linux.git/rust/kernel/num.rs, branch v7.3-rc3

rust: num: seal Integer

2026-09-06T01:44:00+00:00

Bounded relies on Integer implementations to describe primitive integer
semantics correctly. In particular, it uses Integer::BITS and Signedness
to justify unchecked operations.

Integer is currently safe and externally implementable, so an
implementation can violate those assumptions and make safe Bounded
operations reach undefined behavior.

For example, an Integer implementation for a u8 wrapper can report
BITS = 16. Safe code can then cast a Bounded containing 256
to that wrapper. Its TryFrom implementation returns Err, and
Bounded::cast() calls unwrap_unchecked() on it, causing undefined
behavior.

Seal Integer so only the primitive implementations provided by the
kernel crate can satisfy it.

Fixes: 01e345e82ec3 ("rust: num: add Bounded integer wrapping type")
Reported-by: Miguel Ojeda 
Closes: https://lore.kernel.org/rust-for-linux/CANiq72mOfR33s4y+Ueivd5NrC5yre+Pcp57ZOBz0msw9A4AP1Q@mail.gmail.com/
Cc: stable@vger.kernel.org
Suggested-by: Miguel Ojeda 
Signed-off-by: Younes Akhouayri 
Acked-by: Alexandre Courbot 
Link: https://patch.msgid.link/20260905-feature-rust-num-seal-integer-v2-1-f1311ffbe6e7@younes.io
Signed-off-by: Miguel Ojeda

rust: add functions and traits for lossless integer conversions

2026-08-13T11:41:28+00:00

The core library's `From` implementations do not cover conversions that
are not portable or future-proof. For instance, even though it is safe
today, `From` is not implemented for `u64` because of the
possibility of supporting larger-than-64bit architectures in the future.

However, the kernel supports a narrower set of architectures, with a
considerable amount of code that is architecture-specific. This makes it
helpful and desirable to provide more infallible conversions, lest we
rely on the `as` keyword and carry the risk of silently losing data.

Thus, introduce a new module `num::casts` that provides safe const
functions performing more conversions allowed by the build target, as
well as `FromSafeCast` and `IntoSafeCast` traits that are just
extensions of `From` and `Into` to conversions that are known to be
lossless.

Some conversions are architecture-specific: for instance, converting a
`u64` to a `usize` is only lossless on 64-bit platforms. These
conversions are made available via a dedicated `arch` sub-module.

Suggested-by: Danilo Krummrich 
Link: https://lore.kernel.org/rust-for-linux/DDK4KADWJHMG.1FUPL3SDR26XF@kernel.org/
Signed-off-by: Alexandre Courbot 
Reviewed-by: Danilo Krummrich 
Link: https://patch.msgid.link/20260806-as_casts-v2-1-cb76a4d3a6ef@nvidia.com
[ Added a few more intra-doc links. - Miguel ]
Signed-off-by: Miguel Ojeda

rust: num: add Bounded integer wrapping type

2025-11-18T23:22:24+00:00

Add the `Bounded` integer wrapper type, which restricts the number of
bits allowed to represent of value.

This is useful to e.g. enforce guarantees when working with bitfields
that have an arbitrary number of bits.

Alongside this type, provide many `From` and `TryFrom` implementations
are to reduce friction when using with regular integer types. Proxy
implementations of common integer operations are also provided.

Signed-off-by: Alexandre Courbot 
Reviewed-by: Alice Ryhl 
Link: https://patch.msgid.link/20251108-bounded_ints-v4-2-c9342ac7ebd1@nvidia.com
[ Added intra-doc link. Fixed a few other nits. - Miguel ]
Signed-off-by: Miguel Ojeda

rust: add num module and Integer trait

2025-11-17T21:56:23+00:00

Introduce the `num` module, which will provide numerical extensions and
utilities for the kernel.

For now, introduce the `Integer` trait, which is implemented for all
primitive integer types to provides their core properties to generic
code.

Signed-off-by: Alexandre Courbot 
Reviewed-by: Alice Ryhl 
Link: https://patch.msgid.link/20251108-bounded_ints-v4-1-c9342ac7ebd1@nvidia.com
Signed-off-by: Miguel Ojeda