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, 137 insertions, 0 deletions

diff --git a/drivers/clocksource/bcm2835_timer.c b/drivers/clocksource/bcm2835_timer.c
new file mode 100644
index 000000000..d7662301b
--- /dev/null
+++ b/drivers/clocksource/bcm2835_timer.c
@@ -0,0 +1,137 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2012 Simon Arlott
+ */
+
+#include <linux/bitops.h>
+#include <linux/clockchips.h>
+#include <linux/clocksource.h>
+#include <linux/interrupt.h>
+#include <linux/irqreturn.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/sched_clock.h>
+
+#include <asm/irq.h>
+
+#define REG_CONTROL	0x00
+#define REG_COUNTER_LO	0x04
+#define REG_COUNTER_HI	0x08
+#define REG_COMPARE(n)	(0x0c + (n) * 4)
+#define MAX_TIMER	3
+#define DEFAULT_TIMER	3
+
+struct bcm2835_timer {
+	void __iomem *control;
+	void __iomem *compare;
+	int match_mask;
+	struct clock_event_device evt;
+};
+
+static void __iomem *system_clock __read_mostly;
+
+static u64 notrace bcm2835_sched_read(void)
+{
+	return readl_relaxed(system_clock);
+}
+
+static int bcm2835_time_set_next_event(unsigned long event,
+	struct clock_event_device *evt_dev)
+{
+	struct bcm2835_timer *timer = container_of(evt_dev,
+		struct bcm2835_timer, evt);
+	writel_relaxed(readl_relaxed(system_clock) + event,
+		timer->compare);
+	return 0;
+}
+
+static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
+{
+	struct bcm2835_timer *timer = dev_id;
+	void (*event_handler)(struct clock_event_device *);
+	if (readl_relaxed(timer->control) & timer->match_mask) {
+		writel_relaxed(timer->match_mask, timer->control);
+
+		event_handler = READ_ONCE(timer->evt.event_handler);
+		if (event_handler)
+			event_handler(&timer->evt);
+		return IRQ_HANDLED;
+	} else {
+		return IRQ_NONE;
+	}
+}
+
+static int __init bcm2835_timer_init(struct device_node *node)
+{
+	void __iomem *base;
+	u32 freq;
+	int irq, ret;
+	struct bcm2835_timer *timer;
+
+	base = of_iomap(node, 0);
+	if (!base) {
+		pr_err("Can't remap registers\n");
+		return -ENXIO;
+	}
+
+	ret = of_property_read_u32(node, "clock-frequency", &freq);
+	if (ret) {
+		pr_err("Can't read clock-frequency\n");
+		goto err_iounmap;
+	}
+
+	system_clock = base + REG_COUNTER_LO;
+	sched_clock_register(bcm2835_sched_read, 32, freq);
+
+	clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
+		freq, 300, 32, clocksource_mmio_readl_up);
+
+	irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
+	if (irq <= 0) {
+		pr_err("Can't parse IRQ\n");
+		ret = -EINVAL;
+		goto err_iounmap;
+	}
+
+	timer = kzalloc_obj(*timer);
+	if (!timer) {
+		ret = -ENOMEM;
+		goto err_iounmap;
+	}
+
+	timer->control = base + REG_CONTROL;
+	timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
+	timer->match_mask = BIT(DEFAULT_TIMER);
+	timer->evt.name = node->name;
+	timer->evt.rating = 300;
+	timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
+	timer->evt.set_next_event = bcm2835_time_set_next_event;
+	timer->evt.cpumask = cpumask_of(0);
+
+	ret = request_irq(irq, bcm2835_time_interrupt, IRQF_TIMER | IRQF_SHARED,
+			  node->name, timer);
+	if (ret) {
+		pr_err("Can't set up timer IRQ\n");
+		goto err_timer_free;
+	}
+
+	clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
+
+	pr_info("bcm2835: system timer (irq = %d)\n", irq);
+
+	return 0;
+
+err_timer_free:
+	kfree(timer);
+
+err_iounmap:
+	iounmap(base);
+	return ret;
+}
+TIMER_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
+			bcm2835_timer_init);