rust: uaccess: add __rust_helper to helpers

This is needed to inline these helpers into Rust code.

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260105-define-rust-helper-v2-23-51da5f454a67@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: Darksonn

rust/helpers/uaccess.c

@@ -2,24 +2,26 @@
 
 #include <linux/uaccess.h>
 
-unsigned long rust_helper_copy_from_user(void *to, const void __user *from,
-					 unsigned long n)
+__rust_helper unsigned long
+rust_helper_copy_from_user(void *to, const void __user *from, unsigned long n)
 {
 	return copy_from_user(to, from, n);
 }
 
-unsigned long rust_helper_copy_to_user(void __user *to, const void *from,
-				       unsigned long n)
+__rust_helper unsigned long
+rust_helper_copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	return copy_to_user(to, from, n);
 }
 
 #ifdef INLINE_COPY_FROM_USER
+__rust_helper
 unsigned long rust_helper__copy_from_user(void *to, const void __user *from, unsigned long n)
 {
 	return _inline_copy_from_user(to, from, n);
 }
 
+__rust_helper
 unsigned long rust_helper__copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	return _inline_copy_to_user(to, from, n);