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, 218 insertions, 0 deletions

diff --git a/drivers/mtd/maps/plat-ram.c b/drivers/mtd/maps/plat-ram.c
new file mode 100644
index 000000000..816111031
--- /dev/null
+++ b/drivers/mtd/maps/plat-ram.c
@@ -0,0 +1,218 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* drivers/mtd/maps/plat-ram.c
+ *
+ * (c) 2004-2005 Simtec Electronics
+ *	http://www.simtec.co.uk/products/SWLINUX/
+ *	Ben Dooks <ben@simtec.co.uk>
+ *
+ * Generic platform device based RAM map
+*/
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/ioport.h>
+#include <linux/device.h>
+#include <linux/slab.h>
+#include <linux/platform_device.h>
+
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/map.h>
+#include <linux/mtd/partitions.h>
+#include <linux/mtd/plat-ram.h>
+
+#include <asm/io.h>
+
+/* private structure for each mtd platform ram device created */
+
+struct platram_info {
+	struct device		*dev;
+	struct mtd_info		*mtd;
+	struct map_info		 map;
+	struct platdata_mtd_ram	*pdata;
+};
+
+/* to_platram_info()
+ *
+ * device private data to struct platram_info conversion
+*/
+
+static inline struct platram_info *to_platram_info(struct platform_device *dev)
+{
+	return platform_get_drvdata(dev);
+}
+
+/* platram_setrw
+ *
+ * call the platform device's set rw/ro control
+ *
+ * to = 0 => read-only
+ *    = 1 => read-write
+*/
+
+static inline void platram_setrw(struct platram_info *info, int to)
+{
+	if (info->pdata == NULL)
+		return;
+
+	if (info->pdata->set_rw != NULL)
+		(info->pdata->set_rw)(info->dev, to);
+}
+
+/* platram_remove
+ *
+ * called to remove the device from the driver's control
+*/
+
+static void platram_remove(struct platform_device *pdev)
+{
+	struct platram_info *info = to_platram_info(pdev);
+
+	dev_dbg(&pdev->dev, "removing device\n");
+
+	if (info == NULL)
+		return;
+
+	if (info->mtd) {
+		mtd_device_unregister(info->mtd);
+		map_destroy(info->mtd);
+	}
+
+	/* ensure ram is left read-only */
+
+	platram_setrw(info, PLATRAM_RO);
+
+	kfree(info);
+}
+
+/* platram_probe
+ *
+ * called from device drive system when a device matching our
+ * driver is found.
+*/
+
+static int platram_probe(struct platform_device *pdev)
+{
+	struct platdata_mtd_ram	*pdata;
+	struct platram_info *info;
+	struct resource *res;
+	int err = 0;
+
+	dev_dbg(&pdev->dev, "probe entered\n");
+
+	if (dev_get_platdata(&pdev->dev) == NULL) {
+		dev_err(&pdev->dev, "no platform data supplied\n");
+		err = -ENOENT;
+		goto exit_error;
+	}
+
+	pdata = dev_get_platdata(&pdev->dev);
+
+	info = kzalloc_obj(*info);
+	if (info == NULL) {
+		err = -ENOMEM;
+		goto exit_error;
+	}
+
+	platform_set_drvdata(pdev, info);
+
+	info->dev = &pdev->dev;
+	info->pdata = pdata;
+
+	/* get the resource for the memory mapping */
+	info->map.virt = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
+	if (IS_ERR(info->map.virt)) {
+		err = PTR_ERR(info->map.virt);
+		goto exit_free;
+	}
+
+	dev_dbg(&pdev->dev, "got platform resource %p (0x%llx)\n", res,
+		(unsigned long long)res->start);
+
+	/* setup map parameters */
+
+	info->map.phys = res->start;
+	info->map.size = resource_size(res);
+	info->map.name = pdata->mapname != NULL ?
+			(char *)pdata->mapname : (char *)pdev->name;
+	info->map.bankwidth = pdata->bankwidth;
+
+	dev_dbg(&pdev->dev, "virt %p, %lu bytes\n", info->map.virt, info->map.size);
+
+	simple_map_init(&info->map);
+
+	dev_dbg(&pdev->dev, "initialised map, probing for mtd\n");
+
+	/* probe for the right mtd map driver
+	 * supplied by the platform_data struct */
+
+	if (pdata->map_probes) {
+		const char * const *map_probes = pdata->map_probes;
+
+		for ( ; !info->mtd && *map_probes; map_probes++)
+			info->mtd = do_map_probe(*map_probes , &info->map);
+	}
+	/* fallback to map_ram */
+	else
+		info->mtd = do_map_probe("map_ram", &info->map);
+
+	if (info->mtd == NULL) {
+		dev_err(&pdev->dev, "failed to probe for map_ram\n");
+		err = -ENOMEM;
+		goto exit_free;
+	}
+
+	info->mtd->dev.parent = &pdev->dev;
+
+	platram_setrw(info, PLATRAM_RW);
+
+	/* check to see if there are any available partitions, or whether
+	 * to add this device whole */
+
+	err = mtd_device_parse_register(info->mtd, pdata->probes, NULL,
+					pdata->partitions,
+					pdata->nr_partitions);
+	if (err) {
+		dev_err(&pdev->dev, "failed to register mtd device\n");
+		goto exit_free;
+	}
+
+	dev_info(&pdev->dev, "registered mtd device\n");
+
+	if (pdata->nr_partitions) {
+		/* add the whole device. */
+		err = mtd_device_register(info->mtd, NULL, 0);
+		if (err) {
+			dev_err(&pdev->dev,
+				"failed to register the entire device\n");
+			goto exit_free;
+		}
+	}
+
+	return 0;
+
+ exit_free:
+	platram_remove(pdev);
+ exit_error:
+	return err;
+}
+
+/* device driver info */
+
+/* work with hotplug and coldplug */
+MODULE_ALIAS("platform:mtd-ram");
+
+static struct platform_driver platram_driver = {
+	.probe		= platram_probe,
+	.remove		= platram_remove,
+	.driver		= {
+		.name	= "mtd-ram",
+	},
+};
+
+module_platform_driver(platram_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Ben Dooks <ben@simtec.co.uk>");
+MODULE_DESCRIPTION("MTD platform RAM map driver");