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, 405 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-ab8500.c b/drivers/rtc/rtc-ab8500.c
new file mode 100644
index 000000000..0978bd0a3
--- /dev/null
+++ b/drivers/rtc/rtc-ab8500.c
@@ -0,0 +1,405 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) ST-Ericsson SA 2010
+ *
+ * Author: Virupax Sadashivpetimath <virupax.sadashivpetimath@stericsson.com>
+ *
+ * RTC clock driver for the RTC part of the AB8500 Power management chip.
+ * Based on RTC clock driver for the AB3100 Analog Baseband Chip by
+ * Linus Walleij <linus.walleij@stericsson.com>
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/mfd/abx500.h>
+#include <linux/mfd/abx500/ab8500.h>
+#include <linux/delay.h>
+#include <linux/of.h>
+#include <linux/pm_wakeirq.h>
+
+#define AB8500_RTC_SOFF_STAT_REG	0x00
+#define AB8500_RTC_CC_CONF_REG		0x01
+#define AB8500_RTC_READ_REQ_REG		0x02
+#define AB8500_RTC_WATCH_TSECMID_REG	0x03
+#define AB8500_RTC_WATCH_TSECHI_REG	0x04
+#define AB8500_RTC_WATCH_TMIN_LOW_REG	0x05
+#define AB8500_RTC_WATCH_TMIN_MID_REG	0x06
+#define AB8500_RTC_WATCH_TMIN_HI_REG	0x07
+#define AB8500_RTC_ALRM_MIN_LOW_REG	0x08
+#define AB8500_RTC_ALRM_MIN_MID_REG	0x09
+#define AB8500_RTC_ALRM_MIN_HI_REG	0x0A
+#define AB8500_RTC_STAT_REG		0x0B
+#define AB8500_RTC_BKUP_CHG_REG		0x0C
+#define AB8500_RTC_FORCE_BKUP_REG	0x0D
+#define AB8500_RTC_CALIB_REG		0x0E
+#define AB8500_RTC_SWITCH_STAT_REG	0x0F
+
+/* RtcReadRequest bits */
+#define RTC_READ_REQUEST		0x01
+#define RTC_WRITE_REQUEST		0x02
+
+/* RtcCtrl bits */
+#define RTC_ALARM_ENA			0x04
+#define RTC_STATUS_DATA			0x01
+
+#define COUNTS_PER_SEC			(0xF000 / 60)
+
+static const u8 ab8500_rtc_time_regs[] = {
+	AB8500_RTC_WATCH_TMIN_HI_REG, AB8500_RTC_WATCH_TMIN_MID_REG,
+	AB8500_RTC_WATCH_TMIN_LOW_REG, AB8500_RTC_WATCH_TSECHI_REG,
+	AB8500_RTC_WATCH_TSECMID_REG
+};
+
+static const u8 ab8500_rtc_alarm_regs[] = {
+	AB8500_RTC_ALRM_MIN_HI_REG, AB8500_RTC_ALRM_MIN_MID_REG,
+	AB8500_RTC_ALRM_MIN_LOW_REG
+};
+
+static int ab8500_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	unsigned long timeout = jiffies + HZ;
+	int retval, i;
+	unsigned long mins, secs;
+	unsigned char buf[ARRAY_SIZE(ab8500_rtc_time_regs)];
+	u8 value;
+
+	/* Request a data read */
+	retval = abx500_set_register_interruptible(dev,
+		AB8500_RTC, AB8500_RTC_READ_REQ_REG, RTC_READ_REQUEST);
+	if (retval < 0)
+		return retval;
+
+	/* Wait for some cycles after enabling the rtc read in ab8500 */
+	while (time_before(jiffies, timeout)) {
+		retval = abx500_get_register_interruptible(dev,
+			AB8500_RTC, AB8500_RTC_READ_REQ_REG, &value);
+		if (retval < 0)
+			return retval;
+
+		if (!(value & RTC_READ_REQUEST))
+			break;
+
+		usleep_range(1000, 5000);
+	}
+
+	/* Read the Watchtime registers */
+	for (i = 0; i < ARRAY_SIZE(ab8500_rtc_time_regs); i++) {
+		retval = abx500_get_register_interruptible(dev,
+			AB8500_RTC, ab8500_rtc_time_regs[i], &value);
+		if (retval < 0)
+			return retval;
+		buf[i] = value;
+	}
+
+	mins = (buf[0] << 16) | (buf[1] << 8) | buf[2];
+
+	secs =	(buf[3] << 8) | buf[4];
+	secs =	secs / COUNTS_PER_SEC;
+	secs =	secs + (mins * 60);
+
+	rtc_time64_to_tm(secs, tm);
+	return 0;
+}
+
+static int ab8500_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	int retval, i;
+	unsigned char buf[ARRAY_SIZE(ab8500_rtc_time_regs)];
+	unsigned long no_secs, no_mins, secs = 0;
+
+	secs = rtc_tm_to_time64(tm);
+
+	no_mins = secs / 60;
+
+	no_secs = secs % 60;
+	/* Make the seconds count as per the RTC resolution */
+	no_secs = no_secs * COUNTS_PER_SEC;
+
+	buf[4] = no_secs & 0xFF;
+	buf[3] = (no_secs >> 8) & 0xFF;
+
+	buf[2] = no_mins & 0xFF;
+	buf[1] = (no_mins >> 8) & 0xFF;
+	buf[0] = (no_mins >> 16) & 0xFF;
+
+	for (i = 0; i < ARRAY_SIZE(ab8500_rtc_time_regs); i++) {
+		retval = abx500_set_register_interruptible(dev, AB8500_RTC,
+			ab8500_rtc_time_regs[i], buf[i]);
+		if (retval < 0)
+			return retval;
+	}
+
+	/* Request a data write */
+	return abx500_set_register_interruptible(dev, AB8500_RTC,
+		AB8500_RTC_READ_REQ_REG, RTC_WRITE_REQUEST);
+}
+
+static int ab8500_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	int retval, i;
+	u8 rtc_ctrl, value;
+	unsigned char buf[ARRAY_SIZE(ab8500_rtc_alarm_regs)];
+	unsigned long secs, mins;
+
+	/* Check if the alarm is enabled or not */
+	retval = abx500_get_register_interruptible(dev, AB8500_RTC,
+		AB8500_RTC_STAT_REG, &rtc_ctrl);
+	if (retval < 0)
+		return retval;
+
+	if (rtc_ctrl & RTC_ALARM_ENA)
+		alarm->enabled = 1;
+	else
+		alarm->enabled = 0;
+
+	alarm->pending = 0;
+
+	for (i = 0; i < ARRAY_SIZE(ab8500_rtc_alarm_regs); i++) {
+		retval = abx500_get_register_interruptible(dev, AB8500_RTC,
+			ab8500_rtc_alarm_regs[i], &value);
+		if (retval < 0)
+			return retval;
+		buf[i] = value;
+	}
+
+	mins = (buf[0] << 16) | (buf[1] << 8) | (buf[2]);
+	secs = mins * 60;
+
+	rtc_time64_to_tm(secs, &alarm->time);
+
+	return 0;
+}
+
+static int ab8500_rtc_irq_enable(struct device *dev, unsigned int enabled)
+{
+	return abx500_mask_and_set_register_interruptible(dev, AB8500_RTC,
+		AB8500_RTC_STAT_REG, RTC_ALARM_ENA,
+		enabled ? RTC_ALARM_ENA : 0);
+}
+
+static int ab8500_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	int retval, i;
+	unsigned char buf[ARRAY_SIZE(ab8500_rtc_alarm_regs)];
+	unsigned long mins;
+
+	mins = (unsigned long)rtc_tm_to_time64(&alarm->time) / 60;
+
+	buf[2] = mins & 0xFF;
+	buf[1] = (mins >> 8) & 0xFF;
+	buf[0] = (mins >> 16) & 0xFF;
+
+	/* Set the alarm time */
+	for (i = 0; i < ARRAY_SIZE(ab8500_rtc_alarm_regs); i++) {
+		retval = abx500_set_register_interruptible(dev, AB8500_RTC,
+			ab8500_rtc_alarm_regs[i], buf[i]);
+		if (retval < 0)
+			return retval;
+	}
+
+	return ab8500_rtc_irq_enable(dev, alarm->enabled);
+}
+
+static int ab8500_rtc_set_calibration(struct device *dev, int calibration)
+{
+	int retval;
+	u8  rtccal = 0;
+
+	/*
+	 * Check that the calibration value (which is in units of 0.5
+	 * parts-per-million) is in the AB8500's range for RtcCalibration
+	 * register. -128 (0x80) is not permitted because the AB8500 uses
+	 * a sign-bit rather than two's complement, so 0x80 is just another
+	 * representation of zero.
+	 */
+	if ((calibration < -127) || (calibration > 127)) {
+		dev_err(dev, "RtcCalibration value outside permitted range\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * The AB8500 uses sign (in bit7) and magnitude (in bits0-7)
+	 * so need to convert to this sort of representation before writing
+	 * into RtcCalibration register...
+	 */
+	if (calibration >= 0)
+		rtccal = 0x7F & calibration;
+	else
+		rtccal = ~(calibration - 1) | 0x80;
+
+	retval = abx500_set_register_interruptible(dev, AB8500_RTC,
+			AB8500_RTC_CALIB_REG, rtccal);
+
+	return retval;
+}
+
+static int ab8500_rtc_get_calibration(struct device *dev, int *calibration)
+{
+	int retval;
+	u8  rtccal = 0;
+
+	retval =  abx500_get_register_interruptible(dev, AB8500_RTC,
+			AB8500_RTC_CALIB_REG, &rtccal);
+	if (retval >= 0) {
+		/*
+		 * The AB8500 uses sign (in bit7) and magnitude (in bits0-7)
+		 * so need to convert value from RtcCalibration register into
+		 * a two's complement signed value...
+		 */
+		if (rtccal & 0x80)
+			*calibration = 0 - (rtccal & 0x7F);
+		else
+			*calibration = 0x7F & rtccal;
+	}
+
+	return retval;
+}
+
+static ssize_t ab8500_sysfs_store_rtc_calibration(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	int retval;
+	int calibration = 0;
+
+	if (sscanf(buf, " %i ", &calibration) != 1) {
+		dev_err(dev, "Failed to store RTC calibration attribute\n");
+		return -EINVAL;
+	}
+
+	retval = ab8500_rtc_set_calibration(dev, calibration);
+
+	return retval ? retval : count;
+}
+
+static ssize_t ab8500_sysfs_show_rtc_calibration(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	int  retval = 0;
+	int  calibration = 0;
+
+	retval = ab8500_rtc_get_calibration(dev, &calibration);
+	if (retval < 0) {
+		dev_err(dev, "Failed to read RTC calibration attribute\n");
+		return retval;
+	}
+
+	return sysfs_emit(buf, "%d\n", calibration);
+}
+
+static DEVICE_ATTR(rtc_calibration, S_IRUGO | S_IWUSR,
+		   ab8500_sysfs_show_rtc_calibration,
+		   ab8500_sysfs_store_rtc_calibration);
+
+static struct attribute *ab8500_rtc_attrs[] = {
+	&dev_attr_rtc_calibration.attr,
+	NULL
+};
+
+static const struct attribute_group ab8500_rtc_sysfs_files = {
+	.attrs	= ab8500_rtc_attrs,
+};
+
+static irqreturn_t rtc_alarm_handler(int irq, void *data)
+{
+	struct rtc_device *rtc = data;
+	unsigned long events = RTC_IRQF | RTC_AF;
+
+	dev_dbg(&rtc->dev, "%s\n", __func__);
+	rtc_update_irq(rtc, 1, events);
+
+	return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops ab8500_rtc_ops = {
+	.read_time		= ab8500_rtc_read_time,
+	.set_time		= ab8500_rtc_set_time,
+	.read_alarm		= ab8500_rtc_read_alarm,
+	.set_alarm		= ab8500_rtc_set_alarm,
+	.alarm_irq_enable	= ab8500_rtc_irq_enable,
+};
+
+static const struct platform_device_id ab85xx_rtc_ids[] = {
+	{ .name = "ab8500-rtc" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(platform, ab85xx_rtc_ids);
+
+static int ab8500_rtc_probe(struct platform_device *pdev)
+{
+	int err;
+	struct rtc_device *rtc;
+	u8 rtc_ctrl;
+	int irq;
+
+	irq = platform_get_irq_byname(pdev, "ALARM");
+	if (irq < 0)
+		return irq;
+
+	/* For RTC supply test */
+	err = abx500_mask_and_set_register_interruptible(&pdev->dev, AB8500_RTC,
+		AB8500_RTC_STAT_REG, RTC_STATUS_DATA, RTC_STATUS_DATA);
+	if (err < 0)
+		return err;
+
+	/* Wait for reset by the PorRtc */
+	usleep_range(1000, 5000);
+
+	err = abx500_get_register_interruptible(&pdev->dev, AB8500_RTC,
+		AB8500_RTC_STAT_REG, &rtc_ctrl);
+	if (err < 0)
+		return err;
+
+	/* Check if the RTC Supply fails */
+	if (!(rtc_ctrl & RTC_STATUS_DATA)) {
+		dev_err(&pdev->dev, "RTC supply failure\n");
+		return -ENODEV;
+	}
+
+	devm_device_init_wakeup(&pdev->dev);
+
+	rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	rtc->ops = &ab8500_rtc_ops;
+
+	err = devm_request_threaded_irq(&pdev->dev, irq, NULL,
+			rtc_alarm_handler, IRQF_ONESHOT,
+			"ab8500-rtc", rtc);
+	if (err < 0)
+		return err;
+
+	devm_pm_set_wake_irq(&pdev->dev, irq);
+	platform_set_drvdata(pdev, rtc);
+
+	set_bit(RTC_FEATURE_ALARM_RES_MINUTE, rtc->features);
+	clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, rtc->features);
+
+	rtc->range_max = (1ULL << 24) * 60 - 1; // 24-bit minutes + 59 secs
+	rtc->start_secs = RTC_TIMESTAMP_BEGIN_2000;
+	rtc->set_start_time = true;
+
+	err = rtc_add_group(rtc, &ab8500_rtc_sysfs_files);
+	if (err)
+		return err;
+
+	return devm_rtc_register_device(rtc);
+}
+
+static struct platform_driver ab8500_rtc_driver = {
+	.driver = {
+		.name = "ab8500-rtc",
+	},
+	.probe	= ab8500_rtc_probe,
+	.id_table = ab85xx_rtc_ids,
+};
+
+module_platform_driver(ab8500_rtc_driver);
+
+MODULE_AUTHOR("Virupax Sadashivpetimath <virupax.sadashivpetimath@stericsson.com>");
+MODULE_DESCRIPTION("AB8500 RTC Driver");
+MODULE_LICENSE("GPL v2");