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, 670 insertions, 0 deletions

diff --git a/drivers/hwmon/emc2103.c b/drivers/hwmon/emc2103.c
new file mode 100644
index 000000000..27dc149a3
--- /dev/null
+++ b/drivers/hwmon/emc2103.c
@@ -0,0 +1,670 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * emc2103.c - Support for SMSC EMC2103
+ * Copyright (c) 2010 SMSC
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/jiffies.h>
+#include <linux/i2c.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+
+/* Addresses scanned */
+static const unsigned short normal_i2c[] = { 0x2E, I2C_CLIENT_END };
+
+static const u8 REG_TEMP[4] = { 0x00, 0x02, 0x04, 0x06 };
+static const u8 REG_TEMP_MIN[4] = { 0x3c, 0x38, 0x39, 0x3a };
+static const u8 REG_TEMP_MAX[4] = { 0x34, 0x30, 0x31, 0x32 };
+
+#define REG_CONF1		0x20
+#define REG_TEMP_MAX_ALARM	0x24
+#define REG_TEMP_MIN_ALARM	0x25
+#define REG_FAN_CONF1		0x42
+#define REG_FAN_TARGET_LO	0x4c
+#define REG_FAN_TARGET_HI	0x4d
+#define REG_FAN_TACH_HI		0x4e
+#define REG_FAN_TACH_LO		0x4f
+#define REG_PRODUCT_ID		0xfd
+#define REG_MFG_ID		0xfe
+
+/* equation 4 from datasheet: rpm = (3932160 * multipler) / count */
+#define FAN_RPM_FACTOR		3932160
+
+/*
+ * 2103-2 and 2103-4's 3rd temperature sensor can be connected to two diodes
+ * in anti-parallel mode, and in this configuration both can be read
+ * independently (so we have 4 temperature inputs).  The device can't
+ * detect if it's connected in this mode, so we have to manually enable
+ * it.  Default is to leave the device in the state it's already in (-1).
+ * This parameter allows APD mode to be optionally forced on or off
+ */
+static int apd = -1;
+module_param(apd, bint, 0);
+MODULE_PARM_DESC(apd, "Set to zero to disable anti-parallel diode mode");
+
+struct temperature {
+	s8	degrees;
+	u8	fraction;	/* 0-7 multiples of 0.125 */
+};
+
+struct emc2103_data {
+	struct i2c_client	*client;
+	const struct		attribute_group *groups[4];
+	struct mutex		update_lock;
+	bool			valid;		/* registers are valid */
+	bool			fan_rpm_control;
+	int			temp_count;	/* num of temp sensors */
+	unsigned long		last_updated;	/* in jiffies */
+	struct temperature	temp[4];	/* internal + 3 external */
+	s8			temp_min[4];	/* no fractional part */
+	s8			temp_max[4];    /* no fractional part */
+	u8			temp_min_alarm;
+	u8			temp_max_alarm;
+	u8			fan_multiplier;
+	u16			fan_tach;
+	u16			fan_target;
+};
+
+static int read_u8_from_i2c(struct i2c_client *client, u8 i2c_reg, u8 *output)
+{
+	int status = i2c_smbus_read_byte_data(client, i2c_reg);
+	if (status < 0) {
+		dev_warn(&client->dev, "reg 0x%02x, err %d\n",
+			i2c_reg, status);
+	} else {
+		*output = status;
+	}
+	return status;
+}
+
+static void read_temp_from_i2c(struct i2c_client *client, u8 i2c_reg,
+			       struct temperature *temp)
+{
+	u8 degrees, fractional;
+
+	if (read_u8_from_i2c(client, i2c_reg, &degrees) < 0)
+		return;
+
+	if (read_u8_from_i2c(client, i2c_reg + 1, &fractional) < 0)
+		return;
+
+	temp->degrees = degrees;
+	temp->fraction = (fractional & 0xe0) >> 5;
+}
+
+static void read_fan_from_i2c(struct i2c_client *client, u16 *output,
+			      u8 hi_addr, u8 lo_addr)
+{
+	u8 high_byte, lo_byte;
+
+	if (read_u8_from_i2c(client, hi_addr, &high_byte) < 0)
+		return;
+
+	if (read_u8_from_i2c(client, lo_addr, &lo_byte) < 0)
+		return;
+
+	*output = ((u16)high_byte << 5) | (lo_byte >> 3);
+}
+
+static void write_fan_target_to_i2c(struct i2c_client *client, u16 new_target)
+{
+	u8 high_byte = (new_target & 0x1fe0) >> 5;
+	u8 low_byte = (new_target & 0x001f) << 3;
+	i2c_smbus_write_byte_data(client, REG_FAN_TARGET_LO, low_byte);
+	i2c_smbus_write_byte_data(client, REG_FAN_TARGET_HI, high_byte);
+}
+
+static void read_fan_config_from_i2c(struct i2c_client *client)
+
+{
+	struct emc2103_data *data = i2c_get_clientdata(client);
+	u8 conf1;
+
+	if (read_u8_from_i2c(client, REG_FAN_CONF1, &conf1) < 0)
+		return;
+
+	data->fan_multiplier = 1 << ((conf1 & 0x60) >> 5);
+	data->fan_rpm_control = (conf1 & 0x80) != 0;
+}
+
+static struct emc2103_data *emc2103_update_device(struct device *dev)
+{
+	struct emc2103_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+
+	mutex_lock(&data->update_lock);
+
+	if (time_after(jiffies, data->last_updated + HZ + HZ / 2)
+	    || !data->valid) {
+		int i;
+
+		for (i = 0; i < data->temp_count; i++) {
+			read_temp_from_i2c(client, REG_TEMP[i], &data->temp[i]);
+			read_u8_from_i2c(client, REG_TEMP_MIN[i],
+				&data->temp_min[i]);
+			read_u8_from_i2c(client, REG_TEMP_MAX[i],
+				&data->temp_max[i]);
+		}
+
+		read_u8_from_i2c(client, REG_TEMP_MIN_ALARM,
+			&data->temp_min_alarm);
+		read_u8_from_i2c(client, REG_TEMP_MAX_ALARM,
+			&data->temp_max_alarm);
+
+		read_fan_from_i2c(client, &data->fan_tach,
+			REG_FAN_TACH_HI, REG_FAN_TACH_LO);
+		read_fan_from_i2c(client, &data->fan_target,
+			REG_FAN_TARGET_HI, REG_FAN_TARGET_LO);
+		read_fan_config_from_i2c(client);
+
+		data->last_updated = jiffies;
+		data->valid = true;
+	}
+
+	mutex_unlock(&data->update_lock);
+
+	return data;
+}
+
+static ssize_t
+temp_show(struct device *dev, struct device_attribute *da, char *buf)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct emc2103_data *data = emc2103_update_device(dev);
+	int millidegrees = data->temp[nr].degrees * 1000
+		+ data->temp[nr].fraction * 125;
+	return sprintf(buf, "%d\n", millidegrees);
+}
+
+static ssize_t
+temp_min_show(struct device *dev, struct device_attribute *da, char *buf)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct emc2103_data *data = emc2103_update_device(dev);
+	int millidegrees = data->temp_min[nr] * 1000;
+	return sprintf(buf, "%d\n", millidegrees);
+}
+
+static ssize_t
+temp_max_show(struct device *dev, struct device_attribute *da, char *buf)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct emc2103_data *data = emc2103_update_device(dev);
+	int millidegrees = data->temp_max[nr] * 1000;
+	return sprintf(buf, "%d\n", millidegrees);
+}
+
+static ssize_t
+temp_fault_show(struct device *dev, struct device_attribute *da, char *buf)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct emc2103_data *data = emc2103_update_device(dev);
+	bool fault = (data->temp[nr].degrees == -128);
+	return sprintf(buf, "%d\n", fault ? 1 : 0);
+}
+
+static ssize_t
+temp_min_alarm_show(struct device *dev, struct device_attribute *da,
+		    char *buf)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct emc2103_data *data = emc2103_update_device(dev);
+	bool alarm = data->temp_min_alarm & (1 << nr);
+	return sprintf(buf, "%d\n", alarm ? 1 : 0);
+}
+
+static ssize_t
+temp_max_alarm_show(struct device *dev, struct device_attribute *da,
+		    char *buf)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct emc2103_data *data = emc2103_update_device(dev);
+	bool alarm = data->temp_max_alarm & (1 << nr);
+	return sprintf(buf, "%d\n", alarm ? 1 : 0);
+}
+
+static ssize_t temp_min_store(struct device *dev, struct device_attribute *da,
+			      const char *buf, size_t count)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct emc2103_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	long val;
+
+	int result = kstrtol(buf, 10, &val);
+	if (result < 0)
+		return result;
+
+	val = DIV_ROUND_CLOSEST(clamp_val(val, -63000, 127000), 1000);
+
+	mutex_lock(&data->update_lock);
+	data->temp_min[nr] = val;
+	i2c_smbus_write_byte_data(client, REG_TEMP_MIN[nr], val);
+	mutex_unlock(&data->update_lock);
+
+	return count;
+}
+
+static ssize_t temp_max_store(struct device *dev, struct device_attribute *da,
+			      const char *buf, size_t count)
+{
+	int nr = to_sensor_dev_attr(da)->index;
+	struct emc2103_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	long val;
+
+	int result = kstrtol(buf, 10, &val);
+	if (result < 0)
+		return result;
+
+	val = DIV_ROUND_CLOSEST(clamp_val(val, -63000, 127000), 1000);
+
+	mutex_lock(&data->update_lock);
+	data->temp_max[nr] = val;
+	i2c_smbus_write_byte_data(client, REG_TEMP_MAX[nr], val);
+	mutex_unlock(&data->update_lock);
+
+	return count;
+}
+
+static ssize_t
+fan1_input_show(struct device *dev, struct device_attribute *da, char *buf)
+{
+	struct emc2103_data *data = emc2103_update_device(dev);
+	int rpm = 0;
+	mutex_lock(&data->update_lock);
+	if (data->fan_tach != 0)
+		rpm = (FAN_RPM_FACTOR * data->fan_multiplier) / data->fan_tach;
+	mutex_unlock(&data->update_lock);
+	return sprintf(buf, "%d\n", rpm);
+}
+
+static ssize_t
+fan1_div_show(struct device *dev, struct device_attribute *da, char *buf)
+{
+	struct emc2103_data *data = emc2103_update_device(dev);
+	int fan_div = 8 / data->fan_multiplier;
+	return sprintf(buf, "%d\n", fan_div);
+}
+
+/*
+ * Note: we also update the fan target here, because its value is
+ * determined in part by the fan clock divider.  This follows the principle
+ * of least surprise; the user doesn't expect the fan target to change just
+ * because the divider changed.
+ */
+static ssize_t fan1_div_store(struct device *dev, struct device_attribute *da,
+			      const char *buf, size_t count)
+{
+	struct emc2103_data *data = emc2103_update_device(dev);
+	struct i2c_client *client = data->client;
+	int new_range_bits, old_div = 8 / data->fan_multiplier;
+	long new_div;
+
+	int status = kstrtol(buf, 10, &new_div);
+	if (status < 0)
+		return status;
+
+	if (new_div == old_div) /* No change */
+		return count;
+
+	switch (new_div) {
+	case 1:
+		new_range_bits = 3;
+		break;
+	case 2:
+		new_range_bits = 2;
+		break;
+	case 4:
+		new_range_bits = 1;
+		break;
+	case 8:
+		new_range_bits = 0;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	mutex_lock(&data->update_lock);
+
+	status = i2c_smbus_read_byte_data(client, REG_FAN_CONF1);
+	if (status < 0) {
+		dev_dbg(&client->dev, "reg 0x%02x, err %d\n",
+			REG_FAN_CONF1, status);
+		mutex_unlock(&data->update_lock);
+		return status;
+	}
+	status &= 0x9F;
+	status |= (new_range_bits << 5);
+	i2c_smbus_write_byte_data(client, REG_FAN_CONF1, status);
+
+	data->fan_multiplier = 8 / new_div;
+
+	/* update fan target if high byte is not disabled */
+	if ((data->fan_target & 0x1fe0) != 0x1fe0) {
+		u16 new_target = (data->fan_target * old_div) / new_div;
+		data->fan_target = min(new_target, (u16)0x1fff);
+		write_fan_target_to_i2c(client, data->fan_target);
+	}
+
+	/* invalidate data to force re-read from hardware */
+	data->valid = false;
+
+	mutex_unlock(&data->update_lock);
+	return count;
+}
+
+static ssize_t
+fan1_target_show(struct device *dev, struct device_attribute *da, char *buf)
+{
+	struct emc2103_data *data = emc2103_update_device(dev);
+	int rpm = 0;
+
+	mutex_lock(&data->update_lock);
+	/* high byte of 0xff indicates disabled so return 0 */
+	if ((data->fan_target != 0) && ((data->fan_target & 0x1fe0) != 0x1fe0))
+		rpm = (FAN_RPM_FACTOR * data->fan_multiplier)
+			/ data->fan_target;
+	mutex_unlock(&data->update_lock);
+
+	return sprintf(buf, "%d\n", rpm);
+}
+
+static ssize_t fan1_target_store(struct device *dev,
+				 struct device_attribute *da, const char *buf,
+				 size_t count)
+{
+	struct emc2103_data *data = emc2103_update_device(dev);
+	struct i2c_client *client = data->client;
+	unsigned long rpm_target;
+
+	int result = kstrtoul(buf, 10, &rpm_target);
+	if (result < 0)
+		return result;
+
+	/* Datasheet states 16384 as maximum RPM target (table 3.2) */
+	rpm_target = clamp_val(rpm_target, 0, 16384);
+
+	mutex_lock(&data->update_lock);
+
+	if (rpm_target == 0)
+		data->fan_target = 0x1fff;
+	else
+		data->fan_target = clamp_val(
+			(FAN_RPM_FACTOR * data->fan_multiplier) / rpm_target,
+			0, 0x1fff);
+
+	write_fan_target_to_i2c(client, data->fan_target);
+
+	mutex_unlock(&data->update_lock);
+	return count;
+}
+
+static ssize_t
+fan1_fault_show(struct device *dev, struct device_attribute *da, char *buf)
+{
+	struct emc2103_data *data = emc2103_update_device(dev);
+	bool fault = ((data->fan_tach & 0x1fe0) == 0x1fe0);
+	return sprintf(buf, "%d\n", fault ? 1 : 0);
+}
+
+static ssize_t
+pwm1_enable_show(struct device *dev, struct device_attribute *da, char *buf)
+{
+	struct emc2103_data *data = emc2103_update_device(dev);
+	return sprintf(buf, "%d\n", data->fan_rpm_control ? 3 : 0);
+}
+
+static ssize_t pwm1_enable_store(struct device *dev,
+				 struct device_attribute *da, const char *buf,
+				 size_t count)
+{
+	struct emc2103_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	long new_value;
+	u8 conf_reg;
+
+	int result = kstrtol(buf, 10, &new_value);
+	if (result < 0)
+		return result;
+
+	mutex_lock(&data->update_lock);
+	switch (new_value) {
+	case 0:
+		data->fan_rpm_control = false;
+		break;
+	case 3:
+		data->fan_rpm_control = true;
+		break;
+	default:
+		count = -EINVAL;
+		goto err;
+	}
+
+	result = read_u8_from_i2c(client, REG_FAN_CONF1, &conf_reg);
+	if (result < 0) {
+		count = result;
+		goto err;
+	}
+
+	if (data->fan_rpm_control)
+		conf_reg |= 0x80;
+	else
+		conf_reg &= ~0x80;
+
+	i2c_smbus_write_byte_data(client, REG_FAN_CONF1, conf_reg);
+err:
+	mutex_unlock(&data->update_lock);
+	return count;
+}
+
+static SENSOR_DEVICE_ATTR_RO(temp1_input, temp, 0);
+static SENSOR_DEVICE_ATTR_RW(temp1_min, temp_min, 0);
+static SENSOR_DEVICE_ATTR_RW(temp1_max, temp_max, 0);
+static SENSOR_DEVICE_ATTR_RO(temp1_fault, temp_fault, 0);
+static SENSOR_DEVICE_ATTR_RO(temp1_min_alarm, temp_min_alarm, 0);
+static SENSOR_DEVICE_ATTR_RO(temp1_max_alarm, temp_max_alarm, 0);
+
+static SENSOR_DEVICE_ATTR_RO(temp2_input, temp, 1);
+static SENSOR_DEVICE_ATTR_RW(temp2_min, temp_min, 1);
+static SENSOR_DEVICE_ATTR_RW(temp2_max, temp_max, 1);
+static SENSOR_DEVICE_ATTR_RO(temp2_fault, temp_fault, 1);
+static SENSOR_DEVICE_ATTR_RO(temp2_min_alarm, temp_min_alarm, 1);
+static SENSOR_DEVICE_ATTR_RO(temp2_max_alarm, temp_max_alarm, 1);
+
+static SENSOR_DEVICE_ATTR_RO(temp3_input, temp, 2);
+static SENSOR_DEVICE_ATTR_RW(temp3_min, temp_min, 2);
+static SENSOR_DEVICE_ATTR_RW(temp3_max, temp_max, 2);
+static SENSOR_DEVICE_ATTR_RO(temp3_fault, temp_fault, 2);
+static SENSOR_DEVICE_ATTR_RO(temp3_min_alarm, temp_min_alarm, 2);
+static SENSOR_DEVICE_ATTR_RO(temp3_max_alarm, temp_max_alarm, 2);
+
+static SENSOR_DEVICE_ATTR_RO(temp4_input, temp, 3);
+static SENSOR_DEVICE_ATTR_RW(temp4_min, temp_min, 3);
+static SENSOR_DEVICE_ATTR_RW(temp4_max, temp_max, 3);
+static SENSOR_DEVICE_ATTR_RO(temp4_fault, temp_fault, 3);
+static SENSOR_DEVICE_ATTR_RO(temp4_min_alarm, temp_min_alarm, 3);
+static SENSOR_DEVICE_ATTR_RO(temp4_max_alarm, temp_max_alarm, 3);
+
+static DEVICE_ATTR_RO(fan1_input);
+static DEVICE_ATTR_RW(fan1_div);
+static DEVICE_ATTR_RW(fan1_target);
+static DEVICE_ATTR_RO(fan1_fault);
+
+static DEVICE_ATTR_RW(pwm1_enable);
+
+/* sensors present on all models */
+static struct attribute *emc2103_attributes[] = {
+	&sensor_dev_attr_temp1_input.dev_attr.attr,
+	&sensor_dev_attr_temp1_min.dev_attr.attr,
+	&sensor_dev_attr_temp1_max.dev_attr.attr,
+	&sensor_dev_attr_temp1_fault.dev_attr.attr,
+	&sensor_dev_attr_temp1_min_alarm.dev_attr.attr,
+	&sensor_dev_attr_temp1_max_alarm.dev_attr.attr,
+	&sensor_dev_attr_temp2_input.dev_attr.attr,
+	&sensor_dev_attr_temp2_min.dev_attr.attr,
+	&sensor_dev_attr_temp2_max.dev_attr.attr,
+	&sensor_dev_attr_temp2_fault.dev_attr.attr,
+	&sensor_dev_attr_temp2_min_alarm.dev_attr.attr,
+	&sensor_dev_attr_temp2_max_alarm.dev_attr.attr,
+	&dev_attr_fan1_input.attr,
+	&dev_attr_fan1_div.attr,
+	&dev_attr_fan1_target.attr,
+	&dev_attr_fan1_fault.attr,
+	&dev_attr_pwm1_enable.attr,
+	NULL
+};
+
+/* extra temperature sensors only present on 2103-2 and 2103-4 */
+static struct attribute *emc2103_attributes_temp3[] = {
+	&sensor_dev_attr_temp3_input.dev_attr.attr,
+	&sensor_dev_attr_temp3_min.dev_attr.attr,
+	&sensor_dev_attr_temp3_max.dev_attr.attr,
+	&sensor_dev_attr_temp3_fault.dev_attr.attr,
+	&sensor_dev_attr_temp3_min_alarm.dev_attr.attr,
+	&sensor_dev_attr_temp3_max_alarm.dev_attr.attr,
+	NULL
+};
+
+/* extra temperature sensors only present on 2103-2 and 2103-4 in APD mode */
+static struct attribute *emc2103_attributes_temp4[] = {
+	&sensor_dev_attr_temp4_input.dev_attr.attr,
+	&sensor_dev_attr_temp4_min.dev_attr.attr,
+	&sensor_dev_attr_temp4_max.dev_attr.attr,
+	&sensor_dev_attr_temp4_fault.dev_attr.attr,
+	&sensor_dev_attr_temp4_min_alarm.dev_attr.attr,
+	&sensor_dev_attr_temp4_max_alarm.dev_attr.attr,
+	NULL
+};
+
+static const struct attribute_group emc2103_group = {
+	.attrs = emc2103_attributes,
+};
+
+static const struct attribute_group emc2103_temp3_group = {
+	.attrs = emc2103_attributes_temp3,
+};
+
+static const struct attribute_group emc2103_temp4_group = {
+	.attrs = emc2103_attributes_temp4,
+};
+
+static int
+emc2103_probe(struct i2c_client *client)
+{
+	struct emc2103_data *data;
+	struct device *hwmon_dev;
+	int status, idx = 0;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -EIO;
+
+	data = devm_kzalloc(&client->dev, sizeof(struct emc2103_data),
+			    GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, data);
+	data->client = client;
+	mutex_init(&data->update_lock);
+
+	/* 2103-2 and 2103-4 have 3 external diodes, 2103-1 has 1 */
+	status = i2c_smbus_read_byte_data(client, REG_PRODUCT_ID);
+	if (status == 0x24) {
+		/* 2103-1 only has 1 external diode */
+		data->temp_count = 2;
+	} else {
+		/* 2103-2 and 2103-4 have 3 or 4 external diodes */
+		status = i2c_smbus_read_byte_data(client, REG_CONF1);
+		if (status < 0) {
+			dev_dbg(&client->dev, "reg 0x%02x, err %d\n", REG_CONF1,
+				status);
+			return status;
+		}
+
+		/* detect current state of hardware */
+		data->temp_count = (status & 0x01) ? 4 : 3;
+
+		/* force APD state if module parameter is set */
+		if (apd == 0) {
+			/* force APD mode off */
+			data->temp_count = 3;
+			status &= ~(0x01);
+			i2c_smbus_write_byte_data(client, REG_CONF1, status);
+		} else if (apd == 1) {
+			/* force APD mode on */
+			data->temp_count = 4;
+			status |= 0x01;
+			i2c_smbus_write_byte_data(client, REG_CONF1, status);
+		}
+	}
+
+	/* sysfs hooks */
+	data->groups[idx++] = &emc2103_group;
+	if (data->temp_count >= 3)
+		data->groups[idx++] = &emc2103_temp3_group;
+	if (data->temp_count == 4)
+		data->groups[idx++] = &emc2103_temp4_group;
+
+	hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev,
+							   client->name, data,
+							   data->groups);
+	if (IS_ERR(hwmon_dev))
+		return PTR_ERR(hwmon_dev);
+
+	dev_info(&client->dev, "%s: sensor '%s'\n",
+		 dev_name(hwmon_dev), client->name);
+
+	return 0;
+}
+
+static const struct i2c_device_id emc2103_ids[] = {
+	{ .name = "emc2103" },
+	{ /* LIST END */ }
+};
+MODULE_DEVICE_TABLE(i2c, emc2103_ids);
+
+/* Return 0 if detection is successful, -ENODEV otherwise */
+static int
+emc2103_detect(struct i2c_client *new_client, struct i2c_board_info *info)
+{
+	struct i2c_adapter *adapter = new_client->adapter;
+	int manufacturer, product;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -ENODEV;
+
+	manufacturer = i2c_smbus_read_byte_data(new_client, REG_MFG_ID);
+	if (manufacturer != 0x5D)
+		return -ENODEV;
+
+	product = i2c_smbus_read_byte_data(new_client, REG_PRODUCT_ID);
+	if ((product != 0x24) && (product != 0x26))
+		return -ENODEV;
+
+	strscpy(info->type, "emc2103", I2C_NAME_SIZE);
+
+	return 0;
+}
+
+static struct i2c_driver emc2103_driver = {
+	.class		= I2C_CLASS_HWMON,
+	.driver = {
+		.name	= "emc2103",
+	},
+	.probe		= emc2103_probe,
+	.id_table	= emc2103_ids,
+	.detect		= emc2103_detect,
+	.address_list	= normal_i2c,
+};
+
+module_i2c_driver(emc2103_driver);
+
+MODULE_AUTHOR("Steve Glendinning <steve.glendinning@shawell.net>");
+MODULE_DESCRIPTION("SMSC EMC2103 hwmon driver");
+MODULE_LICENSE("GPL");