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, 396 insertions, 0 deletions

diff --git a/drivers/input/joystick/a3d.c b/drivers/input/joystick/a3d.c
new file mode 100644
index 000000000..48a145796
--- /dev/null
+++ b/drivers/input/joystick/a3d.c
@@ -0,0 +1,396 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (c) 1998-2001 Vojtech Pavlik
+ */
+
+/*
+ * FP-Gaming Assassin 3D joystick 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	"FP-Gaming Assassin 3D joystick driver"
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+#define A3D_MAX_START		600	/* 600 us */
+#define A3D_MAX_STROBE		80	/* 80 us */
+#define A3D_MAX_LENGTH		40	/* 40*3 bits */
+
+#define A3D_MODE_A3D		1	/* Assassin 3D */
+#define A3D_MODE_PAN		2	/* Panther */
+#define A3D_MODE_OEM		3	/* Panther OEM version */
+#define A3D_MODE_PXL		4	/* Panther XL */
+
+static char *a3d_names[] = { NULL, "FP-Gaming Assassin 3D", "MadCatz Panther", "OEM Panther",
+			"MadCatz Panther XL", "MadCatz Panther XL w/ rudder" };
+
+struct a3d {
+	struct gameport *gameport;
+	struct gameport *adc;
+	struct input_dev *dev;
+	int axes[4];
+	int buttons;
+	int mode;
+	int length;
+	int reads;
+	int bads;
+	char phys[32];
+};
+
+/*
+ * a3d_read_packet() reads an Assassin 3D packet.
+ */
+
+static int a3d_read_packet(struct gameport *gameport, int length, char *data)
+{
+	unsigned long flags;
+	unsigned char u, v;
+	unsigned int t, s;
+	int i;
+
+	i = 0;
+	t = gameport_time(gameport, A3D_MAX_START);
+	s = gameport_time(gameport, A3D_MAX_STROBE);
+
+	local_irq_save(flags);
+	gameport_trigger(gameport);
+	v = gameport_read(gameport);
+
+	while (t > 0 && i < length) {
+		t--;
+		u = v; v = gameport_read(gameport);
+		if (~v & u & 0x10) {
+			data[i++] = v >> 5;
+			t = s;
+		}
+	}
+
+	local_irq_restore(flags);
+
+	return i;
+}
+
+/*
+ * a3d_csum() computes checksum of triplet packet
+ */
+
+static int a3d_csum(char *data, int count)
+{
+	int i, csum = 0;
+
+	for (i = 0; i < count - 2; i++)
+		csum += data[i];
+	return (csum & 0x3f) != ((data[count - 2] << 3) | data[count - 1]);
+}
+
+static void a3d_read(struct a3d *a3d, unsigned char *data)
+{
+	struct input_dev *dev = a3d->dev;
+
+	switch (a3d->mode) {
+
+		case A3D_MODE_A3D:
+		case A3D_MODE_OEM:
+		case A3D_MODE_PAN:
+
+			input_report_rel(dev, REL_X, ((data[5] << 6) | (data[6] << 3) | data[ 7]) - ((data[5] & 4) << 7));
+			input_report_rel(dev, REL_Y, ((data[8] << 6) | (data[9] << 3) | data[10]) - ((data[8] & 4) << 7));
+
+			input_report_key(dev, BTN_RIGHT,  data[2] & 1);
+			input_report_key(dev, BTN_LEFT,   data[3] & 2);
+			input_report_key(dev, BTN_MIDDLE, data[3] & 4);
+
+			input_sync(dev);
+
+			a3d->axes[0] = ((signed char)((data[11] << 6) | (data[12] << 3) | (data[13]))) + 128;
+			a3d->axes[1] = ((signed char)((data[14] << 6) | (data[15] << 3) | (data[16]))) + 128;
+			a3d->axes[2] = ((signed char)((data[17] << 6) | (data[18] << 3) | (data[19]))) + 128;
+			a3d->axes[3] = ((signed char)((data[20] << 6) | (data[21] << 3) | (data[22]))) + 128;
+
+			a3d->buttons = ((data[3] << 3) | data[4]) & 0xf;
+
+			break;
+
+		case A3D_MODE_PXL:
+
+			input_report_rel(dev, REL_X, ((data[ 9] << 6) | (data[10] << 3) | data[11]) - ((data[ 9] & 4) << 7));
+			input_report_rel(dev, REL_Y, ((data[12] << 6) | (data[13] << 3) | data[14]) - ((data[12] & 4) << 7));
+
+			input_report_key(dev, BTN_RIGHT,  data[2] & 1);
+			input_report_key(dev, BTN_LEFT,   data[3] & 2);
+			input_report_key(dev, BTN_MIDDLE, data[3] & 4);
+			input_report_key(dev, BTN_SIDE,   data[7] & 2);
+			input_report_key(dev, BTN_EXTRA,  data[7] & 4);
+
+			input_report_abs(dev, ABS_X,        ((signed char)((data[15] << 6) | (data[16] << 3) | (data[17]))) + 128);
+			input_report_abs(dev, ABS_Y,        ((signed char)((data[18] << 6) | (data[19] << 3) | (data[20]))) + 128);
+			input_report_abs(dev, ABS_RUDDER,   ((signed char)((data[21] << 6) | (data[22] << 3) | (data[23]))) + 128);
+			input_report_abs(dev, ABS_THROTTLE, ((signed char)((data[24] << 6) | (data[25] << 3) | (data[26]))) + 128);
+
+			input_report_abs(dev, ABS_HAT0X, ( data[5]       & 1) - ((data[5] >> 2) & 1));
+			input_report_abs(dev, ABS_HAT0Y, ((data[5] >> 1) & 1) - ((data[6] >> 2) & 1));
+			input_report_abs(dev, ABS_HAT1X, ((data[4] >> 1) & 1) - ( data[3]       & 1));
+			input_report_abs(dev, ABS_HAT1Y, ((data[4] >> 2) & 1) - ( data[4]       & 1));
+
+			input_report_key(dev, BTN_TRIGGER, data[8] & 1);
+			input_report_key(dev, BTN_THUMB,   data[8] & 2);
+			input_report_key(dev, BTN_TOP,     data[8] & 4);
+			input_report_key(dev, BTN_PINKIE,  data[7] & 1);
+
+			input_sync(dev);
+
+			break;
+	}
+}
+
+
+/*
+ * a3d_poll() reads and analyzes A3D joystick data.
+ */
+
+static void a3d_poll(struct gameport *gameport)
+{
+	struct a3d *a3d = gameport_get_drvdata(gameport);
+	unsigned char data[A3D_MAX_LENGTH];
+
+	a3d->reads++;
+	if (a3d_read_packet(a3d->gameport, a3d->length, data) != a3d->length ||
+	    data[0] != a3d->mode || a3d_csum(data, a3d->length))
+		a3d->bads++;
+	else
+		a3d_read(a3d, data);
+}
+
+/*
+ * a3d_adc_cooked_read() copies the acis and button data to the
+ * callers arrays. It could do the read itself, but the caller could
+ * call this more than 50 times a second, which would use too much CPU.
+ */
+
+static int a3d_adc_cooked_read(struct gameport *gameport, int *axes, int *buttons)
+{
+	struct a3d *a3d = gameport->port_data;
+	int i;
+
+	for (i = 0; i < 4; i++)
+		axes[i] = (a3d->axes[i] < 254) ? a3d->axes[i] : -1;
+	*buttons = a3d->buttons;
+	return 0;
+}
+
+/*
+ * a3d_adc_open() is the gameport open routine. It refuses to serve
+ * any but cooked data.
+ */
+
+static int a3d_adc_open(struct gameport *gameport, int mode)
+{
+	struct a3d *a3d = gameport->port_data;
+
+	if (mode != GAMEPORT_MODE_COOKED)
+		return -1;
+
+	gameport_start_polling(a3d->gameport);
+	return 0;
+}
+
+/*
+ * a3d_adc_close() is a callback from the input close routine.
+ */
+
+static void a3d_adc_close(struct gameport *gameport)
+{
+	struct a3d *a3d = gameport->port_data;
+
+	gameport_stop_polling(a3d->gameport);
+}
+
+/*
+ * a3d_open() is a callback from the input open routine.
+ */
+
+static int a3d_open(struct input_dev *dev)
+{
+	struct a3d *a3d = input_get_drvdata(dev);
+
+	gameport_start_polling(a3d->gameport);
+	return 0;
+}
+
+/*
+ * a3d_close() is a callback from the input close routine.
+ */
+
+static void a3d_close(struct input_dev *dev)
+{
+	struct a3d *a3d = input_get_drvdata(dev);
+
+	gameport_stop_polling(a3d->gameport);
+}
+
+/*
+ * a3d_connect() probes for A3D joysticks.
+ */
+
+static int a3d_connect(struct gameport *gameport, struct gameport_driver *drv)
+{
+	struct a3d *a3d;
+	struct input_dev *input_dev;
+	struct gameport *adc;
+	unsigned char data[A3D_MAX_LENGTH];
+	int i;
+	int err;
+
+	a3d = kzalloc_obj(*a3d);
+	input_dev = input_allocate_device();
+	if (!a3d || !input_dev) {
+		err = -ENOMEM;
+		goto fail1;
+	}
+
+	a3d->dev = input_dev;
+	a3d->gameport = gameport;
+
+	gameport_set_drvdata(gameport, a3d);
+
+	err = gameport_open(gameport, drv, GAMEPORT_MODE_RAW);
+	if (err)
+		goto fail1;
+
+	i = a3d_read_packet(gameport, A3D_MAX_LENGTH, data);
+
+	if (!i || a3d_csum(data, i)) {
+		err = -ENODEV;
+		goto fail2;
+	}
+
+	a3d->mode = data[0];
+
+	if (!a3d->mode || a3d->mode > 5) {
+		printk(KERN_WARNING "a3d.c: Unknown A3D device detected "
+			"(%s, id=%d), contact <vojtech@ucw.cz>\n", gameport->phys, a3d->mode);
+		err = -ENODEV;
+		goto fail2;
+	}
+
+	gameport_set_poll_handler(gameport, a3d_poll);
+	gameport_set_poll_interval(gameport, 20);
+
+	snprintf(a3d->phys, sizeof(a3d->phys), "%s/input0", gameport->phys);
+
+	input_dev->name = a3d_names[a3d->mode];
+	input_dev->phys = a3d->phys;
+	input_dev->id.bustype = BUS_GAMEPORT;
+	input_dev->id.vendor = GAMEPORT_ID_VENDOR_MADCATZ;
+	input_dev->id.product = a3d->mode;
+	input_dev->id.version = 0x0100;
+	input_dev->dev.parent = &gameport->dev;
+	input_dev->open = a3d_open;
+	input_dev->close = a3d_close;
+
+	input_set_drvdata(input_dev, a3d);
+
+	if (a3d->mode == A3D_MODE_PXL) {
+
+		int axes[] = { ABS_X, ABS_Y, ABS_THROTTLE, ABS_RUDDER };
+
+		a3d->length = 33;
+
+		input_dev->evbit[0] |= BIT_MASK(EV_ABS) | BIT_MASK(EV_KEY) |
+			BIT_MASK(EV_REL);
+		input_dev->relbit[0] |= BIT_MASK(REL_X) | BIT_MASK(REL_Y);
+		input_dev->absbit[0] |= BIT_MASK(ABS_X) | BIT_MASK(ABS_Y) |
+			BIT_MASK(ABS_THROTTLE) | BIT_MASK(ABS_RUDDER) |
+			BIT_MASK(ABS_HAT0X) | BIT_MASK(ABS_HAT0Y) |
+			BIT_MASK(ABS_HAT1X) | BIT_MASK(ABS_HAT1Y);
+		input_dev->keybit[BIT_WORD(BTN_MOUSE)] |= BIT_MASK(BTN_RIGHT) |
+			BIT_MASK(BTN_LEFT) | BIT_MASK(BTN_MIDDLE) |
+			BIT_MASK(BTN_SIDE) | BIT_MASK(BTN_EXTRA);
+		input_dev->keybit[BIT_WORD(BTN_JOYSTICK)] |=
+			BIT_MASK(BTN_TRIGGER) | BIT_MASK(BTN_THUMB) |
+			BIT_MASK(BTN_TOP) | BIT_MASK(BTN_PINKIE);
+
+		a3d_read(a3d, data);
+
+		for (i = 0; i < 4; i++) {
+			if (i < 2)
+				input_set_abs_params(input_dev, axes[i],
+					48, input_abs_get_val(input_dev, axes[i]) * 2 - 48, 0, 8);
+			else
+				input_set_abs_params(input_dev, axes[i], 2, 253, 0, 0);
+			input_set_abs_params(input_dev, ABS_HAT0X + i, -1, 1, 0, 0);
+		}
+
+	} else {
+		a3d->length = 29;
+
+		input_dev->evbit[0] |= BIT_MASK(EV_KEY) | BIT_MASK(EV_REL);
+		input_dev->relbit[0] |= BIT_MASK(REL_X) | BIT_MASK(REL_Y);
+		input_dev->keybit[BIT_WORD(BTN_MOUSE)] |= BIT_MASK(BTN_RIGHT) |
+			BIT_MASK(BTN_LEFT) | BIT_MASK(BTN_MIDDLE);
+
+		a3d_read(a3d, data);
+
+		if (!(a3d->adc = adc = gameport_allocate_port()))
+			printk(KERN_ERR "a3d: Not enough memory for ADC port\n");
+		else {
+			adc->port_data = a3d;
+			adc->open = a3d_adc_open;
+			adc->close = a3d_adc_close;
+			adc->cooked_read = a3d_adc_cooked_read;
+			adc->fuzz = 1;
+
+			gameport_set_name(adc, a3d_names[a3d->mode]);
+			gameport_set_phys(adc, "%s/gameport0", gameport->phys);
+			adc->dev.parent = &gameport->dev;
+
+			gameport_register_port(adc);
+		}
+	}
+
+	err = input_register_device(a3d->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3:	if (a3d->adc)
+		gameport_unregister_port(a3d->adc);
+ fail2:	gameport_close(gameport);
+ fail1:	gameport_set_drvdata(gameport, NULL);
+	input_free_device(input_dev);
+	kfree(a3d);
+	return err;
+}
+
+static void a3d_disconnect(struct gameport *gameport)
+{
+	struct a3d *a3d = gameport_get_drvdata(gameport);
+
+	input_unregister_device(a3d->dev);
+	if (a3d->adc)
+		gameport_unregister_port(a3d->adc);
+	gameport_close(gameport);
+	gameport_set_drvdata(gameport, NULL);
+	kfree(a3d);
+}
+
+static struct gameport_driver a3d_drv = {
+	.driver		= {
+		.name	= "adc",
+		.owner	= THIS_MODULE,
+	},
+	.description	= DRIVER_DESC,
+	.connect	= a3d_connect,
+	.disconnect	= a3d_disconnect,
+};
+
+module_gameport_driver(a3d_drv);