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>

3 files changed, 146 insertions, 0 deletions

diff --git a/drivers/soc/vt8500/Kconfig b/drivers/soc/vt8500/Kconfig
new file mode 100644
index 000000000..b4cc0ba11
--- /dev/null
+++ b/drivers/soc/vt8500/Kconfig
@@ -0,0 +1,19 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+if ARCH_VT8500 || COMPILE_TEST
+
+menu "VIA/WonderMedia SoC drivers"
+
+config WMT_SOCINFO
+	bool "VIA/WonderMedia SoC Information driver"
+	default ARCH_VT8500
+	select SOC_BUS
+	help
+	  Say yes to support decoding of VIA/WonderMedia system configuration
+	  register information. This currently includes just the chip ID register
+	  which helps identify the exact hardware revision of the SoC the kernel
+	  is running on (to know if any revision-specific quirks are required)
+
+endmenu
+
+endif
diff --git a/drivers/soc/vt8500/Makefile b/drivers/soc/vt8500/Makefile
new file mode 100644
index 000000000..05964c5f2
--- /dev/null
+++ b/drivers/soc/vt8500/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_WMT_SOCINFO)	+= wmt-socinfo.o
diff --git a/drivers/soc/vt8500/wmt-socinfo.c b/drivers/soc/vt8500/wmt-socinfo.c
new file mode 100644
index 000000000..461f8c1ae
--- /dev/null
+++ b/drivers/soc/vt8500/wmt-socinfo.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2025 Alexey Charkov <alchark@gmail.com>
+ * Based on aspeed-socinfo.c
+ */
+
+#include <linux/dev_printk.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/sys_soc.h>
+
+static const struct {
+	const char *name;
+	const u32 id;
+} chip_id_table[] = {
+	/* VIA */
+	{ "VT8420", 0x3300 },
+	{ "VT8430", 0x3357 },
+	{ "VT8500", 0x3400 },
+
+	/* WonderMedia */
+	{ "WM8425", 0x3429 },
+	{ "WM8435", 0x3437 },
+	{ "WM8440", 0x3451 },
+	{ "WM8505", 0x3426 },
+	{ "WM8650", 0x3465 },
+	{ "WM8750", 0x3445 },
+	{ "WM8850", 0x3481 },
+	{ "WM8880", 0x3498 },
+};
+
+static const char *sccid_to_name(u32 sccid)
+{
+	u32 id = sccid >> 16;
+	unsigned int i;
+
+	for (i = 0 ; i < ARRAY_SIZE(chip_id_table) ; ++i) {
+		if (chip_id_table[i].id == id)
+			return chip_id_table[i].name;
+	}
+
+	return "Unknown";
+}
+
+static int wmt_socinfo_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct soc_device_attribute *attrs;
+	struct soc_device *soc_dev;
+	char letter, digit;
+	void __iomem *reg;
+	u32 sccid;
+
+	reg = devm_of_iomap(&pdev->dev, np, 0, NULL);
+	if (IS_ERR(reg))
+		return PTR_ERR(reg);
+
+	sccid = readl(reg);
+
+	attrs = devm_kzalloc(&pdev->dev, sizeof(*attrs), GFP_KERNEL);
+	if (!attrs)
+		return -ENOMEM;
+
+	/*
+	 * Machine: VIA APC Rock
+	 * Family: WM8850
+	 * Revision: A2
+	 * SoC ID: raw silicon revision id (34810103 in hexadecimal)
+	 */
+
+	attrs->family = sccid_to_name(sccid);
+
+	letter = (sccid >> 8) & 0xf;
+	letter = (letter - 1) + 'A';
+	digit = sccid & 0xff;
+	digit = (digit - 1) + '0';
+	attrs->revision = devm_kasprintf(&pdev->dev, GFP_KERNEL,
+					 "%c%c", letter, digit);
+
+	attrs->soc_id = devm_kasprintf(&pdev->dev, GFP_KERNEL, "%08x", sccid);
+
+	if (!attrs->revision || !attrs->soc_id)
+		return -ENOMEM;
+
+	soc_dev = soc_device_register(attrs);
+	if (IS_ERR(soc_dev))
+		return PTR_ERR(soc_dev);
+
+	dev_info(&pdev->dev,
+		 "VIA/WonderMedia %s rev %s (%s)\n",
+		 attrs->family,
+		 attrs->revision,
+		 attrs->soc_id);
+
+	platform_set_drvdata(pdev, soc_dev);
+	return 0;
+}
+
+static void wmt_socinfo_remove(struct platform_device *pdev)
+{
+	struct soc_device *soc_dev = platform_get_drvdata(pdev);
+
+	soc_device_unregister(soc_dev);
+}
+
+static const struct of_device_id wmt_socinfo_ids[] = {
+	{ .compatible = "via,vt8500-scc-id" },
+	{ /* Sentinel */ },
+};
+
+static struct platform_driver wmt_socinfo = {
+	.probe = wmt_socinfo_probe,
+	.remove = wmt_socinfo_remove,
+	.driver = {
+		.name = "wmt-socinfo",
+		.of_match_table = wmt_socinfo_ids,
+	},
+};
+module_platform_driver(wmt_socinfo);
+
+MODULE_AUTHOR("Alexey Charkov <alchark@gmail.com>");
+MODULE_DESCRIPTION("VIA/WonderMedia socinfo driver");
+MODULE_LICENSE("GPL");