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, 63 insertions, 0 deletions

diff --git a/drivers/tty/ipwireless/hardware.h b/drivers/tty/ipwireless/hardware.h
new file mode 100644
index 000000000..e524a8fcc
--- /dev/null
+++ b/drivers/tty/ipwireless/hardware.h
@@ -0,0 +1,63 @@
+/* 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_HARDWARE_H_
+#define _IPWIRELESS_CS_HARDWARE_H_
+
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+
+#define IPW_CONTROL_LINE_CTS 0x0001
+#define IPW_CONTROL_LINE_DCD 0x0002
+#define IPW_CONTROL_LINE_DSR 0x0004
+#define IPW_CONTROL_LINE_RI  0x0008
+#define IPW_CONTROL_LINE_DTR 0x0010
+#define IPW_CONTROL_LINE_RTS 0x0020
+
+struct ipw_hardware;
+struct ipw_network;
+
+struct ipw_hardware *ipwireless_hardware_create(void);
+void ipwireless_hardware_free(struct ipw_hardware *hw);
+irqreturn_t ipwireless_interrupt(int irq, void *dev_id);
+int ipwireless_set_DTR(struct ipw_hardware *hw, unsigned int channel_idx,
+		int state);
+int ipwireless_set_RTS(struct ipw_hardware *hw, unsigned int channel_idx,
+		int state);
+int ipwireless_send_packet(struct ipw_hardware *hw,
+			    unsigned int channel_idx,
+			    const unsigned char *data,
+			    unsigned int length,
+			    void (*packet_sent_callback) (void *cb,
+							  unsigned int length),
+			    void *sent_cb_data);
+void ipwireless_associate_network(struct ipw_hardware *hw,
+		struct ipw_network *net);
+void ipwireless_stop_interrupts(struct ipw_hardware *hw);
+void ipwireless_init_hardware_v1(struct ipw_hardware *hw,
+				 unsigned int base_port,
+				 void __iomem *attr_memory,
+				 void __iomem *common_memory,
+				 int is_v2_card,
+				 void (*reboot_cb) (void *data),
+				 void *reboot_cb_data);
+void ipwireless_init_hardware_v2_v3(struct ipw_hardware *hw);
+void ipwireless_sleep(unsigned int tenths);
+
+#endif