rust: generate bindings for helpers

Automatically generate rust bindings for helper functions via bindgen.
The corresponding Rust bindings will have their `rust_helper_`
prefix removed, so Rust code can call `bindings::foo` regardless
whether `foo` is directly exposed or exposed via a helper.

When both a directly exposed symbol and a helper exists, the directly
exposed symbol will take precedence.

Signed-off-by: Gary Guo <[email protected]>

Author: nbdd0121

Makefile

@@ -1839,6 +1839,7 @@ rustfmt:
 		-o -path $(abs_objtree)/rust/test -prune \
 		| grep -Fv $(abs_srctree)/rust/alloc \
 		| grep -Fv $(abs_objtree)/rust/test \
+		| grep -Fv generated \
 		| xargs $(RUSTFMT) $(rustfmt_flags)
 
 rustfmtcheck: rustfmt_flags = --check

rust/.gitignore

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 
 bindings_generated.rs
+bindings_helpers_generated.rs
 exports_*_generated.h
 doc/
 test/

rust/Makefile

@@ -5,7 +5,7 @@ extra-$(CONFIG_RUST) += exports_core_generated.h
 
 extra-$(CONFIG_RUST) += libmacros.so
 
-extra-$(CONFIG_RUST) += bindings_generated.rs
+extra-$(CONFIG_RUST) += bindings_generated.rs bindings_helpers_generated.rs
 obj-$(CONFIG_RUST) += alloc.o kernel.o
 extra-$(CONFIG_RUST) += exports_alloc_generated.h exports_kernel_generated.h
 
@@ -30,7 +30,7 @@ endif
 
 quiet_cmd_rustdoc = RUSTDOC $(if $(rustdoc_host),H, ) $<
       cmd_rustdoc = \
-	RUST_BINDINGS_FILE=$(abspath $(objtree)/rust/bindings_generated.rs) \
+	OBJTREE=$(abspath $(objtree)) \
 	$(RUSTDOC) $(if $(rustdoc_host),,$(rustc_cross_flags)) \
 		$(filter-out -Cpanic=abort, $(filter-out --emit=%, $(rustc_flags))) \
 		$(rustc_target_flags) -L $(objtree)/rust \
@@ -73,12 +73,13 @@ rustdoc-kernel: private rustc_target_flags = --extern alloc \
     --extern macros=$(objtree)/rust/libmacros.so
 rustdoc-kernel: $(srctree)/rust/kernel/lib.rs rustdoc-core \
     rustdoc-macros rustdoc-compiler_builtins rustdoc-alloc \
-    $(objtree)/rust/libmacros.so $(objtree)/rust/bindings_generated.rs FORCE
+    $(objtree)/rust/libmacros.so $(objtree)/rust/bindings_generated.rs \
+    $(objtree)/rust/bindings_helpers_generated.rs FORCE
 	$(call if_changed,rustdoc)
 
 quiet_cmd_rustc_test_library = RUSTC TL $<
       cmd_rustc_test_library = \
-	RUST_BINDINGS_FILE=$(abspath $(objtree)/rust/bindings_generated.rs) \
+	OBJTREE=$(abspath $(objtree)) \
 	$(RUSTC) $(filter-out --sysroot=%, $(filter-out -Cpanic=abort, $(filter-out --emit=%, $(rustc_flags)))) \
 		$(rustc_target_flags) --crate-type $(if $(rustc_test_library_proc),proc-macro,rlib) \
 		--out-dir $(objtree)/rust/test/ --cfg testlib \
@@ -107,7 +108,7 @@ quiet_cmd_rustdoc_test = RUSTDOC T $<
 # so for the moment we skip `-Cpanic=abort`.
 quiet_cmd_rustc_test = RUSTC T  $<
       cmd_rustc_test = \
-	RUST_BINDINGS_FILE=$(abspath $(objtree)/rust/bindings_generated.rs) \
+	OBJTREE=$(abspath $(objtree)) \
 	$(RUSTC) --test $(filter-out --sysroot=%, $(filter-out -Cpanic=abort, $(filter-out --emit=%, $(rustc_flags)))) \
 		$(rustc_target_flags) --out-dir $(objtree)/rust/test \
 		--sysroot $(objtree)/rust/test/sysroot \
@@ -228,6 +229,21 @@ $(objtree)/rust/bindings_generated.rs: $(srctree)/rust/kernel/bindings_helper.h
 	$(srctree)/rust/bindgen_parameters FORCE
 	$(call if_changed_dep,bindgen)
 
+quiet_cmd_bindgen_helper = BINDGEN $@
+      cmd_bindgen_helper = \
+	$(BINDGEN) $< --blacklist-type '.*' --whitelist-var '' \
+		--whitelist-function 'rust_helper_.*' \
+		--use-core --with-derive-default --ctypes-prefix c_types \
+		--no-debug '.*' \
+		--size_t-is-usize -o $@ -- $(bindgen_c_flags_final) \
+		-I$(objtree)/rust/ -DMODULE; \
+	sed -Ei 's/pub fn rust_helper_([a-zA-Z0-9_]*)/\#[link_name="rust_helper_\1"]\n    pub fn \1/g' $@
+
+CFLAGS_helpers.o = -I$(objtree)/rust/
+
+$(objtree)/rust/bindings_helpers_generated.rs: $(srctree)/rust/helpers.c FORCE
+	$(call if_changed_dep,bindgen_helper)
+
 quiet_cmd_exports = EXPORTS $@
       cmd_exports = \
 	$(NM) -p --defined-only $< \
@@ -265,7 +281,7 @@ $(objtree)/rust/libmacros.so: $(srctree)/rust/macros/lib.rs \
 
 quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L $@
       cmd_rustc_library = \
-	RUST_BINDINGS_FILE=$(abspath $(objtree)/rust/bindings_generated.rs) \
+	OBJTREE=$(abspath $(objtree)) \
 	$(if $(skip_clippy),$(RUSTC),$(RUSTC_OR_CLIPPY)) \
 		$(rustc_flags) $(rustc_cross_flags) $(rustc_target_flags) \
 		--crate-type rlib --out-dir $(objtree)/rust/ -L $(objtree)/rust/ \
@@ -303,7 +319,8 @@ $(objtree)/rust/kernel.o: private rustc_target_flags = --extern alloc \
     --extern macros=$(objtree)/rust/libmacros.so
 $(objtree)/rust/kernel.o: $(srctree)/rust/kernel/lib.rs $(objtree)/rust/alloc.o \
     $(objtree)/rust/build_error.o \
-    $(objtree)/rust/libmacros.so $(objtree)/rust/bindings_generated.rs FORCE
+    $(objtree)/rust/libmacros.so $(objtree)/rust/bindings_generated.rs \
+    $(objtree)/rust/bindings_helpers_generated.rs FORCE
 	$(call if_changed_dep,rustc_library)
 
 # Targets that need to expand twice

rust/helpers.c

@@ -32,7 +32,7 @@ unsigned long rust_helper_clear_user(void __user *to, unsigned long n)
 	return clear_user(to, n);
 }
 
-void rust_helper_spin_lock_init(spinlock_t *lock, const char *name,
+void rust_helper___spin_lock_init(spinlock_t *lock, const char *name,
 				struct lock_class_key *key)
 {
 #ifdef CONFIG_DEBUG_SPINLOCK
@@ -41,7 +41,7 @@ void rust_helper_spin_lock_init(spinlock_t *lock, const char *name,
 	spin_lock_init(lock);
 #endif
 }
-EXPORT_SYMBOL_GPL(rust_helper_spin_lock_init);
+EXPORT_SYMBOL_GPL(rust_helper___spin_lock_init);
 
 void rust_helper_spin_lock(spinlock_t *lock)
 {
@@ -103,22 +103,23 @@ size_t rust_helper_copy_to_iter(const void *addr, size_t bytes, struct iov_iter
 }
 EXPORT_SYMBOL_GPL(rust_helper_copy_to_iter);
 
-bool rust_helper_is_err(__force const void *ptr)
+bool rust_helper_IS_ERR(__force const void *ptr)
 {
 	return IS_ERR(ptr);
 }
-EXPORT_SYMBOL_GPL(rust_helper_is_err);
+EXPORT_SYMBOL_GPL(rust_helper_IS_ERR);
 
-long rust_helper_ptr_err(__force const void *ptr)
+long rust_helper_PTR_ERR(__force const void *ptr)
 {
 	return PTR_ERR(ptr);
 }
-EXPORT_SYMBOL_GPL(rust_helper_ptr_err);
+EXPORT_SYMBOL_GPL(rust_helper_PTR_ERR);
 
 const char *rust_helper_errname(int err)
 {
 	return errname(err);
 }
+EXPORT_SYMBOL_GPL(rust_helper_errname);
 
 void rust_helper_mutex_lock(struct mutex *lock)
 {

rust/kernel/bindings.rs

@@ -8,19 +8,37 @@
 #![cfg_attr(test, allow(deref_nullptr))]
 #![cfg_attr(test, allow(unaligned_references))]
 #![cfg_attr(test, allow(unsafe_op_in_unsafe_fn))]
-
-#[allow(
+#![allow(
     clippy::all,
     non_camel_case_types,
     non_upper_case_globals,
     non_snake_case,
     improper_ctypes,
     unsafe_op_in_unsafe_fn
 )]
+
 mod bindings_raw {
+    // Use glob import here to expose all helpers.
+    // Symbols defined within the module will take precedence to the glob import.
+    pub use super::bindings_helper::*;
+    use crate::c_types;
+    include!(concat!(env!("OBJTREE"), "/rust/bindings_generated.rs"));
+}
+
+// When both a directly exposed symbol and a helper exists for the same function,
+// the directly exposed symbol is preferred and the helper becomes dead code, so
+// ignore the warning here.
+#[allow(dead_code)]
+mod bindings_helper {
+    // Import the generated bindings for types.
+    use super::bindings_raw::*;
     use crate::c_types;
-    include!(env!("RUST_BINDINGS_FILE"));
+    include!(concat!(
+        env!("OBJTREE"),
+        "/rust/bindings_helpers_generated.rs"
+    ));
 }
+
 pub use bindings_raw::*;
 
 pub const GFP_KERNEL: gfp_t = BINDINGS_GFP_KERNEL;

rust/kernel/error.rs

@@ -98,11 +98,8 @@ impl Error {
 
 impl fmt::Debug for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        extern "C" {
-            fn rust_helper_errname(err: c_types::c_int) -> *const c_types::c_char;
-        }
         // SAFETY: FFI call.
-        let name = unsafe { rust_helper_errname(-self.0) };
+        let name = unsafe { bindings::errname(-self.0) };
 
         if name.is_null() {
             // Print out number if no name can be found.
@@ -199,7 +196,7 @@ where
 /// ) -> c_types::c_int {
 ///     from_kernel_result! {
 ///         let ptr = devm_alloc(pdev)?;
-///         rust_helper_platform_set_drvdata(pdev, ptr);
+///         bindings::platform_set_drvdata(pdev, ptr);
 ///         Ok(0)
 ///     }
 /// }
@@ -243,28 +240,20 @@ macro_rules! from_kernel_result {
 // TODO: remove `dead_code` marker once an in-kernel client is available.
 #[allow(dead_code)]
 pub(crate) fn from_kernel_err_ptr<T>(ptr: *mut T) -> Result<*mut T> {
-    extern "C" {
-        #[allow(improper_ctypes)]
-        fn rust_helper_is_err(ptr: *const c_types::c_void) -> bool;
-
-        #[allow(improper_ctypes)]
-        fn rust_helper_ptr_err(ptr: *const c_types::c_void) -> c_types::c_long;
-    }
-
     // CAST: casting a pointer to `*const c_types::c_void` is always valid.
     let const_ptr: *const c_types::c_void = ptr.cast();
     // SAFETY: the FFI function does not deref the pointer.
-    if unsafe { rust_helper_is_err(const_ptr) } {
+    if unsafe { bindings::IS_ERR(const_ptr) } {
         // SAFETY: the FFI function does not deref the pointer.
-        let err = unsafe { rust_helper_ptr_err(const_ptr) };
-        // CAST: if `rust_helper_is_err()` returns `true`,
-        // then `rust_helper_ptr_err()` is guaranteed to return a
+        let err = unsafe { bindings::PTR_ERR(const_ptr) };
+        // CAST: if `IS_ERR()` returns `true`,
+        // then `PTR_ERR()` is guaranteed to return a
         // negative value greater-or-equal to `-bindings::MAX_ERRNO`,
         // which always fits in an `i16`, as per the invariant above.
         // And an `i16` always fits in an `i32`. So casting `err` to
         // an `i32` can never overflow, and is always valid.
         //
-        // SAFETY: `rust_helper_is_err()` ensures `err` is a
+        // SAFETY: `IS_ERR()` ensures `err` is a
         // negative value greater-or-equal to `-bindings::MAX_ERRNO`
         return Err(unsafe { Error::from_kernel_errno_unchecked(err as i32) });
     }

rust/kernel/iov_iter.rs

@@ -5,26 +5,12 @@
 //! C header: [`include/linux/uio.h`](../../../../include/linux/uio.h)
 
 use crate::{
-    bindings, c_types,
+    bindings,
     error::Error,
     io_buffer::{IoBufferReader, IoBufferWriter},
     Result,
 };
 
-extern "C" {
-    fn rust_helper_copy_to_iter(
-        addr: *const c_types::c_void,
-        bytes: usize,
-        i: *mut bindings::iov_iter,
-    ) -> usize;
-
-    fn rust_helper_copy_from_iter(
-        addr: *mut c_types::c_void,
-        bytes: usize,
-        i: *mut bindings::iov_iter,
-    ) -> usize;
-}
-
 /// Wraps the kernel's `struct iov_iter`.
 ///
 /// # Invariants
@@ -70,7 +56,7 @@ impl IoBufferWriter for IovIter {
     }
 
     unsafe fn write_raw(&mut self, data: *const u8, len: usize) -> Result {
-        let res = unsafe { rust_helper_copy_to_iter(data as _, len, self.ptr) };
+        let res = unsafe { bindings::copy_to_iter(data as _, len, self.ptr) };
         if res != len {
             Err(Error::EFAULT)
         } else {
@@ -85,7 +71,7 @@ impl IoBufferReader for IovIter {
     }
 
     unsafe fn read_raw(&mut self, out: *mut u8, len: usize) -> Result {
-        let res = unsafe { rust_helper_copy_from_iter(out as _, len, self.ptr) };
+        let res = unsafe { bindings::copy_from_iter(out as _, len, self.ptr) };
         if res != len {
             Err(Error::EFAULT)
         } else {

rust/kernel/pages.rs

@@ -10,20 +10,6 @@ use crate::{
 };
 use core::{marker::PhantomData, ptr};
 
-extern "C" {
-    #[allow(improper_ctypes)]
-    fn rust_helper_alloc_pages(
-        gfp_mask: bindings::gfp_t,
-        order: c_types::c_uint,
-    ) -> *mut bindings::page;
-
-    #[allow(improper_ctypes)]
-    fn rust_helper_kmap(page: *mut bindings::page) -> *mut c_types::c_void;
-
-    #[allow(improper_ctypes)]
-    fn rust_helper_kunmap(page: *mut bindings::page);
-}
-
 /// A set of physical pages.
 ///
 /// `Pages` holds a reference to a set of pages of order `ORDER`. Having the order as a generic
@@ -42,7 +28,7 @@ impl<const ORDER: u32> Pages<ORDER> {
         // TODO: Consider whether we want to allow callers to specify flags.
         // SAFETY: This only allocates pages. We check that it succeeds in the next statement.
         let pages = unsafe {
-            rust_helper_alloc_pages(
+            bindings::alloc_pages(
                 bindings::GFP_KERNEL | bindings::__GFP_ZERO | bindings::__GFP_HIGHMEM,
                 ORDER,
             )
@@ -141,7 +127,7 @@ impl<const ORDER: u32> Pages<ORDER> {
         let page = unsafe { self.pages.add(index) };
 
         // SAFETY: `page` is valid based on the checks above.
-        let ptr = unsafe { rust_helper_kmap(page) };
+        let ptr = unsafe { bindings::kmap(page) };
         if ptr.is_null() {
             return None;
         }
@@ -171,6 +157,6 @@ impl Drop for PageMapping<'_> {
     fn drop(&mut self) {
         // SAFETY: An instance of `PageMapping` is created only when `kmap` succeeded for the given
         // page, so it is safe to unmap it here.
-        unsafe { rust_helper_kunmap(self.page) };
+        unsafe { bindings::kunmap(self.page) };
     }
 }

rust/kernel/platdev.rs

@@ -29,19 +29,6 @@ pub struct Registration {
 // (it is fine for multiple threads to have a shared reference to it).
 unsafe impl Sync for Registration {}
 
-extern "C" {
-    #[allow(improper_ctypes)]
-    fn rust_helper_platform_get_drvdata(
-        pdev: *const bindings::platform_device,
-    ) -> *mut c_types::c_void;
-
-    #[allow(improper_ctypes)]
-    fn rust_helper_platform_set_drvdata(
-        pdev: *mut bindings::platform_device,
-        data: *mut c_types::c_void,
-    );
-}
-
 extern "C" fn probe_callback<P: PlatformDriver>(
     pdev: *mut bindings::platform_device,
 ) -> c_types::c_int {
@@ -52,7 +39,7 @@ extern "C" fn probe_callback<P: PlatformDriver>(
         let drv_data = drv_data.into_pointer() as *mut c_types::c_void;
         // SAFETY: `pdev` is guaranteed to be a valid, non-null pointer.
         unsafe {
-            rust_helper_platform_set_drvdata(pdev, drv_data);
+            bindings::platform_set_drvdata(pdev, drv_data);
         }
         Ok(0)
     }
@@ -65,7 +52,7 @@ extern "C" fn remove_callback<P: PlatformDriver>(
         // SAFETY: `pdev` is guaranteed to be a valid, non-null pointer.
         let device_id = unsafe { (*pdev).id };
         // SAFETY: `pdev` is guaranteed to be a valid, non-null pointer.
-        let ptr = unsafe { rust_helper_platform_get_drvdata(pdev) };
+        let ptr = unsafe { bindings::platform_get_drvdata(pdev) };
         // SAFETY:
         //   - we allocated this pointer using `P::DrvData::into_pointer`,
         //     so it is safe to turn back into a `P::DrvData`.

rust/kernel/rbtree.rs

@@ -16,14 +16,6 @@ use core::{
     ptr::{addr_of_mut, NonNull},
 };
 
-extern "C" {
-    fn rust_helper_rb_link_node(
-        node: *mut bindings::rb_node,
-        parent: *const bindings::rb_node,
-        rb_link: *mut *mut bindings::rb_node,
-    );
-}
-
 struct Node<K, V> {
     links: bindings::rb_node,
     key: K,
@@ -289,7 +281,7 @@ impl<K, V> RBTree<K, V> {
         // "forgot" it with `Box::into_raw`.
         // SAFETY: All pointers are non-null and valid (`*new_link` is null, but `new_link` is a
         // mutable reference).
-        unsafe { rust_helper_rb_link_node(node_links, parent, new_link) };
+        unsafe { bindings::rb_link_node(node_links, parent, new_link) };
 
         // SAFETY: All pointers are valid. `node` has just been inserted into the tree.
         unsafe { bindings::rb_insert_color(node_links, &mut self.root) };