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3438 svoboda 1
/*
2
 * Copyright (c) 2008 Jiri Svoboda
3
 * All rights reserved.
4
 *
5
 * Redistribution and use in source and binary forms, with or without
6
 * modification, are permitted provided that the following conditions
7
 * are met:
8
 *
9
 * - Redistributions of source code must retain the above copyright
10
 *   notice, this list of conditions and the following disclaimer.
11
 * - Redistributions in binary form must reproduce the above copyright
12
 *   notice, this list of conditions and the following disclaimer in the
13
 *   documentation and/or other materials provided with the distribution.
14
 * - The name of the author may not be used to endorse or promote products
15
 *   derived from this software without specific prior written permission.
16
 *
17
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27
 */
28
 
29
/** @addtogroup generic
30
 * @{
31
 */
32
 
33
/**
34
 * @file
3474 svoboda 35
 * @brief   Udebug hooks and data structure management.
3438 svoboda 36
 *
3474 svoboda 37
 * Udebug is an interface that makes userspace debuggers possible.
38
 *
3438 svoboda 39
 * Functions in this file are executed directly in each thread, which
40
 * may or may not be the subject of debugging. The udebug_stoppable_begin/end()
41
 * functions are also executed in the clock interrupt handler. To avoid
42
 * deadlock, functions in this file are protected from the interrupt
43
 * by locking the recursive lock THREAD->udebug.int_lock (just an atomic
44
 * variable). This prevents udebug_stoppable_begin/end() from being
45
 * executed in the interrupt handler (they are skipped).
46
 *
47
 * Functions in udebug_ops.c and udebug_ipc.c execute in different threads,
48
 * so they needn't be protected from the (preemptible) interrupt-initiated
49
 * code.
50
 */
51
 
52
#include <synch/waitq.h>
3441 svoboda 53
#include <debug.h>
3438 svoboda 54
#include <udebug/udebug.h>
55
#include <errno.h>
56
#include <arch.h>
57
 
58
static inline void udebug_int_lock(void)
59
{
60
    atomic_inc(&THREAD->udebug.int_lock);
61
}
62
 
63
static inline void udebug_int_unlock(void)
64
{
65
    atomic_dec(&THREAD->udebug.int_lock);
66
}
67
 
3474 svoboda 68
/** Initialize udebug part of task structure.
69
 *
70
 * Called as part of task structure initialization.
71
 * @param ut    Pointer to the structure to initialize.
72
 */
3438 svoboda 73
void udebug_task_init(udebug_task_t *ut)
74
{
75
    mutex_initialize(&ut->lock, MUTEX_PASSIVE);
76
    ut->dt_state = UDEBUG_TS_INACTIVE;
77
    ut->begin_call = NULL;
78
    ut->not_stoppable_count = 0;
79
    ut->evmask = 0;
80
}
81
 
3474 svoboda 82
/** Initialize udebug part of thread structure.
83
 *
84
 * Called as part of thread structure initialization.
85
 * @param ut    Pointer to the structure to initialize.
86
 */
3438 svoboda 87
void udebug_thread_initialize(udebug_thread_t *ut)
88
{
89
    mutex_initialize(&ut->lock, MUTEX_PASSIVE);
90
    waitq_initialize(&ut->go_wq);
91
 
92
    /*
93
     * At the beginning the thread is stoppable, so int_lock be set, too.
94
     */
95
    atomic_set(&ut->int_lock, 1);
96
 
97
    ut->go_call = NULL;
98
    ut->stop = true;
99
    ut->stoppable = true;
100
    ut->debug_active = false;
101
    ut->cur_event = 0; /* none */
102
}
103
 
3474 svoboda 104
/** Wait for a GO message.
105
 *
106
 * When a debugging event occurs in a thread or the thread is stopped,
107
 * this function is called to block the thread until a GO message
108
 * is received.
109
 *
110
 * @param wq    The wait queue used by the thread to wait for GO messages.
111
 */
3438 svoboda 112
static void udebug_wait_for_go(waitq_t *wq)
113
{
114
    int rc;
115
    ipl_t ipl;
116
 
117
    ipl = waitq_sleep_prepare(wq);
118
 
119
    wq->missed_wakeups = 0; /* Enforce blocking. */
120
    rc = waitq_sleep_timeout_unsafe(wq, SYNCH_NO_TIMEOUT, SYNCH_FLAGS_NONE);
121
 
122
    waitq_sleep_finish(wq, rc, ipl);
123
}
124
 
125
/** Do a preliminary check that a debugging session is in progress.
126
 *
3474 svoboda 127
 * This only requires the THREAD->udebug.lock mutex (and not TASK->udebug.lock
128
 * mutex). For an undebugged task, this will never block (while there could be
129
 * collisions by different threads on the TASK mutex), thus improving SMP
130
 * perormance for undebugged tasks.
131
 *
132
 * @return  True if the thread was in a debugging session when the function
133
 *      checked, false otherwise.
3438 svoboda 134
 */
135
static bool udebug_thread_precheck(void)
136
{
137
    bool res;
138
 
139
    mutex_lock(&THREAD->udebug.lock);
140
    res = THREAD->udebug.debug_active;
141
    mutex_unlock(&THREAD->udebug.lock);
142
 
143
    return res;
144
}
145
 
3474 svoboda 146
/** Start of stoppable section.
147
 *
148
 * A stoppable section is a section of code where if the thread can be stoped. In other words,
149
 * if a STOP operation is issued, the thread is guaranteed not to execute
150
 * any userspace instructions until the thread is resumed.
151
 *
152
 * Having stoppable sections is better than having stopping points, since
153
 * a thread can be stopped even when it is blocked indefinitely in a system
154
 * call (whereas it would not reach any stopping point).
155
 */
3438 svoboda 156
void udebug_stoppable_begin(void)
157
{
158
    int nsc;
159
    call_t *db_call, *go_call;
160
 
161
    ASSERT(THREAD);
162
    ASSERT(TASK);
163
 
164
    udebug_int_lock();
165
 
166
    /* Early check for undebugged tasks */
167
    if (!udebug_thread_precheck()) {
168
        udebug_int_unlock();
169
        return;
170
    }
171
 
172
    mutex_lock(&TASK->udebug.lock);
173
 
174
    nsc = --TASK->udebug.not_stoppable_count;
175
 
176
    /* Lock order OK, THREAD->udebug.lock is after TASK->udebug.lock */
177
    mutex_lock(&THREAD->udebug.lock);
178
    ASSERT(THREAD->udebug.stoppable == false);
179
    THREAD->udebug.stoppable = true;
180
 
181
    if (TASK->udebug.dt_state == UDEBUG_TS_BEGINNING && nsc == 0) {
182
        /*
183
         * This was the last non-stoppable thread. Reply to
184
         * DEBUG_BEGIN call.
185
         */
186
 
187
        db_call = TASK->udebug.begin_call;
188
        ASSERT(db_call);
189
 
190
        TASK->udebug.dt_state = UDEBUG_TS_ACTIVE;
191
        TASK->udebug.begin_call = NULL;
192
 
193
        IPC_SET_RETVAL(db_call->data, 0);
194
        ipc_answer(&TASK->answerbox, db_call);     
195
 
196
    } else if (TASK->udebug.dt_state == UDEBUG_TS_ACTIVE) {
197
        /*
198
         * Active debugging session
199
         */
200
 
201
        if (THREAD->udebug.debug_active && THREAD->udebug.stop) {
202
            /*
203
             * Thread was requested to stop - answer go call
204
             */
205
 
206
            /* Make sure nobody takes this call away from us */
207
            go_call = THREAD->udebug.go_call;
208
            THREAD->udebug.go_call = NULL;
209
            ASSERT(go_call);
210
 
211
            IPC_SET_RETVAL(go_call->data, 0);
212
            IPC_SET_ARG1(go_call->data, UDEBUG_EVENT_STOP);
213
 
214
            THREAD->udebug.cur_event = UDEBUG_EVENT_STOP;
215
 
216
                ipc_answer(&TASK->answerbox, go_call);
217
        }
218
    }
219
 
220
    mutex_unlock(&THREAD->udebug.lock);
221
        mutex_unlock(&TASK->udebug.lock);
222
}
223
 
3474 svoboda 224
/** End of a stoppable section.
225
 *
226
 * This is the point where the thread will block if it is stopped.
227
 * (As, by definition, a stopped thread must not leave its stoppable section).
228
 */
3438 svoboda 229
void udebug_stoppable_end(void)
230
{
231
    /* Early check for undebugged tasks */
232
    if (!udebug_thread_precheck()) {
233
        udebug_int_unlock();
234
        return;
235
    }
236
 
237
restart:
238
    mutex_lock(&TASK->udebug.lock);
239
    mutex_lock(&THREAD->udebug.lock);
240
 
241
    if (THREAD->udebug.debug_active &&
242
        THREAD->udebug.stop == true) {
243
        TASK->udebug.begin_call = NULL;
244
        mutex_unlock(&THREAD->udebug.lock);
245
        mutex_unlock(&TASK->udebug.lock);
246
 
247
        udebug_wait_for_go(&THREAD->udebug.go_wq);
248
 
249
        goto restart;
250
        /* must try again - have to lose stoppability atomically */
251
    } else {
252
        ++TASK->udebug.not_stoppable_count;
253
        ASSERT(THREAD->udebug.stoppable == true);
254
        THREAD->udebug.stoppable = false;
255
 
256
        mutex_unlock(&THREAD->udebug.lock);
257
        mutex_unlock(&TASK->udebug.lock);
258
    }
259
 
260
    udebug_int_unlock();
261
}
262
 
263
/** Upon being scheduled to run, check if the current thread should stop.
264
 *
265
 * This function is called from clock(). Preemption is enabled.
266
 * interrupts are disabled, but since this is called after
267
 * being scheduled-in, we can enable them, if we're careful enough
268
 * not to allow arbitrary recursion or deadlock with the thread context.
269
 */
270
void udebug_before_thread_runs(void)
271
{
272
    ipl_t ipl;
273
 
274
    return;
275
    ASSERT(!PREEMPTION_DISABLED);
276
 
277
    /*
278
     * Prevent agains re-entering, such as when preempted inside this
279
     * function.
280
     */
281
    if (atomic_get(&THREAD->udebug.int_lock) != 0)
282
        return;
283
 
284
    udebug_int_lock();
285
 
286
    ipl = interrupts_enable();
287
 
288
    /* Now we're free to do whatever we need (lock mutexes, sleep, etc.) */
289
 
290
    /* Check if we're supposed to stop */
291
    udebug_stoppable_begin();
292
    udebug_stoppable_end();
293
 
294
    interrupts_restore(ipl);
295
 
296
    udebug_int_unlock();
297
}
298
 
3474 svoboda 299
/** Syscall event hook.
300
 *
301
 * Must be called before and after servicing a system call. This generates
302
 * a SYSCALL_B or SYSCALL_E event, depending on the value of @a end_variant.
303
 */
3438 svoboda 304
void udebug_syscall_event(unative_t a1, unative_t a2, unative_t a3,
305
    unative_t a4, unative_t a5, unative_t a6, unative_t id, unative_t rc,
306
    bool end_variant)
307
{
308
    call_t *call;
309
    udebug_event_t etype;
310
 
311
    etype = end_variant ? UDEBUG_EVENT_SYSCALL_E : UDEBUG_EVENT_SYSCALL_B;
312
 
313
    udebug_int_lock();
314
 
315
    /* Early check for undebugged tasks */
316
    if (!udebug_thread_precheck()) {
317
        udebug_int_unlock();
318
        return;
319
    }
320
 
321
    mutex_lock(&TASK->udebug.lock);
322
    mutex_lock(&THREAD->udebug.lock);
323
 
324
    /* Must only generate events when in debugging session and have go */
325
    if (THREAD->udebug.debug_active != true ||
326
        THREAD->udebug.stop == true ||
327
        (TASK->udebug.evmask & UDEBUG_EVMASK(etype)) == 0) {
328
        mutex_unlock(&THREAD->udebug.lock);
329
        mutex_unlock(&TASK->udebug.lock);
330
        return;
331
    }
332
 
333
    //printf("udebug_syscall_event\n");
334
    call = THREAD->udebug.go_call;
335
    THREAD->udebug.go_call = NULL;
336
 
337
    IPC_SET_RETVAL(call->data, 0);
338
    IPC_SET_ARG1(call->data, etype);
339
    IPC_SET_ARG2(call->data, id);
340
    IPC_SET_ARG3(call->data, rc);
341
    //printf("udebug_syscall_event/ipc_answer\n");
342
 
343
    THREAD->udebug.syscall_args[0] = a1;
344
    THREAD->udebug.syscall_args[1] = a2;
345
    THREAD->udebug.syscall_args[2] = a3;
346
    THREAD->udebug.syscall_args[3] = a4;
347
    THREAD->udebug.syscall_args[4] = a5;
348
    THREAD->udebug.syscall_args[5] = a6;
349
 
350
    /*
351
     * Make sure udebug.stop is true when going to sleep
352
     * in case we get woken up by DEBUG_END. (At which
353
     * point it must be back to the initial true value).
354
     */
355
    THREAD->udebug.stop = true;
356
    THREAD->udebug.cur_event = etype;
357
 
358
    ipc_answer(&TASK->answerbox, call);
359
 
360
    mutex_unlock(&THREAD->udebug.lock);
361
    mutex_unlock(&TASK->udebug.lock);
362
 
363
    udebug_wait_for_go(&THREAD->udebug.go_wq);
364
 
365
    udebug_int_unlock();
366
}
367
 
3474 svoboda 368
/** Thread-creation event hook.
369
 *
370
 * Must be called when a new userspace thread is created in the debugged
371
 * task. Generates a THREAD_B event.
372
 *
373
 * @param t Structure of the thread being created. Not locked, as the
374
 *      thread is not executing yet.
375
 */
3438 svoboda 376
void udebug_thread_b_event(struct thread *t)
377
{
378
    call_t *call;
379
 
380
    udebug_int_lock();
381
 
382
    mutex_lock(&TASK->udebug.lock);
383
    mutex_lock(&THREAD->udebug.lock);
384
 
3441 svoboda 385
    LOG("udebug_thread_b_event\n");
386
    LOG("- check state\n");
3438 svoboda 387
 
388
    /* Must only generate events when in debugging session */
389
    if (THREAD->udebug.debug_active != true) {
3441 svoboda 390
        LOG("- debug_active: %s, udebug.stop: %s\n",
3438 svoboda 391
            THREAD->udebug.debug_active ? "yes(+)" : "no(-)",
392
            THREAD->udebug.stop ? "yes(-)" : "no(+)");
393
        mutex_unlock(&THREAD->udebug.lock);
394
        mutex_unlock(&TASK->udebug.lock);
395
        return;
396
    }
397
 
3441 svoboda 398
    LOG("- trigger event\n");
3438 svoboda 399
 
400
    call = THREAD->udebug.go_call;
401
    THREAD->udebug.go_call = NULL;
402
    IPC_SET_RETVAL(call->data, 0);
403
    IPC_SET_ARG1(call->data, UDEBUG_EVENT_THREAD_B);
404
    IPC_SET_ARG2(call->data, (unative_t)t);
405
 
406
    /*
407
     * Make sure udebug.stop is true when going to sleep
408
     * in case we get woken up by DEBUG_END. (At which
409
     * point it must be back to the initial true value).
410
     */
411
    THREAD->udebug.stop = true;
412
    THREAD->udebug.cur_event = UDEBUG_EVENT_THREAD_B;
413
 
414
    ipc_answer(&TASK->answerbox, call);
415
 
416
    mutex_unlock(&THREAD->udebug.lock);
417
    mutex_unlock(&TASK->udebug.lock);
418
 
3441 svoboda 419
    LOG("- sleep\n");
3438 svoboda 420
    udebug_wait_for_go(&THREAD->udebug.go_wq);
421
 
422
    udebug_int_unlock();
423
}
424
 
3474 svoboda 425
/** Thread-termination event hook.
426
 *
427
 * Must be called when the current thread is terminating.
428
 * Generates a THREAD_E event.
429
 */
3438 svoboda 430
void udebug_thread_e_event(void)
431
{
432
    call_t *call;
433
 
434
    udebug_int_lock();
435
 
436
    mutex_lock(&TASK->udebug.lock);
437
    mutex_lock(&THREAD->udebug.lock);
438
 
3441 svoboda 439
    LOG("udebug_thread_e_event\n");
440
    LOG("- check state\n");
3438 svoboda 441
 
442
    /* Must only generate events when in debugging session */
443
    if (THREAD->udebug.debug_active != true) {
444
/*      printf("- debug_active: %s, udebug.stop: %s\n",
445
            THREAD->udebug.debug_active ? "yes(+)" : "no(-)",
446
            THREAD->udebug.stop ? "yes(-)" : "no(+)");*/
447
        mutex_unlock(&THREAD->udebug.lock);
448
        mutex_unlock(&TASK->udebug.lock);
449
        return;
450
    }
451
 
3441 svoboda 452
    LOG("- trigger event\n");
3438 svoboda 453
 
454
    call = THREAD->udebug.go_call;
455
    THREAD->udebug.go_call = NULL;
456
    IPC_SET_RETVAL(call->data, 0);
457
    IPC_SET_ARG1(call->data, UDEBUG_EVENT_THREAD_E);
458
 
459
    /* Prevent any further debug activity in thread */
460
    THREAD->udebug.debug_active = false;
461
    THREAD->udebug.cur_event = 0;       /* none */
462
    THREAD->udebug.stop = true; /* set to initial value */
463
 
464
    ipc_answer(&TASK->answerbox, call);
465
 
466
    mutex_unlock(&THREAD->udebug.lock);
467
    mutex_unlock(&TASK->udebug.lock);
468
 
469
    /* Leave int_lock enabled */
470
    /* This event does not sleep - debugging has finished in this thread */
471
}
472
 
473
/**
474
 * Terminate task debugging session.
475
 *
3474 svoboda 476
 * Gracefully terminates the debugging session for a task. If the debugger
477
 * is still waiting for events on some threads, it will receive a
478
 * FINISHED event for each of them.
479
 *
480
 * @param ta    Task structure. ta->udebug.lock must be already locked.
481
 * @return  Zero on success or negative error code.
3438 svoboda 482
 */
483
int udebug_task_cleanup(struct task *ta)
484
{
485
    thread_t *t;
486
    link_t *cur;
487
    int flags;
488
    ipl_t ipl;
489
 
3441 svoboda 490
    LOG("udebug_task_cleanup()\n");
491
    LOG("task %" PRIu64 "\n", ta->taskid);
3438 svoboda 492
 
493
    udebug_int_lock();
494
 
495
    if (ta->udebug.dt_state != UDEBUG_TS_BEGINNING &&
496
        ta->udebug.dt_state != UDEBUG_TS_ACTIVE) {
3441 svoboda 497
        LOG("udebug_task_cleanup(): task not being debugged\n");
3438 svoboda 498
        return EINVAL;
499
    }
500
 
501
    /* Finish debugging of all userspace threads */
502
    for (cur = ta->th_head.next; cur != &ta->th_head; cur = cur->next) {
503
        t = list_get_instance(cur, thread_t, th_link);
504
 
505
        mutex_lock(&t->udebug.lock);
506
 
507
        ipl = interrupts_disable();
508
        spinlock_lock(&t->lock);
509
 
510
        flags = t->flags;
511
 
512
        spinlock_unlock(&t->lock);
513
        interrupts_restore(ipl);
514
 
515
        /* Only process userspace threads */
516
        if ((flags & THREAD_FLAG_USPACE) != 0) {
517
            /* Prevent any further debug activity in thread */
518
            t->udebug.debug_active = false;
519
            t->udebug.cur_event = 0;    /* none */
520
 
521
            /* Still has go? */
522
            if (t->udebug.stop == false) {
523
                /*
524
                * Yes, so clear go. As debug_active == false,
525
                 * this doesn't affect anything.
526
                 */
527
                t->udebug.stop = true; 
528
 
529
                /* Answer GO call */
3441 svoboda 530
                LOG("answer GO call with EVENT_FINISHED\n");
3438 svoboda 531
                IPC_SET_RETVAL(t->udebug.go_call->data, 0);
3474 svoboda 532
                IPC_SET_ARG1(t->udebug.go_call->data,
533
                    UDEBUG_EVENT_FINISHED);
3438 svoboda 534
 
535
                ipc_answer(&ta->answerbox, t->udebug.go_call);
536
                t->udebug.go_call = NULL;
537
            } else {
538
                /*
539
                 * Debug_stop is already at initial value.
540
                 * Yet this means the thread needs waking up.
541
                 */
542
 
543
                /*
544
                 * t's lock must not be held when calling
545
                 * waitq_wakeup.
546
                 */
547
                waitq_wakeup(&t->udebug.go_wq, WAKEUP_FIRST);
548
            }
549
        }
550
        mutex_unlock(&t->udebug.lock);
551
    }
552
 
553
    ta->udebug.dt_state = UDEBUG_TS_INACTIVE;
554
    ta->udebug.debugger = NULL;
555
 
556
    udebug_int_unlock();
557
 
558
    return 0;
559
}
560
 
561
 
562
/** @}
563
 */