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, 110 insertions, 0 deletions

diff --git a/drivers/clocksource/clps711x-timer.c b/drivers/clocksource/clps711x-timer.c
new file mode 100644
index 000000000..63ae3a691
--- /dev/null
+++ b/drivers/clocksource/clps711x-timer.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Cirrus Logic CLPS711X clocksource driver
+ *
+ *  Copyright (C) 2014 Alexander Shiyan <shc_work@mail.ru>
+ */
+
+#include <linux/clk.h>
+#include <linux/clockchips.h>
+#include <linux/clocksource.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/sched_clock.h>
+#include <linux/slab.h>
+
+enum {
+	CLPS711X_CLKSRC_CLOCKSOURCE,
+	CLPS711X_CLKSRC_CLOCKEVENT,
+};
+
+static void __iomem *tcd;
+
+static u64 notrace clps711x_sched_clock_read(void)
+{
+	return ~readw(tcd);
+}
+
+static void __init clps711x_clksrc_init(struct clk *clock, void __iomem *base)
+{
+	unsigned long rate = clk_get_rate(clock);
+
+	tcd = base;
+
+	clocksource_mmio_init(tcd, "clps711x-clocksource", rate, 300, 16,
+			      clocksource_mmio_readw_down);
+
+	sched_clock_register(clps711x_sched_clock_read, 16, rate);
+}
+
+static irqreturn_t clps711x_timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+
+	evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+static int __init _clps711x_clkevt_init(struct clk *clock, void __iomem *base,
+					unsigned int irq)
+{
+	struct clock_event_device *clkevt;
+	unsigned long rate;
+
+	clkevt = kzalloc_obj(*clkevt);
+	if (!clkevt)
+		return -ENOMEM;
+
+	rate = clk_get_rate(clock);
+
+	/* Set Timer prescaler */
+	writew(DIV_ROUND_CLOSEST(rate, HZ), base);
+
+	clkevt->name = "clps711x-clockevent";
+	clkevt->rating = 300;
+	clkevt->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_C3STOP;
+	clkevt->cpumask = cpumask_of(0);
+	clockevents_config_and_register(clkevt, HZ, 0, 0);
+
+	return request_irq(irq, clps711x_timer_interrupt, IRQF_TIMER,
+			   "clps711x-timer", clkevt);
+}
+
+static int __init clps711x_timer_init(struct device_node *np)
+{
+	unsigned int irq = irq_of_parse_and_map(np, 0);
+	struct clk *clock = of_clk_get(np, 0);
+	void __iomem *base = of_iomap(np, 0);
+	int ret = 0;
+
+	if (!base)
+		return -ENOMEM;
+	if (!irq) {
+		ret = -EINVAL;
+		goto unmap_io;
+	}
+	if (IS_ERR(clock)) {
+		ret = PTR_ERR(clock);
+		goto unmap_io;
+	}
+
+	switch (of_alias_get_id(np, "timer")) {
+	case CLPS711X_CLKSRC_CLOCKSOURCE:
+		clps711x_clksrc_init(clock, base);
+		return 0;
+	case CLPS711X_CLKSRC_CLOCKEVENT:
+		ret =  _clps711x_clkevt_init(clock, base, irq);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+unmap_io:
+	iounmap(base);
+	return ret;
+}
+TIMER_OF_DECLARE(clps711x, "cirrus,ep7209-timer", clps711x_timer_init);