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-msm6242.c | 228 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 228 insertions(+) create mode 100644 drivers/rtc/rtc-msm6242.c (limited to 'drivers/rtc/rtc-msm6242.c') diff --git a/drivers/rtc/rtc-msm6242.c b/drivers/rtc/rtc-msm6242.c new file mode 100644 index 000000000..80e364baa --- /dev/null +++ b/drivers/rtc/rtc-msm6242.c @@ -0,0 +1,228 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Oki MSM6242 RTC Driver + * + * Copyright 2009 Geert Uytterhoeven + * + * Based on the A2000 TOD code in arch/m68k/amiga/config.c + * Copyright (C) 1993 Hamish Macdonald + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include +#include +#include + + +enum { + MSM6242_SECOND1 = 0x0, /* 1-second digit register */ + MSM6242_SECOND10 = 0x1, /* 10-second digit register */ + MSM6242_MINUTE1 = 0x2, /* 1-minute digit register */ + MSM6242_MINUTE10 = 0x3, /* 10-minute digit register */ + MSM6242_HOUR1 = 0x4, /* 1-hour digit register */ + MSM6242_HOUR10 = 0x5, /* PM/AM, 10-hour digit register */ + MSM6242_DAY1 = 0x6, /* 1-day digit register */ + MSM6242_DAY10 = 0x7, /* 10-day digit register */ + MSM6242_MONTH1 = 0x8, /* 1-month digit register */ + MSM6242_MONTH10 = 0x9, /* 10-month digit register */ + MSM6242_YEAR1 = 0xa, /* 1-year digit register */ + MSM6242_YEAR10 = 0xb, /* 10-year digit register */ + MSM6242_WEEK = 0xc, /* Week register */ + MSM6242_CD = 0xd, /* Control Register D */ + MSM6242_CE = 0xe, /* Control Register E */ + MSM6242_CF = 0xf, /* Control Register F */ +}; + +#define MSM6242_HOUR10_AM (0 << 2) +#define MSM6242_HOUR10_PM (1 << 2) +#define MSM6242_HOUR10_HR_MASK (3 << 0) + +#define MSM6242_WEEK_SUNDAY 0 +#define MSM6242_WEEK_MONDAY 1 +#define MSM6242_WEEK_TUESDAY 2 +#define MSM6242_WEEK_WEDNESDAY 3 +#define MSM6242_WEEK_THURSDAY 4 +#define MSM6242_WEEK_FRIDAY 5 +#define MSM6242_WEEK_SATURDAY 6 + +#define MSM6242_CD_30_S_ADJ (1 << 3) /* 30-second adjustment */ +#define MSM6242_CD_IRQ_FLAG (1 << 2) +#define MSM6242_CD_BUSY (1 << 1) +#define MSM6242_CD_HOLD (1 << 0) + +#define MSM6242_CE_T_MASK (3 << 2) +#define MSM6242_CE_T_64HZ (0 << 2) /* period 1/64 second */ +#define MSM6242_CE_T_1HZ (1 << 2) /* period 1 second */ +#define MSM6242_CE_T_1MINUTE (2 << 2) /* period 1 minute */ +#define MSM6242_CE_T_1HOUR (3 << 2) /* period 1 hour */ + +#define MSM6242_CE_ITRPT_STND (1 << 1) +#define MSM6242_CE_MASK (1 << 0) /* STD.P output control */ + +#define MSM6242_CF_TEST (1 << 3) +#define MSM6242_CF_12H (0 << 2) +#define MSM6242_CF_24H (1 << 2) +#define MSM6242_CF_STOP (1 << 1) +#define MSM6242_CF_REST (1 << 0) /* reset */ + + +struct msm6242_priv { + u32 __iomem *regs; + struct rtc_device *rtc; +}; + +static inline unsigned int msm6242_read(struct msm6242_priv *priv, + unsigned int reg) +{ + return __raw_readl(&priv->regs[reg]) & 0xf; +} + +static inline void msm6242_write(struct msm6242_priv *priv, unsigned int val, + unsigned int reg) +{ + __raw_writel(val, &priv->regs[reg]); +} + +static void msm6242_lock(struct msm6242_priv *priv) +{ + int cnt = 5; + + msm6242_write(priv, MSM6242_CD_HOLD|MSM6242_CD_IRQ_FLAG, MSM6242_CD); + + while ((msm6242_read(priv, MSM6242_CD) & MSM6242_CD_BUSY) && cnt) { + msm6242_write(priv, MSM6242_CD_IRQ_FLAG, MSM6242_CD); + udelay(70); + msm6242_write(priv, MSM6242_CD_HOLD|MSM6242_CD_IRQ_FLAG, MSM6242_CD); + cnt--; + } + + if (!cnt) + pr_warn("timed out waiting for RTC (0x%x)\n", + msm6242_read(priv, MSM6242_CD)); +} + +static void msm6242_unlock(struct msm6242_priv *priv) +{ + msm6242_write(priv, MSM6242_CD_IRQ_FLAG, MSM6242_CD); +} + +static int msm6242_read_time(struct device *dev, struct rtc_time *tm) +{ + struct msm6242_priv *priv = dev_get_drvdata(dev); + + msm6242_lock(priv); + + tm->tm_sec = msm6242_read(priv, MSM6242_SECOND10) * 10 + + msm6242_read(priv, MSM6242_SECOND1); + tm->tm_min = msm6242_read(priv, MSM6242_MINUTE10) * 10 + + msm6242_read(priv, MSM6242_MINUTE1); + tm->tm_hour = (msm6242_read(priv, MSM6242_HOUR10) & + MSM6242_HOUR10_HR_MASK) * 10 + + msm6242_read(priv, MSM6242_HOUR1); + tm->tm_mday = msm6242_read(priv, MSM6242_DAY10) * 10 + + msm6242_read(priv, MSM6242_DAY1); + tm->tm_wday = msm6242_read(priv, MSM6242_WEEK); + tm->tm_mon = msm6242_read(priv, MSM6242_MONTH10) * 10 + + msm6242_read(priv, MSM6242_MONTH1) - 1; + tm->tm_year = msm6242_read(priv, MSM6242_YEAR10) * 10 + + msm6242_read(priv, MSM6242_YEAR1); + if (tm->tm_year <= 69) + tm->tm_year += 100; + + if (!(msm6242_read(priv, MSM6242_CF) & MSM6242_CF_24H)) { + unsigned int pm = msm6242_read(priv, MSM6242_HOUR10) & + MSM6242_HOUR10_PM; + if (!pm && tm->tm_hour == 12) + tm->tm_hour = 0; + else if (pm && tm->tm_hour != 12) + tm->tm_hour += 12; + } + + msm6242_unlock(priv); + + return 0; +} + +static int msm6242_set_time(struct device *dev, struct rtc_time *tm) +{ + struct msm6242_priv *priv = dev_get_drvdata(dev); + + msm6242_lock(priv); + + msm6242_write(priv, tm->tm_sec / 10, MSM6242_SECOND10); + msm6242_write(priv, tm->tm_sec % 10, MSM6242_SECOND1); + msm6242_write(priv, tm->tm_min / 10, MSM6242_MINUTE10); + msm6242_write(priv, tm->tm_min % 10, MSM6242_MINUTE1); + if (msm6242_read(priv, MSM6242_CF) & MSM6242_CF_24H) + msm6242_write(priv, tm->tm_hour / 10, MSM6242_HOUR10); + else if (tm->tm_hour >= 12) + msm6242_write(priv, MSM6242_HOUR10_PM + (tm->tm_hour - 12) / 10, + MSM6242_HOUR10); + else + msm6242_write(priv, tm->tm_hour / 10, MSM6242_HOUR10); + msm6242_write(priv, tm->tm_hour % 10, MSM6242_HOUR1); + msm6242_write(priv, tm->tm_mday / 10, MSM6242_DAY10); + msm6242_write(priv, tm->tm_mday % 10, MSM6242_DAY1); + if (tm->tm_wday != -1) + msm6242_write(priv, tm->tm_wday, MSM6242_WEEK); + msm6242_write(priv, (tm->tm_mon + 1) / 10, MSM6242_MONTH10); + msm6242_write(priv, (tm->tm_mon + 1) % 10, MSM6242_MONTH1); + if (tm->tm_year >= 100) + tm->tm_year -= 100; + msm6242_write(priv, tm->tm_year / 10, MSM6242_YEAR10); + msm6242_write(priv, tm->tm_year % 10, MSM6242_YEAR1); + + msm6242_unlock(priv); + return 0; +} + +static const struct rtc_class_ops msm6242_rtc_ops = { + .read_time = msm6242_read_time, + .set_time = msm6242_set_time, +}; + +static int __init msm6242_rtc_probe(struct platform_device *pdev) +{ + struct resource *res; + struct msm6242_priv *priv; + struct rtc_device *rtc; + + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + if (!res) + return -ENODEV; + + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + priv->regs = devm_ioremap(&pdev->dev, res->start, resource_size(res)); + if (!priv->regs) + return -ENOMEM; + platform_set_drvdata(pdev, priv); + + rtc = devm_rtc_device_register(&pdev->dev, "rtc-msm6242", + &msm6242_rtc_ops, THIS_MODULE); + if (IS_ERR(rtc)) + return PTR_ERR(rtc); + + priv->rtc = rtc; + return 0; +} + +static struct platform_driver msm6242_rtc_driver = { + .driver = { + .name = "rtc-msm6242", + }, +}; + +module_platform_driver_probe(msm6242_rtc_driver, msm6242_rtc_probe); + +MODULE_AUTHOR("Geert Uytterhoeven "); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Oki MSM6242 RTC driver"); +MODULE_ALIAS("platform:rtc-msm6242"); -- cgit v1.3.1