summaryrefslogtreecommitdiffstats
path: root/sys/geom/geom_bsd.c
blob: 7d51896958a30f6cacedef86999385590b66d86f (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
/*-
 * Copyright (c) 2002 Poul-Henning Kamp
 * Copyright (c) 2002 Networks Associates Technology, Inc.
 * All rights reserved.
 *
 * This software was developed for the FreeBSD Project by Poul-Henning Kamp
 * and NAI Labs, the Security Research Division of Network Associates, Inc.
 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
 * DARPA CHATS research program.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The names of the authors may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD$
 *
 * This is the method for dealing with BSD disklabels.  It has been
 * extensively (by my standards at least) commented, in the vain hope that
 * it will server as the source in future copy&paste operations.
 */

#include <sys/param.h>
#ifndef _KERNEL
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <signal.h>
#include <err.h>
#else
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/bio.h>
#include <sys/malloc.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#endif
#include <sys/stdint.h>
#include <sys/errno.h>
#include <sys/disklabel.h>
#include <geom/geom.h>
#include <geom/geom_slice.h>

#define	BSD_CLASS_NAME "BSD"

#define ALPHA_LABEL_OFFSET	64

/*
 * Our private data about one instance.  All the rest is handled by the
 * slice code and stored in its softc, so this is just the stuff
 * specific to BSD disklabels.
 */
struct g_bsd_softc {
	off_t	labeloffset;
	off_t	mbroffset;
	off_t	rawoffset;
	struct disklabel ondisk;
	struct disklabel inram;
};

/*
 * The next 4 functions isolate us from how the compiler lays out and pads
 * "struct disklabel".  We treat what we read from disk as a bytestream and
 * explicitly convert it into a struct disklabel.  This makes us compiler-
 * endianness- and wordsize- agnostic.
 * For now we only have little-endian formats to deal with.
 */

static void
g_bsd_ledec_partition(u_char *ptr, struct partition *d)
{
	d->p_size = g_dec_le4(ptr + 0);
	d->p_offset = g_dec_le4(ptr + 4);
	d->p_fsize = g_dec_le4(ptr + 8);
	d->p_fstype = ptr[12];
	d->p_frag = ptr[13];
	d->p_cpg = g_dec_le2(ptr + 14);
}

static void
g_bsd_ledec_disklabel(u_char *ptr, struct disklabel *d)
{
	int i;

	d->d_magic = g_dec_le4(ptr + 0);
	d->d_type = g_dec_le2(ptr + 4);
	d->d_subtype = g_dec_le2(ptr + 6);
	bcopy(ptr + 8, d->d_typename, 16);
	bcopy(ptr + 24, d->d_packname, 16);
	d->d_secsize = g_dec_le4(ptr + 40);
	d->d_nsectors = g_dec_le4(ptr + 44);
	d->d_ntracks = g_dec_le4(ptr + 48);
	d->d_ncylinders = g_dec_le4(ptr + 52);
	d->d_secpercyl = g_dec_le4(ptr + 56);
	d->d_secperunit = g_dec_le4(ptr + 60);
	d->d_sparespertrack = g_dec_le2(ptr + 64);
	d->d_sparespercyl = g_dec_le2(ptr + 66);
	d->d_acylinders = g_dec_le4(ptr + 68);
	d->d_rpm = g_dec_le2(ptr + 72);
	d->d_interleave = g_dec_le2(ptr + 74);
	d->d_trackskew = g_dec_le2(ptr + 76);
	d->d_cylskew = g_dec_le2(ptr + 78);
	d->d_headswitch = g_dec_le4(ptr + 80);
	d->d_trkseek = g_dec_le4(ptr + 84);
	d->d_flags = g_dec_le4(ptr + 88);
	d->d_drivedata[0] = g_dec_le4(ptr + 92);
	d->d_drivedata[1] = g_dec_le4(ptr + 96);
	d->d_drivedata[2] = g_dec_le4(ptr + 100);
	d->d_drivedata[3] = g_dec_le4(ptr + 104);
	d->d_drivedata[4] = g_dec_le4(ptr + 108);
	d->d_spare[0] = g_dec_le4(ptr + 112);
	d->d_spare[1] = g_dec_le4(ptr + 116);
	d->d_spare[2] = g_dec_le4(ptr + 120);
	d->d_spare[3] = g_dec_le4(ptr + 124);
	d->d_spare[4] = g_dec_le4(ptr + 128);
	d->d_magic2 = g_dec_le4(ptr + 132);
	d->d_checksum = g_dec_le2(ptr + 136);
	d->d_npartitions = g_dec_le2(ptr + 138);
	d->d_bbsize = g_dec_le4(ptr + 140);
	d->d_sbsize = g_dec_le4(ptr + 144);
	for (i = 0; i < MAXPARTITIONS; i++)
		g_bsd_ledec_partition(ptr + 148 + 16 * i, &d->d_partitions[i]);
}

static void
g_bsd_leenc_partition(u_char *ptr, struct partition *d)
{
	g_enc_le4(ptr + 0, d->p_size);
	g_enc_le4(ptr + 4, d->p_offset);
	g_enc_le4(ptr + 8, d->p_fsize);
	ptr[12] = d->p_fstype;
	ptr[13] = d->p_frag;
	g_enc_le2(ptr + 14, d->p_cpg);
}

static void
g_bsd_leenc_disklabel(u_char *ptr, struct disklabel *d)
{
	int i;

	g_enc_le4(ptr + 0, d->d_magic);
	g_enc_le2(ptr + 4, d->d_type);
	g_enc_le2(ptr + 6, d->d_subtype);
	bcopy(d->d_typename, ptr + 8, 16);
	bcopy(d->d_packname, ptr + 24, 16);
	g_enc_le4(ptr + 40, d->d_secsize);
	g_enc_le4(ptr + 44, d->d_nsectors);
	g_enc_le4(ptr + 48, d->d_ntracks);
	g_enc_le4(ptr + 52, d->d_ncylinders);
	g_enc_le4(ptr + 56, d->d_secpercyl);
	g_enc_le4(ptr + 60, d->d_secperunit);
	g_enc_le2(ptr + 64, d->d_sparespertrack);
	g_enc_le2(ptr + 66, d->d_sparespercyl);
	g_enc_le4(ptr + 68, d->d_acylinders);
	g_enc_le2(ptr + 72, d->d_rpm);
	g_enc_le2(ptr + 74, d->d_interleave);
	g_enc_le2(ptr + 76, d->d_trackskew);
	g_enc_le2(ptr + 78, d->d_cylskew);
	g_enc_le4(ptr + 80, d->d_headswitch);
	g_enc_le4(ptr + 84, d->d_trkseek);
	g_enc_le4(ptr + 88, d->d_flags);
	g_enc_le4(ptr + 92, d->d_drivedata[0]);
	g_enc_le4(ptr + 96, d->d_drivedata[1]);
	g_enc_le4(ptr + 100, d->d_drivedata[2]);
	g_enc_le4(ptr + 104, d->d_drivedata[3]);
	g_enc_le4(ptr + 108, d->d_drivedata[4]);
	g_enc_le4(ptr + 112, d->d_spare[0]);
	g_enc_le4(ptr + 116, d->d_spare[1]);
	g_enc_le4(ptr + 120, d->d_spare[2]);
	g_enc_le4(ptr + 124, d->d_spare[3]);
	g_enc_le4(ptr + 128, d->d_spare[4]);
	g_enc_le4(ptr + 132, d->d_magic2);
	g_enc_le2(ptr + 136, d->d_checksum);
	g_enc_le2(ptr + 138, d->d_npartitions);
	g_enc_le4(ptr + 140, d->d_bbsize);
	g_enc_le4(ptr + 144, d->d_sbsize);
	for (i = 0; i < MAXPARTITIONS; i++)
		g_bsd_leenc_partition(ptr + 148 + 16 * i, &d->d_partitions[i]);
}

static int
g_bsd_ondisk_size(void)
{
	return (148 + 16 * MAXPARTITIONS);
}

/*
 * For reasons which were valid and just in their days, FreeBSD/i386 uses
 * absolute disk-addresses in disklabels.  The way it works is that the
 * p_offset field of all partitions have the first sector number of the
 * disk slice added to them.  This was hidden kernel-magic, userland did
 * not see these offsets.  These two functions subtract and add them
 * while converting from the "ondisk" to the "inram" labels and vice
 * versa.
 */
static void
ondisk2inram(struct g_bsd_softc *sc)
{
	struct partition *ppp;
	struct disklabel *dl;
	int i;

	sc->inram = sc->ondisk;
	dl = &sc->inram;

	/* Basic sanity-check needed to avoid mistakes. */
	if (dl->d_magic != DISKMAGIC || dl->d_magic2 != DISKMAGIC)
		return;
	if (dl->d_npartitions > MAXPARTITIONS)
		return;

	sc->rawoffset = dl->d_partitions[RAW_PART].p_offset;
	for (i = 0; i < dl->d_npartitions; i++) {
		ppp = &dl->d_partitions[i];
		if (ppp->p_size != 0 && ppp->p_offset < sc->rawoffset)
			sc->rawoffset = 0;
	}
	if (sc->rawoffset > 0) {
		for (i = 0; i < dl->d_npartitions; i++) {
			ppp = &dl->d_partitions[i];
			if (ppp->p_offset != 0)
				ppp->p_offset -= sc->rawoffset;
		}
	}
	dl->d_checksum = 0;
	dl->d_checksum = dkcksum(&sc->inram);
}

static void
inram2ondisk(struct g_bsd_softc *sc)
{
	struct partition *ppp;
	int i;

	sc->ondisk = sc->inram;
	if (sc->mbroffset != 0)
		sc->rawoffset = sc->mbroffset / sc->inram.d_secsize; 
	if (sc->rawoffset != 0) {
		for (i = 0; i < sc->inram.d_npartitions; i++) {
			ppp = &sc->ondisk.d_partitions[i];
			if (ppp->p_size > 0) 
				ppp->p_offset += sc->rawoffset;
			else
				ppp->p_offset = 0;
		}
	}
	sc->ondisk.d_checksum = 0;
	sc->ondisk.d_checksum = dkcksum(&sc->ondisk);
}

/*
 * Check that this looks like a valid disklabel, but be prepared
 * to get any kind of junk.  The checksum must be checked only
 * after this function returns success to prevent a bogus d_npartitions
 * value from tripping us up.
 */
static int
g_bsd_checklabel(struct disklabel *dl)
{
	struct partition *ppp;
	int i;

	if (dl->d_magic != DISKMAGIC || dl->d_magic2 != DISKMAGIC)
		return (EINVAL);
	/*
	 * If the label specifies more partitions than we can handle
	 * we have to reject it:  If people updated the label they would
	 * trash it, and that would break the checksum.
	 */
	if (dl->d_npartitions > MAXPARTITIONS)
		return (EINVAL);

	for (i = 0; i < dl->d_npartitions; i++) {
		ppp = &dl->d_partitions[i];
		/* Cannot extend past unit. */
		if (ppp->p_size != 0 &&
		     ppp->p_offset + ppp->p_size > dl->d_secperunit) {
			return (EINVAL);
		}
	}
	return (0);
}

/*
 * Modify our slicer to match proposed disklabel, if possible.
 * First carry out all the simple checks, then lock topology
 * and check that no open providers are affected negatively
 * then carry out all the changes.
 *
 * NB: Returns with topology held only if successful return.
 */
static int
g_bsd_modify(struct g_geom *gp, struct disklabel *dl)
{
	int i, error;
	struct partition *ppp;
	struct g_slicer *gsp;
	struct g_consumer *cp;
	u_int secsize, u;
	off_t mediasize;

	/* Basic check that this is indeed a disklabel. */
	error = g_bsd_checklabel(dl);
	if (error)
		return (error);

	/* Make sure the checksum is OK. */
	if (dkcksum(dl) != 0)
		return (EINVAL);

	/* Get dimensions of our device. */
	cp = LIST_FIRST(&gp->consumer);
	secsize = cp->provider->sectorsize;
	mediasize = cp->provider->mediasize;

#ifdef nolonger
	/*
	 * The raw-partition must start at zero.  We do not check that the
	 * size == mediasize because this is overly restrictive.  We have
	 * already tested in g_bsd_checklabel() that it is not longer.
	 * XXX: RAW_PART is archaic anyway, and we should drop it.
	 */
	if (dl->d_partitions[RAW_PART].p_offset != 0)
		return (EINVAL);
#endif

#ifdef notyet
	/*
	 * Indications are that the d_secperunit is not correctly
	 * initialized in many cases, and since we don't need it
	 * for anything, we dont strictly need this test.
	 * Preemptive action to avoid confusing people in disklabel(8)
	 * may be in order.
	 */
	/* The label cannot claim a larger size than the media. */
	if ((off_t)dl->d_secperunit * dl->d_secsize > mediasize)
		return (EINVAL);
#endif


	/* ... or a smaller sector size. */
	if (dl->d_secsize < secsize)
		return (EINVAL);

	/* ... or a non-multiple sector size. */
	if (dl->d_secsize % secsize != 0)
		return (EINVAL);

	g_topology_lock();

	/* Don't munge open partitions. */
	gsp = gp->softc;
	for (i = 0; i < dl->d_npartitions; i++) {
		ppp = &dl->d_partitions[i];

		error = g_slice_config(gp, i, G_SLICE_CONFIG_CHECK,
		    (off_t)ppp->p_offset * dl->d_secsize,
		    (off_t)ppp->p_size * dl->d_secsize,
		     dl->d_secsize,
		    "%s%c", gp->name, 'a' + i);
		if (error) {
			g_topology_unlock();
			return (error);
		}
	}

	/* Look good, go for it... */
	for (u = 0; u < gsp->nslice; u++) {
		ppp = &dl->d_partitions[u];
		g_slice_config(gp, u, G_SLICE_CONFIG_SET,
		    (off_t)ppp->p_offset * dl->d_secsize,
		    (off_t)ppp->p_size * dl->d_secsize,
		     dl->d_secsize,
		    "%s%c", gp->name, 'a' + u);
	}
	return (0);
}

/*
 * Calculate a disklabel checksum for a little-endian byte-stream.
 * We need access to the decoded disklabel because the checksum only
 * covers the partition data for the first d_npartitions.
 */
static int
g_bsd_lesum(struct disklabel *dl, u_char *p)
{
	u_char *pe;
	uint16_t sum;

	pe = p + 148 + 16 * dl->d_npartitions;
	sum = 0;
	while (p < pe) {
		sum ^= g_dec_le2(p);
		p += 2;
	}
	return (sum);
}

/*
 * This is an internal helper function, called multiple times from the taste
 * function to try to locate a disklabel on the disk.  More civilized formats
 * will not need this, as there is only one possible place on disk to look
 * for the magic spot.
 */

static int
g_bsd_try(struct g_geom *gp, struct g_slicer *gsp, struct g_consumer *cp, int secsize, struct g_bsd_softc *ms, off_t offset)
{
	int error;
	u_char *buf;
	struct disklabel *dl;
	off_t secoff;

	/*
	 * We need to read entire aligned sectors, and we assume that the
	 * disklabel does not span sectors, so one sector is enough.
	 */
	error = 0;
	secoff = offset % secsize;
	buf = g_read_data(cp, offset - secoff, secsize, &error);
	if (buf == NULL || error != 0)
		return (ENOENT);

	/* Decode into our native format. */
	dl = &ms->ondisk;
	g_bsd_ledec_disklabel(buf + secoff, dl);

	ondisk2inram(ms);

	dl = &ms->inram;
	/* Does it look like a label at all? */
	if (g_bsd_checklabel(dl))
		error = ENOENT;
	/* ... and does the raw data have a good checksum? */
	if (error == 0 && g_bsd_lesum(dl, buf + secoff) != 0)
		error = ENOENT;

	/* Remember to free the buffer g_read_data() gave us. */
	g_free(buf);

	/* If we had a label, record it properly. */
	if (error == 0) {
		gsp->frontstuff = 16 * secsize;	/* XXX */
		ms->labeloffset = offset;
		g_topology_lock();
		g_slice_conf_hot(gp, 0, offset, g_bsd_ondisk_size());
		g_topology_unlock();
	}
	return (error);
}

/*
 * Implement certain ioctls to modify disklabels with.  This function
 * is called by the event handler thread with topology locked as result
 * of the g_call_me() in g_bsd_start().  It is not necessary to keep
 * topology locked all the time but make sure to return with topology
 * locked as well.
 */

static void
g_bsd_ioctl(void *arg)
{
	struct bio *bp;
	struct g_geom *gp;
	struct g_slicer *gsp;
	struct g_bsd_softc *ms;
	struct disklabel *dl;
	struct g_ioctl *gio;
	struct g_consumer *cp;
	u_char *buf;
	off_t secoff;
	u_int secsize;
	int error, i;
	uint64_t sum;

	/* We don't need topology for now. */
	g_topology_unlock();

	/* Get hold of the interesting bits from the bio. */
	bp = arg;
	gp = bp->bio_to->geom;
	gsp = gp->softc;
	ms = gsp->softc;
	gio = (struct g_ioctl *)bp->bio_data;

	/* The disklabel to set is the ioctl argument. */
	dl = gio->data;

	/* Validate and modify our slice instance to match. */
	error = g_bsd_modify(gp, dl);	/* Picks up topology lock on success. */
	if (error) {
		g_topology_lock();
		g_io_deliver(bp, error);
		return;
	}
	/* Update our copy of the disklabel. */
	ms->inram = *dl;
	inram2ondisk(ms);

	if (gio->cmd == DIOCSDINFO) {
		g_io_deliver(bp, 0);
		return;
	}
	KASSERT(gio->cmd == DIOCWDINFO, ("Unknown ioctl in g_bsd_ioctl"));
	cp = LIST_FIRST(&gp->consumer);
	/* Get sector size, we need it to read data. */
	secsize = cp->provider->sectorsize;
	secoff = ms->labeloffset % secsize;
	buf = g_read_data(cp, ms->labeloffset - secoff, secsize, &error);
	if (buf == NULL || error != 0) {
		g_io_deliver(bp, error);
		return;
	}
	dl = &ms->ondisk;
	g_bsd_leenc_disklabel(buf + secoff, dl);
	if (ms->labeloffset == ALPHA_LABEL_OFFSET) {
		sum = 0;
		for (i = 0; i < 63; i++)
			sum += g_dec_le8(buf + i * 8);
		g_enc_le8(buf + 504, sum);
	}
	error = g_write_data(cp, ms->labeloffset - secoff, buf, secsize);
	g_free(buf);
	g_io_deliver(bp, error);
}

/*
 * If the user tries to overwrite our disklabel through an open partition
 * or via a magicwrite config call, we end up here and try to prevent
 * footshooting as best we can.
 */
static void
g_bsd_hotwrite(void *arg)
{
	struct bio *bp;
	struct g_geom *gp;
	struct g_slicer *gsp;
	struct g_slice *gsl;
	struct g_bsd_softc *ms;
	struct g_bsd_softc fake;
	u_char *p;
	int error;
	
	bp = arg;
	gp = bp->bio_to->geom;
	gsp = gp->softc;
	ms = gsp->softc;
	gsl = &gsp->slices[bp->bio_to->index];
	p = (u_char*)bp->bio_data + ms->labeloffset 
	    - (bp->bio_offset + gsl->offset);
	g_bsd_ledec_disklabel(p, &fake.ondisk);
	
	ondisk2inram(&fake);
	if (g_bsd_checklabel(&fake.inram)) {
		g_io_deliver(bp, EPERM);
		return;
	}
	if (g_bsd_lesum(&fake.ondisk, p) != 0) {
		g_io_deliver(bp, EPERM);
		return;
	}
	g_topology_unlock();
	error = g_bsd_modify(gp, &fake.inram);	/* May pick up topology. */
	if (error) {
		g_io_deliver(bp, EPERM);
		g_topology_lock();
		return;
	}
	/* Update our copy of the disklabel. */
	ms->inram = fake.inram;
	inram2ondisk(ms);
	g_bsd_leenc_disklabel(p, &ms->ondisk);
	g_slice_finish_hot(bp);
}

/*-
 * This start routine is only called for non-trivial requests, all the
 * trivial ones are handled autonomously by the slice code.
 * For requests we handle here, we must call the g_io_deliver() on the
 * bio, and return non-zero to indicate to the slice code that we did so.
 * This code executes in the "DOWN" I/O path, this means:
 *    * No sleeping.
 *    * Don't grab the topology lock.
 *    * Don't call biowait, g_getattr(), g_setattr() or g_read_data()
 */

static int
g_bsd_start(struct bio *bp)
{
	struct g_geom *gp;
	struct g_bsd_softc *ms;
	struct g_slicer *gsp;
	struct g_ioctl *gio;
	int error;

	gp = bp->bio_to->geom;
	gsp = gp->softc;
	ms = gsp->softc;
	switch(bp->bio_cmd) {
	case BIO_READ:
		/* We allow reading of our hot spots */
		return (0);
	case BIO_DELETE:
		/* We do not allow deleting our hot spots */
		return (EPERM);
	case BIO_WRITE:
		g_call_me(g_bsd_hotwrite, bp);
		return (EJUSTRETURN);
	case BIO_GETATTR:
	case BIO_SETATTR:
		break;
	default:
		KASSERT(0 == 1, ("Unknown bio_cmd in g_bsd_start (%d)",
		    bp->bio_cmd));
	}

	/* We only handle ioctl(2) requests of the right format. */
	if (strcmp(bp->bio_attribute, "GEOM::ioctl"))
		return (0);
	else if (bp->bio_length != sizeof(*gio))
		return (0);

	/* Get hold of the ioctl parameters. */
	gio = (struct g_ioctl *)bp->bio_data;

	switch (gio->cmd) {
	case DIOCGDINFO:
		/* Return a copy of the disklabel to userland. */
		bcopy(&ms->inram, gio->data, sizeof(ms->inram));
		g_io_deliver(bp, 0);
		return (1);
	case DIOCSDINFO:
	case DIOCWDINFO:
		/*
		 * These we cannot do without the topology lock and some
		 * some I/O requests.  Ask the event-handler to schedule
		 * us in a less restricted environment.
		 */
		error = g_call_me(g_bsd_ioctl, bp);
		if (error)
			g_io_deliver(bp, error);
		/*
		 * We must return non-zero to indicate that we will deal
		 * with this bio, even though we have not done so yet.
		 */
		return (1);
	default:
		return (0);
	}
}

/*
 * Dump configuration information in XML format.
 * Notice that the function is called once for the geom and once for each
 * consumer and provider.  We let g_slice_dumpconf() do most of the work.
 */
static void
g_bsd_dumpconf(struct sbuf *sb, const char *indent, struct g_geom *gp, struct g_consumer *cp, struct g_provider *pp)
{
	struct g_bsd_softc *ms;
	struct g_slicer *gsp;

	gsp = gp->softc;
	ms = gsp->softc;
	g_slice_dumpconf(sb, indent, gp, cp, pp);
	if (indent != NULL && pp == NULL && cp == NULL) {
		sbuf_printf(sb, "%s<labeloffset>%jd</labeloffset>\n",
		    indent, (intmax_t)ms->labeloffset);
		sbuf_printf(sb, "%s<rawoffset>%jd</rawoffset>\n",
		    indent, (intmax_t)ms->rawoffset);
		sbuf_printf(sb, "%s<mbroffset>%jd</mbroffset>\n",
		    indent, (intmax_t)ms->mbroffset);
	}
}

/*
 * The taste function is called from the event-handler, with the topology
 * lock already held and a provider to examine.  The flags are unused.
 *
 * If flags == G_TF_NORMAL, the idea is to take a bite of the provider and
 * if we find valid, consistent magic on it, build a geom on it.
 * any magic bits which indicate that we should automatically put a BSD
 * geom on it.
 *
 * There may be cases where the operator would like to put a BSD-geom on
 * providers which do not meet all of the requirements.  This can be done
 * by instead passing the G_TF_INSIST flag, which will override these
 * checks.
 *
 * The final flags value is G_TF_TRANSPARENT, which instructs the method
 * to put a geom on top of the provider and configure it to be as transparent
 * as possible.  This is not really relevant to the BSD method and therefore
 * not implemented here.
 */

static struct g_geom *
g_bsd_taste(struct g_class *mp, struct g_provider *pp, int flags)
{
	struct g_geom *gp;
	struct g_consumer *cp;
	int error, i;
	struct g_bsd_softc *ms;
	struct disklabel *dl;
	u_int secsize;
	struct g_slicer *gsp;

	g_trace(G_T_TOPOLOGY, "bsd_taste(%s,%s)", mp->name, pp->name);
	g_topology_assert();

	/* We don't implement transparent inserts. */
	if (flags == G_TF_TRANSPARENT)
		return (NULL);

	/*
	 * The BSD-method will not automatically configure itself recursively
	 * Note that it is legal to examine the class-name of our provider,
	 * nothing else should ever be examined inside the provider.
	 */
	if (flags == G_TF_NORMAL &&
	    !strcmp(pp->geom->class->name, BSD_CLASS_NAME))
		return (NULL);

	/*
	 * BSD labels are a subclass of the general "slicing" topology so
	 * a lot of the work can be done by the common "slice" code.
	 * Create a geom with space for MAXPARTITIONS providers, one consumer
	 * and a softc structure for us.  Specify the provider to attach
	 * the consumer to and our "start" routine for special requests.
	 * The provider is opened with mode (1,0,0) so we can do reads
	 * from it.
	 */
	gp = g_slice_new(mp, MAXPARTITIONS, pp, &cp, &ms,
	     sizeof(*ms), g_bsd_start);
	if (gp == NULL)
		return (NULL);

	/*
	 * Now that we have attached to and opened our provider, we do
	 * not need the topology lock until we change the topology again
	 * next time.
	 */
	g_topology_unlock();

	/*
	 * Fill in the optional details, in our case we have a dumpconf
	 * routine which the "slice" code should call at the right time
	 */
	gp->dumpconf = g_bsd_dumpconf;

	/* Get the geom_slicer softc from the geom. */
	gsp = gp->softc;

	/*
	 * The do...while loop here allows us to have multiple escapes
	 * using a simple "break".  This improves code clarity without
	 * ending up in deep nesting and without using goto or come from.
	 */
	do {
		/*
		 * If the provider is an MBR we will only auto attach
		 * to type 165 slices in the G_TF_NORMAL case.  We will
		 * attach to any other type (BSD was handles above)
		 */
		error = g_getattr("MBR::type", cp, &i);
		if (!error) {
			if (i != 165 && flags == G_TF_NORMAL)
				break;
			error = g_getattr("MBR::offset", cp, &ms->mbroffset);
			if (error)
				break;
		}

		/* Same thing if we are inside a PC98 */
		error = g_getattr("PC98::type", cp, &i);
		if (!error) {
			if (i != 0xc494 && flags == G_TF_NORMAL)
				break;
			error = g_getattr("PC98::offset", cp, &ms->mbroffset);
			if (error)
				break;
		}

		/* Get sector size, we need it to read data. */
		secsize = cp->provider->sectorsize;
		if (secsize < 512)
			break;

		/* First look for a label at the start of the second sector. */
		error = g_bsd_try(gp, gsp, cp, secsize, ms, secsize);

		/* Next, look for alpha labels */
		if (error)
			error = g_bsd_try(gp, gsp, cp, secsize, ms,
			    ALPHA_LABEL_OFFSET);

		/* If we didn't find a label, punt. */
		if (error)
			break;

		/*
		 * Process the found disklabel, and modify our "slice"
		 * instance to match it, if possible.
		 */
		dl = &ms->inram;
		error = g_bsd_modify(gp, dl);	/* Picks up topology lock. */
		if (!error)
			g_topology_unlock();
		break;
	} while (0);

	/* Success of failure, we can close our provider now. */
	g_topology_lock();
	error = g_access_rel(cp, -1, 0, 0);

	/* If we have configured any providers, return the new geom. */
	if (gsp->nprovider > 0)
		return (gp);
	/*
	 * ...else push the "self-destruct" button, by spoiling our own
	 * consumer.  This triggers a call to g_std_spoiled which will
	 * dismantle what was setup.
	 */
	g_std_spoiled(cp);
	return (NULL);
}

/* Finally, register with GEOM infrastructure. */
static struct g_class g_bsd_class = {
	BSD_CLASS_NAME,
	g_bsd_taste,
	NULL,
	G_CLASS_INITIALIZER
};

DECLARE_GEOM_CLASS(g_bsd_class, g_bsd);
OpenPOWER on IntegriCloud