89 Commits
Author SHA1 Message Date
Gary GuoandMiguel Ojeda 68bf102226 rust: pin-init: fix incorrect accessor reference lifetime
When a field has been initialized, `init!`/`pin_init!` create a reference
or pinned reference to the field so it can be accessed later during the
initialization of other fields. However, the reference it created is
incorrectly `&'static` rather than just the scope of the initializer.

This means that you can do

    init!(Foo {
        a: 1,
        _: {
            let b: &'static u32 = a;
        }
    })

which is unsound.

This is caused by `&mut (*#slot).#ident`, which actually allows arbitrary
lifetime, so this is effectively `'static`. Somewhat ironically, the safety
justification of creating the accessor is.. "SAFETY: TODO".

Fix it by adding `let_binding` method on `DropGuard` to shorten lifetime.
This results in exactly what we want for these accessors. The safety and
invariant comments of `DropGuard` have been reworked; instead of reasoning
about what caller can do with the guard, express it in a way that the
ownership is transferred to the guard and `forget` takes it back, so the
unsafe operations within the `DropGuard` can be more easily justified.

Fixes: 42415d163e ("rust: pin-init: add references to previously initialized fields")
Cc: stable@vger.kernel.org
Signed-off-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260427-pin-init-fix-v3-2-496a699674dd@garyguo.net
[ Reworded for missing word. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2026-04-30 22:43:32 +02:00
Gary GuoandMiguel Ojeda 83ac287031 rust: pin-init: internal: move alignment check to make_field_check
Instead of having the reference creation serving dual-purpose as both for
let bindings and alignment check, detangle them so that the alignment check
is done explicitly in `make_field_check`. This is more robust against
refactors that may change the way let bindings are created.

Cc: stable@vger.kernel.org
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260427-pin-init-fix-v3-1-496a699674dd@garyguo.net
[ Reworded for typo. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2026-04-30 22:43:28 +02:00
Antonio HickeyandBenno Lossin 09808839c7 rust: pin-init: replace addr_of_mut! with &raw mut
`feature(raw_ref_op)` became stable in Rust 1.82.0 which is the current
MSRV of pin-init with no default features. Earlier Rust versions will
now need to enable `raw_ref_op` to continue to work with pin-init.

This reduces visual complexity and improves consistency with existing
reference syntax.

Suggested-by: Benno Lossin <lossin@kernel.org>
Link: https://github.com/Rust-for-Linux/linux/issues/1148
Closes: https://github.com/Rust-for-Linux/pin-init/issues/99
Signed-off-by: Antonio Hickey <contact@antoniohickey.com>
Link: https://github.com/Rust-for-Linux/pin-init/commit/e27763004e2f6616b089437fbe9b3719cd72bd5c
[ Reworded commit message. - Benno ]
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260319093542.3756606-6-lossin@kernel.org
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-03-25 10:57:53 +01:00
Hamdan-KhanandBenno Lossin aa9ec9460d rust: pin-init: implement ZeroableOption for NonZero* integer types
Add a macro for implementing `ZeroableOption` for `NonZero*` types.

`Option<NonZero*>` now automatically implements `Zeroable` trait  by
implementing `ZeroableOption` for `NonZero*` types, which serves as a
blanket impl.

Closes: https://github.com/Rust-for-Linux/pin-init/issues/95
Signed-off-by: Hamdan-Khan <hamdankhan212@gmail.com>
Link: https://github.com/Rust-for-Linux/pin-init/commit/74f772641cd9670848fa360f4ebfd20fdb40bf78
[ Fixed a typo in the commit message. - Benno ]
Link: https://patch.msgid.link/20260319093542.3756606-5-lossin@kernel.org
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-03-25 10:57:33 +01:00
Gary GuoandBenno Lossin 44f6fa0dce rust: pin-init: doc: de-clutter documentation with fake-variadics
Currently the doc for `Zeroable` and `ZeroableOption` are filled with the
generated impl of tuples and fn pointers. Use the internal
"fake_variadics" feature to improve the rendered quality.

This makes use of an internal feature, however this is of minimal risk as
it's for documentation only, not activated during normal build, gated
behind `USE_RUSTC_FEATURES`, and can be removed at any time. This feature
is already used by serde and bevy to improve documentation quality.

For compilers that cannot use this feature, we still hide most generated
impls, and the existence of them are hinted by doc comments on the single
non-hidden impl.

Signed-off-by: Gary Guo <gary@garyguo.net>
Link: https://github.com/Rust-for-Linux/pin-init/commit/530c4eb79a449599e219821f9397f03250cc2aa4
[ Reordered `#[doc]` attributes and safety comments to avoid errors in
  older versions of clippy. - Benno ]
Link: https://patch.msgid.link/20260319093542.3756606-4-lossin@kernel.org
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-03-25 10:57:16 +01:00
Benno Lossin 960c37cbcb rust: pin-init: properly document let binding workaround
The three let bindings (in the bodies of `cast_init`, `cast_pin_init`
and the `init!` macro) are used to avoid the following compiler error in
Rust 1.78.0, 1.79.0, 1.80.0, 1.80.1, and 1.81.0 (just showing the one
for `cast_init`, the others are similar):

    error[E0391]: cycle detected when computing type of opaque `cast_init::{opaque#0}`
        --> src/lib.rs:1160:66
         |
    1160 | pub const unsafe fn cast_init<T, U, E>(init: impl Init<T, E>) -> impl Init<U, E> {
         |                                                                  ^^^^^^^^^^^^^^^
         |
    note: ...which requires borrow-checking `cast_init`...
        --> src/lib.rs:1160:1
         |
    1160 | pub const unsafe fn cast_init<T, U, E>(init: impl Init<T, E>) -> impl Init<U, E> {
         | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    note: ...which requires const checking `cast_init`...
        --> src/lib.rs:1160:1
         |
    1160 | pub const unsafe fn cast_init<T, U, E>(init: impl Init<T, E>) -> impl Init<U, E> {
         | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
         = note: ...which requires computing whether `cast_init::{opaque#0}` is freeze...
         = note: ...which requires evaluating trait selection obligation `cast_init::{opaque#0}: core::marker::Freeze`...
         = note: ...which again requires computing type of opaque `cast_init::{opaque#0}`, completing the cycle
    note: cycle used when computing type of `cast_init::{opaque#0}`
        --> src/lib.rs:1160:66
         |
    1160 | pub const unsafe fn cast_init<T, U, E>(init: impl Init<T, E>) -> impl Init<U, E> {
         |                                                                  ^^^^^^^^^^^^^^^
         = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information

Once we raise the nightly-MSRV above 1.81, we can remove this
workaround.

Link: https://github.com/Rust-for-Linux/pin-init/commit/bb3e96f3e9a4f5fca80a22af883c7e5aa90f0893
[ Moved this commit after the previous one to avoid a build failure due
  to unstable features. Changed the cfg to use `USE_RUSTC_FEAUTURES`.
  - Benno ]
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260319093542.3756606-3-lossin@kernel.org
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-03-25 10:56:53 +01:00
Gary GuoandBenno Lossin 002a121b16 rust: pin-init: build: simplify use of nightly features
We use some features that are already stable in later versions of Rust,
but only available as unstable features in older Rust versions that the
kernel needs to support.

Instead of checking if a feature is already stable, simply enable them
and allow the warning if the feature is already stable. This avoids the
need of hardcoding whether a feature has been stabilized at a given
version.

`#[feature(...)]` is used when cfg `USE_RUSTC_FEATURES` is enabled. The
build script automatically does this when a nightly compiler is detected
or `RUSTC_BOOTSTRAP` is set.

Signed-off-by: Gary Guo <gary@garyguo.net>
Link: https://github.com/Rust-for-Linux/pin-init/commit/885c5d83d7eb778a796d4a17380a0898b0d0a571
[ Added kernel build system changes to always enable USE_RUSTC_FEATURES.
  Moved this commit earlier (swapped with the next one) to avoid a build
  error. - Benno ]
Link: https://patch.msgid.link/20260319093542.3756606-2-lossin@kernel.org
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-03-25 10:56:16 +01:00
Benno LossinandMiguel Ojeda fdbaa9d2b7 rust: pin-init: replace shadowed return token by unsafe-to-create token
We use a unit struct `__InitOk` in the closure generated by the
initializer macros as the return value. We shadow it by creating a
struct with the same name again inside of the closure, preventing early
returns of `Ok` in the initializer (before all fields have been
initialized).

In the face of Type Alias Impl Trait (TAIT) and the next trait solver,
this solution no longer works [1]. The shadowed struct can be named
through type inference. In addition, there is an RFC proposing to add
the feature of path inference to Rust, which would similarly allow [2].

Thus remove the shadowed token and replace it with an `unsafe` to create
token.

The reason we initially used the shadowing solution was because an
alternative solution used a builder pattern. Gary writes [3]:

    In the early builder-pattern based InitOk, having a single InitOk
    type for token is unsound because one can launder an InitOk token
    used for one place to another initializer. I used a branded lifetime
    solution, and then you figured out that using a shadowed type would
    work better because nobody could construct it at all.

The laundering issue does not apply to the approach we ended up with
today.

With this change, the example by Tim Chirananthavat in [1] no longer
compiles and results in this error:

    error: cannot construct `pin_init::__internal::InitOk` with struct literal syntax due to private fields
      --> src/main.rs:26:17
       |
    26 |                 InferredType {}
       |                 ^^^^^^^^^^^^
       |
       = note: private field `0` that was not provided
    help: you might have meant to use the `new` associated function
       |
    26 -                 InferredType {}
    26 +                 InferredType::new()
       |

Applying the suggestion of using the `::new()` function, results in
another expected error:

    error[E0133]: call to unsafe function `pin_init::__internal::InitOk::new` is unsafe and requires unsafe block
      --> src/main.rs:26:17
       |
    26 |                 InferredType::new()
       |                 ^^^^^^^^^^^^^^^^^^^ call to unsafe function
       |
       = note: consult the function's documentation for information on how to avoid undefined behavior

Reported-by: Tim Chirananthavat <theemathas@gmail.com>
Link: https://github.com/rust-lang/rust/issues/153535 [1]
Link: https://github.com/rust-lang/rfcs/pull/3444#issuecomment-4016145373 [2]
Link: https://github.com/rust-lang/rust/issues/153535#issuecomment-4017620804 [3]
Fixes: fc6c6baa1f ("rust: init: add initialization macros")
Cc: stable@vger.kernel.org
Signed-off-by: Benno Lossin <lossin@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260311105056.1425041-1-lossin@kernel.org
[ Added period as mentioned. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2026-03-12 08:46:17 +01:00
Benno LossinandMiguel Ojeda 580cc37b1d rust: pin-init: internal: init: document load-bearing fact of field accessors
The functions `[Pin]Init::__[pinned_]init` and `ptr::write` called from
the `init!` macro require the passed pointer to be aligned. This fact is
ensured by the creation of field accessors to previously initialized
fields.

Since we missed this very important fact from the beginning [1],
document it in the code.

Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1]
Fixes: 90e53c5e70 ("rust: add pin-init API core")
Cc: <stable@vger.kernel.org> # 6.6.y, 6.12.y: 42415d163e: rust: pin-init: add references to previously initialized fields
Cc: <stable@vger.kernel.org> # 6.6.y, 6.12.y, 6.18.y, 6.19.y
Signed-off-by: Benno Lossin <lossin@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260302140424.4097655-2-lossin@kernel.org
[ Updated Cc: stable@ tags as discussed. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2026-03-06 02:05:46 +01:00
Benno LossinandMiguel Ojeda a075082a15 rust: pin-init: internal: init: remove #[disable_initialized_field_access]
Gary noticed [1] that the initializer macros as well as the `[Pin]Init`
traits cannot support unaligned fields, since they use operations that
require aligned pointers. This means that any code using structs with
unaligned fields in pin-init is unsound.

By default, the `init!` macro generates references to initialized fields,
which makes the compiler check that those fields are aligned.  However,
we added the `#[disable_initialized_field_access]` attribute to avoid
this behavior in commit ceca298c53 ("rust: pin-init: internal: init:
add escape hatch for referencing initialized fields"). Thus remove the
`#[disable_initialized_field_access]` attribute from `init!`, which is
the only safe way to create an initializer handling unaligned fields.

If support for in-place initializing structs with unaligned fields is
required in the future, we could figure out a solution. This is tracked
in [2].

Reported-by: Gary Guo <gary@garyguo.net>
Closes: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1]
Link: https://github.com/Rust-for-Linux/pin-init/issues/112 [2]
Fixes: ceca298c53 ("rust: pin-init: internal: init: add escape hatch for referencing initialized fields")
Signed-off-by: Benno Lossin <lossin@kernel.org>
Acked-by: Janne Grunau <j@jannau.net>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260302140424.4097655-1-lossin@kernel.org
[ Adjusted tags and reworded as discussed. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2026-03-06 02:04:09 +01:00
Linus Torvalds 1dd419145d Merge tag 'rust-fixes-7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux
Pull rust fixes from Miguel Ojeda:
 "Toolchain and infrastructure:

   - Pass '-Zunstable-options' flag required by the future Rust 1.95.0

   - Fix 'objtool' warning for Rust 1.84.0

  'kernel' crate:

   - 'irq' module: add missing bound detected by the future Rust 1.95.0

   - 'list' module: add missing 'unsafe' blocks and placeholder safety
     comments to macros (an issue for future callers within the crate)

  'pin-init' crate:

   - Clean Clippy warning that changed behavior in the future Rust
     1.95.0"

* tag 'rust-fixes-7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux:
  rust: list: Add unsafe blocks for container_of and safety comments
  rust: pin-init: replace clippy `expect` with `allow`
  rust: irq: add `'static` bounds to irq callbacks
  objtool/rust: add one more `noreturn` Rust function
  rust: kbuild: pass `-Zunstable-options` for Rust 1.95.0
2026-02-22 08:43:31 -08:00
Benno LossinandMiguel Ojeda a58b8764ae rust: pin-init: replace clippy expect with allow
`clippy` has changed behavior in [1] (Rust 1.95) where it no longer
warns about the `let_and_return` lint when a comment is placed between
the let binding and the return expression. Nightly thus fails to build,
because the expectation is no longer fulfilled.

Thus replace the expectation with an `allow`.

[ The errors were:

      error: this lint expectation is unfulfilled
          --> rust/pin-init/src/lib.rs:1279:10
           |
      1279 | #[expect(clippy::let_and_return)]
           |          ^^^^^^^^^^^^^^^^^^^^^^
           |
           = note: `-D unfulfilled-lint-expectations` implied by `-D warnings`
           = help: to override `-D warnings` add `#[allow(unfulfilled_lint_expectations)]`

      error: this lint expectation is unfulfilled
          --> rust/pin-init/src/lib.rs:1295:10
           |
      1295 | #[expect(clippy::let_and_return)]
           |          ^^^^^^^^^^^^^^^^^^^^^^

    - Miguel ]

Link: https://github.com/rust-lang/rust-clippy/pull/16461 [1]
Signed-off-by: Benno Lossin <lossin@kernel.org>
Cc: stable@vger.kernel.org # Needed in 6.18.y and later.
Link: https://patch.msgid.link/20260215132232.1549861-1-lossin@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2026-02-19 09:33:43 +01:00
Oleksandr BabakandBenno Lossin aeb5ecad53 rust: pin-init: Implement InPlaceWrite<T> for &'static mut MaybeUninit<T>
This feature allows users to use `&'static mut MaybeUninit<T>` as a
place to initialize the value. It mirrors an existing implemetation
for `Box<MaybeUninit>`, but enables users to use external allocation
mechanisms such as `static_cell` [1].

Signed-off-by: Oleksandr Babak <alexanderbabak@proton.me>
Link: https://crates.io/crates/static_cell [1]
[ Added link to `static_cell` - Benno ]
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-01-17 10:53:28 +01:00
Benno Lossin 1f1cd6964b rust: pin-init: internal: init: simplify Zeroable safety check
The `Zeroable` type check uses a small dance with a raw pointer to aid
type inference. It turns out that this is not necessary and type
inference is powerful enough to resolve any ambiguity. Thus remove it.

Suggested-by: Gary Guo <gary@garyguo.net>
Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-01-17 10:51:43 +01:00
Benno Lossin ceca298c53 rust: pin-init: internal: init: add escape hatch for referencing initialized fields
The initializer macro emits mutable references for already initialized
fields, which allows modifying or accessing them later in code blocks or
when initializing other fields. This behavior results in compiler errors
when combining with packed structs, since those do not permit creating
references to misaligned fields. For example:

    #[repr(C, packed)]
    struct Foo {
        a: i8,
        b: i32,
    }

    fn main() {
        let _ = init!(Foo { a: -42, b: 42 });
    }

This will lead to an error like this:

    error[E0793]: reference to field of packed struct is unaligned
      --> tests/ui/compile-fail/init/packed_struct.rs:10:13
       |
    10 |     let _ = init!(Foo { a: -42, b: 42 });
       |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
       |
       = note: this struct is 1-byte aligned, but the type of this field may require higher alignment
       = note: creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
       = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
       = note: this error originates in the macro `init` (in Nightly builds, run with -Z macro-backtrace for more info)

This was requested by Janne Grunau [1] and will most certainly be used
by the kernel when we eventually end up with trying to initialize packed
structs.

Thus add an initializer attribute `#[disable_initialized_field_access]`
that does what the name suggests: do not generate references to already
initialized fields.

There is space for future work: add yet another attribute which can be
applied on fields of initializers that ask for said field to be made
accessible. We can add that when the need arises.

Requested-by: Janne Grunau <j@jannau.net>
Link: https://lore.kernel.org/all/20251206170214.GE1097212@robin.jannau.net [1]
Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-01-17 10:51:43 +01:00
Benno Lossin d26732e57b rust: pin-init: internal: init: add support for attributes on initializer fields
Initializer fields ought to support the same attributes that are allowed
in struct initializers on fields. For example, `cfg` or lint levels such
as `expect`, `allow` etc. Add parsing support for these attributes using
syn to initializer fields and adjust the macro expansion accordingly.

Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-01-17 10:51:42 +01:00
Benno Lossin aeabc92eb2 rust: pin-init: add #[default_error(<type>)] attribute to initializer macros
The `#[default_error(<type>)]` attribute can be used to supply a default
type as the error used for the `[pin_]init!` macros. This way one can
easily define custom `try_[pin_]init!` variants that default to your
project specific error type. Just write the following declarative macro:

    macro_rules! try_init {
        ($($args:tt)*) => {
            ::pin_init::init!(
                #[default_error(YourCustomErrorType)]
                $($args)*
            )
        }
    }

Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-01-17 10:51:42 +01:00
Benno Lossin 4883830e97 rust: pin-init: rewrite the initializer macros using syn
Rewrite the initializer macros `[pin_]init!` using `syn`. No functional
changes intended aside from improved error messages on syntactic and
semantical errors. For example if one forgets to use `<-` with an
initializer (and instead uses `:`):

    impl Bar {
        fn new() -> impl PinInit<Self> { ... }
    }

    impl Foo {
        fn new() -> impl PinInit<Self> {
            pin_init!(Self { bar: Bar::new() })
        }
    }

Then the declarative macro would report:

    error[E0308]: mismatched types
      --> tests/ui/compile-fail/init/colon_instead_of_arrow.rs:21:9
       |
    14 |     fn new() -> impl PinInit<Self> {
       |                 ------------------ the found opaque type
    ...
    21 |         pin_init!(Self { bar: Bar::new() })
       |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
       |         |
       |         expected `Bar`, found opaque type
       |         arguments to this function are incorrect
       |
       = note:   expected struct `Bar`
               found opaque type `impl pin_init::PinInit<Bar>`
    note: function defined here
      --> $RUST/core/src/ptr/mod.rs
       |
       | pub const unsafe fn write<T>(dst: *mut T, src: T) {
       |                     ^^^^^
       = note: this error originates in the macro `$crate::__init_internal` which comes from the expansion of the macro `pin_init` (in Nightly builds, run with -Z macro-backtrace for more info)

And the new error is:

    error[E0308]: mismatched types
      --> tests/ui/compile-fail/init/colon_instead_of_arrow.rs:21:31
       |
    14 |     fn new() -> impl PinInit<Self> {
       |                 ------------------ the found opaque type
    ...
    21 |         pin_init!(Self { bar: Bar::new() })
       |                          ---  ^^^^^^^^^^ expected `Bar`, found opaque type
       |                          |
       |                          arguments to this function are incorrect
       |
       = note:   expected struct `Bar`
               found opaque type `impl pin_init::PinInit<Bar>`
    note: function defined here
      --> $RUST/core/src/ptr/mod.rs
       |
       | pub const unsafe fn write<T>(dst: *mut T, src: T) {
       |                     ^^^^^

Importantly, this error gives much more accurate span locations,
pointing to the offending field, rather than the entire macro
invocation.

Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-01-17 10:51:42 +01:00
Benno Lossin dae5466c4a rust: pin-init: add ?Sized bounds to traits in #[pin_data] macro
The `#[pin_data]` macro uses some auxiliary traits to ensure that a user
does not implement `Drop` for the annotated struct, as that is unsound
and can lead to UB. However, if the struct that is annotated is
`!Sized`, the current bounds do not work, because `Sized` is an implicit
bound for generics.

This is *not* a soundness hole of pin-init, as it currently is
impossible to construct an unsized struct using pin-init.

Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-01-17 10:51:42 +01:00
Benno Lossin 560f6d13c3 rust: pin-init: rewrite #[pin_data] using syn
Rewrite the attribute macro `#[pin_data]` using `syn`. No functional
changes intended aside from improved error messages on syntactic and
semantical errors. For example if one forgets a comma at the end of a
field:

    #[pin_data]
    struct Foo {
        a: Box<Foo>
        b: Box<Foo>
    }

The declarative macro reports the following errors:

    error: expected `,`, or `}`, found `b`
     --> tests/ui/compile-fail/pin_data/missing_comma.rs:5:16
      |
    5 |     a: Box<Foo>
      |                ^ help: try adding a comma: `,`

    error: recursion limit reached while expanding `$crate::__pin_data!`
     --> tests/ui/compile-fail/pin_data/missing_comma.rs:3:1
      |
    3 | #[pin_data]
      | ^^^^^^^^^^^
      |
      = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`$CRATE`)
      = note: this error originates in the macro `$crate::__pin_data` which comes from the expansion of the attribute macro `pin_data` (in Nightly builds, run with -Z macro-backtrace for more info)

The new `syn` version reports:

    error: expected `,`, or `}`, found `b`
     --> tests/ui/compile-fail/pin_data/missing_comma.rs:5:16
      |
    5 |     a: Box<Foo>
      |                ^ help: try adding a comma: `,`

    error: expected `,`
     --> tests/ui/compile-fail/pin_data/missing_comma.rs:6:5
      |
    6 |     b: Box<Foo>
      |     ^

Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-01-17 10:51:42 +01:00
Benno Lossin a92f5fd292 rust: pin-init: rewrite the #[pinned_drop] attribute macro using syn
Rewrite the attribute macro for implementing `PinnedDrop` using `syn`.
Otherwise no functional changes intended aside from improved error
messages on syntactic and semantical errors. For example:

When missing the `drop` function in the implementation, the old error
was:

    error: no rules expected `)`
     --> tests/ui/compile-fail/pinned_drop/no_fn.rs:6:1
      |
    6 | #[pinned_drop]
      | ^^^^^^^^^^^^^^ no rules expected this token in macro call
      |
    note: while trying to match keyword `fn`
     --> src/macros.rs
      |
      |             fn drop($($sig:tt)*) {
      |             ^^
      = note: this error originates in the attribute macro `pinned_drop` (in Nightly builds, run with -Z macro-backtrace for more info)

And the new one is:

    error[E0046]: not all trait items implemented, missing: `drop`
     --> tests/ui/compile-fail/pinned_drop/no_fn.rs:7:1
      |
    7 | impl PinnedDrop for Foo {}
      | ^^^^^^^^^^^^^^^^^^^^^^^ missing `drop` in implementation
      |
      = help: implement the missing item: `fn drop(self: Pin<&mut Self>, _: OnlyCallFromDrop) { todo!() }`

Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-01-17 10:51:42 +01:00
Benno Lossin 50426bde15 rust: pin-init: rewrite derive(Zeroable) and derive(MaybeZeroable) using syn
Rewrite the two derive macros for `Zeroable` using `syn`. One positive
side effect of this change is that tuple structs are now supported by
them. Additionally, syntax errors and the error emitted when trying to
use one of the derive macros on an `enum` are improved. Otherwise no
functional changes intended.

For example:

    #[derive(Zeroable)]
    enum Num {
        A(u32),
        B(i32),
    }

Produced this error before this commit:

    error: no rules expected keyword `enum`
     --> tests/ui/compile-fail/zeroable/enum.rs:5:1
      |
    5 | enum Num {
      | ^^^^ no rules expected this token in macro call
      |
    note: while trying to match keyword `struct`
     --> src/macros.rs
      |
      |             $vis:vis struct $name:ident
      |                      ^^^^^^

Now the error is:

    error: cannot derive `Zeroable` for an enum
     --> tests/ui/compile-fail/zeroable/enum.rs:5:1
      |
    5 | enum Num {
      | ^^^^

    error: cannot derive `Zeroable` for an enum

Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-01-17 10:51:42 +01:00
Benno Lossin 26bd940238 rust: pin-init: internal: add utility API for syn error handling
The API is similar to diagnostics handling in rustc and uses a
`ErrorGuaranteed` value to signify that an error has been emitted. It
supports both fatal errors (which abort the macro expansion immediately
by returning `Err(ErrorGuaranteed)`) and non-fatal ones at generation
time. These errors are appended to the token stream after generation has
finished normally. This allows giving good errors while still expanding
most of the code as expected to avoid the user encountering additional
errors (for example missing definitions).

Suggested-by: Gary Guo <gary@garyguo.net>
Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
[ remove duplicate word in commit message - Benno ]
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-01-17 10:51:21 +01:00
Benno Lossin 514e4ed2c9 rust: pin-init: add syn dependency and remove proc-macro[2] and quote workarounds
`syn` makes parsing Rust from proc-macros a lot simpler. `pin-init` has
not used `syn` up until now, because the we did not support it. That
changed in commit 54e3eae855 ("Merge patch series "`syn` support""),
so we can finally utilize the added ergonomics of parsing proc-macro
input with `syn`.

Previously we only had the `proc-macro` library available, whereas the
user-space version also used `proc-macro2` and `quote`. Now both are
available, so remove the workarounds.

Due to these changes, clippy emits warnings about unnecessary
`.to_string()` as `proc-macro2` provides an additional `PartialEq` impl
on `Ident`, so the warnings are fixed.

[ Adjusted wording from upstream version and added build system changes
  for the kernel - Benno ]

Co-developed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Tamir Duberstein <tamird@gmail.com>
Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-01-17 10:49:31 +01:00
Benno Lossin 901f1d73d2 rust: pin-init: allow the crate to refer to itself as pin-init in doc tests
The `syn` approach requires use of `::pin_init::...` instead of the
`$crate::...` construct available to declarative macros. To be able to
use the `pin_init` crate from itself (which includes doc tests), we have
to declare it as such.

Reviewed-by: Gary Guo <gary@garyguo.net>
Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Benno Lossin <lossin@kernel.org>
2026-01-17 10:49:31 +01:00