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, 134 insertions, 0 deletions

diff --git a/drivers/ptp/ptp_vmw.c b/drivers/ptp/ptp_vmw.c
new file mode 100644
index 000000000..14fc587d0
--- /dev/null
+++ b/drivers/ptp/ptp_vmw.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+/*
+ * Copyright (C) 2020 VMware, Inc., Palo Alto, CA., USA
+ *
+ * PTP clock driver for VMware precision clock virtual device.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/acpi.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/ptp_clock_kernel.h>
+#include <asm/hypervisor.h>
+#include <asm/vmware.h>
+
+#define VMWARE_CMD_PCLK(nr) ((nr << 16) | 97)
+#define VMWARE_CMD_PCLK_GETTIME VMWARE_CMD_PCLK(0)
+
+static struct ptp_clock *ptp_vmw_clock;
+
+
+static int ptp_vmw_pclk_read(u64 *ns)
+{
+	u32 ret, nsec_hi, nsec_lo;
+
+	ret = vmware_hypercall3(VMWARE_CMD_PCLK_GETTIME, 0,
+				&nsec_hi, &nsec_lo);
+	if (ret == 0)
+		*ns = ((u64)nsec_hi << 32) | nsec_lo;
+	return ret;
+}
+
+/*
+ * PTP clock ops.
+ */
+
+static int ptp_vmw_adjtime(struct ptp_clock_info *info, s64 delta)
+{
+	return -EOPNOTSUPP;
+}
+
+static int ptp_vmw_adjfine(struct ptp_clock_info *info, long delta)
+{
+	return -EOPNOTSUPP;
+}
+
+static int ptp_vmw_gettime(struct ptp_clock_info *info, struct timespec64 *ts)
+{
+	u64 ns;
+
+	if (ptp_vmw_pclk_read(&ns) != 0)
+		return -EIO;
+	*ts = ns_to_timespec64(ns);
+	return 0;
+}
+
+static int ptp_vmw_settime(struct ptp_clock_info *info,
+			  const struct timespec64 *ts)
+{
+	return -EOPNOTSUPP;
+}
+
+static int ptp_vmw_enable(struct ptp_clock_info *info,
+			 struct ptp_clock_request *request, int on)
+{
+	return -EOPNOTSUPP;
+}
+
+static struct ptp_clock_info ptp_vmw_clock_info = {
+	.owner		= THIS_MODULE,
+	.name		= "ptp_vmw",
+	.max_adj	= 0,
+	.adjtime	= ptp_vmw_adjtime,
+	.adjfine	= ptp_vmw_adjfine,
+	.gettime64	= ptp_vmw_gettime,
+	.settime64	= ptp_vmw_settime,
+	.enable		= ptp_vmw_enable,
+};
+
+/*
+ * ACPI driver ops for VMware "precision clock" virtual device.
+ */
+
+static int ptp_vmw_acpi_probe(struct platform_device *pdev)
+{
+	ptp_vmw_clock = ptp_clock_register(&ptp_vmw_clock_info, NULL);
+	if (IS_ERR(ptp_vmw_clock)) {
+		pr_err("failed to register ptp clock\n");
+		return PTR_ERR(ptp_vmw_clock);
+	}
+	return 0;
+}
+
+static void ptp_vmw_acpi_remove(struct platform_device *pdev)
+{
+	ptp_clock_unregister(ptp_vmw_clock);
+}
+
+static const struct acpi_device_id ptp_vmw_acpi_device_ids[] = {
+	{ "VMW0005", 0 },
+	{ "", 0 },
+};
+
+MODULE_DEVICE_TABLE(acpi, ptp_vmw_acpi_device_ids);
+
+static struct platform_driver ptp_vmw_acpi_driver = {
+	.probe = ptp_vmw_acpi_probe,
+	.remove = ptp_vmw_acpi_remove,
+	.driver = {
+		.name = "ptp_vmw_acpi",
+		.acpi_match_table = ptp_vmw_acpi_device_ids,
+	},
+};
+
+static int __init ptp_vmw_init(void)
+{
+	if (x86_hyper_type != X86_HYPER_VMWARE)
+		return -1;
+	return platform_driver_register(&ptp_vmw_acpi_driver);
+}
+
+static void __exit ptp_vmw_exit(void)
+{
+	platform_driver_unregister(&ptp_vmw_acpi_driver);
+}
+
+module_init(ptp_vmw_init);
+module_exit(ptp_vmw_exit);
+
+MODULE_DESCRIPTION("VMware virtual PTP clock driver");
+MODULE_AUTHOR("VMware, Inc.");
+MODULE_LICENSE("Dual BSD/GPL");