linux-next/rust/compiler_builtins.rs

// SPDX-License-Identifier: GPL-2.0

//! Our own `compiler_builtins`.
//!
//! Rust provides [`compiler_builtins`] as a port of LLVM's [`compiler-rt`].
//! Since we do not need the vast majority of them, we avoid the dependency
//! by providing this file.
//!
//! At the moment, some builtins are required that should not be. For instance,
//! [`core`] has 128-bit integers functionality which we should not be compiling
//! in. We will work with upstream [`core`] to provide feature flags to disable
//! the parts we do not need. For the moment, we define them to [`panic!`] at
//! runtime for simplicity to catch mistakes, instead of performing surgery
//! on `core.o`.
//!
//! In any case, all these symbols are weakened to ensure we do not override
//! those that may be provided by the rest of the kernel.
//!
//! [`compiler_builtins`]: https://github.com/rust-lang/compiler-builtins
//! [`compiler-rt`]: https://compiler-rt.llvm.org/

#![feature(compiler_builtins)]
#![compiler_builtins]
#![no_builtins]
#![no_std]

macro_rules! define_panicking_intrinsics(
    ($reason: tt, { $($ident: ident, )* }) => {
        $(
            #[doc(hidden)]
            #[no_mangle]
            pub extern "C" fn $ident() {
                panic!($reason);
            }
        )*
    }
);

define_panicking_intrinsics!("`i128` should not be used", {
    __ashrti3,
    __muloti4,
    __multi3,
});

define_panicking_intrinsics!("`u128` should not be used", {
    __ashlti3,
    __lshrti3,
    __udivmodti4,
    __udivti3,
    __umodti3,
});

#[cfg(target_arch = "arm")]
define_panicking_intrinsics!("`u64` division/modulo should not be used", {
    __aeabi_uldivmod,
    __mulodi4,
});