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, 160 insertions, 0 deletions

diff --git a/drivers/power/reset/syscon-reboot.c b/drivers/power/reset/syscon-reboot.c
new file mode 100644
index 000000000..60e855cae
--- /dev/null
+++ b/drivers/power/reset/syscon-reboot.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Generic Syscon Reboot Driver
+ *
+ * Copyright (c) 2013, Applied Micro Circuits Corporation
+ * Author: Feng Kan <fkan@apm.com>
+ */
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/notifier.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+#include <linux/regmap.h>
+
+struct reboot_mode_bits {
+	u32 offset;
+	u32 mask;
+	u32 value;
+	bool valid;
+};
+
+struct reboot_data {
+	struct reboot_mode_bits mode_bits[REBOOT_SOFT + 1];
+	struct reboot_mode_bits catchall;
+};
+
+struct syscon_reboot_context {
+	struct regmap *map;
+
+	const struct reboot_data *rd; /* from of match data, if any */
+	struct reboot_mode_bits catchall; /* from DT */
+
+	struct notifier_block restart_handler;
+};
+
+static int syscon_restart_handle(struct notifier_block *this,
+					unsigned long mode, void *cmd)
+{
+	struct syscon_reboot_context *ctx =
+			container_of(this, struct syscon_reboot_context,
+					restart_handler);
+	const struct reboot_mode_bits *mode_bits;
+
+	if (ctx->rd) {
+		if (mode < ARRAY_SIZE(ctx->rd->mode_bits) &&
+		    ctx->rd->mode_bits[mode].valid)
+			mode_bits = &ctx->rd->mode_bits[mode];
+		else
+			mode_bits = &ctx->rd->catchall;
+	} else {
+		mode_bits = &ctx->catchall;
+	}
+
+	/* Issue the reboot */
+	regmap_update_bits(ctx->map, mode_bits->offset, mode_bits->mask,
+			   mode_bits->value);
+
+	mdelay(1000);
+
+	pr_emerg("Unable to restart system\n");
+	return NOTIFY_DONE;
+}
+
+static int syscon_reboot_probe(struct platform_device *pdev)
+{
+	struct syscon_reboot_context *ctx;
+	struct device *dev = &pdev->dev;
+	u32 priority;
+	int err;
+
+	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->map = syscon_regmap_lookup_by_phandle(dev->of_node, "regmap");
+	if (IS_ERR(ctx->map)) {
+		ctx->map = syscon_node_to_regmap(dev->parent->of_node);
+		if (IS_ERR(ctx->map))
+			return PTR_ERR(ctx->map);
+	}
+
+	if (of_property_read_u32(pdev->dev.of_node, "priority", &priority))
+		priority = 192;
+
+	ctx->rd = of_device_get_match_data(dev);
+	if (!ctx->rd) {
+		int mask_err, value_err;
+
+		if (of_property_read_u32(pdev->dev.of_node, "offset",
+					 &ctx->catchall.offset) &&
+		    of_property_read_u32(pdev->dev.of_node, "reg",
+					 &ctx->catchall.offset))
+			return -EINVAL;
+
+		value_err = of_property_read_u32(pdev->dev.of_node, "value",
+						 &ctx->catchall.value);
+		mask_err = of_property_read_u32(pdev->dev.of_node, "mask",
+						&ctx->catchall.mask);
+		if (value_err && mask_err) {
+			dev_err(dev, "unable to read 'value' and 'mask'");
+			return -EINVAL;
+		}
+
+		if (value_err) {
+			/* support old binding */
+			ctx->catchall.value = ctx->catchall.mask;
+			ctx->catchall.mask = 0xFFFFFFFF;
+		} else if (mask_err) {
+			/* support value without mask */
+			ctx->catchall.mask = 0xFFFFFFFF;
+		}
+	}
+
+	ctx->restart_handler.notifier_call = syscon_restart_handle;
+	ctx->restart_handler.priority = priority;
+	err = register_restart_handler(&ctx->restart_handler);
+	if (err)
+		dev_err(dev, "can't register restart notifier (err=%d)\n", err);
+
+	return err;
+}
+
+static const struct reboot_data gs101_reboot_data = {
+	.mode_bits = {
+		[REBOOT_WARM] = {
+			.offset = 0x3a00, /* SYSTEM_CONFIGURATION */
+			.mask = 0x00000002, /* SWRESET_SYSTEM */
+			.value = 0x00000002,
+			.valid = true,
+		},
+		[REBOOT_SOFT] = {
+			.offset = 0x3a00, /* SYSTEM_CONFIGURATION */
+			.mask = 0x00000002, /* SWRESET_SYSTEM */
+			.value = 0x00000002,
+			.valid = true,
+		},
+	},
+	.catchall = {
+		.offset = 0x3e9c, /* PAD_CTRL_PWR_HOLD */
+		.mask = 0x00000100,
+		.value = 0x00000000,
+	},
+};
+
+static const struct of_device_id syscon_reboot_of_match[] = {
+	{ .compatible = "google,gs101-reboot", .data = &gs101_reboot_data  },
+	{ .compatible = "syscon-reboot" },
+	{}
+};
+
+static struct platform_driver syscon_reboot_driver = {
+	.probe = syscon_reboot_probe,
+	.driver = {
+		.name = "syscon-reboot",
+		.of_match_table = syscon_reboot_of_match,
+	},
+};
+builtin_platform_driver(syscon_reboot_driver);