@@ -276,6 +276,25 @@ 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
=============
@@ -291,7 +310,8 @@ Any particular buffer can be fed from multiple sources. Sources include:
* WATCH_TYPE_BLOCK_NOTIFY
Notifications of this type indicate block layer events, such as I/O errors
- or temporary link loss. Watches of this type are set on a global queue.
+ or temporary link loss. Watches of this type are set on the global device
+ watch list.
Event Filtering
@@ -475,3 +475,4 @@
543 common fspick sys_fspick
544 common pidfd_open sys_pidfd_open
# 545 reserved for clone3
+546 common watch_devices sys_watch_devices
@@ -449,3 +449,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
435 common clone3 sys_clone3
+436 common watch_devices sys_watch_devices
@@ -356,3 +356,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
# 435 reserved for clone3
+436 common watch_devices sys_watch_devices
@@ -435,3 +435,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
# 435 reserved for clone3
+436 common watch_devices sys_watch_devices
@@ -441,3 +441,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
435 common clone3 sys_clone3
+436 common watch_devices sys_watch_devices
@@ -374,3 +374,4 @@
433 n32 fspick sys_fspick
434 n32 pidfd_open sys_pidfd_open
# 435 reserved for clone3
+436 n32 watch_devices sys_watch_devices
@@ -350,3 +350,4 @@
433 n64 fspick sys_fspick
434 n64 pidfd_open sys_pidfd_open
# 435 reserved for clone3
+436 n64 watch_devices sys_watch_devices
@@ -423,3 +423,4 @@
433 o32 fspick sys_fspick
434 o32 pidfd_open sys_pidfd_open
# 435 reserved for clone3
+436 o32 watch_devices sys_watch_devices
@@ -432,3 +432,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
435 common clone3 sys_clone3_wrapper
+436 common watch_devices sys_watch_devices
@@ -517,3 +517,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
435 nospu clone3 ppc_clone3
+436 common watch_devices sys_watch_devices
@@ -438,3 +438,4 @@
433 common fspick sys_fspick sys_fspick
434 common pidfd_open sys_pidfd_open sys_pidfd_open
435 common clone3 sys_clone3 sys_clone3
+436 common watch_devices sys_watch_devices sys_watch_devices
@@ -438,3 +438,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
# 435 reserved for clone3
+436 common watch_devices sys_watch_devices
@@ -481,3 +481,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
# 435 reserved for clone3
+436 common watch_devices sys_watch_devices
@@ -440,3 +440,4 @@
433 i386 fspick sys_fspick __ia32_sys_fspick
434 i386 pidfd_open sys_pidfd_open __ia32_sys_pidfd_open
435 i386 clone3 sys_clone3 __ia32_sys_clone3
+436 i386 watch_devices sys_watch_devices __ia32_sys_watch_devices
@@ -357,6 +357,7 @@
433 common fspick __x64_sys_fspick
434 common pidfd_open __x64_sys_pidfd_open
435 common clone3 __x64_sys_clone3/ptregs
+436 common watch_devices __x64_sys_watch_devices
#
# x32-specific system call numbers start at 512 to avoid cache impact
@@ -406,3 +406,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
435 common clone3 sys_clone3
+436 common watch_devices sys_watch_devices
@@ -1,6 +1,15 @@
# SPDX-License-Identifier: GPL-2.0
menu "Generic Driver Options"
+config DEVICE_NOTIFICATIONS
+ bool "Provide device event notifications"
+ depends on 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 +1,90 @@
+// 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/device.h>
+#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);
+}
+EXPORT_SYMBOL(post_device_notification);
+
+/**
+ * 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)
+ * @flags: Flags (reserved for future)
+ */
+SYSCALL_DEFINE3(watch_devices, int, watch_fd, int, watch_id, unsigned int, flags)
+{
+ struct watch_queue *wqueue;
+ struct watch *watch = NULL;
+ long ret = -ENOMEM;
+
+ if (watch_id < -1 || watch_id > 0xff || flags)
+ 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->info_id = (u32)watch_id << WATCH_INFO_ID__SHIFT;
+
+ ret = security_watch_devices();
+ if (ret < 0)
+ goto err_watch;
+
+ spin_lock(&device_watchers_lock);
+ ret = add_watch_to_object(watch, &device_watchers);
+ spin_unlock(&device_watchers_lock);
+ if (ret == 0)
+ watch = NULL;
+ } else {
+ spin_lock(&device_watchers_lock);
+ ret = remove_watch_from_object(&device_watchers, wqueue, 0,
+ false);
+ spin_unlock(&device_watchers_lock);
+ }
+
+err_watch:
+ kfree(watch);
+err_wqueue:
+ put_watch_queue(wqueue);
+err:
+ return ret;
+}
@@ -43,6 +43,7 @@ struct iommu_group;
struct iommu_fwspec;
struct dev_pin_info;
struct iommu_param;
+struct watch_notification;
struct bus_attribute {
struct attribute attr;
@@ -1412,6 +1413,12 @@ 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
@@ -1000,6 +1000,7 @@ asmlinkage long sys_fspick(int dfd, const char __user *path, unsigned int flags)
asmlinkage long sys_pidfd_send_signal(int pidfd, int sig,
siginfo_t __user *info,
unsigned int flags);
+asmlinkage long sys_watch_devices(int watch_fd, int watch_id, unsigned int flags);
/*
* Architecture-specific system calls
@@ -850,9 +850,11 @@ __SYSCALL(__NR_pidfd_open, sys_pidfd_open)
#define __NR_clone3 435
__SYSCALL(__NR_clone3, sys_clone3)
#endif
+#define __NR_watch_devices 436
+__SYSCALL(__NR_watch_devices, sys_watch_devices)
#undef __NR_syscalls
-#define __NR_syscalls 436
+#define __NR_syscalls 437
/*
* 32 bit systems traditionally used different
@@ -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(watch_devices);
/* 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, 0); Unless the application wants to receive all events, it should employ appropriate filters. For example, to receive just USB notifications, it could do: struct watch_notification_filter filter = { .nr_filters = 1, .filters = { [0] = { .type = WATCH_TYPE_USB_NOTIFY, .subtype_filter[0] = UINT_MAX; }, }, }; ioctl(fd, IOC_WATCH_QUEUE_SET_FILTER, &filter); Signed-off-by: David Howells <dhowells@redhat.com> --- Documentation/watch_queue.rst | 22 ++++++- arch/alpha/kernel/syscalls/syscall.tbl | 1 arch/arm/tools/syscall.tbl | 1 arch/ia64/kernel/syscalls/syscall.tbl | 1 arch/m68k/kernel/syscalls/syscall.tbl | 1 arch/microblaze/kernel/syscalls/syscall.tbl | 1 arch/mips/kernel/syscalls/syscall_n32.tbl | 1 arch/mips/kernel/syscalls/syscall_n64.tbl | 1 arch/mips/kernel/syscalls/syscall_o32.tbl | 1 arch/parisc/kernel/syscalls/syscall.tbl | 1 arch/powerpc/kernel/syscalls/syscall.tbl | 1 arch/s390/kernel/syscalls/syscall.tbl | 1 arch/sh/kernel/syscalls/syscall.tbl | 1 arch/sparc/kernel/syscalls/syscall.tbl | 1 arch/x86/entry/syscalls/syscall_32.tbl | 1 arch/x86/entry/syscalls/syscall_64.tbl | 1 arch/xtensa/kernel/syscalls/syscall.tbl | 1 drivers/base/Kconfig | 9 +++ drivers/base/Makefile | 1 drivers/base/watch.c | 90 +++++++++++++++++++++++++++ include/linux/device.h | 7 ++ include/linux/syscalls.h | 1 include/uapi/asm-generic/unistd.h | 4 + kernel/sys_ni.c | 1 24 files changed, 149 insertions(+), 2 deletions(-) create mode 100644 drivers/base/watch.c