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, 481 insertions, 0 deletions

diff --git a/drivers/misc/ics932s401.c b/drivers/misc/ics932s401.c
new file mode 100644
index 000000000..015710762
--- /dev/null
+++ b/drivers/misc/ics932s401.c
@@ -0,0 +1,481 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * A driver for the Integrated Circuits ICS932S401
+ * Copyright (C) 2008 IBM
+ *
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ */
+
+#include <linux/module.h>
+#include <linux/jiffies.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+#include <linux/delay.h>
+#include <linux/log2.h>
+#include <linux/slab.h>
+
+/* Addresses to scan */
+static const unsigned short normal_i2c[] = { 0x69, I2C_CLIENT_END };
+
+/* ICS932S401 registers */
+#define ICS932S401_REG_CFG2			0x01
+#define		ICS932S401_CFG1_SPREAD		0x01
+#define ICS932S401_REG_CFG7			0x06
+#define		ICS932S401_FS_MASK		0x07
+#define	ICS932S401_REG_VENDOR_REV		0x07
+#define		ICS932S401_VENDOR		1
+#define		ICS932S401_VENDOR_MASK		0x0F
+#define		ICS932S401_REV			4
+#define		ICS932S401_REV_SHIFT		4
+#define ICS932S401_REG_DEVICE			0x09
+#define		ICS932S401_DEVICE		11
+#define	ICS932S401_REG_CTRL			0x0A
+#define		ICS932S401_MN_ENABLED		0x80
+#define		ICS932S401_CPU_ALT		0x04
+#define		ICS932S401_SRC_ALT		0x08
+#define ICS932S401_REG_CPU_M_CTRL		0x0B
+#define		ICS932S401_M_MASK		0x3F
+#define	ICS932S401_REG_CPU_N_CTRL		0x0C
+#define	ICS932S401_REG_CPU_SPREAD1		0x0D
+#define ICS932S401_REG_CPU_SPREAD2		0x0E
+#define		ICS932S401_SPREAD_MASK		0x7FFF
+#define ICS932S401_REG_SRC_M_CTRL		0x0F
+#define ICS932S401_REG_SRC_N_CTRL		0x10
+#define	ICS932S401_REG_SRC_SPREAD1		0x11
+#define ICS932S401_REG_SRC_SPREAD2		0x12
+#define ICS932S401_REG_CPU_DIVISOR		0x13
+#define		ICS932S401_CPU_DIVISOR_SHIFT	4
+#define ICS932S401_REG_PCISRC_DIVISOR		0x14
+#define		ICS932S401_SRC_DIVISOR_MASK	0x0F
+#define		ICS932S401_PCI_DIVISOR_SHIFT	4
+
+/* Base clock is 14.318MHz */
+#define BASE_CLOCK				14318
+
+#define NUM_REGS				21
+#define NUM_MIRRORED_REGS			15
+
+static int regs_to_copy[NUM_MIRRORED_REGS] = {
+	ICS932S401_REG_CFG2,
+	ICS932S401_REG_CFG7,
+	ICS932S401_REG_VENDOR_REV,
+	ICS932S401_REG_DEVICE,
+	ICS932S401_REG_CTRL,
+	ICS932S401_REG_CPU_M_CTRL,
+	ICS932S401_REG_CPU_N_CTRL,
+	ICS932S401_REG_CPU_SPREAD1,
+	ICS932S401_REG_CPU_SPREAD2,
+	ICS932S401_REG_SRC_M_CTRL,
+	ICS932S401_REG_SRC_N_CTRL,
+	ICS932S401_REG_SRC_SPREAD1,
+	ICS932S401_REG_SRC_SPREAD2,
+	ICS932S401_REG_CPU_DIVISOR,
+	ICS932S401_REG_PCISRC_DIVISOR,
+};
+
+/* How often do we reread sensors values? (In jiffies) */
+#define SENSOR_REFRESH_INTERVAL	(2 * HZ)
+
+/* How often do we reread sensor limit values? (In jiffies) */
+#define LIMIT_REFRESH_INTERVAL	(60 * HZ)
+
+struct ics932s401_data {
+	struct attribute_group	attrs;
+	struct mutex		lock;
+	char			sensors_valid;
+	unsigned long		sensors_last_updated;	/* In jiffies */
+
+	u8			regs[NUM_REGS];
+};
+
+static int ics932s401_probe(struct i2c_client *client);
+static int ics932s401_detect(struct i2c_client *client,
+			  struct i2c_board_info *info);
+static void ics932s401_remove(struct i2c_client *client);
+
+static const struct i2c_device_id ics932s401_id[] = {
+	{ "ics932s401" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ics932s401_id);
+
+static struct i2c_driver ics932s401_driver = {
+	.class		= I2C_CLASS_HWMON,
+	.driver = {
+		.name	= "ics932s401",
+	},
+	.probe		= ics932s401_probe,
+	.remove		= ics932s401_remove,
+	.id_table	= ics932s401_id,
+	.detect		= ics932s401_detect,
+	.address_list	= normal_i2c,
+};
+
+static struct ics932s401_data *ics932s401_update_device(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct ics932s401_data *data = i2c_get_clientdata(client);
+	unsigned long local_jiffies = jiffies;
+	int i, temp;
+
+	mutex_lock(&data->lock);
+	if (time_before(local_jiffies, data->sensors_last_updated +
+		SENSOR_REFRESH_INTERVAL)
+		&& data->sensors_valid)
+		goto out;
+
+	/*
+	 * Each register must be read as a word and then right shifted 8 bits.
+	 * Not really sure why this is; setting the "byte count programming"
+	 * register to 1 does not fix this problem.
+	 */
+	for (i = 0; i < NUM_MIRRORED_REGS; i++) {
+		temp = i2c_smbus_read_word_data(client, regs_to_copy[i]);
+		if (temp < 0)
+			temp = 0;
+		data->regs[regs_to_copy[i]] = temp >> 8;
+	}
+
+	data->sensors_last_updated = local_jiffies;
+	data->sensors_valid = 1;
+
+out:
+	mutex_unlock(&data->lock);
+	return data;
+}
+
+static ssize_t show_spread_enabled(struct device *dev,
+				   struct device_attribute *devattr,
+				   char *buf)
+{
+	struct ics932s401_data *data = ics932s401_update_device(dev);
+
+	if (data->regs[ICS932S401_REG_CFG2] & ICS932S401_CFG1_SPREAD)
+		return sprintf(buf, "1\n");
+
+	return sprintf(buf, "0\n");
+}
+
+/* bit to cpu khz map */
+static const int fs_speeds[] = {
+	266666,
+	133333,
+	200000,
+	166666,
+	333333,
+	100000,
+	400000,
+	0,
+};
+
+/* clock divisor map */
+static const int divisors[] = {2, 3, 5, 15, 4, 6, 10, 30, 8, 12, 20, 60, 16,
+			       24, 40, 120};
+
+/* Calculate CPU frequency from the M/N registers. */
+static int calculate_cpu_freq(struct ics932s401_data *data)
+{
+	int m, n, freq;
+
+	m = data->regs[ICS932S401_REG_CPU_M_CTRL] & ICS932S401_M_MASK;
+	n = data->regs[ICS932S401_REG_CPU_N_CTRL];
+
+	/* Pull in bits 8 & 9 from the M register */
+	n |= ((int)data->regs[ICS932S401_REG_CPU_M_CTRL] & 0x80) << 1;
+	n |= ((int)data->regs[ICS932S401_REG_CPU_M_CTRL] & 0x40) << 3;
+
+	freq = BASE_CLOCK * (n + 8) / (m + 2);
+	freq /= divisors[data->regs[ICS932S401_REG_CPU_DIVISOR] >>
+			 ICS932S401_CPU_DIVISOR_SHIFT];
+
+	return freq;
+}
+
+static ssize_t show_cpu_clock(struct device *dev,
+			      struct device_attribute *devattr,
+			      char *buf)
+{
+	struct ics932s401_data *data = ics932s401_update_device(dev);
+
+	return sprintf(buf, "%d\n", calculate_cpu_freq(data));
+}
+
+static ssize_t show_cpu_clock_sel(struct device *dev,
+				  struct device_attribute *devattr,
+				  char *buf)
+{
+	struct ics932s401_data *data = ics932s401_update_device(dev);
+	int freq;
+
+	if (data->regs[ICS932S401_REG_CTRL] & ICS932S401_MN_ENABLED)
+		freq = calculate_cpu_freq(data);
+	else {
+		/* Freq is neatly wrapped up for us */
+		int fid = data->regs[ICS932S401_REG_CFG7] & ICS932S401_FS_MASK;
+
+		freq = fs_speeds[fid];
+		if (data->regs[ICS932S401_REG_CTRL] & ICS932S401_CPU_ALT) {
+			switch (freq) {
+			case 166666:
+				freq = 160000;
+				break;
+			case 333333:
+				freq = 320000;
+				break;
+			}
+		}
+	}
+
+	return sprintf(buf, "%d\n", freq);
+}
+
+/* Calculate SRC frequency from the M/N registers. */
+static int calculate_src_freq(struct ics932s401_data *data)
+{
+	int m, n, freq;
+
+	m = data->regs[ICS932S401_REG_SRC_M_CTRL] & ICS932S401_M_MASK;
+	n = data->regs[ICS932S401_REG_SRC_N_CTRL];
+
+	/* Pull in bits 8 & 9 from the M register */
+	n |= ((int)data->regs[ICS932S401_REG_SRC_M_CTRL] & 0x80) << 1;
+	n |= ((int)data->regs[ICS932S401_REG_SRC_M_CTRL] & 0x40) << 3;
+
+	freq = BASE_CLOCK * (n + 8) / (m + 2);
+	freq /= divisors[data->regs[ICS932S401_REG_PCISRC_DIVISOR] &
+			 ICS932S401_SRC_DIVISOR_MASK];
+
+	return freq;
+}
+
+static ssize_t show_src_clock(struct device *dev,
+			      struct device_attribute *devattr,
+			      char *buf)
+{
+	struct ics932s401_data *data = ics932s401_update_device(dev);
+
+	return sprintf(buf, "%d\n", calculate_src_freq(data));
+}
+
+static ssize_t show_src_clock_sel(struct device *dev,
+				  struct device_attribute *devattr,
+				  char *buf)
+{
+	struct ics932s401_data *data = ics932s401_update_device(dev);
+	int freq;
+
+	if (data->regs[ICS932S401_REG_CTRL] & ICS932S401_MN_ENABLED)
+		freq = calculate_src_freq(data);
+	else
+		/* Freq is neatly wrapped up for us */
+		if (data->regs[ICS932S401_REG_CTRL] & ICS932S401_CPU_ALT &&
+		    data->regs[ICS932S401_REG_CTRL] & ICS932S401_SRC_ALT)
+			freq = 96000;
+		else
+			freq = 100000;
+
+	return sprintf(buf, "%d\n", freq);
+}
+
+/* Calculate PCI frequency from the SRC M/N registers. */
+static int calculate_pci_freq(struct ics932s401_data *data)
+{
+	int m, n, freq;
+
+	m = data->regs[ICS932S401_REG_SRC_M_CTRL] & ICS932S401_M_MASK;
+	n = data->regs[ICS932S401_REG_SRC_N_CTRL];
+
+	/* Pull in bits 8 & 9 from the M register */
+	n |= ((int)data->regs[ICS932S401_REG_SRC_M_CTRL] & 0x80) << 1;
+	n |= ((int)data->regs[ICS932S401_REG_SRC_M_CTRL] & 0x40) << 3;
+
+	freq = BASE_CLOCK * (n + 8) / (m + 2);
+	freq /= divisors[data->regs[ICS932S401_REG_PCISRC_DIVISOR] >>
+			 ICS932S401_PCI_DIVISOR_SHIFT];
+
+	return freq;
+}
+
+static ssize_t show_pci_clock(struct device *dev,
+			      struct device_attribute *devattr,
+			      char *buf)
+{
+	struct ics932s401_data *data = ics932s401_update_device(dev);
+
+	return sprintf(buf, "%d\n", calculate_pci_freq(data));
+}
+
+static ssize_t show_pci_clock_sel(struct device *dev,
+				  struct device_attribute *devattr,
+				  char *buf)
+{
+	struct ics932s401_data *data = ics932s401_update_device(dev);
+	int freq;
+
+	if (data->regs[ICS932S401_REG_CTRL] & ICS932S401_MN_ENABLED)
+		freq = calculate_pci_freq(data);
+	else
+		freq = 33333;
+
+	return sprintf(buf, "%d\n", freq);
+}
+
+static ssize_t show_value(struct device *dev,
+			  struct device_attribute *devattr,
+			  char *buf);
+
+static ssize_t show_spread(struct device *dev,
+			   struct device_attribute *devattr,
+			   char *buf);
+
+static DEVICE_ATTR(spread_enabled, S_IRUGO, show_spread_enabled, NULL);
+static DEVICE_ATTR(cpu_clock_selection, S_IRUGO, show_cpu_clock_sel, NULL);
+static DEVICE_ATTR(cpu_clock, S_IRUGO, show_cpu_clock, NULL);
+static DEVICE_ATTR(src_clock_selection, S_IRUGO, show_src_clock_sel, NULL);
+static DEVICE_ATTR(src_clock, S_IRUGO, show_src_clock, NULL);
+static DEVICE_ATTR(pci_clock_selection, S_IRUGO, show_pci_clock_sel, NULL);
+static DEVICE_ATTR(pci_clock, S_IRUGO, show_pci_clock, NULL);
+static DEVICE_ATTR(usb_clock, S_IRUGO, show_value, NULL);
+static DEVICE_ATTR(ref_clock, S_IRUGO, show_value, NULL);
+static DEVICE_ATTR(cpu_spread, S_IRUGO, show_spread, NULL);
+static DEVICE_ATTR(src_spread, S_IRUGO, show_spread, NULL);
+
+static struct attribute *ics932s401_attr[] = {
+	&dev_attr_spread_enabled.attr,
+	&dev_attr_cpu_clock_selection.attr,
+	&dev_attr_cpu_clock.attr,
+	&dev_attr_src_clock_selection.attr,
+	&dev_attr_src_clock.attr,
+	&dev_attr_pci_clock_selection.attr,
+	&dev_attr_pci_clock.attr,
+	&dev_attr_usb_clock.attr,
+	&dev_attr_ref_clock.attr,
+	&dev_attr_cpu_spread.attr,
+	&dev_attr_src_spread.attr,
+	NULL
+};
+
+static ssize_t show_value(struct device *dev,
+			  struct device_attribute *devattr,
+			  char *buf)
+{
+	int x;
+
+	if (devattr == &dev_attr_usb_clock)
+		x = 48000;
+	else if (devattr == &dev_attr_ref_clock)
+		x = BASE_CLOCK;
+	else
+		BUG();
+
+	return sprintf(buf, "%d\n", x);
+}
+
+static ssize_t show_spread(struct device *dev,
+			   struct device_attribute *devattr,
+			   char *buf)
+{
+	struct ics932s401_data *data = ics932s401_update_device(dev);
+	int reg;
+	unsigned long val;
+
+	if (!(data->regs[ICS932S401_REG_CFG2] & ICS932S401_CFG1_SPREAD))
+		return sprintf(buf, "0%%\n");
+
+	if (devattr == &dev_attr_src_spread)
+		reg = ICS932S401_REG_SRC_SPREAD1;
+	else if (devattr == &dev_attr_cpu_spread)
+		reg = ICS932S401_REG_CPU_SPREAD1;
+	else
+		BUG();
+
+	val = data->regs[reg] | (data->regs[reg + 1] << 8);
+	val &= ICS932S401_SPREAD_MASK;
+
+	/* Scale 0..2^14 to -0.5. */
+	val = 500000 * val / 16384;
+	return sprintf(buf, "-0.%lu%%\n", val);
+}
+
+/* Return 0 if detection is successful, -ENODEV otherwise */
+static int ics932s401_detect(struct i2c_client *client,
+			  struct i2c_board_info *info)
+{
+	struct i2c_adapter *adapter = client->adapter;
+	int vendor, device, revision;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -ENODEV;
+
+	vendor = i2c_smbus_read_word_data(client, ICS932S401_REG_VENDOR_REV);
+	vendor >>= 8;
+	revision = vendor >> ICS932S401_REV_SHIFT;
+	vendor &= ICS932S401_VENDOR_MASK;
+	if (vendor != ICS932S401_VENDOR)
+		return -ENODEV;
+
+	device = i2c_smbus_read_word_data(client, ICS932S401_REG_DEVICE);
+	device >>= 8;
+	if (device != ICS932S401_DEVICE)
+		return -ENODEV;
+
+	if (revision != ICS932S401_REV)
+		dev_info(&adapter->dev, "Unknown revision %d\n", revision);
+
+	strscpy(info->type, "ics932s401", I2C_NAME_SIZE);
+
+	return 0;
+}
+
+static int ics932s401_probe(struct i2c_client *client)
+{
+	struct ics932s401_data *data;
+	int err;
+
+	data = kzalloc_obj(struct ics932s401_data);
+	if (!data) {
+		err = -ENOMEM;
+		goto exit;
+	}
+
+	i2c_set_clientdata(client, data);
+	mutex_init(&data->lock);
+
+	dev_info(&client->dev, "%s chip found\n", client->name);
+
+	/* Register sysfs hooks */
+	data->attrs.attrs = ics932s401_attr;
+	err = sysfs_create_group(&client->dev.kobj, &data->attrs);
+	if (err)
+		goto exit_free;
+
+	return 0;
+
+exit_free:
+	kfree(data);
+exit:
+	return err;
+}
+
+static void ics932s401_remove(struct i2c_client *client)
+{
+	struct ics932s401_data *data = i2c_get_clientdata(client);
+
+	sysfs_remove_group(&client->dev.kobj, &data->attrs);
+	kfree(data);
+}
+
+module_i2c_driver(ics932s401_driver);
+
+MODULE_AUTHOR("Darrick J. Wong <darrick.wong@oracle.com>");
+MODULE_DESCRIPTION("ICS932S401 driver");
+MODULE_LICENSE("GPL");
+
+/* IBM IntelliStation Z30 */
+MODULE_ALIAS("dmi:bvnIBM:*:rn9228:*");
+MODULE_ALIAS("dmi:bvnIBM:*:rn9232:*");
+
+/* IBM x3650/x3550 */
+MODULE_ALIAS("dmi:bvnIBM:*:pnIBMSystemx3650*");
+MODULE_ALIAS("dmi:bvnIBM:*:pnIBMSystemx3550*");