x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 530 insertions, 0 deletions

diff --git a/drivers/hwmon/ltc2945.c b/drivers/hwmon/ltc2945.c
new file mode 100644
index 000000000..b521100af
--- /dev/null
+++ b/drivers/hwmon/ltc2945.c
@@ -0,0 +1,530 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for Linear Technology LTC2945 I2C Power Monitor
+ *
+ * Copyright (c) 2014 Guenter Roeck
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/jiffies.h>
+#include <linux/regmap.h>
+
+/* chip registers */
+#define LTC2945_CONTROL			0x00
+#define LTC2945_ALERT			0x01
+#define LTC2945_STATUS			0x02
+#define LTC2945_FAULT			0x03
+#define LTC2945_POWER_H			0x05
+#define LTC2945_MAX_POWER_H		0x08
+#define LTC2945_MIN_POWER_H		0x0b
+#define LTC2945_MAX_POWER_THRES_H	0x0e
+#define LTC2945_MIN_POWER_THRES_H	0x11
+#define LTC2945_SENSE_H			0x14
+#define LTC2945_MAX_SENSE_H		0x16
+#define LTC2945_MIN_SENSE_H		0x18
+#define LTC2945_MAX_SENSE_THRES_H	0x1a
+#define LTC2945_MIN_SENSE_THRES_H	0x1c
+#define LTC2945_VIN_H			0x1e
+#define LTC2945_MAX_VIN_H		0x20
+#define LTC2945_MIN_VIN_H		0x22
+#define LTC2945_MAX_VIN_THRES_H		0x24
+#define LTC2945_MIN_VIN_THRES_H		0x26
+#define LTC2945_ADIN_H			0x28
+#define LTC2945_MAX_ADIN_H		0x2a
+#define LTC2945_MIN_ADIN_H		0x2c
+#define LTC2945_MAX_ADIN_THRES_H	0x2e
+#define LTC2945_MIN_ADIN_THRES_H	0x30
+#define LTC2945_MIN_ADIN_THRES_L	0x31
+
+/* Fault register bits */
+
+#define FAULT_ADIN_UV		(1 << 0)
+#define FAULT_ADIN_OV		(1 << 1)
+#define FAULT_VIN_UV		(1 << 2)
+#define FAULT_VIN_OV		(1 << 3)
+#define FAULT_SENSE_UV		(1 << 4)
+#define FAULT_SENSE_OV		(1 << 5)
+#define FAULT_POWER_UV		(1 << 6)
+#define FAULT_POWER_OV		(1 << 7)
+
+/* Control register bits */
+
+#define CONTROL_MULT_SELECT	(1 << 0)
+#define CONTROL_TEST_MODE	(1 << 4)
+
+static const struct of_device_id __maybe_unused ltc2945_of_match[] = {
+	{ .compatible = "adi,ltc2945" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ltc2945_of_match);
+
+/**
+ * struct ltc2945_data - LTC2945 device data
+ * @regmap: regmap device
+ * @shunt_resistor: shunt resistor value in micro ohms (1000 by default)
+ */
+struct ltc2945_data {
+	struct regmap *regmap;
+	u32 shunt_resistor;
+};
+
+static inline bool is_power_reg(u8 reg)
+{
+	return reg < LTC2945_SENSE_H;
+}
+
+/* Return the value from the given register in uW, mV, or mA */
+static long long ltc2945_reg_to_val(struct device *dev, u8 reg)
+{
+	struct ltc2945_data *data = dev_get_drvdata(dev);
+	struct regmap *regmap = data->regmap;
+	u32 shunt_resistor = data->shunt_resistor;
+	unsigned int control;
+	u8 buf[3];
+	long long val;
+	int ret;
+
+	ret = regmap_bulk_read(regmap, reg, buf,
+			       is_power_reg(reg) ? 3 : 2);
+	if (ret < 0)
+		return ret;
+
+	if (is_power_reg(reg)) {
+		/* 24-bit power */
+		val = (buf[0] << 16) + (buf[1] << 8) + buf[2];
+	} else {
+		/* 12-bit current, voltage */
+		val = (buf[0] << 4) + (buf[1] >> 4);
+	}
+
+	switch (reg) {
+	case LTC2945_POWER_H:
+	case LTC2945_MAX_POWER_H:
+	case LTC2945_MIN_POWER_H:
+	case LTC2945_MAX_POWER_THRES_H:
+	case LTC2945_MIN_POWER_THRES_H:
+		/*
+		 * Convert to uW
+		 * Control register bit 0 selects if voltage at SENSE+/VDD
+		 * or voltage at ADIN is used to measure power.
+		 */
+		ret = regmap_read(regmap, LTC2945_CONTROL, &control);
+		if (ret < 0)
+			return ret;
+		if (control & CONTROL_MULT_SELECT) {
+			/* 25 mV * 25 uV = 0.625 uV resolution. */
+			val *= 625LL;
+		} else {
+			/* 0.5 mV * 25 uV = 0.0125 uV resolution. */
+			val = (val * 25LL) >> 1;
+		}
+		val *= 1000;
+		/* Overflow check: Assuming max 24-bit power, val is at most 53 bits right now. */
+		val = DIV_ROUND_CLOSEST_ULL(val, shunt_resistor);
+		/*
+		 * Overflow check: After division, depending on shunt resistor,
+		 * val can still be > 32 bits so returning long long makes sense
+		 */
+
+		break;
+	case LTC2945_VIN_H:
+	case LTC2945_MAX_VIN_H:
+	case LTC2945_MIN_VIN_H:
+	case LTC2945_MAX_VIN_THRES_H:
+	case LTC2945_MIN_VIN_THRES_H:
+		/* 25 mV resolution. Convert to mV. */
+		val *= 25;
+		break;
+	case LTC2945_ADIN_H:
+	case LTC2945_MAX_ADIN_H:
+	case LTC2945_MIN_ADIN_THRES_H:
+	case LTC2945_MAX_ADIN_THRES_H:
+	case LTC2945_MIN_ADIN_H:
+		/* 0.5mV resolution. Convert to mV. */
+		val = val >> 1;
+		break;
+	case LTC2945_SENSE_H:
+	case LTC2945_MAX_SENSE_H:
+	case LTC2945_MIN_SENSE_H:
+	case LTC2945_MAX_SENSE_THRES_H:
+	case LTC2945_MIN_SENSE_THRES_H:
+		/* 25 uV resolution. Convert to mA. */
+		val *= 25 * 1000;
+		/* Overflow check: Assuming max 12-bit sense, val is at most 27 bits right now */
+		val = DIV_ROUND_CLOSEST_ULL(val, shunt_resistor);
+		/* Overflow check: After division, <= 27 bits */
+		break;
+	default:
+		return -EINVAL;
+	}
+	return val;
+}
+
+static long long ltc2945_val_to_reg(struct device *dev, u8 reg,
+				    unsigned long long val)
+{
+	struct ltc2945_data *data = dev_get_drvdata(dev);
+	struct regmap *regmap = data->regmap;
+	u32 shunt_resistor = data->shunt_resistor;
+	unsigned int control;
+	int ret;
+
+	/* Ensure we don't overflow */
+	val = clamp_val(val, 0, U32_MAX);
+
+	switch (reg) {
+	case LTC2945_POWER_H:
+	case LTC2945_MAX_POWER_H:
+	case LTC2945_MIN_POWER_H:
+	case LTC2945_MAX_POWER_THRES_H:
+	case LTC2945_MIN_POWER_THRES_H:
+		/*
+		 * Control register bit 0 selects if voltage at SENSE+/VDD
+		 * or voltage at ADIN is used to measure power, which in turn
+		 * determines register calculations.
+		 */
+		ret = regmap_read(regmap, LTC2945_CONTROL, &control);
+		if (ret < 0)
+			return ret;
+		if (control & CONTROL_MULT_SELECT) {
+			/* 25 mV * 25 uV = 0.625 uV resolution. */
+			val *= shunt_resistor;
+			/* Overflow check: Assuming 32-bit val and shunt resistor, val <= 64bits */
+			val = DIV_ROUND_CLOSEST_ULL(val, 625 * 1000);
+			/* Overflow check: val is now <= 44 bits */
+		} else {
+			/* 0.5 mV * 25 uV = 0.0125 uV resolution. */
+			val *= shunt_resistor;
+			/* Overflow check: Assuming 32-bit val and shunt resistor, val <= 64bits */
+			val = DIV_ROUND_CLOSEST_ULL(val, 25 * 1000) * 2;
+			/* Overflow check: val is now <= 51 bits */
+		}
+		break;
+	case LTC2945_VIN_H:
+	case LTC2945_MAX_VIN_H:
+	case LTC2945_MIN_VIN_H:
+	case LTC2945_MAX_VIN_THRES_H:
+	case LTC2945_MIN_VIN_THRES_H:
+		/* 25 mV resolution. */
+		val = DIV_ROUND_CLOSEST_ULL(val, 25);
+		break;
+	case LTC2945_ADIN_H:
+	case LTC2945_MAX_ADIN_H:
+	case LTC2945_MIN_ADIN_THRES_H:
+	case LTC2945_MAX_ADIN_THRES_H:
+	case LTC2945_MIN_ADIN_H:
+		/* 0.5mV resolution. */
+		val *= 2;
+		break;
+	case LTC2945_SENSE_H:
+	case LTC2945_MAX_SENSE_H:
+	case LTC2945_MIN_SENSE_H:
+	case LTC2945_MAX_SENSE_THRES_H:
+	case LTC2945_MIN_SENSE_THRES_H:
+		/* 25 uV resolution. Convert to  mA. */
+		val *= shunt_resistor;
+		/* Overflow check: Assuming 32-bit val and 32-bit shunt resistor, val is 64bits */
+		val = DIV_ROUND_CLOSEST_ULL(val, 25 * 1000);
+		/* Overflow check: val is now <= 50 bits */
+		break;
+	default:
+		return -EINVAL;
+	}
+	return val;
+}
+
+static ssize_t ltc2945_value_show(struct device *dev,
+				  struct device_attribute *da, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	long long value;
+
+	value = ltc2945_reg_to_val(dev, attr->index);
+	if (value < 0)
+		return value;
+	return sysfs_emit(buf, "%lld\n", value);
+}
+
+static ssize_t ltc2945_value_store(struct device *dev,
+				   struct device_attribute *da,
+				   const char *buf, size_t count)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	struct ltc2945_data *data = dev_get_drvdata(dev);
+	struct regmap *regmap = data->regmap;
+	u8 reg = attr->index;
+	unsigned int val;
+	u8 regbuf[3];
+	int num_regs;
+	long long regval;
+	int ret;
+
+	ret = kstrtouint(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	/* convert to register value, then clamp and write result */
+	regval = ltc2945_val_to_reg(dev, reg, val);
+	if (regval < 0)
+		return regval;
+	if (is_power_reg(reg)) {
+		regval = clamp_val(regval, 0, 0xffffff);
+		regbuf[0] = regval >> 16;
+		regbuf[1] = (regval >> 8) & 0xff;
+		regbuf[2] = regval;
+		num_regs = 3;
+	} else {
+		regval = clamp_val(regval, 0, 0xfff) << 4;
+		regbuf[0] = regval >> 8;
+		regbuf[1] = regval & 0xff;
+		num_regs = 2;
+	}
+	ret = regmap_bulk_write(regmap, reg, regbuf, num_regs);
+	return ret < 0 ? ret : count;
+}
+
+static ssize_t ltc2945_history_store(struct device *dev,
+				     struct device_attribute *da,
+				     const char *buf, size_t count)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	struct ltc2945_data *data = dev_get_drvdata(dev);
+	struct regmap *regmap = data->regmap;
+	u8 reg = attr->index;
+	int num_regs = is_power_reg(reg) ? 3 : 2;
+	u8 buf_min[3] = { 0xff, 0xff, 0xff };
+	u8 buf_max[3] = { 0, 0, 0 };
+	unsigned long val;
+	int ret;
+
+	ret = kstrtoul(buf, 10, &val);
+	if (ret)
+		return ret;
+	if (val != 1)
+		return -EINVAL;
+
+	ret = regmap_update_bits(regmap, LTC2945_CONTROL, CONTROL_TEST_MODE,
+				 CONTROL_TEST_MODE);
+
+	/* Reset minimum */
+	ret = regmap_bulk_write(regmap, reg, buf_min, num_regs);
+	if (ret)
+		return ret;
+
+	switch (reg) {
+	case LTC2945_MIN_POWER_H:
+		reg = LTC2945_MAX_POWER_H;
+		break;
+	case LTC2945_MIN_SENSE_H:
+		reg = LTC2945_MAX_SENSE_H;
+		break;
+	case LTC2945_MIN_VIN_H:
+		reg = LTC2945_MAX_VIN_H;
+		break;
+	case LTC2945_MIN_ADIN_H:
+		reg = LTC2945_MAX_ADIN_H;
+		break;
+	default:
+		WARN_ONCE(1, "Bad register: 0x%x\n", reg);
+		return -EINVAL;
+	}
+	/* Reset maximum */
+	ret = regmap_bulk_write(regmap, reg, buf_max, num_regs);
+
+	/* Try resetting test mode even if there was an error */
+	regmap_update_bits(regmap, LTC2945_CONTROL, CONTROL_TEST_MODE, 0);
+
+	return ret ? : count;
+}
+
+static ssize_t ltc2945_bool_show(struct device *dev,
+				 struct device_attribute *da, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	struct ltc2945_data *data = dev_get_drvdata(dev);
+	struct regmap *regmap = data->regmap;
+	unsigned int fault;
+	int ret;
+
+	ret = regmap_read(regmap, LTC2945_FAULT, &fault);
+	if (ret < 0)
+		return ret;
+
+	fault &= attr->index;
+	if (fault)		/* Clear reported faults in chip register */
+		regmap_update_bits(regmap, LTC2945_FAULT, attr->index, 0);
+
+	return sysfs_emit(buf, "%d\n", !!fault);
+}
+
+/* Input voltages */
+
+static SENSOR_DEVICE_ATTR_RO(in1_input, ltc2945_value, LTC2945_VIN_H);
+static SENSOR_DEVICE_ATTR_RW(in1_min, ltc2945_value, LTC2945_MIN_VIN_THRES_H);
+static SENSOR_DEVICE_ATTR_RW(in1_max, ltc2945_value, LTC2945_MAX_VIN_THRES_H);
+static SENSOR_DEVICE_ATTR_RO(in1_lowest, ltc2945_value, LTC2945_MIN_VIN_H);
+static SENSOR_DEVICE_ATTR_RO(in1_highest, ltc2945_value, LTC2945_MAX_VIN_H);
+static SENSOR_DEVICE_ATTR_WO(in1_reset_history, ltc2945_history,
+			     LTC2945_MIN_VIN_H);
+
+static SENSOR_DEVICE_ATTR_RO(in2_input, ltc2945_value, LTC2945_ADIN_H);
+static SENSOR_DEVICE_ATTR_RW(in2_min, ltc2945_value, LTC2945_MIN_ADIN_THRES_H);
+static SENSOR_DEVICE_ATTR_RW(in2_max, ltc2945_value, LTC2945_MAX_ADIN_THRES_H);
+static SENSOR_DEVICE_ATTR_RO(in2_lowest, ltc2945_value, LTC2945_MIN_ADIN_H);
+static SENSOR_DEVICE_ATTR_RO(in2_highest, ltc2945_value, LTC2945_MAX_ADIN_H);
+static SENSOR_DEVICE_ATTR_WO(in2_reset_history, ltc2945_history,
+			     LTC2945_MIN_ADIN_H);
+
+/* Voltage alarms */
+
+static SENSOR_DEVICE_ATTR_RO(in1_min_alarm, ltc2945_bool, FAULT_VIN_UV);
+static SENSOR_DEVICE_ATTR_RO(in1_max_alarm, ltc2945_bool, FAULT_VIN_OV);
+static SENSOR_DEVICE_ATTR_RO(in2_min_alarm, ltc2945_bool, FAULT_ADIN_UV);
+static SENSOR_DEVICE_ATTR_RO(in2_max_alarm, ltc2945_bool, FAULT_ADIN_OV);
+
+/* Currents (via sense resistor) */
+
+static SENSOR_DEVICE_ATTR_RO(curr1_input, ltc2945_value, LTC2945_SENSE_H);
+static SENSOR_DEVICE_ATTR_RW(curr1_min, ltc2945_value,
+			     LTC2945_MIN_SENSE_THRES_H);
+static SENSOR_DEVICE_ATTR_RW(curr1_max, ltc2945_value,
+			     LTC2945_MAX_SENSE_THRES_H);
+static SENSOR_DEVICE_ATTR_RO(curr1_lowest, ltc2945_value, LTC2945_MIN_SENSE_H);
+static SENSOR_DEVICE_ATTR_RO(curr1_highest, ltc2945_value,
+			     LTC2945_MAX_SENSE_H);
+static SENSOR_DEVICE_ATTR_WO(curr1_reset_history, ltc2945_history,
+			     LTC2945_MIN_SENSE_H);
+
+/* Current alarms */
+
+static SENSOR_DEVICE_ATTR_RO(curr1_min_alarm, ltc2945_bool, FAULT_SENSE_UV);
+static SENSOR_DEVICE_ATTR_RO(curr1_max_alarm, ltc2945_bool, FAULT_SENSE_OV);
+
+/* Power */
+
+static SENSOR_DEVICE_ATTR_RO(power1_input, ltc2945_value, LTC2945_POWER_H);
+static SENSOR_DEVICE_ATTR_RW(power1_min, ltc2945_value,
+			     LTC2945_MIN_POWER_THRES_H);
+static SENSOR_DEVICE_ATTR_RW(power1_max, ltc2945_value,
+			     LTC2945_MAX_POWER_THRES_H);
+static SENSOR_DEVICE_ATTR_RO(power1_input_lowest, ltc2945_value,
+			     LTC2945_MIN_POWER_H);
+static SENSOR_DEVICE_ATTR_RO(power1_input_highest, ltc2945_value,
+			     LTC2945_MAX_POWER_H);
+static SENSOR_DEVICE_ATTR_WO(power1_reset_history, ltc2945_history,
+			     LTC2945_MIN_POWER_H);
+
+/* Power alarms */
+
+static SENSOR_DEVICE_ATTR_RO(power1_min_alarm, ltc2945_bool, FAULT_POWER_UV);
+static SENSOR_DEVICE_ATTR_RO(power1_max_alarm, ltc2945_bool, FAULT_POWER_OV);
+
+static struct attribute *ltc2945_attrs[] = {
+	&sensor_dev_attr_in1_input.dev_attr.attr,
+	&sensor_dev_attr_in1_min.dev_attr.attr,
+	&sensor_dev_attr_in1_max.dev_attr.attr,
+	&sensor_dev_attr_in1_lowest.dev_attr.attr,
+	&sensor_dev_attr_in1_highest.dev_attr.attr,
+	&sensor_dev_attr_in1_reset_history.dev_attr.attr,
+	&sensor_dev_attr_in1_min_alarm.dev_attr.attr,
+	&sensor_dev_attr_in1_max_alarm.dev_attr.attr,
+
+	&sensor_dev_attr_in2_input.dev_attr.attr,
+	&sensor_dev_attr_in2_min.dev_attr.attr,
+	&sensor_dev_attr_in2_max.dev_attr.attr,
+	&sensor_dev_attr_in2_lowest.dev_attr.attr,
+	&sensor_dev_attr_in2_highest.dev_attr.attr,
+	&sensor_dev_attr_in2_reset_history.dev_attr.attr,
+	&sensor_dev_attr_in2_min_alarm.dev_attr.attr,
+	&sensor_dev_attr_in2_max_alarm.dev_attr.attr,
+
+	&sensor_dev_attr_curr1_input.dev_attr.attr,
+	&sensor_dev_attr_curr1_min.dev_attr.attr,
+	&sensor_dev_attr_curr1_max.dev_attr.attr,
+	&sensor_dev_attr_curr1_lowest.dev_attr.attr,
+	&sensor_dev_attr_curr1_highest.dev_attr.attr,
+	&sensor_dev_attr_curr1_reset_history.dev_attr.attr,
+	&sensor_dev_attr_curr1_min_alarm.dev_attr.attr,
+	&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
+
+	&sensor_dev_attr_power1_input.dev_attr.attr,
+	&sensor_dev_attr_power1_min.dev_attr.attr,
+	&sensor_dev_attr_power1_max.dev_attr.attr,
+	&sensor_dev_attr_power1_input_lowest.dev_attr.attr,
+	&sensor_dev_attr_power1_input_highest.dev_attr.attr,
+	&sensor_dev_attr_power1_reset_history.dev_attr.attr,
+	&sensor_dev_attr_power1_min_alarm.dev_attr.attr,
+	&sensor_dev_attr_power1_max_alarm.dev_attr.attr,
+
+	NULL,
+};
+ATTRIBUTE_GROUPS(ltc2945);
+
+static const struct regmap_config ltc2945_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = LTC2945_MIN_ADIN_THRES_L,
+};
+
+static int ltc2945_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct device *hwmon_dev;
+	struct regmap *regmap;
+	struct ltc2945_data *data;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+	dev_set_drvdata(dev, data);
+
+	regmap = devm_regmap_init_i2c(client, &ltc2945_regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(dev, "failed to allocate register map\n");
+		return PTR_ERR(regmap);
+	}
+
+	data->regmap = regmap;
+	if (device_property_read_u32(dev, "shunt-resistor-micro-ohms",
+				     &data->shunt_resistor))
+		data->shunt_resistor = 1000;
+
+	if (data->shunt_resistor == 0)
+		return -EINVAL;
+
+	/* Clear faults */
+	regmap_write(regmap, LTC2945_FAULT, 0x00);
+
+	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
+							   data,
+							   ltc2945_groups);
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id ltc2945_id[] = {
+	{ .name = "ltc2945" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(i2c, ltc2945_id);
+
+static struct i2c_driver ltc2945_driver = {
+	.driver = {
+		.name = "ltc2945",
+		.of_match_table = of_match_ptr(ltc2945_of_match),
+	},
+	.probe = ltc2945_probe,
+	.id_table = ltc2945_id,
+};
+
+module_i2c_driver(ltc2945_driver);
+
+MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
+MODULE_DESCRIPTION("LTC2945 driver");
+MODULE_LICENSE("GPL");