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SubjectRe: [PATCH v6 1/4] rust: uaccess: add userspace pointers
On Fri, Apr 19, 2024 at 7:11 PM Boqun Feng <boqun.feng@gmail.com> wrote:
>
> On Thu, Apr 18, 2024 at 08:59:17AM +0000, Alice Ryhl wrote:
> [...]
> > + /// Reads the entirety of the user slice, appending it to the end of the provided buffer.
> > + ///
> > + /// Fails with `EFAULT` if the read happens on a bad address.
> > + pub fn read_all(mut self, buf: &mut Vec<u8>, flags: Flags) -> Result {
> > + let len = self.length;
> > + buf.reserve(len, flags)?;
>
> (Reportedy by Miguel)
>
> When compile with `make rusttest`, kernel crate is compiled as userspace
> program, so we need to explicitly pick where the `reserve` comes from
> (Vec or VecExt), the current version will hit the following error:
>
> error[E0061]: this method takes 1 argument but 2 arguments were supplied
> --> rust/kernel/uaccess.rs:296:13
> |
> 296 | buf.reserve(len, flags)?;
> | ^^^^^^^ -------
> | | |
> | | unexpected argument of type `Flags`
> | help: remove the extra argument
> |
> note: method defined here
> --> /home/boqun/linux-rust/rust/test/sysroot/lib/rustlib/src/rust/library/alloc/src/vec/mod.rs:910:12
> |
> 910 | pub fn reserve(&mut self, additional: usize) {
> | ^^^^^^^
>
> error[E0277]: the `?` operator can only be applied to values that implement `Try`
> --> rust/kernel/uaccess.rs:296:9
> |
> 296 | buf.reserve(len, flags)?;
> | ^^^^^^^^^^^^^^^^^^^^^^^^ the `?` operator cannot be applied to type `()`
> |
> = help: the trait `Try` is not implemented for `()`
>
> error: aborting due to 2 previous errors
>
> Some errors have detailed explanations: E0061, E0277.
> For more information about an error, try `rustc --explain E0061`.
>
> and we need to the following fix
>
> diff --git a/rust/kernel/uaccess.rs b/rust/kernel/uaccess.rs
> index 39481e374c40..80f7e7ca2f5e 100644
> --- a/rust/kernel/uaccess.rs
> +++ b/rust/kernel/uaccess.rs
> @@ -293,7 +293,7 @@ pub fn read<T: FromBytes>(&mut self) -> Result<T> {
> /// Fails with `EFAULT` if the read happens on a bad address.
> pub fn read_all(mut self, buf: &mut Vec<u8>, flags: Flags) -> Result {
> let len = self.length;
> - buf.reserve(len, flags)?;
> + VecExt::<u8>::reserve(buf, len, flags)?;
>
> // The call to `try_reserve` was successful, so the spare capacity is at least `len` bytes
> // long.

I'm sorry, what? This seems like a problem with `make rusttest`.

Alice

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