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

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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: Asahi Lina <lina@asahilina.net>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Benno Lossin <benno.lossin@proton.me>
Link: https://lore.kernel.org/r/20230814084602.25699-10-benno.lossin@proton.me
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Benno Lossin 2023-08-14 08:47:28 +00:00 committed by Miguel Ojeda
parent 9e49439077
commit 674b1c7aed
1 changed files with 35 additions and 19 deletions
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54
rust/kernel/init/macros.rs
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@ -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();
::core::ptr::write($slot, $t {
$($acc)*
..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 {
::core::ptr::write($slot, $t {
$($acc)*
});
// 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)*),
) => {