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[](https://crates.io/crates/cortex-a)
[](https://crates.io/crates/cortex-a)
# 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](src/registers) (as provided by
`cortex_a::registers::*`), you need to also include
[`tock-registers`](https://crates.io/crates/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`](Cargo.toml).
```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.
```rust
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](https://static.docs.arm.com/ddi0487/ca/DDI0487C_a_armv8_arm.pdf?_ga=2.266626254.1122218691.1534883460-1326731866.1530967873).
## License
Licensed under either of
- Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
http://www.apache.org/licenses/LICENSE-2.0)
- MIT License ([LICENSE-MIT](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.
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