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, 408 insertions, 0 deletions

diff --git a/drivers/input/joystick/grip.c b/drivers/input/joystick/grip.c
new file mode 100644
index 000000000..2a3f768a7
--- /dev/null
+++ b/drivers/input/joystick/grip.c
@@ -0,0 +1,408 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (c) 1998-2001 Vojtech Pavlik
+ */
+
+/*
+ * Gravis/Kensington GrIP protocol joystick and gamepad driver for Linux
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/gameport.h>
+#include <linux/input.h>
+#include <linux/jiffies.h>
+
+#define DRIVER_DESC	"Gravis GrIP protocol joystick driver"
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+#define GRIP_MODE_GPP		1
+#define GRIP_MODE_BD		2
+#define GRIP_MODE_XT		3
+#define GRIP_MODE_DC		4
+
+#define GRIP_LENGTH_GPP		24
+#define GRIP_STROBE_GPP		200	/* 200 us */
+#define GRIP_LENGTH_XT		4
+#define GRIP_STROBE_XT		64	/* 64 us */
+#define GRIP_MAX_CHUNKS_XT	10
+#define GRIP_MAX_BITS_XT	30
+
+struct grip {
+	struct gameport *gameport;
+	struct input_dev *dev[2];
+	unsigned char mode[2];
+	int reads;
+	int bads;
+	char phys[2][32];
+};
+
+static int grip_btn_gpp[] = { BTN_START, BTN_SELECT, BTN_TR2, BTN_Y, 0, BTN_TL2, BTN_A, BTN_B, BTN_X, 0, BTN_TL, BTN_TR, -1 };
+static int grip_btn_bd[] = { BTN_THUMB, BTN_THUMB2, BTN_TRIGGER, BTN_TOP, BTN_BASE, -1 };
+static int grip_btn_xt[] = { BTN_TRIGGER, BTN_THUMB, BTN_A, BTN_B, BTN_C, BTN_X, BTN_Y, BTN_Z, BTN_SELECT, BTN_START, BTN_MODE, -1 };
+static int grip_btn_dc[] = { BTN_TRIGGER, BTN_THUMB, BTN_TOP, BTN_TOP2, BTN_BASE, BTN_BASE2, BTN_BASE3, BTN_BASE4, BTN_BASE5, -1 };
+
+static int grip_abs_gpp[] = { ABS_X, ABS_Y, -1 };
+static int grip_abs_bd[] = { ABS_X, ABS_Y, ABS_THROTTLE, ABS_HAT0X, ABS_HAT0Y, -1 };
+static int grip_abs_xt[] = { ABS_X, ABS_Y, ABS_BRAKE, ABS_GAS, ABS_THROTTLE, ABS_HAT0X, ABS_HAT0Y, ABS_HAT1X, ABS_HAT1Y, -1 };
+static int grip_abs_dc[] = { ABS_X, ABS_Y, ABS_RX, ABS_RY, ABS_THROTTLE, ABS_HAT0X, ABS_HAT0Y, -1 };
+
+static char *grip_name[] = { NULL, "Gravis GamePad Pro", "Gravis Blackhawk Digital",
+				"Gravis Xterminator Digital", "Gravis Xterminator DualControl" };
+static int *grip_abs[] = { NULL, grip_abs_gpp, grip_abs_bd, grip_abs_xt, grip_abs_dc };
+static int *grip_btn[] = { NULL, grip_btn_gpp, grip_btn_bd, grip_btn_xt, grip_btn_dc };
+static char grip_anx[] = { 0, 0, 3, 5, 5 };
+static char grip_cen[] = { 0, 0, 2, 2, 4 };
+
+/*
+ * grip_gpp_read_packet() reads a Gravis GamePad Pro packet.
+ */
+
+static int grip_gpp_read_packet(struct gameport *gameport, int shift, unsigned int *data)
+{
+	unsigned long flags;
+	unsigned char u, v;
+	unsigned int t;
+	int i;
+
+	int strobe = gameport_time(gameport, GRIP_STROBE_GPP);
+
+	data[0] = 0;
+	t = strobe;
+	i = 0;
+
+	local_irq_save(flags);
+
+	v = gameport_read(gameport) >> shift;
+
+	do {
+		t--;
+		u = v; v = (gameport_read(gameport) >> shift) & 3;
+		if (~v & u & 1) {
+			data[0] |= (v >> 1) << i++;
+			t = strobe;
+		}
+	} while (i < GRIP_LENGTH_GPP && t > 0);
+
+	local_irq_restore(flags);
+
+	if (i < GRIP_LENGTH_GPP) return -1;
+
+	for (i = 0; i < GRIP_LENGTH_GPP && (data[0] & 0xfe4210) ^ 0x7c0000; i++)
+		data[0] = data[0] >> 1 | (data[0] & 1) << (GRIP_LENGTH_GPP - 1);
+
+	return -(i == GRIP_LENGTH_GPP);
+}
+
+/*
+ * grip_xt_read_packet() reads a Gravis Xterminator packet.
+ */
+
+static int grip_xt_read_packet(struct gameport *gameport, int shift, unsigned int *data)
+{
+	unsigned int i, j, buf, crc;
+	unsigned char u, v, w;
+	unsigned long flags;
+	unsigned int t;
+	char status;
+
+	int strobe = gameport_time(gameport, GRIP_STROBE_XT);
+
+	data[0] = data[1] = data[2] = data[3] = 0;
+	status = buf = i = j = 0;
+	t = strobe;
+
+	local_irq_save(flags);
+
+	v = w = (gameport_read(gameport) >> shift) & 3;
+
+	do {
+		t--;
+		u = (gameport_read(gameport) >> shift) & 3;
+
+		if (u ^ v) {
+
+			if ((u ^ v) & 1) {
+				buf = (buf << 1) | (u >> 1);
+				t = strobe;
+				i++;
+			} else
+
+			if ((((u ^ v) & (v ^ w)) >> 1) & ~(u | v | w) & 1) {
+				if (i == 20) {
+					crc = buf ^ (buf >> 7) ^ (buf >> 14);
+					if (!((crc ^ (0x25cb9e70 >> ((crc >> 2) & 0x1c))) & 0xf)) {
+						data[buf >> 18] = buf >> 4;
+						status |= 1 << (buf >> 18);
+					}
+					j++;
+				}
+				t = strobe;
+				buf = 0;
+				i = 0;
+			}
+			w = v;
+			v = u;
+		}
+
+	} while (status != 0xf && i < GRIP_MAX_BITS_XT && j < GRIP_MAX_CHUNKS_XT && t > 0);
+
+	local_irq_restore(flags);
+
+	return -(status != 0xf);
+}
+
+/*
+ * grip_timer() repeatedly polls the joysticks and generates events.
+ */
+
+static void grip_poll(struct gameport *gameport)
+{
+	struct grip *grip = gameport_get_drvdata(gameport);
+	unsigned int data[GRIP_LENGTH_XT];
+	struct input_dev *dev;
+	int i, j;
+
+	for (i = 0; i < 2; i++) {
+
+		dev = grip->dev[i];
+		if (!dev)
+			continue;
+
+		grip->reads++;
+
+		switch (grip->mode[i]) {
+
+			case GRIP_MODE_GPP:
+
+				if (grip_gpp_read_packet(grip->gameport, (i << 1) + 4, data)) {
+					grip->bads++;
+					break;
+				}
+
+				input_report_abs(dev, ABS_X, ((*data >> 15) & 1) - ((*data >> 16) & 1));
+				input_report_abs(dev, ABS_Y, ((*data >> 13) & 1) - ((*data >> 12) & 1));
+
+				for (j = 0; j < 12; j++)
+					if (grip_btn_gpp[j])
+						input_report_key(dev, grip_btn_gpp[j], (*data >> j) & 1);
+
+				break;
+
+			case GRIP_MODE_BD:
+
+				if (grip_xt_read_packet(grip->gameport, (i << 1) + 4, data)) {
+					grip->bads++;
+					break;
+				}
+
+				input_report_abs(dev, ABS_X,        (data[0] >> 2) & 0x3f);
+				input_report_abs(dev, ABS_Y,  63 - ((data[0] >> 8) & 0x3f));
+				input_report_abs(dev, ABS_THROTTLE, (data[2] >> 8) & 0x3f);
+
+				input_report_abs(dev, ABS_HAT0X, ((data[2] >> 1) & 1) - ( data[2]       & 1));
+				input_report_abs(dev, ABS_HAT0Y, ((data[2] >> 2) & 1) - ((data[2] >> 3) & 1));
+
+				for (j = 0; j < 5; j++)
+					input_report_key(dev, grip_btn_bd[j], (data[3] >> (j + 4)) & 1);
+
+				break;
+
+			case GRIP_MODE_XT:
+
+				if (grip_xt_read_packet(grip->gameport, (i << 1) + 4, data)) {
+					grip->bads++;
+					break;
+				}
+
+				input_report_abs(dev, ABS_X,        (data[0] >> 2) & 0x3f);
+				input_report_abs(dev, ABS_Y,  63 - ((data[0] >> 8) & 0x3f));
+				input_report_abs(dev, ABS_BRAKE,    (data[1] >> 2) & 0x3f);
+				input_report_abs(dev, ABS_GAS,	    (data[1] >> 8) & 0x3f);
+				input_report_abs(dev, ABS_THROTTLE, (data[2] >> 8) & 0x3f);
+
+				input_report_abs(dev, ABS_HAT0X, ((data[2] >> 1) & 1) - ( data[2]       & 1));
+				input_report_abs(dev, ABS_HAT0Y, ((data[2] >> 2) & 1) - ((data[2] >> 3) & 1));
+				input_report_abs(dev, ABS_HAT1X, ((data[2] >> 5) & 1) - ((data[2] >> 4) & 1));
+				input_report_abs(dev, ABS_HAT1Y, ((data[2] >> 6) & 1) - ((data[2] >> 7) & 1));
+
+				for (j = 0; j < 11; j++)
+					input_report_key(dev, grip_btn_xt[j], (data[3] >> (j + 3)) & 1);
+				break;
+
+			case GRIP_MODE_DC:
+
+				if (grip_xt_read_packet(grip->gameport, (i << 1) + 4, data)) {
+					grip->bads++;
+					break;
+				}
+
+				input_report_abs(dev, ABS_X,        (data[0] >> 2) & 0x3f);
+				input_report_abs(dev, ABS_Y,        (data[0] >> 8) & 0x3f);
+				input_report_abs(dev, ABS_RX,       (data[1] >> 2) & 0x3f);
+				input_report_abs(dev, ABS_RY,	    (data[1] >> 8) & 0x3f);
+				input_report_abs(dev, ABS_THROTTLE, (data[2] >> 8) & 0x3f);
+
+				input_report_abs(dev, ABS_HAT0X, ((data[2] >> 1) & 1) - ( data[2]       & 1));
+				input_report_abs(dev, ABS_HAT0Y, ((data[2] >> 2) & 1) - ((data[2] >> 3) & 1));
+
+				for (j = 0; j < 9; j++)
+					input_report_key(dev, grip_btn_dc[j], (data[3] >> (j + 3)) & 1);
+				break;
+
+
+		}
+
+		input_sync(dev);
+	}
+}
+
+static int grip_open(struct input_dev *dev)
+{
+	struct grip *grip = input_get_drvdata(dev);
+
+	gameport_start_polling(grip->gameport);
+	return 0;
+}
+
+static void grip_close(struct input_dev *dev)
+{
+	struct grip *grip = input_get_drvdata(dev);
+
+	gameport_stop_polling(grip->gameport);
+}
+
+static int grip_connect(struct gameport *gameport, struct gameport_driver *drv)
+{
+	struct grip *grip;
+	struct input_dev *input_dev;
+	unsigned int data[GRIP_LENGTH_XT];
+	int i, j, t;
+	int err;
+
+	grip = kzalloc_obj(*grip);
+	if (!grip)
+		return -ENOMEM;
+
+	grip->gameport = gameport;
+
+	gameport_set_drvdata(gameport, grip);
+
+	err = gameport_open(gameport, drv, GAMEPORT_MODE_RAW);
+	if (err)
+		goto fail1;
+
+	for (i = 0; i < 2; i++) {
+		if (!grip_gpp_read_packet(gameport, (i << 1) + 4, data)) {
+			grip->mode[i] = GRIP_MODE_GPP;
+			continue;
+		}
+		if (!grip_xt_read_packet(gameport, (i << 1) + 4, data)) {
+			if (!(data[3] & 7)) {
+				grip->mode[i] = GRIP_MODE_BD;
+				continue;
+			}
+			if (!(data[2] & 0xf0)) {
+				grip->mode[i] = GRIP_MODE_XT;
+				continue;
+			}
+			grip->mode[i] = GRIP_MODE_DC;
+			continue;
+		}
+	}
+
+	if (!grip->mode[0] && !grip->mode[1]) {
+		err = -ENODEV;
+		goto fail2;
+	}
+
+	gameport_set_poll_handler(gameport, grip_poll);
+	gameport_set_poll_interval(gameport, 20);
+
+	for (i = 0; i < 2; i++) {
+		if (!grip->mode[i])
+			continue;
+
+		grip->dev[i] = input_dev = input_allocate_device();
+		if (!input_dev) {
+			err = -ENOMEM;
+			goto fail3;
+		}
+
+		snprintf(grip->phys[i], sizeof(grip->phys[i]),
+			 "%s/input%d", gameport->phys, i);
+
+		input_dev->name = grip_name[grip->mode[i]];
+		input_dev->phys = grip->phys[i];
+		input_dev->id.bustype = BUS_GAMEPORT;
+		input_dev->id.vendor = GAMEPORT_ID_VENDOR_GRAVIS;
+		input_dev->id.product = grip->mode[i];
+		input_dev->id.version = 0x0100;
+		input_dev->dev.parent = &gameport->dev;
+
+		input_set_drvdata(input_dev, grip);
+
+		input_dev->open = grip_open;
+		input_dev->close = grip_close;
+
+		input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+
+		for (j = 0; (t = grip_abs[grip->mode[i]][j]) >= 0; j++) {
+
+			if (j < grip_cen[grip->mode[i]])
+				input_set_abs_params(input_dev, t, 14, 52, 1, 2);
+			else if (j < grip_anx[grip->mode[i]])
+				input_set_abs_params(input_dev, t, 3, 57, 1, 0);
+			else
+				input_set_abs_params(input_dev, t, -1, 1, 0, 0);
+		}
+
+		for (j = 0; (t = grip_btn[grip->mode[i]][j]) >= 0; j++)
+			if (t > 0)
+				set_bit(t, input_dev->keybit);
+
+		err = input_register_device(grip->dev[i]);
+		if (err)
+			goto fail4;
+	}
+
+	return 0;
+
+ fail4:	input_free_device(grip->dev[i]);
+ fail3:	while (--i >= 0)
+		if (grip->dev[i])
+			input_unregister_device(grip->dev[i]);
+ fail2:	gameport_close(gameport);
+ fail1:	gameport_set_drvdata(gameport, NULL);
+	kfree(grip);
+	return err;
+}
+
+static void grip_disconnect(struct gameport *gameport)
+{
+	struct grip *grip = gameport_get_drvdata(gameport);
+	int i;
+
+	for (i = 0; i < 2; i++)
+		if (grip->dev[i])
+			input_unregister_device(grip->dev[i]);
+	gameport_close(gameport);
+	gameport_set_drvdata(gameport, NULL);
+	kfree(grip);
+}
+
+static struct gameport_driver grip_drv = {
+	.driver		= {
+		.name	= "grip",
+		.owner	= THIS_MODULE,
+	},
+	.description	= DRIVER_DESC,
+	.connect	= grip_connect,
+	.disconnect	= grip_disconnect,
+};
+
+module_gameport_driver(grip_drv);