From f41941aab3acd33f13d65a2ae496329bc8ae4de0 Mon Sep 17 00:00:00 2001 From: Gary Guo Date: Mon, 2 Mar 2026 16:42:35 +0000 Subject: rust: ptr: add projection infrastructure Add a generic infrastructure for performing field and index projections on raw pointers. This will form the basis of performing I/O projections. Pointers manipulations are intentionally using the safe wrapping variants instead of the unsafe variants, as the latter requires pointers to be inside an allocation which is not necessarily true for I/O pointers. This projection macro protects against rogue `Deref` implementation, which can causes the projected pointer to be outside the bounds of starting pointer. This is extremely unlikely and Rust has a lint to catch this, but is unsoundness regardless. The protection works by inducing type inference ambiguity when `Deref` is implemented. This projection macro also stops projecting into unaligned fields (i.e. fields of `#[repr(packed)]` structs), as misaligned pointers require special handling. This is implemented by attempting to create reference to projected field inside a `if false` block. Despite being unreachable, Rust still checks that they're not unaligned fields. The projection macro supports both fallible and infallible index projections. These are described in detail inside the documentation. Signed-off-by: Gary Guo Reviewed-by: Benno Lossin Acked-by: Miguel Ojeda Link: https://patch.msgid.link/20260302164239.284084-3-gary@kernel.org [ * Add intro-doc links where possible, * Fix typos and slightly improve wording, e.g. "as documentation describes" -> "as the documentation of [`Self::proj`] describes", * Add an empty line between regular and safety comments, before examples, and between logically independent comments, * Capitalize various safety comments. - Danilo ] Signed-off-by: Danilo Krummrich --- rust/kernel/ptr.rs | 3 +++ 1 file changed, 3 insertions(+) (limited to 'rust/kernel/ptr.rs') diff --git a/rust/kernel/ptr.rs b/rust/kernel/ptr.rs index e91de5f0d78f..bdc2d79ff669 100644 --- a/rust/kernel/ptr.rs +++ b/rust/kernel/ptr.rs @@ -2,6 +2,9 @@ //! Types and functions to work with pointers and addresses. +pub mod projection; +pub use crate::project_pointer as project; + use core::mem::{ align_of, size_of, // -- cgit v1.2.3