Implement THIS_MODULE.

Closes #15
Fixes #10

rust/kernel/chrdev.rs

@@ -38,7 +38,7 @@ impl Builder {
         self
     }
 
-    pub fn build(self) -> KernelResult<Registration> {
+    pub fn build(self, this_module: &'static crate::ThisModule) -> KernelResult<Registration> {
         let mut dev: bindings::dev_t = 0;
         let res = unsafe {
             bindings::alloc_chrdev_region(
@@ -58,8 +58,7 @@ impl Builder {
         for (i, file_op) in self.file_ops.iter().enumerate() {
             unsafe {
                 bindings::cdev_init(&mut cdevs[i], *file_op);
-                // TODO: proper `THIS_MODULE` handling
-                cdevs[i].owner = core::ptr::null_mut();
+                cdevs[i].owner = this_module.0;
                 let rc = bindings::cdev_add(&mut cdevs[i], dev + i as bindings::dev_t, 1);
                 if rc != 0 {
                     // Clean up the ones that were allocated.

rust/kernel/lib.rs

@@ -44,6 +44,18 @@ pub trait KernelModule: Sized + Sync {
     fn init() -> KernelResult<Self>;
 }
 
+/// An instance equivalent to `THIS_MODULE` in C code.
+pub struct ThisModule(*mut bindings::module);
+
+// Safe because THIS_MODULE may be used from all threads within a module.
+unsafe impl Sync for ThisModule {}
+
+impl ThisModule {
+    pub const unsafe fn from_ptr(ptr: *mut bindings::module) -> ThisModule {
+        ThisModule(ptr)
+    }
+}
+
 extern "C" {
     fn rust_helper_BUG() -> !;
 }

rust/module.rs

@@ -309,6 +309,11 @@ pub fn module(ts: TokenStream) -> TokenStream {
         "
             static mut __MOD: Option<{type_}> = None;
 
+            #[cfg(MODULE)]
+            static THIS_MODULE: kernel::ThisModule = kernel::ThisModule::from_ptr(&mut kernel::bindings::__this_module);
+            #[cfg(not(MODULE))]
+            static THIS_MODULE: kernel::ThisModule = kernel::ThisModule::from_ptr(core::ptr::null_mut());
+
             // Loadable modules need to export the `{{init,cleanup}}_module` identifiers
             #[cfg(MODULE)]
             #[no_mangle]