[PATCH v8 02/10] rust: module: add `THIS_MODULE` const to `ModuleMetadata` trait

[Alvin Sun]

Since `const_refs_to_static` has been stable as of the MSRV bump, a
`ThisModule` pointer can now be used in const contexts.

Add a `THIS_MODULE` const to the `ModuleMetadata` trait so that modules
can provide their `ThisModule` pointer in const contexts such as static
`file_operations`.

Add a `this_module()` helper to retrieve the `THIS_MODULE` pointer of a
given module type, and update `__init` to use it instead of the
`THIS_MODULE` static generated by the `module!` macro.

The `static THIS_MODULE` generated by the `module!` macro is retained
for backwards compatibility with existing users and removed in a later
patch once all references have been migrated.

Assisted-by: opencode:glm-5.2
Reviewed-by: Andreas Hindborg <a.hin...@kernel.org>
Reviewed-by: Gary Guo <ga...@garyguo.net>
Acked-by: Danilo Krummrich <da...@kernel.org>
Signed-off-by: Alvin Sun <alvi...@linux.dev>
---
rust/kernel/module.rs | 9 +++++++++
rust/macros/module.rs | 18 +++++++++++++++++-
2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/module.rs b/rust/kernel/module.rs
index be242a82e86d2..d713705984477 100644
--- a/rust/kernel/module.rs
+++ b/rust/kernel/module.rs
@@ -42,6 +42,15 @@ fn init(module: &'static ThisModule) -> impl pin_init::PinInit<Self, crate::erro
pub trait ModuleMetadata {
/// The name of the module as specified in the `module!` macro.
const NAME: &'static crate::str::CStr;
+
+ /// The module's `THIS_MODULE` pointer.
+ const THIS_MODULE: ThisModule;
+}
+
+/// Returns a reference to the `THIS_MODULE` of the given module type.
+#[inline]
+pub const fn this_module<M: ModuleMetadata>() -> &'static ThisModule {
+ &M::THIS_MODULE
}

/// Equivalent to `THIS_MODULE` in the C API.
diff --git a/rust/macros/module.rs b/rust/macros/module.rs
index 06c18e2075083..aa9a618d5d19e 100644
--- a/rust/macros/module.rs
+++ b/rust/macros/module.rs
@@ -519,6 +519,22 @@ pub(crate) fn module(info: ModuleInfo) -> Result<TokenStream> {

impl ::kernel::ModuleMetadata for #type_ {
const NAME: &'static ::kernel::str::CStr = #name_cstr;
+
+ #[cfg(MODULE)]
+ const THIS_MODULE: ::kernel::ThisModule = {
+ extern "C" {
+ static __this_module: ::kernel::types::Opaque<::kernel::bindings::module>;
+ }
+
+ // SAFETY: `__this_module` is constructed by the kernel at load time
+ // and lives until the module is unloaded.
+ unsafe { ::kernel::ThisModule::from_ptr(__this_module.get()) }
+ };
+
+ #[cfg(not(MODULE))]
+ const THIS_MODULE: ::kernel::ThisModule = unsafe {
+ ::kernel::ThisModule::from_ptr(::core::ptr::null_mut())
+ };
}

// Double nested modules, since then nobody can access the public items inside.
@@ -616,7 +632,7 @@ pub extern "C" fn #ident_exit() {
/// This function must only be called once.
unsafe fn __init() -> ::kernel::ffi::c_int {
let initer = <super::super::LocalModule as ::kernel::InPlaceModule>::init(
- &super::super::THIS_MODULE
+ ::kernel::module::this_module::<super::super::LocalModule>()
);
// SAFETY: No data race, since `__MOD` can only be accessed by this module
// and there only `__init` and `__exit` access it. These functions are only

--
2.43.0

[Alvin Sun]

Since `const_refs_to_static` has been stable as of the MSRV bump, a
`ThisModule` pointer can now be used in const contexts.

Add a `THIS_MODULE` const to the `ModuleMetadata` trait so that modules
can provide their `ThisModule` pointer in const contexts such as static
`file_operations`.

Add a `this_module()` helper to retrieve the `THIS_MODULE` pointer of a
given module type, and update `__init` to use it instead of the
`THIS_MODULE` static generated by the `module!` macro.

The `static THIS_MODULE` generated by the `module!` macro is retained
for backwards compatibility with existing users and removed in a later
patch once all references have been migrated.

Assisted-by: opencode:glm-5.2
Reviewed-by: Andreas Hindborg <a.hin...@kernel.org>
Reviewed-by: Gary Guo <ga...@garyguo.net>
Acked-by: Danilo Krummrich <da...@kernel.org>

Reviewed-by: Alice Ryhl <alic...@google.com>