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 #include <linux/refcount.h> 24 25 __noreturn void rust_helper_BUG(void) 26 { 27 BUG(); 28 } 29 EXPORT_SYMBOL_GPL(rust_helper_BUG); 30 31 refcount_t rust_helper_REFCOUNT_INIT(int n) 32 { 33 return (refcount_t)REFCOUNT_INIT(n); 34 } 35 EXPORT_SYMBOL_GPL(rust_helper_REFCOUNT_INIT); 36 37 void rust_helper_refcount_inc(refcount_t *r) 38 { 39 refcount_inc(r); 40 } 41 EXPORT_SYMBOL_GPL(rust_helper_refcount_inc); 42 43 bool rust_helper_refcount_dec_and_test(refcount_t *r) 44 { 45 return refcount_dec_and_test(r); 46 } 47 EXPORT_SYMBOL_GPL(rust_helper_refcount_dec_and_test); 48 49 /* 50 * We use `bindgen`'s `--size_t-is-usize` option to bind the C `size_t` type 51 * as the Rust `usize` type, so we can use it in contexts where Rust 52 * expects a `usize` like slice (array) indices. `usize` is defined to be 53 * the same as C's `uintptr_t` type (can hold any pointer) but not 54 * necessarily the same as `size_t` (can hold the size of any single 55 * object). Most modern platforms use the same concrete integer type for 56 * both of them, but in case we find ourselves on a platform where 57 * that's not true, fail early instead of risking ABI or 58 * integer-overflow issues. 59 * 60 * If your platform fails this assertion, it means that you are in 61 * danger of integer-overflow bugs (even if you attempt to remove 62 * `--size_t-is-usize`). It may be easiest to change the kernel ABI on 63 * your platform such that `size_t` matches `uintptr_t` (i.e., to increase 64 * `size_t`, because `uintptr_t` has to be at least as big as `size_t`). 65 */ 66 static_assert( 67 sizeof(size_t) == sizeof(uintptr_t) && 68 __alignof__(size_t) == __alignof__(uintptr_t), 69 "Rust code expects C `size_t` to match Rust `usize`" 70 ); 71