diff options
Diffstat (limited to 'rust/kernel/init/macros.rs')
| -rw-r--r-- | rust/kernel/init/macros.rs | 237 |
1 files changed, 235 insertions, 2 deletions
diff --git a/rust/kernel/init/macros.rs b/rust/kernel/init/macros.rs index 00aa4e956c0a..ad78dd0d9d9e 100644 --- a/rust/kernel/init/macros.rs +++ b/rust/kernel/init/macros.rs @@ -1,10 +1,12 @@ // SPDX-License-Identifier: Apache-2.0 OR MIT //! This module provides the macros that actually implement the proc-macros `pin_data` and -//! `pinned_drop`. +//! `pinned_drop`. It also contains `__init_internal` the implementation of the `{try_}{pin_}init!` +//! macros. //! //! These macros should never be called directly, since they expect their input to be -//! in a certain format which is internal. Use the proc-macros instead. +//! in a certain format which is internal. If used incorrectly, these macros can lead to UB even in +//! safe code! Use the public facing macros instead. //! //! This architecture has been chosen because the kernel does not yet have access to `syn` which //! would make matters a lot easier for implementing these as proc-macros. @@ -980,3 +982,234 @@ macro_rules! __pin_data { } }; } + +/// The internal init macro. Do not call manually! +/// +/// This is called by the `{try_}{pin_}init!` macros with various inputs. +/// +/// This macro has multiple internal call configurations, these are always the very first ident: +/// - nothing: this is the base case and called by the `{try_}{pin_}init!` macros. +/// - `init_slot`: recursively creates the code that initializes all fields in `slot`. +/// - `make_initializer`: recursively create the struct initializer that guarantees that every +/// field has been initialized exactly once. +/// - `forget_guards`: recursively forget the drop guards for every field. +#[doc(hidden)] +#[macro_export] +macro_rules! __init_internal { + ( + @this($($this:ident)?), + @typ($t:ident $(::<$($generics:ty),*>)?), + @fields($($fields:tt)*), + @error($err:ty), + // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData` + // case. + @data($data:ident, $($use_data:ident)?), + // `HasPinData` or `HasInitData`. + @has_data($has_data:ident, $get_data:ident), + // `pin_init_from_closure` or `init_from_closure`. + @construct_closure($construct_closure:ident), + ) => {{ + // We do not want to allow arbitrary returns, so we declare this type as the `Ok` return + // type and shadow it later when we insert the arbitrary user code. That way there will be + // no possibility of returning without `unsafe`. + struct __InitOk; + // Get the data about fields from the supplied type. + let data = unsafe { + use $crate::init::__internal::$has_data; + $t$(::<$($generics),*>)?::$get_data() + }; + // Ensure that `data` really is of type `$data` and help with type inference: + let init = $crate::init::__internal::$data::make_closure::<_, __InitOk, $err>( + data, + move |slot| { + { + // Shadow the structure so it cannot be used to return early. + struct __InitOk; + // Create the `this` so it can be referenced by the user inside of the + // expressions creating the individual fields. + $(let $this = unsafe { ::core::ptr::NonNull::new_unchecked(slot) };)? + // Initialize every field. + $crate::__init_internal!(init_slot($($use_data)?): + @data(data), + @slot(slot), + @munch_fields($($fields)*,), + ); + // We use unreachable code to ensure that all fields have been mentioned exactly + // once, this struct initializer will still be type-checked and complain with a + // very natural error message if a field is forgotten/mentioned more than once. + #[allow(unreachable_code, clippy::diverging_sub_expression)] + if false { + $crate::__init_internal!(make_initializer: + @slot(slot), + @type_name($t), + @munch_fields($($fields)*,), + @acc(), + ); + } + // Forget all guards, since initialization was a success. + $crate::__init_internal!(forget_guards: + @munch_fields($($fields)*,), + ); + } + Ok(__InitOk) + } + ); + let init = move |slot| -> ::core::result::Result<(), $err> { + init(slot).map(|__InitOk| ()) + }; + let init = unsafe { $crate::init::$construct_closure::<_, $err>(init) }; + init + }}; + (init_slot($($use_data:ident)?): + @data($data:ident), + @slot($slot:ident), + @munch_fields($(,)?), + ) => { + // Endpoint of munching, no fields are left. + }; + (init_slot($use_data:ident): // `use_data` is present, so we use the `data` to init fields. + @data($data:ident), + @slot($slot:ident), + // In-place initialization syntax. + @munch_fields($field:ident <- $val:expr, $($rest:tt)*), + ) => { + let $field = $val; + // Call the initializer. + // + // SAFETY: `slot` is valid, because we are inside of an initializer closure, we + // return when an error/panic occurs. + // We also use the `data` to require the correct trait (`Init` or `PinInit`) for `$field`. + unsafe { $data.$field(::core::ptr::addr_of_mut!((*$slot).$field), $field)? }; + // Create the drop guard. + // + // We only give access to `&DropGuard`, so it cannot be forgotten via safe code. + // + // SAFETY: We forget the guard later when initialization has succeeded. + let $field = &unsafe { + $crate::init::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field)) + }; + + $crate::__init_internal!(init_slot($use_data): + @data($data), + @slot($slot), + @munch_fields($($rest)*), + ); + }; + (init_slot(): // No `use_data`, so we use `Init::__init` directly. + @data($data:ident), + @slot($slot:ident), + // In-place initialization syntax. + @munch_fields($field:ident <- $val:expr, $($rest:tt)*), + ) => { + let $field = $val; + // Call the initializer. + // + // SAFETY: `slot` is valid, because we are inside of an initializer closure, we + // return when an error/panic occurs. + unsafe { $crate::init::Init::__init($field, ::core::ptr::addr_of_mut!((*$slot).$field))? }; + // Create the drop guard. + // + // We only give access to `&DropGuard`, so it cannot be forgotten via safe code. + // + // SAFETY: We forget the guard later when initialization has succeeded. + let $field = &unsafe { + $crate::init::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field)) + }; + + $crate::__init_internal!(init_slot(): + @data($data), + @slot($slot), + @munch_fields($($rest)*), + ); + }; + (init_slot($($use_data:ident)?): + @data($data:ident), + @slot($slot:ident), + // Init by-value. + @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), + ) => { + $(let $field = $val;)? + // Initialize the field. + // + // SAFETY: The memory at `slot` is uninitialized. + unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) }; + // Create the drop guard: + // + // We only give access to `&DropGuard`, so it cannot be accidentally forgotten. + // + // SAFETY: We forget the guard later when initialization has succeeded. + let $field = &unsafe { + $crate::init::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field)) + }; + + $crate::__init_internal!(init_slot($($use_data)?): + @data($data), + @slot($slot), + @munch_fields($($rest)*), + ); + }; + (make_initializer: + @slot($slot:ident), + @type_name($t:ident), + @munch_fields($(,)?), + @acc($($acc:tt)*), + ) => { + // Endpoint, nothing more to munch, create the initializer. + // Since we are in the `if false` branch, this will never get executed. We abuse `slot` to + // get the correct type inference here: + unsafe { + ::core::ptr::write($slot, $t { + $($acc)* + }); + } + }; + (make_initializer: + @slot($slot:ident), + @type_name($t:ident), + @munch_fields($field:ident <- $val:expr, $($rest:tt)*), + @acc($($acc:tt)*), + ) => { + $crate::__init_internal!(make_initializer: + @slot($slot), + @type_name($t), + @munch_fields($($rest)*), + @acc($($acc)* $field: ::core::panic!(),), + ); + }; + (make_initializer: + @slot($slot:ident), + @type_name($t:ident), + @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), + @acc($($acc:tt)*), + ) => { + $crate::__init_internal!(make_initializer: + @slot($slot), + @type_name($t), + @munch_fields($($rest)*), + @acc($($acc)* $field: ::core::panic!(),), + ); + }; + (forget_guards: + @munch_fields($(,)?), + ) => { + // Munching finished. + }; + (forget_guards: + @munch_fields($field:ident <- $val:expr, $($rest:tt)*), + ) => { + unsafe { $crate::init::__internal::DropGuard::forget($field) }; + + $crate::__init_internal!(forget_guards: + @munch_fields($($rest)*), + ); + }; + (forget_guards: + @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), + ) => { + unsafe { $crate::init::__internal::DropGuard::forget($field) }; + + $crate::__init_internal!(forget_guards: + @munch_fields($($rest)*), + ); + }; +} |