1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License, Version 1.0 only
6 * (the "License").  You may not use this file except in compliance
7 * with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://www.opensolaris.org/os/licensing.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22/*
23 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
24 * Use is subject to license terms.
25 */
26
27#pragma ident	"%Z%%M%	%I%	%E% SMI"
28
29/*
30 * The communication mechanism for requesting that the driver perform work on
31 * behalf of the debugger.  Messages are passed and processed in FIFO order,
32 * with no provision for high priority messages.  High priority messages, such
33 * as debugger termination requests, should be passed using a different
34 * mechanism.
35 *
36 * Two FIFO queues are used for communication - one from the debugger to the
37 * driver, known as the driver_notify queue, and one from the driver to the
38 * debugger, known as the debugger_notify queue.  Messages are added to one
39 * queue, processed by the party on the other end, and are sent back as
40 * acknowledgements on the other queue.  All messages must be acknowledged, in
41 * part because the party who sent the message is the only one who can free it.
42 *
43 * Debugger-initiated work requests are usually triggered by dcmds such as
44 * ::load.  In the case of a ::load, the debugger adds a load request to the
45 * driver_notify queue.  The driver removes the request from the queue and
46 * processes it.  When processing is complete, the message is turned into an
47 * acknowledgement, and completion status is added.  The message is then added
48 * to the debugger_notify queue.  Upon receipt, the debugger removes the
49 * message from the queue, notes the completion status, and frees it.
50 *
51 * The driver can itself initiate unsolicited work, such as the automatic
52 * loading of a dmod in response to a krtld module load notification.  In this
53 * case, the driver loads the module and creates a work-completion message.
54 * This completion is identical to the one sent in the solicited load case
55 * above, with the exception of the acknowledgement bit, which isn't be set.
56 * When the debugger receives the completion message, it notes the completion
57 * status, and sends the message back to the driver via the driver_notify queue,
58 * this time with the acknowledgement bit set.
59 */
60
61#include <sys/types.h>
62
63#include <kmdb/kmdb_asmutil.h>
64#include <kmdb/kmdb_wr_impl.h>
65#include <mdb/mdb_debug.h>
66#include <mdb/mdb.h>
67
68/*
69 * Called by the driver to pass a message to the debugger.  The debugger could
70 * start running at any time.  Nodes are added to the queue in FIFO order, but
71 * with links pointing in reverse order.
72 */
73void
74kmdb_wr_debugger_notify(void *arg)
75{
76	kmdb_wr_t *new = arg;
77	kmdb_wr_t *curtail;
78
79	new->wn_next = new->wn_prev = NULL;
80	membar_producer();
81
82	do {
83		if ((curtail = mdb.m_dbgwrtail) == NULL) {
84			/*
85			 * The queue is empty, because tail will only be NULL if
86			 * head is NULL too.  We're the only one who can add
87			 * to the queue, so we can blindly add our node.  The
88			 * debugger can't look at tail until head is non-NULL,
89			 * so we set tail first.
90			 */
91			mdb.m_dbgwrtail = new;
92			membar_producer();
93			mdb.m_dbgwrhead = new;
94			membar_producer();
95			break;
96		}
97
98		/*
99		 * Point the new node at the current tail.  Attempt to set tail
100		 * to point to our new node, but only as long as tail is what
101		 * we think it is.
102		 */
103		new->wn_prev = curtail;
104		membar_producer();
105	} while (cas((uintptr_t *)&mdb.m_dbgwrtail, (uintptr_t)curtail,
106	    (uintptr_t)new) != (uintptr_t)curtail);
107}
108
109/*
110 * Called by the debugger to receive messages from the driver.  The driver
111 * has added the nodes in FIFO order, but has only set the prev pointers.  We
112 * have to correct that before processing the nodes.  This routine will not
113 * be preempted.
114 */
115int
116kmdb_wr_debugger_process(int (*cb)(kmdb_wr_t *, void *), void *arg)
117{
118	kmdb_wr_t *wn, *wnn;
119	int i;
120
121	if (mdb.m_dbgwrhead == NULL)
122		return (0); /* The queue is empty, so there's nothing to do */
123
124	/* Re-establish the next links so we can traverse in FIFO order */
125	mdb.m_dbgwrtail->wn_next = NULL;
126	for (wn = mdb.m_dbgwrtail; wn->wn_prev != NULL;
127	    wn = wn->wn_prev)
128		wn->wn_prev->wn_next = wn;
129
130	/* We don't own wn after we've invoked the callback */
131	wn = mdb.m_dbgwrhead;
132	i = 0;
133	do {
134		wnn = wn->wn_next;
135		i += cb(wn, arg);
136	} while ((wn = wnn) != NULL);
137
138	mdb.m_dbgwrhead = mdb.m_dbgwrtail = NULL;
139
140	return (i);
141}
142
143/*
144 * Called by the debugger to check queue status.
145 */
146int
147kmdb_wr_debugger_notify_isempty(void)
148{
149	return (mdb.m_dbgwrhead == NULL);
150}
151
152/*
153 * Called by the debugger to pass a message to the driver.  This routine will
154 * not be preempted.
155 */
156void
157kmdb_wr_driver_notify(void *arg)
158{
159	kmdb_wr_t *new = arg;
160
161	/*
162	 * We restrict ourselves to manipulating the rear of the queue.  We
163	 * don't look at the head unless the tail is NULL.
164	 */
165	if (mdb.m_drvwrtail == NULL) {
166		new->wn_next = new->wn_prev = NULL;
167		mdb.m_drvwrhead = mdb.m_drvwrtail = new;
168	} else {
169		mdb.m_drvwrtail->wn_next = new;
170		new->wn_prev = mdb.m_drvwrtail;
171		new->wn_next = NULL;
172		mdb.m_drvwrtail = new;
173	}
174}
175
176/*
177 * Called by the driver to receive messages from the debugger.  The debugger
178 * could start running at any time.
179 *
180 * NOTE: This routine may run *after* mdb_destroy(), and may *NOT* use any MDB
181 * services.
182 */
183int
184kmdb_wr_driver_process(int (*cb)(kmdb_wr_t *, void *), void *arg)
185{
186	kmdb_wr_t *worklist, *wn, *wnn;
187	int rc, rv, i;
188
189	if ((worklist = mdb.m_drvwrhead) == NULL) {
190		return (0); /* The queue is empty, so there's nothing to do */
191	}
192
193	mdb.m_drvwrhead = NULL;
194	/* The debugger uses tail, so enqueues still work */
195	membar_producer();
196	mdb.m_drvwrtail = NULL;
197	membar_producer();
198
199	/*
200	 * The current set of messages has been removed from the queue, so
201	 * we can process them at our leisure.
202	 */
203
204	wn = worklist;
205	rc = i = 0;
206	do {
207		wnn = wn->wn_next;
208		if ((rv = cb(wn, arg)) < 0)
209			rc = -1;
210		else
211			i += rv;
212	} while ((wn = wnn) != NULL);
213
214	return (rc == 0 ? i : -1);
215}
216
217/*
218 * Called by the debugger to check queue status
219 */
220int
221kmdb_wr_driver_notify_isempty(void)
222{
223	return (mdb.m_drvwrhead == NULL);
224}
225