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 */
73 void
kmdb_wr_debugger_notify(void * arg)74 kmdb_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 */
115 int
kmdb_wr_debugger_process(int (* cb)(kmdb_wr_t *,void *),void * arg)116 kmdb_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 */
146 int
kmdb_wr_debugger_notify_isempty(void)147 kmdb_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 */
156 void
kmdb_wr_driver_notify(void * arg)157 kmdb_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 */
183 int
kmdb_wr_driver_process(int (* cb)(kmdb_wr_t *,void *),void * arg)184 kmdb_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 */
220 int
kmdb_wr_driver_notify_isempty(void)221 kmdb_wr_driver_notify_isempty(void)
222 {
223 return (mdb.m_drvwrhead == NULL);
224 }
225