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, 449 insertions, 0 deletions

diff --git a/drivers/input/keyboard/pinephone-keyboard.c b/drivers/input/keyboard/pinephone-keyboard.c
new file mode 100644
index 000000000..86f21045c
--- /dev/null
+++ b/drivers/input/keyboard/pinephone-keyboard.c
@@ -0,0 +1,449 @@
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// Copyright (C) 2021-2022 Samuel Holland <samuel@sholland.org>
+
+#include <linux/crc8.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/input/matrix_keypad.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regulator/consumer.h>
+#include <linux/types.h>
+
+#define DRV_NAME			"pinephone-keyboard"
+
+#define PPKB_CRC8_POLYNOMIAL		0x07
+
+#define PPKB_DEVICE_ID_HI		0x00
+#define PPKB_DEVICE_ID_HI_VALUE			'K'
+#define PPKB_DEVICE_ID_LO		0x01
+#define PPKB_DEVICE_ID_LO_VALUE			'B'
+#define PPKB_FW_REVISION		0x02
+#define PPKB_FW_FEATURES		0x03
+#define PPKB_MATRIX_SIZE		0x06
+#define PPKB_SCAN_CRC			0x07
+#define PPKB_SCAN_DATA			0x08
+#define PPKB_SYS_CONFIG			0x20
+#define PPKB_SYS_CONFIG_DISABLE_SCAN		BIT(0)
+#define PPKB_SYS_SMBUS_COMMAND		0x21
+#define PPKB_SYS_SMBUS_DATA		0x22
+#define PPKB_SYS_COMMAND		0x23
+#define PPKB_SYS_COMMAND_SMBUS_READ		0x91
+#define PPKB_SYS_COMMAND_SMBUS_WRITE		0xa1
+
+#define PPKB_ROWS			6
+#define PPKB_COLS			12
+
+/* Size of the scan buffer, including the CRC byte at the beginning. */
+#define PPKB_BUF_LEN			(1 + PPKB_COLS)
+
+static const uint32_t ppkb_keymap[] = {
+	KEY(0,  0, KEY_ESC),
+	KEY(0,  1, KEY_1),
+	KEY(0,  2, KEY_2),
+	KEY(0,  3, KEY_3),
+	KEY(0,  4, KEY_4),
+	KEY(0,  5, KEY_5),
+	KEY(0,  6, KEY_6),
+	KEY(0,  7, KEY_7),
+	KEY(0,  8, KEY_8),
+	KEY(0,  9, KEY_9),
+	KEY(0, 10, KEY_0),
+	KEY(0, 11, KEY_BACKSPACE),
+
+	KEY(1,  0, KEY_TAB),
+	KEY(1,  1, KEY_Q),
+	KEY(1,  2, KEY_W),
+	KEY(1,  3, KEY_E),
+	KEY(1,  4, KEY_R),
+	KEY(1,  5, KEY_T),
+	KEY(1,  6, KEY_Y),
+	KEY(1,  7, KEY_U),
+	KEY(1,  8, KEY_I),
+	KEY(1,  9, KEY_O),
+	KEY(1, 10, KEY_P),
+	KEY(1, 11, KEY_ENTER),
+
+	KEY(2,  0, KEY_LEFTMETA),
+	KEY(2,  1, KEY_A),
+	KEY(2,  2, KEY_S),
+	KEY(2,  3, KEY_D),
+	KEY(2,  4, KEY_F),
+	KEY(2,  5, KEY_G),
+	KEY(2,  6, KEY_H),
+	KEY(2,  7, KEY_J),
+	KEY(2,  8, KEY_K),
+	KEY(2,  9, KEY_L),
+	KEY(2, 10, KEY_SEMICOLON),
+
+	KEY(3,  0, KEY_LEFTSHIFT),
+	KEY(3,  1, KEY_Z),
+	KEY(3,  2, KEY_X),
+	KEY(3,  3, KEY_C),
+	KEY(3,  4, KEY_V),
+	KEY(3,  5, KEY_B),
+	KEY(3,  6, KEY_N),
+	KEY(3,  7, KEY_M),
+	KEY(3,  8, KEY_COMMA),
+	KEY(3,  9, KEY_DOT),
+	KEY(3, 10, KEY_SLASH),
+
+	KEY(4,  1, KEY_LEFTCTRL),
+	KEY(4,  4, KEY_SPACE),
+	KEY(4,  6, KEY_APOSTROPHE),
+	KEY(4,  8, KEY_RIGHTBRACE),
+	KEY(4,  9, KEY_LEFTBRACE),
+
+	KEY(5,  2, KEY_FN),
+	KEY(5,  3, KEY_LEFTALT),
+	KEY(5,  5, KEY_RIGHTALT),
+
+	/* FN layer */
+	KEY(PPKB_ROWS + 0,  0, KEY_FN_ESC),
+	KEY(PPKB_ROWS + 0,  1, KEY_F1),
+	KEY(PPKB_ROWS + 0,  2, KEY_F2),
+	KEY(PPKB_ROWS + 0,  3, KEY_F3),
+	KEY(PPKB_ROWS + 0,  4, KEY_F4),
+	KEY(PPKB_ROWS + 0,  5, KEY_F5),
+	KEY(PPKB_ROWS + 0,  6, KEY_F6),
+	KEY(PPKB_ROWS + 0,  7, KEY_F7),
+	KEY(PPKB_ROWS + 0,  8, KEY_F8),
+	KEY(PPKB_ROWS + 0,  9, KEY_F9),
+	KEY(PPKB_ROWS + 0, 10, KEY_F10),
+	KEY(PPKB_ROWS + 0, 11, KEY_DELETE),
+
+	KEY(PPKB_ROWS + 1, 10, KEY_PAGEUP),
+
+	KEY(PPKB_ROWS + 2,  0, KEY_SYSRQ),
+	KEY(PPKB_ROWS + 2,  9, KEY_PAGEDOWN),
+	KEY(PPKB_ROWS + 2, 10, KEY_INSERT),
+
+	KEY(PPKB_ROWS + 3,  0, KEY_LEFTSHIFT),
+	KEY(PPKB_ROWS + 3,  8, KEY_HOME),
+	KEY(PPKB_ROWS + 3,  9, KEY_UP),
+	KEY(PPKB_ROWS + 3, 10, KEY_END),
+
+	KEY(PPKB_ROWS + 4, 1, KEY_LEFTCTRL),
+	KEY(PPKB_ROWS + 4, 6, KEY_LEFT),
+	KEY(PPKB_ROWS + 4, 8, KEY_RIGHT),
+	KEY(PPKB_ROWS + 4, 9, KEY_DOWN),
+
+	KEY(PPKB_ROWS + 5, 3, KEY_LEFTALT),
+	KEY(PPKB_ROWS + 5, 5, KEY_RIGHTALT),
+};
+
+static const struct matrix_keymap_data ppkb_keymap_data = {
+	.keymap		= ppkb_keymap,
+	.keymap_size	= ARRAY_SIZE(ppkb_keymap),
+};
+
+struct pinephone_keyboard {
+	struct i2c_adapter adapter;
+	struct input_dev *input;
+	u8 buf[2][PPKB_BUF_LEN];
+	u8 crc_table[CRC8_TABLE_SIZE];
+	u8 fn_state[PPKB_COLS];
+	bool buf_swap;
+	bool fn_pressed;
+};
+
+static int ppkb_adap_smbus_xfer(struct i2c_adapter *adap, u16 addr,
+				unsigned short flags, char read_write,
+				u8 command, int size,
+				union i2c_smbus_data *data)
+{
+	struct i2c_client *client = adap->algo_data;
+	u8 buf[3];
+	int ret;
+
+	buf[0] = command;
+	buf[1] = data->byte;
+	buf[2] = read_write == I2C_SMBUS_READ ? PPKB_SYS_COMMAND_SMBUS_READ
+					      : PPKB_SYS_COMMAND_SMBUS_WRITE;
+
+	ret = i2c_smbus_write_i2c_block_data(client, PPKB_SYS_SMBUS_COMMAND,
+					     sizeof(buf), buf);
+	if (ret)
+		return ret;
+
+	/* Read back the command status until it passes or fails. */
+	do {
+		usleep_range(300, 500);
+		ret = i2c_smbus_read_byte_data(client, PPKB_SYS_COMMAND);
+	} while (ret == buf[2]);
+	if (ret < 0)
+		return ret;
+	/* Commands return 0x00 on success and 0xff on failure. */
+	if (ret)
+		return -EIO;
+
+	if (read_write == I2C_SMBUS_READ) {
+		ret = i2c_smbus_read_byte_data(client, PPKB_SYS_SMBUS_DATA);
+		if (ret < 0)
+			return ret;
+
+		data->byte = ret;
+	}
+
+	return 0;
+}
+
+static u32 ppkg_adap_functionality(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_SMBUS_BYTE_DATA;
+}
+
+static const struct i2c_algorithm ppkb_adap_algo = {
+	.smbus_xfer		= ppkb_adap_smbus_xfer,
+	.functionality		= ppkg_adap_functionality,
+};
+
+static void ppkb_update(struct i2c_client *client)
+{
+	struct pinephone_keyboard *ppkb = i2c_get_clientdata(client);
+	unsigned short *keymap = ppkb->input->keycode;
+	int row_shift = get_count_order(PPKB_COLS);
+	u8 *old_buf = ppkb->buf[!ppkb->buf_swap];
+	u8 *new_buf = ppkb->buf[ppkb->buf_swap];
+	int col, crc, ret, row;
+	struct device *dev = &client->dev;
+
+	ret = i2c_smbus_read_i2c_block_data(client, PPKB_SCAN_CRC,
+					    PPKB_BUF_LEN, new_buf);
+	if (ret != PPKB_BUF_LEN) {
+		dev_err(dev, "Failed to read scan data: %d\n", ret);
+		return;
+	}
+
+	crc = crc8(ppkb->crc_table, &new_buf[1], PPKB_COLS, CRC8_INIT_VALUE);
+	if (crc != new_buf[0]) {
+		dev_err(dev, "Bad scan data (%02x != %02x)\n", crc, new_buf[0]);
+		return;
+	}
+
+	ppkb->buf_swap = !ppkb->buf_swap;
+
+	for (col = 0; col < PPKB_COLS; ++col) {
+		u8 old = old_buf[1 + col];
+		u8 new = new_buf[1 + col];
+		u8 changed = old ^ new;
+
+		if (!changed)
+			continue;
+
+		for (row = 0; row < PPKB_ROWS; ++row) {
+			u8 mask = BIT(row);
+			u8 value = new & mask;
+			unsigned short code;
+			bool fn_state;
+
+			if (!(changed & mask))
+				continue;
+
+			/*
+			 * Save off the FN key state when the key was pressed,
+			 * and use that to determine the code during a release.
+			 */
+			fn_state = value ? ppkb->fn_pressed : ppkb->fn_state[col] & mask;
+			if (fn_state)
+				ppkb->fn_state[col] ^= mask;
+
+			/* The FN layer is a second set of rows. */
+			code = MATRIX_SCAN_CODE(fn_state ? PPKB_ROWS + row : row,
+						col, row_shift);
+			input_event(ppkb->input, EV_MSC, MSC_SCAN, code);
+			input_report_key(ppkb->input, keymap[code], value);
+			if (keymap[code] == KEY_FN)
+				ppkb->fn_pressed = value;
+		}
+	}
+	input_sync(ppkb->input);
+}
+
+static irqreturn_t ppkb_irq_thread(int irq, void *data)
+{
+	struct i2c_client *client = data;
+
+	ppkb_update(client);
+
+	return IRQ_HANDLED;
+}
+
+static int ppkb_set_scan(struct i2c_client *client, bool enable)
+{
+	struct device *dev = &client->dev;
+	int ret, val;
+
+	ret = i2c_smbus_read_byte_data(client, PPKB_SYS_CONFIG);
+	if (ret < 0) {
+		dev_err(dev, "Failed to read config: %d\n", ret);
+		return ret;
+	}
+
+	if (enable)
+		val = ret & ~PPKB_SYS_CONFIG_DISABLE_SCAN;
+	else
+		val = ret | PPKB_SYS_CONFIG_DISABLE_SCAN;
+
+	ret = i2c_smbus_write_byte_data(client, PPKB_SYS_CONFIG, val);
+	if (ret) {
+		dev_err(dev, "Failed to write config: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int ppkb_open(struct input_dev *input)
+{
+	struct i2c_client *client = input_get_drvdata(input);
+	int error;
+
+	error = ppkb_set_scan(client, true);
+	if (error)
+		return error;
+
+	return 0;
+}
+
+static void ppkb_close(struct input_dev *input)
+{
+	struct i2c_client *client = input_get_drvdata(input);
+
+	ppkb_set_scan(client, false);
+}
+
+static int ppkb_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	unsigned int phys_rows, phys_cols;
+	struct pinephone_keyboard *ppkb;
+	u8 info[PPKB_MATRIX_SIZE + 1];
+	struct device_node *i2c_bus;
+	int ret;
+	int error;
+
+	error = devm_regulator_get_enable(dev, "vbat");
+	if (error) {
+		dev_err(dev, "Failed to get VBAT supply: %d\n", error);
+		return error;
+	}
+
+	ret = i2c_smbus_read_i2c_block_data(client, 0, sizeof(info), info);
+	if (ret != sizeof(info)) {
+		error = ret < 0 ? ret : -EIO;
+		dev_err(dev, "Failed to read device ID: %d\n", error);
+		return error;
+	}
+
+	if (info[PPKB_DEVICE_ID_HI] != PPKB_DEVICE_ID_HI_VALUE ||
+	    info[PPKB_DEVICE_ID_LO] != PPKB_DEVICE_ID_LO_VALUE) {
+		dev_warn(dev, "Unexpected device ID: %#02x %#02x\n",
+			 info[PPKB_DEVICE_ID_HI], info[PPKB_DEVICE_ID_LO]);
+		return -ENODEV;
+	}
+
+	dev_info(dev, "Found firmware version %d.%d features %#x\n",
+		 info[PPKB_FW_REVISION] >> 4,
+		 info[PPKB_FW_REVISION] & 0xf,
+		 info[PPKB_FW_FEATURES]);
+
+	phys_rows = info[PPKB_MATRIX_SIZE] & 0xf;
+	phys_cols = info[PPKB_MATRIX_SIZE] >> 4;
+	if (phys_rows != PPKB_ROWS || phys_cols != PPKB_COLS) {
+		dev_err(dev, "Unexpected keyboard size %ux%u\n",
+			phys_rows, phys_cols);
+		return -EINVAL;
+	}
+
+	/* Disable scan by default to save power. */
+	error = ppkb_set_scan(client, false);
+	if (error)
+		return error;
+
+	ppkb = devm_kzalloc(dev, sizeof(*ppkb), GFP_KERNEL);
+	if (!ppkb)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, ppkb);
+
+	i2c_bus = of_get_child_by_name(dev->of_node, "i2c");
+	if (i2c_bus) {
+		ppkb->adapter.owner = THIS_MODULE;
+		ppkb->adapter.algo = &ppkb_adap_algo;
+		ppkb->adapter.algo_data = client;
+		ppkb->adapter.dev.parent = dev;
+		ppkb->adapter.dev.of_node = i2c_bus;
+		strscpy(ppkb->adapter.name, DRV_NAME, sizeof(ppkb->adapter.name));
+
+		error = devm_i2c_add_adapter(dev, &ppkb->adapter);
+		if (error) {
+			dev_err(dev, "Failed to add I2C adapter: %d\n", error);
+			return error;
+		}
+	}
+
+	crc8_populate_msb(ppkb->crc_table, PPKB_CRC8_POLYNOMIAL);
+
+	ppkb->input = devm_input_allocate_device(dev);
+	if (!ppkb->input)
+		return -ENOMEM;
+
+	input_set_drvdata(ppkb->input, client);
+
+	ppkb->input->name = "PinePhone Keyboard";
+	ppkb->input->phys = DRV_NAME "/input0";
+	ppkb->input->id.bustype = BUS_I2C;
+	ppkb->input->open = ppkb_open;
+	ppkb->input->close = ppkb_close;
+
+	input_set_capability(ppkb->input, EV_MSC, MSC_SCAN);
+	__set_bit(EV_REP, ppkb->input->evbit);
+
+	error = matrix_keypad_build_keymap(&ppkb_keymap_data, NULL,
+					   2 * PPKB_ROWS, PPKB_COLS, NULL,
+					   ppkb->input);
+	if (error) {
+		dev_err(dev, "Failed to build keymap: %d\n", error);
+		return error;
+	}
+
+	error = input_register_device(ppkb->input);
+	if (error) {
+		dev_err(dev, "Failed to register input: %d\n", error);
+		return error;
+	}
+
+	error = devm_request_threaded_irq(dev, client->irq,
+					  NULL, ppkb_irq_thread,
+					  IRQF_ONESHOT, client->name, client);
+	if (error) {
+		dev_err(dev, "Failed to request IRQ: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id ppkb_of_match[] = {
+	{ .compatible = "pine64,pinephone-keyboard" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ppkb_of_match);
+
+static struct i2c_driver ppkb_driver = {
+	.probe		= ppkb_probe,
+	.driver		= {
+		.name		= DRV_NAME,
+		.of_match_table = ppkb_of_match,
+	},
+};
+module_i2c_driver(ppkb_driver);
+
+MODULE_AUTHOR("Samuel Holland <samuel@sholland.org>");
+MODULE_DESCRIPTION("Pine64 PinePhone keyboard driver");
+MODULE_LICENSE("GPL");