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, 341 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-bq32k.c b/drivers/rtc/rtc-bq32k.c
new file mode 100644
index 000000000..573231613
--- /dev/null
+++ b/drivers/rtc/rtc-bq32k.c
@@ -0,0 +1,341 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for TI BQ32000 RTC.
+ *
+ * Copyright (C) 2009 Semihalf.
+ * Copyright (C) 2014 Pavel Machek <pavel@denx.de>
+ *
+ * You can get hardware description at
+ * https://www.ti.com/lit/ds/symlink/bq32000.pdf
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/rtc.h>
+#include <linux/init.h>
+#include <linux/kstrtox.h>
+#include <linux/errno.h>
+#include <linux/bcd.h>
+#include <linux/delay.h>
+
+#define BQ32K_SECONDS		0x00	/* Seconds register address */
+#define BQ32K_SECONDS_MASK	0x7F	/* Mask over seconds value */
+#define BQ32K_STOP		0x80	/* Oscillator Stop flat */
+
+#define BQ32K_MINUTES		0x01	/* Minutes register address */
+#define BQ32K_MINUTES_MASK	0x7F	/* Mask over minutes value */
+#define BQ32K_OF		0x80	/* Oscillator Failure flag */
+
+#define BQ32K_HOURS_MASK	0x3F	/* Mask over hours value */
+#define BQ32K_CENT		0x40	/* Century flag */
+#define BQ32K_CENT_EN		0x80	/* Century flag enable bit */
+
+#define BQ32K_CALIBRATION	0x07	/* CAL_CFG1, calibration and control */
+#define BQ32K_TCH2		0x08	/* Trickle charge enable */
+#define BQ32K_CFG2		0x09	/* Trickle charger control */
+#define BQ32K_TCFE		BIT(6)	/* Trickle charge FET bypass */
+
+#define MAX_LEN			10	/* Maximum number of consecutive
+					 * register for this particular RTC.
+					 */
+
+struct bq32k_regs {
+	uint8_t		seconds;
+	uint8_t		minutes;
+	uint8_t		cent_hours;
+	uint8_t		day;
+	uint8_t		date;
+	uint8_t		month;
+	uint8_t		years;
+};
+
+static struct i2c_driver bq32k_driver;
+
+static int bq32k_read(struct device *dev, void *data, uint8_t off, uint8_t len)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct i2c_msg msgs[] = {
+		{
+			.addr = client->addr,
+			.flags = 0,
+			.len = 1,
+			.buf = &off,
+		}, {
+			.addr = client->addr,
+			.flags = I2C_M_RD,
+			.len = len,
+			.buf = data,
+		}
+	};
+
+	if (i2c_transfer(client->adapter, msgs, 2) == 2)
+		return 0;
+
+	return -EIO;
+}
+
+static int bq32k_write(struct device *dev, void *data, uint8_t off, uint8_t len)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	uint8_t buffer[MAX_LEN + 1];
+
+	buffer[0] = off;
+	memcpy(&buffer[1], data, len);
+
+	if (i2c_master_send(client, buffer, len + 1) == len + 1)
+		return 0;
+
+	return -EIO;
+}
+
+static int bq32k_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct bq32k_regs regs;
+	int error;
+
+	/*
+	 * When the device doesn't have the interrupt connected, prevent
+	 * userpace from polling the RTC registers too frequently.
+	 */
+	if (client->irq <= 0)
+		usleep_range(2000, 2500);
+
+	error = bq32k_read(dev, &regs, 0, sizeof(regs));
+	if (error)
+		return error;
+
+	/*
+	 * In case of oscillator failure, the register contents should be
+	 * considered invalid. The flag is cleared the next time the RTC is set.
+	 */
+	if (regs.minutes & BQ32K_OF)
+		return -EINVAL;
+
+	tm->tm_sec = bcd2bin(regs.seconds & BQ32K_SECONDS_MASK);
+	tm->tm_min = bcd2bin(regs.minutes & BQ32K_MINUTES_MASK);
+	tm->tm_hour = bcd2bin(regs.cent_hours & BQ32K_HOURS_MASK);
+	tm->tm_mday = bcd2bin(regs.date);
+	tm->tm_wday = bcd2bin(regs.day) - 1;
+	tm->tm_mon = bcd2bin(regs.month) - 1;
+	tm->tm_year = bcd2bin(regs.years) +
+				((regs.cent_hours & BQ32K_CENT) ? 100 : 0);
+
+	return 0;
+}
+
+static int bq32k_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct bq32k_regs regs;
+
+	regs.seconds = bin2bcd(tm->tm_sec);
+	regs.minutes = bin2bcd(tm->tm_min);
+	regs.cent_hours = bin2bcd(tm->tm_hour) | BQ32K_CENT_EN;
+	regs.day = bin2bcd(tm->tm_wday + 1);
+	regs.date = bin2bcd(tm->tm_mday);
+	regs.month = bin2bcd(tm->tm_mon + 1);
+
+	if (tm->tm_year >= 100) {
+		regs.cent_hours |= BQ32K_CENT;
+		regs.years = bin2bcd(tm->tm_year - 100);
+	} else
+		regs.years = bin2bcd(tm->tm_year);
+
+	return bq32k_write(dev, &regs, 0, sizeof(regs));
+}
+
+static const struct rtc_class_ops bq32k_rtc_ops = {
+	.read_time	= bq32k_rtc_read_time,
+	.set_time	= bq32k_rtc_set_time,
+};
+
+static int trickle_charger_of_init(struct device *dev, struct device_node *node)
+{
+	unsigned char reg;
+	int error;
+	u32 ohms = 0;
+
+	if (of_property_read_u32(node, "trickle-resistor-ohms" , &ohms))
+		return 0;
+
+	switch (ohms) {
+	case 180+940:
+		/*
+		 * TCHE[3:0] == 0x05, TCH2 == 1, TCFE == 0 (charging
+		 * over diode and 940ohm resistor)
+		 */
+
+		if (of_property_read_bool(node, "trickle-diode-disable")) {
+			dev_err(dev, "diode and resistor mismatch\n");
+			return -EINVAL;
+		}
+		reg = 0x05;
+		break;
+
+	case 180+20000:
+		/* diode disabled */
+
+		if (!of_property_read_bool(node, "trickle-diode-disable")) {
+			dev_err(dev, "bq32k: diode and resistor mismatch\n");
+			return -EINVAL;
+		}
+		reg = 0x45;
+		break;
+
+	default:
+		dev_err(dev, "invalid resistor value (%d)\n", ohms);
+		return -EINVAL;
+	}
+
+	error = bq32k_write(dev, &reg, BQ32K_CFG2, 1);
+	if (error)
+		return error;
+
+	reg = 0x20;
+	error = bq32k_write(dev, &reg, BQ32K_TCH2, 1);
+	if (error)
+		return error;
+
+	dev_info(dev, "Enabled trickle RTC battery charge.\n");
+	return 0;
+}
+
+static ssize_t bq32k_sysfs_show_tricklecharge_bypass(struct device *dev,
+					       struct device_attribute *attr,
+					       char *buf)
+{
+	int reg, error;
+
+	error = bq32k_read(dev, &reg, BQ32K_CFG2, 1);
+	if (error)
+		return error;
+
+	return sprintf(buf, "%d\n", (reg & BQ32K_TCFE) ? 1 : 0);
+}
+
+static ssize_t bq32k_sysfs_store_tricklecharge_bypass(struct device *dev,
+						struct device_attribute *attr,
+						const char *buf, size_t count)
+{
+	int reg, enable, error;
+
+	if (kstrtoint(buf, 0, &enable))
+		return -EINVAL;
+
+	error = bq32k_read(dev, &reg, BQ32K_CFG2, 1);
+	if (error)
+		return error;
+
+	if (enable) {
+		reg |= BQ32K_TCFE;
+		error = bq32k_write(dev, &reg, BQ32K_CFG2, 1);
+		if (error)
+			return error;
+
+		dev_info(dev, "Enabled trickle charge FET bypass.\n");
+	} else {
+		reg &= ~BQ32K_TCFE;
+		error = bq32k_write(dev, &reg, BQ32K_CFG2, 1);
+		if (error)
+			return error;
+
+		dev_info(dev, "Disabled trickle charge FET bypass.\n");
+	}
+
+	return count;
+}
+
+static DEVICE_ATTR(trickle_charge_bypass, 0644,
+		   bq32k_sysfs_show_tricklecharge_bypass,
+		   bq32k_sysfs_store_tricklecharge_bypass);
+
+static int bq32k_sysfs_register(struct device *dev)
+{
+	return device_create_file(dev, &dev_attr_trickle_charge_bypass);
+}
+
+static void bq32k_sysfs_unregister(struct device *dev)
+{
+	device_remove_file(dev, &dev_attr_trickle_charge_bypass);
+}
+
+static int bq32k_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct rtc_device *rtc;
+	uint8_t reg;
+	int error;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -ENODEV;
+
+	/* Check Oscillator Stop flag */
+	error = bq32k_read(dev, &reg, BQ32K_SECONDS, 1);
+	if (!error && (reg & BQ32K_STOP)) {
+		dev_warn(dev, "Oscillator was halted. Restarting...\n");
+		reg &= ~BQ32K_STOP;
+		error = bq32k_write(dev, &reg, BQ32K_SECONDS, 1);
+	}
+	if (error)
+		return error;
+
+	/* Check Oscillator Failure flag */
+	error = bq32k_read(dev, &reg, BQ32K_MINUTES, 1);
+	if (error)
+		return error;
+	if (reg & BQ32K_OF)
+		dev_warn(dev, "Oscillator Failure. Check RTC battery.\n");
+
+	if (client->dev.of_node)
+		trickle_charger_of_init(dev, client->dev.of_node);
+
+	rtc = devm_rtc_device_register(&client->dev, bq32k_driver.driver.name,
+						&bq32k_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	error = bq32k_sysfs_register(&client->dev);
+	if (error) {
+		dev_err(&client->dev,
+			"Unable to create sysfs entries for rtc bq32000\n");
+		return error;
+	}
+
+
+	i2c_set_clientdata(client, rtc);
+
+	return 0;
+}
+
+static void bq32k_remove(struct i2c_client *client)
+{
+	bq32k_sysfs_unregister(&client->dev);
+}
+
+static const struct i2c_device_id bq32k_id[] = {
+	{ .name = "bq32000" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, bq32k_id);
+
+static const __maybe_unused struct of_device_id bq32k_of_match[] = {
+	{ .compatible = "ti,bq32000" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, bq32k_of_match);
+
+static struct i2c_driver bq32k_driver = {
+	.driver = {
+		.name	= "bq32k",
+		.of_match_table = of_match_ptr(bq32k_of_match),
+	},
+	.probe		= bq32k_probe,
+	.remove		= bq32k_remove,
+	.id_table	= bq32k_id,
+};
+
+module_i2c_driver(bq32k_driver);
+
+MODULE_AUTHOR("Semihalf, Piotr Ziecik <kosmo@semihalf.com>");
+MODULE_DESCRIPTION("TI BQ32000 I2C RTC driver");
+MODULE_LICENSE("GPL");