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, 421 insertions, 0 deletions

diff --git a/drivers/video/backlight/mp3309c.c b/drivers/video/backlight/mp3309c.c
new file mode 100644
index 000000000..752a45798
--- /dev/null
+++ b/drivers/video/backlight/mp3309c.c
@@ -0,0 +1,421 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for MPS MP3309C White LED driver with I2C interface
+ *
+ * This driver support both analog (by I2C commands) and PWM dimming control
+ * modes.
+ *
+ * Copyright (C) 2023 ASEM Srl
+ * Author: Flavio Suligoi <f.suligoi@asem.it>
+ *
+ * Based on pwm_bl.c
+ */
+
+#include <linux/backlight.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/property.h>
+#include <linux/pwm.h>
+#include <linux/regmap.h>
+
+#define REG_I2C_0	0x00
+#define REG_I2C_1	0x01
+
+#define REG_I2C_0_EN	0x80
+#define REG_I2C_0_D0	0x40
+#define REG_I2C_0_D1	0x20
+#define REG_I2C_0_D2	0x10
+#define REG_I2C_0_D3	0x08
+#define REG_I2C_0_D4	0x04
+#define REG_I2C_0_RSRV1	0x02
+#define REG_I2C_0_RSRV2	0x01
+
+#define REG_I2C_1_RSRV1	0x80
+#define REG_I2C_1_DIMS	0x40
+#define REG_I2C_1_SYNC	0x20
+#define REG_I2C_1_OVP0	0x10
+#define REG_I2C_1_OVP1	0x08
+#define REG_I2C_1_VOS	0x04
+#define REG_I2C_1_LEDO	0x02
+#define REG_I2C_1_OTP	0x01
+
+#define ANALOG_I2C_NUM_LEVELS	32		/* 0..31 */
+#define ANALOG_I2C_REG_MASK	0x7c
+
+#define MP3309C_PWM_DEFAULT_NUM_LEVELS	256	/* 0..255 */
+
+enum mp3309c_status_value {
+	FIRST_POWER_ON,
+	BACKLIGHT_OFF,
+	BACKLIGHT_ON,
+};
+
+enum mp3309c_dimming_mode_value {
+	DIMMING_PWM,
+	DIMMING_ANALOG_I2C,
+};
+
+struct mp3309c_platform_data {
+	unsigned int max_brightness;
+	unsigned int default_brightness;
+	unsigned int *levels;
+	u8  dimming_mode;
+	u8  over_voltage_protection;
+	bool sync_mode;
+	u8 status;
+};
+
+struct mp3309c_chip {
+	struct device *dev;
+	struct mp3309c_platform_data *pdata;
+	struct backlight_device *bl;
+	struct gpio_desc *enable_gpio;
+	struct regmap *regmap;
+	struct pwm_device *pwmd;
+};
+
+static const struct regmap_config mp3309c_regmap = {
+	.name = "mp3309c_regmap",
+	.reg_bits = 8,
+	.reg_stride = 1,
+	.val_bits = 8,
+	.max_register = REG_I2C_1,
+};
+
+static int mp3309c_enable_device(struct mp3309c_chip *chip)
+{
+	u8 reg_val;
+	int ret;
+
+	/* I2C register #0 - Device enable */
+	ret = regmap_update_bits(chip->regmap, REG_I2C_0, REG_I2C_0_EN,
+				 REG_I2C_0_EN);
+	if (ret)
+		return ret;
+
+	/*
+	 * I2C register #1 - Set working mode:
+	 *  - enable/disable synchronous mode
+	 *  - set overvoltage protection (OVP)
+	 */
+	reg_val = 0x00;
+	if (chip->pdata->sync_mode)
+		reg_val |= REG_I2C_1_SYNC;
+	reg_val |= chip->pdata->over_voltage_protection;
+	ret = regmap_write(chip->regmap, REG_I2C_1, reg_val);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int mp3309c_bl_update_status(struct backlight_device *bl)
+{
+	struct mp3309c_chip *chip = bl_get_data(bl);
+	int brightness = backlight_get_brightness(bl);
+	struct pwm_state pwmstate;
+	unsigned int analog_val, bits_val;
+	int i, ret;
+
+	if (chip->pdata->dimming_mode == DIMMING_PWM) {
+		/*
+		 * PWM control mode
+		 */
+		pwm_get_state(chip->pwmd, &pwmstate);
+		pwm_set_relative_duty_cycle(&pwmstate,
+					    chip->pdata->levels[brightness],
+					    chip->pdata->levels[chip->pdata->max_brightness]);
+		pwmstate.enabled = true;
+		ret = pwm_apply_might_sleep(chip->pwmd, &pwmstate);
+		if (ret)
+			return ret;
+
+		switch (chip->pdata->status) {
+		case FIRST_POWER_ON:
+		case BACKLIGHT_OFF:
+			/*
+			 * After 20ms of low pwm signal level, the chip turns
+			 * off automatically. In this case, before enabling the
+			 * chip again, we must wait about 10ms for pwm signal to
+			 * stabilize.
+			 */
+			if (brightness > 0) {
+				msleep(10);
+				mp3309c_enable_device(chip);
+				chip->pdata->status = BACKLIGHT_ON;
+			} else {
+				chip->pdata->status = BACKLIGHT_OFF;
+			}
+			break;
+		case BACKLIGHT_ON:
+			if (brightness == 0)
+				chip->pdata->status = BACKLIGHT_OFF;
+			break;
+		}
+	} else {
+		/*
+		 * Analog (by I2C command) control mode
+		 *
+		 * The first time, before setting brightness, we must enable the
+		 * device
+		 */
+		if (chip->pdata->status == FIRST_POWER_ON)
+			mp3309c_enable_device(chip);
+
+		/*
+		 * Dimming mode I2C command (fixed dimming range 0..31)
+		 *
+		 * The 5 bits of the dimming analog value D4..D0 is allocated
+		 * in the I2C register #0, in the following way:
+		 *
+		 *     +--+--+--+--+--+--+--+--+
+		 *     |EN|D0|D1|D2|D3|D4|XX|XX|
+		 *     +--+--+--+--+--+--+--+--+
+		 */
+		analog_val = brightness;
+		bits_val = 0;
+		for (i = 0; i <= 5; i++)
+			bits_val += ((analog_val >> i) & 0x01) << (6 - i);
+		ret = regmap_update_bits(chip->regmap, REG_I2C_0,
+					 ANALOG_I2C_REG_MASK, bits_val);
+		if (ret)
+			return ret;
+
+		if (brightness > 0)
+			chip->pdata->status = BACKLIGHT_ON;
+		else
+			chip->pdata->status = BACKLIGHT_OFF;
+	}
+
+	return 0;
+}
+
+static const struct backlight_ops mp3309c_bl_ops = {
+	.update_status = mp3309c_bl_update_status,
+};
+
+static int mp3309c_parse_fwnode(struct mp3309c_chip *chip,
+				struct mp3309c_platform_data *pdata)
+{
+	int ret, i;
+	unsigned int tmp_value;
+	struct device *dev = chip->dev;
+	int num_levels;
+
+	if (!dev_fwnode(dev))
+		return dev_err_probe(dev, -ENODEV, "failed to get firmware node\n");
+
+	/*
+	 * Dimming mode: the MP3309C provides two dimming control mode:
+	 *
+	 * - PWM mode
+	 * - Analog by I2C control mode (default)
+	 *
+	 * I2C control mode is assumed as default but, if the pwms property is
+	 * found in the backlight node, the mode switches to PWM mode.
+	 */
+	pdata->dimming_mode = DIMMING_ANALOG_I2C;
+	if (device_property_present(dev, "pwms")) {
+		chip->pwmd = devm_pwm_get(dev, NULL);
+		if (IS_ERR(chip->pwmd))
+			return dev_err_probe(dev, PTR_ERR(chip->pwmd), "error getting pwm data\n");
+		pdata->dimming_mode = DIMMING_PWM;
+	}
+
+	/*
+	 * In I2C control mode the dimming levels (0..31) are fixed by the
+	 * hardware, while in PWM control mode they can be chosen by the user,
+	 * to allow nonlinear mappings.
+	 */
+	if  (pdata->dimming_mode == DIMMING_ANALOG_I2C) {
+		/*
+		 * Analog (by I2C commands) control mode: fixed 0..31 brightness
+		 * levels
+		 */
+		num_levels = ANALOG_I2C_NUM_LEVELS;
+
+		/* Enable GPIO used in I2C dimming mode only */
+		chip->enable_gpio = devm_gpiod_get(dev, "enable", GPIOD_OUT_HIGH);
+		if (IS_ERR(chip->enable_gpio))
+			return dev_err_probe(dev, PTR_ERR(chip->enable_gpio),
+					     "error getting enable gpio\n");
+	} else {
+		/*
+		 * PWM control mode: check for brightness level in DT
+		 */
+		if (device_property_present(dev, "brightness-levels")) {
+			/* Read brightness levels from DT */
+			num_levels = device_property_count_u32(dev, "brightness-levels");
+			if (num_levels < 2)
+				return -EINVAL;
+		} else {
+			/* Use default brightness levels */
+			num_levels = MP3309C_PWM_DEFAULT_NUM_LEVELS;
+		}
+	}
+
+	/* Fill brightness levels array */
+	pdata->levels = devm_kcalloc(dev, num_levels, sizeof(*pdata->levels), GFP_KERNEL);
+	if (!pdata->levels)
+		return -ENOMEM;
+	if (device_property_present(dev, "brightness-levels")) {
+		ret = device_property_read_u32_array(dev, "brightness-levels",
+						     pdata->levels, num_levels);
+		if (ret < 0)
+			return ret;
+	} else {
+		for (i = 0; i < num_levels; i++)
+			pdata->levels[i] = i;
+	}
+
+	pdata->max_brightness = num_levels - 1;
+
+	ret = device_property_read_u32(dev, "default-brightness", &pdata->default_brightness);
+	if (ret)
+		pdata->default_brightness = pdata->max_brightness;
+	if (pdata->default_brightness > pdata->max_brightness) {
+		dev_err_probe(dev, -ERANGE, "default brightness exceeds max brightness\n");
+		pdata->default_brightness = pdata->max_brightness;
+	}
+
+	/*
+	 * Over-voltage protection (OVP)
+	 *
+	 * This (optional) property values are:
+	 *
+	 *  - 13.5V
+	 *  - 24V
+	 *  - 35.5V (hardware default setting)
+	 *
+	 * If missing, the default value for OVP is 35.5V
+	 */
+	pdata->over_voltage_protection = REG_I2C_1_OVP1;
+	ret = device_property_read_u32(dev, "mps,overvoltage-protection-microvolt", &tmp_value);
+	if (!ret) {
+		switch (tmp_value) {
+		case 13500000:
+			pdata->over_voltage_protection = 0x00;
+			break;
+		case 24000000:
+			pdata->over_voltage_protection = REG_I2C_1_OVP0;
+			break;
+		case 35500000:
+			pdata->over_voltage_protection = REG_I2C_1_OVP1;
+			break;
+		default:
+			return -EINVAL;
+		}
+	}
+
+	/* Synchronous (default) and non-synchronous mode */
+	pdata->sync_mode = !device_property_read_bool(dev, "mps,no-sync-mode");
+
+	return 0;
+}
+
+static int mp3309c_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct mp3309c_platform_data *pdata = dev_get_platdata(dev);
+	struct mp3309c_chip *chip;
+	struct backlight_properties props;
+	struct pwm_state pwmstate;
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return dev_err_probe(dev, -EOPNOTSUPP, "failed to check i2c functionality\n");
+
+	chip = devm_kzalloc(dev, sizeof(*chip), GFP_KERNEL);
+	if (!chip)
+		return -ENOMEM;
+
+	chip->dev = dev;
+
+	chip->regmap = devm_regmap_init_i2c(client, &mp3309c_regmap);
+	if (IS_ERR(chip->regmap))
+		return dev_err_probe(dev, PTR_ERR(chip->regmap),
+				     "failed to allocate register map\n");
+
+	i2c_set_clientdata(client, chip);
+
+	if (!pdata) {
+		pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
+		if (!pdata)
+			return -ENOMEM;
+
+		ret = mp3309c_parse_fwnode(chip, pdata);
+		if (ret)
+			return ret;
+	}
+	chip->pdata = pdata;
+
+	/* Backlight properties */
+	props = (typeof(props)){
+		.brightness = pdata->default_brightness,
+		.max_brightness = pdata->max_brightness,
+		.scale = BACKLIGHT_SCALE_LINEAR,
+		.type = BACKLIGHT_RAW,
+		.power = BACKLIGHT_POWER_ON,
+	};
+	chip->bl = devm_backlight_device_register(dev, "mp3309c", dev, chip,
+						  &mp3309c_bl_ops, &props);
+	if (IS_ERR(chip->bl))
+		return dev_err_probe(dev, PTR_ERR(chip->bl),
+				     "error registering backlight device\n");
+
+	/* In PWM dimming mode, enable pwm device */
+	if (chip->pdata->dimming_mode == DIMMING_PWM) {
+		pwm_init_state(chip->pwmd, &pwmstate);
+		pwm_set_relative_duty_cycle(&pwmstate,
+					    chip->pdata->default_brightness,
+					    chip->pdata->max_brightness);
+		pwmstate.enabled = true;
+		ret = pwm_apply_might_sleep(chip->pwmd, &pwmstate);
+		if (ret)
+			return dev_err_probe(dev, ret, "error setting pwm device\n");
+	}
+
+	chip->pdata->status = FIRST_POWER_ON;
+	backlight_update_status(chip->bl);
+
+	return 0;
+}
+
+static void mp3309c_remove(struct i2c_client *client)
+{
+	struct mp3309c_chip *chip = i2c_get_clientdata(client);
+	struct backlight_device *bl = chip->bl;
+
+	bl->props.power = BACKLIGHT_POWER_OFF;
+	bl->props.brightness = 0;
+	backlight_update_status(chip->bl);
+}
+
+static const struct of_device_id mp3309c_match_table[] = {
+	{ .compatible = "mps,mp3309c", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, mp3309c_match_table);
+
+static const struct i2c_device_id mp3309c_id[] = {
+	{ .name = "mp3309c" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, mp3309c_id);
+
+static struct i2c_driver mp3309c_i2c_driver = {
+	.driver	= {
+			.name		= KBUILD_MODNAME,
+			.of_match_table	= mp3309c_match_table,
+	},
+	.probe		= mp3309c_probe,
+	.remove		= mp3309c_remove,
+	.id_table	= mp3309c_id,
+};
+
+module_i2c_driver(mp3309c_i2c_driver);
+
+MODULE_DESCRIPTION("Backlight Driver for MPS MP3309C");
+MODULE_AUTHOR("Flavio Suligoi <f.suligoi@asem.it>");
+MODULE_LICENSE("GPL");