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-as3722.c | 252 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 252 insertions(+) create mode 100644 drivers/rtc/rtc-as3722.c (limited to 'drivers/rtc/rtc-as3722.c') diff --git a/drivers/rtc/rtc-as3722.c b/drivers/rtc/rtc-as3722.c new file mode 100644 index 000000000..9682d6457 --- /dev/null +++ b/drivers/rtc/rtc-as3722.c @@ -0,0 +1,252 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * rtc-as3722.c - Real Time Clock driver for ams AS3722 PMICs + * + * Copyright (C) 2013 ams AG + * Copyright (c) 2013, NVIDIA Corporation. All rights reserved. + * + * Author: Florian Lobmaier + * Author: Laxman Dewangan + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define AS3722_RTC_START_YEAR 2000 +struct as3722_rtc { + struct rtc_device *rtc; + struct device *dev; + struct as3722 *as3722; + int alarm_irq; + bool irq_enable; +}; + +static void as3722_time_to_reg(u8 *rbuff, struct rtc_time *tm) +{ + rbuff[0] = bin2bcd(tm->tm_sec); + rbuff[1] = bin2bcd(tm->tm_min); + rbuff[2] = bin2bcd(tm->tm_hour); + rbuff[3] = bin2bcd(tm->tm_mday); + rbuff[4] = bin2bcd(tm->tm_mon + 1); + rbuff[5] = bin2bcd(tm->tm_year - (AS3722_RTC_START_YEAR - 1900)); +} + +static void as3722_reg_to_time(u8 *rbuff, struct rtc_time *tm) +{ + tm->tm_sec = bcd2bin(rbuff[0] & 0x7F); + tm->tm_min = bcd2bin(rbuff[1] & 0x7F); + tm->tm_hour = bcd2bin(rbuff[2] & 0x3F); + tm->tm_mday = bcd2bin(rbuff[3] & 0x3F); + tm->tm_mon = bcd2bin(rbuff[4] & 0x1F) - 1; + tm->tm_year = (AS3722_RTC_START_YEAR - 1900) + bcd2bin(rbuff[5] & 0x7F); + return; +} + +static int as3722_rtc_read_time(struct device *dev, struct rtc_time *tm) +{ + struct as3722_rtc *as3722_rtc = dev_get_drvdata(dev); + struct as3722 *as3722 = as3722_rtc->as3722; + u8 as_time_array[6]; + int ret; + + ret = as3722_block_read(as3722, AS3722_RTC_SECOND_REG, + 6, as_time_array); + if (ret < 0) { + dev_err(dev, "RTC_SECOND reg block read failed %d\n", ret); + return ret; + } + as3722_reg_to_time(as_time_array, tm); + return 0; +} + +static int as3722_rtc_set_time(struct device *dev, struct rtc_time *tm) +{ + struct as3722_rtc *as3722_rtc = dev_get_drvdata(dev); + struct as3722 *as3722 = as3722_rtc->as3722; + u8 as_time_array[6]; + int ret; + + if (tm->tm_year < (AS3722_RTC_START_YEAR - 1900)) + return -EINVAL; + + as3722_time_to_reg(as_time_array, tm); + ret = as3722_block_write(as3722, AS3722_RTC_SECOND_REG, 6, + as_time_array); + if (ret < 0) + dev_err(dev, "RTC_SECOND reg block write failed %d\n", ret); + return ret; +} + +static int as3722_rtc_alarm_irq_enable(struct device *dev, + unsigned int enabled) +{ + struct as3722_rtc *as3722_rtc = dev_get_drvdata(dev); + + if (enabled && !as3722_rtc->irq_enable) { + enable_irq(as3722_rtc->alarm_irq); + as3722_rtc->irq_enable = true; + } else if (!enabled && as3722_rtc->irq_enable) { + disable_irq(as3722_rtc->alarm_irq); + as3722_rtc->irq_enable = false; + } + return 0; +} + +static int as3722_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm) +{ + struct as3722_rtc *as3722_rtc = dev_get_drvdata(dev); + struct as3722 *as3722 = as3722_rtc->as3722; + u8 as_time_array[6]; + int ret; + + ret = as3722_block_read(as3722, AS3722_RTC_ALARM_SECOND_REG, 6, + as_time_array); + if (ret < 0) { + dev_err(dev, "RTC_ALARM_SECOND block read failed %d\n", ret); + return ret; + } + + as3722_reg_to_time(as_time_array, &alrm->time); + return 0; +} + +static int as3722_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm) +{ + struct as3722_rtc *as3722_rtc = dev_get_drvdata(dev); + struct as3722 *as3722 = as3722_rtc->as3722; + u8 as_time_array[6]; + int ret; + + if (alrm->time.tm_year < (AS3722_RTC_START_YEAR - 1900)) + return -EINVAL; + + ret = as3722_rtc_alarm_irq_enable(dev, 0); + if (ret < 0) { + dev_err(dev, "Disable RTC alarm failed\n"); + return ret; + } + + as3722_time_to_reg(as_time_array, &alrm->time); + ret = as3722_block_write(as3722, AS3722_RTC_ALARM_SECOND_REG, 6, + as_time_array); + if (ret < 0) { + dev_err(dev, "RTC_ALARM_SECOND block write failed %d\n", ret); + return ret; + } + + if (alrm->enabled) + ret = as3722_rtc_alarm_irq_enable(dev, alrm->enabled); + return ret; +} + +static irqreturn_t as3722_alarm_irq(int irq, void *data) +{ + struct as3722_rtc *as3722_rtc = data; + + rtc_update_irq(as3722_rtc->rtc, 1, RTC_IRQF | RTC_AF); + return IRQ_HANDLED; +} + +static const struct rtc_class_ops as3722_rtc_ops = { + .read_time = as3722_rtc_read_time, + .set_time = as3722_rtc_set_time, + .read_alarm = as3722_rtc_read_alarm, + .set_alarm = as3722_rtc_set_alarm, + .alarm_irq_enable = as3722_rtc_alarm_irq_enable, +}; + +static int as3722_rtc_probe(struct platform_device *pdev) +{ + struct as3722 *as3722 = dev_get_drvdata(pdev->dev.parent); + struct as3722_rtc *as3722_rtc; + int ret; + + as3722_rtc = devm_kzalloc(&pdev->dev, sizeof(*as3722_rtc), GFP_KERNEL); + if (!as3722_rtc) + return -ENOMEM; + + as3722_rtc->as3722 = as3722; + as3722_rtc->dev = &pdev->dev; + platform_set_drvdata(pdev, as3722_rtc); + + /* Enable the RTC to make sure it is running. */ + ret = as3722_update_bits(as3722, AS3722_RTC_CONTROL_REG, + AS3722_RTC_ON | AS3722_RTC_ALARM_WAKEUP_EN, + AS3722_RTC_ON | AS3722_RTC_ALARM_WAKEUP_EN); + if (ret < 0) { + dev_err(&pdev->dev, "RTC_CONTROL reg write failed: %d\n", ret); + return ret; + } + + device_init_wakeup(&pdev->dev, true); + + as3722_rtc->rtc = devm_rtc_device_register(&pdev->dev, "as3722-rtc", + &as3722_rtc_ops, THIS_MODULE); + if (IS_ERR(as3722_rtc->rtc)) { + ret = PTR_ERR(as3722_rtc->rtc); + dev_err(&pdev->dev, "RTC register failed: %d\n", ret); + return ret; + } + + as3722_rtc->alarm_irq = platform_get_irq(pdev, 0); + dev_info(&pdev->dev, "RTC interrupt %d\n", as3722_rtc->alarm_irq); + + ret = devm_request_threaded_irq(&pdev->dev, as3722_rtc->alarm_irq, NULL, + as3722_alarm_irq, IRQF_ONESHOT, + "rtc-alarm", as3722_rtc); + if (ret < 0) { + dev_err(&pdev->dev, "Failed to request alarm IRQ %d: %d\n", + as3722_rtc->alarm_irq, ret); + return ret; + } + disable_irq(as3722_rtc->alarm_irq); + return 0; +} + +#ifdef CONFIG_PM_SLEEP +static int as3722_rtc_suspend(struct device *dev) +{ + struct as3722_rtc *as3722_rtc = dev_get_drvdata(dev); + + if (device_may_wakeup(dev)) + enable_irq_wake(as3722_rtc->alarm_irq); + + return 0; +} + +static int as3722_rtc_resume(struct device *dev) +{ + struct as3722_rtc *as3722_rtc = dev_get_drvdata(dev); + + if (device_may_wakeup(dev)) + disable_irq_wake(as3722_rtc->alarm_irq); + return 0; +} +#endif + +static SIMPLE_DEV_PM_OPS(as3722_rtc_pm_ops, as3722_rtc_suspend, + as3722_rtc_resume); + +static struct platform_driver as3722_rtc_driver = { + .probe = as3722_rtc_probe, + .driver = { + .name = "as3722-rtc", + .pm = &as3722_rtc_pm_ops, + }, +}; +module_platform_driver(as3722_rtc_driver); + +MODULE_DESCRIPTION("RTC driver for AS3722 PMICs"); +MODULE_ALIAS("platform:as3722-rtc"); +MODULE_AUTHOR("Florian Lobmaier "); +MODULE_AUTHOR("Laxman Dewangan "); +MODULE_LICENSE("GPL"); -- cgit v1.3.1