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 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 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 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 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 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 219 kmdb_wr_driver_notify_isempty(void) 220 { 221 return (mdb.m_drvwrhead == NULL); 222 } 223