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, 460 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-rk808.c b/drivers/rtc/rtc-rk808.c
new file mode 100644
index 000000000..59b8e9a30
--- /dev/null
+++ b/drivers/rtc/rtc-rk808.c
@@ -0,0 +1,460 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * RTC driver for Rockchip RK808
+ *
+ * Copyright (c) 2014, Fuzhou Rockchip Electronics Co., Ltd
+ *
+ * Author: Chris Zhong <zyw@rock-chips.com>
+ * Author: Zhang Qing <zhangqing@rock-chips.com>
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+#include <linux/mfd/rk808.h>
+#include <linux/platform_device.h>
+
+/* RTC_CTRL_REG bitfields */
+#define BIT_RTC_CTRL_REG_STOP_RTC_M		BIT(0)
+
+/* RK808 has a shadowed register for saving a "frozen" RTC time.
+ * When user setting "GET_TIME" to 1, the time will save in this shadowed
+ * register. If set "READSEL" to 1, user read rtc time register, actually
+ * get the time of that moment. If we need the real time, clr this bit.
+ */
+#define BIT_RTC_CTRL_REG_RTC_GET_TIME		BIT(6)
+#define BIT_RTC_CTRL_REG_RTC_READSEL_M		BIT(7)
+#define BIT_RTC_INTERRUPTS_REG_IT_ALARM_M	BIT(3)
+#define RTC_STATUS_MASK		0xFE
+
+#define SECONDS_REG_MSK		0x7F
+#define MINUTES_REG_MAK		0x7F
+#define HOURS_REG_MSK		0x3F
+#define DAYS_REG_MSK		0x3F
+#define MONTHS_REG_MSK		0x1F
+#define YEARS_REG_MSK		0xFF
+#define WEEKS_REG_MSK		0x7
+
+/* REG_SECONDS_REG through REG_YEARS_REG is how many registers? */
+
+#define NUM_TIME_REGS	(RK808_WEEKS_REG - RK808_SECONDS_REG + 1)
+#define NUM_ALARM_REGS	(RK808_ALARM_YEARS_REG - RK808_ALARM_SECONDS_REG + 1)
+
+struct rk_rtc_compat_reg {
+	unsigned int ctrl_reg;
+	unsigned int status_reg;
+	unsigned int alarm_seconds_reg;
+	unsigned int int_reg;
+	unsigned int seconds_reg;
+};
+
+struct rk808_rtc {
+	struct regmap *regmap;
+	struct rtc_device *rtc;
+	struct rk_rtc_compat_reg *creg;
+	int irq;
+};
+
+/*
+ * The Rockchip calendar used by the RK808 counts November with 31 days. We use
+ * these translation functions to convert its dates to/from the Gregorian
+ * calendar used by the rest of the world. We arbitrarily define Jan 1st, 2016
+ * as the day when both calendars were in sync, and treat all other dates
+ * relative to that.
+ * NOTE: Other system software (e.g. firmware) that reads the same hardware must
+ * implement this exact same conversion algorithm, with the same anchor date.
+ */
+static time64_t nov2dec_transitions(struct rtc_time *tm)
+{
+	return (tm->tm_year + 1900) - 2016 + (tm->tm_mon + 1 > 11 ? 1 : 0);
+}
+
+static void rockchip_to_gregorian(struct rtc_time *tm)
+{
+	/* If it's Nov 31st, rtc_tm_to_time64() will count that like Dec 1st */
+	time64_t time = rtc_tm_to_time64(tm);
+	rtc_time64_to_tm(time + nov2dec_transitions(tm) * 86400, tm);
+}
+
+static void gregorian_to_rockchip(struct rtc_time *tm)
+{
+	time64_t extra_days = nov2dec_transitions(tm);
+	time64_t time = rtc_tm_to_time64(tm);
+	rtc_time64_to_tm(time - extra_days * 86400, tm);
+
+	/* Compensate if we went back over Nov 31st (will work up to 2381) */
+	if (nov2dec_transitions(tm) < extra_days) {
+		if (tm->tm_mon + 1 == 11)
+			tm->tm_mday++;	/* This may result in 31! */
+		else
+			rtc_time64_to_tm(time - (extra_days - 1) * 86400, tm);
+	}
+}
+
+/* Read current time and date in RTC */
+static int rk808_rtc_readtime(struct device *dev, struct rtc_time *tm)
+{
+	struct rk808_rtc *rk808_rtc = dev_get_drvdata(dev);
+	u8 rtc_data[NUM_TIME_REGS];
+	int ret;
+
+	/* Force an update of the shadowed registers right now */
+	ret = regmap_update_bits(rk808_rtc->regmap, rk808_rtc->creg->ctrl_reg,
+				 BIT_RTC_CTRL_REG_RTC_GET_TIME,
+				 BIT_RTC_CTRL_REG_RTC_GET_TIME);
+	if (ret) {
+		dev_err(dev, "Failed to update bits rtc_ctrl: %d\n", ret);
+		return ret;
+	}
+
+	/*
+	 * After we set the GET_TIME bit, the rtc time can't be read
+	 * immediately. So we should wait up to 31.25 us, about one cycle of
+	 * 32khz. If we clear the GET_TIME bit here, the time of i2c transfer
+	 * certainly more than 31.25us: 16 * 2.5us at 400kHz bus frequency.
+	 */
+	ret = regmap_update_bits(rk808_rtc->regmap, rk808_rtc->creg->ctrl_reg,
+				 BIT_RTC_CTRL_REG_RTC_GET_TIME,
+				 0);
+	if (ret) {
+		dev_err(dev, "Failed to update bits rtc_ctrl: %d\n", ret);
+		return ret;
+	}
+
+	ret = regmap_bulk_read(rk808_rtc->regmap, rk808_rtc->creg->seconds_reg,
+			       rtc_data, NUM_TIME_REGS);
+	if (ret) {
+		dev_err(dev, "Failed to bulk read rtc_data: %d\n", ret);
+		return ret;
+	}
+
+	tm->tm_sec = bcd2bin(rtc_data[0] & SECONDS_REG_MSK);
+	tm->tm_min = bcd2bin(rtc_data[1] & MINUTES_REG_MAK);
+	tm->tm_hour = bcd2bin(rtc_data[2] & HOURS_REG_MSK);
+	tm->tm_mday = bcd2bin(rtc_data[3] & DAYS_REG_MSK);
+	tm->tm_mon = (bcd2bin(rtc_data[4] & MONTHS_REG_MSK)) - 1;
+	tm->tm_year = (bcd2bin(rtc_data[5] & YEARS_REG_MSK)) + 100;
+	tm->tm_wday = bcd2bin(rtc_data[6] & WEEKS_REG_MSK);
+	rockchip_to_gregorian(tm);
+	dev_dbg(dev, "RTC date/time %ptRd(%d) %ptRt\n", tm, tm->tm_wday, tm);
+
+	return ret;
+}
+
+/* Set current time and date in RTC */
+static int rk808_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rk808_rtc *rk808_rtc = dev_get_drvdata(dev);
+	u8 rtc_data[NUM_TIME_REGS];
+	int ret;
+
+	dev_dbg(dev, "set RTC date/time %ptRd(%d) %ptRt\n", tm, tm->tm_wday, tm);
+	gregorian_to_rockchip(tm);
+	rtc_data[0] = bin2bcd(tm->tm_sec);
+	rtc_data[1] = bin2bcd(tm->tm_min);
+	rtc_data[2] = bin2bcd(tm->tm_hour);
+	rtc_data[3] = bin2bcd(tm->tm_mday);
+	rtc_data[4] = bin2bcd(tm->tm_mon + 1);
+	rtc_data[5] = bin2bcd(tm->tm_year - 100);
+	rtc_data[6] = bin2bcd(tm->tm_wday);
+
+	/* Stop RTC while updating the RTC registers */
+	ret = regmap_update_bits(rk808_rtc->regmap, rk808_rtc->creg->ctrl_reg,
+				 BIT_RTC_CTRL_REG_STOP_RTC_M,
+				 BIT_RTC_CTRL_REG_STOP_RTC_M);
+	if (ret) {
+		dev_err(dev, "Failed to update RTC control: %d\n", ret);
+		return ret;
+	}
+
+	ret = regmap_bulk_write(rk808_rtc->regmap, rk808_rtc->creg->seconds_reg,
+				rtc_data, NUM_TIME_REGS);
+	if (ret) {
+		dev_err(dev, "Failed to bull write rtc_data: %d\n", ret);
+		return ret;
+	}
+	/* Start RTC again */
+	ret = regmap_update_bits(rk808_rtc->regmap, rk808_rtc->creg->ctrl_reg,
+				 BIT_RTC_CTRL_REG_STOP_RTC_M, 0);
+	if (ret) {
+		dev_err(dev, "Failed to update RTC control: %d\n", ret);
+		return ret;
+	}
+	return 0;
+}
+
+/* Read alarm time and date in RTC */
+static int rk808_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct rk808_rtc *rk808_rtc = dev_get_drvdata(dev);
+	u8 alrm_data[NUM_ALARM_REGS];
+	uint32_t int_reg;
+	int ret;
+
+	ret = regmap_bulk_read(rk808_rtc->regmap,
+			       rk808_rtc->creg->alarm_seconds_reg,
+			       alrm_data, NUM_ALARM_REGS);
+	if (ret) {
+		dev_err(dev, "Failed to read RTC alarm date REG: %d\n", ret);
+		return ret;
+	}
+
+	alrm->time.tm_sec = bcd2bin(alrm_data[0] & SECONDS_REG_MSK);
+	alrm->time.tm_min = bcd2bin(alrm_data[1] & MINUTES_REG_MAK);
+	alrm->time.tm_hour = bcd2bin(alrm_data[2] & HOURS_REG_MSK);
+	alrm->time.tm_mday = bcd2bin(alrm_data[3] & DAYS_REG_MSK);
+	alrm->time.tm_mon = (bcd2bin(alrm_data[4] & MONTHS_REG_MSK)) - 1;
+	alrm->time.tm_year = (bcd2bin(alrm_data[5] & YEARS_REG_MSK)) + 100;
+	rockchip_to_gregorian(&alrm->time);
+
+	ret = regmap_read(rk808_rtc->regmap, rk808_rtc->creg->int_reg, &int_reg);
+	if (ret) {
+		dev_err(dev, "Failed to read RTC INT REG: %d\n", ret);
+		return ret;
+	}
+
+	dev_dbg(dev, "alrm read RTC date/time %ptRd(%d) %ptRt\n",
+		&alrm->time, alrm->time.tm_wday, &alrm->time);
+
+	alrm->enabled = (int_reg & BIT_RTC_INTERRUPTS_REG_IT_ALARM_M) ? 1 : 0;
+
+	return 0;
+}
+
+static int rk808_rtc_stop_alarm(struct rk808_rtc *rk808_rtc)
+{
+	int ret;
+
+	ret = regmap_update_bits(rk808_rtc->regmap, rk808_rtc->creg->int_reg,
+				 BIT_RTC_INTERRUPTS_REG_IT_ALARM_M, 0);
+
+	return ret;
+}
+
+static int rk808_rtc_start_alarm(struct rk808_rtc *rk808_rtc)
+{
+	int ret;
+
+	ret = regmap_update_bits(rk808_rtc->regmap, rk808_rtc->creg->int_reg,
+				 BIT_RTC_INTERRUPTS_REG_IT_ALARM_M,
+				 BIT_RTC_INTERRUPTS_REG_IT_ALARM_M);
+
+	return ret;
+}
+
+static int rk808_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct rk808_rtc *rk808_rtc = dev_get_drvdata(dev);
+	u8 alrm_data[NUM_ALARM_REGS];
+	int ret;
+
+	ret = rk808_rtc_stop_alarm(rk808_rtc);
+	if (ret) {
+		dev_err(dev, "Failed to stop alarm: %d\n", ret);
+		return ret;
+	}
+	dev_dbg(dev, "alrm set RTC date/time %ptRd(%d) %ptRt\n",
+		&alrm->time, alrm->time.tm_wday, &alrm->time);
+
+	gregorian_to_rockchip(&alrm->time);
+	alrm_data[0] = bin2bcd(alrm->time.tm_sec);
+	alrm_data[1] = bin2bcd(alrm->time.tm_min);
+	alrm_data[2] = bin2bcd(alrm->time.tm_hour);
+	alrm_data[3] = bin2bcd(alrm->time.tm_mday);
+	alrm_data[4] = bin2bcd(alrm->time.tm_mon + 1);
+	alrm_data[5] = bin2bcd(alrm->time.tm_year - 100);
+
+	ret = regmap_bulk_write(rk808_rtc->regmap,
+				rk808_rtc->creg->alarm_seconds_reg,
+				alrm_data, NUM_ALARM_REGS);
+	if (ret) {
+		dev_err(dev, "Failed to bulk write: %d\n", ret);
+		return ret;
+	}
+	if (alrm->enabled) {
+		ret = rk808_rtc_start_alarm(rk808_rtc);
+		if (ret) {
+			dev_err(dev, "Failed to start alarm: %d\n", ret);
+			return ret;
+		}
+	}
+	return 0;
+}
+
+static int rk808_rtc_alarm_irq_enable(struct device *dev,
+				      unsigned int enabled)
+{
+	struct rk808_rtc *rk808_rtc = dev_get_drvdata(dev);
+
+	if (enabled)
+		return rk808_rtc_start_alarm(rk808_rtc);
+
+	return rk808_rtc_stop_alarm(rk808_rtc);
+}
+
+/*
+ * We will just handle setting the frequency and make use the framework for
+ * reading the periodic interupts.
+ *
+ * @freq: Current periodic IRQ freq:
+ * bit 0: every second
+ * bit 1: every minute
+ * bit 2: every hour
+ * bit 3: every day
+ */
+static irqreturn_t rk808_alarm_irq(int irq, void *data)
+{
+	struct rk808_rtc *rk808_rtc = data;
+	int ret;
+
+	ret = regmap_write(rk808_rtc->regmap, rk808_rtc->creg->status_reg,
+			   RTC_STATUS_MASK);
+	if (ret) {
+		dev_err(&rk808_rtc->rtc->dev,
+			"%s:Failed to update RTC status: %d\n", __func__, ret);
+		return ret;
+	}
+
+	rtc_update_irq(rk808_rtc->rtc, 1, RTC_IRQF | RTC_AF);
+	dev_dbg(&rk808_rtc->rtc->dev,
+		 "%s:irq=%d\n", __func__, irq);
+	return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops rk808_rtc_ops = {
+	.read_time = rk808_rtc_readtime,
+	.set_time = rk808_rtc_set_time,
+	.read_alarm = rk808_rtc_readalarm,
+	.set_alarm = rk808_rtc_setalarm,
+	.alarm_irq_enable = rk808_rtc_alarm_irq_enable,
+};
+
+#ifdef CONFIG_PM_SLEEP
+/* Turn off the alarm if it should not be a wake source. */
+static int rk808_rtc_suspend(struct device *dev)
+{
+	struct rk808_rtc *rk808_rtc = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		enable_irq_wake(rk808_rtc->irq);
+
+	return 0;
+}
+
+/* Enable the alarm if it should be enabled (in case it was disabled to
+ * prevent use as a wake source).
+ */
+static int rk808_rtc_resume(struct device *dev)
+{
+	struct rk808_rtc *rk808_rtc = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		disable_irq_wake(rk808_rtc->irq);
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(rk808_rtc_pm_ops,
+	rk808_rtc_suspend, rk808_rtc_resume);
+
+static struct rk_rtc_compat_reg rk808_creg = {
+	.ctrl_reg = RK808_RTC_CTRL_REG,
+	.status_reg = RK808_RTC_STATUS_REG,
+	.alarm_seconds_reg = RK808_ALARM_SECONDS_REG,
+	.int_reg = RK808_RTC_INT_REG,
+	.seconds_reg = RK808_SECONDS_REG,
+};
+
+static struct rk_rtc_compat_reg rk817_creg = {
+	.ctrl_reg = RK817_RTC_CTRL_REG,
+	.status_reg = RK817_RTC_STATUS_REG,
+	.alarm_seconds_reg = RK817_ALARM_SECONDS_REG,
+	.int_reg = RK817_RTC_INT_REG,
+	.seconds_reg = RK817_SECONDS_REG,
+};
+
+static int rk808_rtc_probe(struct platform_device *pdev)
+{
+	struct rk808 *rk808 = dev_get_drvdata(pdev->dev.parent);
+	struct rk808_rtc *rk808_rtc;
+	int ret;
+
+	rk808_rtc = devm_kzalloc(&pdev->dev, sizeof(*rk808_rtc), GFP_KERNEL);
+	if (rk808_rtc == NULL)
+		return -ENOMEM;
+
+	switch (rk808->variant) {
+	case RK809_ID:
+	case RK817_ID:
+		rk808_rtc->creg = &rk817_creg;
+		break;
+	default:
+		rk808_rtc->creg = &rk808_creg;
+		break;
+	}
+	platform_set_drvdata(pdev, rk808_rtc);
+	rk808_rtc->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!rk808_rtc->regmap)
+		return -ENODEV;
+
+	/* start rtc running by default, and use shadowed timer. */
+	ret = regmap_update_bits(rk808_rtc->regmap, rk808_rtc->creg->ctrl_reg,
+				 BIT_RTC_CTRL_REG_STOP_RTC_M |
+				 BIT_RTC_CTRL_REG_RTC_READSEL_M,
+				 BIT_RTC_CTRL_REG_RTC_READSEL_M);
+	if (ret) {
+		dev_err(&pdev->dev,
+			"Failed to update RTC control: %d\n", ret);
+		return ret;
+	}
+
+	ret = regmap_write(rk808_rtc->regmap, rk808_rtc->creg->status_reg,
+			   RTC_STATUS_MASK);
+	if (ret) {
+		dev_err(&pdev->dev,
+			"Failed to write RTC status: %d\n", ret);
+		return ret;
+	}
+
+	device_init_wakeup(&pdev->dev, true);
+
+	rk808_rtc->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(rk808_rtc->rtc))
+		return PTR_ERR(rk808_rtc->rtc);
+
+	rk808_rtc->rtc->ops = &rk808_rtc_ops;
+
+	rk808_rtc->irq = platform_get_irq(pdev, 0);
+	if (rk808_rtc->irq < 0)
+		return rk808_rtc->irq;
+
+	/* request alarm irq of rk808 */
+	ret = devm_request_threaded_irq(&pdev->dev, rk808_rtc->irq, NULL,
+					rk808_alarm_irq, 0,
+					"RTC alarm", rk808_rtc);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to request alarm IRQ %d: %d\n",
+			rk808_rtc->irq, ret);
+		return ret;
+	}
+
+	return devm_rtc_register_device(rk808_rtc->rtc);
+}
+
+static struct platform_driver rk808_rtc_driver = {
+	.probe = rk808_rtc_probe,
+	.driver = {
+		.name = "rk808-rtc",
+		.pm = &rk808_rtc_pm_ops,
+	},
+};
+
+module_platform_driver(rk808_rtc_driver);
+
+MODULE_DESCRIPTION("RTC driver for the rk808 series PMICs");
+MODULE_AUTHOR("Chris Zhong <zyw@rock-chips.com>");
+MODULE_AUTHOR("Zhang Qing <zhangqing@rock-chips.com>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:rk808-rtc");