xref: /qemu/replay/replay-debugging.c (revision 84615a19) 
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     AioContext *aio_context;
148 
149     *snapshot_icount = -1;
150 
151     bs = bdrv_all_find_vmstate_bs(NULL, false, NULL, NULL);
152     if (!bs) {
153         goto fail;
154     }
155     aio_context = bdrv_get_aio_context(bs);
156 
157     aio_context_acquire(aio_context);
158     nb_sns = bdrv_snapshot_list(bs, &sn_tab);
159     aio_context_release(aio_context);
160 
161     for (i = 0; i < nb_sns; i++) {
162         rv = bdrv_all_has_snapshot(sn_tab[i].name, false, NULL, NULL);
163         if (rv < 0)
164             goto fail;
165         if (rv == 1) {
166             if (sn_tab[i].icount != -1ULL
167                 && sn_tab[i].icount <= icount
168                 && (!nearest || nearest->icount < sn_tab[i].icount)) {
169                 nearest = &sn_tab[i];
170             }
171         }
172     }
173     if (nearest) {
174         ret = g_strdup(nearest->name);
175         *snapshot_icount = nearest->icount;
176     }
177     g_free(sn_tab);
178 
179 fail:
180     return ret;
181 }
182 
183 static void replay_seek(int64_t icount, QEMUTimerCB callback, Error **errp)
184 {
185     char *snapshot = NULL;
186     int64_t snapshot_icount;
187 
188     if (replay_mode != REPLAY_MODE_PLAY) {
189         error_setg(errp, "replay must be enabled to seek");
190         return;
191     }
192 
193     snapshot = replay_find_nearest_snapshot(icount, &snapshot_icount);
194     if (snapshot) {
195         if (icount < replay_get_current_icount()
196             || replay_get_current_icount() < snapshot_icount) {
197             vm_stop(RUN_STATE_RESTORE_VM);
198             load_snapshot(snapshot, NULL, false, NULL, errp);
199         }
200         g_free(snapshot);
201     }
202     if (replay_get_current_icount() <= icount) {
203         replay_break(icount, callback, NULL);
204         vm_start();
205     } else {
206         error_setg(errp, "cannot seek to the specified instruction count");
207     }
208 }
209 
210 void qmp_replay_seek(int64_t icount, Error **errp)
211 {
212     replay_seek(icount, replay_stop_vm, errp);
213 }
214 
215 void hmp_replay_seek(Monitor *mon, const QDict *qdict)
216 {
217     int64_t icount = qdict_get_try_int(qdict, "icount", -1LL);
218     Error *err = NULL;
219 
220     qmp_replay_seek(icount, &err);
221     if (err) {
222         error_report_err(err);
223         return;
224     }
225 }
226 
227 static void replay_stop_vm_debug(void *opaque)
228 {
229     replay_is_debugging = false;
230     vm_stop(RUN_STATE_DEBUG);
231     replay_delete_break();
232 }
233 
234 bool replay_reverse_step(void)
235 {
236     Error *err = NULL;
237 
238     assert(replay_mode == REPLAY_MODE_PLAY);
239 
240     if (replay_get_current_icount() != 0) {
241         replay_seek(replay_get_current_icount() - 1,
242                     replay_stop_vm_debug, &err);
243         if (err) {
244             error_free(err);
245             return false;
246         }
247         replay_is_debugging = true;
248         return true;
249     }
250 
251     return false;
252 }
253 
254 static void replay_continue_end(void)
255 {
256     replay_is_debugging = false;
257     vm_stop(RUN_STATE_DEBUG);
258     replay_delete_break();
259 }
260 
261 static void replay_continue_stop(void *opaque)
262 {
263     Error *err = NULL;
264     if (replay_last_breakpoint != -1LL) {
265         replay_seek(replay_last_breakpoint, replay_stop_vm_debug, &err);
266         if (err) {
267             error_free(err);
268             replay_continue_end();
269         }
270         return;
271     }
272     /*
273      * No breakpoints since the last snapshot.
274      * Find previous snapshot and try again.
275      */
276     if (replay_last_snapshot != 0) {
277         replay_seek(replay_last_snapshot - 1, replay_continue_stop, &err);
278         if (err) {
279             error_free(err);
280             replay_continue_end();
281         }
282         replay_last_snapshot = replay_get_current_icount();
283     } else {
284         /* Seek to the very first step */
285         replay_seek(0, replay_stop_vm_debug, &err);
286         if (err) {
287             error_free(err);
288             replay_continue_end();
289         }
290     }
291 }
292 
293 bool replay_reverse_continue(void)
294 {
295     Error *err = NULL;
296 
297     assert(replay_mode == REPLAY_MODE_PLAY);
298 
299     if (replay_get_current_icount() != 0) {
300         replay_seek(replay_get_current_icount() - 1,
301                     replay_continue_stop, &err);
302         if (err) {
303             error_free(err);
304             return false;
305         }
306         replay_last_breakpoint = -1LL;
307         replay_is_debugging = true;
308         replay_last_snapshot = replay_get_current_icount();
309         return true;
310     }
311 
312     return false;
313 }
314 
315 void replay_breakpoint(void)
316 {
317     assert(replay_mode == REPLAY_MODE_PLAY);
318     replay_last_breakpoint = replay_get_current_icount();
319 }
320 
321 void replay_gdb_attached(void)
322 {
323     /*
324      * Create VM snapshot on temporary overlay to allow reverse
325      * debugging even if snapshots were not enabled.
326      */
327     if (replay_mode == REPLAY_MODE_PLAY
328         && !replay_snapshot) {
329         if (!save_snapshot("start_debugging", true, NULL, false, NULL, NULL)) {
330             /* Can't create the snapshot. Continue conventional debugging. */
331         }
332     }
333 }
334