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, 204 insertions, 0 deletions

diff --git a/drivers/hid/hid-universal-pidff.c b/drivers/hid/hid-universal-pidff.c
new file mode 100644
index 000000000..549dac555
--- /dev/null
+++ b/drivers/hid/hid-universal-pidff.c
@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * HID UNIVERSAL PIDFF
+ * hid-pidff wrapper for PID-enabled devices
+ * Handles device reports, quirks and extends usable button range
+ *
+ * Copyright (c) 2024, 2025 Oleg Makarenko
+ * Copyright (c) 2024, 2025 Tomasz Pakuła
+ */
+
+#include "hid-ids.h"
+#include "usbhid/hid-pidff.h"
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/input-event-codes.h>
+#include <linux/module.h>
+
+#define JOY_RANGE (BTN_DEAD - BTN_JOYSTICK + 1)
+
+/*
+ * Map buttons manually to extend the default joystick button limit
+ */
+static int universal_pidff_input_mapping(struct hid_device *hdev,
+					 struct hid_input *hi,
+					 struct hid_field *field,
+					 struct hid_usage *usage,
+					 unsigned long **bit, int *max)
+{
+	if ((usage->hid & HID_USAGE_PAGE) != HID_UP_BUTTON)
+		return 0;
+
+	if (field->application != HID_GD_JOYSTICK)
+		return 0;
+
+	int button = ((usage->hid - 1) & HID_USAGE);
+	int code = button + BTN_JOYSTICK;
+
+	/* Detect the end of JOYSTICK buttons range */
+	if (code > BTN_DEAD)
+		code = button + KEY_NEXT_FAVORITE - JOY_RANGE;
+
+	/*
+	 * Map overflowing buttons to KEY_RESERVED to not ignore
+	 * them and let them still trigger MSC_SCAN
+	 */
+	if (code > KEY_MAX)
+		code = KEY_RESERVED;
+
+	hid_map_usage(hi, usage, bit, max, EV_KEY, code);
+	hid_dbg(hdev, "Button %d: usage %d", button, code);
+	return 1;
+}
+
+/*
+ * Check if the device is PID and initialize it
+ * Add quirks after initialisation
+ */
+static int universal_pidff_probe(struct hid_device *hdev,
+				 const struct hid_device_id *id)
+{
+	int i, error;
+
+	error = hid_parse(hdev);
+	if (error) {
+		hid_err(hdev, "HID parse failed\n");
+		goto err;
+	}
+
+	error = hid_hw_start(hdev, HID_CONNECT_DEFAULT & ~HID_CONNECT_FF);
+	if (error) {
+		hid_err(hdev, "HID hw start failed\n");
+		goto err;
+	}
+
+	/* Check if device contains PID usage page */
+	error = 1;
+	for (i = 0; i < hdev->collection_size; i++)
+		if ((hdev->collection[i].usage & HID_USAGE_PAGE) == HID_UP_PID) {
+			error = 0;
+			hid_dbg(hdev, "PID usage page found\n");
+			break;
+		}
+
+	/*
+	 * Do not fail as this might be the second "device"
+	 * just for additional buttons/axes. Exit cleanly if force
+	 * feedback usage page wasn't found (included devices were
+	 * tested and confirmed to be USB PID after all).
+	 */
+	if (error) {
+		hid_dbg(hdev, "PID usage page not found in the descriptor\n");
+		return 0;
+	}
+
+	/* Check if HID_PID support is enabled */
+	int (*init_function)(struct hid_device *, u32);
+
+	init_function = hid_pidff_init_with_quirks;
+	if (!init_function) {
+		hid_warn(hdev, "HID_PID support not enabled!\n");
+		return 0;
+	}
+
+	error = init_function(hdev, id->driver_data);
+	if (error) {
+		hid_warn(hdev, "Error initialising force feedback\n");
+		goto err;
+	}
+
+	hid_info(hdev, "Universal pidff driver loaded successfully!");
+
+	return 0;
+err:
+	return error;
+}
+
+static int universal_pidff_input_configured(struct hid_device *hdev,
+					    struct hid_input *hidinput)
+{
+	int axis;
+	struct input_dev *input = hidinput->input;
+
+	if (!input->absinfo)
+		return 0;
+
+	/* Decrease fuzz and deadzone on available axes */
+	for (axis = ABS_X; axis <= ABS_BRAKE; axis++) {
+		if (!test_bit(axis, input->absbit))
+			continue;
+
+		input_set_abs_params(input, axis, input->absinfo[axis].minimum,
+				     input->absinfo[axis].maximum,
+				     axis == ABS_X ? 0 : 8, 0);
+	}
+
+	/* Remove fuzz and deadzone from the second joystick axis */
+	if (hdev->vendor == USB_VENDOR_ID_FFBEAST &&
+	    hdev->product == USB_DEVICE_ID_FFBEAST_JOYSTICK)
+		input_set_abs_params(input, ABS_Y,
+				     input->absinfo[ABS_Y].minimum,
+				     input->absinfo[ABS_Y].maximum, 0, 0);
+
+	return 0;
+}
+
+static const struct hid_device_id universal_pidff_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R3),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R3_2),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R5),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R5_2),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R9),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R9_2),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R12),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R12_2),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R16_R21),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R16_R21_2),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_CAMMUS, USB_DEVICE_ID_CAMMUS_C5) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_CAMMUS, USB_DEVICE_ID_CAMMUS_C12) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_VRS, USB_DEVICE_ID_VRS_DFP),
+	  .driver_data = HID_PIDFF_QUIRK_PERMISSIVE_CONTROL },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_FFBEAST, USB_DEVICE_ID_FFBEAST_JOYSTICK), },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_FFBEAST, USB_DEVICE_ID_FFBEAST_RUDDER), },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_FFBEAST, USB_DEVICE_ID_FFBEAST_WHEEL) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LITE_STAR, USB_DEVICE_ID_PXN_V10),
+	  .driver_data = HID_PIDFF_QUIRK_PERIODIC_SINE_ONLY },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LITE_STAR, USB_DEVICE_ID_PXN_V12),
+	  .driver_data = HID_PIDFF_QUIRK_PERIODIC_SINE_ONLY },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LITE_STAR, USB_DEVICE_ID_PXN_V12_LITE),
+	  .driver_data = HID_PIDFF_QUIRK_PERIODIC_SINE_ONLY },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LITE_STAR, USB_DEVICE_ID_PXN_V12_LITE_2),
+	  .driver_data = HID_PIDFF_QUIRK_PERIODIC_SINE_ONLY },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LITE_STAR, USB_DEVICE_ID_LITE_STAR_GT987),
+	  .driver_data = HID_PIDFF_QUIRK_PERIODIC_SINE_ONLY },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ASETEK, USB_DEVICE_ID_ASETEK_INVICTA) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ASETEK, USB_DEVICE_ID_ASETEK_FORTE) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ASETEK, USB_DEVICE_ID_ASETEK_LA_PRIMA) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ASETEK, USB_DEVICE_ID_ASETEK_TONY_KANAAN) },
+	{}
+};
+MODULE_DEVICE_TABLE(hid, universal_pidff_devices);
+
+static struct hid_driver universal_pidff = {
+	.name = "hid-universal-pidff",
+	.id_table = universal_pidff_devices,
+	.input_mapping = universal_pidff_input_mapping,
+	.probe = universal_pidff_probe,
+	.input_configured = universal_pidff_input_configured
+};
+module_hid_driver(universal_pidff);
+
+MODULE_DESCRIPTION("Universal driver for USB PID Force Feedback devices");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Oleg Makarenko <oleg@makarenk.ooo>");
+MODULE_AUTHOR("Tomasz Pakuła <tomasz.pakula.oficjalny@gmail.com>");