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, 321 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-mv.c b/drivers/rtc/rtc-mv.c
new file mode 100644
index 000000000..db64c459e
--- /dev/null
+++ b/drivers/rtc/rtc-mv.c
@@ -0,0 +1,321 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for the RTC in Marvell SoCs.
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+#include <linux/bitops.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/delay.h>
+#include <linux/clk.h>
+#include <linux/gfp.h>
+#include <linux/module.h>
+
+
+#define RTC_TIME_REG_OFFS	0
+#define RTC_SECONDS_OFFS	0
+#define RTC_MINUTES_OFFS	8
+#define RTC_HOURS_OFFS		16
+#define RTC_WDAY_OFFS		24
+#define RTC_HOURS_12H_MODE	BIT(22) /* 12 hour mode */
+
+#define RTC_DATE_REG_OFFS	4
+#define RTC_MDAY_OFFS		0
+#define RTC_MONTH_OFFS		8
+#define RTC_YEAR_OFFS		16
+
+#define RTC_ALARM_TIME_REG_OFFS	8
+#define RTC_ALARM_DATE_REG_OFFS	0xc
+#define RTC_ALARM_VALID		BIT(7)
+
+#define RTC_ALARM_INTERRUPT_MASK_REG_OFFS	0x10
+#define RTC_ALARM_INTERRUPT_CASUE_REG_OFFS	0x14
+
+struct rtc_plat_data {
+	struct rtc_device *rtc;
+	void __iomem *ioaddr;
+	int		irq;
+	struct clk	*clk;
+};
+
+static int mv_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+	void __iomem *ioaddr = pdata->ioaddr;
+	u32	rtc_reg;
+
+	rtc_reg = (bin2bcd(tm->tm_sec) << RTC_SECONDS_OFFS) |
+		(bin2bcd(tm->tm_min) << RTC_MINUTES_OFFS) |
+		(bin2bcd(tm->tm_hour) << RTC_HOURS_OFFS) |
+		(bin2bcd(tm->tm_wday) << RTC_WDAY_OFFS);
+	writel(rtc_reg, ioaddr + RTC_TIME_REG_OFFS);
+
+	rtc_reg = (bin2bcd(tm->tm_mday) << RTC_MDAY_OFFS) |
+		(bin2bcd(tm->tm_mon + 1) << RTC_MONTH_OFFS) |
+		(bin2bcd(tm->tm_year - 100) << RTC_YEAR_OFFS);
+	writel(rtc_reg, ioaddr + RTC_DATE_REG_OFFS);
+
+	return 0;
+}
+
+static int mv_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+	void __iomem *ioaddr = pdata->ioaddr;
+	u32	rtc_time, rtc_date;
+	unsigned int year, month, day, hour, minute, second, wday;
+
+	rtc_time = readl(ioaddr + RTC_TIME_REG_OFFS);
+	rtc_date = readl(ioaddr + RTC_DATE_REG_OFFS);
+
+	second = rtc_time & 0x7f;
+	minute = (rtc_time >> RTC_MINUTES_OFFS) & 0x7f;
+	hour = (rtc_time >> RTC_HOURS_OFFS) & 0x3f; /* assume 24 hour mode */
+	wday = (rtc_time >> RTC_WDAY_OFFS) & 0x7;
+
+	day = rtc_date & 0x3f;
+	month = (rtc_date >> RTC_MONTH_OFFS) & 0x3f;
+	year = (rtc_date >> RTC_YEAR_OFFS) & 0xff;
+
+	tm->tm_sec = bcd2bin(second);
+	tm->tm_min = bcd2bin(minute);
+	tm->tm_hour = bcd2bin(hour);
+	tm->tm_mday = bcd2bin(day);
+	tm->tm_wday = bcd2bin(wday);
+	tm->tm_mon = bcd2bin(month) - 1;
+	/* hw counts from year 2000, but tm_year is relative to 1900 */
+	tm->tm_year = bcd2bin(year) + 100;
+
+	return 0;
+}
+
+static int mv_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+	void __iomem *ioaddr = pdata->ioaddr;
+	u32	rtc_time, rtc_date;
+	unsigned int year, month, day, hour, minute, second, wday;
+
+	rtc_time = readl(ioaddr + RTC_ALARM_TIME_REG_OFFS);
+	rtc_date = readl(ioaddr + RTC_ALARM_DATE_REG_OFFS);
+
+	second = rtc_time & 0x7f;
+	minute = (rtc_time >> RTC_MINUTES_OFFS) & 0x7f;
+	hour = (rtc_time >> RTC_HOURS_OFFS) & 0x3f; /* assume 24 hour mode */
+	wday = (rtc_time >> RTC_WDAY_OFFS) & 0x7;
+
+	day = rtc_date & 0x3f;
+	month = (rtc_date >> RTC_MONTH_OFFS) & 0x3f;
+	year = (rtc_date >> RTC_YEAR_OFFS) & 0xff;
+
+	alm->time.tm_sec = bcd2bin(second);
+	alm->time.tm_min = bcd2bin(minute);
+	alm->time.tm_hour = bcd2bin(hour);
+	alm->time.tm_mday = bcd2bin(day);
+	alm->time.tm_wday = bcd2bin(wday);
+	alm->time.tm_mon = bcd2bin(month) - 1;
+	/* hw counts from year 2000, but tm_year is relative to 1900 */
+	alm->time.tm_year = bcd2bin(year) + 100;
+
+	alm->enabled = !!readl(ioaddr + RTC_ALARM_INTERRUPT_MASK_REG_OFFS);
+
+	return rtc_valid_tm(&alm->time);
+}
+
+static int mv_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+	void __iomem *ioaddr = pdata->ioaddr;
+	u32 rtc_reg = 0;
+
+	if (alm->time.tm_sec >= 0)
+		rtc_reg |= (RTC_ALARM_VALID | bin2bcd(alm->time.tm_sec))
+			<< RTC_SECONDS_OFFS;
+	if (alm->time.tm_min >= 0)
+		rtc_reg |= (RTC_ALARM_VALID | bin2bcd(alm->time.tm_min))
+			<< RTC_MINUTES_OFFS;
+	if (alm->time.tm_hour >= 0)
+		rtc_reg |= (RTC_ALARM_VALID | bin2bcd(alm->time.tm_hour))
+			<< RTC_HOURS_OFFS;
+
+	writel(rtc_reg, ioaddr + RTC_ALARM_TIME_REG_OFFS);
+
+	if (alm->time.tm_mday >= 0)
+		rtc_reg = (RTC_ALARM_VALID | bin2bcd(alm->time.tm_mday))
+			<< RTC_MDAY_OFFS;
+	else
+		rtc_reg = 0;
+
+	if (alm->time.tm_mon >= 0)
+		rtc_reg |= (RTC_ALARM_VALID | bin2bcd(alm->time.tm_mon + 1))
+			<< RTC_MONTH_OFFS;
+
+	if (alm->time.tm_year >= 0)
+		rtc_reg |= (RTC_ALARM_VALID | bin2bcd(alm->time.tm_year - 100))
+			<< RTC_YEAR_OFFS;
+
+	writel(rtc_reg, ioaddr + RTC_ALARM_DATE_REG_OFFS);
+	writel(0, ioaddr + RTC_ALARM_INTERRUPT_CASUE_REG_OFFS);
+	writel(alm->enabled ? 1 : 0,
+	       ioaddr + RTC_ALARM_INTERRUPT_MASK_REG_OFFS);
+
+	return 0;
+}
+
+static int mv_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+	void __iomem *ioaddr = pdata->ioaddr;
+
+	if (pdata->irq < 0)
+		return -EINVAL; /* fall back into rtc-dev's emulation */
+
+	if (enabled)
+		writel(1, ioaddr + RTC_ALARM_INTERRUPT_MASK_REG_OFFS);
+	else
+		writel(0, ioaddr + RTC_ALARM_INTERRUPT_MASK_REG_OFFS);
+	return 0;
+}
+
+static irqreturn_t mv_rtc_interrupt(int irq, void *data)
+{
+	struct rtc_plat_data *pdata = data;
+	void __iomem *ioaddr = pdata->ioaddr;
+
+	/* alarm irq? */
+	if (!readl(ioaddr + RTC_ALARM_INTERRUPT_CASUE_REG_OFFS))
+		return IRQ_NONE;
+
+	/* clear interrupt */
+	writel(0, ioaddr + RTC_ALARM_INTERRUPT_CASUE_REG_OFFS);
+	rtc_update_irq(pdata->rtc, 1, RTC_IRQF | RTC_AF);
+	return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops mv_rtc_ops = {
+	.read_time	= mv_rtc_read_time,
+	.set_time	= mv_rtc_set_time,
+	.read_alarm	= mv_rtc_read_alarm,
+	.set_alarm	= mv_rtc_set_alarm,
+	.alarm_irq_enable = mv_rtc_alarm_irq_enable,
+};
+
+static int __init mv_rtc_probe(struct platform_device *pdev)
+{
+	struct rtc_plat_data *pdata;
+	u32 rtc_time;
+	int ret = 0;
+
+	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
+	if (!pdata)
+		return -ENOMEM;
+
+	pdata->ioaddr = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(pdata->ioaddr))
+		return PTR_ERR(pdata->ioaddr);
+
+	pdata->clk = devm_clk_get_optional_prepared(&pdev->dev, NULL);
+	if (IS_ERR(pdata->clk))
+		return PTR_ERR(pdata->clk);
+
+	/* make sure the 24 hour mode is enabled */
+	rtc_time = readl(pdata->ioaddr + RTC_TIME_REG_OFFS);
+	if (rtc_time & RTC_HOURS_12H_MODE) {
+		dev_err(&pdev->dev, "12 Hour mode is enabled but not supported.\n");
+		return  -EINVAL;
+	}
+
+	/* make sure it is actually functional */
+	if (rtc_time == 0x01000000) {
+		ssleep(1);
+		rtc_time = readl(pdata->ioaddr + RTC_TIME_REG_OFFS);
+		if (rtc_time == 0x01000000) {
+			dev_err(&pdev->dev, "internal RTC not ticking\n");
+			return -ENODEV;
+		}
+	}
+
+	pdata->irq = platform_get_irq(pdev, 0);
+
+	platform_set_drvdata(pdev, pdata);
+
+	pdata->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(pdata->rtc)) {
+		return PTR_ERR(pdata->rtc);
+	}
+
+	if (pdata->irq >= 0) {
+		writel(0, pdata->ioaddr + RTC_ALARM_INTERRUPT_MASK_REG_OFFS);
+		if (devm_request_irq(&pdev->dev, pdata->irq, mv_rtc_interrupt,
+				     IRQF_SHARED,
+				     pdev->name, pdata) < 0) {
+			dev_warn(&pdev->dev, "interrupt not available.\n");
+			pdata->irq = -1;
+		}
+	}
+
+	if (pdata->irq >= 0)
+		devm_device_init_wakeup(&pdev->dev);
+	else
+		clear_bit(RTC_FEATURE_ALARM, pdata->rtc->features);
+
+	pdata->rtc->ops = &mv_rtc_ops;
+	pdata->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	pdata->rtc->range_max = RTC_TIMESTAMP_END_2099;
+
+	ret = devm_rtc_register_device(pdata->rtc);
+	if (!ret)
+		return 0;
+
+	return ret;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id rtc_mv_of_match_table[] = {
+	{ .compatible = "marvell,orion-rtc", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, rtc_mv_of_match_table);
+#endif
+
+#ifdef CONFIG_PM_SLEEP
+static int mv_rtc_suspend(struct device *dev)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev) && pdata->irq >= 0)
+		enable_irq_wake(pdata->irq);
+	return 0;
+}
+
+static int mv_rtc_resume(struct device *dev)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev) && pdata->irq >= 0)
+		disable_irq_wake(pdata->irq);
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(mv_rtc_pm_ops, mv_rtc_suspend, mv_rtc_resume);
+
+static struct platform_driver mv_rtc_driver = {
+	.driver		= {
+		.name	= "rtc-mv",
+		.of_match_table = of_match_ptr(rtc_mv_of_match_table),
+		.pm	= &mv_rtc_pm_ops,
+	},
+};
+
+module_platform_driver_probe(mv_rtc_driver, mv_rtc_probe);
+
+MODULE_AUTHOR("Saeed Bishara <saeed@marvell.com>");
+MODULE_DESCRIPTION("Marvell RTC driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:rtc-mv");