On Fri, Aug 15, 2025 at 09:30:41AM +0200, Andreas Hindborg wrote:
> Add a convenience function to convert byte slices to boolean values by
> wrapping them in a null-terminated C string and delegating to the
> existing `kstrtobool` function. Only considers the first two bytes of
> the input slice, following the kernel's boolean parsing semantics.
>
> Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
> ---
> rust/kernel/str.rs | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
> index 5611f7846dc0..ced1cb639efc 100644
> --- a/rust/kernel/str.rs
> +++ b/rust/kernel/str.rs
> @@ -978,6 +978,16 @@ pub fn kstrtobool(string: &CStr) -> Result<bool> {
> kernel::error::to_result(ret).map(|()| result)
> }
>
> +/// Convert `&[u8]` to `bool` by deferring to [`kernel::str::kstrtobool`].
> +///
> +/// Only considers at most the first two bytes of `bytes`.
> +pub fn bytes_to_bool(bytes: &[u8]) -> Result<bool> {
> + // `ktostrbool` only considers the first two bytes of the input.
> + let nbuffer = [*bytes.first().unwrap_or(&0), *bytes.get(1).unwrap_or(&0), 0];
> + let c_str = CStr::from_bytes_with_nul(nbuffer.split_inclusive(|c| *c == 0).next().unwrap())?;
> + kstrtobool(c_str)
> +}
Ouch. That's unpleasant. I would probably suggest this instead to avoid
the length computation:
/// # Safety
/// `string` is a readable NUL-terminated string
unsafe fn kstrtobool_raw(string: *const c_char) -> Result<bool> {
let mut result: bool = false;
let ret = unsafe { bindings::kstrtobool(string, &raw mut result) };
kernel::error::to_result(ret).map(|()| result)
}
pub fn kstrtobool(string: &CStr) -> Result<bool> {
// SAFETY: Caller ensures that `string` is NUL-terminated.
unsafe { kstrtobool_cstr(string.as_char_ptr()) }
}
pub fn kstrtobool_bytes(string: &[u8]) -> Result<bool> {
let mut stack_string = [0u8; 3];
if let Some(first) = string.get(0) {
stack_string[0] = *first;
}
if let Some(second) = string.get(1) {
stack_string[1] = *second;
}
// SAFETY: stack_string[2] is zero, so the string is NUL-terminated.
unsafe { kstrtobool_cstr(stack_string.as_ptr()) }
}
Alice
