From: Benno Lossin <benno.lossin@proton.me>
To: Alice Ryhl <aliceryhl@google.com>,
Miguel Ojeda <ojeda@kernel.org>,
Matthew Wilcox <willy@infradead.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Kees Cook <keescook@chromium.org>
Cc: "Alex Gaynor" <alex.gaynor@gmail.com>,
"Wedson Almeida Filho" <wedsonaf@gmail.com>,
"Boqun Feng" <boqun.feng@gmail.com>,
"Gary Guo" <gary@garyguo.net>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Andreas Hindborg" <a.hindborg@samsung.com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Arve Hjønnevåg" <arve@android.com>,
"Todd Kjos" <tkjos@android.com>,
"Martijn Coenen" <maco@android.com>,
"Joel Fernandes" <joel@joelfernandes.org>,
"Carlos Llamas" <cmllamas@google.com>,
"Suren Baghdasaryan" <surenb@google.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Trevor Gross" <tmgross@umich.edu>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
rust-for-linux@vger.kernel.org,
"Christian Brauner" <brauner@kernel.org>
Subject: Re: [PATCH v6 3/4] rust: uaccess: add typed accessors for userspace pointers
Date: Thu, 18 Apr 2024 13:01:20 +0000 [thread overview]
Message-ID: <5fd684d8-d46d-4009-bcf8-134dab342322@proton.me> (raw)
In-Reply-To: <20240418-alice-mm-v6-3-cb8f3e5d688f@google.com>
On 18.04.24 10:59, Alice Ryhl wrote:
> diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
> index 8fad61268465..9c57c6c75553 100644
> --- a/rust/kernel/types.rs
> +++ b/rust/kernel/types.rs
> @@ -409,3 +409,67 @@ pub enum Either<L, R> {
> /// Constructs an instance of [`Either`] containing a value of type `R`.
> Right(R),
> }
> +
> +/// Types for which any bit pattern is valid.
> +///
> +/// Not all types are valid for all values. For example, a `bool` must be either zero or one, so
> +/// reading arbitrary bytes into something that contains a `bool` is not okay.
> +///
> +/// It's okay for the type to have padding, as initializing those bytes has no effect.
> +///
> +/// # Safety
> +///
> +/// All bit-patterns must be valid for this type. This type must not have interior mutability.
What is the reason for disallowing interior mutability here? I agree
that it is necessary for `AsBytes`, but I don't think we need it here.
For example it is fine to convert `u8` to `UnsafeCell<u8>`. Niches also
should not be a problem, since eg `Option<UnsafeCell<NonNull<u8>>>`
already fails the "All bit-patterns must be valid for this type".
--
Cheers,
Benno
> +pub unsafe trait FromBytes {}
> +
> +// SAFETY: All bit patterns are acceptable values of the types below.
> +unsafe impl FromBytes for u8 {}
> +unsafe impl FromBytes for u16 {}
> +unsafe impl FromBytes for u32 {}
> +unsafe impl FromBytes for u64 {}
> +unsafe impl FromBytes for usize {}
> +unsafe impl FromBytes for i8 {}
> +unsafe impl FromBytes for i16 {}
> +unsafe impl FromBytes for i32 {}
> +unsafe impl FromBytes for i64 {}
> +unsafe impl FromBytes for isize {}
next prev parent reply other threads:[~2024-04-18 13:02 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-18 8:59 [PATCH v6 0/4] Memory management patches needed by Rust Binder Alice Ryhl
2024-04-18 8:59 ` [PATCH v6 1/4] rust: uaccess: add userspace pointers Alice Ryhl
2024-04-19 17:11 ` Boqun Feng
2024-04-19 18:12 ` Alice Ryhl
2024-04-18 8:59 ` [PATCH v6 2/4] uaccess: always export _copy_[from|to]_user with CONFIG_RUST Alice Ryhl
2024-05-14 17:27 ` Andrew Morton
2024-05-15 7:34 ` Arnd Bergmann
2024-04-18 8:59 ` [PATCH v6 3/4] rust: uaccess: add typed accessors for userspace pointers Alice Ryhl
2024-04-18 13:01 ` Benno Lossin [this message]
2024-04-18 13:17 ` Alice Ryhl
2024-04-18 16:23 ` Benno Lossin
2024-04-18 17:19 ` Boqun Feng
2024-04-18 19:35 ` Alice Ryhl
2024-04-18 20:01 ` Boqun Feng
2024-04-18 17:52 ` Trevor Gross
2024-04-25 16:13 ` Gary Guo
2024-04-26 7:13 ` Alice Ryhl
2024-04-18 8:59 ` [PATCH v6 4/4] rust: add abstraction for `struct page` Alice Ryhl
2024-04-18 18:52 ` Boqun Feng
2024-04-18 22:08 ` Benno Lossin
2024-04-18 22:56 ` Boqun Feng
2024-04-18 23:04 ` Boqun Feng
2024-04-19 8:36 ` Benno Lossin
2024-04-19 17:23 ` Boqun Feng
2024-04-19 19:24 ` Benno Lossin
2024-04-19 19:35 ` Boqun Feng
2024-04-25 16:20 ` Gary Guo
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