
 	} else {
 		machine.set_result(-ENOSYS);
 	}
@@ -556,12 +560,12 @@ template <int W>
 static void syscall_getcwd(Machine<W>& machine)
 {
 	const auto g_buf = machine.sysarg(0);
-	const auto size = machine.sysarg(1);
+	[[maybe_unused]] const auto size = machine.sysarg(1);
 
 	auto& cwd = machine.fds().cwd;
 	if (!cwd.empty()) {
 		machine.copy_to_guest(g_buf, cwd.c_str(), cwd.size()+1);
-		machine.set_result(0);
+		machine.set_result(cwd.size()+1);
 	} else {
 		machine.set_result(-1);
 	}