aarch64-unknown-none and aarch64-unknown-none-softfloat
- Tier: 2
- Library Support: core and alloc (bare-metal,
#![no_std])
Bare-metal targets for CPUs in the Armv8-A architecture family, running in AArch64 mode.
For the AArch32 mode carried over from Armv7-A, see
armv7a-none-eabi instead.
Processors in this family include the Arm Cortex-A35, 53, 76, etc.
Target maintainers
Rust Embedded Devices Working Group Arm Team
Target CPU and Target Feature options
All AArch64 processors include an FPU. The difference between the -none and
-none-softfloat targets is whether the FPU is used for passing function arguments.
You may prefer the -softfloat target when writing a kernel or interfacing with
pre-compiled binaries that use the soft-float ABI.
When using the hardfloat targets, the minimum floating-point features assumed
are those of the fp-armv8, which excludes NEON SIMD support. If your
processor supports a different set of floating-point features than the default
expectations of fp-armv8, then these should also be enabled or disabled as
needed with -C target-feature=(+/-). It is also possible to tell Rust (or
LLVM) that you have a specific model of Arm processor, using the
-Ctarget-cpu option. Doing so may change the default set of
target-features enabled.
Requirements
These targets are cross-compiled and use static linking.
By default, the lld linker included with Rust will be used; however, you may
want to use the GNU linker instead. This can be obtained for Windows/Mac/Linux
from the Arm Developer Website, or possibly from your OS's
package manager. To use it, add the following to your .cargo/config.toml:
[target.aarch64-unknown-none]
linker = "aarch64-none-elf-ld"
The GNU linker can also be used by specifying aarch64-none-elf-gcc as the
linker. This is needed when using GCC's link time optimization.
These targets don't provide a linker script, so you'll need to bring your own
according to the specific device you are using. Pass
-Clink-arg=-Tyour_script.ld as a rustc argument to make the linker use
your_script.ld during linking.
Cross-compilation toolchains and C code
This target supports C code compiled with the aarch64-none-elf target
triple and a suitable -march or -mcpu flag.
Start-up and Low-Level Code
The Rust Embedded Devices Working Group Arm Team maintain the
aarch64-cpu crate, which may be useful for writing bare-metal code using
this target.
The TrustedFirmware group also maintain Rust crates for this target.