From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions 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) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- drivers/rtc/rtc-max8925.c | 322 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 322 insertions(+) create mode 100644 drivers/rtc/rtc-max8925.c (limited to 'drivers/rtc/rtc-max8925.c') diff --git a/drivers/rtc/rtc-max8925.c b/drivers/rtc/rtc-max8925.c new file mode 100644 index 000000000..6ce8afbea --- /dev/null +++ b/drivers/rtc/rtc-max8925.c @@ -0,0 +1,322 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * RTC driver for Maxim MAX8925 + * + * Copyright (C) 2009-2010 Marvell International Ltd. + * Haojian Zhuang + */ + +#include +#include +#include +#include +#include +#include + +enum { + RTC_SEC = 0, + RTC_MIN, + RTC_HOUR, + RTC_WEEKDAY, + RTC_DATE, + RTC_MONTH, + RTC_YEAR1, + RTC_YEAR2, +}; + +#define MAX8925_RTC_SEC 0x00 +#define MAX8925_RTC_MIN 0x01 +#define MAX8925_RTC_HOUR 0x02 +#define MAX8925_RTC_WEEKDAY 0x03 +#define MAX8925_RTC_DATE 0x04 +#define MAX8925_RTC_MONTH 0x05 +#define MAX8925_RTC_YEAR1 0x06 +#define MAX8925_RTC_YEAR2 0x07 +#define MAX8925_ALARM0_SEC 0x08 +#define MAX8925_ALARM0_MIN 0x09 +#define MAX8925_ALARM0_HOUR 0x0a +#define MAX8925_ALARM0_WEEKDAY 0x0b +#define MAX8925_ALARM0_DATE 0x0c +#define MAX8925_ALARM0_MON 0x0d +#define MAX8925_ALARM0_YEAR1 0x0e +#define MAX8925_ALARM0_YEAR2 0x0f +#define MAX8925_ALARM1_SEC 0x10 +#define MAX8925_ALARM1_MIN 0x11 +#define MAX8925_ALARM1_HOUR 0x12 +#define MAX8925_ALARM1_WEEKDAY 0x13 +#define MAX8925_ALARM1_DATE 0x14 +#define MAX8925_ALARM1_MON 0x15 +#define MAX8925_ALARM1_YEAR1 0x16 +#define MAX8925_ALARM1_YEAR2 0x17 +#define MAX8925_RTC_CNTL 0x1b +#define MAX8925_RTC_STATUS 0x20 + +#define TIME_NUM 8 +#define ALARM_1SEC (1 << 7) +#define HOUR_12 (1 << 7) +#define HOUR_AM_PM (1 << 5) +#define ALARM0_IRQ (1 << 3) +#define ALARM1_IRQ (1 << 2) +#define ALARM0_STATUS (1 << 2) +#define ALARM1_STATUS (1 << 1) + + +struct max8925_rtc_info { + struct rtc_device *rtc_dev; + struct max8925_chip *chip; + struct i2c_client *rtc; + struct device *dev; + int irq; +}; + +static irqreturn_t rtc_update_handler(int irq, void *data) +{ + struct max8925_rtc_info *info = (struct max8925_rtc_info *)data; + + /* disable ALARM0 except for 1SEC alarm */ + max8925_set_bits(info->rtc, MAX8925_ALARM0_CNTL, 0x7f, 0); + rtc_update_irq(info->rtc_dev, 1, RTC_IRQF | RTC_AF); + return IRQ_HANDLED; +} + +static int tm_calc(struct rtc_time *tm, unsigned char *buf, int len) +{ + if (len < TIME_NUM) + return -EINVAL; + tm->tm_year = (buf[RTC_YEAR2] >> 4) * 1000 + + (buf[RTC_YEAR2] & 0xf) * 100 + + (buf[RTC_YEAR1] >> 4) * 10 + + (buf[RTC_YEAR1] & 0xf); + tm->tm_year -= 1900; + tm->tm_mon = ((buf[RTC_MONTH] >> 4) & 0x01) * 10 + + (buf[RTC_MONTH] & 0x0f); + tm->tm_mday = ((buf[RTC_DATE] >> 4) & 0x03) * 10 + + (buf[RTC_DATE] & 0x0f); + tm->tm_wday = buf[RTC_WEEKDAY] & 0x07; + if (buf[RTC_HOUR] & HOUR_12) { + tm->tm_hour = ((buf[RTC_HOUR] >> 4) & 0x1) * 10 + + (buf[RTC_HOUR] & 0x0f); + if (buf[RTC_HOUR] & HOUR_AM_PM) + tm->tm_hour += 12; + } else + tm->tm_hour = ((buf[RTC_HOUR] >> 4) & 0x03) * 10 + + (buf[RTC_HOUR] & 0x0f); + tm->tm_min = ((buf[RTC_MIN] >> 4) & 0x7) * 10 + + (buf[RTC_MIN] & 0x0f); + tm->tm_sec = ((buf[RTC_SEC] >> 4) & 0x7) * 10 + + (buf[RTC_SEC] & 0x0f); + return 0; +} + +static int data_calc(unsigned char *buf, struct rtc_time *tm, int len) +{ + unsigned char high, low; + + if (len < TIME_NUM) + return -EINVAL; + + high = (tm->tm_year + 1900) / 1000; + low = (tm->tm_year + 1900) / 100; + low = low - high * 10; + buf[RTC_YEAR2] = (high << 4) + low; + high = (tm->tm_year + 1900) / 10; + low = tm->tm_year + 1900; + low = low - high * 10; + high = high - (high / 10) * 10; + buf[RTC_YEAR1] = (high << 4) + low; + high = tm->tm_mon / 10; + low = tm->tm_mon; + low = low - high * 10; + buf[RTC_MONTH] = (high << 4) + low; + high = tm->tm_mday / 10; + low = tm->tm_mday; + low = low - high * 10; + buf[RTC_DATE] = (high << 4) + low; + buf[RTC_WEEKDAY] = tm->tm_wday; + high = tm->tm_hour / 10; + low = tm->tm_hour; + low = low - high * 10; + buf[RTC_HOUR] = (high << 4) + low; + high = tm->tm_min / 10; + low = tm->tm_min; + low = low - high * 10; + buf[RTC_MIN] = (high << 4) + low; + high = tm->tm_sec / 10; + low = tm->tm_sec; + low = low - high * 10; + buf[RTC_SEC] = (high << 4) + low; + return 0; +} + +static int max8925_rtc_read_time(struct device *dev, struct rtc_time *tm) +{ + struct max8925_rtc_info *info = dev_get_drvdata(dev); + unsigned char buf[TIME_NUM]; + int ret; + + ret = max8925_bulk_read(info->rtc, MAX8925_RTC_SEC, TIME_NUM, buf); + if (ret < 0) + goto out; + ret = tm_calc(tm, buf, TIME_NUM); +out: + return ret; +} + +static int max8925_rtc_set_time(struct device *dev, struct rtc_time *tm) +{ + struct max8925_rtc_info *info = dev_get_drvdata(dev); + unsigned char buf[TIME_NUM]; + int ret; + + ret = data_calc(buf, tm, TIME_NUM); + if (ret < 0) + goto out; + ret = max8925_bulk_write(info->rtc, MAX8925_RTC_SEC, TIME_NUM, buf); +out: + return ret; +} + +static int max8925_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm) +{ + struct max8925_rtc_info *info = dev_get_drvdata(dev); + unsigned char buf[TIME_NUM]; + int ret; + + ret = max8925_bulk_read(info->rtc, MAX8925_ALARM0_SEC, TIME_NUM, buf); + if (ret < 0) + goto out; + ret = tm_calc(&alrm->time, buf, TIME_NUM); + if (ret < 0) + goto out; + ret = max8925_reg_read(info->rtc, MAX8925_RTC_IRQ_MASK); + if (ret < 0) + goto out; + if (ret & ALARM0_IRQ) { + alrm->enabled = 0; + } else { + ret = max8925_reg_read(info->rtc, MAX8925_ALARM0_CNTL); + if (ret < 0) + goto out; + if (!ret) + alrm->enabled = 0; + else + alrm->enabled = 1; + } + ret = max8925_reg_read(info->rtc, MAX8925_RTC_STATUS); + if (ret < 0) + goto out; + if (ret & ALARM0_STATUS) + alrm->pending = 1; + else + alrm->pending = 0; + return 0; +out: + return ret; +} + +static int max8925_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm) +{ + struct max8925_rtc_info *info = dev_get_drvdata(dev); + unsigned char buf[TIME_NUM]; + int ret; + + ret = data_calc(buf, &alrm->time, TIME_NUM); + if (ret < 0) + goto out; + ret = max8925_bulk_write(info->rtc, MAX8925_ALARM0_SEC, TIME_NUM, buf); + if (ret < 0) + goto out; + if (alrm->enabled) + /* only enable alarm on year/month/day/hour/min/sec */ + ret = max8925_reg_write(info->rtc, MAX8925_ALARM0_CNTL, 0x77); + else + ret = max8925_reg_write(info->rtc, MAX8925_ALARM0_CNTL, 0x0); +out: + return ret; +} + +static const struct rtc_class_ops max8925_rtc_ops = { + .read_time = max8925_rtc_read_time, + .set_time = max8925_rtc_set_time, + .read_alarm = max8925_rtc_read_alarm, + .set_alarm = max8925_rtc_set_alarm, +}; + +static int max8925_rtc_probe(struct platform_device *pdev) +{ + struct max8925_chip *chip = dev_get_drvdata(pdev->dev.parent); + struct max8925_rtc_info *info; + int ret; + + info = devm_kzalloc(&pdev->dev, sizeof(struct max8925_rtc_info), + GFP_KERNEL); + if (!info) + return -ENOMEM; + info->chip = chip; + info->rtc = chip->rtc; + info->dev = &pdev->dev; + info->irq = platform_get_irq(pdev, 0); + + ret = devm_request_threaded_irq(&pdev->dev, info->irq, NULL, + rtc_update_handler, IRQF_ONESHOT, + "rtc-alarm0", info); + if (ret < 0) { + dev_err(chip->dev, "Failed to request IRQ: #%d: %d\n", + info->irq, ret); + return ret; + } + + dev_set_drvdata(&pdev->dev, info); + /* XXX - isn't this redundant? */ + platform_set_drvdata(pdev, info); + + device_init_wakeup(&pdev->dev, true); + + info->rtc_dev = devm_rtc_device_register(&pdev->dev, "max8925-rtc", + &max8925_rtc_ops, THIS_MODULE); + ret = PTR_ERR(info->rtc_dev); + if (IS_ERR(info->rtc_dev)) { + dev_err(&pdev->dev, "Failed to register RTC device: %d\n", ret); + return ret; + } + + return 0; +} + +#ifdef CONFIG_PM_SLEEP +static int max8925_rtc_suspend(struct device *dev) +{ + struct platform_device *pdev = to_platform_device(dev); + struct max8925_chip *chip = dev_get_drvdata(pdev->dev.parent); + + if (device_may_wakeup(dev)) + chip->wakeup_flag |= 1 << MAX8925_IRQ_RTC_ALARM0; + return 0; +} +static int max8925_rtc_resume(struct device *dev) +{ + struct platform_device *pdev = to_platform_device(dev); + struct max8925_chip *chip = dev_get_drvdata(pdev->dev.parent); + + if (device_may_wakeup(dev)) + chip->wakeup_flag &= ~(1 << MAX8925_IRQ_RTC_ALARM0); + return 0; +} +#endif + +static SIMPLE_DEV_PM_OPS(max8925_rtc_pm_ops, max8925_rtc_suspend, max8925_rtc_resume); + +static struct platform_driver max8925_rtc_driver = { + .driver = { + .name = "max8925-rtc", + .pm = &max8925_rtc_pm_ops, + }, + .probe = max8925_rtc_probe, +}; + +module_platform_driver(max8925_rtc_driver); + +MODULE_DESCRIPTION("Maxim MAX8925 RTC driver"); +MODULE_AUTHOR("Haojian Zhuang "); +MODULE_LICENSE("GPL"); + -- cgit v1.3.1