[PATCH 6.18 199/227] rust: io: always inline functions using build_assert with arguments

Greg Kroah-Hartman
2026-01-28T16:01:20Z

From: Alexandre Courbot <acourbot@nvidia.com>

commit 33d19f621641de1b6ec6fe1bb2ac68a7d2c61f6a upstream.

`build_assert` relies on the compiler to optimize out its error path.
Functions using it with its arguments must thus always be inlined,
otherwise the error path of `build_assert` might not be optimized out,
triggering a build error.

Cc: stable@vger.kernel.org
Fixes: ce30d94e6855 ("rust: add `io::{Io, IoRaw}` base types")
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Timur Tabi <ttabi@nvidia.com>
Link: https://patch.msgid.link/20251208-io-build-assert-v3-2-98aded02c1ea@nvidia.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
rust/kernel/io.rs | 9 ++++++---
rust/kernel/io/resource.rs | 2 ++
2 files changed, 8 insertions(+), 3 deletions(-)

--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -140,7 +140,8 @@ macro_rules! define_read {
/// Bound checks are performed on compile time, hence if the offset is not known at compile
/// time, the build will fail.
$(#[$attr])*
- #[inline]
+ // Always inline to optimize out error path of `io_addr_assert`.
+ #[inline(always)]
pub fn $name(&self, offset: usize) -> $type_name {
let addr = self.io_addr_assert::<$type_name>(offset);

@@ -169,7 +170,8 @@ macro_rules! define_write {
/// Bound checks are performed on compile time, hence if the offset is not known at compile
/// time, the build will fail.
$(#[$attr])*
- #[inline]
+ // Always inline to optimize out error path of `io_addr_assert`.
+ #[inline(always)]
pub fn $name(&self, value: $type_name, offset: usize) {
let addr = self.io_addr_assert::<$type_name>(offset);

@@ -237,7 +239,8 @@ impl<const SIZE: usize> Io<SIZE> {
self.addr().checked_add(offset).ok_or(EINVAL)
}

- #[inline]
+ // Always inline to optimize out error path of `build_assert`.
+ #[inline(always)]
fn io_addr_assert(&self, offset: usize) -> usize {
build_assert!(Self::offset_valid::(offset, SIZE));

--- a/rust/kernel/io/resource.rs
+++ b/rust/kernel/io/resource.rs
@@ -222,6 +222,8 @@ impl Flags {
/// Resource represents a memory region that must be ioremaped using `ioremap_np`.
pub const IORESOURCE_MEM_NONPOSTED: Flags = Flags::new(bindings::IORESOURCE_MEM_NONPOSTED);

+ // Always inline to optimize out error path of `build_assert`.
+ #[inline(always)]
const fn new(value: u32) -> Self {
crate::build_assert!(value as u64 <= c_ulong::MAX as u64);
Flags(value as c_ulong)