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, 189 insertions, 0 deletions

diff --git a/drivers/firmware/imx/imx-dsp.c b/drivers/firmware/imx/imx-dsp.c
new file mode 100644
index 000000000..ed79e8231
--- /dev/null
+++ b/drivers/firmware/imx/imx-dsp.c
@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2019 NXP
+ *  Author: Daniel Baluta <daniel.baluta@nxp.com>
+ *
+ * Implementation of the DSP IPC interface (host side)
+ */
+
+#include <linux/firmware/imx/dsp.h>
+#include <linux/kernel.h>
+#include <linux/mailbox_client.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+/*
+ * imx_dsp_ring_doorbell - triggers an interrupt on the other side (DSP)
+ *
+ * @dsp: DSP IPC handle
+ * @chan_idx: index of the channel where to trigger the interrupt
+ *
+ * Returns non-negative value for success, negative value for error
+ */
+int imx_dsp_ring_doorbell(struct imx_dsp_ipc *ipc, unsigned int idx)
+{
+	int ret;
+	struct imx_dsp_chan *dsp_chan;
+
+	if (idx >= DSP_MU_CHAN_NUM)
+		return -EINVAL;
+
+	dsp_chan = &ipc->chans[idx];
+	ret = mbox_send_message(dsp_chan->ch, NULL);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL(imx_dsp_ring_doorbell);
+
+/*
+ * imx_dsp_handle_rx - rx callback used by imx mailbox
+ *
+ * @c: mbox client
+ * @msg: message received
+ *
+ * Users of DSP IPC will need to privde handle_reply and handle_request
+ * callbacks.
+ */
+static void imx_dsp_handle_rx(struct mbox_client *c, void *msg)
+{
+	struct imx_dsp_chan *chan = container_of(c, struct imx_dsp_chan, cl);
+
+	if (chan->idx == 0) {
+		chan->ipc->ops->handle_reply(chan->ipc);
+	} else {
+		chan->ipc->ops->handle_request(chan->ipc);
+		imx_dsp_ring_doorbell(chan->ipc, 1);
+	}
+}
+
+struct mbox_chan *imx_dsp_request_channel(struct imx_dsp_ipc *dsp_ipc, int idx)
+{
+	struct imx_dsp_chan *dsp_chan;
+
+	if (idx >= DSP_MU_CHAN_NUM)
+		return ERR_PTR(-EINVAL);
+
+	dsp_chan = &dsp_ipc->chans[idx];
+	dsp_chan->ch = mbox_request_channel_byname(&dsp_chan->cl, dsp_chan->name);
+	return dsp_chan->ch;
+}
+EXPORT_SYMBOL(imx_dsp_request_channel);
+
+void imx_dsp_free_channel(struct imx_dsp_ipc *dsp_ipc, int idx)
+{
+	struct imx_dsp_chan *dsp_chan;
+
+	if (idx >= DSP_MU_CHAN_NUM)
+		return;
+
+	dsp_chan = &dsp_ipc->chans[idx];
+	mbox_free_channel(dsp_chan->ch);
+}
+EXPORT_SYMBOL(imx_dsp_free_channel);
+
+static int imx_dsp_setup_channels(struct imx_dsp_ipc *dsp_ipc)
+{
+	struct device *dev = dsp_ipc->dev;
+	struct imx_dsp_chan *dsp_chan;
+	struct mbox_client *cl;
+	char *chan_name;
+	int ret;
+	int i, j;
+
+	for (i = 0; i < DSP_MU_CHAN_NUM; i++) {
+		if (i < 2)
+			chan_name = kasprintf(GFP_KERNEL, "txdb%d", i);
+		else
+			chan_name = kasprintf(GFP_KERNEL, "rxdb%d", i - 2);
+
+		if (!chan_name)
+			return -ENOMEM;
+
+		dsp_chan = &dsp_ipc->chans[i];
+		dsp_chan->name = chan_name;
+		cl = &dsp_chan->cl;
+		cl->dev = dev;
+		cl->tx_block = false;
+		cl->knows_txdone = true;
+		cl->rx_callback = imx_dsp_handle_rx;
+
+		dsp_chan->ipc = dsp_ipc;
+		dsp_chan->idx = i % 2;
+		dsp_chan->ch = mbox_request_channel_byname(cl, chan_name);
+		if (IS_ERR(dsp_chan->ch)) {
+			ret = PTR_ERR(dsp_chan->ch);
+			if (ret != -EPROBE_DEFER)
+				dev_err(dev, "Failed to request mbox chan %s ret %d\n",
+					chan_name, ret);
+			kfree(dsp_chan->name);
+			goto out;
+		}
+
+		dev_dbg(dev, "request mbox chan %s\n", chan_name);
+	}
+
+	return 0;
+out:
+	for (j = 0; j < i; j++) {
+		dsp_chan = &dsp_ipc->chans[j];
+		mbox_free_channel(dsp_chan->ch);
+		kfree(dsp_chan->name);
+	}
+
+	return ret;
+}
+
+static int imx_dsp_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct imx_dsp_ipc *dsp_ipc;
+	int ret;
+
+	device_set_of_node_from_dev(&pdev->dev, pdev->dev.parent);
+
+	dsp_ipc = devm_kzalloc(dev, sizeof(*dsp_ipc), GFP_KERNEL);
+	if (!dsp_ipc)
+		return -ENOMEM;
+
+	dsp_ipc->dev = dev;
+	dev_set_drvdata(dev, dsp_ipc);
+
+	ret = imx_dsp_setup_channels(dsp_ipc);
+	if (ret < 0)
+		return ret;
+
+	dev_info(dev, "NXP i.MX DSP IPC initialized\n");
+
+	return 0;
+}
+
+static void imx_dsp_remove(struct platform_device *pdev)
+{
+	struct imx_dsp_chan *dsp_chan;
+	struct imx_dsp_ipc *dsp_ipc;
+	int i;
+
+	dsp_ipc = dev_get_drvdata(&pdev->dev);
+
+	for (i = 0; i < DSP_MU_CHAN_NUM; i++) {
+		dsp_chan = &dsp_ipc->chans[i];
+		mbox_free_channel(dsp_chan->ch);
+		kfree(dsp_chan->name);
+	}
+}
+
+static struct platform_driver imx_dsp_driver = {
+	.driver = {
+		.name = "imx-dsp",
+	},
+	.probe = imx_dsp_probe,
+	.remove = imx_dsp_remove,
+};
+builtin_platform_driver(imx_dsp_driver);
+
+MODULE_AUTHOR("Daniel Baluta <daniel.baluta@nxp.com>");
+MODULE_DESCRIPTION("IMX DSP IPC protocol driver");
+MODULE_LICENSE("GPL v2");