| Functions marked as `cmse-nonsecure-call` place restrictions on their |
| inputs and outputs. |
| |
| - inputs must fit in the 4 available 32-bit argument registers. Alignment |
| is relevant. |
| - outputs must either fit in 4 bytes, or be a foundational type of |
| size 8 (`i64`, `u64`, `f64`). |
| - no generics can be used in the signature |
| |
| For more information, |
| see [arm's aapcs32](https://github.com/ARM-software/abi-aa/releases). |
| |
| Erroneous code example: |
| |
| ```ignore (host errors will not match for target) |
| #![feature(abi_cmse_nonsecure_call)] |
| |
| #[no_mangle] |
| pub fn test( |
| f: extern "cmse-nonsecure-call" fn(u32, u32, u32, u32, u32) -> u32, |
| ) -> u32 { |
| f(1, 2, 3, 4, 5) |
| } |
| ``` |
| |
| Arguments' alignment is respected. In the example below, padding is inserted |
| so that the `u64` argument is passed in registers r2 and r3. There is then no |
| room left for the final `f32` argument |
| |
| ```ignore (host errors will not match for target) |
| #![feature(abi_cmse_nonsecure_call)] |
| |
| #[no_mangle] |
| pub fn test( |
| f: extern "cmse-nonsecure-call" fn(u32, u64, f32) -> u32, |
| ) -> u32 { |
| f(1, 2, 3.0) |
| } |
| ``` |
