Skip to content

Commit 42415d1

Browse files
BennoLossinBennoLossin
committed
rust: pin-init: add references to previously initialized fields
After initializing a field in an initializer macro, create a variable holding a reference that points at that field. The type is either `Pin<&mut T>` or `&mut T` depending on the field's structural pinning kind. [ Applied fixes to devres and rust_driver_pci sample - Benno] Reviewed-by: Danilo Krummrich <dakr@kernel.org> Signed-off-by: Benno Lossin <lossin@kernel.org>
1 parent 1fa5167 commit 42415d1

3 files changed

Lines changed: 118 additions & 39 deletions

File tree

‎rust/kernel/devres.rs‎

Lines changed: 2 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -134,11 +134,9 @@ impl<T: Send> Devres<T> {
134134
T: 'a,
135135
Error: From<E>,
136136
{
137-
let callback = Self::devres_callback;
138-
139137
try_pin_init!(&this in Self {
140138
dev: dev.into(),
141-
callback,
139+
callback: Self::devres_callback,
142140
// INVARIANT: `inner` is properly initialized.
143141
inner <- {
144142
// SAFETY: `this` is a valid pointer to uninitialized memory.
@@ -151,7 +149,7 @@ impl<T: Send> Devres<T> {
151149
// properly initialized, because we require `dev` (i.e. the *bound* device) to
152150
// live at least as long as the returned `impl PinInit<Self, Error>`.
153151
to_result(unsafe {
154-
bindings::devm_add_action(dev.as_raw(), Some(callback), inner.cast())
152+
bindings::devm_add_action(dev.as_raw(), Some(*callback), inner.cast())
155153
})?;
156154

157155
Opaque::pin_init(try_pin_init!(Inner {

‎rust/pin-init/src/macros.rs‎

Lines changed: 115 additions & 34 deletions
Original file line numberDiff line numberDiff line change
@@ -1049,38 +1049,56 @@ macro_rules! __pin_data {
10491049
@pinned($($(#[$($p_attr:tt)*])* $pvis:vis $p_field:ident : $p_type:ty),* $(,)?),
10501050
@not_pinned($($(#[$($attr:tt)*])* $fvis:vis $field:ident : $type:ty),* $(,)?),
10511051
) => {
1052-
// For every field, we create a projection function according to its projection type. If a
1053-
// field is structurally pinned, then it must be initialized via `PinInit`, if it is not
1054-
// structurally pinned, then it can be initialized via `Init`.
1055-
//
1056-
// The functions are `unsafe` to prevent accidentally calling them.
1057-
#[allow(dead_code)]
1058-
#[expect(clippy::missing_safety_doc)]
1059-
impl<$($impl_generics)*> $pin_data<$($ty_generics)*>
1060-
where $($whr)*
1061-
{
1062-
$(
1063-
$(#[$($p_attr)*])*
1064-
$pvis unsafe fn $p_field<E>(
1065-
self,
1066-
slot: *mut $p_type,
1067-
init: impl $crate::PinInit<$p_type, E>,
1068-
) -> ::core::result::Result<(), E> {
1069-
// SAFETY: TODO.
1070-
unsafe { $crate::PinInit::__pinned_init(init, slot) }
1071-
}
1072-
)*
1073-
$(
1074-
$(#[$($attr)*])*
1075-
$fvis unsafe fn $field<E>(
1076-
self,
1077-
slot: *mut $type,
1078-
init: impl $crate::Init<$type, E>,
1079-
) -> ::core::result::Result<(), E> {
1080-
// SAFETY: TODO.
1081-
unsafe { $crate::Init::__init(init, slot) }
1082-
}
1083-
)*
1052+
$crate::macros::paste! {
1053+
// For every field, we create a projection function according to its projection type. If a
1054+
// field is structurally pinned, then it must be initialized via `PinInit`, if it is not
1055+
// structurally pinned, then it can be initialized via `Init`.
1056+
//
1057+
// The functions are `unsafe` to prevent accidentally calling them.
1058+
#[allow(dead_code)]
1059+
#[expect(clippy::missing_safety_doc)]
1060+
impl<$($impl_generics)*> $pin_data<$($ty_generics)*>
1061+
where $($whr)*
1062+
{
1063+
$(
1064+
$(#[$($p_attr)*])*
1065+
$pvis unsafe fn $p_field<E>(
1066+
self,
1067+
slot: *mut $p_type,
1068+
init: impl $crate::PinInit<$p_type, E>,
1069+
) -> ::core::result::Result<(), E> {
1070+
// SAFETY: TODO.
1071+
unsafe { $crate::PinInit::__pinned_init(init, slot) }
1072+
}
1073+
1074+
$(#[$($p_attr)*])*
1075+
$pvis unsafe fn [<__project_ $p_field>]<'__slot>(
1076+
self,
1077+
slot: &'__slot mut $p_type,
1078+
) -> ::core::pin::Pin<&'__slot mut $p_type> {
1079+
::core::pin::Pin::new_unchecked(slot)
1080+
}
1081+
)*
1082+
$(
1083+
$(#[$($attr)*])*
1084+
$fvis unsafe fn $field<E>(
1085+
self,
1086+
slot: *mut $type,
1087+
init: impl $crate::Init<$type, E>,
1088+
) -> ::core::result::Result<(), E> {
1089+
// SAFETY: TODO.
1090+
unsafe { $crate::Init::__init(init, slot) }
1091+
}
1092+
1093+
$(#[$($attr)*])*
1094+
$fvis unsafe fn [<__project_ $field>]<'__slot>(
1095+
self,
1096+
slot: &'__slot mut $type,
1097+
) -> &'__slot mut $type {
1098+
slot
1099+
}
1100+
)*
1101+
}
10841102
}
10851103
};
10861104
}
@@ -1292,6 +1310,13 @@ macro_rules! __init_internal {
12921310
// return when an error/panic occurs.
12931311
// We also use the `data` to require the correct trait (`Init` or `PinInit`) for `$field`.
12941312
unsafe { $data.$field(::core::ptr::addr_of_mut!((*$slot).$field), init)? };
1313+
// SAFETY:
1314+
// - the project function does the correct field projection,
1315+
// - the field has been initialized,
1316+
// - the reference is only valid until the end of the initializer.
1317+
#[allow(unused_variables)]
1318+
let $field = $crate::macros::paste!(unsafe { $data.[< __project_ $field >](&mut (*$slot).$field) });
1319+
12951320
// Create the drop guard:
12961321
//
12971322
// We rely on macro hygiene to make it impossible for users to access this local variable.
@@ -1323,6 +1348,14 @@ macro_rules! __init_internal {
13231348
// SAFETY: `slot` is valid, because we are inside of an initializer closure, we
13241349
// return when an error/panic occurs.
13251350
unsafe { $crate::Init::__init(init, ::core::ptr::addr_of_mut!((*$slot).$field))? };
1351+
1352+
// SAFETY:
1353+
// - the field is not structurally pinned, since the line above must compile,
1354+
// - the field has been initialized,
1355+
// - the reference is only valid until the end of the initializer.
1356+
#[allow(unused_variables)]
1357+
let $field = unsafe { &mut (*$slot).$field };
1358+
13261359
// Create the drop guard:
13271360
//
13281361
// We rely on macro hygiene to make it impossible for users to access this local variable.
@@ -1341,7 +1374,48 @@ macro_rules! __init_internal {
13411374
);
13421375
}
13431376
};
1344-
(init_slot($($use_data:ident)?):
1377+
(init_slot(): // No `use_data`, so all fields are not structurally pinned
1378+
@data($data:ident),
1379+
@slot($slot:ident),
1380+
@guards($($guards:ident,)*),
1381+
// Init by-value.
1382+
@munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*),
1383+
) => {
1384+
{
1385+
$(let $field = $val;)?
1386+
// Initialize the field.
1387+
//
1388+
// SAFETY: The memory at `slot` is uninitialized.
1389+
unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) };
1390+
}
1391+
1392+
#[allow(unused_variables)]
1393+
// SAFETY:
1394+
// - the field is not structurally pinned, since no `use_data` was required to create this
1395+
// initializer,
1396+
// - the field has been initialized,
1397+
// - the reference is only valid until the end of the initializer.
1398+
let $field = unsafe { &mut (*$slot).$field };
1399+
1400+
// Create the drop guard:
1401+
//
1402+
// We rely on macro hygiene to make it impossible for users to access this local variable.
1403+
// We use `paste!` to create new hygiene for `$field`.
1404+
$crate::macros::paste! {
1405+
// SAFETY: We forget the guard later when initialization has succeeded.
1406+
let [< __ $field _guard >] = unsafe {
1407+
$crate::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field))
1408+
};
1409+
1410+
$crate::__init_internal!(init_slot():
1411+
@data($data),
1412+
@slot($slot),
1413+
@guards([< __ $field _guard >], $($guards,)*),
1414+
@munch_fields($($rest)*),
1415+
);
1416+
}
1417+
};
1418+
(init_slot($use_data:ident):
13451419
@data($data:ident),
13461420
@slot($slot:ident),
13471421
@guards($($guards:ident,)*),
@@ -1355,6 +1429,13 @@ macro_rules! __init_internal {
13551429
// SAFETY: The memory at `slot` is uninitialized.
13561430
unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) };
13571431
}
1432+
// SAFETY:
1433+
// - the project function does the correct field projection,
1434+
// - the field has been initialized,
1435+
// - the reference is only valid until the end of the initializer.
1436+
#[allow(unused_variables)]
1437+
let $field = $crate::macros::paste!(unsafe { $data.[< __project_ $field >](&mut (*$slot).$field) });
1438+
13581439
// Create the drop guard:
13591440
//
13601441
// We rely on macro hygiene to make it impossible for users to access this local variable.
@@ -1365,7 +1446,7 @@ macro_rules! __init_internal {
13651446
$crate::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field))
13661447
};
13671448

1368-
$crate::__init_internal!(init_slot($($use_data)?):
1449+
$crate::__init_internal!(init_slot($use_data):
13691450
@data($data),
13701451
@slot($slot),
13711452
@guards([< __ $field _guard >], $($guards,)*),

‎samples/rust/rust_driver_pci.rs‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -78,8 +78,8 @@ impl pci::Driver for SampleDriver {
7878

7979
let drvdata = KBox::pin_init(
8080
try_pin_init!(Self {
81-
pdev: pdev.into(),
8281
bar <- pdev.iomap_region_sized::<{ Regs::END }>(0, c_str!("rust_driver_pci")),
82+
pdev: pdev.into(),
8383
index: *info,
8484
}),
8585
GFP_KERNEL,

0 commit comments

Comments
 (0)