Understanding Rust Error E0775

Overview of Error E0775

Rust Error E0775 occurs when the #[cmse_nonsecure_entry] attribute is used, but the target platform does not support the TrustZone-M extension. The TrustZone-M extension is required for cmse_nonsecure_entry to be a valid attribute.

Erroneous Code Example

#![allow(unused)]
#![feature(cmse_nonsecure_entry)]

fn main() {
#[cmse_nonsecure_entry]
pub extern "C" fn entry_function() {}
}

Resolving Error E0775

To resolve this error, compile your Rust code for a target that supports the TrustZone-M extension. The currently supported targets are: thumbv8m.main-none-eabi, thumbv8m.main-none-eabihf, and thumbv8m.base-none-eabi.

Specifying a Target with Rust Flags

You can specify a target for Rust using the --target flag when compiling with rustc or cargo. For example, you can build with the thumbv8m.base-none-eabi target by running:

rustc --target thumbv8m.base-none-eabi my_source_code.rs

Or, when using Cargo:

cargo build --target thumbv8m.base-none-eabi

Verifying Your Target Support

Ensure that the target platform being used satisfies the requirements for TrustZone-M by either referring to the documentation of a specific platform or checking the platform's cargo config.

For example, here is how you would verify the thumbv8m.main-none-eabi target is supported in your Cargo config:

[build]
target = "thumbv8m.main-none-eabi"