xref: /qemu/replay/replay-debugging.c (revision 2abf0da2) 
1 /*
2  * replay-debugging.c
3  *
4  * Copyright (c) 2010-2020 Institute for System Programming
5  *                         of the Russian Academy of Sciences.
6  *
7  * This work is licensed under the terms of the GNU GPL, version 2 or later.
8  * See the COPYING file in the top-level directory.
9  *
10  */
11 
12 #include "qemu/osdep.h"
13 #include "qapi/error.h"
14 #include "sysemu/replay.h"
15 #include "sysemu/runstate.h"
16 #include "replay-internal.h"
17 #include "monitor/hmp.h"
18 #include "monitor/monitor.h"
19 #include "qapi/qapi-commands-replay.h"
20 #include "qapi/qmp/qdict.h"
21 #include "qemu/timer.h"
22 #include "block/snapshot.h"
23 #include "migration/snapshot.h"
24 
25 static bool replay_is_debugging;
26 static int64_t replay_last_breakpoint;
27 static int64_t replay_last_snapshot;
28 
29 bool replay_running_debug(void)
30 {
31     return replay_is_debugging;
32 }
33 
34 void hmp_info_replay(Monitor *mon, const QDict *qdict)
35 {
36     if (replay_mode == REPLAY_MODE_NONE) {
37         monitor_printf(mon, "Record/replay is not active\n");
38     } else {
39         monitor_printf(mon,
40             "%s execution '%s': instruction count = %"PRId64"\n",
41             replay_mode == REPLAY_MODE_RECORD ? "Recording" : "Replaying",
42             replay_get_filename(), replay_get_current_icount());
43     }
44 }
45 
46 ReplayInfo *qmp_query_replay(Error **errp)
47 {
48     ReplayInfo *retval = g_new0(ReplayInfo, 1);
49 
50     retval->mode = replay_mode;
51     if (replay_get_filename()) {
52         retval->filename = g_strdup(replay_get_filename());
53     }
54     retval->icount = replay_get_current_icount();
55     return retval;
56 }
57 
58 static void replay_break(uint64_t icount, QEMUTimerCB callback, void *opaque)
59 {
60     assert(replay_mode == REPLAY_MODE_PLAY);
61     assert(replay_mutex_locked());
62     assert(replay_break_icount >= replay_get_current_icount());
63     assert(callback);
64 
65     replay_break_icount = icount;
66 
67     if (replay_break_timer) {
68         timer_del(replay_break_timer);
69     }
70     replay_break_timer = timer_new_ns(QEMU_CLOCK_REALTIME,
71                                       callback, opaque);
72 }
73 
74 static void replay_delete_break(void)
75 {
76     assert(replay_mode == REPLAY_MODE_PLAY);
77     assert(replay_mutex_locked());
78 
79     if (replay_break_timer) {
80         timer_free(replay_break_timer);
81         replay_break_timer = NULL;
82     }
83     replay_break_icount = -1ULL;
84 }
85 
86 static void replay_stop_vm(void *opaque)
87 {
88     vm_stop(RUN_STATE_PAUSED);
89     replay_delete_break();
90 }
91 
92 void qmp_replay_break(int64_t icount, Error **errp)
93 {
94     if (replay_mode == REPLAY_MODE_PLAY) {
95         if (icount >= replay_get_current_icount()) {
96             replay_break(icount, replay_stop_vm, NULL);
97         } else {
98             error_setg(errp,
99                 "cannot set breakpoint at the instruction in the past");
100         }
101     } else {
102         error_setg(errp, "setting the breakpoint is allowed only in play mode");
103     }
104 }
105 
106 void hmp_replay_break(Monitor *mon, const QDict *qdict)
107 {
108     int64_t icount = qdict_get_try_int(qdict, "icount", -1LL);
109     Error *err = NULL;
110 
111     qmp_replay_break(icount, &err);
112     if (err) {
113         error_report_err(err);
114         return;
115     }
116 }
117 
118 void qmp_replay_delete_break(Error **errp)
119 {
120     if (replay_mode == REPLAY_MODE_PLAY) {
121         replay_delete_break();
122     } else {
123         error_setg(errp, "replay breakpoints are allowed only in play mode");
124     }
125 }
126 
127 void hmp_replay_delete_break(Monitor *mon, const QDict *qdict)
128 {
129     Error *err = NULL;
130 
131     qmp_replay_delete_break(&err);
132     if (err) {
133         error_report_err(err);
134         return;
135     }
136 }
137 
138 static char *replay_find_nearest_snapshot(int64_t icount,
139                                           int64_t *snapshot_icount)
140 {
141     BlockDriverState *bs;
142     QEMUSnapshotInfo *sn_tab;
143     QEMUSnapshotInfo *nearest = NULL;
144     char *ret = NULL;
145     int rv;
146     int nb_sns, i;
147 
148     *snapshot_icount = -1;
149 
150     bs = bdrv_all_find_vmstate_bs(NULL, false, NULL, NULL);
151     if (!bs) {
152         goto fail;
153     }
154 
155     nb_sns = bdrv_snapshot_list(bs, &sn_tab);
156 
157     for (i = 0; i < nb_sns; i++) {
158         rv = bdrv_all_has_snapshot(sn_tab[i].name, false, NULL, NULL);
159         if (rv < 0)
160             goto fail;
161         if (rv == 1) {
162             if (sn_tab[i].icount != -1ULL
163                 && sn_tab[i].icount <= icount
164                 && (!nearest || nearest->icount < sn_tab[i].icount)) {
165                 nearest = &sn_tab[i];
166             }
167         }
168     }
169     if (nearest) {
170         ret = g_strdup(nearest->name);
171         *snapshot_icount = nearest->icount;
172     }
173     g_free(sn_tab);
174 
175 fail:
176     return ret;
177 }
178 
179 static void replay_seek(int64_t icount, QEMUTimerCB callback, Error **errp)
180 {
181     char *snapshot = NULL;
182     int64_t snapshot_icount;
183 
184     if (replay_mode != REPLAY_MODE_PLAY) {
185         error_setg(errp, "replay must be enabled to seek");
186         return;
187     }
188 
189     snapshot = replay_find_nearest_snapshot(icount, &snapshot_icount);
190     if (snapshot) {
191         if (icount < replay_get_current_icount()
192             || replay_get_current_icount() < snapshot_icount) {
193             vm_stop(RUN_STATE_RESTORE_VM);
194             load_snapshot(snapshot, NULL, false, NULL, errp);
195         }
196         g_free(snapshot);
197     }
198     if (replay_get_current_icount() <= icount) {
199         replay_break(icount, callback, NULL);
200         vm_start();
201     } else {
202         error_setg(errp, "cannot seek to the specified instruction count");
203     }
204 }
205 
206 void qmp_replay_seek(int64_t icount, Error **errp)
207 {
208     replay_seek(icount, replay_stop_vm, errp);
209 }
210 
211 void hmp_replay_seek(Monitor *mon, const QDict *qdict)
212 {
213     int64_t icount = qdict_get_try_int(qdict, "icount", -1LL);
214     Error *err = NULL;
215 
216     qmp_replay_seek(icount, &err);
217     if (err) {
218         error_report_err(err);
219         return;
220     }
221 }
222 
223 static void replay_stop_vm_debug(void *opaque)
224 {
225     replay_is_debugging = false;
226     vm_stop(RUN_STATE_DEBUG);
227     replay_delete_break();
228 }
229 
230 bool replay_reverse_step(void)
231 {
232     Error *err = NULL;
233 
234     assert(replay_mode == REPLAY_MODE_PLAY);
235 
236     if (replay_get_current_icount() != 0) {
237         replay_seek(replay_get_current_icount() - 1,
238                     replay_stop_vm_debug, &err);
239         if (err) {
240             error_free(err);
241             return false;
242         }
243         replay_is_debugging = true;
244         return true;
245     }
246 
247     return false;
248 }
249 
250 static void replay_continue_end(void)
251 {
252     replay_is_debugging = false;
253     vm_stop(RUN_STATE_DEBUG);
254     replay_delete_break();
255 }
256 
257 static void replay_continue_stop(void *opaque)
258 {
259     Error *err = NULL;
260     if (replay_last_breakpoint != -1LL) {
261         replay_seek(replay_last_breakpoint, replay_stop_vm_debug, &err);
262         if (err) {
263             error_free(err);
264             replay_continue_end();
265         }
266         return;
267     }
268     /*
269      * No breakpoints since the last snapshot.
270      * Find previous snapshot and try again.
271      */
272     if (replay_last_snapshot != 0) {
273         replay_seek(replay_last_snapshot - 1, replay_continue_stop, &err);
274         if (err) {
275             error_free(err);
276             replay_continue_end();
277         }
278         replay_last_snapshot = replay_get_current_icount();
279     } else {
280         /* Seek to the very first step */
281         replay_seek(0, replay_stop_vm_debug, &err);
282         if (err) {
283             error_free(err);
284             replay_continue_end();
285         }
286     }
287 }
288 
289 bool replay_reverse_continue(void)
290 {
291     Error *err = NULL;
292 
293     assert(replay_mode == REPLAY_MODE_PLAY);
294 
295     if (replay_get_current_icount() != 0) {
296         replay_seek(replay_get_current_icount() - 1,
297                     replay_continue_stop, &err);
298         if (err) {
299             error_free(err);
300             return false;
301         }
302         replay_last_breakpoint = -1LL;
303         replay_is_debugging = true;
304         replay_last_snapshot = replay_get_current_icount();
305         return true;
306     }
307 
308     return false;
309 }
310 
311 void replay_breakpoint(void)
312 {
313     assert(replay_mode == REPLAY_MODE_PLAY);
314     replay_last_breakpoint = replay_get_current_icount();
315 }
316 
317 void replay_gdb_attached(void)
318 {
319     /*
320      * Create VM snapshot on temporary overlay to allow reverse
321      * debugging even if snapshots were not enabled.
322      */
323     if (replay_mode == REPLAY_MODE_PLAY
324         && !replay_snapshot) {
325         if (!save_snapshot("start_debugging", true, NULL, false, NULL, NULL)) {
326             /* Can't create the snapshot. Continue conventional debugging. */
327         }
328     }
329 }
330