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// SPDX-License-Identifier: GPL-2.0
/*
* Non-trivial C macros cannot be used in Rust. Similarly, inlined C functions
* cannot be called either. This file explicitly creates functions ("helpers")
* that wrap those so that they can be called from Rust.
*
* Even though Rust kernel modules should never use directly the bindings, some
* of these helpers need to be exported because Rust generics and inlined
* functions may not get their code generated in the crate where they are
* defined. Other helpers, called from non-inline functions, may not be
* exported, in principle. However, in general, the Rust compiler does not
* guarantee codegen will be performed for a non-inline function either.
* Therefore, this file exports all the helpers. In the future, this may be
* revisited to reduce the number of exports after the compiler is informed
* about the places codegen is required.
*
* All symbols are exported as GPL-only to guarantee no GPL-only feature is
* accidentally exposed.
*/
#include <linux/bug.h>
#include <linux/build_bug.h>
__noreturn void rust_helper_BUG(void)
{
BUG();
}
EXPORT_SYMBOL_GPL(rust_helper_BUG);
/*
* We use `bindgen`'s `--size_t-is-usize` option to bind the C `size_t` type
* as the Rust `usize` type, so we can use it in contexts where Rust
* expects a `usize` like slice (array) indices. `usize` is defined to be
* the same as C's `uintptr_t` type (can hold any pointer) but not
* necessarily the same as `size_t` (can hold the size of any single
* object). Most modern platforms use the same concrete integer type for
* both of them, but in case we find ourselves on a platform where
* that's not true, fail early instead of risking ABI or
* integer-overflow issues.
*
* If your platform fails this assertion, it means that you are in
* danger of integer-overflow bugs (even if you attempt to remove
* `--size_t-is-usize`). It may be easiest to change the kernel ABI on
* your platform such that `size_t` matches `uintptr_t` (i.e., to increase
* `size_t`, because `uintptr_t` has to be at least as big as `size_t`).
*/
static_assert(
sizeof(size_t) == sizeof(uintptr_t) &&
__alignof__(size_t) == __alignof__(uintptr_t),
"Rust code expects C `size_t` to match Rust `usize`"
);
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