@@ -11,7 +11,7 @@ receive notifications from the kernel. This can be used in conjunction with::
* Superblock event notifications
- * Block layer event notifications
+ * General device event notifications
The notifications buffers can be enabled by:
@@ -292,6 +292,25 @@ The ``id`` is the ID of the source object (such as the serial number on a key).
Only watches that have the same ID set in them will see this notification.
+Global Device Watch List
+========================
+
+There is a global watch list that hardware generated events, such as device
+connection, disconnection, failure and error can be posted upon. It must be
+enabled using::
+
+ CONFIG_DEVICE_NOTIFICATIONS
+
+Watchpoints are set in userspace using the device_notify(2) system call.
+Within the kernel events are posted upon it using::
+
+ void post_device_notification(struct watch_notification *n, u64 id);
+
+where ``n`` is the formatted notification record to post. ``id`` is an
+identifier that can be used to direct to specific watches, but it should be 0
+for general use on this queue.
+
+
Watch Sources
=============
@@ -317,12 +336,6 @@ Any particular buffer can be fed from multiple sources. Sources include:
See Documentation/security/keys/core.rst for more information.
- * WATCH_TYPE_BLOCK_NOTIFY
-
- Notifications of this type indicate block layer events, such as I/O errors
- or temporary link loss. Watchpoints of this type are set on a global
- queue.
-
Event Filtering
===============
@@ -441,3 +441,4 @@
434 i386 fsinfo sys_fsinfo __ia32_sys_fsinfo
435 i386 watch_mount sys_watch_mount __ia32_sys_watch_mount
436 i386 watch_sb sys_watch_sb __ia32_sys_watch_sb
+437 i386 watch_devices sys_watch_devices __ia32_sys_watch_devices
@@ -358,6 +358,7 @@
434 common fsinfo __x64_sys_fsinfo
435 common watch_mount __x64_sys_watch_mount
436 common watch_sb __x64_sys_watch_sb
+437 common watch_devices __x64_sys_watch_devices
#
# x32-specific system call numbers start at 512 to avoid cache impact
@@ -1,6 +1,15 @@
# SPDX-License-Identifier: GPL-2.0
menu "Generic Driver Options"
+config DEVICE_NOTIFICATIONS
+ bool "Provide device event notifications"
+ select WATCH_QUEUE
+ help
+ This option provides support for getting hardware event notifications
+ on devices, buses and interfaces. This makes use of the
+ /dev/watch_queue misc device to handle the notification buffer.
+ device_notify(2) is used to set/remove watches.
+
config UEVENT_HELPER
bool "Support for uevent helper"
help
@@ -7,6 +7,7 @@ obj-y := component.o core.o bus.o dd.o syscore.o \
attribute_container.o transport_class.o \
topology.o container.o property.o cacheinfo.o \
devcon.o swnode.o
+obj-$(CONFIG_DEVICE_NOTIFICATIONS) += watch.o
obj-$(CONFIG_DEVTMPFS) += devtmpfs.o
obj-y += power/
obj-$(CONFIG_ISA_BUS_API) += isa.o
new file mode 100644
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Event notifications.
+ *
+ * Copyright (C) 2019 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/watch_queue.h>
+#include <linux/syscalls.h>
+#include <linux/init_task.h>
+#include <linux/security.h>
+
+/*
+ * Global queue for watching for device layer events.
+ */
+static struct watch_list device_watchers = {
+ .watchers = HLIST_HEAD_INIT,
+ .lock = __SPIN_LOCK_UNLOCKED(&device_watchers.lock),
+};
+
+static DEFINE_SPINLOCK(device_watchers_lock);
+
+/**
+ * post_device_notification - Post notification of a device event
+ * @n - The notification to post
+ * @id - The device ID
+ *
+ * Note that there's only a global queue to which all events are posted. Might
+ * want to provide per-dev queues also.
+ */
+void post_device_notification(struct watch_notification *n, u64 id)
+{
+ post_watch_notification(&device_watchers, n, &init_cred, id);
+}
+
+/**
+ * sys_watch_devices - Watch for device events.
+ * @watch_fd: The watch queue to send notifications to.
+ * @watch_id: The watch ID to be placed in the notification (-1 to remove watch)
+ */
+SYSCALL_DEFINE2(watch_devices, int, watch_fd, int, watch_id)
+{
+ struct watch_queue *wqueue;
+ struct watch_list *wlist = &device_watchers;
+ struct watch *watch;
+ long ret = -ENOMEM;
+ u64 id = 0; /* Might want to allow dev# here. */
+
+ if (watch_id < -1 || watch_id > 0xff)
+ return -EINVAL;
+
+ wqueue = get_watch_queue(watch_fd);
+ if (IS_ERR(wqueue)) {
+ ret = PTR_ERR(wqueue);
+ goto err;
+ }
+
+ if (watch_id >= 0) {
+ watch = kzalloc(sizeof(*watch), GFP_KERNEL);
+ if (!watch)
+ goto err_wqueue;
+
+ init_watch(watch, wqueue);
+ watch->id = id;
+ watch->info_id = (u32)watch_id << WATCH_INFO_ID__SHIFT;
+
+ ret = security_watch_devices(watch);
+ if (ret < 0)
+ goto err_watch;
+
+ spin_lock(&device_watchers_lock);
+ ret = add_watch_to_object(watch, wlist);
+ spin_unlock(&device_watchers_lock);
+ if (ret == 0)
+ watch = NULL;
+ } else {
+ spin_lock(&device_watchers_lock);
+ ret = remove_watch_from_object(wlist, wqueue, id, false);
+ spin_unlock(&device_watchers_lock);
+ }
+
+err_watch:
+ kfree(watch);
+err_wqueue:
+ put_watch_queue(wqueue);
+err:
+ return ret;
+}
@@ -26,6 +26,7 @@
#include <linux/uidgid.h>
#include <linux/gfp.h>
#include <linux/overflow.h>
+#include <linux/watch_queue.h>
#include <asm/device.h>
struct device;
@@ -1396,6 +1397,12 @@ struct device_link *device_link_add(struct device *consumer,
void device_link_del(struct device_link *link);
void device_link_remove(void *consumer, struct device *supplier);
+#ifdef CONFIG_DEVICE_NOTIFICATIONS
+extern void post_device_notification(struct watch_notification *n, u64 id);
+#else
+static inline void post_device_notification(struct watch_notification *n, u64 id) {}
+#endif
+
#ifndef dev_fmt
#define dev_fmt(fmt) fmt
#endif
@@ -1005,6 +1005,7 @@ asmlinkage long sys_watch_mount(int dfd, const char __user *path,
unsigned int at_flags, int watch_fd, int watch_id);
asmlinkage long sys_watch_sb(int dfd, const char __user *path,
unsigned int at_flags, int watch_fd, int watch_id);
+asmlinkage long sys_watch_devices(int watch_fd, int watch_id, unsigned int flags);
/*
* Architecture-specific system calls
@@ -12,10 +12,12 @@
#include <uapi/linux/watch_queue.h>
#include <linux/kref.h>
+#include <linux/rcupdate.h>
#ifdef CONFIG_WATCH_QUEUE
struct watch_queue;
+struct cred;
/*
* Representation of a watch on an object.
@@ -53,6 +55,7 @@ extern void put_watch_queue(struct watch_queue *);
extern void init_watch(struct watch *, struct watch_queue *);
extern int add_watch_to_object(struct watch *, struct watch_list *);
extern int remove_watch_from_object(struct watch_list *, struct watch_queue *, u64, bool);
+extern void post_device_notification(struct watch_notification *, u64);
static inline void init_watch_list(struct watch_list *wlist,
void (*release_watch)(struct watch *))
@@ -51,6 +51,7 @@ COND_SYSCALL_COMPAT(io_pgetevents);
COND_SYSCALL(io_uring_setup);
COND_SYSCALL(io_uring_enter);
COND_SYSCALL(io_uring_register);
+COND_SYSCALL(device_notify);
/* fs/xattr.c */
Create a general, global watch list that can be used for the posting of device notification events, for such things as device attachment, detachment and errors on sources such as block devices and USB devices. This can be enabled with: CONFIG_DEVICE_NOTIFICATIONS To add a watch on this list, an event queue must be created and configured: fd = open("/dev/event_queue", O_RDWR); ioctl(fd, IOC_WATCH_QUEUE_SET_SIZE, page_size << n); and then a watch can be placed upon it using a system call: watch_devices(fd, 12); Unless the application wants to receive all events, it should employ appropriate filters. Signed-off-by: David Howells <dhowells@redhat.com> --- Documentation/watch_queue.rst | 27 +++++++--- arch/x86/entry/syscalls/syscall_32.tbl | 1 arch/x86/entry/syscalls/syscall_64.tbl | 1 drivers/base/Kconfig | 9 +++ drivers/base/Makefile | 1 drivers/base/watch.c | 89 ++++++++++++++++++++++++++++++++ include/linux/device.h | 7 +++ include/linux/syscalls.h | 1 include/linux/watch_queue.h | 3 + kernel/sys_ni.c | 1 10 files changed, 133 insertions(+), 7 deletions(-) create mode 100644 drivers/base/watch.c