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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 02/13] uapi: General notification ring definitions [ver #4] From: David Howells To: viro@zeniv.linux.org.uk Cc: dhowells@redhat.com, raven@themaw.net, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-block@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Date: Fri, 07 Jun 2019 15:17:40 +0100 Message-ID: <155991706083.15579.16359443779582362339.stgit@warthog.procyon.org.uk> In-Reply-To: <155991702981.15579.6007568669839441045.stgit@warthog.procyon.org.uk> References: <155991702981.15579.6007568669839441045.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Fri, 07 Jun 2019 14:17:43 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP Add UAPI definitions for the general notification ring, including the following pieces: (1) struct watch_notification. This is the metadata header for each entry in the ring. 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_OVERRUN. If preceding messages were lost due to ring overrun or lack of memory. - WATCH_INFO_ENOMEM. If preceding messages were lost due to lack of memory. - WATCH_INFO_RECURSIVE. If the event detected was applied to multiple objects (eg. a recursive change to mount attributes). - WATCH_INFO_IN_SUBTREE. If the event didn't happen at the watched object, but rather to some related object (eg. a subtree mount watch saw a mount happen somewhere within the subtree). - WATCH_INFO_TYPE_FLAGS. Eight flags whose meanings depend on the message type. - WATCH_INFO_ID. The watch ID specified when the watchpoint was set. All the information in the header can be used in filtering messages at the point of writing into the buffer. (2) struct watch_queue_buffer. This describes the layout of the ring. Note that the first slots in the ring contain a special metadata entry that contains the ring pointers. The producer in the kernel knows to skip this and it has a proper header (WATCH_TYPE_META, WATCH_META_SKIP_NOTIFICATION) that indicates the size so that the ring consumer can handle it the same as any other record and just skip it. Note that this means that ring entries can never be split over the end of the ring, so if an entry would need to be split, a skip record is inserted to wrap the ring first; this is also WATCH_TYPE_META, WATCH_META_SKIP_NOTIFICATION. Signed-off-by: David Howells --- include/uapi/linux/watch_queue.h | 63 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 include/uapi/linux/watch_queue.h diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h new file mode 100644 index 000000000000..c3a88fa5f62a --- /dev/null +++ b/include/uapi/linux/watch_queue.h @@ -0,0 +1,63 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef _UAPI_LINUX_WATCH_QUEUE_H +#define _UAPI_LINUX_WATCH_QUEUE_H + +#include + +enum watch_notification_type { + WATCH_TYPE_META = 0, /* Special record */ + WATCH_TYPE_MOUNT_NOTIFY = 1, /* Mount notification record */ + WATCH_TYPE_SB_NOTIFY = 2, /* Superblock notification */ + WATCH_TYPE_KEY_NOTIFY = 3, /* Key/keyring change notification */ + WATCH_TYPE_BLOCK_NOTIFY = 4, /* Block layer notifications */ +#define WATCH_TYPE___NR 5 +}; + +enum watch_meta_notification_subtype { + WATCH_META_SKIP_NOTIFICATION = 0, /* Just skip this record */ + WATCH_META_REMOVAL_NOTIFICATION = 1, /* Watched object was removed */ +}; + +/* + * Notification record + */ +struct watch_notification { + __u32 type:24; /* enum watch_notification_type */ + __u32 subtype:8; /* Type-specific subtype (filterable) */ + __u32 info; +#define WATCH_INFO_OVERRUN 0x00000001 /* Event(s) lost due to overrun */ +#define WATCH_INFO_ENOMEM 0x00000002 /* Event(s) lost due to ENOMEM */ +#define WATCH_INFO_RECURSIVE 0x00000004 /* Change was recursive */ +#define WATCH_INFO_LENGTH 0x000001f8 /* Length of record / sizeof(watch_notification) */ +#define WATCH_INFO_IN_SUBTREE 0x00000200 /* Change was not at watched root */ +#define WATCH_INFO_TYPE_FLAGS 0x00ff0000 /* Type-specific flags */ +#define WATCH_INFO_FLAG_0 0x00010000 +#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 +#define WATCH_INFO_ID 0xff000000 /* ID of watchpoint */ +#define WATCH_INFO_ID__SHIFT 24 +}; + +#define WATCH_LENGTH_SHIFT 3 + +struct watch_queue_buffer { + union { + /* The first few entries are special, containing the + * ring management variables. + */ + struct { + struct watch_notification watch; /* WATCH_TYPE_META */ + __u32 head; /* Ring head index */ + __u32 tail; /* Ring tail index */ + __u32 mask; /* Ring index mask */ + } meta; + struct watch_notification slots[0]; + }; +}; + +#endif /* _UAPI_LINUX_WATCH_QUEUE_H */