cortex-a

Low level access to Cortex-A processors.

Currently Supported Execution States

• [x] AArch64
• [ ] AArch32

Minimum Supported Rust Version

Requires a recent nightly of Rust.

Usage

Please note that for using this crate's register definitions (as provided by cortex_a::registers::*), you need to also include tock-registers in your project. This is because the interface traits provided by tock-registers are implemented by this crate. You should include the same version of tock-registers as is being used by this crate to ensure sane interoperatbility.

For example, in the following snippet, X.Y.Z should be the same version of tock-registers that is mentioned in cortex-a's Cargo.toml.

[package]
name = "Your embedded project"

# Some parts omitted for brevity.

[dependencies]
tock-registers = "X.Y.Z"
cortex-a = "A.B.C"       # <-- Includes tock-registers itself.

Example

Check out https://github.com/rust-embedded/rust-raspberrypi-OS-tutorials for usage examples. Listed below is a snippet of rust-raspberrypi-OS-tutorials's early boot code.

use cortex_a::{asm, registers::*};
use tock_registers::interfaces::Writeable; // <-- Trait needed to use `write()` and `set()`.

// Some parts omitted for brevity.

unsafe fn prepare_el2_to_el1_transition(
    virt_boot_core_stack_end_exclusive_addr: u64,
    virt_kernel_init_addr: u64,
) {
    // Enable timer counter registers for EL1.
    CNTHCTL_EL2.write(CNTHCTL_EL2::EL1PCEN::SET + CNTHCTL_EL2::EL1PCTEN::SET);

    // No offset for reading the counters.
    CNTVOFF_EL2.set(0);

    // Set EL1 execution state to AArch64.
    HCR_EL2.write(HCR_EL2::RW::EL1IsAarch64);

    // Set up a simulated exception return.
    SPSR_EL2.write(
        SPSR_EL2::D::Masked
            + SPSR_EL2::A::Masked
            + SPSR_EL2::I::Masked
            + SPSR_EL2::F::Masked
            + SPSR_EL2::M::EL1h,
    );

Disclaimer

Descriptive comments in the source files are taken from the ARM Architecture Reference Manual ARMv8, for ARMv8-A architecture profile.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.