aboutsummaryrefslogtreecommitdiffstats
path: root/extras/mini-os/xenbus/xenbus.c
blob: ee1691b85815cddfac758a686d70a6ea1b50b370 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
/* 
 ****************************************************************************
 * (C) 2006 - Cambridge University
 ****************************************************************************
 *
 *        File: xenbus.c
 *      Author: Steven Smith (sos22@cam.ac.uk) 
 *     Changes: Grzegorz Milos (gm281@cam.ac.uk)
 *     Changes: John D. Ramsdell
 *              
 *        Date: Jun 2006, chages Aug 2005
 * 
 * Environment: Xen Minimal OS
 * Description: Minimal implementation of xenbus
 *
 ****************************************************************************
 **/
#include <mini-os/os.h>
#include <mini-os/mm.h>
#include <mini-os/traps.h>
#include <mini-os/lib.h>
#include <mini-os/xenbus.h>
#include <mini-os/events.h>
#include <mini-os/errno.h>
#include <mini-os/sched.h>
#include <mini-os/wait.h>
#include <xen/io/xs_wire.h>
#include <mini-os/spinlock.h>
#include <mini-os/xmalloc.h>

#define min(x,y) ({                       \
        typeof(x) tmpx = (x);                 \
        typeof(y) tmpy = (y);                 \
        tmpx < tmpy ? tmpx : tmpy;            \
        })

#ifdef XENBUS_DEBUG
#define DEBUG(_f, _a...) \
    printk("MINI_OS(file=xenbus.c, line=%d) " _f , __LINE__, ## _a)
#else
#define DEBUG(_f, _a...)    ((void)0)
#endif

static struct xenstore_domain_interface *xenstore_buf;
static DECLARE_WAIT_QUEUE_HEAD(xb_waitq);
DECLARE_WAIT_QUEUE_HEAD(xenbus_watch_queue);

xenbus_event_queue xenbus_events;
static struct watch {
    char *token;
    xenbus_event_queue *events;
    struct watch *next;
} *watches;
struct xenbus_req_info 
{
    int in_use:1;
    struct wait_queue_head waitq;
    void *reply;
};

#define NR_REQS 32
static struct xenbus_req_info req_info[NR_REQS];

static void memcpy_from_ring(const void *Ring,
        void *Dest,
        int off,
        int len)
{
    int c1, c2;
    const char *ring = Ring;
    char *dest = Dest;
    c1 = min(len, XENSTORE_RING_SIZE - off);
    c2 = len - c1;
    memcpy(dest, ring + off, c1);
    memcpy(dest + c1, ring, c2);
}

char **xenbus_wait_for_watch_return(xenbus_event_queue *queue)
{
    struct xenbus_event *event;
    DEFINE_WAIT(w);
    if (!queue)
        queue = &xenbus_events;
    while (!(event = *queue)) {
        add_waiter(w, xenbus_watch_queue);
        schedule();
    }
    remove_waiter(w, xenbus_watch_queue);
    *queue = event->next;
    return &event->path;
}

void xenbus_wait_for_watch(xenbus_event_queue *queue)
{
    char **ret;
    if (!queue)
        queue = &xenbus_events;
    ret = xenbus_wait_for_watch_return(queue);
    if (ret)
        free(ret);
    else
        printk("unexpected path returned by watch\n");
}

char* xenbus_wait_for_value(const char* path, const char* value, xenbus_event_queue *queue)
{
    if (!queue)
        queue = &xenbus_events;
    for(;;)
    {
        char *res, *msg;
        int r;

        msg = xenbus_read(XBT_NIL, path, &res);
        if(msg) return msg;

        r = strcmp(value,res);
        free(res);

        if(r==0) break;
        else xenbus_wait_for_watch(queue);
    }
    return NULL;
}

char *xenbus_switch_state(xenbus_transaction_t xbt, const char* path, XenbusState state)
{
    char *current_state;
    char *msg = NULL;
    char *msg2 = NULL;
    char value[2];
    XenbusState rs;
    int xbt_flag = 0;
    int retry = 0;

    do {
        if (xbt == XBT_NIL) {
            msg = xenbus_transaction_start(&xbt);
            if (msg) goto exit;
            xbt_flag = 1;
        }

        msg = xenbus_read(xbt, path, &current_state);
        if (msg) goto exit;

        rs = (XenbusState) (current_state[0] - '0');
        free(current_state);
        if (rs == state) {
            msg = NULL;
            goto exit;
        }

        snprintf(value, 2, "%d", state);
        msg = xenbus_write(xbt, path, value);

exit:
        if (xbt_flag) {
            msg2 = xenbus_transaction_end(xbt, 0, &retry);
            xbt = XBT_NIL;
        }
        if (msg == NULL && msg2 != NULL)
            msg = msg2;
    } while (retry);

    return msg;
}

char *xenbus_wait_for_state_change(const char* path, XenbusState *state, xenbus_event_queue *queue)
{
    if (!queue)
        queue = &xenbus_events;
    for(;;)
    {
        char *res, *msg;
        XenbusState rs;

        msg = xenbus_read(XBT_NIL, path, &res);
        if(msg) return msg;

        rs = (XenbusState) (res[0] - 48);
        free(res);

        if (rs == *state)
            xenbus_wait_for_watch(queue);
        else {
            *state = rs;
            break;
        }
    }
    return NULL;
}


static void xenbus_thread_func(void *ign)
{
    struct xsd_sockmsg msg;
    unsigned prod = xenstore_buf->rsp_prod;

    for (;;) 
    {
        wait_event(xb_waitq, prod != xenstore_buf->rsp_prod);
        while (1) 
        {
            prod = xenstore_buf->rsp_prod;
            DEBUG("Rsp_cons %d, rsp_prod %d.\n", xenstore_buf->rsp_cons,
                    xenstore_buf->rsp_prod);
            if (xenstore_buf->rsp_prod - xenstore_buf->rsp_cons < sizeof(msg))
                break;
            rmb();
            memcpy_from_ring(xenstore_buf->rsp,
                    &msg,
                    MASK_XENSTORE_IDX(xenstore_buf->rsp_cons),
                    sizeof(msg));
            DEBUG("Msg len %d, %d avail, id %d.\n",
                    msg.len + sizeof(msg),
                    xenstore_buf->rsp_prod - xenstore_buf->rsp_cons,
                    msg.req_id);
            if (xenstore_buf->rsp_prod - xenstore_buf->rsp_cons <
                    sizeof(msg) + msg.len)
                break;

            DEBUG("Message is good.\n");

            if(msg.type == XS_WATCH_EVENT)
            {
		struct xenbus_event *event = malloc(sizeof(*event) + msg.len);
                xenbus_event_queue *events = NULL;
		char *data = (char*)event + sizeof(*event);
                struct watch *watch;

                memcpy_from_ring(xenstore_buf->rsp,
		    data,
                    MASK_XENSTORE_IDX(xenstore_buf->rsp_cons + sizeof(msg)),
                    msg.len);

		event->path = data;
		event->token = event->path + strlen(event->path) + 1;

                xenstore_buf->rsp_cons += msg.len + sizeof(msg);

                for (watch = watches; watch; watch = watch->next)
                    if (!strcmp(watch->token, event->token)) {
                        events = watch->events;
                        break;
                    }

                if (events) {
                    event->next = *events;
                    *events = event;
                    wake_up(&xenbus_watch_queue);
                } else {
                    printk("unexpected watch token %s\n", event->token);
                    free(event);
                }
            }

            else
            {
                req_info[msg.req_id].reply = malloc(sizeof(msg) + msg.len);
                memcpy_from_ring(xenstore_buf->rsp,
                    req_info[msg.req_id].reply,
                    MASK_XENSTORE_IDX(xenstore_buf->rsp_cons),
                    msg.len + sizeof(msg));
                xenstore_buf->rsp_cons += msg.len + sizeof(msg);
                wake_up(&req_info[msg.req_id].waitq);
            }
        }
    }
}

static void xenbus_evtchn_handler(evtchn_port_t port, struct pt_regs *regs,
				  void *ign)
{
    wake_up(&xb_waitq);
}

static int nr_live_reqs;
static spinlock_t req_lock = SPIN_LOCK_UNLOCKED;
static DECLARE_WAIT_QUEUE_HEAD(req_wq);

/* Release a xenbus identifier */
static void release_xenbus_id(int id)
{
    BUG_ON(!req_info[id].in_use);
    spin_lock(&req_lock);
    req_info[id].in_use = 0;
    nr_live_reqs--;
    req_info[id].in_use = 0;
    if (nr_live_reqs == NR_REQS - 1)
        wake_up(&req_wq);
    spin_unlock(&req_lock);
}

/* Allocate an identifier for a xenbus request.  Blocks if none are
   available. */
static int allocate_xenbus_id(void)
{
    static int probe;
    int o_probe;

    while (1) 
    {
        spin_lock(&req_lock);
        if (nr_live_reqs < NR_REQS)
            break;
        spin_unlock(&req_lock);
        wait_event(req_wq, (nr_live_reqs < NR_REQS));
    }

    o_probe = probe;
    for (;;) 
    {
        if (!req_info[o_probe].in_use)
            break;
        o_probe = (o_probe + 1) % NR_REQS;
        BUG_ON(o_probe == probe);
    }
    nr_live_reqs++;
    req_info[o_probe].in_use = 1;
    probe = (o_probe + 1) % NR_REQS;
    spin_unlock(&req_lock);
    init_waitqueue_head(&req_info[o_probe].waitq);

    return o_probe;
}

/* Initialise xenbus. */
void init_xenbus(void)
{
    int err;
    DEBUG("init_xenbus called.\n");
    xenstore_buf = mfn_to_virt(start_info.store_mfn);
    create_thread("xenstore", xenbus_thread_func, NULL);
    DEBUG("buf at %p.\n", xenstore_buf);
    err = bind_evtchn(start_info.store_evtchn,
		      xenbus_evtchn_handler,
              NULL);
    unmask_evtchn(start_info.store_evtchn);
    printk("xenbus initialised on irq %d mfn %#lx\n",
	   err, start_info.store_mfn);
}

void fini_xenbus(void)
{
}

/* Send data to xenbus.  This can block.  All of the requests are seen
   by xenbus as if sent atomically.  The header is added
   automatically, using type %type, req_id %req_id, and trans_id
   %trans_id. */
static void xb_write(int type, int req_id, xenbus_transaction_t trans_id,
		     const struct write_req *req, int nr_reqs)
{
    XENSTORE_RING_IDX prod;
    int r;
    int len = 0;
    const struct write_req *cur_req;
    int req_off;
    int total_off;
    int this_chunk;
    struct xsd_sockmsg m = {.type = type, .req_id = req_id,
        .tx_id = trans_id };
    struct write_req header_req = { &m, sizeof(m) };

    for (r = 0; r < nr_reqs; r++)
        len += req[r].len;
    m.len = len;
    len += sizeof(m);

    cur_req = &header_req;

    BUG_ON(len > XENSTORE_RING_SIZE);
    /* Wait for the ring to drain to the point where we can send the
       message. */
    prod = xenstore_buf->req_prod;
    if (prod + len - xenstore_buf->req_cons > XENSTORE_RING_SIZE) 
    {
        /* Wait for there to be space on the ring */
        DEBUG("prod %d, len %d, cons %d, size %d; waiting.\n",
                prod, len, xenstore_buf->req_cons, XENSTORE_RING_SIZE);
        wait_event(xb_waitq,
                xenstore_buf->req_prod + len - xenstore_buf->req_cons <=
                XENSTORE_RING_SIZE);
        DEBUG("Back from wait.\n");
        prod = xenstore_buf->req_prod;
    }

    /* We're now guaranteed to be able to send the message without
       overflowing the ring.  Do so. */
    total_off = 0;
    req_off = 0;
    while (total_off < len) 
    {
        this_chunk = min(cur_req->len - req_off,
                XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(prod));
        memcpy((char *)xenstore_buf->req + MASK_XENSTORE_IDX(prod),
                (char *)cur_req->data + req_off, this_chunk);
        prod += this_chunk;
        req_off += this_chunk;
        total_off += this_chunk;
        if (req_off == cur_req->len) 
        {
            req_off = 0;
            if (cur_req == &header_req)
                cur_req = req;
            else
                cur_req++;
        }
    }

    DEBUG("Complete main loop of xb_write.\n");
    BUG_ON(req_off != 0);
    BUG_ON(total_off != len);
    BUG_ON(prod > xenstore_buf->req_cons + XENSTORE_RING_SIZE);

    /* Remote must see entire message before updating indexes */
    wmb();

    xenstore_buf->req_prod += len;

    /* Send evtchn to notify remote */
    notify_remote_via_evtchn(start_info.store_evtchn);
}

/* Send a mesasge to xenbus, in the same fashion as xb_write, and
   block waiting for a reply.  The reply is malloced and should be
   freed by the caller. */
struct xsd_sockmsg *
xenbus_msg_reply(int type,
		 xenbus_transaction_t trans,
		 struct write_req *io,
		 int nr_reqs)
{
    int id;
    DEFINE_WAIT(w);
    struct xsd_sockmsg *rep;

    id = allocate_xenbus_id();
    add_waiter(w, req_info[id].waitq);

    xb_write(type, id, trans, io, nr_reqs);

    schedule();
    remove_waiter(w, req_info[id].waitq);
    wake(current);

    rep = req_info[id].reply;
    BUG_ON(rep->req_id != id);
    release_xenbus_id(id);
    return rep;
}

static char *errmsg(struct xsd_sockmsg *rep)
{
    char *res;
    if (!rep) {
	char msg[] = "No reply";
	size_t len = strlen(msg) + 1;
	return memcpy(malloc(len), msg, len);
    }
    if (rep->type != XS_ERROR)
	return NULL;
    res = malloc(rep->len + 1);
    memcpy(res, rep + 1, rep->len);
    res[rep->len] = 0;
    free(rep);
    return res;
}	

/* Send a debug message to xenbus.  Can block. */
static void xenbus_debug_msg(const char *msg)
{
    int len = strlen(msg);
    struct write_req req[] = {
        { "print", sizeof("print") },
        { msg, len },
        { "", 1 }};
    struct xsd_sockmsg *reply;

    reply = xenbus_msg_reply(XS_DEBUG, 0, req, ARRAY_SIZE(req));
    printk("Got a reply, type %d, id %d, len %d.\n",
            reply->type, reply->req_id, reply->len);
}

/* List the contents of a directory.  Returns a malloc()ed array of
   pointers to malloc()ed strings.  The array is NULL terminated.  May
   block. */
char *xenbus_ls(xenbus_transaction_t xbt, const char *pre, char ***contents)
{
    struct xsd_sockmsg *reply, *repmsg;
    struct write_req req[] = { { pre, strlen(pre)+1 } };
    int nr_elems, x, i;
    char **res, *msg;

    repmsg = xenbus_msg_reply(XS_DIRECTORY, xbt, req, ARRAY_SIZE(req));
    msg = errmsg(repmsg);
    if (msg) {
	*contents = NULL;
	return msg;
    }
    reply = repmsg + 1;
    for (x = nr_elems = 0; x < repmsg->len; x++)
        nr_elems += (((char *)reply)[x] == 0);
    res = malloc(sizeof(res[0]) * (nr_elems + 1));
    for (x = i = 0; i < nr_elems; i++) {
        int l = strlen((char *)reply + x);
        res[i] = malloc(l + 1);
        memcpy(res[i], (char *)reply + x, l + 1);
        x += l + 1;
    }
    res[i] = NULL;
    free(repmsg);
    *contents = res;
    return NULL;
}

char *xenbus_read(xenbus_transaction_t xbt, const char *path, char **value)
{
    struct write_req req[] = { {path, strlen(path) + 1} };
    struct xsd_sockmsg *rep;
    char *res, *msg;
    rep = xenbus_msg_reply(XS_READ, xbt, req, ARRAY_SIZE(req));
    msg = errmsg(rep);
    if (msg) {
	*value = NULL;
	return msg;
    }
    res = malloc(rep->len + 1);
    memcpy(res, rep + 1, rep->len);
    res[rep->len] = 0;
    free(rep);
    *value = res;
    return NULL;
}

char *xenbus_write(xenbus_transaction_t xbt, const char *path, const char *value)
{
    struct write_req req[] = { 
	{path, strlen(path) + 1},
	{value, strlen(value)},
    };
    struct xsd_sockmsg *rep;
    char *msg;
    rep = xenbus_msg_reply(XS_WRITE, xbt, req, ARRAY_SIZE(req));
    msg = errmsg(rep);
    if (msg) return msg;
    free(rep);
    return NULL;
}

char* xenbus_watch_path_token( xenbus_transaction_t xbt, const char *path, const char *token, xenbus_event_queue *events)
{
    struct xsd_sockmsg *rep;

    struct write_req req[] = { 
        {path, strlen(path) + 1},
	{token, strlen(token) + 1},
    };

    struct watch *watch = malloc(sizeof(*watch));

    char *msg;

    if (!events)
        events = &xenbus_events;

    watch->token = strdup(token);
    watch->events = events;
    watch->next = watches;
    watches = watch;

    rep = xenbus_msg_reply(XS_WATCH, xbt, req, ARRAY_SIZE(req));

    msg = errmsg(rep);
    if (msg) return msg;
    free(rep);

    return NULL;
}

char* xenbus_unwatch_path_token( xenbus_transaction_t xbt, const char *path, const char *token)
{
    struct xsd_sockmsg *rep;

    struct write_req req[] = { 
        {path, strlen(path) + 1},
	{token, strlen(token) + 1},
    };

    struct watch *watch, **prev;

    char *msg;

    rep = xenbus_msg_reply(XS_UNWATCH, xbt, req, ARRAY_SIZE(req));

    msg = errmsg(rep);
    if (msg) return msg;
    free(rep);

    for (prev = &watches, watch = *prev; watch; prev = &watch->next, watch = *prev)
        if (!strcmp(watch->token, token)) {
            free(watch->token);
            *prev = watch->next;
            free(watch);
            break;
        }

    return NULL;
}

char *xenbus_rm(xenbus_transaction_t xbt, const char *path)
{
    struct write_req req[] = { {path, strlen(path) + 1} };
    struct xsd_sockmsg *rep;
    char *msg;
    rep = xenbus_msg_reply(XS_RM, xbt, req, ARRAY_SIZE(req));
    msg = errmsg(rep);
    if (msg)
	return msg;
    free(rep);
    return NULL;
}

char *xenbus_get_perms(xenbus_transaction_t xbt, const char *path, char **value)
{
    struct write_req req[] = { {path, strlen(path) + 1} };
    struct xsd_sockmsg *rep;
    char *res, *msg;
    rep = xenbus_msg_reply(XS_GET_PERMS, xbt, req, ARRAY_SIZE(req));
    msg = errmsg(rep);
    if (msg) {
	*value = NULL;
	return msg;
    }
    res = malloc(rep->len + 1);
    memcpy(res, rep + 1, rep->len);
    res[rep->len] = 0;
    free(rep);
    *value = res;
    return NULL;
}

#define PERM_MAX_SIZE 32
char *xenbus_set_perms(xenbus_transaction_t xbt, const char *path, domid_t dom, char perm)
{
    char value[PERM_MAX_SIZE];
    struct write_req req[] = { 
	{path, strlen(path) + 1},
	{value, 0},
    };
    struct xsd_sockmsg *rep;
    char *msg;
    snprintf(value, PERM_MAX_SIZE, "%c%hu", perm, dom);
    req[1].len = strlen(value) + 1;
    rep = xenbus_msg_reply(XS_SET_PERMS, xbt, req, ARRAY_SIZE(req));
    msg = errmsg(rep);
    if (msg)
	return msg;
    free(rep);
    return NULL;
}

char *xenbus_transaction_start(xenbus_transaction_t *xbt)
{
    /* xenstored becomes angry if you send a length 0 message, so just
       shove a nul terminator on the end */
    struct write_req req = { "", 1};
    struct xsd_sockmsg *rep;
    char *err;

    rep = xenbus_msg_reply(XS_TRANSACTION_START, 0, &req, 1);
    err = errmsg(rep);
    if (err)
	return err;
    sscanf((char *)(rep + 1), "%u", xbt);
    free(rep);
    return NULL;
}

char *
xenbus_transaction_end(xenbus_transaction_t t, int abort, int *retry)
{
    struct xsd_sockmsg *rep;
    struct write_req req;
    char *err;

    *retry = 0;

    req.data = abort ? "F" : "T";
    req.len = 2;
    rep = xenbus_msg_reply(XS_TRANSACTION_END, t, &req, 1);
    err = errmsg(rep);
    if (err) {
	if (!strcmp(err, "EAGAIN")) {
	    *retry = 1;
	    free(err);
	    return NULL;
	} else {
	    return err;
	}
    }
    free(rep);
    return NULL;
}

int xenbus_read_integer(const char *path)
{
    char *res, *buf;
    int t;

    res = xenbus_read(XBT_NIL, path, &buf);
    if (res) {
	printk("Failed to read %s.\n", path);
	free(res);
	return -1;
    }
    sscanf(buf, "%d", &t);
    free(buf);
    return t;
}

int xenbus_read_uuid(const char* path, unsigned char uuid[16]) {
   char * res, *buf;
   res = xenbus_read(XBT_NIL, path, &buf);
   if(res) {
      printk("Failed to read %s.\n", path);
      free(res);
      return 0;
   }
   if(strlen(buf) != ((2*16)+4) /* 16 hex bytes and 4 hyphens */
         || sscanf(buf,
            "%2hhx%2hhx%2hhx%2hhx-"
            "%2hhx%2hhx-"
            "%2hhx%2hhx-"
            "%2hhx%2hhx-"
            "%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx",
            uuid, uuid + 1, uuid + 2, uuid + 3,
            uuid + 4, uuid + 5, uuid + 6, uuid + 7,
            uuid + 8, uuid + 9, uuid + 10, uuid + 11,
            uuid + 12, uuid + 13, uuid + 14, uuid + 15) != 16) {
      printk("Xenbus path %s value %s is not a uuid!\n", path, buf);
      free(buf);
      return 0;
   }
   free(buf);
   return 1;
}

char* xenbus_printf(xenbus_transaction_t xbt,
                                  const char* node, const char* path,
                                  const char* fmt, ...)
{
#define BUFFER_SIZE 256
    char fullpath[BUFFER_SIZE];
    char val[BUFFER_SIZE];
    va_list args;

    BUG_ON(strlen(node) + strlen(path) + 1 >= BUFFER_SIZE);
    sprintf(fullpath,"%s/%s", node, path);
    va_start(args, fmt);
    vsprintf(val, fmt, args);
    va_end(args);
    return xenbus_write(xbt,fullpath,val);
}

domid_t xenbus_get_self_id(void)
{
    char *dom_id;
    domid_t ret;

    BUG_ON(xenbus_read(XBT_NIL, "domid", &dom_id));
    sscanf(dom_id, "%d", &ret);

    return ret;
}

static void do_ls_test(const char *pre)
{
    char **dirs, *msg;
    int x;

    printk("ls %s...\n", pre);
    msg = xenbus_ls(XBT_NIL, pre, &dirs);
    if (msg) {
	printk("Error in xenbus ls: %s\n", msg);
	free(msg);
	return;
    }
    for (x = 0; dirs[x]; x++) 
    {
        printk("ls %s[%d] -> %s\n", pre, x, dirs[x]);
        free(dirs[x]);
    }
    free(dirs);
}

static void do_read_test(const char *path)
{
    char *res, *msg;
    printk("Read %s...\n", path);
    msg = xenbus_read(XBT_NIL, path, &res);
    if (msg) {
	printk("Error in xenbus read: %s\n", msg);
	free(msg);
	return;
    }
    printk("Read %s -> %s.\n", path, res);
    free(res);
}

static void do_write_test(const char *path, const char *val)
{
    char *msg;
    printk("Write %s to %s...\n", val, path);
    msg = xenbus_write(XBT_NIL, path, val);
    if (msg) {
	printk("Result %s\n", msg);
	free(msg);
    } else {
	printk("Success.\n");
    }
}

static void do_rm_test(const char *path)
{
    char *msg;
    printk("rm %s...\n", path);
    msg = xenbus_rm(XBT_NIL, path);
    if (msg) {
	printk("Result %s\n", msg);
	free(msg);
    } else {
	printk("Success.\n");
    }
}

/* Simple testing thing */
void test_xenbus(void)
{
    printk("Doing xenbus test.\n");
    xenbus_debug_msg("Testing xenbus...\n");

    printk("Doing ls test.\n");
    do_ls_test("device");
    do_ls_test("device/vif");
    do_ls_test("device/vif/0");

    printk("Doing read test.\n");
    do_read_test("device/vif/0/mac");
    do_read_test("device/vif/0/backend");

    printk("Doing write test.\n");
    do_write_test("device/vif/0/flibble", "flobble");
    do_read_test("device/vif/0/flibble");
    do_write_test("device/vif/0/flibble", "widget");
    do_read_test("device/vif/0/flibble");

    printk("Doing rm test.\n");
    do_rm_test("device/vif/0/flibble");
    do_read_test("device/vif/0/flibble");
    printk("(Should have said ENOENT)\n");
}

/*
 * Local variables:
 * mode: C
 * c-basic-offset: 4
 * End:
 */