[S390] smsgiucv_app: deliver z/VM CP special messages (SMSG) as uevents

The smsgiucv_app driver registers a callback with the smsgiucv driver
to receive z/VM CP special messages (SMSG) starting with "APP".

When the callback is called for special messages, the driver creates
an uevent for the received message.  The uevent consists of additional
environment data containing the message prefix ("APP"), message sender,
and message content.

udev rules can be used to trigger application specific actions through
matching the content or sender of the special message.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/net/Kconfig

@@ -43,6 +43,16 @@ config SMSGIUCV
 	  Select this option if you want to be able to receive SMSG messages
 	  from other VM guest systems.
 
+config SMSGIUCV_EVENT
+	tristate "Deliver IUCV special messages as uevents (VM only)"
+	depends on SMSGIUCV
+	help
+	  Select this option to deliver CP special messages (SMSGs) as
+	  uevents.  The driver handles only those special messages that
+	  start with "APP".
+
+	  To compile as a module, choose M. The module name is "smsgiucv_app".
+
 config CLAW
 	tristate "CLAW device support"
 	depends on CCW && NETDEVICES

drivers/s390/net/Makefile

@@ -6,6 +6,7 @@ ctcm-y += ctcm_main.o ctcm_fsms.o ctcm_mpc.o ctcm_sysfs.o ctcm_dbug.o
 obj-$(CONFIG_CTCM) += ctcm.o fsm.o
 obj-$(CONFIG_NETIUCV) += netiucv.o fsm.o
 obj-$(CONFIG_SMSGIUCV) += smsgiucv.o
+obj-$(CONFIG_SMSGIUCV_EVENT) += smsgiucv_app.o
 obj-$(CONFIG_LCS) += lcs.o
 obj-$(CONFIG_CLAW) += claw.o
 qeth-y += qeth_core_sys.o qeth_core_main.o qeth_core_mpc.o

drivers/s390/net/smsgiucv.c

@@ -177,7 +177,7 @@ static const struct dev_pm_ops smsg_pm_ops = {
 
 static struct device_driver smsg_driver = {
 	.owner = THIS_MODULE,
-	.name = "SMSGIUCV",
+	.name = SMSGIUCV_DRV_NAME,
 	.bus  = &iucv_bus,
 	.pm = &smsg_pm_ops,
 };

drivers/s390/net/smsgiucv.h

@@ -5,6 +5,8 @@
  * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
  */
 
+#define SMSGIUCV_DRV_NAME     "SMSGIUCV"
+
 int  smsg_register_callback(const char *,
 			    void (*)(const char *, char *));
 void smsg_unregister_callback(const char *,

drivers/s390/net/smsgiucv_app.c

+/*
+ * Deliver z/VM CP special messages (SMSG) as uevents.
+ *
+ * The driver registers for z/VM CP special messages with the
+ * "APP" prefix. Incoming messages are delivered to user space
+ * as uevents.
+ *
+ * Copyright IBM Corp. 2010
+ * Author(s): Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
+ *
+ */
+#define KMSG_COMPONENT		"smsgiucv_app"
+#define pr_fmt(fmt)		KMSG_COMPONENT ": " fmt
+
+#include <linux/ctype.h>
+#include <linux/err.h>
+#include <linux/device.h>
+#include <linux/list.h>
+#include <linux/kobject.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/workqueue.h>
+#include <net/iucv/iucv.h>
+#include "smsgiucv.h"
+
+/* prefix used for SMSG registration */
+#define SMSG_PREFIX		"APP"
+
+/* SMSG related uevent environment variables */
+#define ENV_SENDER_STR		"SMSG_SENDER="
+#define ENV_SENDER_LEN		(strlen(ENV_SENDER_STR) + 8 + 1)
+#define ENV_PREFIX_STR		"SMSG_ID="
+#define ENV_PREFIX_LEN		(strlen(ENV_PREFIX_STR) + \
+				 strlen(SMSG_PREFIX) + 1)
+#define ENV_TEXT_STR		"SMSG_TEXT="
+#define ENV_TEXT_LEN(msg)	(strlen(ENV_TEXT_STR) + strlen((msg)) + 1)
+
+/* z/VM user ID which is permitted to send SMSGs
+ * If the value is undefined or empty (""), special messages are
+ * accepted from any z/VM user ID. */
+static char *sender;
+module_param(sender, charp, 0400);
+MODULE_PARM_DESC(sender, "z/VM user ID from which CP SMSGs are accepted");
+
+/* SMSG device representation */
+static struct device *smsg_app_dev;
+
+/* list element for queuing received messages for delivery */
+struct smsg_app_event {
+	struct list_head list;
+	char *buf;
+	char *envp[4];
+};
+
+/* queue for outgoing uevents */
+static LIST_HEAD(smsg_event_queue);
+static DEFINE_SPINLOCK(smsg_event_queue_lock);
+
+static void smsg_app_event_free(struct smsg_app_event *ev)
+{
+	kfree(ev->buf);
+	kfree(ev);
+}
+
+static struct smsg_app_event *smsg_app_event_alloc(const char *from,
+						   const char *msg)
+{
+	struct smsg_app_event *ev;
+
+	ev = kzalloc(sizeof(*ev), GFP_ATOMIC);
+	if (!ev)
+		return NULL;
+
+	ev->buf = kzalloc(ENV_SENDER_LEN + ENV_PREFIX_LEN +
+			  ENV_TEXT_LEN(msg), GFP_ATOMIC);
+	if (!ev->buf) {
+		kfree(ev);
+		return NULL;
+	}
+
+	/* setting up environment pointers into buf */
+	ev->envp[0] = ev->buf;
+	ev->envp[1] = ev->envp[0] + ENV_SENDER_LEN;
+	ev->envp[2] = ev->envp[1] + ENV_PREFIX_LEN;
+	ev->envp[3] = NULL;
+
+	/* setting up environment: sender, prefix name, and message text */
+	snprintf(ev->envp[0], ENV_SENDER_LEN, ENV_SENDER_STR "%s", from);
+	snprintf(ev->envp[1], ENV_PREFIX_LEN, ENV_PREFIX_STR "%s", SMSG_PREFIX);
+	snprintf(ev->envp[2], ENV_TEXT_LEN(msg), ENV_TEXT_STR "%s", msg);
+
+	return ev;
+}
+
+static void smsg_event_work_fn(struct work_struct *work)
+{
+	LIST_HEAD(event_queue);
+	struct smsg_app_event *p, *n;
+	struct device *dev;
+
+	dev = get_device(smsg_app_dev);
+	if (!dev)
+		return;
+
+	spin_lock_bh(&smsg_event_queue_lock);
+	list_splice_init(&smsg_event_queue, &event_queue);
+	spin_unlock_bh(&smsg_event_queue_lock);
+
+	list_for_each_entry_safe(p, n, &event_queue, list) {
+		list_del(&p->list);
+		kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, p->envp);
+		smsg_app_event_free(p);
+	}
+
+	put_device(dev);
+}
+static DECLARE_WORK(smsg_event_work, smsg_event_work_fn);
+
+static void smsg_app_callback(const char *from, char *msg)
+{
+	struct smsg_app_event *se;
+
+	/* check if the originating z/VM user ID matches
+	 * the configured sender. */
+	if (sender && strlen(sender) > 0 && strcmp(from, sender) != 0)
+		return;
+
+	/* get start of message text (skip prefix and leading blanks) */
+	msg += strlen(SMSG_PREFIX);
+	while (*msg && isspace(*msg))
+		msg++;
+	if (*msg == '\0')
+		return;
+
+	/* allocate event list element and its environment */
+	se = smsg_app_event_alloc(from, msg);
+	if (!se)
+		return;
+
+	/* queue event and schedule work function */
+	spin_lock(&smsg_event_queue_lock);
+	list_add_tail(&se->list, &smsg_event_queue);
+	spin_unlock(&smsg_event_queue_lock);
+
+	schedule_work(&smsg_event_work);
+	return;
+}
+
+static int __init smsgiucv_app_init(void)
+{
+	struct device_driver *smsgiucv_drv;
+	int rc;
+
+	if (!MACHINE_IS_VM)
+		return -ENODEV;
+
+	smsg_app_dev = kzalloc(sizeof(*smsg_app_dev), GFP_KERNEL);
+	if (!smsg_app_dev)
+		return -ENOMEM;
+
+	smsgiucv_drv = driver_find(SMSGIUCV_DRV_NAME, &iucv_bus);
+	if (!smsgiucv_drv) {
+		kfree(smsg_app_dev);
+		return -ENODEV;
+	}
+
+	rc = dev_set_name(smsg_app_dev, KMSG_COMPONENT);
+	if (rc) {
+		kfree(smsg_app_dev);
+		goto fail_put_driver;
+	}
+	smsg_app_dev->bus = &iucv_bus;
+	smsg_app_dev->parent = iucv_root;
+	smsg_app_dev->release = (void (*)(struct device *)) kfree;
+	smsg_app_dev->driver = smsgiucv_drv;
+	rc = device_register(smsg_app_dev);
+	if (rc) {
+		put_device(smsg_app_dev);
+		goto fail_put_driver;
+	}
+
+	/* register with the smsgiucv device driver */
+	rc = smsg_register_callback(SMSG_PREFIX, smsg_app_callback);
+	if (rc) {
+		device_unregister(smsg_app_dev);
+		goto fail_put_driver;
+	}
+
+	rc = 0;
+fail_put_driver:
+	put_driver(smsgiucv_drv);
+	return rc;
+}
+module_init(smsgiucv_app_init);
+
+static void __exit smsgiucv_app_exit(void)
+{
+	/* unregister callback */
+	smsg_unregister_callback(SMSG_PREFIX, smsg_app_callback);
+
+	/* cancel pending work and flush any queued event work */
+	cancel_work_sync(&smsg_event_work);
+	smsg_event_work_fn(&smsg_event_work);
+
+	device_unregister(smsg_app_dev);
+}
+module_exit(smsgiucv_app_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Deliver z/VM CP SMSG as uevents");
+MODULE_AUTHOR("Hendrik Brueckner <brueckner@linux.vnet.ibm.com>");