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![Alice Ryhl](/assets/img/avatar_default.png)
The main challenge with defining `work_struct` fields is making sure that the function pointer stored in the `work_struct` is appropriate for the work item type it is embedded in. It needs to know the offset of the `work_struct` field being used (even if there are several!) so that it can do a `container_of`, and it needs to know the type of the work item so that it can call into the right user-provided code. All of this needs to happen in a way that provides a safe API to the user, so that users of the workqueue cannot mix up the function pointers. There are three important pieces that are relevant when doing this: * The pointer type. * The work item struct. This is what the pointer points at. * The `work_struct` field. This is a field of the work item struct. This patch introduces a separate trait for each piece. The pointer type is given a `WorkItemPointer` trait, which pointer types need to implement to be usable with the workqueue. This trait will be implemented for `Arc` and `Box` in a later patch in this patchset. Implementing this trait is unsafe because this is where the `container_of` operation happens, but user-code will not need to implement it themselves. The work item struct should then implement the `WorkItem` trait. This trait is where user-code specifies what they want to happen when a work item is executed. It also specifies what the correct pointer type is. Finally, to make the work item struct know the offset of its `work_struct` field, we use a trait called `HasWork<T, ID>`. If a type implements this trait, then the type declares that, at the given offset, there is a field of type `Work<T, ID>`. The trait is marked unsafe because the OFFSET constant must be correct, but we provide an `impl_has_work!` macro that can safely implement `HasWork<T>` on a type. The macro expands to something that only compiles if the specified field really has the type `Work<T>`. It is used like this: ``` struct MyWorkItem { work_field: Work<MyWorkItem, 1>, } impl_has_work! { impl HasWork<MyWorkItem, 1> for MyWorkItem { self.work_field } } ``` Note that since the `Work` type is annotated with an id, you can have several `work_struct` fields by using a different id for each one. Co-developed-by: Gary Guo <gary@garyguo.net> Signed-off-by: Gary Guo <gary@garyguo.net> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Benno Lossin <benno.lossin@proton.me> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com> Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com> Reviewed-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Tejun Heo <tj@kernel.org>
181 lines
5 KiB
C
181 lines
5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Non-trivial C macros cannot be used in Rust. Similarly, inlined C functions
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* cannot be called either. This file explicitly creates functions ("helpers")
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* that wrap those so that they can be called from Rust.
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*
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* Even though Rust kernel modules should never use directly the bindings, some
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* of these helpers need to be exported because Rust generics and inlined
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* functions may not get their code generated in the crate where they are
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* defined. Other helpers, called from non-inline functions, may not be
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* exported, in principle. However, in general, the Rust compiler does not
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* guarantee codegen will be performed for a non-inline function either.
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* Therefore, this file exports all the helpers. In the future, this may be
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* revisited to reduce the number of exports after the compiler is informed
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* about the places codegen is required.
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*
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* All symbols are exported as GPL-only to guarantee no GPL-only feature is
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* accidentally exposed.
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*
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* Sorted alphabetically.
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*/
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#include <kunit/test-bug.h>
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#include <linux/bug.h>
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#include <linux/build_bug.h>
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#include <linux/err.h>
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#include <linux/errname.h>
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#include <linux/mutex.h>
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#include <linux/refcount.h>
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#include <linux/sched/signal.h>
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#include <linux/spinlock.h>
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#include <linux/wait.h>
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#include <linux/workqueue.h>
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__noreturn void rust_helper_BUG(void)
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{
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BUG();
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}
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EXPORT_SYMBOL_GPL(rust_helper_BUG);
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void rust_helper_mutex_lock(struct mutex *lock)
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{
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mutex_lock(lock);
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}
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EXPORT_SYMBOL_GPL(rust_helper_mutex_lock);
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void rust_helper___spin_lock_init(spinlock_t *lock, const char *name,
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struct lock_class_key *key)
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{
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#ifdef CONFIG_DEBUG_SPINLOCK
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__raw_spin_lock_init(spinlock_check(lock), name, key, LD_WAIT_CONFIG);
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#else
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spin_lock_init(lock);
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#endif
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}
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EXPORT_SYMBOL_GPL(rust_helper___spin_lock_init);
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void rust_helper_spin_lock(spinlock_t *lock)
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{
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spin_lock(lock);
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}
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EXPORT_SYMBOL_GPL(rust_helper_spin_lock);
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void rust_helper_spin_unlock(spinlock_t *lock)
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{
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spin_unlock(lock);
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}
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EXPORT_SYMBOL_GPL(rust_helper_spin_unlock);
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void rust_helper_init_wait(struct wait_queue_entry *wq_entry)
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{
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init_wait(wq_entry);
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}
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EXPORT_SYMBOL_GPL(rust_helper_init_wait);
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int rust_helper_signal_pending(struct task_struct *t)
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{
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return signal_pending(t);
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}
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EXPORT_SYMBOL_GPL(rust_helper_signal_pending);
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refcount_t rust_helper_REFCOUNT_INIT(int n)
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{
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return (refcount_t)REFCOUNT_INIT(n);
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}
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EXPORT_SYMBOL_GPL(rust_helper_REFCOUNT_INIT);
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void rust_helper_refcount_inc(refcount_t *r)
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{
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refcount_inc(r);
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}
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EXPORT_SYMBOL_GPL(rust_helper_refcount_inc);
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bool rust_helper_refcount_dec_and_test(refcount_t *r)
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{
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return refcount_dec_and_test(r);
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}
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EXPORT_SYMBOL_GPL(rust_helper_refcount_dec_and_test);
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__force void *rust_helper_ERR_PTR(long err)
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{
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return ERR_PTR(err);
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}
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EXPORT_SYMBOL_GPL(rust_helper_ERR_PTR);
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bool rust_helper_IS_ERR(__force const void *ptr)
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{
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return IS_ERR(ptr);
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}
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EXPORT_SYMBOL_GPL(rust_helper_IS_ERR);
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long rust_helper_PTR_ERR(__force const void *ptr)
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{
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return PTR_ERR(ptr);
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}
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EXPORT_SYMBOL_GPL(rust_helper_PTR_ERR);
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const char *rust_helper_errname(int err)
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{
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return errname(err);
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}
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EXPORT_SYMBOL_GPL(rust_helper_errname);
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struct task_struct *rust_helper_get_current(void)
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{
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return current;
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}
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EXPORT_SYMBOL_GPL(rust_helper_get_current);
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void rust_helper_get_task_struct(struct task_struct *t)
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{
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get_task_struct(t);
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}
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EXPORT_SYMBOL_GPL(rust_helper_get_task_struct);
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void rust_helper_put_task_struct(struct task_struct *t)
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{
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put_task_struct(t);
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}
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EXPORT_SYMBOL_GPL(rust_helper_put_task_struct);
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struct kunit *rust_helper_kunit_get_current_test(void)
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{
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return kunit_get_current_test();
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}
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EXPORT_SYMBOL_GPL(rust_helper_kunit_get_current_test);
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void rust_helper_init_work_with_key(struct work_struct *work, work_func_t func,
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bool onstack, const char *name,
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struct lock_class_key *key)
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{
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__init_work(work, onstack);
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work->data = (atomic_long_t)WORK_DATA_INIT();
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lockdep_init_map(&work->lockdep_map, name, key, 0);
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INIT_LIST_HEAD(&work->entry);
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work->func = func;
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}
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EXPORT_SYMBOL_GPL(rust_helper_init_work_with_key);
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/*
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* `bindgen` binds the C `size_t` type as the Rust `usize` type, so we can
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* use it in contexts where Rust expects a `usize` like slice (array) indices.
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* `usize` is defined to be the same as C's `uintptr_t` type (can hold any
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* pointer) but not necessarily the same as `size_t` (can hold the size of any
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* single object). Most modern platforms use the same concrete integer type for
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* both of them, but in case we find ourselves on a platform where
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* that's not true, fail early instead of risking ABI or
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* integer-overflow issues.
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*
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* If your platform fails this assertion, it means that you are in
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* danger of integer-overflow bugs (even if you attempt to add
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* `--no-size_t-is-usize`). It may be easiest to change the kernel ABI on
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* your platform such that `size_t` matches `uintptr_t` (i.e., to increase
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* `size_t`, because `uintptr_t` has to be at least as big as `size_t`).
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*/
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static_assert(
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sizeof(size_t) == sizeof(uintptr_t) &&
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__alignof__(size_t) == __alignof__(uintptr_t),
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"Rust code expects C `size_t` to match Rust `usize`"
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);
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