linux-kernel - [PATCH 2/5] rust: map `__kernel_size_t` and friends also to usize/isize

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Message-ID: <20240913213041.395655-3-gary@garyguo.net>
Date: Fri, 13 Sep 2024 22:29:22 +0100
From: Gary Guo <gary@...yguo.net>
To: Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Wedson Almeida Filho <wedsonaf@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...sung.com>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	Finn Behrens <me@...enk.dev>,
	Martin Rodriguez Reboredo <yakoyoku@...il.com>
Cc: rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/5] rust: map `__kernel_size_t` and friends also to usize/isize

Currently bindgen has special logic to recognise `size_t` and `ssize_t`
and map them to Rust `usize` and `isize`. Similarly, `ptrdiff_t` is
mapped to `isize`.

However this falls short for `__kernel_size_t`, `__kernel_ssize_t` and
`__kernel_ptrdiff_t`. To ensure that they are mapped to usize/isize
rather than 32/64 integers depending on platform, blocklist them in
bindgen parameters and manually provide their definition.

Signed-off-by: Gary Guo <gary@...yguo.net>
---
 rust/bindgen_parameters | 5 +++++
 rust/bindings/lib.rs    | 5 +++++
 rust/uapi/lib.rs        | 5 +++++
 3 files changed, 15 insertions(+)

diff --git a/rust/bindgen_parameters b/rust/bindgen_parameters
index a721d466bee4b..756307dd59350 100644
--- a/rust/bindgen_parameters
+++ b/rust/bindgen_parameters
@@ -1,5 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0
 
+# We want to map these types to isize/usize manually, instead of
+# define them as int/long depending on platform bitwidth.
+--blocklist-type __kernel_s?size_t
+--blocklist-type __kernel_ptrdiff_t
+
 --opaque-type xregs_state
 --opaque-type desc_struct
 --opaque-type arch_lbr_state
diff --git a/rust/bindings/lib.rs b/rust/bindings/lib.rs
index 93a1a3fc97bc9..9999c90e8db14 100644
--- a/rust/bindings/lib.rs
+++ b/rust/bindings/lib.rs
@@ -26,6 +26,11 @@
 
 #[allow(dead_code)]
 mod bindings_raw {
+    // Manual definition for blocklisted types.
+    type __kernel_size_t = usize;
+    type __kernel_ssize_t = isize;
+    type __kernel_ptrdiff_t = isize;
+
     // Use glob import here to expose all helpers.
     // Symbols defined within the module will take precedence to the glob import.
     pub use super::bindings_helper::*;
diff --git a/rust/uapi/lib.rs b/rust/uapi/lib.rs
index 80a00260e3e7a..0eca836c0dbbb 100644
--- a/rust/uapi/lib.rs
+++ b/rust/uapi/lib.rs
@@ -24,4 +24,9 @@
     unsafe_op_in_unsafe_fn
 )]
 
+// Manual definition of blocklisted types.
+type __kernel_size_t = usize;
+type __kernel_ssize_t = isize;
+type __kernel_ptrdiff_t = isize;
+
 include!(concat!(env!("OBJTREE"), "/rust/uapi/uapi_generated.rs"));
-- 
2.44.1