1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Non-trivial C macros cannot be used in Rust. Similarly, inlined C functions 4 * cannot be called either. This file explicitly creates functions ("helpers") 5 * that wrap those so that they can be called from Rust. 6 * 7 * Even though Rust kernel modules should never use directly the bindings, some 8 * of these helpers need to be exported because Rust generics and inlined 9 * functions may not get their code generated in the crate where they are 10 * defined. Other helpers, called from non-inline functions, may not be 11 * exported, in principle. However, in general, the Rust compiler does not 12 * guarantee codegen will be performed for a non-inline function either. 13 * Therefore, this file exports all the helpers. In the future, this may be 14 * revisited to reduce the number of exports after the compiler is informed 15 * about the places codegen is required. 16 * 17 * All symbols are exported as GPL-only to guarantee no GPL-only feature is 18 * accidentally exposed. 19 */ 20 21 #include <linux/bug.h> 22 #include <linux/build_bug.h> 23 24 __noreturn void rust_helper_BUG(void) 25 { 26 BUG(); 27 } 28 EXPORT_SYMBOL_GPL(rust_helper_BUG); 29 30 /* 31 * We use `bindgen`'s `--size_t-is-usize` option to bind the C `size_t` type 32 * as the Rust `usize` type, so we can use it in contexts where Rust 33 * expects a `usize` like slice (array) indices. `usize` is defined to be 34 * the same as C's `uintptr_t` type (can hold any pointer) but not 35 * necessarily the same as `size_t` (can hold the size of any single 36 * object). Most modern platforms use the same concrete integer type for 37 * both of them, but in case we find ourselves on a platform where 38 * that's not true, fail early instead of risking ABI or 39 * integer-overflow issues. 40 * 41 * If your platform fails this assertion, it means that you are in 42 * danger of integer-overflow bugs (even if you attempt to remove 43 * `--size_t-is-usize`). It may be easiest to change the kernel ABI on 44 * your platform such that `size_t` matches `uintptr_t` (i.e., to increase 45 * `size_t`, because `uintptr_t` has to be at least as big as `size_t`). 46 */ 47 static_assert( 48 sizeof(size_t) == sizeof(uintptr_t) && 49 __alignof__(size_t) == __alignof__(uintptr_t), 50 "Rust code expects C `size_t` to match Rust `usize`" 51 ); 52