Add tests for filesystem::register (#197)

* Add tests for filesystem::register

Check whether loading the module makes the name of the filesystem
(testfs) appear in /proc/filesystems

* Improve name for /proc/filesystems test

* Mark filesystem::Registration<T: FileSystem> as Sync

* Make Sync a supertrait of filesystem::FileSystem

* Use cstr!() macro in const context

* Remove unneeded const_raw_ptr_deref feature

* Remove redundant "\x00" from the end of "testfs"

Author: luisgerhorst

src/filesystem.rs

@@ -14,13 +14,16 @@ pub struct Registration<T: FileSystem> {
     ptr: Box<bindings::file_system_type>,
 }
 
+// This is safe because Registration doesn't actually expose any methods.
+unsafe impl<T> Sync for Registration<T> where T: FileSystem {}
+
 impl<T: FileSystem> Drop for Registration<T> {
     fn drop(&mut self) {
         unsafe { bindings::unregister_filesystem(&mut *self.ptr) };
     }
 }
 
-pub trait FileSystem {
+pub trait FileSystem: Sync {
     const NAME: &'static CStr;
     const FLAGS: FileSystemFlags;
 }

tests/filesystem/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "filesystem-tests"
+version = "0.1.0"
+authors = ["Luis Gerhorst <privat@luisgerhorst.de>", "Alex Gaynor <alex.gaynor@gmail.com>", "Geoffrey Thomas <geofft@ldpreload.com>"]
+edition = "2018"
+
+[lib]
+crate-type = ["staticlib"]
+test = false
+
+[features]
+default = ["linux-kernel-module"]
+
+[dependencies]
+linux-kernel-module = { path = "../..", optional = true }
+
+[dev-dependencies]
+kernel-module-testlib = { path = "../../testlib" }

tests/filesystem/src/lib.rs

@@ -0,0 +1,34 @@
+#![no_std]
+#![feature(const_str_as_bytes)]
+
+extern crate alloc;
+
+use linux_kernel_module::filesystem::{self, FileSystem, FileSystemFlags};
+use linux_kernel_module::{self, cstr, CStr};
+
+struct TestFSModule {
+    _fs_registration: filesystem::Registration<TestFS>,
+}
+
+struct TestFS {}
+
+impl FileSystem for TestFS {
+    const NAME: &'static CStr = cstr!("testfs");
+    const FLAGS: FileSystemFlags = FileSystemFlags::FS_REQUIRES_DEV;
+}
+
+impl linux_kernel_module::KernelModule for TestFSModule {
+    fn init() -> linux_kernel_module::KernelResult<Self> {
+        let fs_registration = filesystem::register::<TestFS>()?;
+        Ok(TestFSModule {
+            _fs_registration: fs_registration,
+        })
+    }
+}
+
+linux_kernel_module::kernel_module!(
+    TestFSModule,
+    author: "Fish in a Barrel Contributors",
+    description: "A module for testing filesystem::register",
+    license: "GPL"
+);

tests/filesystem/tests/tests.rs

@@ -0,0 +1,17 @@
+use std::fs;
+
+use kernel_module_testlib::with_kernel_module;
+
+#[test]
+fn test_proc_filesystems() {
+    let filesystems = fs::read_to_string("/proc/filesystems").unwrap();
+    assert!(!filesystems.contains("testfs"));
+
+    with_kernel_module(|| {
+        let filesystems = fs::read_to_string("/proc/filesystems").unwrap();
+        assert!(filesystems.contains("testfs"));
+    });
+
+    let filesystems = fs::read_to_string("/proc/filesystems").unwrap();
+    assert!(!filesystems.contains("testfs"));
+}