ftrace: Synchronize the initialization of ftrace_opsgrafted

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 <rostedt@goodmis.org>

1 files changed, 236 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-loongson1-pwm.c b/drivers/clocksource/timer-loongson1-pwm.c
new file mode 100644
index 000000000..244d66835
--- /dev/null
+++ b/drivers/clocksource/timer-loongson1-pwm.c
@@ -0,0 +1,236 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Clocksource driver for Loongson-1 SoC
+ *
+ * Copyright (c) 2023 Keguang Zhang <keguang.zhang@gmail.com>
+ */
+
+#include <linux/clockchips.h>
+#include <linux/interrupt.h>
+#include <linux/sizes.h>
+#include "timer-of.h"
+
+/* Loongson-1 PWM Timer Register Definitions */
+#define PWM_CNTR		0x0
+#define PWM_HRC			0x4
+#define PWM_LRC			0x8
+#define PWM_CTRL		0xc
+
+/* PWM Control Register Bits */
+#define INT_LRC_EN		BIT(11)
+#define INT_HRC_EN		BIT(10)
+#define CNTR_RST		BIT(7)
+#define INT_SR			BIT(6)
+#define INT_EN			BIT(5)
+#define PWM_SINGLE		BIT(4)
+#define PWM_OE			BIT(3)
+#define CNT_EN			BIT(0)
+
+#define CNTR_WIDTH		24
+
+static DEFINE_RAW_SPINLOCK(ls1x_timer_lock);
+
+struct ls1x_clocksource {
+	void __iomem *reg_base;
+	unsigned long ticks_per_jiffy;
+	struct clocksource clksrc;
+};
+
+static inline struct ls1x_clocksource *to_ls1x_clksrc(struct clocksource *c)
+{
+	return container_of(c, struct ls1x_clocksource, clksrc);
+}
+
+static inline void ls1x_pwmtimer_set_period(unsigned int period,
+					    struct timer_of *to)
+{
+	writel(period, timer_of_base(to) + PWM_LRC);
+	writel(period, timer_of_base(to) + PWM_HRC);
+}
+
+static inline void ls1x_pwmtimer_clear(struct timer_of *to)
+{
+	writel(0, timer_of_base(to) + PWM_CNTR);
+}
+
+static inline void ls1x_pwmtimer_start(struct timer_of *to)
+{
+	writel((INT_EN | PWM_OE | CNT_EN), timer_of_base(to) + PWM_CTRL);
+}
+
+static inline void ls1x_pwmtimer_stop(struct timer_of *to)
+{
+	writel(0, timer_of_base(to) + PWM_CTRL);
+}
+
+static inline void ls1x_pwmtimer_irq_ack(struct timer_of *to)
+{
+	int val;
+
+	val = readl(timer_of_base(to) + PWM_CTRL);
+	val |= INT_SR;
+	writel(val, timer_of_base(to) + PWM_CTRL);
+}
+
+static irqreturn_t ls1x_clockevent_isr(int irq, void *dev_id)
+{
+	struct clock_event_device *clkevt = dev_id;
+	struct timer_of *to = to_timer_of(clkevt);
+
+	ls1x_pwmtimer_irq_ack(to);
+	ls1x_pwmtimer_clear(to);
+	ls1x_pwmtimer_start(to);
+
+	clkevt->event_handler(clkevt);
+
+	return IRQ_HANDLED;
+}
+
+static int ls1x_clockevent_set_state_periodic(struct clock_event_device *clkevt)
+{
+	struct timer_of *to = to_timer_of(clkevt);
+
+	raw_spin_lock(&ls1x_timer_lock);
+	ls1x_pwmtimer_set_period(timer_of_period(to), to);
+	ls1x_pwmtimer_clear(to);
+	ls1x_pwmtimer_start(to);
+	raw_spin_unlock(&ls1x_timer_lock);
+
+	return 0;
+}
+
+static int ls1x_clockevent_tick_resume(struct clock_event_device *clkevt)
+{
+	raw_spin_lock(&ls1x_timer_lock);
+	ls1x_pwmtimer_start(to_timer_of(clkevt));
+	raw_spin_unlock(&ls1x_timer_lock);
+
+	return 0;
+}
+
+static int ls1x_clockevent_set_state_shutdown(struct clock_event_device *clkevt)
+{
+	raw_spin_lock(&ls1x_timer_lock);
+	ls1x_pwmtimer_stop(to_timer_of(clkevt));
+	raw_spin_unlock(&ls1x_timer_lock);
+
+	return 0;
+}
+
+static int ls1x_clockevent_set_next(unsigned long evt,
+				    struct clock_event_device *clkevt)
+{
+	struct timer_of *to = to_timer_of(clkevt);
+
+	raw_spin_lock(&ls1x_timer_lock);
+	ls1x_pwmtimer_set_period(evt, to);
+	ls1x_pwmtimer_clear(to);
+	ls1x_pwmtimer_start(to);
+	raw_spin_unlock(&ls1x_timer_lock);
+
+	return 0;
+}
+
+static struct timer_of ls1x_to = {
+	.flags = TIMER_OF_IRQ | TIMER_OF_BASE | TIMER_OF_CLOCK,
+	.clkevt = {
+		.name			= "ls1x-pwmtimer",
+		.features		= CLOCK_EVT_FEAT_PERIODIC |
+					  CLOCK_EVT_FEAT_ONESHOT,
+		.rating			= 300,
+		.set_next_event		= ls1x_clockevent_set_next,
+		.set_state_periodic	= ls1x_clockevent_set_state_periodic,
+		.set_state_oneshot	= ls1x_clockevent_set_state_shutdown,
+		.set_state_shutdown	= ls1x_clockevent_set_state_shutdown,
+		.tick_resume		= ls1x_clockevent_tick_resume,
+	},
+	.of_irq = {
+		.handler		= ls1x_clockevent_isr,
+		.flags			= IRQF_TIMER,
+	},
+};
+
+/*
+ * Since the PWM timer overflows every two ticks, its not very useful
+ * to just read by itself. So use jiffies to emulate a free
+ * running counter:
+ */
+static u64 ls1x_clocksource_read(struct clocksource *cs)
+{
+	struct ls1x_clocksource *ls1x_cs = to_ls1x_clksrc(cs);
+	unsigned long flags;
+	int count;
+	u32 jifs;
+	static int old_count;
+	static u32 old_jifs;
+
+	raw_spin_lock_irqsave(&ls1x_timer_lock, flags);
+	/*
+	 * Although our caller may have the read side of xtime_lock,
+	 * this is now a seqlock, and we are cheating in this routine
+	 * by having side effects on state that we cannot undo if
+	 * there is a collision on the seqlock and our caller has to
+	 * retry.  (Namely, old_jifs and old_count.)  So we must treat
+	 * jiffies as volatile despite the lock.  We read jiffies
+	 * before latching the timer count to guarantee that although
+	 * the jiffies value might be older than the count (that is,
+	 * the counter may underflow between the last point where
+	 * jiffies was incremented and the point where we latch the
+	 * count), it cannot be newer.
+	 */
+	jifs = jiffies;
+	/* read the count */
+	count = readl(ls1x_cs->reg_base + PWM_CNTR);
+
+	/*
+	 * It's possible for count to appear to go the wrong way for this
+	 * reason:
+	 *
+	 *  The timer counter underflows, but we haven't handled the resulting
+	 *  interrupt and incremented jiffies yet.
+	 *
+	 * Previous attempts to handle these cases intelligently were buggy, so
+	 * we just do the simple thing now.
+	 */
+	if (count < old_count && jifs == old_jifs)
+		count = old_count;
+
+	old_count = count;
+	old_jifs = jifs;
+
+	raw_spin_unlock_irqrestore(&ls1x_timer_lock, flags);
+
+	return (u64)(jifs * ls1x_cs->ticks_per_jiffy) + count;
+}
+
+static struct ls1x_clocksource ls1x_clocksource = {
+	.clksrc = {
+		.name           = "ls1x-pwmtimer",
+		.rating		= 300,
+		.read           = ls1x_clocksource_read,
+		.mask           = CLOCKSOURCE_MASK(CNTR_WIDTH),
+		.flags          = CLOCK_SOURCE_IS_CONTINUOUS,
+	},
+};
+
+static int __init ls1x_pwm_clocksource_init(struct device_node *np)
+{
+	struct timer_of *to = &ls1x_to;
+	int ret;
+
+	ret = timer_of_init(np, to);
+	if (ret)
+		return ret;
+
+	clockevents_config_and_register(&to->clkevt, timer_of_rate(to),
+					0x1, GENMASK(CNTR_WIDTH - 1, 0));
+
+	ls1x_clocksource.reg_base = timer_of_base(to);
+	ls1x_clocksource.ticks_per_jiffy = timer_of_period(to);
+
+	return clocksource_register_hz(&ls1x_clocksource.clksrc,
+				       timer_of_rate(to));
+}
+
+TIMER_OF_DECLARE(ls1x_pwm_clocksource, "loongson,ls1b-pwmtimer",
+		 ls1x_pwm_clocksource_init);