kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 75 insertions, 0 deletions

diff --git a/net/bluetooth/mgmt_util.h b/net/bluetooth/mgmt_util.h
new file mode 100644
index 000000000..20810cf06
--- /dev/null
+++ b/net/bluetooth/mgmt_util.h
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+   BlueZ - Bluetooth protocol stack for Linux
+   Copyright (C) 2015  Intel Coropration
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+   OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.
+   IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) AND AUTHOR(S) BE LIABLE FOR ANY
+   CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES
+   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+   ALL LIABILITY, INCLUDING LIABILITY FOR INFRINGEMENT OF ANY PATENTS,
+   COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS, RELATING TO USE OF THIS
+   SOFTWARE IS DISCLAIMED.
+*/
+
+struct mgmt_mesh_tx {
+	struct list_head list;
+	int index;
+	size_t param_len;
+	struct sock *sk;
+	u8 handle;
+	u8 instance;
+	u8 param[sizeof(struct mgmt_cp_mesh_send) + 31];
+};
+
+struct mgmt_pending_cmd {
+	struct list_head list;
+	u16 opcode;
+	struct hci_dev *hdev;
+	void *param;
+	size_t param_len;
+	struct sock *sk;
+	struct sk_buff *skb;
+	void *user_data;
+	int (*cmd_complete)(struct mgmt_pending_cmd *cmd, u8 status);
+};
+
+struct sk_buff *mgmt_alloc_skb(struct hci_dev *hdev, u16 opcode,
+			       unsigned int size);
+int mgmt_send_event_skb(unsigned short channel, struct sk_buff *skb, int flag,
+			struct sock *skip_sk);
+int mgmt_send_event(u16 event, struct hci_dev *hdev, unsigned short channel,
+		    void *data, u16 data_len, int flag, struct sock *skip_sk);
+int mgmt_cmd_status(struct sock *sk, u16 index, u16 cmd, u8 status);
+int mgmt_cmd_complete(struct sock *sk, u16 index, u16 cmd, u8 status,
+		      void *rp, size_t rp_len);
+
+struct mgmt_pending_cmd *mgmt_pending_find(unsigned short channel, u16 opcode,
+					   struct hci_dev *hdev);
+void mgmt_pending_foreach(u16 opcode, struct hci_dev *hdev, bool remove,
+			  void (*cb)(struct mgmt_pending_cmd *cmd, void *data),
+			  void *data);
+struct mgmt_pending_cmd *mgmt_pending_add(struct sock *sk, u16 opcode,
+					  struct hci_dev *hdev,
+					  void *data, u16 len);
+struct mgmt_pending_cmd *mgmt_pending_new(struct sock *sk, u16 opcode,
+					  struct hci_dev *hdev,
+					  void *data, u16 len);
+void mgmt_pending_free(struct mgmt_pending_cmd *cmd);
+void mgmt_pending_remove(struct mgmt_pending_cmd *cmd);
+bool __mgmt_pending_listed(struct hci_dev *hdev, struct mgmt_pending_cmd *cmd);
+bool mgmt_pending_listed(struct hci_dev *hdev, struct mgmt_pending_cmd *cmd);
+bool mgmt_pending_valid(struct hci_dev *hdev, struct mgmt_pending_cmd *cmd);
+void mgmt_mesh_foreach(struct hci_dev *hdev,
+		       void (*cb)(struct mgmt_mesh_tx *mesh_tx, void *data),
+		       void *data, struct sock *sk);
+struct mgmt_mesh_tx *mgmt_mesh_find(struct hci_dev *hdev, u8 handle);
+struct mgmt_mesh_tx *mgmt_mesh_next(struct hci_dev *hdev, struct sock *sk);
+struct mgmt_mesh_tx *mgmt_mesh_add(struct sock *sk, struct hci_dev *hdev,
+				   void *data, u16 len);
+void mgmt_mesh_remove(struct mgmt_mesh_tx *mesh_tx);