linux-toradex.git/rust/kernel/error.rs, branch v6.14-rc2

rust: error: import `kernel`'s `LayoutError` instead of `core`'s

2025-01-13T22:45:13+00:00

Import the internal (`kernel::alloc`) version of `LayoutError` instead
of the `core::alloc` one.

In particular, this results in switching the type in the existing
`From for Error` implementation.

Acked-by: Danilo Krummrich 
Signed-off-by: Jimmy Ostler 
Link: https://lore.kernel.org/r/fe58a02189e8804a9eabdd01cb1927d4c491d79c.1734674670.git.jtostler1@gmail.com
[ Reworded commit. - Miguel ]
Signed-off-by: Miguel Ojeda

rust: error: modify `from_errno` to use `try_from_errno`

2024-12-17T22:52:06+00:00

Modify the from_errno function to use try_from_errno to
reduce code duplication while still maintaining all existing
behavior and error handling and also reduces unsafe code.

Link: https://github.com/Rust-for-Linux/linux/issues/1125
Suggested-by: Miguel Ojeda 
Co-developed-by: Guilherme Augusto Martins da Silva 
Signed-off-by: Guilherme Augusto Martins da Silva 
Signed-off-by: Daniel Sedlak 
Reviewed-by: Fiona Behrens 
Link: https://lore.kernel.org/r/20241207112445.55502-1-daniel@sedlak.dev
Signed-off-by: Miguel Ojeda

rust: map `long` to `isize` and `char` to `u8`

2024-12-16T20:49:33+00:00

The following FFI types are replaced compared to `core::ffi`:

1. `char` type is now always mapped to `u8`, since kernel uses
   `-funsigned-char` on the C code. `core::ffi` maps it to platform
   default ABI, which can be either signed or unsigned.

2. `long` is now always mapped to `isize`. It's very common in the
   kernel to use `long` to represent a pointer-sized integer, and in
   fact `intptr_t` is a typedef of `long` in the kernel. Enforce this
   mapping rather than mapping to `i32/i64` depending on platform can
   save us a lot of unnecessary casts.

Signed-off-by: Gary Guo 
Reviewed-by: Alice Ryhl 
Link: https://lore.kernel.org/r/20240913213041.395655-5-gary@garyguo.net
[ Moved `uaccess` changes from the next commit, since they were
  irrefutable patterns that Rust >= 1.82.0 warns about. Reworded
  slightly and reformatted a few documentation comments. Rebased on
  top of `rust-next`. Added the removal of two casts to avoid Clippy
  warnings. - Miguel ]
Signed-off-by: Miguel Ojeda

rust: use custom FFI integer types

2024-11-10T22:58:00+00:00

Currently FFI integer types are defined in libcore. This commit creates
the `ffi` crate and asks bindgen to use that crate for FFI integer types
instead of `core::ffi`.

This commit is preparatory and no type changes are made in this commit
yet.

Signed-off-by: Gary Guo 
Link: https://lore.kernel.org/r/20240913213041.395655-4-gary@garyguo.net
[ Added `rustdoc`, `rusttest` and KUnit tests support. Rebased on top of
  `rust-next` (e.g. migrated more `core::ffi` cases). Reworded crate
  docs slightly and formatted. - Miguel ]
Signed-off-by: Miguel Ojeda

rust: error: check for config `test` in `Error::name`

2024-10-15T21:10:32+00:00

Additional to `testlib` also check for `test` in `Error::name`. This is
required by a subsequent patch that (indirectly) uses `Error` in test
cases.

Reviewed-by: Alice Ryhl 
Reviewed-by: Benno Lossin 
Reviewed-by: Gary Guo 
Signed-off-by: Danilo Krummrich 
Link: https://lore.kernel.org/r/20241004154149.93856-24-dakr@kernel.org
Signed-off-by: Miguel Ojeda

rust: error: use `core::alloc::LayoutError`

2024-10-15T21:10:32+00:00

Use `core::alloc::LayoutError` instead of `alloc::alloc::LayoutError` in
preparation to get rid of Rust's alloc crate.

Reviewed-by: Alice Ryhl 
Reviewed-by: Benno Lossin 
Reviewed-by: Gary Guo 
Signed-off-by: Danilo Krummrich 
Link: https://lore.kernel.org/r/20241004154149.93856-23-dakr@kernel.org
Signed-off-by: Miguel Ojeda

rust: error: optimize error type to use nonzero

2024-10-09T22:33:42+00:00

Optimize `Result<(), Error>` size by changing `Error` type to
`NonZero*` for niche optimization.

This reduces the space used by the `Result` type, as the `NonZero*`
type enables the compiler to apply more efficient memory layout.
For example, the `Result<(), Error>` changes size from 8 to 4 bytes.

Link: https://github.com/Rust-for-Linux/linux/issues/1120
Signed-off-by: Filipe Xavier 
Reviewed-by: Gary Guo 
Reviewed-by: Alice Ryhl 
Reviewed-by: Fiona Behrens 
Link: https://lore.kernel.org/r/BL0PR02MB4914B9B088865CF237731207E9732@BL0PR02MB4914.namprd02.prod.outlook.com
[ Removed unneeded block around `match`, added backticks in panic
  message and added intra-doc link. - Miguel ]
Signed-off-by: Miguel Ojeda

rust: error: make conversion functions public

2024-10-07T19:39:57+00:00

Change visibility to public of functions in error.rs:
from_err_ptr, from_errno, from_result and to_ptr.
Additionally, remove dead_code annotations.

Link: https://github.com/Rust-for-Linux/linux/issues/1105
Reviewed-by: Alice Ryhl 
Signed-off-by: Filipe Xavier 
Reviewed-by: Benno Lossin 
Reviewed-by: Gary Guo 
Link: https://lore.kernel.org/r/DM4PR14MB7276E6948E67B3B23D8EA847E9652@DM4PR14MB7276.namprd14.prod.outlook.com
Signed-off-by: Miguel Ojeda

rust: start using the `#[expect(...)]` attribute

2024-10-07T19:39:57+00:00

In Rust, it is possible to `allow` particular warnings (diagnostics,
lints) locally, making the compiler ignore instances of a given warning
within a given function, module, block, etc.

It is similar to `#pragma GCC diagnostic push` + `ignored` + `pop` in C:

    #pragma GCC diagnostic push
    #pragma GCC diagnostic ignored "-Wunused-function"
    static void f(void) {}
    #pragma GCC diagnostic pop

But way less verbose:

    #[allow(dead_code)]
    fn f() {}

By that virtue, it makes it possible to comfortably enable more
diagnostics by default (i.e. outside `W=` levels) that may have some
false positives but that are otherwise quite useful to keep enabled to
catch potential mistakes.

The `#[expect(...)]` attribute [1] takes this further, and makes the
compiler warn if the diagnostic was _not_ produced. For instance, the
following will ensure that, when `f()` is called somewhere, we will have
to remove the attribute:

    #[expect(dead_code)]
    fn f() {}

If we do not, we get a warning from the compiler:

    warning: this lint expectation is unfulfilled
     --> x.rs:3:10
      |
    3 | #[expect(dead_code)]
      |          ^^^^^^^^^
      |
      = note: `#[warn(unfulfilled_lint_expectations)]` on by default

This means that `expect`s do not get forgotten when they are not needed.

See the next commit for more details, nuances on its usage and
documentation on the feature.

The attribute requires the `lint_reasons` [2] unstable feature, but it
is becoming stable in 1.81.0 (to be released on 2024-09-05) and it has
already been useful to clean things up in this patch series, finding
cases where the `allow`s should not have been there.

Thus, enable `lint_reasons` and convert some of our `allow`s to `expect`s
where possible.

This feature was also an example of the ongoing collaboration between
Rust and the kernel -- we tested it in the kernel early on and found an
issue that was quickly resolved [3].

Cc: Fridtjof Stoldt 
Cc: Urgau 
Link: https://rust-lang.github.io/rfcs/2383-lint-reasons.html#expect-lint-attribute [1]
Link: https://github.com/rust-lang/rust/issues/54503 [2]
Link: https://github.com/rust-lang/rust/issues/114557 [3]
Reviewed-by: Alice Ryhl 
Reviewed-by: Trevor Gross 
Tested-by: Gary Guo 
Reviewed-by: Gary Guo 
Link: https://lore.kernel.org/r/20240904204347.168520-18-ojeda@kernel.org
Signed-off-by: Miguel Ojeda

rust: enable `clippy::undocumented_unsafe_blocks` lint

2024-10-07T19:39:05+00:00

Checking that we are not missing any `// SAFETY` comments in our `unsafe`
blocks is something we have wanted to do for a long time, as well as
cleaning up the remaining cases that were not documented [1].

Back when Rust for Linux started, this was something that could have
been done via a script, like Rust's `tidy`. Soon after, in Rust 1.58.0,
Clippy implemented the `undocumented_unsafe_blocks` lint [2].

Even though the lint has a few false positives, e.g. in some cases where
attributes appear between the comment and the `unsafe` block [3], there
are workarounds and the lint seems quite usable already.

Thus enable the lint now.

We still have a few cases to clean up, so just allow those for the moment
by writing a `TODO` comment -- some of those may be good candidates for
new contributors.

Link: https://github.com/Rust-for-Linux/linux/issues/351 [1]
Link: https://rust-lang.github.io/rust-clippy/master/#/undocumented_unsafe_blocks [2]
Link: https://github.com/rust-lang/rust-clippy/issues/13189 [3]
Reviewed-by: Alice Ryhl 
Reviewed-by: Trevor Gross 
Tested-by: Gary Guo 
Reviewed-by: Gary Guo 
Link: https://lore.kernel.org/r/20240904204347.168520-5-ojeda@kernel.org
Signed-off-by: Miguel Ojeda