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, 279 insertions, 0 deletions

diff --git a/drivers/misc/atmel-ssc.c b/drivers/misc/atmel-ssc.c
new file mode 100644
index 000000000..35a196341
--- /dev/null
+++ b/drivers/misc/atmel-ssc.c
@@ -0,0 +1,279 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Atmel SSC driver
+ *
+ * Copyright (C) 2007 Atmel Corporation
+ */
+
+#include <linux/platform_device.h>
+#include <linux/list.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/mutex.h>
+#include <linux/atmel-ssc.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+
+#include <linux/of.h>
+
+#include "../../sound/soc/atmel/atmel_ssc_dai.h"
+
+/* Serialize access to ssc_list and user count */
+static DEFINE_MUTEX(user_lock);
+static LIST_HEAD(ssc_list);
+
+struct ssc_device *ssc_request(unsigned int ssc_num)
+{
+	int ssc_valid = 0;
+	struct ssc_device *ssc;
+
+	mutex_lock(&user_lock);
+	list_for_each_entry(ssc, &ssc_list, list) {
+		if (ssc->pdev->dev.of_node) {
+			if (of_alias_get_id(ssc->pdev->dev.of_node, "ssc")
+				== ssc_num) {
+				ssc->pdev->id = ssc_num;
+				ssc_valid = 1;
+				break;
+			}
+		} else if (ssc->pdev->id == ssc_num) {
+			ssc_valid = 1;
+			break;
+		}
+	}
+
+	if (!ssc_valid) {
+		mutex_unlock(&user_lock);
+		pr_err("ssc: ssc%d platform device is missing\n", ssc_num);
+		return ERR_PTR(-ENODEV);
+	}
+
+	if (ssc->user) {
+		mutex_unlock(&user_lock);
+		dev_dbg(&ssc->pdev->dev, "module busy\n");
+		return ERR_PTR(-EBUSY);
+	}
+	ssc->user++;
+	mutex_unlock(&user_lock);
+
+	clk_prepare(ssc->clk);
+
+	return ssc;
+}
+EXPORT_SYMBOL(ssc_request);
+
+void ssc_free(struct ssc_device *ssc)
+{
+	bool disable_clk = true;
+
+	mutex_lock(&user_lock);
+	if (ssc->user)
+		ssc->user--;
+	else {
+		disable_clk = false;
+		dev_dbg(&ssc->pdev->dev, "device already free\n");
+	}
+	mutex_unlock(&user_lock);
+
+	if (disable_clk)
+		clk_unprepare(ssc->clk);
+}
+EXPORT_SYMBOL(ssc_free);
+
+static struct atmel_ssc_platform_data at91rm9200_config = {
+	.use_dma = 0,
+	.has_fslen_ext = 0,
+};
+
+static struct atmel_ssc_platform_data at91sam9rl_config = {
+	.use_dma = 0,
+	.has_fslen_ext = 1,
+};
+
+static struct atmel_ssc_platform_data at91sam9g45_config = {
+	.use_dma = 1,
+	.has_fslen_ext = 1,
+};
+
+static const struct platform_device_id atmel_ssc_devtypes[] = {
+	{
+		.name = "at91rm9200_ssc",
+		.driver_data = (unsigned long) &at91rm9200_config,
+	}, {
+		.name = "at91sam9rl_ssc",
+		.driver_data = (unsigned long) &at91sam9rl_config,
+	}, {
+		.name = "at91sam9g45_ssc",
+		.driver_data = (unsigned long) &at91sam9g45_config,
+	}, {
+		/* sentinel */
+	}
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id atmel_ssc_dt_ids[] = {
+	{
+		.compatible = "atmel,at91rm9200-ssc",
+		.data = &at91rm9200_config,
+	}, {
+		.compatible = "atmel,at91sam9rl-ssc",
+		.data = &at91sam9rl_config,
+	}, {
+		.compatible = "atmel,at91sam9g45-ssc",
+		.data = &at91sam9g45_config,
+	}, {
+		/* sentinel */
+	}
+};
+MODULE_DEVICE_TABLE(of, atmel_ssc_dt_ids);
+#endif
+
+static inline const struct atmel_ssc_platform_data *
+	atmel_ssc_get_driver_data(struct platform_device *pdev)
+{
+	if (pdev->dev.of_node) {
+		const struct of_device_id *match;
+		match = of_match_node(atmel_ssc_dt_ids, pdev->dev.of_node);
+		if (match == NULL)
+			return NULL;
+		return match->data;
+	}
+
+	return (struct atmel_ssc_platform_data *)
+		platform_get_device_id(pdev)->driver_data;
+}
+
+#ifdef CONFIG_SND_ATMEL_SOC_SSC
+static int ssc_sound_dai_probe(struct ssc_device *ssc)
+{
+	struct device_node *np = ssc->pdev->dev.of_node;
+	int ret;
+	int id;
+
+	ssc->sound_dai = false;
+
+	if (!of_property_present(np, "#sound-dai-cells"))
+		return 0;
+
+	id = of_alias_get_id(np, "ssc");
+	if (id < 0)
+		return id;
+
+	ret = atmel_ssc_set_audio(id);
+	ssc->sound_dai = !ret;
+
+	return ret;
+}
+
+static void ssc_sound_dai_remove(struct ssc_device *ssc)
+{
+	if (!ssc->sound_dai)
+		return;
+
+	atmel_ssc_put_audio(of_alias_get_id(ssc->pdev->dev.of_node, "ssc"));
+}
+#else
+static inline int ssc_sound_dai_probe(struct ssc_device *ssc)
+{
+	if (of_property_present(ssc->pdev->dev.of_node, "#sound-dai-cells"))
+		return -ENOTSUPP;
+
+	return 0;
+}
+
+static inline void ssc_sound_dai_remove(struct ssc_device *ssc)
+{
+}
+#endif
+
+static int ssc_probe(struct platform_device *pdev)
+{
+	struct resource *regs;
+	struct ssc_device *ssc;
+	const struct atmel_ssc_platform_data *plat_dat;
+
+	ssc = devm_kzalloc(&pdev->dev, sizeof(struct ssc_device), GFP_KERNEL);
+	if (!ssc) {
+		dev_dbg(&pdev->dev, "out of memory\n");
+		return -ENOMEM;
+	}
+
+	ssc->pdev = pdev;
+
+	plat_dat = atmel_ssc_get_driver_data(pdev);
+	if (!plat_dat)
+		return -ENODEV;
+	ssc->pdata = (struct atmel_ssc_platform_data *)plat_dat;
+
+	if (pdev->dev.of_node) {
+		struct device_node *np = pdev->dev.of_node;
+		ssc->clk_from_rk_pin =
+			of_property_read_bool(np, "atmel,clk-from-rk-pin");
+	}
+
+	ssc->regs = devm_platform_get_and_ioremap_resource(pdev, 0, &regs);
+	if (IS_ERR(ssc->regs))
+		return PTR_ERR(ssc->regs);
+
+	ssc->phybase = regs->start;
+
+	ssc->clk = devm_clk_get(&pdev->dev, "pclk");
+	if (IS_ERR(ssc->clk)) {
+		dev_dbg(&pdev->dev, "no pclk clock defined\n");
+		return -ENXIO;
+	}
+
+	/* disable all interrupts */
+	clk_prepare_enable(ssc->clk);
+	ssc_writel(ssc->regs, IDR, -1);
+	ssc_readl(ssc->regs, SR);
+	clk_disable_unprepare(ssc->clk);
+
+	ssc->irq = platform_get_irq(pdev, 0);
+	if (ssc->irq < 0) {
+		dev_dbg(&pdev->dev, "could not get irq\n");
+		return ssc->irq;
+	}
+
+	mutex_lock(&user_lock);
+	list_add_tail(&ssc->list, &ssc_list);
+	mutex_unlock(&user_lock);
+
+	platform_set_drvdata(pdev, ssc);
+
+	dev_info(&pdev->dev, "Atmel SSC device at 0x%p (irq %d)\n",
+			ssc->regs, ssc->irq);
+
+	if (ssc_sound_dai_probe(ssc))
+		dev_err(&pdev->dev, "failed to auto-setup ssc for audio\n");
+
+	return 0;
+}
+
+static void ssc_remove(struct platform_device *pdev)
+{
+	struct ssc_device *ssc = platform_get_drvdata(pdev);
+
+	ssc_sound_dai_remove(ssc);
+
+	mutex_lock(&user_lock);
+	list_del(&ssc->list);
+	mutex_unlock(&user_lock);
+}
+
+static struct platform_driver ssc_driver = {
+	.driver		= {
+		.name		= "ssc",
+		.of_match_table	= of_match_ptr(atmel_ssc_dt_ids),
+	},
+	.id_table	= atmel_ssc_devtypes,
+	.probe		= ssc_probe,
+	.remove		= ssc_remove,
+};
+module_platform_driver(ssc_driver);
+
+MODULE_AUTHOR("Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>");
+MODULE_DESCRIPTION("SSC driver for Atmel AT91");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ssc");