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, 41 insertions, 0 deletions

diff --git a/drivers/gpib/include/gpibP.h b/drivers/gpib/include/gpibP.h
new file mode 100644
index 000000000..e3938ada3
--- /dev/null
+++ b/drivers/gpib/include/gpibP.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/***************************************************************************
+ *    copyright		   : (C) 2002,2003 by Frank Mori Hess
+ ***************************************************************************/
+
+#ifndef _GPIB_P_H
+#define _GPIB_P_H
+
+#include <linux/types.h>
+
+#include "gpib_types.h"
+#include "gpib_proto.h"
+#include "gpib_cmd.h"
+#include <linux/gpib.h>
+#include <linux/gpib_ioctl.h>
+
+#include <linux/fs.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+
+int gpib_register_driver(struct gpib_interface *interface, struct module *mod);
+void gpib_unregister_driver(struct gpib_interface *interface);
+struct pci_dev *gpib_pci_get_device(const struct gpib_board_config *config, unsigned int vendor_id,
+				    unsigned int device_id, struct pci_dev *from);
+struct pci_dev *gpib_pci_get_subsys(const struct gpib_board_config *config, unsigned int vendor_id,
+				    unsigned int device_id, unsigned int ss_vendor,
+				    unsigned int ss_device, struct pci_dev *from);
+unsigned int num_gpib_events(const struct gpib_event_queue *queue);
+int push_gpib_event(struct gpib_board *board, short event_type);
+int pop_gpib_event(struct gpib_board *board, struct gpib_event_queue *queue, short *event_type);
+int gpib_request_pseudo_irq(struct gpib_board *board, irqreturn_t (*handler)(int, void *));
+void gpib_free_pseudo_irq(struct gpib_board *board);
+int gpib_match_device_path(struct device *dev, const char *device_path_in);
+
+extern struct gpib_board board_array[GPIB_MAX_NUM_BOARDS];
+
+extern struct list_head registered_drivers;
+
+#endif	// _GPIB_P_H
+