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, 376 insertions, 0 deletions

diff --git a/drivers/input/keyboard/sunkbd.c b/drivers/input/keyboard/sunkbd.c
new file mode 100644
index 000000000..5a0020827
--- /dev/null
+++ b/drivers/input/keyboard/sunkbd.c
@@ -0,0 +1,376 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (c) 1999-2001 Vojtech Pavlik
+ */
+
+/*
+ * Sun keyboard driver for Linux
+ */
+
+#include <linux/delay.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+#include <linux/workqueue.h>
+
+#define DRIVER_DESC	"Sun keyboard driver"
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+static unsigned char sunkbd_keycode[128] = {
+	  0,128,114,129,115, 59, 60, 68, 61, 87, 62, 88, 63,100, 64,112,
+	 65, 66, 67, 56,103,119, 99, 70,105,130,131,108,106,  1,  2,  3,
+	  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 41, 14,110,113, 98, 55,
+	116,132, 83,133,102, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
+	 26, 27,111,127, 71, 72, 73, 74,134,135,107,  0, 29, 30, 31, 32,
+	 33, 34, 35, 36, 37, 38, 39, 40, 43, 28, 96, 75, 76, 77, 82,136,
+	104,137, 69, 42, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54,101,
+	 79, 80, 81,  0,  0,  0,138, 58,125, 57,126,109, 86, 78
+};
+
+#define SUNKBD_CMD_RESET	0x1
+#define SUNKBD_CMD_BELLON	0x2
+#define SUNKBD_CMD_BELLOFF	0x3
+#define SUNKBD_CMD_CLICK	0xa
+#define SUNKBD_CMD_NOCLICK	0xb
+#define SUNKBD_CMD_SETLED	0xe
+#define SUNKBD_CMD_LAYOUT	0xf
+
+#define SUNKBD_RET_RESET	0xff
+#define SUNKBD_RET_ALLUP	0x7f
+#define SUNKBD_RET_LAYOUT	0xfe
+
+#define SUNKBD_LAYOUT_5_MASK	0x20
+#define SUNKBD_RELEASE		0x80
+#define SUNKBD_KEY		0x7f
+
+/*
+ * Per-keyboard data.
+ */
+
+struct sunkbd {
+	unsigned char keycode[ARRAY_SIZE(sunkbd_keycode)];
+	struct input_dev *dev;
+	struct serio *serio;
+	struct work_struct tq;
+	wait_queue_head_t wait;
+	char name[64];
+	char phys[32];
+	char type;
+	bool enabled;
+	volatile s8 reset;
+	volatile s8 layout;
+};
+
+/*
+ * sunkbd_interrupt() is called by the low level driver when a character
+ * is received.
+ */
+
+static irqreturn_t sunkbd_interrupt(struct serio *serio,
+		unsigned char data, unsigned int flags)
+{
+	struct sunkbd *sunkbd = serio_get_drvdata(serio);
+
+	if (sunkbd->reset <= -1) {
+		/*
+		 * If cp[i] is 0xff, sunkbd->reset will stay -1.
+		 * The keyboard sends 0xff 0xff 0xID on powerup.
+		 */
+		sunkbd->reset = data;
+		wake_up_interruptible(&sunkbd->wait);
+		goto out;
+	}
+
+	if (sunkbd->layout == -1) {
+		sunkbd->layout = data;
+		wake_up_interruptible(&sunkbd->wait);
+		goto out;
+	}
+
+	switch (data) {
+
+	case SUNKBD_RET_RESET:
+		if (sunkbd->enabled)
+			schedule_work(&sunkbd->tq);
+		sunkbd->reset = -1;
+		break;
+
+	case SUNKBD_RET_LAYOUT:
+		sunkbd->layout = -1;
+		break;
+
+	case SUNKBD_RET_ALLUP: /* All keys released */
+		break;
+
+	default:
+		if (!sunkbd->enabled)
+			break;
+
+		if (sunkbd->keycode[data & SUNKBD_KEY]) {
+			input_report_key(sunkbd->dev,
+					 sunkbd->keycode[data & SUNKBD_KEY],
+					 !(data & SUNKBD_RELEASE));
+			input_sync(sunkbd->dev);
+		} else {
+			printk(KERN_WARNING
+				"sunkbd.c: Unknown key (scancode %#x) %s.\n",
+				data & SUNKBD_KEY,
+				data & SUNKBD_RELEASE ? "released" : "pressed");
+		}
+	}
+out:
+	return IRQ_HANDLED;
+}
+
+/*
+ * sunkbd_event() handles events from the input module.
+ */
+
+static int sunkbd_event(struct input_dev *dev,
+			unsigned int type, unsigned int code, int value)
+{
+	struct sunkbd *sunkbd = input_get_drvdata(dev);
+
+	switch (type) {
+
+	case EV_LED:
+
+		serio_write(sunkbd->serio, SUNKBD_CMD_SETLED);
+		serio_write(sunkbd->serio,
+			(!!test_bit(LED_CAPSL,   dev->led) << 3) |
+			(!!test_bit(LED_SCROLLL, dev->led) << 2) |
+			(!!test_bit(LED_COMPOSE, dev->led) << 1) |
+			 !!test_bit(LED_NUML,    dev->led));
+		return 0;
+
+	case EV_SND:
+
+		switch (code) {
+
+		case SND_CLICK:
+			serio_write(sunkbd->serio, SUNKBD_CMD_NOCLICK - value);
+			return 0;
+
+		case SND_BELL:
+			serio_write(sunkbd->serio, SUNKBD_CMD_BELLOFF - value);
+			return 0;
+		}
+
+		break;
+	}
+
+	return -1;
+}
+
+/*
+ * sunkbd_initialize() checks for a Sun keyboard attached, and determines
+ * its type.
+ */
+
+static int sunkbd_initialize(struct sunkbd *sunkbd)
+{
+	sunkbd->reset = -2;
+	serio_write(sunkbd->serio, SUNKBD_CMD_RESET);
+	wait_event_interruptible_timeout(sunkbd->wait, sunkbd->reset >= 0, HZ);
+	if (sunkbd->reset < 0)
+		return -1;
+
+	sunkbd->type = sunkbd->reset;
+
+	if (sunkbd->type == 4) {	/* Type 4 keyboard */
+		sunkbd->layout = -2;
+		serio_write(sunkbd->serio, SUNKBD_CMD_LAYOUT);
+		wait_event_interruptible_timeout(sunkbd->wait,
+						 sunkbd->layout >= 0, HZ / 4);
+		if (sunkbd->layout < 0)
+			return -1;
+		if (sunkbd->layout & SUNKBD_LAYOUT_5_MASK)
+			sunkbd->type = 5;
+	}
+
+	return 0;
+}
+
+/*
+ * sunkbd_set_leds_beeps() sets leds and beeps to a state the computer remembers
+ * they were in.
+ */
+
+static void sunkbd_set_leds_beeps(struct sunkbd *sunkbd)
+{
+	serio_write(sunkbd->serio, SUNKBD_CMD_SETLED);
+	serio_write(sunkbd->serio,
+		(!!test_bit(LED_CAPSL,   sunkbd->dev->led) << 3) |
+		(!!test_bit(LED_SCROLLL, sunkbd->dev->led) << 2) |
+		(!!test_bit(LED_COMPOSE, sunkbd->dev->led) << 1) |
+		 !!test_bit(LED_NUML,    sunkbd->dev->led));
+	serio_write(sunkbd->serio,
+		SUNKBD_CMD_NOCLICK - !!test_bit(SND_CLICK, sunkbd->dev->snd));
+	serio_write(sunkbd->serio,
+		SUNKBD_CMD_BELLOFF - !!test_bit(SND_BELL, sunkbd->dev->snd));
+}
+
+
+/*
+ * sunkbd_reinit() wait for the keyboard reset to complete and restores state
+ * of leds and beeps.
+ */
+
+static void sunkbd_reinit(struct work_struct *work)
+{
+	struct sunkbd *sunkbd = container_of(work, struct sunkbd, tq);
+
+	/*
+	 * It is OK that we check sunkbd->enabled without pausing serio,
+	 * as we only want to catch true->false transition that will
+	 * happen once and we will be woken up for it.
+	 */
+	wait_event_interruptible_timeout(sunkbd->wait,
+					 sunkbd->reset >= 0 || !sunkbd->enabled,
+					 HZ);
+
+	if (sunkbd->reset >= 0 && sunkbd->enabled)
+		sunkbd_set_leds_beeps(sunkbd);
+}
+
+static void sunkbd_enable(struct sunkbd *sunkbd, bool enable)
+{
+	scoped_guard(serio_pause_rx, sunkbd->serio)
+		sunkbd->enabled = enable;
+
+	if (!enable) {
+		wake_up_interruptible(&sunkbd->wait);
+		cancel_work_sync(&sunkbd->tq);
+	}
+}
+
+/*
+ * sunkbd_connect() probes for a Sun keyboard and fills the necessary
+ * structures.
+ */
+
+static int sunkbd_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct sunkbd *sunkbd;
+	struct input_dev *input_dev;
+	int err = -ENOMEM;
+	int i;
+
+	sunkbd = kzalloc_obj(*sunkbd);
+	input_dev = input_allocate_device();
+	if (!sunkbd || !input_dev)
+		goto fail1;
+
+	sunkbd->serio = serio;
+	sunkbd->dev = input_dev;
+	init_waitqueue_head(&sunkbd->wait);
+	INIT_WORK(&sunkbd->tq, sunkbd_reinit);
+	snprintf(sunkbd->phys, sizeof(sunkbd->phys), "%s/input0", serio->phys);
+
+	serio_set_drvdata(serio, sunkbd);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	if (sunkbd_initialize(sunkbd) < 0) {
+		err = -ENODEV;
+		goto fail3;
+	}
+
+	snprintf(sunkbd->name, sizeof(sunkbd->name),
+		 "Sun Type %d keyboard", sunkbd->type);
+	memcpy(sunkbd->keycode, sunkbd_keycode, sizeof(sunkbd->keycode));
+
+	input_dev->name = sunkbd->name;
+	input_dev->phys = sunkbd->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor  = SERIO_SUNKBD;
+	input_dev->id.product = sunkbd->type;
+	input_dev->id.version = 0x0100;
+	input_dev->dev.parent = &serio->dev;
+
+	input_set_drvdata(input_dev, sunkbd);
+
+	input_dev->event = sunkbd_event;
+
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_LED) |
+		BIT_MASK(EV_SND) | BIT_MASK(EV_REP);
+	input_dev->ledbit[0] = BIT_MASK(LED_CAPSL) | BIT_MASK(LED_COMPOSE) |
+		BIT_MASK(LED_SCROLLL) | BIT_MASK(LED_NUML);
+	input_dev->sndbit[0] = BIT_MASK(SND_CLICK) | BIT_MASK(SND_BELL);
+
+	input_dev->keycode = sunkbd->keycode;
+	input_dev->keycodesize = sizeof(unsigned char);
+	input_dev->keycodemax = ARRAY_SIZE(sunkbd_keycode);
+	for (i = 0; i < ARRAY_SIZE(sunkbd_keycode); i++)
+		__set_bit(sunkbd->keycode[i], input_dev->keybit);
+	__clear_bit(KEY_RESERVED, input_dev->keybit);
+
+	sunkbd_enable(sunkbd, true);
+
+	err = input_register_device(sunkbd->dev);
+	if (err)
+		goto fail4;
+
+	return 0;
+
+ fail4:	sunkbd_enable(sunkbd, false);
+ fail3:	serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(sunkbd);
+	return err;
+}
+
+/*
+ * sunkbd_disconnect() unregisters and closes behind us.
+ */
+
+static void sunkbd_disconnect(struct serio *serio)
+{
+	struct sunkbd *sunkbd = serio_get_drvdata(serio);
+
+	sunkbd_enable(sunkbd, false);
+	input_unregister_device(sunkbd->dev);
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	kfree(sunkbd);
+}
+
+static const struct serio_device_id sunkbd_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_SUNKBD,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_UNKNOWN, /* sunkbd does probe */
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, sunkbd_serio_ids);
+
+static struct serio_driver sunkbd_drv = {
+	.driver		= {
+		.name	= "sunkbd",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= sunkbd_serio_ids,
+	.interrupt	= sunkbd_interrupt,
+	.connect	= sunkbd_connect,
+	.disconnect	= sunkbd_disconnect,
+};
+
+module_serio_driver(sunkbd_drv);