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, 362 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-palmas.c b/drivers/rtc/rtc-palmas.c
new file mode 100644
index 000000000..aecada6bc
--- /dev/null
+++ b/drivers/rtc/rtc-palmas.c
@@ -0,0 +1,362 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * rtc-palmas.c -- Palmas Real Time Clock driver.
+
+ * RTC driver for TI Palma series devices like TPS65913,
+ * TPS65914 power management IC.
+ *
+ * Copyright (c) 2012, NVIDIA Corporation.
+ *
+ * Author: Laxman Dewangan <ldewangan@nvidia.com>
+ */
+
+#include <linux/bcd.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/mfd/palmas.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/rtc.h>
+#include <linux/types.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+
+struct palmas_rtc {
+	struct rtc_device	*rtc;
+	struct device		*dev;
+	unsigned int		irq;
+};
+
+/* Total number of RTC registers needed to set time*/
+#define PALMAS_NUM_TIME_REGS	(PALMAS_YEARS_REG - PALMAS_SECONDS_REG + 1)
+
+static int palmas_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	unsigned char rtc_data[PALMAS_NUM_TIME_REGS];
+	struct palmas *palmas = dev_get_drvdata(dev->parent);
+	int ret;
+
+	/* Copy RTC counting registers to static registers or latches */
+	ret = palmas_update_bits(palmas, PALMAS_RTC_BASE, PALMAS_RTC_CTRL_REG,
+		PALMAS_RTC_CTRL_REG_GET_TIME, PALMAS_RTC_CTRL_REG_GET_TIME);
+	if (ret < 0) {
+		dev_err(dev, "RTC CTRL reg update failed, err: %d\n", ret);
+		return ret;
+	}
+
+	ret = palmas_bulk_read(palmas, PALMAS_RTC_BASE, PALMAS_SECONDS_REG,
+			rtc_data, PALMAS_NUM_TIME_REGS);
+	if (ret < 0) {
+		dev_err(dev, "RTC_SECONDS reg read failed, err = %d\n", ret);
+		return ret;
+	}
+
+	tm->tm_sec = bcd2bin(rtc_data[0]);
+	tm->tm_min = bcd2bin(rtc_data[1]);
+	tm->tm_hour = bcd2bin(rtc_data[2]);
+	tm->tm_mday = bcd2bin(rtc_data[3]);
+	tm->tm_mon = bcd2bin(rtc_data[4]) - 1;
+	tm->tm_year = bcd2bin(rtc_data[5]) + 100;
+
+	return ret;
+}
+
+static int palmas_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	unsigned char rtc_data[PALMAS_NUM_TIME_REGS];
+	struct palmas *palmas = dev_get_drvdata(dev->parent);
+	int ret;
+
+	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);
+
+	/* Stop RTC while updating the RTC time registers */
+	ret = palmas_update_bits(palmas, PALMAS_RTC_BASE, PALMAS_RTC_CTRL_REG,
+		PALMAS_RTC_CTRL_REG_STOP_RTC, 0);
+	if (ret < 0) {
+		dev_err(dev, "RTC stop failed, err = %d\n", ret);
+		return ret;
+	}
+
+	ret = palmas_bulk_write(palmas, PALMAS_RTC_BASE, PALMAS_SECONDS_REG,
+		rtc_data, PALMAS_NUM_TIME_REGS);
+	if (ret < 0) {
+		dev_err(dev, "RTC_SECONDS reg write failed, err = %d\n", ret);
+		return ret;
+	}
+
+	/* Start back RTC */
+	ret = palmas_update_bits(palmas, PALMAS_RTC_BASE, PALMAS_RTC_CTRL_REG,
+		PALMAS_RTC_CTRL_REG_STOP_RTC, PALMAS_RTC_CTRL_REG_STOP_RTC);
+	if (ret < 0)
+		dev_err(dev, "RTC start failed, err = %d\n", ret);
+	return ret;
+}
+
+static int palmas_rtc_alarm_irq_enable(struct device *dev, unsigned enabled)
+{
+	struct palmas *palmas = dev_get_drvdata(dev->parent);
+	u8 val;
+
+	val = enabled ? PALMAS_RTC_INTERRUPTS_REG_IT_ALARM : 0;
+	return palmas_write(palmas, PALMAS_RTC_BASE,
+		PALMAS_RTC_INTERRUPTS_REG, val);
+}
+
+static int palmas_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	unsigned char alarm_data[PALMAS_NUM_TIME_REGS];
+	u32 int_val;
+	struct palmas *palmas = dev_get_drvdata(dev->parent);
+	int ret;
+
+	ret = palmas_bulk_read(palmas, PALMAS_RTC_BASE,
+			PALMAS_ALARM_SECONDS_REG,
+			alarm_data, PALMAS_NUM_TIME_REGS);
+	if (ret < 0) {
+		dev_err(dev, "RTC_ALARM_SECONDS read failed, err = %d\n", ret);
+		return ret;
+	}
+
+	alm->time.tm_sec = bcd2bin(alarm_data[0]);
+	alm->time.tm_min = bcd2bin(alarm_data[1]);
+	alm->time.tm_hour = bcd2bin(alarm_data[2]);
+	alm->time.tm_mday = bcd2bin(alarm_data[3]);
+	alm->time.tm_mon = bcd2bin(alarm_data[4]) - 1;
+	alm->time.tm_year = bcd2bin(alarm_data[5]) + 100;
+
+	ret = palmas_read(palmas, PALMAS_RTC_BASE, PALMAS_RTC_INTERRUPTS_REG,
+			&int_val);
+	if (ret < 0) {
+		dev_err(dev, "RTC_INTERRUPTS reg read failed, err = %d\n", ret);
+		return ret;
+	}
+
+	if (int_val & PALMAS_RTC_INTERRUPTS_REG_IT_ALARM)
+		alm->enabled = 1;
+	return ret;
+}
+
+static int palmas_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	unsigned char alarm_data[PALMAS_NUM_TIME_REGS];
+	struct palmas *palmas = dev_get_drvdata(dev->parent);
+	int ret;
+
+	ret = palmas_rtc_alarm_irq_enable(dev, 0);
+	if (ret < 0) {
+		dev_err(dev, "Disable RTC alarm failed\n");
+		return ret;
+	}
+
+	alarm_data[0] = bin2bcd(alm->time.tm_sec);
+	alarm_data[1] = bin2bcd(alm->time.tm_min);
+	alarm_data[2] = bin2bcd(alm->time.tm_hour);
+	alarm_data[3] = bin2bcd(alm->time.tm_mday);
+	alarm_data[4] = bin2bcd(alm->time.tm_mon + 1);
+	alarm_data[5] = bin2bcd(alm->time.tm_year - 100);
+
+	ret = palmas_bulk_write(palmas, PALMAS_RTC_BASE,
+		PALMAS_ALARM_SECONDS_REG, alarm_data, PALMAS_NUM_TIME_REGS);
+	if (ret < 0) {
+		dev_err(dev, "ALARM_SECONDS_REG write failed, err = %d\n", ret);
+		return ret;
+	}
+
+	if (alm->enabled)
+		ret = palmas_rtc_alarm_irq_enable(dev, 1);
+	return ret;
+}
+
+static int palmas_clear_interrupts(struct device *dev)
+{
+	struct palmas *palmas = dev_get_drvdata(dev->parent);
+	unsigned int rtc_reg;
+	int ret;
+
+	ret = palmas_read(palmas, PALMAS_RTC_BASE, PALMAS_RTC_STATUS_REG,
+				&rtc_reg);
+	if (ret < 0) {
+		dev_err(dev, "RTC_STATUS read failed, err = %d\n", ret);
+		return ret;
+	}
+
+	ret = palmas_write(palmas, PALMAS_RTC_BASE, PALMAS_RTC_STATUS_REG,
+			rtc_reg);
+	if (ret < 0) {
+		dev_err(dev, "RTC_STATUS write failed, err = %d\n", ret);
+		return ret;
+	}
+	return 0;
+}
+
+static irqreturn_t palmas_rtc_interrupt(int irq, void *context)
+{
+	struct palmas_rtc *palmas_rtc = context;
+	struct device *dev = palmas_rtc->dev;
+	int ret;
+
+	ret = palmas_clear_interrupts(dev);
+	if (ret < 0) {
+		dev_err(dev, "RTC interrupt clear failed, err = %d\n", ret);
+		return IRQ_NONE;
+	}
+
+	rtc_update_irq(palmas_rtc->rtc, 1, RTC_IRQF | RTC_AF);
+	return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops palmas_rtc_ops = {
+	.read_time	= palmas_rtc_read_time,
+	.set_time	= palmas_rtc_set_time,
+	.read_alarm	= palmas_rtc_read_alarm,
+	.set_alarm	= palmas_rtc_set_alarm,
+	.alarm_irq_enable = palmas_rtc_alarm_irq_enable,
+};
+
+static int palmas_rtc_probe(struct platform_device *pdev)
+{
+	struct palmas *palmas = dev_get_drvdata(pdev->dev.parent);
+	struct palmas_rtc *palmas_rtc = NULL;
+	int ret;
+	bool enable_bb_charging = false;
+	bool high_bb_charging = false;
+
+	if (pdev->dev.of_node) {
+		enable_bb_charging = of_property_read_bool(pdev->dev.of_node,
+					"ti,backup-battery-chargeable");
+		high_bb_charging = of_property_read_bool(pdev->dev.of_node,
+					"ti,backup-battery-charge-high-current");
+	}
+
+	palmas_rtc = devm_kzalloc(&pdev->dev, sizeof(struct palmas_rtc),
+			GFP_KERNEL);
+	if (!palmas_rtc)
+		return -ENOMEM;
+
+	/* Clear pending interrupts */
+	ret = palmas_clear_interrupts(&pdev->dev);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "clear RTC int failed, err = %d\n", ret);
+		return ret;
+	}
+
+	palmas_rtc->dev = &pdev->dev;
+	platform_set_drvdata(pdev, palmas_rtc);
+
+	if (enable_bb_charging) {
+		unsigned reg = PALMAS_BACKUP_BATTERY_CTRL_BBS_BBC_LOW_ICHRG;
+
+		if (high_bb_charging)
+			reg = 0;
+
+		ret = palmas_update_bits(palmas, PALMAS_PMU_CONTROL_BASE,
+			PALMAS_BACKUP_BATTERY_CTRL,
+			PALMAS_BACKUP_BATTERY_CTRL_BBS_BBC_LOW_ICHRG, reg);
+		if (ret < 0) {
+			dev_err(&pdev->dev,
+				"BACKUP_BATTERY_CTRL update failed, %d\n", ret);
+			return ret;
+		}
+
+		ret = palmas_update_bits(palmas, PALMAS_PMU_CONTROL_BASE,
+			PALMAS_BACKUP_BATTERY_CTRL,
+			PALMAS_BACKUP_BATTERY_CTRL_BB_CHG_EN,
+			PALMAS_BACKUP_BATTERY_CTRL_BB_CHG_EN);
+		if (ret < 0) {
+			dev_err(&pdev->dev,
+				"BACKUP_BATTERY_CTRL update failed, %d\n", ret);
+			return ret;
+		}
+	}
+
+	/* Start RTC */
+	ret = palmas_update_bits(palmas, PALMAS_RTC_BASE, PALMAS_RTC_CTRL_REG,
+			PALMAS_RTC_CTRL_REG_STOP_RTC,
+			PALMAS_RTC_CTRL_REG_STOP_RTC);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "RTC_CTRL write failed, err = %d\n", ret);
+		return ret;
+	}
+
+	palmas_rtc->irq = platform_get_irq(pdev, 0);
+
+	device_init_wakeup(&pdev->dev, true);
+	palmas_rtc->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
+				&palmas_rtc_ops, THIS_MODULE);
+	if (IS_ERR(palmas_rtc->rtc)) {
+		ret = PTR_ERR(palmas_rtc->rtc);
+		dev_err(&pdev->dev, "RTC register failed, err = %d\n", ret);
+		return ret;
+	}
+
+	ret = devm_request_threaded_irq(&pdev->dev, palmas_rtc->irq, NULL,
+			palmas_rtc_interrupt,
+			IRQF_TRIGGER_LOW | IRQF_ONESHOT,
+			dev_name(&pdev->dev), palmas_rtc);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "IRQ request failed, err = %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void palmas_rtc_remove(struct platform_device *pdev)
+{
+	palmas_rtc_alarm_irq_enable(&pdev->dev, 0);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int palmas_rtc_suspend(struct device *dev)
+{
+	struct palmas_rtc *palmas_rtc = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		enable_irq_wake(palmas_rtc->irq);
+	return 0;
+}
+
+static int palmas_rtc_resume(struct device *dev)
+{
+	struct palmas_rtc *palmas_rtc = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		disable_irq_wake(palmas_rtc->irq);
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(palmas_rtc_pm_ops, palmas_rtc_suspend,
+			 palmas_rtc_resume);
+
+#ifdef CONFIG_OF
+static const struct of_device_id of_palmas_rtc_match[] = {
+	{ .compatible = "ti,palmas-rtc"},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, of_palmas_rtc_match);
+#endif
+
+static struct platform_driver palmas_rtc_driver = {
+	.probe		= palmas_rtc_probe,
+	.remove		= palmas_rtc_remove,
+	.driver		= {
+		.name	= "palmas-rtc",
+		.pm	= &palmas_rtc_pm_ops,
+		.of_match_table = of_match_ptr(of_palmas_rtc_match),
+	},
+};
+
+module_platform_driver(palmas_rtc_driver);
+
+MODULE_ALIAS("platform:palmas_rtc");
+MODULE_DESCRIPTION("TI PALMAS series RTC driver");
+MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
+MODULE_LICENSE("GPL v2");