test(fs): refactor write_to_fd, make guest path name optional

- write_to_fd test is now part of fs_tests
- standard streams' (written to by write_to_fd) output is checked
- generate_params now takes Option<PathBuf> as guest_path, as such a
  path may not always be necessary (like in the case of write_to_fd).
  A superfluous guest_path was also removed from mounts_test.

Author: n0toose

tests/fs-test.rs

@@ -118,7 +118,7 @@ fn create_kernel_args<T: AsStr, U: AsStr>(test_name: T, file_path: U) -> Vec<Str
 fn generate_params(
 	filemap_params: Option<Vec<String>>,
 	test_name: &'static str,
-	guest_path: &PathBuf,
+	guest_path: Option<PathBuf>,
 ) -> Params {
 	Params {
 		cpu_count: 2.try_into().unwrap(),
@@ -129,7 +129,11 @@ fn generate_params(
 		file_mapping: filemap_params.unwrap_or_default(),
 		#[cfg(target_os = "linux")]
 		file_isolation: strict_sandbox(),
-		kernel_args: create_kernel_args(test_name, guest_path),
+		// A default value is chosen to make debugging investigations a bit easier.
+		kernel_args: create_kernel_args(
+			test_name,
+			&guest_path.unwrap_or(PathBuf::from("./no_guest_path_needed")),
+		),
 		..Default::default()
 	}
 }
@@ -153,7 +157,11 @@ fn create_mapped_parent_nonpresent_file() {
 
 	let uhyvefilemap_params = create_filemap_params(&host_dir_path, &guest_dir_path);
 
-	let params = generate_params(uhyvefilemap_params.into(), test_name, &guest_file_path);
+	let params = generate_params(
+		uhyvefilemap_params.into(),
+		test_name,
+		guest_file_path.into(),
+	);
 
 	let bin_path: PathBuf = build_hermit_bin("fs_tests", BuildMode::Debug);
 	let res = run_vm_in_thread(bin_path, params);
@@ -178,7 +186,11 @@ fn create_write_mapped_nonpresent_file() {
 
 	let uhyvefilemap_params = create_filemap_params(&host_file_path, &guest_file_path);
 
-	let params = generate_params(uhyvefilemap_params.into(), test_name, &guest_file_path);
+	let params = generate_params(
+		uhyvefilemap_params.into(),
+		test_name,
+		guest_file_path.into(),
+	);
 
 	let bin_path: PathBuf = build_hermit_bin("fs_tests", BuildMode::Debug);
 	let res = run_vm_in_thread(bin_path, params);
@@ -200,7 +212,7 @@ fn create_write_unmapped_nonpresent_file() {
 	let mut guest_file_path = guest_dir_path.clone();
 	guest_file_path.push(&filename);
 
-	let params = generate_params(None, testname, &guest_file_path);
+	let params = generate_params(None, testname, guest_file_path.into());
 
 	let bin_path: PathBuf = build_hermit_bin("fs_tests", BuildMode::Debug);
 	let res = run_vm_in_thread(bin_path, params);
@@ -230,7 +242,11 @@ fn remove_mapped_present_file() {
 
 	let uhyvefilemap_params = create_filemap_params(&host_file_path, &guest_file_path);
 
-	let params = generate_params(uhyvefilemap_params.into(), test_name, &guest_file_path);
+	let params = generate_params(
+		uhyvefilemap_params.into(),
+		test_name,
+		guest_file_path.into(),
+	);
 
 	assert!(host_file_path.exists());
 	let bin_path: PathBuf = build_hermit_bin("fs_tests", BuildMode::Debug);
@@ -263,7 +279,11 @@ fn remove_mapped_parent_present_file() {
 
 	let uhyvefilemap_params = create_filemap_params(&host_dir_path, &guest_dir_path);
 
-	let params = generate_params(uhyvefilemap_params.into(), test_name, &guest_file_path);
+	let params = generate_params(
+		uhyvefilemap_params.into(),
+		test_name,
+		guest_file_path.into(),
+	);
 
 	assert!(host_file_path.exists());
 	let bin_path: PathBuf = build_hermit_bin("fs_tests", BuildMode::Debug);
@@ -282,7 +302,7 @@ fn remove_nonpresent_file_test() {
 
 	let test_name: &'static str = "remove_nonpresent_file_test";
 	let guest_file_path = get_testname_derived_guest_path(test_name);
-	let params = generate_params(None, test_name, &guest_file_path);
+	let params = generate_params(None, test_name, guest_file_path.into());
 
 	let bin_path: PathBuf = build_hermit_bin("fs_tests", BuildMode::Debug);
 	let res = run_vm_in_thread(bin_path, params);
@@ -297,7 +317,7 @@ fn fd_open_remove_close() {
 
 	let test_name: &'static str = "fd_open_remove_close";
 	let (filemap, guest_file_path, _tmpdir) = create_filemap(test_name);
-	let params = generate_params(Some(filemap), test_name, &guest_file_path);
+	let params = generate_params(Some(filemap), test_name, guest_file_path.into());
 
 	let bin_path: PathBuf = build_hermit_bin("fs_tests", BuildMode::Debug);
 	let res = run_vm_in_thread(bin_path, params);
@@ -312,7 +332,7 @@ fn fd_open_remove_before_and_after_closing() {
 
 	let test_name: &'static str = "fd_open_remove_before_and_after_closing";
 	let guest_file_path = get_testname_derived_guest_path(test_name);
-	let params = generate_params(None, test_name, &guest_file_path);
+	let params = generate_params(None, test_name, guest_file_path.into());
 
 	let bin_path: PathBuf = build_hermit_bin("fs_tests", BuildMode::Debug);
 	let res = run_vm_in_thread(bin_path, params);
@@ -327,7 +347,7 @@ fn fd_remove_twice_before_closing() {
 
 	let test_name: &'static str = "fd_remove_twice_before_closing";
 	let guest_file_path = get_testname_derived_guest_path(test_name);
-	let params = generate_params(None, test_name, &guest_file_path);
+	let params = generate_params(None, test_name, guest_file_path.into());
 
 	let bin_path: PathBuf = build_hermit_bin("fs_tests", BuildMode::Debug);
 	let res = run_vm_in_thread(bin_path, params);
@@ -342,7 +362,7 @@ fn open_read_only_write() {
 
 	let test_name: &'static str = "open_read_only_write";
 	let (filemap, guest_file_path, _tmpdir) = create_filemap(test_name);
-	let params = generate_params(Some(filemap), test_name, &guest_file_path);
+	let params = generate_params(Some(filemap), test_name, guest_file_path.into());
 
 	let bin_path: PathBuf = build_hermit_bin("fs_tests", BuildMode::Debug);
 
@@ -364,20 +384,27 @@ fn open_read_only_write() {
 fn fd_write_to_fd() {
 	env_logger::try_init().ok();
 
-	let params = Params {
-		cpu_count: 2.try_into().unwrap(),
-		memory_size: Byte::from_u64_with_unit(32, Unit::MiB)
-			.unwrap()
-			.try_into()
-			.unwrap(),
-		#[cfg(target_os = "linux")]
-		file_isolation: strict_sandbox(),
-		..Default::default()
-	};
-
-	let bin_path: PathBuf = build_hermit_bin("write_to_fd", BuildMode::Debug);
+	let test_name: &'static str = "write_to_fd";
+	let mut params = generate_params(None, test_name, None);
+	// This is a one-time thing... for now. If this is used in more tests,
+	// a toggle should become part of generate_params.
+	params.output = uhyvelib::params::Output::Buffer;
+	let bin_path: PathBuf = build_hermit_bin("fs_tests", BuildMode::Debug);
 	let res = run_vm_in_thread(bin_path, params);
 	check_result(&res);
+	// The file descriptors are standard streams.
+	assert!(
+		res.output
+			.as_ref()
+			.unwrap()
+			.contains("Wrote to stdout manually!")
+	);
+	assert!(
+		res.output
+			.as_ref()
+			.unwrap()
+			.contains("Wrote to stderr manually!")
+	);
 }
 
 #[test]
@@ -414,8 +441,7 @@ fn mounts_test() {
 			(&host_dir_path).as_str(),
 		),
 	];
-	let guest_file_path = get_testname_derived_guest_path(test_name);
-	let params = generate_params(uhyvefilemap_params.into(), test_name, &guest_file_path);
+	let params = generate_params(uhyvefilemap_params.into(), test_name, None);
 
 	let bin_path: PathBuf = build_hermit_bin("fs_tests", BuildMode::Debug);
 	let res = run_vm_in_thread(bin_path, params);
@@ -428,7 +454,7 @@ fn lseek_test() {
 
 	let test_name: &'static str = "lseek_file";
 	let (filemap, guest_file_path, _tmpdir) = create_filemap(test_name);
-	let params = generate_params(Some(filemap), test_name, &guest_file_path);
+	let params = generate_params(Some(filemap), test_name, guest_file_path.into());
 
 	let bin_path: PathBuf = build_hermit_bin("fs_tests", BuildMode::Debug);
 	let res = run_vm_in_thread(bin_path, params);

tests/test-kernels/src/bin/fs_tests.rs

@@ -99,6 +99,39 @@ fn open_read_only_write(filename: &str) {
 	}
 }
 
+fn write_to_fd_test() {
+	use std::{
+		fs::File,
+		io::Write,
+		os::fd::{FromRawFd, IntoRawFd},
+	};
+
+	println!("Running write_to_fd_test.");
+	let mut stdout = unsafe { File::from_raw_fd(1) };
+	stdout.write_all(b"Wrote to stdout manually!\n").unwrap();
+	let mut stderr = unsafe { File::from_raw_fd(2) };
+	stderr.write_all(b"Wrote to stderr manually!\n").unwrap();
+
+	// File descriptors above 2 that were not obtained using an open/create hypercall
+	// should not be able to write.
+	let mut file_from_arbitrary_fd = unsafe { File::from_raw_fd(42) };
+	file_from_arbitrary_fd
+		.write_all(b"What?!?!!\n")
+		.expect_err("Could not write to fd 42.");
+
+	{
+		let mut file = File::create("/root/foo.txt").unwrap();
+		file.write_all(b"No! ").unwrap();
+		// Store file descriptor of file (and leak it).
+		let fd_leaked = file.into_raw_fd();
+		println!("File descriptor: {fd_leaked}");
+
+		// Create a new file out of the leaked file descriptor.
+		let mut fd_right = unsafe { File::from_raw_fd(fd_leaked) };
+		fd_right.write_all(b"Nothing is impossible!\n").unwrap();
+	}
+}
+
 fn lseek_file(filename: &str) {
 	let mut buf: [u8; 10] = [0; 10];
 	println!("Initial Buffer: {buf:?}");
@@ -174,6 +207,7 @@ fn main() {
 		"fd_open_remove_before_and_after_closing" => open_remove_before_and_after_closing(filename),
 		"fd_remove_twice_before_closing" => remove_twice_before_closing(filename),
 		"open_read_only_write" => open_read_only_write(filename),
+		"write_to_fd" => write_to_fd_test(),
 		"lseek_file" => lseek_file(filename),
 		"mounts_test" => mount_test(),
 		_ => panic!("test not found"),