Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 827 insertions, 0 deletions

diff --git a/drivers/remoteproc/qcom_sysmon.c b/drivers/remoteproc/qcom_sysmon.c
new file mode 100644
index 000000000..61e103832
--- /dev/null
+++ b/drivers/remoteproc/qcom_sysmon.c
@@ -0,0 +1,827 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2017, Linaro Ltd.
+ */
+#include <linux/firmware.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/remoteproc/qcom_rproc.h>
+#include <linux/rpmsg.h>
+
+#include "qcom_common.h"
+
+static BLOCKING_NOTIFIER_HEAD(sysmon_notifiers);
+
+struct qcom_sysmon {
+	struct rproc_subdev subdev;
+	struct rproc *rproc;
+
+	int state;
+	struct mutex state_lock;
+
+	struct list_head node;
+
+	const char *name;
+
+	int shutdown_irq;
+	int ssctl_version;
+	int ssctl_instance;
+
+	struct notifier_block nb;
+
+	struct device *dev;
+
+	struct rpmsg_endpoint *ept;
+	struct completion comp;
+	struct completion ind_comp;
+	struct completion shutdown_comp;
+	struct completion ssctl_comp;
+	struct mutex lock;
+
+	bool ssr_ack;
+	bool shutdown_acked;
+
+	struct qmi_handle qmi;
+	struct sockaddr_qrtr ssctl;
+};
+
+enum {
+	SSCTL_SSR_EVENT_BEFORE_POWERUP,
+	SSCTL_SSR_EVENT_AFTER_POWERUP,
+	SSCTL_SSR_EVENT_BEFORE_SHUTDOWN,
+	SSCTL_SSR_EVENT_AFTER_SHUTDOWN,
+};
+
+static const char * const sysmon_state_string[] = {
+	[SSCTL_SSR_EVENT_BEFORE_POWERUP]	= "before_powerup",
+	[SSCTL_SSR_EVENT_AFTER_POWERUP]		= "after_powerup",
+	[SSCTL_SSR_EVENT_BEFORE_SHUTDOWN]	= "before_shutdown",
+	[SSCTL_SSR_EVENT_AFTER_SHUTDOWN]	= "after_shutdown",
+};
+
+struct sysmon_event {
+	const char *subsys_name;
+	u32 ssr_event;
+};
+
+static DEFINE_MUTEX(sysmon_lock);
+static LIST_HEAD(sysmon_list);
+
+/**
+ * sysmon_send_event() - send notification of other remote's SSR event
+ * @sysmon:	sysmon context
+ * @event:	sysmon event context
+ */
+static void sysmon_send_event(struct qcom_sysmon *sysmon,
+			      const struct sysmon_event *event)
+{
+	char req[50];
+	int len;
+	int ret;
+
+	len = snprintf(req, sizeof(req), "ssr:%s:%s", event->subsys_name,
+		       sysmon_state_string[event->ssr_event]);
+	if (len >= sizeof(req))
+		return;
+
+	mutex_lock(&sysmon->lock);
+	reinit_completion(&sysmon->comp);
+	sysmon->ssr_ack = false;
+
+	ret = rpmsg_send(sysmon->ept, req, len);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "failed to send sysmon event\n");
+		goto out_unlock;
+	}
+
+	ret = wait_for_completion_timeout(&sysmon->comp,
+					  msecs_to_jiffies(5000));
+	if (!ret) {
+		dev_err(sysmon->dev, "timeout waiting for sysmon ack\n");
+		goto out_unlock;
+	}
+
+	if (!sysmon->ssr_ack)
+		dev_err(sysmon->dev, "unexpected response to sysmon event\n");
+
+out_unlock:
+	mutex_unlock(&sysmon->lock);
+}
+
+/**
+ * sysmon_request_shutdown() - request graceful shutdown of remote
+ * @sysmon:	sysmon context
+ *
+ * Return: boolean indicator of the remote processor acking the request
+ */
+static bool sysmon_request_shutdown(struct qcom_sysmon *sysmon)
+{
+	char *req = "ssr:shutdown";
+	bool acked = false;
+	int ret;
+
+	mutex_lock(&sysmon->lock);
+	reinit_completion(&sysmon->comp);
+	sysmon->ssr_ack = false;
+
+	ret = rpmsg_send(sysmon->ept, req, strlen(req) + 1);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "send sysmon shutdown request failed\n");
+		goto out_unlock;
+	}
+
+	ret = wait_for_completion_timeout(&sysmon->comp,
+					  msecs_to_jiffies(5000));
+	if (!ret) {
+		dev_err(sysmon->dev, "timeout waiting for sysmon ack\n");
+		goto out_unlock;
+	}
+
+	if (!sysmon->ssr_ack)
+		dev_err(sysmon->dev,
+			"unexpected response to sysmon shutdown request\n");
+	else
+		acked = true;
+
+out_unlock:
+	mutex_unlock(&sysmon->lock);
+
+	return acked;
+}
+
+static int sysmon_callback(struct rpmsg_device *rpdev, void *data, int count,
+			   void *priv, u32 addr)
+{
+	struct qcom_sysmon *sysmon = priv;
+	const char *ssr_ack = "ssr:ack";
+	const int ssr_ack_len = strlen(ssr_ack) + 1;
+
+	if (!sysmon)
+		return -EINVAL;
+
+	if (count >= ssr_ack_len && !memcmp(data, ssr_ack, ssr_ack_len))
+		sysmon->ssr_ack = true;
+
+	complete(&sysmon->comp);
+
+	return 0;
+}
+
+#define SSCTL_SHUTDOWN_REQ		0x21
+#define SSCTL_SHUTDOWN_READY_IND	0x21
+#define SSCTL_SUBSYS_EVENT_REQ		0x23
+
+#define SSCTL_MAX_MSG_LEN		7
+
+#define SSCTL_SUBSYS_NAME_LENGTH	15
+
+enum {
+	SSCTL_SSR_EVENT_FORCED,
+	SSCTL_SSR_EVENT_GRACEFUL,
+};
+
+struct ssctl_shutdown_resp {
+	struct qmi_response_type_v01 resp;
+};
+
+static const struct qmi_elem_info ssctl_shutdown_resp_ei[] = {
+	{
+		.data_type	= QMI_STRUCT,
+		.elem_len	= 1,
+		.elem_size	= sizeof(struct qmi_response_type_v01),
+		.array_type	= NO_ARRAY,
+		.tlv_type	= 0x02,
+		.offset		= offsetof(struct ssctl_shutdown_resp, resp),
+		.ei_array	= qmi_response_type_v01_ei,
+	},
+	{}
+};
+
+struct ssctl_subsys_event_req {
+	u32 subsys_name_len;
+	char subsys_name[SSCTL_SUBSYS_NAME_LENGTH];
+	u32 event;
+	u8 evt_driven_valid;
+	u32 evt_driven;
+};
+
+static const struct qmi_elem_info ssctl_subsys_event_req_ei[] = {
+	{
+		.data_type	= QMI_DATA_LEN,
+		.elem_len	= 1,
+		.elem_size	= sizeof(uint8_t),
+		.array_type	= NO_ARRAY,
+		.tlv_type	= 0x01,
+		.offset		= offsetof(struct ssctl_subsys_event_req,
+					   subsys_name_len),
+		.ei_array	= NULL,
+	},
+	{
+		.data_type	= QMI_UNSIGNED_1_BYTE,
+		.elem_len	= SSCTL_SUBSYS_NAME_LENGTH,
+		.elem_size	= sizeof(char),
+		.array_type	= VAR_LEN_ARRAY,
+		.tlv_type	= 0x01,
+		.offset		= offsetof(struct ssctl_subsys_event_req,
+					   subsys_name),
+		.ei_array	= NULL,
+	},
+	{
+		.data_type	= QMI_SIGNED_4_BYTE_ENUM,
+		.elem_len	= 1,
+		.elem_size	= sizeof(uint32_t),
+		.array_type	= NO_ARRAY,
+		.tlv_type	= 0x02,
+		.offset		= offsetof(struct ssctl_subsys_event_req,
+					   event),
+		.ei_array	= NULL,
+	},
+	{
+		.data_type	= QMI_OPT_FLAG,
+		.elem_len	= 1,
+		.elem_size	= sizeof(uint8_t),
+		.array_type	= NO_ARRAY,
+		.tlv_type	= 0x10,
+		.offset		= offsetof(struct ssctl_subsys_event_req,
+					   evt_driven_valid),
+		.ei_array	= NULL,
+	},
+	{
+		.data_type	= QMI_SIGNED_4_BYTE_ENUM,
+		.elem_len	= 1,
+		.elem_size	= sizeof(uint32_t),
+		.array_type	= NO_ARRAY,
+		.tlv_type	= 0x10,
+		.offset		= offsetof(struct ssctl_subsys_event_req,
+					   evt_driven),
+		.ei_array	= NULL,
+	},
+	{}
+};
+
+struct ssctl_subsys_event_resp {
+	struct qmi_response_type_v01 resp;
+};
+
+static const struct qmi_elem_info ssctl_subsys_event_resp_ei[] = {
+	{
+		.data_type	= QMI_STRUCT,
+		.elem_len	= 1,
+		.elem_size	= sizeof(struct qmi_response_type_v01),
+		.array_type	= NO_ARRAY,
+		.tlv_type	= 0x02,
+		.offset		= offsetof(struct ssctl_subsys_event_resp,
+					   resp),
+		.ei_array	= qmi_response_type_v01_ei,
+	},
+	{}
+};
+
+static const struct qmi_elem_info ssctl_shutdown_ind_ei[] = {
+	{}
+};
+
+static void sysmon_ind_cb(struct qmi_handle *qmi, struct sockaddr_qrtr *sq,
+			  struct qmi_txn *txn, const void *data)
+{
+	struct qcom_sysmon *sysmon = container_of(qmi, struct qcom_sysmon, qmi);
+
+	complete(&sysmon->ind_comp);
+}
+
+static const struct qmi_msg_handler qmi_indication_handler[] = {
+	{
+		.type = QMI_INDICATION,
+		.msg_id = SSCTL_SHUTDOWN_READY_IND,
+		.ei = ssctl_shutdown_ind_ei,
+		.decoded_size = 0,
+		.fn = sysmon_ind_cb
+	},
+	{}
+};
+
+static bool ssctl_request_shutdown_wait(struct qcom_sysmon *sysmon)
+{
+	int ret;
+
+	ret = wait_for_completion_timeout(&sysmon->shutdown_comp, 10 * HZ);
+	if (ret)
+		return true;
+
+	ret = try_wait_for_completion(&sysmon->ind_comp);
+	if (ret)
+		return true;
+
+	dev_err(sysmon->dev, "timeout waiting for shutdown ack\n");
+	return false;
+}
+
+/**
+ * ssctl_request_shutdown() - request shutdown via SSCTL QMI service
+ * @sysmon:	sysmon context
+ *
+ * Return: boolean indicator of the remote processor acking the request
+ */
+static bool ssctl_request_shutdown(struct qcom_sysmon *sysmon)
+{
+	struct ssctl_shutdown_resp resp;
+	struct qmi_txn txn;
+	bool acked = false;
+	int ret;
+
+	reinit_completion(&sysmon->ind_comp);
+	reinit_completion(&sysmon->shutdown_comp);
+	ret = qmi_txn_init(&sysmon->qmi, &txn, ssctl_shutdown_resp_ei, &resp);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "failed to allocate QMI txn\n");
+		return false;
+	}
+
+	ret = qmi_send_request(&sysmon->qmi, &sysmon->ssctl, &txn,
+			       SSCTL_SHUTDOWN_REQ, 0, NULL, NULL);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "failed to send shutdown request\n");
+		qmi_txn_cancel(&txn);
+		return false;
+	}
+
+	ret = qmi_txn_wait(&txn, 5 * HZ);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "timeout waiting for shutdown response\n");
+	} else if (resp.resp.result) {
+		dev_err(sysmon->dev, "shutdown request rejected\n");
+	} else {
+		dev_dbg(sysmon->dev, "shutdown request completed\n");
+		acked = true;
+	}
+
+	if (sysmon->shutdown_irq > 0)
+		return ssctl_request_shutdown_wait(sysmon);
+
+	return acked;
+}
+
+/**
+ * ssctl_send_event() - send notification of other remote's SSR event
+ * @sysmon:	sysmon context
+ * @event:	sysmon event context
+ */
+static void ssctl_send_event(struct qcom_sysmon *sysmon,
+			     const struct sysmon_event *event)
+{
+	struct ssctl_subsys_event_resp resp;
+	struct ssctl_subsys_event_req req;
+	struct qmi_txn txn;
+	int ret;
+
+	memset(&resp, 0, sizeof(resp));
+	ret = qmi_txn_init(&sysmon->qmi, &txn, ssctl_subsys_event_resp_ei, &resp);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "failed to allocate QMI txn\n");
+		return;
+	}
+
+	memset(&req, 0, sizeof(req));
+	strscpy(req.subsys_name, event->subsys_name, sizeof(req.subsys_name));
+	req.subsys_name_len = strlen(req.subsys_name);
+	req.event = event->ssr_event;
+	req.evt_driven_valid = true;
+	req.evt_driven = SSCTL_SSR_EVENT_FORCED;
+
+	ret = qmi_send_request(&sysmon->qmi, &sysmon->ssctl, &txn,
+			       SSCTL_SUBSYS_EVENT_REQ, 40,
+			       ssctl_subsys_event_req_ei, &req);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "failed to send subsystem event\n");
+		qmi_txn_cancel(&txn);
+		return;
+	}
+
+	ret = qmi_txn_wait(&txn, 5 * HZ);
+	if (ret < 0)
+		dev_err(sysmon->dev, "timeout waiting for subsystem event response\n");
+	else if (resp.resp.result)
+		dev_err(sysmon->dev, "subsystem event rejected\n");
+	else
+		dev_dbg(sysmon->dev, "subsystem event accepted\n");
+}
+
+/**
+ * ssctl_new_server() - QMI callback indicating a new service
+ * @qmi:	QMI handle
+ * @svc:	service information
+ *
+ * Return: 0 if we're interested in this service, -EINVAL otherwise.
+ */
+static int ssctl_new_server(struct qmi_handle *qmi, struct qmi_service *svc)
+{
+	struct qcom_sysmon *sysmon = container_of(qmi, struct qcom_sysmon, qmi);
+
+	switch (svc->version) {
+	case 1:
+		if (svc->instance != 0)
+			return -EINVAL;
+		if (strcmp(sysmon->name, "modem"))
+			return -EINVAL;
+		break;
+	case 2:
+		if (svc->instance != sysmon->ssctl_instance)
+			return -EINVAL;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	sysmon->ssctl_version = svc->version;
+
+	sysmon->ssctl.sq_family = AF_QIPCRTR;
+	sysmon->ssctl.sq_node = svc->node;
+	sysmon->ssctl.sq_port = svc->port;
+
+	svc->priv = sysmon;
+
+	complete(&sysmon->ssctl_comp);
+
+	return 0;
+}
+
+/**
+ * ssctl_del_server() - QMI callback indicating that @svc is removed
+ * @qmi:	QMI handle
+ * @svc:	service information
+ */
+static void ssctl_del_server(struct qmi_handle *qmi, struct qmi_service *svc)
+{
+	struct qcom_sysmon *sysmon = svc->priv;
+
+	sysmon->ssctl_version = 0;
+}
+
+static const struct qmi_ops ssctl_ops = {
+	.new_server = ssctl_new_server,
+	.del_server = ssctl_del_server,
+};
+
+static int sysmon_prepare(struct rproc_subdev *subdev)
+{
+	struct qcom_sysmon *sysmon = container_of(subdev, struct qcom_sysmon,
+						  subdev);
+	struct sysmon_event event = {
+		.subsys_name = sysmon->name,
+		.ssr_event = SSCTL_SSR_EVENT_BEFORE_POWERUP
+	};
+
+	mutex_lock(&sysmon->state_lock);
+	sysmon->state = SSCTL_SSR_EVENT_BEFORE_POWERUP;
+	blocking_notifier_call_chain(&sysmon_notifiers, 0, (void *)&event);
+	mutex_unlock(&sysmon->state_lock);
+
+	return 0;
+}
+
+/**
+ * sysmon_start() - start callback for the sysmon remoteproc subdevice
+ * @subdev:	instance of the sysmon subdevice
+ *
+ * Inform all the listners of sysmon notifications that the rproc associated
+ * to @subdev has booted up. The rproc that booted up also needs to know
+ * which rprocs are already up and running, so send start notifications
+ * on behalf of all the online rprocs.
+ */
+static int sysmon_start(struct rproc_subdev *subdev)
+{
+	struct qcom_sysmon *sysmon = container_of(subdev, struct qcom_sysmon,
+						  subdev);
+	struct qcom_sysmon *target;
+	struct sysmon_event event = {
+		.subsys_name = sysmon->name,
+		.ssr_event = SSCTL_SSR_EVENT_AFTER_POWERUP
+	};
+
+	reinit_completion(&sysmon->ssctl_comp);
+	mutex_lock(&sysmon->state_lock);
+	sysmon->state = SSCTL_SSR_EVENT_AFTER_POWERUP;
+	blocking_notifier_call_chain(&sysmon_notifiers, 0, (void *)&event);
+	mutex_unlock(&sysmon->state_lock);
+
+	mutex_lock(&sysmon_lock);
+	list_for_each_entry(target, &sysmon_list, node) {
+		mutex_lock(&target->state_lock);
+		if (target == sysmon || target->state != SSCTL_SSR_EVENT_AFTER_POWERUP) {
+			mutex_unlock(&target->state_lock);
+			continue;
+		}
+
+		event.subsys_name = target->name;
+		event.ssr_event = target->state;
+
+		if (sysmon->ssctl_version == 2)
+			ssctl_send_event(sysmon, &event);
+		else if (sysmon->ept)
+			sysmon_send_event(sysmon, &event);
+		mutex_unlock(&target->state_lock);
+	}
+	mutex_unlock(&sysmon_lock);
+
+	return 0;
+}
+
+static void sysmon_stop(struct rproc_subdev *subdev, bool crashed)
+{
+	struct qcom_sysmon *sysmon = container_of(subdev, struct qcom_sysmon, subdev);
+	struct sysmon_event event = {
+		.subsys_name = sysmon->name,
+		.ssr_event = SSCTL_SSR_EVENT_BEFORE_SHUTDOWN
+	};
+
+	sysmon->shutdown_acked = false;
+
+	mutex_lock(&sysmon->state_lock);
+	sysmon->state = SSCTL_SSR_EVENT_BEFORE_SHUTDOWN;
+	blocking_notifier_call_chain(&sysmon_notifiers, 0, (void *)&event);
+	mutex_unlock(&sysmon->state_lock);
+
+	/* Don't request graceful shutdown if we've crashed */
+	if (crashed)
+		return;
+
+	if (sysmon->ssctl_instance) {
+		if (!wait_for_completion_timeout(&sysmon->ssctl_comp, HZ / 2))
+			dev_err(sysmon->dev, "timeout waiting for ssctl service\n");
+	}
+
+	if (sysmon->ssctl_version)
+		sysmon->shutdown_acked = ssctl_request_shutdown(sysmon);
+	else if (sysmon->ept)
+		sysmon->shutdown_acked = sysmon_request_shutdown(sysmon);
+}
+
+static void sysmon_unprepare(struct rproc_subdev *subdev)
+{
+	struct qcom_sysmon *sysmon = container_of(subdev, struct qcom_sysmon,
+						  subdev);
+	struct sysmon_event event = {
+		.subsys_name = sysmon->name,
+		.ssr_event = SSCTL_SSR_EVENT_AFTER_SHUTDOWN
+	};
+
+	mutex_lock(&sysmon->state_lock);
+	sysmon->state = SSCTL_SSR_EVENT_AFTER_SHUTDOWN;
+	blocking_notifier_call_chain(&sysmon_notifiers, 0, (void *)&event);
+	mutex_unlock(&sysmon->state_lock);
+}
+
+/**
+ * sysmon_notify() - notify sysmon target of another's SSR
+ * @nb:		notifier_block associated with sysmon instance
+ * @event:	unused
+ * @data:	SSR identifier of the remote that is going down
+ */
+static int sysmon_notify(struct notifier_block *nb, unsigned long event,
+			 void *data)
+{
+	struct qcom_sysmon *sysmon = container_of(nb, struct qcom_sysmon, nb);
+	struct sysmon_event *sysmon_event = data;
+
+	/* Skip non-running rprocs and the originating instance */
+	if (sysmon->state != SSCTL_SSR_EVENT_AFTER_POWERUP ||
+	    !strcmp(sysmon_event->subsys_name, sysmon->name)) {
+		dev_dbg(sysmon->dev, "not notifying %s\n", sysmon->name);
+		return NOTIFY_DONE;
+	}
+
+	/* Only SSCTL version 2 supports SSR events */
+	if (sysmon->ssctl_version == 2)
+		ssctl_send_event(sysmon, sysmon_event);
+	else if (sysmon->ept)
+		sysmon_send_event(sysmon, sysmon_event);
+
+	return NOTIFY_DONE;
+}
+
+static irqreturn_t sysmon_shutdown_interrupt(int irq, void *data)
+{
+	struct qcom_sysmon *sysmon = data;
+
+	complete(&sysmon->shutdown_comp);
+
+	return IRQ_HANDLED;
+}
+
+/**
+ * qcom_add_sysmon_subdev() - create a sysmon subdev for the given remoteproc
+ * @rproc:	rproc context to associate the subdev with
+ * @name:	name of this subdev, to use in SSR
+ * @ssctl_instance: instance id of the ssctl QMI service
+ *
+ * Return: A new qcom_sysmon object, or an error pointer on failure
+ */
+struct qcom_sysmon *qcom_add_sysmon_subdev(struct rproc *rproc,
+					   const char *name,
+					   int ssctl_instance)
+{
+	struct qcom_sysmon *sysmon;
+	int ret;
+
+	sysmon = kzalloc_obj(*sysmon);
+	if (!sysmon)
+		return ERR_PTR(-ENOMEM);
+
+	sysmon->dev = rproc->dev.parent;
+	sysmon->rproc = rproc;
+
+	sysmon->name = name;
+	sysmon->ssctl_instance = ssctl_instance;
+
+	init_completion(&sysmon->comp);
+	init_completion(&sysmon->ind_comp);
+	init_completion(&sysmon->shutdown_comp);
+	init_completion(&sysmon->ssctl_comp);
+	mutex_init(&sysmon->lock);
+	mutex_init(&sysmon->state_lock);
+
+	sysmon->shutdown_irq = of_irq_get_byname(sysmon->dev->of_node,
+						 "shutdown-ack");
+	if (sysmon->shutdown_irq < 0) {
+		if (sysmon->shutdown_irq != -ENODATA) {
+			dev_err(sysmon->dev,
+				"failed to retrieve shutdown-ack IRQ\n");
+			ret = sysmon->shutdown_irq;
+			kfree(sysmon);
+			return ERR_PTR(ret);
+		}
+	} else {
+		ret = devm_request_threaded_irq(sysmon->dev,
+						sysmon->shutdown_irq,
+						NULL, sysmon_shutdown_interrupt,
+						IRQF_TRIGGER_RISING | IRQF_ONESHOT,
+						"q6v5 shutdown-ack", sysmon);
+		if (ret) {
+			kfree(sysmon);
+			return ERR_PTR(ret);
+		}
+	}
+
+	ret = qmi_handle_init(&sysmon->qmi, SSCTL_MAX_MSG_LEN, &ssctl_ops,
+			      qmi_indication_handler);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "failed to initialize qmi handle\n");
+		kfree(sysmon);
+		return ERR_PTR(ret);
+	}
+
+	qmi_add_lookup(&sysmon->qmi, QMI_SERVICE_ID_SSCTL, 0, 0);
+
+	sysmon->subdev.prepare = sysmon_prepare;
+	sysmon->subdev.start = sysmon_start;
+	sysmon->subdev.stop = sysmon_stop;
+	sysmon->subdev.unprepare = sysmon_unprepare;
+
+	rproc_add_subdev(rproc, &sysmon->subdev);
+
+	sysmon->nb.notifier_call = sysmon_notify;
+	blocking_notifier_chain_register(&sysmon_notifiers, &sysmon->nb);
+
+	mutex_lock(&sysmon_lock);
+	list_add(&sysmon->node, &sysmon_list);
+	mutex_unlock(&sysmon_lock);
+
+	return sysmon;
+}
+EXPORT_SYMBOL_GPL(qcom_add_sysmon_subdev);
+
+/**
+ * qcom_remove_sysmon_subdev() - release a qcom_sysmon
+ * @sysmon:	sysmon context, as retrieved by qcom_add_sysmon_subdev()
+ */
+void qcom_remove_sysmon_subdev(struct qcom_sysmon *sysmon)
+{
+	if (!sysmon)
+		return;
+
+	mutex_lock(&sysmon_lock);
+	list_del(&sysmon->node);
+	mutex_unlock(&sysmon_lock);
+
+	blocking_notifier_chain_unregister(&sysmon_notifiers, &sysmon->nb);
+
+	rproc_remove_subdev(sysmon->rproc, &sysmon->subdev);
+
+	qmi_handle_release(&sysmon->qmi);
+
+	kfree(sysmon);
+}
+EXPORT_SYMBOL_GPL(qcom_remove_sysmon_subdev);
+
+/**
+ * qcom_sysmon_shutdown_acked() - query the success of the last shutdown
+ * @sysmon:	sysmon context
+ *
+ * When sysmon is used to request a graceful shutdown of the remote processor
+ * this can be used by the remoteproc driver to query the success, in order to
+ * know if it should fall back to other means of requesting a shutdown.
+ *
+ * Return: boolean indicator of the success of the last shutdown request
+ */
+bool qcom_sysmon_shutdown_acked(struct qcom_sysmon *sysmon)
+{
+	return sysmon && sysmon->shutdown_acked;
+}
+EXPORT_SYMBOL_GPL(qcom_sysmon_shutdown_acked);
+
+bool qcom_sysmon_shutdown_irq_state(struct qcom_sysmon *sysmon)
+{
+	bool shutdown_state;
+	int ret;
+
+	if (!sysmon)
+		return false;
+
+	ret = irq_get_irqchip_state(sysmon->shutdown_irq,
+				    IRQCHIP_STATE_LINE_LEVEL, &shutdown_state);
+	if (ret) {
+		dev_warn(sysmon->dev, "failed to get shutdown_state: %d\n", ret);
+		return false;
+	}
+
+	return shutdown_state;
+}
+EXPORT_SYMBOL_GPL(qcom_sysmon_shutdown_irq_state);
+
+/**
+ * sysmon_probe() - probe sys_mon channel
+ * @rpdev:	rpmsg device handle
+ *
+ * Find the sysmon context associated with the ancestor remoteproc and assign
+ * this rpmsg device with said sysmon context.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+static int sysmon_probe(struct rpmsg_device *rpdev)
+{
+	struct qcom_sysmon *sysmon;
+	struct rproc *rproc;
+
+	rproc = rproc_get_by_child(&rpdev->dev);
+	if (!rproc) {
+		dev_err(&rpdev->dev, "sysmon device not child of rproc\n");
+		return -EINVAL;
+	}
+
+	mutex_lock(&sysmon_lock);
+	list_for_each_entry(sysmon, &sysmon_list, node) {
+		if (sysmon->rproc == rproc)
+			goto found;
+	}
+	mutex_unlock(&sysmon_lock);
+
+	dev_err(&rpdev->dev, "no sysmon associated with parent rproc\n");
+
+	return -EINVAL;
+
+found:
+	mutex_unlock(&sysmon_lock);
+
+	rpdev->ept->priv = sysmon;
+	sysmon->ept = rpdev->ept;
+
+	return 0;
+}
+
+/**
+ * sysmon_remove() - sys_mon channel remove handler
+ * @rpdev:	rpmsg device handle
+ *
+ * Disassociate the rpmsg device with the sysmon instance.
+ */
+static void sysmon_remove(struct rpmsg_device *rpdev)
+{
+	struct qcom_sysmon *sysmon = rpdev->ept->priv;
+
+	sysmon->ept = NULL;
+}
+
+static const struct rpmsg_device_id sysmon_match[] = {
+	{ "sys_mon" },
+	{}
+};
+
+static struct rpmsg_driver sysmon_driver = {
+	.probe = sysmon_probe,
+	.remove = sysmon_remove,
+	.callback = sysmon_callback,
+	.id_table = sysmon_match,
+	.drv = {
+		.name = "qcom_sysmon",
+	},
+};
+
+module_rpmsg_driver(sysmon_driver);
+
+MODULE_DESCRIPTION("Qualcomm sysmon driver");
+MODULE_LICENSE("GPL v2");