On Mon, Dec 6, 2021 at 6:05 AM Miguel Ojeda <ojeda@xxxxxxxxxx> wrote: > > 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 our own crate. > > Co-developed-by: Alex Gaynor <alex.gaynor@xxxxxxxxx> > Signed-off-by: Alex Gaynor <alex.gaynor@xxxxxxxxx> > Co-developed-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxxx> > Signed-off-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxxx> > Co-developed-by: Sven Van Asbroeck <thesven73@xxxxxxxxx> > Signed-off-by: Sven Van Asbroeck <thesven73@xxxxxxxxx> > Co-developed-by: Gary Guo <gary@xxxxxxxxxxx> > Signed-off-by: Gary Guo <gary@xxxxxxxxxxx> > Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx> > --- > rust/compiler_builtins.rs | 57 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 57 insertions(+) > create mode 100644 rust/compiler_builtins.rs > > diff --git a/rust/compiler_builtins.rs b/rust/compiler_builtins.rs > new file mode 100644 > index 000000000000..a5a0be72591b > --- /dev/null > +++ b/rust/compiler_builtins.rs > @@ -0,0 +1,57 @@ > +// 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 floating-point 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 Rather than panic at runtime, could we do some binary post processing in Kbuild with $(NM) to error the build if any of the below symbols are referenced from .o files produced by .rs sources? If we provide definitions of these symbols, then I worry about C code that previously would have failed to link at build time when referencing these will now succeed at linking when CONFIG_RUST=y is enabled, but may panic at runtime IF we happen to hit those code paths. > +//! on `core.o`. > +//! > +//! In any case, all these symbols are weakened to ensure we do not override > +//! those that may be provided by the rest of the kernel. > +//! > +//! [`compiler_builtins`]: https://github.com/rust-lang/compiler-builtins > +//! [`compiler-rt`]: https://compiler-rt.llvm.org/ > + > +#![feature(compiler_builtins)] > +#![compiler_builtins] > +#![no_builtins] > +#![no_std] > + > +macro_rules! define_panicking_intrinsics( > + ($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, > +}); > -- > 2.34.0 > -- Thanks, ~Nick Desaulniers
