From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- drivers/rtc/rtc-m48t35.c | 193 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 193 insertions(+) create mode 100644 drivers/rtc/rtc-m48t35.c (limited to 'drivers/rtc/rtc-m48t35.c') diff --git a/drivers/rtc/rtc-m48t35.c b/drivers/rtc/rtc-m48t35.c new file mode 100644 index 000000000..92f19bf99 --- /dev/null +++ b/drivers/rtc/rtc-m48t35.c @@ -0,0 +1,193 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Driver for the SGS-Thomson M48T35 Timekeeper RAM chip + * + * Copyright (C) 2000 Silicon Graphics, Inc. + * Written by Ulf Carlsson (ulfc@engr.sgi.com) + * + * Copyright (C) 2008 Thomas Bogendoerfer + * + * Based on code written by Paul Gortmaker. + */ + +#include +#include +#include +#include +#include +#include +#include + +struct m48t35_rtc { + u8 pad[0x7ff8]; /* starts at 0x7ff8 */ +#ifdef CONFIG_SGI_IP27 + u8 hour; + u8 min; + u8 sec; + u8 control; + u8 year; + u8 month; + u8 date; + u8 day; +#else + u8 control; + u8 sec; + u8 min; + u8 hour; + u8 day; + u8 date; + u8 month; + u8 year; +#endif +}; + +#define M48T35_RTC_SET 0x80 +#define M48T35_RTC_READ 0x40 + +struct m48t35_priv { + struct rtc_device *rtc; + struct m48t35_rtc __iomem *reg; + size_t size; + unsigned long baseaddr; + spinlock_t lock; +}; + +static int m48t35_read_time(struct device *dev, struct rtc_time *tm) +{ + struct m48t35_priv *priv = dev_get_drvdata(dev); + u8 control; + + /* + * Only the values that we read from the RTC are set. We leave + * tm_wday, tm_yday and tm_isdst untouched. Even though the + * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated + * by the RTC when initially set to a non-zero value. + */ + spin_lock_irq(&priv->lock); + control = readb(&priv->reg->control); + writeb(control | M48T35_RTC_READ, &priv->reg->control); + tm->tm_sec = readb(&priv->reg->sec); + tm->tm_min = readb(&priv->reg->min); + tm->tm_hour = readb(&priv->reg->hour); + tm->tm_mday = readb(&priv->reg->date); + tm->tm_mon = readb(&priv->reg->month); + tm->tm_year = readb(&priv->reg->year); + writeb(control, &priv->reg->control); + spin_unlock_irq(&priv->lock); + + tm->tm_sec = bcd2bin(tm->tm_sec); + tm->tm_min = bcd2bin(tm->tm_min); + tm->tm_hour = bcd2bin(tm->tm_hour); + tm->tm_mday = bcd2bin(tm->tm_mday); + tm->tm_mon = bcd2bin(tm->tm_mon); + tm->tm_year = bcd2bin(tm->tm_year); + + /* + * Account for differences between how the RTC uses the values + * and how they are defined in a struct rtc_time; + */ + tm->tm_year += 70; + if (tm->tm_year <= 69) + tm->tm_year += 100; + + tm->tm_mon--; + return 0; +} + +static int m48t35_set_time(struct device *dev, struct rtc_time *tm) +{ + struct m48t35_priv *priv = dev_get_drvdata(dev); + unsigned char mon, day, hrs, min, sec; + unsigned int yrs; + u8 control; + + yrs = tm->tm_year + 1900; + mon = tm->tm_mon + 1; /* tm_mon starts at zero */ + day = tm->tm_mday; + hrs = tm->tm_hour; + min = tm->tm_min; + sec = tm->tm_sec; + + if (yrs < 1970) + return -EINVAL; + + yrs -= 1970; + if (yrs > 255) /* They are unsigned */ + return -EINVAL; + + if (yrs > 169) + return -EINVAL; + + if (yrs >= 100) + yrs -= 100; + + sec = bin2bcd(sec); + min = bin2bcd(min); + hrs = bin2bcd(hrs); + day = bin2bcd(day); + mon = bin2bcd(mon); + yrs = bin2bcd(yrs); + + spin_lock_irq(&priv->lock); + control = readb(&priv->reg->control); + writeb(control | M48T35_RTC_SET, &priv->reg->control); + writeb(yrs, &priv->reg->year); + writeb(mon, &priv->reg->month); + writeb(day, &priv->reg->date); + writeb(hrs, &priv->reg->hour); + writeb(min, &priv->reg->min); + writeb(sec, &priv->reg->sec); + writeb(control, &priv->reg->control); + spin_unlock_irq(&priv->lock); + return 0; +} + +static const struct rtc_class_ops m48t35_ops = { + .read_time = m48t35_read_time, + .set_time = m48t35_set_time, +}; + +static int m48t35_probe(struct platform_device *pdev) +{ + struct resource *res; + struct m48t35_priv *priv; + + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + if (!res) + return -ENODEV; + priv = devm_kzalloc(&pdev->dev, sizeof(struct m48t35_priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + priv->size = resource_size(res); + if (!devm_request_mem_region(&pdev->dev, res->start, priv->size, + pdev->name)) + return -EBUSY; + + priv->baseaddr = res->start; + priv->reg = devm_ioremap(&pdev->dev, priv->baseaddr, priv->size); + if (!priv->reg) + return -ENOMEM; + + spin_lock_init(&priv->lock); + + platform_set_drvdata(pdev, priv); + + priv->rtc = devm_rtc_device_register(&pdev->dev, "m48t35", + &m48t35_ops, THIS_MODULE); + return PTR_ERR_OR_ZERO(priv->rtc); +} + +static struct platform_driver m48t35_platform_driver = { + .driver = { + .name = "rtc-m48t35", + }, + .probe = m48t35_probe, +}; + +module_platform_driver(m48t35_platform_driver); + +MODULE_AUTHOR("Thomas Bogendoerfer "); +MODULE_DESCRIPTION("M48T35 RTC driver"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:rtc-m48t35"); -- cgit v1.3.1