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, 431 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-loongson.c b/drivers/rtc/rtc-loongson.c
new file mode 100644
index 000000000..066f0644d
--- /dev/null
+++ b/drivers/rtc/rtc-loongson.c
@@ -0,0 +1,431 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Loongson RTC driver
+ *
+ * Maintained out-of-tree by Huacai Chen <chenhuacai@kernel.org>.
+ * Rewritten for mainline by WANG Xuerui <git@xen0n.name>.
+ *                           Binbin Zhou <zhoubinbin@loongson.cn>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/acpi.h>
+
+/* Time Of Year(TOY) counters registers */
+#define TOY_TRIM_REG		0x20 /* Must be initialized to 0 */
+#define TOY_WRITE0_REG		0x24 /* TOY low 32-bits value (write-only) */
+#define TOY_WRITE1_REG		0x28 /* TOY high 32-bits value (write-only) */
+#define TOY_READ0_REG		0x2c /* TOY low 32-bits value (read-only) */
+#define TOY_READ1_REG		0x30 /* TOY high 32-bits value (read-only) */
+#define TOY_MATCH0_REG		0x34 /* TOY timing interrupt 0 */
+#define TOY_MATCH1_REG		0x38 /* TOY timing interrupt 1 */
+#define TOY_MATCH2_REG		0x3c /* TOY timing interrupt 2 */
+
+/* RTC counters registers */
+#define RTC_CTRL_REG		0x40 /* TOY and RTC control register */
+#define RTC_TRIM_REG		0x60 /* Must be initialized to 0 */
+#define RTC_WRITE0_REG		0x64 /* RTC counters value (write-only) */
+#define RTC_READ0_REG		0x68 /* RTC counters value (read-only) */
+#define RTC_MATCH0_REG		0x6c /* RTC timing interrupt 0 */
+#define RTC_MATCH1_REG		0x70 /* RTC timing interrupt 1 */
+#define RTC_MATCH2_REG		0x74 /* RTC timing interrupt 2 */
+
+/* bitmask of TOY_WRITE0_REG */
+#define TOY_MON			GENMASK(31, 26)
+#define TOY_DAY			GENMASK(25, 21)
+#define TOY_HOUR		GENMASK(20, 16)
+#define TOY_MIN			GENMASK(15, 10)
+#define TOY_SEC			GENMASK(9, 4)
+#define TOY_MSEC		GENMASK(3, 0)
+
+/* bitmask of TOY_MATCH0/1/2_REG */
+#define TOY_MATCH_YEAR		GENMASK(31, 26)
+#define TOY_MATCH_MON		GENMASK(25, 22)
+#define TOY_MATCH_DAY		GENMASK(21, 17)
+#define TOY_MATCH_HOUR		GENMASK(16, 12)
+#define TOY_MATCH_MIN		GENMASK(11, 6)
+#define TOY_MATCH_SEC		GENMASK(5, 0)
+
+/* bitmask of RTC_CTRL_REG */
+#define RTC_ENABLE		BIT(13) /* 1: RTC counters enable */
+#define TOY_ENABLE		BIT(11) /* 1: TOY counters enable */
+#define OSC_ENABLE		BIT(8) /* 1: 32.768k crystal enable */
+#define TOY_ENABLE_MASK		(TOY_ENABLE | OSC_ENABLE)
+
+/* PM domain registers */
+#define PM1_STS_REG		0x0c	/* Power management 1 status register */
+#define RTC_STS			BIT(10)	/* RTC status */
+#define PM1_EN_REG		0x10	/* Power management 1 enable register */
+#define RTC_EN			BIT(10)	/* RTC event enable */
+
+/*
+ * According to the LS1C manual, RTC_CTRL and alarm-related registers are not defined.
+ * Accessing the relevant registers will cause the system to hang.
+ */
+#define LOONGSON_RTC_CTRL_WORKAROUND	BIT(0)
+#define LOONGSON_RTC_ALARM_WORKAROUND	BIT(1)
+
+struct loongson_rtc_config {
+	u32 pm_offset;	/* Offset of PM domain, for RTC alarm wakeup */
+	u32 flags;	/* Workaround bits */
+};
+
+struct loongson_rtc_priv {
+	spinlock_t lock;	/* protects PM registers access */
+	u32 fix_year;		/* RTC alarm year compensation value */
+	struct rtc_device *rtcdev;
+	struct regmap *regmap;
+	void __iomem *pm_base;	/* PM domain base, for RTC alarm wakeup */
+	const struct loongson_rtc_config *config;
+};
+
+static const struct loongson_rtc_config ls1b_rtc_config = {
+	.pm_offset = 0,
+	.flags = 0,
+};
+
+static const struct loongson_rtc_config ls1c_rtc_config = {
+	.pm_offset = 0,
+	.flags = LOONGSON_RTC_CTRL_WORKAROUND | LOONGSON_RTC_ALARM_WORKAROUND,
+};
+
+static const struct loongson_rtc_config generic_rtc_config = {
+	.pm_offset = 0x100,
+	.flags = 0,
+};
+
+static const struct loongson_rtc_config ls2k0300_rtc_config = {
+	.pm_offset = 0x0,
+	.flags = LOONGSON_RTC_ALARM_WORKAROUND,
+};
+
+static const struct loongson_rtc_config ls2k1000_rtc_config = {
+	.pm_offset = 0x800,
+	.flags = 0,
+};
+
+static const struct regmap_config loongson_rtc_regmap_config = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 4,
+};
+
+/* RTC alarm irq handler */
+static irqreturn_t loongson_rtc_isr(int irq, void *id)
+{
+	struct loongson_rtc_priv *priv = (struct loongson_rtc_priv *)id;
+
+	rtc_update_irq(priv->rtcdev, 1, RTC_AF | RTC_IRQF);
+
+	/*
+	 * The TOY_MATCH0_REG should be cleared 0 here,
+	 * otherwise the interrupt cannot be cleared.
+	 */
+	regmap_write(priv->regmap, TOY_MATCH0_REG, 0);
+
+	return IRQ_HANDLED;
+}
+
+/* For ACPI fixed event handler */
+static u32 loongson_rtc_handler(void *id)
+{
+	struct loongson_rtc_priv *priv = (struct loongson_rtc_priv *)id;
+
+	rtc_update_irq(priv->rtcdev, 1, RTC_AF | RTC_IRQF);
+
+	/*
+	 * The TOY_MATCH0_REG should be cleared 0 here,
+	 * otherwise the interrupt cannot be cleared.
+	 */
+	regmap_write(priv->regmap, TOY_MATCH0_REG, 0);
+
+	spin_lock(&priv->lock);
+	/* Disable RTC alarm wakeup and interrupt */
+	writel(readl(priv->pm_base + PM1_EN_REG) & ~RTC_EN,
+	       priv->pm_base + PM1_EN_REG);
+
+	/* Clear RTC interrupt status */
+	writel(RTC_STS, priv->pm_base + PM1_STS_REG);
+	spin_unlock(&priv->lock);
+
+	return ACPI_INTERRUPT_HANDLED;
+}
+
+static int loongson_rtc_set_enabled(struct device *dev)
+{
+	struct loongson_rtc_priv *priv = dev_get_drvdata(dev);
+
+	if (priv->config->flags & LOONGSON_RTC_CTRL_WORKAROUND)
+		return 0;
+
+	/* Enable RTC TOY counters and crystal */
+	return regmap_update_bits(priv->regmap, RTC_CTRL_REG, TOY_ENABLE_MASK,
+				  TOY_ENABLE_MASK);
+}
+
+static bool loongson_rtc_get_enabled(struct device *dev)
+{
+	int ret;
+	u32 ctrl_data;
+	struct loongson_rtc_priv *priv = dev_get_drvdata(dev);
+
+	if (priv->config->flags & LOONGSON_RTC_CTRL_WORKAROUND)
+		return true;
+
+	ret = regmap_read(priv->regmap, RTC_CTRL_REG, &ctrl_data);
+	if (ret < 0)
+		return false;
+
+	return ctrl_data & TOY_ENABLE_MASK;
+}
+
+static int loongson_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	int ret;
+	u32 rtc_data[2];
+	struct loongson_rtc_priv *priv = dev_get_drvdata(dev);
+
+	if (!loongson_rtc_get_enabled(dev))
+		return -EINVAL;
+
+	ret = regmap_bulk_read(priv->regmap, TOY_READ0_REG, rtc_data,
+			       ARRAY_SIZE(rtc_data));
+	if (ret < 0)
+		return ret;
+
+	tm->tm_sec = FIELD_GET(TOY_SEC, rtc_data[0]);
+	tm->tm_min = FIELD_GET(TOY_MIN, rtc_data[0]);
+	tm->tm_hour = FIELD_GET(TOY_HOUR, rtc_data[0]);
+	tm->tm_mday = FIELD_GET(TOY_DAY, rtc_data[0]);
+	tm->tm_mon = FIELD_GET(TOY_MON, rtc_data[0]) - 1;
+	tm->tm_year = rtc_data[1];
+
+	/* Prepare for RTC alarm year compensation value. */
+	priv->fix_year = tm->tm_year / 64 * 64;
+	return 0;
+}
+
+static int loongson_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	int ret;
+	u32 rtc_data[2];
+	struct loongson_rtc_priv *priv = dev_get_drvdata(dev);
+
+	rtc_data[0] = FIELD_PREP(TOY_SEC, tm->tm_sec)
+		    | FIELD_PREP(TOY_MIN, tm->tm_min)
+		    | FIELD_PREP(TOY_HOUR, tm->tm_hour)
+		    | FIELD_PREP(TOY_DAY, tm->tm_mday)
+		    | FIELD_PREP(TOY_MON, tm->tm_mon + 1);
+	rtc_data[1] = tm->tm_year;
+
+	ret = regmap_bulk_write(priv->regmap, TOY_WRITE0_REG, rtc_data,
+				ARRAY_SIZE(rtc_data));
+	if (ret < 0)
+		return ret;
+
+	return loongson_rtc_set_enabled(dev);
+}
+
+static int loongson_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	int ret;
+	u32 alarm_data;
+	struct loongson_rtc_priv *priv = dev_get_drvdata(dev);
+
+	ret = regmap_read(priv->regmap, TOY_MATCH0_REG, &alarm_data);
+	if (ret < 0)
+		return ret;
+
+	alrm->time.tm_sec = FIELD_GET(TOY_MATCH_SEC, alarm_data);
+	alrm->time.tm_min = FIELD_GET(TOY_MATCH_MIN, alarm_data);
+	alrm->time.tm_hour = FIELD_GET(TOY_MATCH_HOUR, alarm_data);
+	alrm->time.tm_mday = FIELD_GET(TOY_MATCH_DAY, alarm_data);
+	alrm->time.tm_mon = FIELD_GET(TOY_MATCH_MON, alarm_data) - 1;
+	/*
+	 * This is a hardware bug: the year field of SYS_TOYMATCH is only 6 bits,
+	 * making it impossible to save year values larger than 64.
+	 *
+	 * SYS_TOYMATCH is used to match the alarm time value and determine if
+	 * an alarm is triggered, so we must keep the lower 6 bits of the year
+	 * value constant during the value conversion.
+	 *
+	 * In summary, we need to manually add 64(or a multiple of 64) to the
+	 * year value to avoid the invalid alarm prompt at startup.
+	 */
+	alrm->time.tm_year = FIELD_GET(TOY_MATCH_YEAR, alarm_data) + priv->fix_year;
+
+	alrm->enabled = !!(readl(priv->pm_base + PM1_EN_REG) & RTC_EN);
+	return 0;
+}
+
+static int loongson_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	u32 val;
+	struct loongson_rtc_priv *priv = dev_get_drvdata(dev);
+
+	spin_lock(&priv->lock);
+	val = readl(priv->pm_base + PM1_EN_REG);
+	/* Enable RTC alarm wakeup */
+	writel(enabled ? val | RTC_EN : val & ~RTC_EN,
+	       priv->pm_base + PM1_EN_REG);
+	spin_unlock(&priv->lock);
+
+	return 0;
+}
+
+static int loongson_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	int ret;
+	u32 alarm_data;
+	struct loongson_rtc_priv *priv = dev_get_drvdata(dev);
+
+	alarm_data = FIELD_PREP(TOY_MATCH_SEC, alrm->time.tm_sec)
+		   | FIELD_PREP(TOY_MATCH_MIN, alrm->time.tm_min)
+		   | FIELD_PREP(TOY_MATCH_HOUR, alrm->time.tm_hour)
+		   | FIELD_PREP(TOY_MATCH_DAY, alrm->time.tm_mday)
+		   | FIELD_PREP(TOY_MATCH_MON, alrm->time.tm_mon + 1)
+		   | FIELD_PREP(TOY_MATCH_YEAR, alrm->time.tm_year - priv->fix_year);
+
+	ret = regmap_write(priv->regmap, TOY_MATCH0_REG, alarm_data);
+	if (ret < 0)
+		return ret;
+
+	return loongson_rtc_alarm_irq_enable(dev, alrm->enabled);
+}
+
+static const struct rtc_class_ops loongson_rtc_ops = {
+	.read_time = loongson_rtc_read_time,
+	.set_time = loongson_rtc_set_time,
+	.read_alarm = loongson_rtc_read_alarm,
+	.set_alarm = loongson_rtc_set_alarm,
+	.alarm_irq_enable = loongson_rtc_alarm_irq_enable,
+};
+
+static int loongson_rtc_alarm_setting(struct platform_device *pdev, void __iomem *regs)
+{
+	int ret = 0, alarm_irq;
+	struct device *dev = &pdev->dev;
+	struct loongson_rtc_priv *priv = dev_get_drvdata(dev);
+
+	if (priv->config->flags & LOONGSON_RTC_ALARM_WORKAROUND) {
+		/* Loongson-1C/Loongson-2K0300 RTC does not support alarm */
+		clear_bit(RTC_FEATURE_ALARM, priv->rtcdev->features);
+		return 0;
+	}
+
+	/* Get RTC alarm irq */
+	alarm_irq = platform_get_irq(pdev, 0);
+	if (alarm_irq < 0)
+		return alarm_irq;
+
+	ret = devm_request_irq(dev, alarm_irq, loongson_rtc_isr, 0, "loongson-alarm",
+			       priv);
+	if (ret < 0)
+		return ret;
+
+	priv->pm_base = regs - priv->config->pm_offset;
+	device_init_wakeup(dev, true);
+
+	if (has_acpi_companion(dev))
+		acpi_install_fixed_event_handler(ACPI_EVENT_RTC,
+						 loongson_rtc_handler, priv);
+
+	return ret;
+}
+
+static int loongson_rtc_probe(struct platform_device *pdev)
+{
+	int ret;
+	void __iomem *regs;
+	struct loongson_rtc_priv *priv;
+	struct device *dev = &pdev->dev;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	regs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(regs))
+		return dev_err_probe(dev, PTR_ERR(regs),
+				     "devm_platform_ioremap_resource failed\n");
+
+	priv->regmap = devm_regmap_init_mmio(dev, regs,
+					     &loongson_rtc_regmap_config);
+	if (IS_ERR(priv->regmap))
+		return dev_err_probe(dev, PTR_ERR(priv->regmap),
+				     "devm_regmap_init_mmio failed\n");
+
+	priv->config = device_get_match_data(dev);
+	spin_lock_init(&priv->lock);
+	platform_set_drvdata(pdev, priv);
+
+	priv->rtcdev = devm_rtc_allocate_device(dev);
+	if (IS_ERR(priv->rtcdev))
+		return dev_err_probe(dev, PTR_ERR(priv->rtcdev),
+				     "devm_rtc_allocate_device failed\n");
+
+	ret = loongson_rtc_alarm_setting(pdev, regs);
+	if (ret)
+		return ret;
+
+	/* Loongson RTC does not support UIE */
+	clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, priv->rtcdev->features);
+	priv->rtcdev->ops = &loongson_rtc_ops;
+	priv->rtcdev->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	priv->rtcdev->range_max = RTC_TIMESTAMP_END_2099;
+
+	return devm_rtc_register_device(priv->rtcdev);
+}
+
+static void loongson_rtc_remove(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct loongson_rtc_priv *priv = dev_get_drvdata(dev);
+
+	if (!test_bit(RTC_FEATURE_ALARM, priv->rtcdev->features))
+		return;
+
+	if (has_acpi_companion(dev))
+		acpi_remove_fixed_event_handler(ACPI_EVENT_RTC,
+						loongson_rtc_handler);
+
+	device_init_wakeup(dev, false);
+	loongson_rtc_alarm_irq_enable(dev, 0);
+}
+
+static const struct of_device_id loongson_rtc_of_match[] = {
+	{ .compatible = "loongson,ls1b-rtc", .data = &ls1b_rtc_config },
+	{ .compatible = "loongson,ls1c-rtc", .data = &ls1c_rtc_config },
+	{ .compatible = "loongson,ls7a-rtc", .data = &generic_rtc_config },
+	{ .compatible = "loongson,ls2k0300-rtc", .data = &ls2k0300_rtc_config },
+	{ .compatible = "loongson,ls2k1000-rtc", .data = &ls2k1000_rtc_config },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, loongson_rtc_of_match);
+
+static const struct acpi_device_id loongson_rtc_acpi_match[] = {
+	{ "LOON0001", .driver_data = (kernel_ulong_t)&generic_rtc_config },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, loongson_rtc_acpi_match);
+
+static struct platform_driver loongson_rtc_driver = {
+	.probe		= loongson_rtc_probe,
+	.remove		= loongson_rtc_remove,
+	.driver		= {
+		.name	= "loongson-rtc",
+		.of_match_table = loongson_rtc_of_match,
+		.acpi_match_table = loongson_rtc_acpi_match,
+	},
+};
+module_platform_driver(loongson_rtc_driver);
+
+MODULE_DESCRIPTION("Loongson RTC driver");
+MODULE_AUTHOR("Binbin Zhou <zhoubinbin@loongson.cn>");
+MODULE_AUTHOR("WANG Xuerui <git@xen0n.name>");
+MODULE_AUTHOR("Huacai Chen <chenhuacai@kernel.org>");
+MODULE_LICENSE("GPL");