rust: rbtree: add red-black tree implementation backed by the C version

The rust rbtree exposes a map-like interface over keys and values,
backed by the kernel red-black tree implementation. Values can be
inserted, deleted, and retrieved from a `RBTree` by key.

This base abstraction is used by binder to store key/value
pairs and perform lookups, for example the patch
"[PATCH RFC 03/20] rust_binder: add threading support"
in the binder RFC [1].

Link: https://lore.kernel.org/rust-for-linux/[email protected]/ [1]
Signed-off-by: Wedson Almeida Filho <[email protected]>
Reviewed-by: Alice Ryhl <[email protected]>
Tested-by: Alice Ryhl <[email protected]>
Reviewed-by: Boqun Feng <[email protected]>
Reviewed-by: Benno Lossin <[email protected]>
Signed-off-by: Matt Gilbride <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: wedsonaf

rust/helpers/helpers.c

@@ -15,6 +15,7 @@
 #include "kunit.c"
 #include "mutex.c"
 #include "page.c"
+#include "rbtree.c"
 #include "refcount.c"
 #include "signal.c"
 #include "slab.c"

rust/helpers/rbtree.c

@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/rbtree.h>
+
+void rust_helper_rb_link_node(struct rb_node *node, struct rb_node *parent,
+			      struct rb_node **rb_link)
+{
+	rb_link_node(node, parent, rb_link);
+}

rust/kernel/lib.rs

@@ -43,6 +43,7 @@ pub mod net;
 pub mod page;
 pub mod prelude;
 pub mod print;
+pub mod rbtree;
 mod static_assert;
 #[doc(hidden)]
 pub mod std_vendor;