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, 173 insertions, 0 deletions

diff --git a/drivers/usb/serial/usb-serial-simple.c b/drivers/usb/serial/usb-serial-simple.c
new file mode 100644
index 000000000..a0afaf254
--- /dev/null
+++ b/drivers/usb/serial/usb-serial-simple.c
@@ -0,0 +1,173 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * USB Serial "Simple" driver
+ *
+ * Copyright (C) 2001-2006,2008,2013 Greg Kroah-Hartman <greg@kroah.com>
+ * Copyright (C) 2005 Arthur Huillet (ahuillet@users.sf.net)
+ * Copyright (C) 2005 Thomas Hergenhahn <thomas.hergenhahn@suse.de>
+ * Copyright (C) 2009 Outpost Embedded, LLC
+ * Copyright (C) 2010 Zilogic Systems <code@zilogic.com>
+ * Copyright (C) 2013 Wei Shuai <cpuwolf@gmail.com>
+ * Copyright (C) 2013 Linux Foundation
+ */
+
+#include <linux/kernel.h>
+#include <linux/tty.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+#define DEVICE_N(vendor, IDS, nport)				\
+static const struct usb_device_id vendor##_id_table[] = {	\
+	IDS(),							\
+	{ },							\
+};								\
+static struct usb_serial_driver vendor##_device = {		\
+	.driver = {						\
+		.name =		#vendor,			\
+	},							\
+	.id_table =		vendor##_id_table,		\
+	.num_ports =		nport,				\
+};
+
+#define DEVICE(vendor, IDS)	DEVICE_N(vendor, IDS, 1)
+
+/* Medtronic CareLink USB driver */
+#define CARELINK_IDS()			\
+	{ USB_DEVICE(0x0a21, 0x8001) }	/* MMT-7305WW */
+DEVICE(carelink, CARELINK_IDS);
+
+/* Infineon Flashloader driver */
+#define FLASHLOADER_IDS()		\
+	{ USB_DEVICE_INTERFACE_CLASS(0x058b, 0x0041, USB_CLASS_CDC_DATA) }, \
+	{ USB_DEVICE(0x8087, 0x0716) }, \
+	{ USB_DEVICE(0x8087, 0x0801) }
+DEVICE(flashloader, FLASHLOADER_IDS);
+
+/* Funsoft Serial USB driver */
+#define FUNSOFT_IDS()			\
+	{ USB_DEVICE(0x1404, 0xcddc) }
+DEVICE(funsoft, FUNSOFT_IDS);
+
+/* Google Serial USB SubClass */
+#define GOOGLE_IDS()						\
+	{ USB_VENDOR_AND_INTERFACE_INFO(0x18d1,			\
+					USB_CLASS_VENDOR_SPEC,	\
+					0x50,			\
+					0x01) }
+DEVICE(google, GOOGLE_IDS);
+
+/* HP4x (48/49) Generic Serial driver */
+#define HP4X_IDS()			\
+	{ USB_DEVICE(0x03f0, 0x0121) }
+DEVICE(hp4x, HP4X_IDS);
+
+/* KAUFMANN RKS+CAN VCP */
+#define KAUFMANN_IDS()			\
+	{ USB_DEVICE(0x16d0, 0x0870) }
+DEVICE(kaufmann, KAUFMANN_IDS);
+
+/* Libtransistor USB console */
+#define LIBTRANSISTOR_IDS()			\
+	{ USB_DEVICE(0x1209, 0x8b00) }
+DEVICE(libtransistor, LIBTRANSISTOR_IDS);
+
+/* Motorola USB Phone driver */
+#define MOTO_IDS()			\
+	{ USB_DEVICE(0x05c6, 0x3197) },	/* unknown Motorola phone */	\
+	{ USB_DEVICE(0x0c44, 0x0022) },	/* unknown Motorola phone */	\
+	{ USB_DEVICE(0x22b8, 0x2a64) },	/* Motorola KRZR K1m */		\
+	{ USB_DEVICE(0x22b8, 0x2c84) },	/* Motorola VE240 phone */	\
+	{ USB_DEVICE(0x22b8, 0x2c64) }	/* Motorola V950 phone */
+DEVICE(moto_modem, MOTO_IDS);
+
+/* Motorola Tetra driver */
+#define MOTOROLA_TETRA_IDS()			\
+	{ USB_DEVICE(0x0cad, 0x9011) },	/* Motorola Solutions TETRA PEI */ \
+	{ USB_DEVICE(0x0cad, 0x9012) },	/* MTP6550 */ \
+	{ USB_DEVICE(0x0cad, 0x9013) },	/* MTP3xxx */ \
+	{ USB_DEVICE(0x0cad, 0x9015) },	/* MTP85xx */ \
+	{ USB_DEVICE(0x0cad, 0x9016) }	/* TPG2200 */
+DEVICE(motorola_tetra, MOTOROLA_TETRA_IDS);
+
+/* Nokia mobile phone driver */
+#define NOKIA_IDS()			\
+	{ USB_DEVICE(0x0421, 0x069a) }	/* Nokia 130 (RM-1035) */
+DEVICE(nokia, NOKIA_IDS);
+
+/* Novatel Wireless GPS driver */
+#define NOVATEL_IDS()			\
+	{ USB_DEVICE(0x09d7, 0x0100) }	/* NovAtel FlexPack GPS */
+DEVICE_N(novatel_gps, NOVATEL_IDS, 3);
+
+/* OWON electronic test and measurement equipment driver */
+#define OWON_IDS()			\
+	{ USB_DEVICE(0x5345, 0x1234) } /* HDS200 oscilloscopes and others */
+DEVICE(owon, OWON_IDS);
+
+/* Siemens USB/MPI adapter */
+#define SIEMENS_IDS()			\
+	{ USB_DEVICE(0x908, 0x0004) }
+DEVICE(siemens_mpi, SIEMENS_IDS);
+
+/* Suunto ANT+ USB Driver */
+#define SUUNTO_IDS()			\
+	{ USB_DEVICE(0x0fcf, 0x1008) },	\
+	{ USB_DEVICE(0x0fcf, 0x1009) } /* Dynastream ANT USB-m Stick */
+DEVICE(suunto, SUUNTO_IDS);
+
+/* ViVOpay USB Serial Driver */
+#define VIVOPAY_IDS()			\
+	{ USB_DEVICE(0x1d5f, 0x1004) }	/* ViVOpay 8800 */
+DEVICE(vivopay, VIVOPAY_IDS);
+
+/* ZIO Motherboard USB driver */
+#define ZIO_IDS()			\
+	{ USB_DEVICE(0x1CBE, 0x0103) }
+DEVICE(zio, ZIO_IDS);
+
+/* All of the above structures mushed into two lists */
+static struct usb_serial_driver * const serial_drivers[] = {
+	&carelink_device,
+	&flashloader_device,
+	&funsoft_device,
+	&google_device,
+	&hp4x_device,
+	&kaufmann_device,
+	&libtransistor_device,
+	&moto_modem_device,
+	&motorola_tetra_device,
+	&nokia_device,
+	&novatel_gps_device,
+	&owon_device,
+	&siemens_mpi_device,
+	&suunto_device,
+	&vivopay_device,
+	&zio_device,
+	NULL
+};
+
+static const struct usb_device_id id_table[] = {
+	CARELINK_IDS(),
+	FLASHLOADER_IDS(),
+	FUNSOFT_IDS(),
+	GOOGLE_IDS(),
+	HP4X_IDS(),
+	KAUFMANN_IDS(),
+	LIBTRANSISTOR_IDS(),
+	MOTO_IDS(),
+	MOTOROLA_TETRA_IDS(),
+	NOKIA_IDS(),
+	NOVATEL_IDS(),
+	OWON_IDS(),
+	SIEMENS_IDS(),
+	SUUNTO_IDS(),
+	VIVOPAY_IDS(),
+	ZIO_IDS(),
+	{ },
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+module_usb_serial_driver(serial_drivers, id_table);
+MODULE_DESCRIPTION("USB Serial 'Simple' driver");
+MODULE_LICENSE("GPL v2");