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, 157 insertions, 0 deletions

diff --git a/drivers/iio/buffer/industrialio-buffer-cb.c b/drivers/iio/buffer/industrialio-buffer-cb.c
new file mode 100644
index 000000000..b58263bcf
--- /dev/null
+++ b/drivers/iio/buffer/industrialio-buffer-cb.c
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* The industrial I/O callback buffer
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer_impl.h>
+#include <linux/iio/consumer.h>
+
+struct iio_cb_buffer {
+	struct iio_buffer buffer;
+	/* Must be safe to call from any context (e.g. must not sleep). */
+	int (*cb)(const void *data, void *private);
+	void *private;
+	struct iio_channel *channels;
+	struct iio_dev *indio_dev;
+};
+
+static struct iio_cb_buffer *buffer_to_cb_buffer(struct iio_buffer *buffer)
+{
+	return container_of(buffer, struct iio_cb_buffer, buffer);
+}
+
+static int iio_buffer_cb_store_to(struct iio_buffer *buffer, const void *data)
+{
+	struct iio_cb_buffer *cb_buff = buffer_to_cb_buffer(buffer);
+	return cb_buff->cb(data, cb_buff->private);
+}
+
+static void iio_buffer_cb_release(struct iio_buffer *buffer)
+{
+	struct iio_cb_buffer *cb_buff = buffer_to_cb_buffer(buffer);
+
+	bitmap_free(cb_buff->buffer.scan_mask);
+	kfree(cb_buff);
+}
+
+static const struct iio_buffer_access_funcs iio_cb_access = {
+	.store_to = &iio_buffer_cb_store_to,
+	.release = &iio_buffer_cb_release,
+
+	.modes = INDIO_BUFFER_SOFTWARE | INDIO_BUFFER_TRIGGERED,
+};
+
+struct iio_cb_buffer *iio_channel_get_all_cb(struct device *dev,
+					     int (*cb)(const void *data,
+						       void *private),
+					     void *private)
+{
+	int ret;
+	struct iio_cb_buffer *cb_buff;
+	struct iio_channel *chan;
+
+	if (!cb) {
+		dev_err(dev, "Invalid arguments: A callback must be provided!\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	cb_buff = kzalloc_obj(*cb_buff);
+	if (cb_buff == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	iio_buffer_init(&cb_buff->buffer);
+
+	cb_buff->private = private;
+	cb_buff->cb = cb;
+	cb_buff->buffer.access = &iio_cb_access;
+
+	cb_buff->channels = iio_channel_get_all(dev);
+	if (IS_ERR(cb_buff->channels)) {
+		ret = PTR_ERR(cb_buff->channels);
+		goto error_free_cb_buff;
+	}
+
+	cb_buff->indio_dev = cb_buff->channels[0].indio_dev;
+	cb_buff->buffer.scan_mask = bitmap_zalloc(iio_get_masklength(cb_buff->indio_dev),
+						  GFP_KERNEL);
+	if (cb_buff->buffer.scan_mask == NULL) {
+		ret = -ENOMEM;
+		goto error_release_channels;
+	}
+	chan = &cb_buff->channels[0];
+	while (chan->indio_dev) {
+		if (chan->indio_dev != cb_buff->indio_dev) {
+			ret = -EINVAL;
+			goto error_free_scan_mask;
+		}
+		set_bit(chan->channel->scan_index,
+			cb_buff->buffer.scan_mask);
+		chan++;
+	}
+
+	return cb_buff;
+
+error_free_scan_mask:
+	bitmap_free(cb_buff->buffer.scan_mask);
+error_release_channels:
+	iio_channel_release_all(cb_buff->channels);
+error_free_cb_buff:
+	kfree(cb_buff);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(iio_channel_get_all_cb);
+
+int iio_channel_cb_set_buffer_watermark(struct iio_cb_buffer *cb_buff,
+					size_t watermark)
+{
+	if (!watermark)
+		return -EINVAL;
+	cb_buff->buffer.watermark = watermark;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(iio_channel_cb_set_buffer_watermark);
+
+int iio_channel_start_all_cb(struct iio_cb_buffer *cb_buff)
+{
+	return iio_update_buffers(cb_buff->indio_dev, &cb_buff->buffer,
+				  NULL);
+}
+EXPORT_SYMBOL_GPL(iio_channel_start_all_cb);
+
+void iio_channel_stop_all_cb(struct iio_cb_buffer *cb_buff)
+{
+	iio_update_buffers(cb_buff->indio_dev, NULL, &cb_buff->buffer);
+}
+EXPORT_SYMBOL_GPL(iio_channel_stop_all_cb);
+
+void iio_channel_release_all_cb(struct iio_cb_buffer *cb_buff)
+{
+	iio_channel_release_all(cb_buff->channels);
+	iio_buffer_put(&cb_buff->buffer);
+}
+EXPORT_SYMBOL_GPL(iio_channel_release_all_cb);
+
+struct iio_channel
+*iio_channel_cb_get_channels(const struct iio_cb_buffer *cb_buffer)
+{
+	return cb_buffer->channels;
+}
+EXPORT_SYMBOL_GPL(iio_channel_cb_get_channels);
+
+struct iio_dev
+*iio_channel_cb_get_iio_dev(const struct iio_cb_buffer *cb_buffer)
+{
+	return cb_buffer->indio_dev;
+}
+EXPORT_SYMBOL_GPL(iio_channel_cb_get_iio_dev);
+
+MODULE_AUTHOR("Jonathan Cameron <jic23@kernel.org>");
+MODULE_DESCRIPTION("Industrial I/O callback buffer");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("IIO_CONSUMER");