xref: /qemu/replay/replay-debugging.c (revision 2e8f72ac) 
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         retval->has_filename = true;
54     }
55     retval->icount = replay_get_current_icount();
56     return retval;
57 }
58 
59 static void replay_break(uint64_t icount, QEMUTimerCB callback, void *opaque)
60 {
61     assert(replay_mode == REPLAY_MODE_PLAY);
62     assert(replay_mutex_locked());
63     assert(replay_break_icount >= replay_get_current_icount());
64     assert(callback);
65 
66     replay_break_icount = icount;
67 
68     if (replay_break_timer) {
69         timer_del(replay_break_timer);
70     }
71     replay_break_timer = timer_new_ns(QEMU_CLOCK_REALTIME,
72                                       callback, opaque);
73 }
74 
75 static void replay_delete_break(void)
76 {
77     assert(replay_mode == REPLAY_MODE_PLAY);
78     assert(replay_mutex_locked());
79 
80     if (replay_break_timer) {
81         timer_free(replay_break_timer);
82         replay_break_timer = NULL;
83     }
84     replay_break_icount = -1ULL;
85 }
86 
87 static void replay_stop_vm(void *opaque)
88 {
89     vm_stop(RUN_STATE_PAUSED);
90     replay_delete_break();
91 }
92 
93 void qmp_replay_break(int64_t icount, Error **errp)
94 {
95     if (replay_mode == REPLAY_MODE_PLAY) {
96         if (icount >= replay_get_current_icount()) {
97             replay_break(icount, replay_stop_vm, NULL);
98         } else {
99             error_setg(errp,
100                 "cannot set breakpoint at the instruction in the past");
101         }
102     } else {
103         error_setg(errp, "setting the breakpoint is allowed only in play mode");
104     }
105 }
106 
107 void hmp_replay_break(Monitor *mon, const QDict *qdict)
108 {
109     int64_t icount = qdict_get_try_int(qdict, "icount", -1LL);
110     Error *err = NULL;
111 
112     qmp_replay_break(icount, &err);
113     if (err) {
114         error_report_err(err);
115         return;
116     }
117 }
118 
119 void qmp_replay_delete_break(Error **errp)
120 {
121     if (replay_mode == REPLAY_MODE_PLAY) {
122         replay_delete_break();
123     } else {
124         error_setg(errp, "replay breakpoints are allowed only in play mode");
125     }
126 }
127 
128 void hmp_replay_delete_break(Monitor *mon, const QDict *qdict)
129 {
130     Error *err = NULL;
131 
132     qmp_replay_delete_break(&err);
133     if (err) {
134         error_report_err(err);
135         return;
136     }
137 }
138 
139 static char *replay_find_nearest_snapshot(int64_t icount,
140                                           int64_t *snapshot_icount)
141 {
142     BlockDriverState *bs;
143     QEMUSnapshotInfo *sn_tab;
144     QEMUSnapshotInfo *nearest = NULL;
145     char *ret = NULL;
146     int nb_sns, i;
147     AioContext *aio_context;
148 
149     *snapshot_icount = -1;
150 
151     bs = bdrv_all_find_vmstate_bs();
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         if (bdrv_all_find_snapshot(sn_tab[i].name, &bs) == 0) {
163             if (sn_tab[i].icount != -1ULL
164                 && sn_tab[i].icount <= icount
165                 && (!nearest || nearest->icount < sn_tab[i].icount)) {
166                 nearest = &sn_tab[i];
167             }
168         }
169     }
170     if (nearest) {
171         ret = g_strdup(nearest->name);
172         *snapshot_icount = nearest->icount;
173     }
174     g_free(sn_tab);
175 
176 fail:
177     return ret;
178 }
179 
180 static void replay_seek(int64_t icount, QEMUTimerCB callback, Error **errp)
181 {
182     char *snapshot = NULL;
183     int64_t snapshot_icount;
184 
185     if (replay_mode != REPLAY_MODE_PLAY) {
186         error_setg(errp, "replay must be enabled to seek");
187         return;
188     }
189 
190     snapshot = replay_find_nearest_snapshot(icount, &snapshot_icount);
191     if (snapshot) {
192         if (icount < replay_get_current_icount()
193             || replay_get_current_icount() < snapshot_icount) {
194             vm_stop(RUN_STATE_RESTORE_VM);
195             load_snapshot(snapshot, errp);
196         }
197         g_free(snapshot);
198     }
199     if (replay_get_current_icount() <= icount) {
200         replay_break(icount, callback, NULL);
201         vm_start();
202     } else {
203         error_setg(errp, "cannot seek to the specified instruction count");
204     }
205 }
206 
207 void qmp_replay_seek(int64_t icount, Error **errp)
208 {
209     replay_seek(icount, replay_stop_vm, errp);
210 }
211 
212 void hmp_replay_seek(Monitor *mon, const QDict *qdict)
213 {
214     int64_t icount = qdict_get_try_int(qdict, "icount", -1LL);
215     Error *err = NULL;
216 
217     qmp_replay_seek(icount, &err);
218     if (err) {
219         error_report_err(err);
220         return;
221     }
222 }
223 
224 static void replay_stop_vm_debug(void *opaque)
225 {
226     replay_is_debugging = false;
227     vm_stop(RUN_STATE_DEBUG);
228     replay_delete_break();
229 }
230 
231 bool replay_reverse_step(void)
232 {
233     Error *err = NULL;
234 
235     assert(replay_mode == REPLAY_MODE_PLAY);
236 
237     if (replay_get_current_icount() != 0) {
238         replay_seek(replay_get_current_icount() - 1,
239                     replay_stop_vm_debug, &err);
240         if (err) {
241             error_free(err);
242             return false;
243         }
244         replay_is_debugging = true;
245         return true;
246     }
247 
248     return false;
249 }
250 
251 static void replay_continue_end(void)
252 {
253     replay_is_debugging = false;
254     vm_stop(RUN_STATE_DEBUG);
255     replay_delete_break();
256 }
257 
258 static void replay_continue_stop(void *opaque)
259 {
260     Error *err = NULL;
261     if (replay_last_breakpoint != -1LL) {
262         replay_seek(replay_last_breakpoint, replay_stop_vm_debug, &err);
263         if (err) {
264             error_free(err);
265             replay_continue_end();
266         }
267         return;
268     }
269     /*
270      * No breakpoints since the last snapshot.
271      * Find previous snapshot and try again.
272      */
273     if (replay_last_snapshot != 0) {
274         replay_seek(replay_last_snapshot - 1, replay_continue_stop, &err);
275         if (err) {
276             error_free(err);
277             replay_continue_end();
278         }
279         replay_last_snapshot = replay_get_current_icount();
280     } else {
281         /* Seek to the very first step */
282         replay_seek(0, replay_stop_vm_debug, &err);
283         if (err) {
284             error_free(err);
285             replay_continue_end();
286         }
287     }
288 }
289 
290 bool replay_reverse_continue(void)
291 {
292     Error *err = NULL;
293 
294     assert(replay_mode == REPLAY_MODE_PLAY);
295 
296     if (replay_get_current_icount() != 0) {
297         replay_seek(replay_get_current_icount() - 1,
298                     replay_continue_stop, &err);
299         if (err) {
300             error_free(err);
301             return false;
302         }
303         replay_last_breakpoint = -1LL;
304         replay_is_debugging = true;
305         replay_last_snapshot = replay_get_current_icount();
306         return true;
307     }
308 
309     return false;
310 }
311 
312 void replay_breakpoint(void)
313 {
314     assert(replay_mode == REPLAY_MODE_PLAY);
315     replay_last_breakpoint = replay_get_current_icount();
316 }
317 
318 void replay_gdb_attached(void)
319 {
320     /*
321      * Create VM snapshot on temporary overlay to allow reverse
322      * debugging even if snapshots were not enabled.
323      */
324     if (replay_mode == REPLAY_MODE_PLAY
325         && !replay_snapshot) {
326         if (save_snapshot("start_debugging", NULL) != 0) {
327             /* Can't create the snapshot. Continue conventional debugging. */
328         }
329     }
330 }
331