Messages in this thread | | | Date | Sat, 24 Jun 2023 21:14:47 +0000 | From | Benno Lossin <> | Subject | Re: [PATCH 5/7] rust: init: add `..Zeroable::zeroed()` syntax for zeroing all missing fields |
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On 6/24/23 17:11, Björn Roy Baron wrote: > On Saturday, June 24th, 2023 at 11:25, Benno Lossin <benno.lossin@proton.me> wrote: > >> Add the struct update syntax to the init macros, but only for >> `..Zeroable::zeroed()`. Adding this at the end of the struct initializer >> allows one to omit fields from the initializer, these fields will be >> initialized with 0x00 set to every byte. Only types that implement the >> `Zeroable` trait can utilize this. >> >> Suggested-by: Asahi Lina <lina@asahilina.net> >> Signed-off-by: Benno Lossin <benno.lossin@proton.me> >> --- >> rust/kernel/init.rs | 16 +++++- >> rust/kernel/init/macros.rs | 114 ++++++++++++++++++++++++++++++++++++- >> 2 files changed, 128 insertions(+), 2 deletions(-) >> >> diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs >> index ecf6a4bd0ce4..44bc3e77419a 100644 >> --- a/rust/kernel/init.rs >> +++ b/rust/kernel/init.rs >> @@ -508,14 +508,18 @@ macro_rules! stack_try_pin_init { >> /// - Fields that you want to initialize in-place have to use `<-` instead of `:`. >> /// - In front of the initializer you can write `&this in` to have access to a [`NonNull<Self>`] >> /// pointer named `this` inside of the initializer. >> +/// - Using struct update syntax one can place `..Zeroable::zeroed()` at the very end of the >> +/// struct, this initializes every field with 0 and then runs all initializers specified in the >> +/// body. This can only be done if [`Zeroable`] is implemented for the struct. >> /// >> /// For instance: >> /// >> /// ```rust >> /// # use kernel::pin_init; >> -/// # use macros::pin_data; >> +/// # use macros::{pin_data, Zeroable}; >> /// # use core::{ptr::addr_of_mut, marker::PhantomPinned}; >> /// #[pin_data] >> +/// #[derive(Zeroable)] >> /// struct Buf { >> /// // `ptr` points into `buf`. >> /// ptr: *mut u8, >> @@ -528,6 +532,10 @@ macro_rules! stack_try_pin_init { >> /// ptr: unsafe { addr_of_mut!((*this.as_ptr()).buf).cast() }, >> /// pin: PhantomPinned, >> /// }); >> +/// pin_init!(Buf { >> +/// buf: [1; 64], >> +/// ..Zeroable::zeroed(), >> +/// }); >> /// ``` >> /// >> /// [`try_pin_init!`]: kernel::try_pin_init >> @@ -547,6 +555,7 @@ macro_rules! pin_init { >> @data(PinData, use_data), >> @has_data(HasPinData, __pin_data), >> @construct_closure(pin_init_from_closure), >> + @munch_fields($($fields)*), >> ) >> }; >> } >> @@ -603,6 +612,7 @@ macro_rules! try_pin_init { >> @data(PinData, use_data), >> @has_data(HasPinData, __pin_data), >> @construct_closure(pin_init_from_closure), >> + @munch_fields($($fields)*), >> ) >> }; >> ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? { >> @@ -616,6 +626,7 @@ macro_rules! try_pin_init { >> @data(PinData, use_data), >> @has_data(HasPinData, __pin_data), >> @construct_closure(pin_init_from_closure), >> + @munch_fields($($fields)*), >> ) >> }; >> } >> @@ -650,6 +661,7 @@ macro_rules! init { >> @data(InitData, /*no use_data*/), >> @has_data(HasInitData, __init_data), >> @construct_closure(init_from_closure), >> + @munch_fields($($fields)*), >> ) >> } >> } >> @@ -700,6 +712,7 @@ macro_rules! try_init { >> @data(InitData, /*no use_data*/), >> @has_data(HasInitData, __init_data), >> @construct_closure(init_from_closure), >> + @munch_fields($($fields)*), >> ) >> }; >> ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? { >> @@ -713,6 +726,7 @@ macro_rules! try_init { >> @data(InitData, /*no use_data*/), >> @has_data(HasInitData, __init_data), >> @construct_closure(init_from_closure), >> + @munch_fields($($fields)*), >> ) >> }; >> } >> diff --git a/rust/kernel/init/macros.rs b/rust/kernel/init/macros.rs >> index 1e0c4aca055a..5dcb2e513f26 100644 >> --- a/rust/kernel/init/macros.rs >> +++ b/rust/kernel/init/macros.rs >> @@ -989,6 +989,7 @@ impl<$($impl_generics)*> $pin_data<$($ty_generics)*> >> /// >> /// This macro has multiple internal call configurations, these are always the very first ident: >> /// - nothing: this is the base case and called by the `{try_}{pin_}init!` macros. >> +/// - `with_update_parsed`: when the `..Zeroable::zeroed()` syntax has been handled. >> /// - `init_slot`: recursively creates the code that initializes all fields in `slot`. >> /// - `make_initializer`: recursively create the struct initializer that guarantees that every >> /// field has been initialized exactly once. >> @@ -1007,6 +1008,82 @@ macro_rules! __init_internal { >> @has_data($has_data:ident, $get_data:ident), >> // `pin_init_from_closure` or `init_from_closure`. >> @construct_closure($construct_closure:ident), >> + @munch_fields(), >> + ) => { >> + $crate::__init_internal!(with_update_parsed: >> + @this($($this)?), >> + @typ($t $(::<$($generics),*>)? ), >> + @fields($($fields)*), >> + @error($err), >> + @data($data, $($use_data)?), >> + @has_data($has_data, $get_data), >> + @construct_closure($construct_closure), >> + @zeroed(), // nothing means default behavior. >> + ) >> + }; >> + ( >> + @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), >> + @munch_fields(..Zeroable::zeroed()), >> + ) => { >> + $crate::__init_internal!(with_update_parsed: >> + @this($($this)?), >> + @typ($t $(::<$($generics),*>)? ), >> + @fields($($fields)*), >> + @error($err), >> + @data($data, $($use_data)?), >> + @has_data($has_data, $get_data), >> + @construct_closure($construct_closure), >> + @zeroed(()), // `()` means zero all fields not mentioned. >> + ) >> + }; >> + ( >> + @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), >> + @munch_fields($ignore:tt $($rest:tt)*), >> + ) => { >> + $crate::__init_internal!( >> + @this($($this)?), >> + @typ($t $(::<$($generics),*>)? ), >> + @fields($($fields)*), >> + @error($err), >> + @data($data, $($use_data)?), >> + @has_data($has_data, $get_data), >> + @construct_closure($construct_closure), >> + @munch_fields($($rest)*), >> + ) >> + }; >> + (with_update_parsed: >> + @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), >> + @zeroed($($init_zeroed:expr)?), >> ) => {{ >> // 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 >> @@ -1024,6 +1101,17 @@ macro_rules! __init_internal { >> { >> // Shadow the structure so it cannot be used to return early. >> struct __InitOk; >> + // If `$init_zeroed` is present we should zero the slot now and not emit an >> + // error when fields are missing (since they will be zeroed). We also have to >> + // check that the type actually implements `Zeroable`. >> + $( >> + fn is_zeroable<T: Zeroable>(ptr: *mut T) {} > > Maybe call this assert_zeroable?
Sure.
> >> + // Ensure that the struct is indeed `Zeroable`. >> + is_zeroable(slot); >> + // SAFETY: The type implements `Zeroable` by the check above. >> + unsafe { ::core::ptr::write_bytes(slot, 0, 1) }; >> + $init_zeroed // this will be `()` if set. > > How does this work? Shouldn't there be a ; after $init_zeroed to consume the () value?
It is the last expression of a block and since it is `()` it is ok (adding a ; would also be ok, but it is not necessary).
> >> + )? >> // Create the `this` so it can be referenced by the user inside of the >> // expressions creating the individual fields. >> $(let $this = unsafe { ::core::ptr::NonNull::new_unchecked(slot) };)? >> @@ -1064,7 +1152,7 @@ macro_rules! __init_internal { >> @data($data:ident), >> @slot($slot:ident), >> @guards($($guards:ident,)*), >> - @munch_fields($(,)?), >> + @munch_fields($(..Zeroable::zeroed())? $(,)?), >> ) => { >> // Endpoint of munching, no fields are left. If execution reaches this point, all fields >> // have been initialized. Therefore we can now dismiss the guards by forgetting them. >> @@ -1157,6 +1245,30 @@ macro_rules! __init_internal { >> @munch_fields($($rest)*), >> ); >> }; >> + (make_initializer: >> + @slot($slot:ident), >> + @type_name($t:ident), >> + @munch_fields(..Zeroable::zeroed() $(,)?), >> + @acc($($acc:tt)*), >> + ) => { >> + // Endpoint, nothing more to munch, create the initializer. Since the users specified >> + // `..Zeroable::zeroed()`, the slot will already have been zeroed and all field that have >> + // not been overwritten are thus zero and initialized. We still check that all fields are >> + // actually accessible by using the struct update syntax ourselves. >> + // Since we are in the `if false` branch, this will never get executed. We abuse `slot` to >> + // get the correct type inference here: >> + unsafe { >> + let mut zeroed = ::core::mem::zeroed(); >> + // We have to use type inference her to make zeroed have the correct type. This does > > *here
Will fix.
-- Cheers, Benno
> >> + // not get executed, so it has no effect. >> + ::core::ptr::write($slot, zeroed); >> + zeroed = ::core::mem::zeroed(); >> + ::core::ptr::write($slot, $t { >> + $($acc)* >> + ..zeroed >> + }); >> + } >> + }; >> (make_initializer: >> @slot($slot:ident), >> @type_name($t:ident), >> -- >> 2.41.0 > > Cheers, > Björn
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