Commit 674b1c7a authored by Benno Lossin's avatar Benno Lossin Committed by Miguel Ojeda
Browse files

rust: init: add support for arbitrary paths in init macros 



Previously only `ident` and generic types were supported in the
`{try_}{pin_}init!` macros. This patch allows arbitrary path fragments,
so for example `Foo::Bar` but also very complex paths such as
`<Foo as Baz>::Bar::<0, i32>`.

Internally this is accomplished by using `path` fragments. Due to some
peculiar declarative macro limitations, we have to "forget" certain
additional parsing information in the token trees. This is achieved by
using the `paste!` proc macro. It does not actually modify the input,
since no `[< >]` will be present in the input, so it just strips the
information held by declarative macros. For example, if a declarative
macro takes `$t:path` as its input, it cannot sensibly propagate this to
a macro that takes `$($p:tt)*` as its input, since the `$t` token will
only be considered one `tt` token for the second macro. If we first pipe
the tokens through `paste!`, then it parses as expected.

Suggested-by: default avatarAsahi Lina <lina@asahilina.net>
Reviewed-by: default avatarMartin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Reviewed-by: default avatarGary Guo <gary@garyguo.net>
Signed-off-by: default avatarBenno Lossin <benno.lossin@proton.me>
Link: https://lore.kernel.org/r/20230814084602.25699-10-benno.lossin@proton.me


Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent 9e494390

rust/kernel/init/macros.rs

+35 −19
Original line number Diff line number Diff line
@@ -1000,7 +1000,7 @@ macro_rules! __pin_data { 
macro_rules! __init_internal {

    (

        @this($($this:ident)?),

        @typ($t:ident $(::<$($generics:ty),*>)?),

        @typ($t:path),

        @fields($($fields:tt)*),

        @error($err:ty),

        // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData`
@@ -1014,7 +1014,7 @@ macro_rules! __init_internal { 
    ) => {

        $crate::__init_internal!(with_update_parsed:

            @this($($this)?),

            @typ($t $(::<$($generics),*>)? ),

            @typ($t),

            @fields($($fields)*),

            @error($err),

            @data($data, $($use_data)?),
@@ -1025,7 +1025,7 @@ macro_rules! __init_internal { 
    };

    (

        @this($($this:ident)?),

        @typ($t:ident $(::<$($generics:ty),*>)?),

        @typ($t:path),

        @fields($($fields:tt)*),

        @error($err:ty),

        // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData`
@@ -1039,7 +1039,7 @@ macro_rules! __init_internal { 
    ) => {

        $crate::__init_internal!(with_update_parsed:

            @this($($this)?),

            @typ($t $(::<$($generics),*>)? ),

            @typ($t),

            @fields($($fields)*),

            @error($err),

            @data($data, $($use_data)?),
@@ -1050,7 +1050,7 @@ macro_rules! __init_internal { 
    };

    (

        @this($($this:ident)?),

        @typ($t:ident $(::<$($generics:ty),*>)?),

        @typ($t:path),

        @fields($($fields:tt)*),

        @error($err:ty),

        // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData`
@@ -1064,7 +1064,7 @@ macro_rules! __init_internal { 
    ) => {

        $crate::__init_internal!(

            @this($($this)?),

            @typ($t $(::<$($generics),*>)? ),

            @typ($t),

            @fields($($fields)*),

            @error($err),

            @data($data, $($use_data)?),
@@ -1075,7 +1075,7 @@ macro_rules! __init_internal { 
    };

    (with_update_parsed:

        @this($($this:ident)?),

        @typ($t:ident $(::<$($generics:ty),*>)?),

        @typ($t:path),

        @fields($($fields:tt)*),

        @error($err:ty),

        // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData`
@@ -1094,7 +1094,11 @@ macro_rules! __init_internal { 
        // Get the data about fields from the supplied type.

        let data = unsafe {

            use $crate::init::__internal::$has_data;

            $t$(::<$($generics),*>)?::$get_data()

            // Here we abuse `paste!` to retokenize `$t`. Declarative macros have some internal

            // information that is associated to already parsed fragments, so a path fragment

            // cannot be used in this position. Doing the retokenization results in valid rust

            // code.

            ::kernel::macros::paste!($t::$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>(
@@ -1253,7 +1257,7 @@ macro_rules! __init_internal { 
    };

    (make_initializer:

        @slot($slot:ident),

        @type_name($t:ident),

        @type_name($t:path),

        @munch_fields(..Zeroable::zeroed() $(,)?),

        @acc($($acc:tt)*),

    ) => {
@@ -1270,15 +1274,21 @@ macro_rules! __init_internal { 
            // not get executed, so it has no effect.

            ::core::ptr::write($slot, zeroed);

            zeroed = ::core::mem::zeroed();

            // Here we abuse `paste!` to retokenize `$t`. Declarative macros have some internal

            // information that is associated to already parsed fragments, so a path fragment

            // cannot be used in this position. Doing the retokenization results in valid rust

            // code.

            ::kernel::macros::paste!(

                ::core::ptr::write($slot, $t {

                    $($acc)*

                    ..zeroed

                });

            );

        }

    };

    (make_initializer:

        @slot($slot:ident),

        @type_name($t:ident),

        @type_name($t:path),

        @munch_fields($(,)?),

        @acc($($acc:tt)*),

    ) => {
@@ -1286,14 +1296,20 @@ macro_rules! __init_internal { 
        // Since we are in the closure that is never called, this will never get executed.

        // We abuse `slot` to get the correct type inference here:

        unsafe {

            // Here we abuse `paste!` to retokenize `$t`. Declarative macros have some internal

            // information that is associated to already parsed fragments, so a path fragment

            // cannot be used in this position. Doing the retokenization results in valid rust

            // code.

            ::kernel::macros::paste!(

                ::core::ptr::write($slot, $t {

                    $($acc)*

                });

            );

        }

    };

    (make_initializer:

        @slot($slot:ident),

        @type_name($t:ident),

        @type_name($t:path),

        @munch_fields($field:ident <- $val:expr, $($rest:tt)*),

        @acc($($acc:tt)*),

    ) => {
@@ -1306,7 +1322,7 @@ macro_rules! __init_internal { 
    };

    (make_initializer:

        @slot($slot:ident),

        @type_name($t:ident),

        @type_name($t:path),

        @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*),

        @acc($($acc:tt)*),

    ) => {