linux-kernel - [PATCH v2] rust: uaccess: mark UserSliceReader methods inline

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Message-ID: <010001958798b97c-4da7647e-d0bc-4f81-9132-ad24353139cb-000000@email.amazonses.com>
Date: Tue, 11 Mar 2025 23:44:48 +0000
From: Antonio Hickey <contact@...oniohickey.com>
To: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...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@...nel.org>, 
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, 
	Danilo Krummrich <dakr@...nel.org>, 
	Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>, 
	Bill Wendling <morbo@...gle.com>, 
	Justin Stitt <justinstitt@...gle.com>
Cc: Antonio Hickey <contact@...oniohickey.com>, 
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org, 
	llvm@...ts.linux.dev
Subject: [PATCH v2] rust: uaccess: mark UserSliceReader methods inline

When you build the kernel using the llvm-19.1.4-rust-1.83.0-x86_64
toolchain provided by kernel.org with ARCH=x86_64, the following symbols
are generated:

$nm vmlinux | grep ' _R'.*UserSliceReader | rustfilt
ffffffff817c3320 T <kernel::uaccess::UserSliceReader>::read_slice
ffffffff817c32b0 T <kernel::uaccess::UserSliceReader>::read_raw

However, these Rust symbols are trivial wrappers around the functions
copy_from_user, _copy_from_user respectively. It doesn't
make sense to go through a trivial wrapper for these functions, so mark
them inline.

After applying this patch, the above command will produce no output.

Link: https://github.com/Rust-for-Linux/linux/issues/1145
Suggested-by: https://github.com/Rust-for-Linux/linux/issues/1145
Signed-off-by: Antonio Hickey <contact@...oniohickey.com>
---
 rust/kernel/uaccess.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/rust/kernel/uaccess.rs b/rust/kernel/uaccess.rs
index 719b0a48ff55..3d8a08aeed89 100644
--- a/rust/kernel/uaccess.rs
+++ b/rust/kernel/uaccess.rs
@@ -218,6 +218,7 @@ pub fn is_empty(&self) -> bool {
     /// # Guarantees
     ///
     /// After a successful call to this method, all bytes in `out` are initialized.
+    #[inline]
     pub fn read_raw(&mut self, out: &mut [MaybeUninit<u8>]) -> Result {
         let len = out.len();
         let out_ptr = out.as_mut_ptr().cast::<c_void>();
@@ -239,6 +240,7 @@ pub fn read_raw(&mut self, out: &mut [MaybeUninit<u8>]) -> Result {
     ///
     /// Fails with [`EFAULT`] if the read happens on a bad address, or if the read goes out of
     /// bounds of this [`UserSliceReader`]. This call may modify `out` even if it returns an error.
+    #[inline]
     pub fn read_slice(&mut self, out: &mut [u8]) -> Result {
         // SAFETY: The types are compatible and `read_raw` doesn't write uninitialized bytes to
         // `out`.
-- 
2.48.1