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, 66 insertions, 0 deletions

diff --git a/drivers/tty/ipwireless/main.h b/drivers/tty/ipwireless/main.h
new file mode 100644
index 000000000..a5728a5b3
--- /dev/null
+++ b/drivers/tty/ipwireless/main.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * IPWireless 3G PCMCIA Network Driver
+ *
+ * Original code
+ *   by Stephen Blackheath <stephen@blacksapphire.com>,
+ *      Ben Martel <benm@symmetric.co.nz>
+ *
+ * Copyrighted as follows:
+ *   Copyright (C) 2004 by Symmetric Systems Ltd (NZ)
+ *
+ * Various driver changes and rewrites, port to new kernels
+ *   Copyright (C) 2006-2007 Jiri Kosina
+ *
+ * Misc code cleanups and updates
+ *   Copyright (C) 2007 David Sterba
+ */
+
+#ifndef _IPWIRELESS_CS_H_
+#define _IPWIRELESS_CS_H_
+
+#include <linux/sched.h>
+#include <linux/types.h>
+
+#include <pcmcia/cistpl.h>
+#include <pcmcia/ds.h>
+
+#include "hardware.h"
+
+#define IPWIRELESS_PCCARD_NAME		"ipwireless"
+#define IPWIRELESS_PCMCIA_VERSION	"1.1"
+#define IPWIRELESS_PCMCIA_AUTHOR        \
+	"Stephen Blackheath, Ben Martel, Jiri Kosina and David Sterba"
+
+#define IPWIRELESS_TX_QUEUE_SIZE  262144
+#define IPWIRELESS_RX_QUEUE_SIZE  262144
+
+#define IPWIRELESS_STATE_DEBUG
+
+struct ipw_hardware;
+struct ipw_network;
+struct ipw_tty;
+
+struct ipw_dev {
+	struct pcmcia_device *link;
+	int is_v2_card;
+
+	void __iomem *attr_memory;
+
+	void __iomem *common_memory;
+
+	/* Hardware context */
+	struct ipw_hardware *hardware;
+	/* Network layer context */
+	struct ipw_network *network;
+	/* TTY device context */
+	struct ipw_tty *tty;
+	struct work_struct work_reboot;
+};
+
+/* Module parametres */
+extern int ipwireless_debug;
+extern int ipwireless_loopback;
+extern int ipwireless_out_queue;
+
+#endif