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, 32 insertions, 0 deletions

diff --git a/include/net/bluetooth/iso.h b/include/net/bluetooth/iso.h
new file mode 100644
index 000000000..3f4fe8b78
--- /dev/null
+++ b/include/net/bluetooth/iso.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * BlueZ - Bluetooth protocol stack for Linux
+ *
+ * Copyright (C) 2022 Intel Corporation
+ */
+
+#ifndef __ISO_H
+#define __ISO_H
+
+/* ISO defaults */
+#define ISO_DEFAULT_MTU		251
+#define ISO_MAX_NUM_BIS		0x1f
+
+/* ISO socket broadcast address */
+struct sockaddr_iso_bc {
+	bdaddr_t	bc_bdaddr;
+	__u8		bc_bdaddr_type;
+	__u8		bc_sid;
+	__u8		bc_num_bis;
+	__u8		bc_bis[ISO_MAX_NUM_BIS];
+};
+
+/* ISO socket address */
+struct sockaddr_iso {
+	sa_family_t	iso_family;
+	bdaddr_t	iso_bdaddr;
+	__u8		iso_bdaddr_type;
+	struct sockaddr_iso_bc iso_bc[];
+};
+
+#endif /* __ISO_H */