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, 358 insertions, 0 deletions

diff --git a/drivers/input/joystick/gf2k.c b/drivers/input/joystick/gf2k.c
new file mode 100644
index 000000000..1d843115d
--- /dev/null
+++ b/drivers/input/joystick/gf2k.c
@@ -0,0 +1,358 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (c) 1998-2001 Vojtech Pavlik
+ */
+
+/*
+ * Genius Flight 2000 joystick driver for Linux
+ */
+
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/input.h>
+#include <linux/gameport.h>
+#include <linux/jiffies.h>
+
+#define DRIVER_DESC	"Genius Flight 2000 joystick driver"
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+#define GF2K_START		400	/* The time we wait for the first bit [400 us] */
+#define GF2K_STROBE		40	/* The time we wait for the first bit [40 us] */
+#define GF2K_TIMEOUT		4	/* Wait for everything to settle [4 ms] */
+#define GF2K_LENGTH		80	/* Max number of triplets in a packet */
+
+/*
+ * Genius joystick ids ...
+ */
+
+#define GF2K_ID_G09		1
+#define GF2K_ID_F30D		2
+#define GF2K_ID_F30		3
+#define GF2K_ID_F31D		4
+#define GF2K_ID_F305		5
+#define GF2K_ID_F23P		6
+#define GF2K_ID_F31		7
+#define GF2K_ID_MAX		7
+
+static char gf2k_length[] = { 40, 40, 40, 40, 40, 40, 40, 40 };
+static char gf2k_hat_to_axis[][2] = {{ 0, 0}, { 0,-1}, { 1,-1}, { 1, 0}, { 1, 1}, { 0, 1}, {-1, 1}, {-1, 0}, {-1,-1}};
+
+static char *gf2k_names[] = {"", "Genius G-09D", "Genius F-30D", "Genius F-30", "Genius MaxFighter F-31D",
+				"Genius F-30-5", "Genius Flight2000 F-23", "Genius F-31"};
+static unsigned char gf2k_hats[] = { 0, 2, 0, 0, 2, 0, 2, 0 };
+static unsigned char gf2k_axes[] = { 0, 2, 0, 0, 4, 0, 4, 0 };
+static unsigned char gf2k_joys[] = { 0, 0, 0, 0,10, 0, 8, 0 };
+static unsigned char gf2k_pads[] = { 0, 6, 0, 0, 0, 0, 0, 0 };
+static unsigned char gf2k_lens[] = { 0,18, 0, 0,18, 0,18, 0 };
+
+static unsigned char gf2k_abs[] = { ABS_X, ABS_Y, ABS_THROTTLE, ABS_RUDDER, ABS_GAS, ABS_BRAKE };
+static short gf2k_btn_joy[] = { BTN_TRIGGER, BTN_THUMB, BTN_TOP, BTN_TOP2, BTN_BASE, BTN_BASE2, BTN_BASE3, BTN_BASE4 };
+static short gf2k_btn_pad[] = { BTN_A, BTN_B, BTN_C, BTN_X, BTN_Y, BTN_Z, BTN_TL, BTN_TR, BTN_TL2, BTN_TR2, BTN_START, BTN_SELECT };
+
+
+static short gf2k_seq_reset[] = { 240, 340, 0 };
+static short gf2k_seq_digital[] = { 590, 320, 860, 0 };
+
+struct gf2k {
+	struct gameport *gameport;
+	struct input_dev *dev;
+	int reads;
+	int bads;
+	unsigned char id;
+	unsigned char length;
+	char phys[32];
+};
+
+/*
+ * gf2k_read_packet() reads a Genius Flight2000 packet.
+ */
+
+static int gf2k_read_packet(struct gameport *gameport, int length, char *data)
+{
+	unsigned char u, v;
+	int i;
+	unsigned int t, p;
+	unsigned long flags;
+
+	t = gameport_time(gameport, GF2K_START);
+	p = gameport_time(gameport, GF2K_STROBE);
+
+	i = 0;
+
+	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 = p;
+		}
+	}
+
+	local_irq_restore(flags);
+
+	return i;
+}
+
+/*
+ * gf2k_trigger_seq() initializes a Genius Flight2000 joystick
+ * into digital mode.
+ */
+
+static void gf2k_trigger_seq(struct gameport *gameport, short *seq)
+{
+
+	unsigned long flags;
+	int i, t;
+
+        local_irq_save(flags);
+
+	i = 0;
+        do {
+		gameport_trigger(gameport);
+		t = gameport_time(gameport, GF2K_TIMEOUT * 1000);
+		while ((gameport_read(gameport) & 1) && t) t--;
+                udelay(seq[i]);
+        } while (seq[++i]);
+
+	gameport_trigger(gameport);
+
+	local_irq_restore(flags);
+}
+
+/*
+ * js_sw_get_bits() composes bits from the triplet buffer into a __u64.
+ * Parameter 'pos' is bit number inside packet where to start at, 'num' is number
+ * of bits to be read, 'shift' is offset in the resulting __u64 to start at, bits
+ * is number of bits per triplet.
+ */
+
+#define GB(p,n,s)	gf2k_get_bits(data, p, n, s)
+
+static int gf2k_get_bits(unsigned char *buf, int pos, int num, int shift)
+{
+	__u64 data = 0;
+	int i;
+
+	for (i = 0; i < num / 3 + 2; i++)
+		data |= buf[pos / 3 + i] << (i * 3);
+	data >>= pos % 3;
+	data &= (1 << num) - 1;
+	data <<= shift;
+
+	return data;
+}
+
+static void gf2k_read(struct gf2k *gf2k, unsigned char *data)
+{
+	struct input_dev *dev = gf2k->dev;
+	int i, t;
+
+	for (i = 0; i < 4 && i < gf2k_axes[gf2k->id]; i++)
+		input_report_abs(dev, gf2k_abs[i], GB(i<<3,8,0) | GB(i+46,1,8) | GB(i+50,1,9));
+
+	for (i = 0; i < 2 && i < gf2k_axes[gf2k->id] - 4; i++)
+		input_report_abs(dev, gf2k_abs[i], GB(i*9+60,8,0) | GB(i+54,1,9));
+
+	t = GB(40,4,0);
+
+	if (t < ARRAY_SIZE(gf2k_hat_to_axis))
+		for (i = 0; i < gf2k_hats[gf2k->id]; i++)
+			input_report_abs(dev, ABS_HAT0X + i,
+					 gf2k_hat_to_axis[t][i]);
+
+	t = GB(44,2,0) | GB(32,8,2) | GB(78,2,10);
+
+	for (i = 0; i < gf2k_joys[gf2k->id]; i++)
+		input_report_key(dev, gf2k_btn_joy[i], (t >> i) & 1);
+
+	for (i = 0; i < gf2k_pads[gf2k->id]; i++)
+		input_report_key(dev, gf2k_btn_pad[i], (t >> i) & 1);
+
+	input_sync(dev);
+}
+
+/*
+ * gf2k_poll() reads and analyzes Genius joystick data.
+ */
+
+static void gf2k_poll(struct gameport *gameport)
+{
+	struct gf2k *gf2k = gameport_get_drvdata(gameport);
+	unsigned char data[GF2K_LENGTH];
+
+	gf2k->reads++;
+
+	if (gf2k_read_packet(gf2k->gameport, gf2k_length[gf2k->id], data) < gf2k_length[gf2k->id])
+		gf2k->bads++;
+	else
+		gf2k_read(gf2k, data);
+}
+
+static int gf2k_open(struct input_dev *dev)
+{
+	struct gf2k *gf2k = input_get_drvdata(dev);
+
+	gameport_start_polling(gf2k->gameport);
+	return 0;
+}
+
+static void gf2k_close(struct input_dev *dev)
+{
+	struct gf2k *gf2k = input_get_drvdata(dev);
+
+	gameport_stop_polling(gf2k->gameport);
+}
+
+/*
+ * gf2k_connect() probes for Genius id joysticks.
+ */
+
+static int gf2k_connect(struct gameport *gameport, struct gameport_driver *drv)
+{
+	struct gf2k *gf2k;
+	struct input_dev *input_dev;
+	unsigned char data[GF2K_LENGTH];
+	int i, err;
+
+	gf2k = kzalloc_obj(*gf2k);
+	input_dev = input_allocate_device();
+	if (!gf2k || !input_dev) {
+		err = -ENOMEM;
+		goto fail1;
+	}
+
+	gf2k->gameport = gameport;
+	gf2k->dev = input_dev;
+
+	gameport_set_drvdata(gameport, gf2k);
+
+	err = gameport_open(gameport, drv, GAMEPORT_MODE_RAW);
+	if (err)
+		goto fail1;
+
+	gf2k_trigger_seq(gameport, gf2k_seq_reset);
+
+	msleep(GF2K_TIMEOUT);
+
+	gf2k_trigger_seq(gameport, gf2k_seq_digital);
+
+	msleep(GF2K_TIMEOUT);
+
+	if (gf2k_read_packet(gameport, GF2K_LENGTH, data) < 12) {
+		err = -ENODEV;
+		goto fail2;
+	}
+
+	if (!(gf2k->id = GB(7,2,0) | GB(3,3,2) | GB(0,3,5))) {
+		err = -ENODEV;
+		goto fail2;
+	}
+
+#ifdef RESET_WORKS
+	if ((gf2k->id != (GB(19,2,0) | GB(15,3,2) | GB(12,3,5))) &&
+	    (gf2k->id != (GB(31,2,0) | GB(27,3,2) | GB(24,3,5)))) {
+		err = -ENODEV;
+		goto fail2;
+	}
+#else
+	gf2k->id = 6;
+#endif
+
+	if (gf2k->id > GF2K_ID_MAX || !gf2k_axes[gf2k->id]) {
+		printk(KERN_WARNING "gf2k.c: Not yet supported joystick on %s. [id: %d type:%s]\n",
+			gameport->phys, gf2k->id, gf2k->id > GF2K_ID_MAX ? "Unknown" : gf2k_names[gf2k->id]);
+		err = -ENODEV;
+		goto fail2;
+	}
+
+	gameport_set_poll_handler(gameport, gf2k_poll);
+	gameport_set_poll_interval(gameport, 20);
+
+	snprintf(gf2k->phys, sizeof(gf2k->phys), "%s/input0", gameport->phys);
+
+	gf2k->length = gf2k_lens[gf2k->id];
+
+	input_dev->name = gf2k_names[gf2k->id];
+	input_dev->phys = gf2k->phys;
+	input_dev->id.bustype = BUS_GAMEPORT;
+	input_dev->id.vendor = GAMEPORT_ID_VENDOR_GENIUS;
+	input_dev->id.product = gf2k->id;
+	input_dev->id.version = 0x0100;
+	input_dev->dev.parent = &gameport->dev;
+
+	input_set_drvdata(input_dev, gf2k);
+
+	input_dev->open = gf2k_open;
+	input_dev->close = gf2k_close;
+
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+
+	for (i = 0; i < gf2k_axes[gf2k->id]; i++)
+		set_bit(gf2k_abs[i], input_dev->absbit);
+
+	for (i = 0; i < gf2k_hats[gf2k->id]; i++)
+		input_set_abs_params(input_dev, ABS_HAT0X + i, -1, 1, 0, 0);
+
+	for (i = 0; i < gf2k_joys[gf2k->id]; i++)
+		set_bit(gf2k_btn_joy[i], input_dev->keybit);
+
+	for (i = 0; i < gf2k_pads[gf2k->id]; i++)
+		set_bit(gf2k_btn_pad[i], input_dev->keybit);
+
+	gf2k_read_packet(gameport, gf2k->length, data);
+	gf2k_read(gf2k, data);
+
+	for (i = 0; i < gf2k_axes[gf2k->id]; i++) {
+		int max = i < 2 ?
+			input_abs_get_val(input_dev, gf2k_abs[i]) * 2 :
+			input_abs_get_val(input_dev, gf2k_abs[0]) +
+				input_abs_get_val(input_dev, gf2k_abs[1]);
+		int flat = i < 2 ? 24 : 0;
+
+		input_set_abs_params(input_dev, gf2k_abs[i],
+				     32, max - 32, 8, flat);
+	}
+
+	err = input_register_device(gf2k->dev);
+	if (err)
+		goto fail2;
+
+	return 0;
+
+ fail2:	gameport_close(gameport);
+ fail1:	gameport_set_drvdata(gameport, NULL);
+	input_free_device(input_dev);
+	kfree(gf2k);
+	return err;
+}
+
+static void gf2k_disconnect(struct gameport *gameport)
+{
+	struct gf2k *gf2k = gameport_get_drvdata(gameport);
+
+	input_unregister_device(gf2k->dev);
+	gameport_close(gameport);
+	gameport_set_drvdata(gameport, NULL);
+	kfree(gf2k);
+}
+
+static struct gameport_driver gf2k_drv = {
+	.driver		= {
+		.name	= "gf2k",
+	},
+	.description	= DRIVER_DESC,
+	.connect	= gf2k_connect,
+	.disconnect	= gf2k_disconnect,
+};
+
+module_gameport_driver(gf2k_drv);