From: Gary Guo <gary@garyguo.net>
Date: Tue, 12 May 2026 12:09:53 +0000 (+0100)
Subject: rust: pin-init: internal: project using full slot
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6fb5912c92926025a7e205d53feb73c3478c79a1;p=thirdparty%2Fkernel%2Flinux.git

rust: pin-init: internal: project using full slot

Instead of projecting using pointer to a field project the full slot. This
further shifts the code generation from the initializer site to the struct
definition site, which means less code is generated overall.

It also makes the safety comment easier to justify, as now the projection
is done by the `#[pin_data]` macro which has full visibility of pinnedness
of fields.

The field alignment could also be checked on the `#[pin_data]` side;
however, since `init!()` macro works for other type of structs, we cannot
remove the alignment check from `init!`/`pin_init!` side anyway, so I opted
to still keep the alignment check in init.rs.

Signed-off-by: Gary Guo <gary@garyguo.net>
---

diff --git a/rust/pin-init/internal/src/init.rs b/rust/pin-init/internal/src/init.rs
index e6f5ea06f91bc..699b105570a54 100644
--- a/rust/pin-init/internal/src/init.rs
+++ b/rust/pin-init/internal/src/init.rs
@@ -245,12 +245,11 @@ fn init_fields(
         let slot = if pinned {
             quote! {
                 // SAFETY:
-                // - `&raw mut (*slot).#ident` points to the `#ident` field of `slot`.
-                // - `&raw mut (*slot).#ident` is valid.
+                // - `slot` is valid and properly aligned.
                 // - `make_field_check` checks that `&raw mut (*slot).#ident` is properly aligned.
                 // - `make_field_check` prevents `#ident` from being used twice, therefore
                 //   `(*slot).#ident` is exclusively accessed and has not been initialized.
-                (unsafe { #data.#ident(&raw mut (*#slot).#ident) })
+                (unsafe { #data.#ident(#slot) })
             }
         } else {
             quote! {
diff --git a/rust/pin-init/internal/src/pin_data.rs b/rust/pin-init/internal/src/pin_data.rs
index 926f84a014c61..2284256a62207 100644
--- a/rust/pin-init/internal/src/pin_data.rs
+++ b/rust/pin-init/internal/src/pin_data.rs
@@ -377,21 +377,21 @@ fn generate_the_pin_data(
             quote! {
                 /// # Safety
                 ///
-                /// - `slot` points to a `#field_name` field of a pinned struct that this
-                ///   `__ThePinData` describes.
-                /// - `slot` is a valid, properly aligned and points to uninitialized and
-                ///   exclusively accessed memory.
+                /// - `slot` is valid and properly aligned.
+                /// - `(*slot).#field_name` is properly aligned.
+                /// - `(*slot).#field_name` points to uninitialized and exclusively accessed
+                ///   memory.
                 #(#attrs)*
                 #[inline(always)]
                 #vis unsafe fn #field_name(
                     self,
-                    slot: *mut #ty,
+                    slot: *mut #struct_name #ty_generics,
                 ) -> ::pin_init::__internal::Slot<::pin_init::__internal::#pin_marker, #ty> {
                     // SAFETY:
                     // - If `#pin_marker` is `Pinned`, the corresponding field is structurally
                     //   pinned.
                     // - Other safety requirements follows the safety requirement.
-                    unsafe { ::pin_init::__internal::Slot::new(slot) }
+                    unsafe { ::pin_init::__internal::Slot::new(&raw mut (*slot).#field_name) }
                 }
             }
         })
diff --git a/rust/pin-init/src/lib.rs b/rust/pin-init/src/lib.rs
index e891d65cc469a..c9e2cbe279157 100644
--- a/rust/pin-init/src/lib.rs
+++ b/rust/pin-init/src/lib.rs
@@ -868,7 +868,7 @@ pub use pin_init_internal::init;
 macro_rules! assert_pinned {
     ($ty:ty, $field:ident, $field_ty:ty, inline) => {
         // SAFETY: This code is unreachable.
-        let _ = move |ptr: *mut $field_ty| unsafe {
+        let _ = move |ptr: *mut $ty| unsafe {
             let data = <$ty as $crate::__internal::HasPinData>::__pin_data();
             _ = data
                 .$field(ptr)