From 8758b75aac12cfec471032d704bb44447e8aa091 Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Sun, 10 Jul 2022 16:13:01 +0200
Subject: [PATCH] Re-implement concat_idents! in libmacros
MIME-Version: 1.0
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This removes an unstable feature used by kernel modules. The new proc
macro also has different behavior with respect to macro hygiene. Unlike
the unstable concat_idents! macro it for example allows referring to
local variables by taking the span of the second macro as span for the
output identifier.

Signed-off-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
---
 drivers/android/defs.rs      |  2 +-
 rust/kernel/lib.rs           |  3 ++-
 rust/macros/concat_idents.rs | 23 +++++++++++++++++++
 rust/macros/lib.rs           | 44 ++++++++++++++++++++++++++++++++++++
 scripts/Makefile.build       |  2 +-
 5 files changed, 71 insertions(+), 3 deletions(-)
 create mode 100644 rust/macros/concat_idents.rs

diff --git a/drivers/android/defs.rs b/drivers/android/defs.rs
index ec2dde9b3dd84c..925e751a2564a5 100644
--- a/drivers/android/defs.rs
+++ b/drivers/android/defs.rs
@@ -9,7 +9,7 @@ use kernel::{
 
 macro_rules! pub_no_prefix {
     ($prefix:ident, $($newname:ident),+) => {
-        $(pub(crate) const $newname: u32 = concat_idents!($prefix, $newname);)+
+        $(pub(crate) const $newname: u32 = kernel::macros::concat_idents!($prefix, $newname);)+
     };
 }
 
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index d752b6f6352f2a..efb0dd3ca06cfa 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -14,7 +14,6 @@
 #![no_std]
 #![feature(allocator_api)]
 #![feature(associated_type_defaults)]
-#![feature(concat_idents)]
 #![feature(const_mut_refs)]
 #![feature(const_ptr_offset_from)]
 #![feature(const_refs_to_cell)]
@@ -41,6 +40,8 @@ mod allocator;
 #[doc(hidden)]
 pub use bindings;
 
+pub use macros;
+
 #[cfg(CONFIG_ARM_AMBA)]
 pub mod amba;
 pub mod chrdev;
diff --git a/rust/macros/concat_idents.rs b/rust/macros/concat_idents.rs
new file mode 100644
index 00000000000000..3b5a9dd70e8a2b
--- /dev/null
+++ b/rust/macros/concat_idents.rs
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use proc_macro::{token_stream, Ident, TokenStream, TokenTree};
+
+use crate::helpers::expect_punct;
+
+fn expect_ident(it: &mut token_stream::IntoIter) -> Ident {
+    if let Some(TokenTree::Ident(ident)) = it.next() {
+        ident
+    } else {
+        panic!("Expected Ident")
+    }
+}
+
+pub(crate) fn concat_idents(ts: TokenStream) -> TokenStream {
+    let mut it = ts.into_iter();
+    let a = expect_ident(&mut it);
+    assert_eq!(expect_punct(&mut it), ',');
+    let b = expect_ident(&mut it);
+    assert!(it.next().is_none(), "only two idents can be concatenated");
+    let res = Ident::new(&(a.to_string() + &b.to_string()), b.span());
+    TokenStream::from_iter([TokenTree::Ident(res)])
+}
diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
index 43e07b259a2d56..4f1b44b23e7593 100644
--- a/rust/macros/lib.rs
+++ b/rust/macros/lib.rs
@@ -2,6 +2,7 @@
 
 //! Crate for all kernel procedural macros.
 
+mod concat_idents;
 mod helpers;
 mod module;
 mod vtable;
@@ -144,3 +145,46 @@ pub fn module(ts: TokenStream) -> TokenStream {
 pub fn vtable(attr: TokenStream, ts: TokenStream) -> TokenStream {
     vtable::vtable(attr, ts)
 }
+
+/// Concatenate two identifiers.
+///
+/// This is useful in macros that need to declare or reference items with names
+/// starting with a fixed prefix and ending in a user specified name. The resulting
+/// identifier has the span of the second argument.
+///
+/// # Examples
+///
+/// ```ignore
+/// use kernel::macro::concat_idents;
+///
+/// macro_rules! pub_no_prefix {
+///     ($prefix:ident, $($newname:ident),+) => {
+///         $(pub(crate) const $newname: u32 = kernel::macros::concat_idents!($prefix, $newname);)+
+///     };
+/// }
+///
+/// pub_no_prefix!(
+///     binder_driver_return_protocol_,
+///     BR_OK,
+///     BR_ERROR,
+///     BR_TRANSACTION,
+///     BR_REPLY,
+///     BR_DEAD_REPLY,
+///     BR_TRANSACTION_COMPLETE,
+///     BR_INCREFS,
+///     BR_ACQUIRE,
+///     BR_RELEASE,
+///     BR_DECREFS,
+///     BR_NOOP,
+///     BR_SPAWN_LOOPER,
+///     BR_DEAD_BINDER,
+///     BR_CLEAR_DEATH_NOTIFICATION_DONE,
+///     BR_FAILED_REPLY
+/// );
+///
+/// assert_eq!(BR_OK, binder_driver_return_protocol_BR_OK);
+/// ```
+#[proc_macro]
+pub fn concat_idents(ts: TokenStream) -> TokenStream {
+    concat_idents::concat_idents(ts)
+}
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index a9e6b51485b234..86c5260631c9b7 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -275,7 +275,7 @@ $(obj)/%.lst: $(src)/%.c FORCE
 # Compile Rust sources (.rs)
 # ---------------------------------------------------------------------------
 
-rust_allowed_features := allocator_api,bench_black_box,concat_idents,core_ffi_c,generic_associated_types,const_ptr_offset_from,const_refs_to_cell
+rust_allowed_features := allocator_api,bench_black_box,core_ffi_c,generic_associated_types,const_ptr_offset_from,const_refs_to_cell
 
 rust_common_cmd = \
 	RUST_MODFILE=$(modfile) $(RUSTC_OR_CLIPPY) $(rust_flags) \