Freestanding/bare-metal x86-64 binaries in ELF format: firmware, kernels, etc.
- Harald Hoyer
- Mike Leany, https://github.com/mikeleany
This target is cross-compiled. There is no support for
std. There is no
default allocator, but it's possible to use
alloc by supplying an allocator.
By default, Rust code generated for this target does not use any vector or
floating-point registers (e.g. SSE, AVX). This allows the generated code to run
in environments, such as kernels, which may need to avoid the use of such
registers or which may have special considerations about the use of such
registers (e.g. saving and restoring them to avoid breaking userspace code
using the same registers). You can change code generation to use additional CPU
features via the
-C target-feature= codegen options to rustc, or via the
#[target_feature] mechanism within Rust code.
By default, code generated with this target should run on any
hardware; enabling additional target features may raise this baseline.
Code generated with this target will use the
kernel code model by default.
You can change this using the
-C code-model= option to rustc.
extern "C" uses the standard System V calling
convention, without red zones.
This target generates binaries in the ELF format. Any alternate formats or special considerations for binary layout will require linker options or linker scripts.
Building the target
You can build Rust with support for the target by adding it to the
[build] build-stage = 1 target = ["x86_64-unknown-none"]
Building Rust programs
Starting with Rust 1.62, precompiled artifacts are provided via
# install cross-compile toolchain rustup target add x86_64-unknown-none # target flag may be used with any cargo or rustc command cargo build --target x86_64-unknown-none
x86_64-unknown-none supports a variety of different environments and does
std, this target does not support running the Rust test suite.
Cross-compilation toolchains and C code
If you want to compile C code along with Rust (such as for Rust crates with C
dependencies), you will need an appropriate
Rust may be able to use an
x86_64-linux-gnu- toolchain with appropriate
standalone flags to build for this toolchain (depending on the assumptions of
that toolchain, see below), or you may wish to use a separate
x86_64 hosts that use ELF binaries, you may be able to use the host
C toolchain, if it does not introduce assumptions about the host environment
that don't match the expectations of a standalone environment. Otherwise, you
may need a separate toolchain for standalone/freestanding development, just as
when cross-compiling from a non-