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, 353 insertions, 0 deletions

diff --git a/drivers/input/mouse/lifebook.c b/drivers/input/mouse/lifebook.c
new file mode 100644
index 000000000..ef11b7b19
--- /dev/null
+++ b/drivers/input/mouse/lifebook.c
@@ -0,0 +1,353 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Fujitsu B-series Lifebook PS/2 TouchScreen driver
+ *
+ * Copyright (c) 2005 Vojtech Pavlik <vojtech@suse.cz>
+ * Copyright (c) 2005 Kenan Esau <kenan.esau@conan.de>
+ *
+ * TouchScreen detection, absolute mode setting and packet layout is taken from
+ * Harald Hoyer's description of the device.
+ */
+
+#include <linux/input.h>
+#include <linux/serio.h>
+#include <linux/libps2.h>
+#include <linux/dmi.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include "psmouse.h"
+#include "lifebook.h"
+
+struct lifebook_data {
+	struct input_dev *dev2;		/* Relative device */
+	char phys[32];
+};
+
+static bool lifebook_present;
+
+static const char *desired_serio_phys;
+
+static int lifebook_limit_serio3(const struct dmi_system_id *d)
+{
+	desired_serio_phys = "isa0060/serio3";
+	return 1;
+}
+
+static bool lifebook_use_6byte_proto;
+
+static int lifebook_set_6byte_proto(const struct dmi_system_id *d)
+{
+	lifebook_use_6byte_proto = true;
+	return 1;
+}
+
+static const struct dmi_system_id lifebook_dmi_table[] __initconst = {
+	{
+		/* FLORA-ie 55mi */
+		.matches = {
+			DMI_MATCH(DMI_PRODUCT_NAME, "FLORA-ie 55mi"),
+		},
+	},
+	{
+		/* LifeBook B */
+		.matches = {
+			DMI_MATCH(DMI_PRODUCT_NAME, "Lifebook B Series"),
+		},
+	},
+	{
+		/* LifeBook B */
+		.matches = {
+			DMI_MATCH(DMI_PRODUCT_NAME, "LifeBook B Series"),
+		},
+	},
+	{
+		/* Lifebook B */
+		.matches = {
+			DMI_MATCH(DMI_PRODUCT_NAME, "LIFEBOOK B Series"),
+		},
+	},
+	{
+		/* Lifebook B-2130 */
+		.matches = {
+			DMI_MATCH(DMI_BOARD_NAME, "ZEPHYR"),
+		},
+	},
+	{
+		/* Lifebook B213x/B2150 */
+		.matches = {
+			DMI_MATCH(DMI_PRODUCT_NAME, "LifeBook B2131/B2133/B2150"),
+		},
+	},
+	{
+		/* Zephyr */
+		.matches = {
+			DMI_MATCH(DMI_PRODUCT_NAME, "ZEPHYR"),
+		},
+	},
+	{
+		/* Panasonic CF-18 */
+		.matches = {
+			DMI_MATCH(DMI_PRODUCT_NAME, "CF-18"),
+		},
+		.callback = lifebook_limit_serio3,
+	},
+	{
+		/* Panasonic CF-28 */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Matsushita"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "CF-28"),
+		},
+		.callback = lifebook_set_6byte_proto,
+	},
+	{
+		/* Panasonic CF-29 */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Matsushita"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "CF-29"),
+		},
+		.callback = lifebook_set_6byte_proto,
+	},
+	{
+		/* Panasonic CF-72 */
+		.matches = {
+			DMI_MATCH(DMI_PRODUCT_NAME, "CF-72"),
+		},
+		.callback = lifebook_set_6byte_proto,
+	},
+	{
+		/* Lifebook B142 */
+		.matches = {
+			DMI_MATCH(DMI_PRODUCT_NAME, "LifeBook B142"),
+		},
+	},
+	{ }
+};
+
+void __init lifebook_module_init(void)
+{
+	lifebook_present = dmi_check_system(lifebook_dmi_table);
+}
+
+static psmouse_ret_t lifebook_process_byte(struct psmouse *psmouse)
+{
+	struct lifebook_data *priv = psmouse->private;
+	struct input_dev *dev1 = psmouse->dev;
+	struct input_dev *dev2 = priv ? priv->dev2 : NULL;
+	u8 *packet = psmouse->packet;
+	bool relative_packet = packet[0] & 0x08;
+
+	if (relative_packet || !lifebook_use_6byte_proto) {
+		if (psmouse->pktcnt != 3)
+			return PSMOUSE_GOOD_DATA;
+	} else {
+		switch (psmouse->pktcnt) {
+		case 1:
+			return (packet[0] & 0xf8) == 0x00 ?
+				PSMOUSE_GOOD_DATA : PSMOUSE_BAD_DATA;
+		case 2:
+			return PSMOUSE_GOOD_DATA;
+		case 3:
+			return ((packet[2] & 0x30) << 2) == (packet[2] & 0xc0) ?
+				PSMOUSE_GOOD_DATA : PSMOUSE_BAD_DATA;
+		case 4:
+			return (packet[3] & 0xf8) == 0xc0 ?
+				PSMOUSE_GOOD_DATA : PSMOUSE_BAD_DATA;
+		case 5:
+			return (packet[4] & 0xc0) == (packet[2] & 0xc0) ?
+				PSMOUSE_GOOD_DATA : PSMOUSE_BAD_DATA;
+		case 6:
+			if (((packet[5] & 0x30) << 2) != (packet[5] & 0xc0))
+				return PSMOUSE_BAD_DATA;
+			if ((packet[5] & 0xc0) != (packet[1] & 0xc0))
+				return PSMOUSE_BAD_DATA;
+			break; /* report data */
+		}
+	}
+
+	if (relative_packet) {
+		if (!dev2)
+			psmouse_warn(psmouse,
+				     "got relative packet but no relative device set up\n");
+	} else {
+		if (lifebook_use_6byte_proto) {
+			input_report_abs(dev1, ABS_X,
+				((packet[1] & 0x3f) << 6) | (packet[2] & 0x3f));
+			input_report_abs(dev1, ABS_Y,
+				4096 - (((packet[4] & 0x3f) << 6) | (packet[5] & 0x3f)));
+		} else {
+			input_report_abs(dev1, ABS_X,
+				(packet[1] | ((packet[0] & 0x30) << 4)));
+			input_report_abs(dev1, ABS_Y,
+				1024 - (packet[2] | ((packet[0] & 0xC0) << 2)));
+		}
+		input_report_key(dev1, BTN_TOUCH, packet[0] & 0x04);
+		input_sync(dev1);
+	}
+
+	if (dev2) {
+		if (relative_packet)
+			psmouse_report_standard_motion(dev2, packet);
+
+		psmouse_report_standard_buttons(dev2, packet[0]);
+		input_sync(dev2);
+	}
+
+	return PSMOUSE_FULL_PACKET;
+}
+
+static int lifebook_absolute_mode(struct psmouse *psmouse)
+{
+	struct ps2dev *ps2dev = &psmouse->ps2dev;
+	u8 param;
+	int error;
+
+	error = psmouse_reset(psmouse);
+	if (error)
+		return error;
+
+	/*
+	 * Enable absolute output -- ps2_command fails always but if
+	 * you leave this call out the touchscreen will never send
+	 * absolute coordinates
+	 */
+	param = lifebook_use_6byte_proto ? 0x08 : 0x07;
+	ps2_command(ps2dev, &param, PSMOUSE_CMD_SETRES);
+
+	return 0;
+}
+
+static void lifebook_relative_mode(struct psmouse *psmouse)
+{
+	struct ps2dev *ps2dev = &psmouse->ps2dev;
+	u8 param = 0x06;
+
+	ps2_command(ps2dev, &param, PSMOUSE_CMD_SETRES);
+}
+
+static void lifebook_set_resolution(struct psmouse *psmouse, unsigned int resolution)
+{
+	static const u8 params[] = { 0, 1, 2, 2, 3 };
+	u8 p;
+
+	if (resolution == 0 || resolution > 400)
+		resolution = 400;
+
+	p = params[resolution / 100];
+	ps2_command(&psmouse->ps2dev, &p, PSMOUSE_CMD_SETRES);
+	psmouse->resolution = 50 << p;
+}
+
+static void lifebook_disconnect(struct psmouse *psmouse)
+{
+	struct lifebook_data *priv = psmouse->private;
+
+	psmouse_reset(psmouse);
+	if (priv) {
+		input_unregister_device(priv->dev2);
+		kfree(priv);
+	}
+	psmouse->private = NULL;
+}
+
+int lifebook_detect(struct psmouse *psmouse, bool set_properties)
+{
+	if (!lifebook_present)
+		return -ENXIO;
+
+	if (desired_serio_phys &&
+	    strcmp(psmouse->ps2dev.serio->phys, desired_serio_phys))
+		return -ENXIO;
+
+	if (set_properties) {
+		psmouse->vendor = "Fujitsu";
+		psmouse->name = "Lifebook TouchScreen";
+	}
+
+	return 0;
+}
+
+static int lifebook_create_relative_device(struct psmouse *psmouse)
+{
+	struct input_dev *dev2;
+	struct lifebook_data *priv;
+	int error = -ENOMEM;
+
+	priv = kzalloc_obj(*priv);
+	dev2 = input_allocate_device();
+	if (!priv || !dev2)
+		goto err_out;
+
+	priv->dev2 = dev2;
+	scnprintf(priv->phys, sizeof(priv->phys),
+		  "%s/input1", psmouse->ps2dev.serio->phys);
+
+	dev2->phys = priv->phys;
+	dev2->name = "LBPS/2 Fujitsu Lifebook Touchpad";
+	dev2->id.bustype = BUS_I8042;
+	dev2->id.vendor  = 0x0002;
+	dev2->id.product = PSMOUSE_LIFEBOOK;
+	dev2->id.version = 0x0000;
+	dev2->dev.parent = &psmouse->ps2dev.serio->dev;
+
+	input_set_capability(dev2, EV_REL, REL_X);
+	input_set_capability(dev2, EV_REL, REL_Y);
+	input_set_capability(dev2, EV_KEY, BTN_LEFT);
+	input_set_capability(dev2, EV_KEY, BTN_RIGHT);
+
+	error = input_register_device(priv->dev2);
+	if (error)
+		goto err_out;
+
+	psmouse->private = priv;
+	return 0;
+
+ err_out:
+	input_free_device(dev2);
+	kfree(priv);
+	return error;
+}
+
+int lifebook_init(struct psmouse *psmouse)
+{
+	struct input_dev *dev1 = psmouse->dev;
+	int max_coord = lifebook_use_6byte_proto ? 4096 : 1024;
+	int error;
+
+	error = lifebook_absolute_mode(psmouse);
+	if (error)
+		return error;
+
+	/* Clear default capabilities */
+	bitmap_zero(dev1->evbit, EV_CNT);
+	bitmap_zero(dev1->relbit, REL_CNT);
+	bitmap_zero(dev1->keybit, KEY_CNT);
+
+	input_set_capability(dev1, EV_KEY, BTN_TOUCH);
+	input_set_abs_params(dev1, ABS_X, 0, max_coord, 0, 0);
+	input_set_abs_params(dev1, ABS_Y, 0, max_coord, 0, 0);
+
+	if (!desired_serio_phys) {
+		error = lifebook_create_relative_device(psmouse);
+		if (error) {
+			lifebook_relative_mode(psmouse);
+			return error;
+		}
+	}
+
+	psmouse->protocol_handler = lifebook_process_byte;
+	psmouse->set_resolution = lifebook_set_resolution;
+	psmouse->disconnect = lifebook_disconnect;
+	psmouse->reconnect  = lifebook_absolute_mode;
+
+	psmouse->model = lifebook_use_6byte_proto ? 6 : 3;
+
+	/*
+	 * Use packet size = 3 even when using 6-byte protocol because
+	 * that's what POLL will return on Lifebooks (according to spec).
+	 */
+	psmouse->pktsize = 3;
+
+	return 0;
+}
+