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, 219 insertions, 0 deletions

diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
new file mode 100644
index 000000000..1bf0335a1
--- /dev/null
+++ b/drivers/pps/kapi.c
@@ -0,0 +1,219 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * kernel API
+ *
+ * Copyright (C) 2005-2009   Rodolfo Giometti <giometti@linux.it>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/time.h>
+#include <linux/timex.h>
+#include <linux/spinlock.h>
+#include <linux/fs.h>
+#include <linux/pps_kernel.h>
+#include <linux/slab.h>
+
+#include "kc.h"
+
+/*
+ * Local functions
+ */
+
+static void pps_add_offset(struct pps_ktime *ts, struct pps_ktime *offset)
+{
+	ts->nsec += offset->nsec;
+	while (ts->nsec >= NSEC_PER_SEC) {
+		ts->nsec -= NSEC_PER_SEC;
+		ts->sec++;
+	}
+	while (ts->nsec < 0) {
+		ts->nsec += NSEC_PER_SEC;
+		ts->sec--;
+	}
+	ts->sec += offset->sec;
+}
+
+static void pps_echo_client_default(struct pps_device *pps, int event,
+		void *data)
+{
+	dev_info(&pps->dev, "echo %s %s\n",
+		event & PPS_CAPTUREASSERT ? "assert" : "",
+		event & PPS_CAPTURECLEAR ? "clear" : "");
+}
+
+/*
+ * Exported functions
+ */
+
+/* pps_register_source - add a PPS source in the system
+ * @info: the PPS info struct
+ * @default_params: the default PPS parameters of the new source
+ *
+ * This function is used to add a new PPS source in the system. The new
+ * source is described by info's fields and it will have, as default PPS
+ * parameters, the ones specified into default_params.
+ *
+ * The function returns, in case of success, the PPS device. Otherwise
+ * ERR_PTR(errno).
+ */
+
+struct pps_device *pps_register_source(struct pps_source_info *info,
+		int default_params)
+{
+	struct pps_device *pps;
+	int err;
+
+	/* Sanity checks */
+	if ((info->mode & default_params) != default_params) {
+		pr_err("%s: unsupported default parameters\n",
+					info->name);
+		err = -EINVAL;
+		goto pps_register_source_exit;
+	}
+	if ((info->mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
+		pr_err("%s: unspecified time format\n",
+					info->name);
+		err = -EINVAL;
+		goto pps_register_source_exit;
+	}
+
+	/* Allocate memory for the new PPS source struct */
+	pps = kzalloc_obj(struct pps_device);
+	if (pps == NULL) {
+		err = -ENOMEM;
+		goto pps_register_source_exit;
+	}
+
+	/* These initializations must be done before calling idr_alloc()
+	 * in order to avoid reces into pps_event().
+	 */
+	pps->params.api_version = PPS_API_VERS;
+	pps->params.mode = default_params;
+	pps->info = *info;
+
+	/* check for default echo function */
+	if ((pps->info.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) &&
+			pps->info.echo == NULL)
+		pps->info.echo = pps_echo_client_default;
+
+	init_waitqueue_head(&pps->queue);
+	spin_lock_init(&pps->lock);
+
+	/* Create the char device */
+	err = pps_register_cdev(pps);
+	if (err < 0) {
+		pr_err("%s: unable to create char device\n",
+					info->name);
+		goto pps_register_source_exit;
+	}
+
+	dev_dbg(&pps->dev, "new PPS source %s\n", info->name);
+
+	return pps;
+
+pps_register_source_exit:
+	pr_err("%s: unable to register source\n", info->name);
+
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL(pps_register_source);
+
+/* pps_unregister_source - remove a PPS source from the system
+ * @pps: the PPS source
+ *
+ * This function is used to remove a previously registered PPS source from
+ * the system.
+ */
+
+void pps_unregister_source(struct pps_device *pps)
+{
+	pps_kc_remove(pps);
+	pps_unregister_cdev(pps);
+
+	/* don't have to kfree(pps) here because it will be done on
+	 * device destruction */
+}
+EXPORT_SYMBOL(pps_unregister_source);
+
+/* pps_event - register a PPS event into the system
+ * @pps: the PPS device
+ * @ts: the event timestamp
+ * @event: the event type
+ * @data: userdef pointer
+ *
+ * This function is used by each PPS client in order to register a new
+ * PPS event into the system (it's usually called inside an IRQ handler).
+ *
+ * If an echo function is associated with the PPS device it will be called
+ * as:
+ *	pps->info.echo(pps, event, data);
+ */
+void pps_event(struct pps_device *pps, struct pps_event_time *ts, int event,
+		void *data)
+{
+	unsigned long flags;
+	int captured = 0;
+	struct pps_ktime ts_real = { .sec = 0, .nsec = 0, .flags = 0 };
+
+	/* check event type */
+	BUG_ON((event & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR)) == 0);
+
+	dev_dbg(&pps->dev, "PPS event at %ptSp\n", &ts->ts_real);
+
+	timespec_to_pps_ktime(&ts_real, ts->ts_real);
+
+	spin_lock_irqsave(&pps->lock, flags);
+
+	/* Must call the echo function? */
+	if ((pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)))
+		pps->info.echo(pps, event, data);
+
+	/* Check the event */
+	pps->current_mode = pps->params.mode;
+	if (event & pps->params.mode & PPS_CAPTUREASSERT) {
+		/* We have to add an offset? */
+		if (pps->params.mode & PPS_OFFSETASSERT)
+			pps_add_offset(&ts_real,
+					&pps->params.assert_off_tu);
+
+		/* Save the time stamp */
+		pps->assert_tu = ts_real;
+		pps->assert_sequence++;
+		dev_dbg(&pps->dev, "capture assert seq #%u\n",
+			pps->assert_sequence);
+
+		captured = ~0;
+	}
+	if (event & pps->params.mode & PPS_CAPTURECLEAR) {
+		/* We have to add an offset? */
+		if (pps->params.mode & PPS_OFFSETCLEAR)
+			pps_add_offset(&ts_real,
+					&pps->params.clear_off_tu);
+
+		/* Save the time stamp */
+		pps->clear_tu = ts_real;
+		pps->clear_sequence++;
+		dev_dbg(&pps->dev, "capture clear seq #%u\n",
+			pps->clear_sequence);
+
+		captured = ~0;
+	}
+
+	pps_kc_event(pps, ts, event);
+
+	/* Wake up if captured something */
+	if (captured) {
+		pps->last_ev++;
+		wake_up_interruptible_all(&pps->queue);
+
+		kill_fasync(&pps->async_queue, SIGIO, POLL_IN);
+	}
+
+	spin_unlock_irqrestore(&pps->lock, flags);
+}
+EXPORT_SYMBOL(pps_event);