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uapi: General notification queue definitions

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Add UAPI definitions for the general notification queue, including the
following pieces:

 (*) struct watch_notification.

     This is the metadata header for notification messages.  It includes a
     type and subtype that indicate the source of the message
     (eg. WATCH_TYPE_MOUNT_NOTIFY) and the kind of the message
     (eg. NOTIFY_MOUNT_NEW_MOUNT).

     The header also contains an information field that conveys the
     following information:

	- WATCH_INFO_LENGTH.  The size of the entry (entries are variable
          length).

	- WATCH_INFO_ID.  The watch ID specified when the watchpoint was
          set.

	- WATCH_INFO_TYPE_INFO.  (Sub)type-specific information.

	- WATCH_INFO_FLAG_*.  Flag bits overlain on the type-specific
          information.  For use by the type.

     All the information in the header can be used in filtering messages at
     the point of writing into the buffer.

 (*) struct watch_notification_removal

     This is an extended watch-removal notification record that includes an
     'id' field that can indicate the identifier of the object being
     removed if available (for instance, a keyring serial number).

Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2020-02-12 13:58:35 +00:00
parent b9bbe6ed63
commit 0858caa419
1 changed files with 55 additions and 0 deletions
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55
include/uapi/linux/watch_queue.h Normal file
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/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
#ifndef _UAPI_LINUX_WATCH_QUEUE_H
#define _UAPI_LINUX_WATCH_QUEUE_H
#include <linux/types.h>
enum watch_notification_type {
WATCH_TYPE_META = 0, /* Special record */
WATCH_TYPE__NR = 1
};
enum watch_meta_notification_subtype {
WATCH_META_REMOVAL_NOTIFICATION = 0, /* Watched object was removed */
WATCH_META_LOSS_NOTIFICATION = 1, /* Data loss occurred */
};
/*
* Notification record header. This is aligned to 64-bits so that subclasses
* can contain __u64 fields.
*/
struct watch_notification {
__u32 type:24; /* enum watch_notification_type */
__u32 subtype:8; /* Type-specific subtype (filterable) */
__u32 info;
#define WATCH_INFO_LENGTH 0x0000007f /* Length of record */
#define WATCH_INFO_LENGTH__SHIFT 0
#define WATCH_INFO_ID 0x0000ff00 /* ID of watchpoint */
#define WATCH_INFO_ID__SHIFT 8
#define WATCH_INFO_TYPE_INFO 0xffff0000 /* Type-specific info */
#define WATCH_INFO_TYPE_INFO__SHIFT 16
#define WATCH_INFO_FLAG_0 0x00010000 /* Type-specific info, flag bit 0 */
#define WATCH_INFO_FLAG_1 0x00020000 /* ... */
#define WATCH_INFO_FLAG_2 0x00040000
#define WATCH_INFO_FLAG_3 0x00080000
#define WATCH_INFO_FLAG_4 0x00100000
#define WATCH_INFO_FLAG_5 0x00200000
#define WATCH_INFO_FLAG_6 0x00400000
#define WATCH_INFO_FLAG_7 0x00800000
};
/*
* Extended watch removal notification. This is used optionally if the type
* wants to indicate an identifier for the object being watched, if there is
* such. This can be distinguished by the length.
*
* type -> WATCH_TYPE_META
* subtype -> WATCH_META_REMOVAL_NOTIFICATION
*/
struct watch_notification_removal {
struct watch_notification watch;
__u64 id; /* Type-dependent identifier */
};
#endif /* _UAPI_LINUX_WATCH_QUEUE_H */