xref: /illumos-gate/usr/src/cmd/mdb/common/kmdb/kmdb_wr.c (revision 2a8bcb4efb45d99ac41c94a75c396b362c414f7f)
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 /*
28  * The communication mechanism for requesting that the driver perform work on
29  * behalf of the debugger.  Messages are passed and processed in FIFO order,
30  * with no provision for high priority messages.  High priority messages, such
31  * as debugger termination requests, should be passed using a different
32  * mechanism.
33  *
34  * Two FIFO queues are used for communication - one from the debugger to the
35  * driver, known as the driver_notify queue, and one from the driver to the
36  * debugger, known as the debugger_notify queue.  Messages are added to one
37  * queue, processed by the party on the other end, and are sent back as
38  * acknowledgements on the other queue.  All messages must be acknowledged, in
39  * part because the party who sent the message is the only one who can free it.
40  *
41  * Debugger-initiated work requests are usually triggered by dcmds such as
42  * ::load.  In the case of a ::load, the debugger adds a load request to the
43  * driver_notify queue.  The driver removes the request from the queue and
44  * processes it.  When processing is complete, the message is turned into an
45  * acknowledgement, and completion status is added.  The message is then added
46  * to the debugger_notify queue.  Upon receipt, the debugger removes the
47  * message from the queue, notes the completion status, and frees it.
48  *
49  * The driver can itself initiate unsolicited work, such as the automatic
50  * loading of a dmod in response to a krtld module load notification.  In this
51  * case, the driver loads the module and creates a work-completion message.
52  * This completion is identical to the one sent in the solicited load case
53  * above, with the exception of the acknowledgement bit, which isn't be set.
54  * When the debugger receives the completion message, it notes the completion
55  * status, and sends the message back to the driver via the driver_notify queue,
56  * this time with the acknowledgement bit set.
57  */
58 
59 #include <sys/types.h>
60 
61 #include <kmdb/kmdb_asmutil.h>
62 #include <kmdb/kmdb_wr_impl.h>
63 #include <mdb/mdb_debug.h>
64 #include <mdb/mdb.h>
65 
66 /*
67  * Called by the driver to pass a message to the debugger.  The debugger could
68  * start running at any time.  Nodes are added to the queue in FIFO order, but
69  * with links pointing in reverse order.
70  */
71 void
kmdb_wr_debugger_notify(void * arg)72 kmdb_wr_debugger_notify(void *arg)
73 {
74 	kmdb_wr_t *new = arg;
75 	kmdb_wr_t *curtail;
76 
77 	new->wn_next = new->wn_prev = NULL;
78 	membar_producer();
79 
80 	do {
81 		if ((curtail = mdb.m_dbgwrtail) == NULL) {
82 			/*
83 			 * The queue is empty, because tail will only be NULL if
84 			 * head is NULL too.  We're the only one who can add
85 			 * to the queue, so we can blindly add our node.  The
86 			 * debugger can't look at tail until head is non-NULL,
87 			 * so we set tail first.
88 			 */
89 			mdb.m_dbgwrtail = new;
90 			membar_producer();
91 			mdb.m_dbgwrhead = new;
92 			membar_producer();
93 			break;
94 		}
95 
96 		/*
97 		 * Point the new node at the current tail.  Attempt to set tail
98 		 * to point to our new node, but only as long as tail is what
99 		 * we think it is.
100 		 */
101 		new->wn_prev = curtail;
102 		membar_producer();
103 	} while (cas((uintptr_t *)&mdb.m_dbgwrtail, (uintptr_t)curtail,
104 	    (uintptr_t)new) != (uintptr_t)curtail);
105 }
106 
107 /*
108  * Called by the debugger to receive messages from the driver.  The driver
109  * has added the nodes in FIFO order, but has only set the prev pointers.  We
110  * have to correct that before processing the nodes.  This routine will not
111  * be preempted.
112  */
113 int
kmdb_wr_debugger_process(int (* cb)(kmdb_wr_t *,void *),void * arg)114 kmdb_wr_debugger_process(int (*cb)(kmdb_wr_t *, void *), void *arg)
115 {
116 	kmdb_wr_t *wn, *wnn;
117 	int i;
118 
119 	if (mdb.m_dbgwrhead == NULL)
120 		return (0); /* The queue is empty, so there's nothing to do */
121 
122 	/* Re-establish the next links so we can traverse in FIFO order */
123 	mdb.m_dbgwrtail->wn_next = NULL;
124 	for (wn = mdb.m_dbgwrtail; wn->wn_prev != NULL;
125 	    wn = wn->wn_prev)
126 		wn->wn_prev->wn_next = wn;
127 
128 	/* We don't own wn after we've invoked the callback */
129 	wn = mdb.m_dbgwrhead;
130 	i = 0;
131 	do {
132 		wnn = wn->wn_next;
133 		i += cb(wn, arg);
134 	} while ((wn = wnn) != NULL);
135 
136 	mdb.m_dbgwrhead = mdb.m_dbgwrtail = NULL;
137 
138 	return (i);
139 }
140 
141 /*
142  * Called by the debugger to check queue status.
143  */
144 int
kmdb_wr_debugger_notify_isempty(void)145 kmdb_wr_debugger_notify_isempty(void)
146 {
147 	return (mdb.m_dbgwrhead == NULL);
148 }
149 
150 /*
151  * Called by the debugger to pass a message to the driver.  This routine will
152  * not be preempted.
153  */
154 void
kmdb_wr_driver_notify(void * arg)155 kmdb_wr_driver_notify(void *arg)
156 {
157 	kmdb_wr_t *new = arg;
158 
159 	/*
160 	 * We restrict ourselves to manipulating the rear of the queue.  We
161 	 * don't look at the head unless the tail is NULL.
162 	 */
163 	if (mdb.m_drvwrtail == NULL) {
164 		new->wn_next = new->wn_prev = NULL;
165 		mdb.m_drvwrhead = mdb.m_drvwrtail = new;
166 	} else {
167 		mdb.m_drvwrtail->wn_next = new;
168 		new->wn_prev = mdb.m_drvwrtail;
169 		new->wn_next = NULL;
170 		mdb.m_drvwrtail = new;
171 	}
172 }
173 
174 /*
175  * Called by the driver to receive messages from the debugger.  The debugger
176  * could start running at any time.
177  *
178  * NOTE: This routine may run *after* mdb_destroy(), and may *NOT* use any MDB
179  * services.
180  */
181 int
kmdb_wr_driver_process(int (* cb)(kmdb_wr_t *,void *),void * arg)182 kmdb_wr_driver_process(int (*cb)(kmdb_wr_t *, void *), void *arg)
183 {
184 	kmdb_wr_t *worklist, *wn, *wnn;
185 	int rc, rv, i;
186 
187 	if ((worklist = mdb.m_drvwrhead) == NULL) {
188 		return (0); /* The queue is empty, so there's nothing to do */
189 	}
190 
191 	mdb.m_drvwrhead = NULL;
192 	/* The debugger uses tail, so enqueues still work */
193 	membar_producer();
194 	mdb.m_drvwrtail = NULL;
195 	membar_producer();
196 
197 	/*
198 	 * The current set of messages has been removed from the queue, so
199 	 * we can process them at our leisure.
200 	 */
201 
202 	wn = worklist;
203 	rc = i = 0;
204 	do {
205 		wnn = wn->wn_next;
206 		if ((rv = cb(wn, arg)) < 0)
207 			rc = -1;
208 		else
209 			i += rv;
210 	} while ((wn = wnn) != NULL);
211 
212 	return (rc == 0 ? i : -1);
213 }
214 
215 /*
216  * Called by the debugger to check queue status
217  */
218 int
kmdb_wr_driver_notify_isempty(void)219 kmdb_wr_driver_notify_isempty(void)
220 {
221 	return (mdb.m_drvwrhead == NULL);
222 }
223