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, 225 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-integrator-ap.c b/drivers/clocksource/timer-integrator-ap.c
new file mode 100644
index 000000000..a4c700b11
--- /dev/null
+++ b/drivers/clocksource/timer-integrator-ap.c
@@ -0,0 +1,225 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Integrator/AP timer driver
+ * Copyright (C) 2000-2003 Deep Blue Solutions Ltd
+ * Copyright (c) 2014, Linaro Limited
+ */
+
+#include <linux/clk.h>
+#include <linux/clocksource.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/of_address.h>
+#include <linux/clockchips.h>
+#include <linux/interrupt.h>
+#include <linux/sched_clock.h>
+
+#include "timer-sp.h"
+
+static void __iomem * sched_clk_base;
+
+static u64 notrace integrator_read_sched_clock(void)
+{
+	return -readl(sched_clk_base + TIMER_VALUE);
+}
+
+static int __init integrator_clocksource_init(unsigned long inrate,
+					      void __iomem *base)
+{
+	u32 ctrl = TIMER_CTRL_ENABLE | TIMER_CTRL_PERIODIC;
+	unsigned long rate = inrate;
+	int ret;
+
+	if (rate >= 1500000) {
+		rate /= 16;
+		ctrl |= TIMER_CTRL_DIV16;
+	}
+
+	writel(0xffff, base + TIMER_LOAD);
+	writel(ctrl, base + TIMER_CTRL);
+
+	ret = clocksource_mmio_init(base + TIMER_VALUE, "timer2",
+				    rate, 200, 16, clocksource_mmio_readl_down);
+	if (ret)
+		return ret;
+
+	sched_clk_base = base;
+	sched_clock_register(integrator_read_sched_clock, 16, rate);
+
+	return 0;
+}
+
+static unsigned long timer_reload;
+static void __iomem * clkevt_base;
+
+/*
+ * IRQ handler for the timer
+ */
+static irqreturn_t integrator_timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+
+	/* clear the interrupt */
+	writel(1, clkevt_base + TIMER_INTCLR);
+
+	evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+static int clkevt_shutdown(struct clock_event_device *evt)
+{
+	u32 ctrl = readl(clkevt_base + TIMER_CTRL) & ~TIMER_CTRL_ENABLE;
+
+	/* Disable timer */
+	writel(ctrl, clkevt_base + TIMER_CTRL);
+	return 0;
+}
+
+static int clkevt_set_oneshot(struct clock_event_device *evt)
+{
+	u32 ctrl = readl(clkevt_base + TIMER_CTRL) &
+		   ~(TIMER_CTRL_ENABLE | TIMER_CTRL_PERIODIC);
+
+	/* Leave the timer disabled, .set_next_event will enable it */
+	writel(ctrl, clkevt_base + TIMER_CTRL);
+	return 0;
+}
+
+static int clkevt_set_periodic(struct clock_event_device *evt)
+{
+	u32 ctrl = readl(clkevt_base + TIMER_CTRL) & ~TIMER_CTRL_ENABLE;
+
+	/* Disable timer */
+	writel(ctrl, clkevt_base + TIMER_CTRL);
+
+	/* Enable the timer and start the periodic tick */
+	writel(timer_reload, clkevt_base + TIMER_LOAD);
+	ctrl |= TIMER_CTRL_PERIODIC | TIMER_CTRL_ENABLE;
+	writel(ctrl, clkevt_base + TIMER_CTRL);
+	return 0;
+}
+
+static int clkevt_set_next_event(unsigned long next, struct clock_event_device *evt)
+{
+	unsigned long ctrl = readl(clkevt_base + TIMER_CTRL);
+
+	writel(ctrl & ~TIMER_CTRL_ENABLE, clkevt_base + TIMER_CTRL);
+	writel(next, clkevt_base + TIMER_LOAD);
+	writel(ctrl | TIMER_CTRL_ENABLE, clkevt_base + TIMER_CTRL);
+
+	return 0;
+}
+
+static struct clock_event_device integrator_clockevent = {
+	.name			= "timer1",
+	.features		= CLOCK_EVT_FEAT_PERIODIC |
+				  CLOCK_EVT_FEAT_ONESHOT,
+	.set_state_shutdown	= clkevt_shutdown,
+	.set_state_periodic	= clkevt_set_periodic,
+	.set_state_oneshot	= clkevt_set_oneshot,
+	.tick_resume		= clkevt_shutdown,
+	.set_next_event		= clkevt_set_next_event,
+	.rating			= 300,
+};
+
+static int integrator_clockevent_init(unsigned long inrate,
+				      void __iomem *base, int irq)
+{
+	unsigned long rate = inrate;
+	unsigned int ctrl = 0;
+	int ret;
+
+	clkevt_base = base;
+	/* Calculate and program a divisor */
+	if (rate > 0x100000 * HZ) {
+		rate /= 256;
+		ctrl |= TIMER_CTRL_DIV256;
+	} else if (rate > 0x10000 * HZ) {
+		rate /= 16;
+		ctrl |= TIMER_CTRL_DIV16;
+	}
+	timer_reload = rate / HZ;
+	writel(ctrl, clkevt_base + TIMER_CTRL);
+
+	ret = request_irq(irq, integrator_timer_interrupt,
+			  IRQF_TIMER | IRQF_IRQPOLL, "timer",
+			  &integrator_clockevent);
+	if (ret)
+		return ret;
+
+	clockevents_config_and_register(&integrator_clockevent,
+					rate,
+					1,
+					0xffffU);
+	return 0;
+}
+
+static int __init integrator_ap_timer_init_of(struct device_node *node)
+{
+	const char *path;
+	void __iomem *base;
+	int err;
+	int irq;
+	struct clk *clk;
+	unsigned long rate;
+	struct device_node *alias_node;
+
+	base = of_io_request_and_map(node, 0, "integrator-timer");
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	clk = of_clk_get(node, 0);
+	if (IS_ERR(clk)) {
+		pr_err("No clock for %pOFn\n", node);
+		return PTR_ERR(clk);
+	}
+	clk_prepare_enable(clk);
+	rate = clk_get_rate(clk);
+	writel(0, base + TIMER_CTRL);
+
+	err = of_property_read_string(of_aliases,
+				"arm,timer-primary", &path);
+	if (err) {
+		pr_warn("Failed to read property\n");
+		return err;
+	}
+
+	alias_node = of_find_node_by_path(path);
+
+	/*
+	 * The pointer is used as an identifier not as a pointer, we
+	 * can drop the refcount on the of__node immediately after
+	 * getting it.
+	 */
+	of_node_put(alias_node);
+
+	if (node == alias_node)
+		/* The primary timer lacks IRQ, use as clocksource */
+		return integrator_clocksource_init(rate, base);
+
+	err = of_property_read_string(of_aliases,
+				"arm,timer-secondary", &path);
+	if (err) {
+		pr_warn("Failed to read property\n");
+		return err;
+	}
+
+	alias_node = of_find_node_by_path(path);
+
+	of_node_put(alias_node);
+
+	if (node == alias_node) {
+		/* The secondary timer will drive the clock event */
+		irq = irq_of_parse_and_map(node, 0);
+		return integrator_clockevent_init(rate, base, irq);
+	}
+
+	pr_info("Timer @%p unused\n", base);
+	clk_disable_unprepare(clk);
+
+	return 0;
+}
+
+TIMER_OF_DECLARE(integrator_ap_timer, "arm,integrator-timer",
+		       integrator_ap_timer_init_of);