aboutsummaryrefslogtreecommitdiff
path: root/pc-bios/s390-ccw/bootmap.c
blob: 56411ab3b67e8071ef6f7e5f56b9b7830d7ed231 (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
/*
 * QEMU S390 bootmap interpreter
 *
 * Copyright (c) 2009 Alexander Graf <agraf@suse.de>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or (at
 * your option) any later version. See the COPYING file in the top-level
 * directory.
 */

#include "libc.h"
#include "s390-ccw.h"
#include "s390-arch.h"
#include "bootmap.h"
#include "virtio.h"
#include "bswap.h"

#ifdef DEBUG
/* #define DEBUG_FALLBACK */
#endif

#ifdef DEBUG_FALLBACK
#define dputs(txt) \
    do { sclp_print("zipl: " txt); } while (0)
#else
#define dputs(fmt, ...) \
    do { } while (0)
#endif

/* Scratch space */
static uint8_t sec[MAX_SECTOR_SIZE*4] __attribute__((__aligned__(PAGE_SIZE)));

const uint8_t el_torito_magic[] = "EL TORITO SPECIFICATION"
                                  "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";

/*
 * Match two CCWs located after PSW and eight filler bytes.
 * From libmagic and arch/s390/kernel/head.S.
 */
const uint8_t linux_s390_magic[] = "\x02\x00\x00\x18\x60\x00\x00\x50\x02\x00"
                                   "\x00\x68\x60\x00\x00\x50\x40\x40\x40\x40"
                                   "\x40\x40\x40\x40";

static inline bool is_iso_vd_valid(IsoVolDesc *vd)
{
    const uint8_t vol_desc_magic[] = "CD001";

    return !memcmp(&vd->ident[0], vol_desc_magic, 5) &&
           vd->version == 0x1 &&
           vd->type <= VOL_DESC_TYPE_PARTITION;
}

/***********************************************************************
 * IPL an ECKD DASD (CDL or LDL/CMS format)
 */

static unsigned char _bprs[8*1024]; /* guessed "max" ECKD sector size */
static const int max_bprs_entries = sizeof(_bprs) / sizeof(ExtEckdBlockPtr);
static uint8_t _s2[MAX_SECTOR_SIZE * 3] __attribute__((__aligned__(PAGE_SIZE)));
static void *s2_prev_blk = _s2;
static void *s2_cur_blk = _s2 + MAX_SECTOR_SIZE;
static void *s2_next_blk = _s2 + MAX_SECTOR_SIZE * 2;

static inline void verify_boot_info(BootInfo *bip)
{
    IPL_assert(magic_match(bip->magic, ZIPL_MAGIC), "No zIPL sig in BootInfo");
    IPL_assert(bip->version == BOOT_INFO_VERSION, "Wrong zIPL version");
    IPL_assert(bip->bp_type == BOOT_INFO_BP_TYPE_IPL, "DASD is not for IPL");
    IPL_assert(bip->dev_type == BOOT_INFO_DEV_TYPE_ECKD, "DASD is not ECKD");
    IPL_assert(bip->flags == BOOT_INFO_FLAGS_ARCH, "Not for this arch");
    IPL_assert(block_size_ok(bip->bp.ipl.bm_ptr.eckd.bptr.size),
               "Bad block size in zIPL section of the 1st record.");
}

static block_number_t eckd_block_num(EckdCHS *chs)
{
    const uint64_t sectors = virtio_get_sectors();
    const uint64_t heads = virtio_get_heads();
    const uint64_t cylinder = chs->cylinder
                            + ((chs->head & 0xfff0) << 12);
    const uint64_t head = chs->head & 0x000f;
    const block_number_t block = sectors * heads * cylinder
                               + sectors * head
                               + chs->sector
                               - 1; /* block nr starts with zero */
    return block;
}

static bool eckd_valid_address(BootMapPointer *p)
{
    const uint64_t head = p->eckd.chs.head & 0x000f;

    if (head >= virtio_get_heads()
        ||  p->eckd.chs.sector > virtio_get_sectors()
        ||  p->eckd.chs.sector <= 0) {
        return false;
    }

    if (!virtio_guessed_disk_nature() &&
        eckd_block_num(&p->eckd.chs) >= virtio_get_blocks()) {
        return false;
    }

    return true;
}

static block_number_t load_eckd_segments(block_number_t blk, uint64_t *address)
{
    block_number_t block_nr;
    int j, rc;
    BootMapPointer *bprs = (void *)_bprs;
    bool more_data;

    memset(_bprs, FREE_SPACE_FILLER, sizeof(_bprs));
    read_block(blk, bprs, "BPRS read failed");

    do {
        more_data = false;
        for (j = 0;; j++) {
            block_nr = eckd_block_num(&bprs[j].xeckd.bptr.chs);
            if (is_null_block_number(block_nr)) { /* end of chunk */
                break;
            }

            /* we need the updated blockno for the next indirect entry
             * in the chain, but don't want to advance address
             */
            if (j == (max_bprs_entries - 1)) {
                break;
            }

            IPL_assert(block_size_ok(bprs[j].xeckd.bptr.size),
                       "bad chunk block size");
            IPL_assert(eckd_valid_address(&bprs[j]), "bad chunk ECKD addr");

            if ((bprs[j].xeckd.bptr.count == 0) && unused_space(&(bprs[j+1]),
                sizeof(EckdBlockPtr))) {
                /* This is a "continue" pointer.
                 * This ptr should be the last one in the current
                 * script section.
                 * I.e. the next ptr must point to the unused memory area
                 */
                memset(_bprs, FREE_SPACE_FILLER, sizeof(_bprs));
                read_block(block_nr, bprs, "BPRS continuation read failed");
                more_data = true;
                break;
            }

            /* Load (count+1) blocks of code at (block_nr)
             * to memory (address).
             */
            rc = virtio_read_many(block_nr, (void *)(*address),
                                  bprs[j].xeckd.bptr.count+1);
            IPL_assert(rc == 0, "code chunk read failed");

            *address += (bprs[j].xeckd.bptr.count+1) * virtio_get_block_size();
        }
    } while (more_data);
    return block_nr;
}

static bool find_zipl_boot_menu_banner(int *offset)
{
    int i;

    /* Menu banner starts with "zIPL" */
    for (i = 0; i <= virtio_get_block_size() - 4; i++) {
        if (magic_match(s2_cur_blk + i, ZIPL_MAGIC_EBCDIC)) {
            *offset = i;
            return true;
        }
    }

    return false;
}

static int eckd_get_boot_menu_index(block_number_t s1b_block_nr)
{
    block_number_t cur_block_nr;
    block_number_t prev_block_nr = 0;
    block_number_t next_block_nr = 0;
    EckdStage1b *s1b = (void *)sec;
    int banner_offset;
    int i;

    /* Get Stage1b data */
    memset(sec, FREE_SPACE_FILLER, sizeof(sec));
    read_block(s1b_block_nr, s1b, "Cannot read stage1b boot loader");

    memset(_s2, FREE_SPACE_FILLER, sizeof(_s2));

    /* Get Stage2 data */
    for (i = 0; i < STAGE2_BLK_CNT_MAX; i++) {
        cur_block_nr = eckd_block_num(&s1b->seek[i].chs);

        if (!cur_block_nr || is_null_block_number(cur_block_nr)) {
            break;
        }

        read_block(cur_block_nr, s2_cur_blk, "Cannot read stage2 boot loader");

        if (find_zipl_boot_menu_banner(&banner_offset)) {
            /*
             * Load the adjacent blocks to account for the
             * possibility of menu data spanning multiple blocks.
             */
            if (prev_block_nr) {
                read_block(prev_block_nr, s2_prev_blk,
                           "Cannot read stage2 boot loader");
            }

            if (i + 1 < STAGE2_BLK_CNT_MAX) {
                next_block_nr = eckd_block_num(&s1b->seek[i + 1].chs);
            }

            if (next_block_nr && !is_null_block_number(next_block_nr)) {
                read_block(next_block_nr, s2_next_blk,
                           "Cannot read stage2 boot loader");
            }

            return menu_get_zipl_boot_index(s2_cur_blk + banner_offset);
        }

        prev_block_nr = cur_block_nr;
    }

    sclp_print("No zipl boot menu data found. Booting default entry.");
    return 0;
}

static void run_eckd_boot_script(block_number_t bmt_block_nr,
                                 block_number_t s1b_block_nr)
{
    int i;
    unsigned int loadparm = get_loadparm_index();
    block_number_t block_nr;
    uint64_t address;
    BootMapTable *bmt = (void *)sec;
    BootMapScript *bms = (void *)sec;

    if (menu_is_enabled_zipl()) {
        loadparm = eckd_get_boot_menu_index(s1b_block_nr);
    }

    debug_print_int("loadparm", loadparm);
    IPL_assert(loadparm < MAX_BOOT_ENTRIES, "loadparm value greater than"
               " maximum number of boot entries allowed");

    memset(sec, FREE_SPACE_FILLER, sizeof(sec));
    read_block(bmt_block_nr, sec, "Cannot read Boot Map Table");

    block_nr = eckd_block_num(&bmt->entry[loadparm].xeckd.bptr.chs);
    IPL_assert(block_nr != -1, "Cannot find Boot Map Table Entry");

    memset(sec, FREE_SPACE_FILLER, sizeof(sec));
    read_block(block_nr, sec, "Cannot read Boot Map Script");

    for (i = 0; bms->entry[i].type == BOOT_SCRIPT_LOAD ||
                bms->entry[i].type == BOOT_SCRIPT_SIGNATURE; i++) {

        /* We don't support secure boot yet, so we skip signature entries */
        if (bms->entry[i].type == BOOT_SCRIPT_SIGNATURE) {
            continue;
        }

        address = bms->entry[i].address.load_address;
        block_nr = eckd_block_num(&bms->entry[i].blkptr.xeckd.bptr.chs);

        do {
            block_nr = load_eckd_segments(block_nr, &address);
        } while (block_nr != -1);
    }

    IPL_assert(bms->entry[i].type == BOOT_SCRIPT_EXEC,
               "Unknown script entry type");
    write_reset_psw(bms->entry[i].address.load_address); /* no return */
    jump_to_IPL_code(0); /* no return */
}

static void ipl_eckd_cdl(void)
{
    XEckdMbr *mbr;
    EckdCdlIpl2 *ipl2 = (void *)sec;
    IplVolumeLabel *vlbl = (void *)sec;
    block_number_t bmt_block_nr, s1b_block_nr;

    /* we have just read the block #0 and recognized it as "IPL1" */
    sclp_print("CDL\n");

    memset(sec, FREE_SPACE_FILLER, sizeof(sec));
    read_block(1, ipl2, "Cannot read IPL2 record at block 1");

    mbr = &ipl2->mbr;
    if (!magic_match(mbr, ZIPL_MAGIC)) {
        sclp_print("No zIPL section in IPL2 record.\n");
        return;
    }
    if (!block_size_ok(mbr->blockptr.xeckd.bptr.size)) {
        sclp_print("Bad block size in zIPL section of IPL2 record.\n");
        return;
    }
    if (mbr->dev_type != DEV_TYPE_ECKD) {
        sclp_print("Non-ECKD device type in zIPL section of IPL2 record.\n");
        return;
    }

    /* save pointer to Boot Map Table */
    bmt_block_nr = eckd_block_num(&mbr->blockptr.xeckd.bptr.chs);

    /* save pointer to Stage1b Data */
    s1b_block_nr = eckd_block_num(&ipl2->stage1.seek[0].chs);

    memset(sec, FREE_SPACE_FILLER, sizeof(sec));
    read_block(2, vlbl, "Cannot read Volume Label at block 2");
    if (!magic_match(vlbl->key, VOL1_MAGIC)) {
        sclp_print("Invalid magic of volume label block.\n");
        return;
    }
    if (!magic_match(vlbl->f.key, VOL1_MAGIC)) {
        sclp_print("Invalid magic of volser block.\n");
        return;
    }
    print_volser(vlbl->f.volser);

    run_eckd_boot_script(bmt_block_nr, s1b_block_nr);
    /* no return */
}

static void print_eckd_ldl_msg(ECKD_IPL_mode_t mode)
{
    LDL_VTOC *vlbl = (void *)sec; /* already read, 3rd block */
    char msg[4] = { '?', '.', '\n', '\0' };

    sclp_print((mode == ECKD_CMS) ? "CMS" : "LDL");
    sclp_print(" version ");
    switch (vlbl->LDL_version) {
    case LDL1_VERSION:
        msg[0] = '1';
        break;
    case LDL2_VERSION:
        msg[0] = '2';
        break;
    default:
        msg[0] = ebc2asc[vlbl->LDL_version];
        msg[1] = '?';
        break;
    }
    sclp_print(msg);
    print_volser(vlbl->volser);
}

static void ipl_eckd_ldl(ECKD_IPL_mode_t mode)
{
    block_number_t bmt_block_nr, s1b_block_nr;
    EckdLdlIpl1 *ipl1 = (void *)sec;

    if (mode != ECKD_LDL_UNLABELED) {
        print_eckd_ldl_msg(mode);
    }

    /* DO NOT read BootMap pointer (only one, xECKD) at block #2 */

    memset(sec, FREE_SPACE_FILLER, sizeof(sec));
    read_block(0, sec, "Cannot read block 0 to grab boot info.");
    if (mode == ECKD_LDL_UNLABELED) {
        if (!magic_match(ipl1->bip.magic, ZIPL_MAGIC)) {
            return; /* not applicable layout */
        }
        sclp_print("unlabeled LDL.\n");
    }
    verify_boot_info(&ipl1->bip);

    /* save pointer to Boot Map Table */
    bmt_block_nr = eckd_block_num(&ipl1->bip.bp.ipl.bm_ptr.eckd.bptr.chs);

    /* save pointer to Stage1b Data */
    s1b_block_nr = eckd_block_num(&ipl1->stage1.seek[0].chs);

    run_eckd_boot_script(bmt_block_nr, s1b_block_nr);
    /* no return */
}

static void print_eckd_msg(void)
{
    char msg[] = "Using ECKD scheme (block size *****), ";
    char *p = &msg[34], *q = &msg[30];
    int n = virtio_get_block_size();

    /* Fill in the block size and show up the message */
    if (n > 0 && n <= 99999) {
        while (n) {
            *p-- = '0' + (n % 10);
            n /= 10;
        }
        while (p >= q) {
            *p-- = ' ';
        }
    }
    sclp_print(msg);
}

static void ipl_eckd(void)
{
    XEckdMbr *mbr = (void *)sec;
    LDL_VTOC *vlbl = (void *)sec;

    print_eckd_msg();

    /* Grab the MBR again */
    memset(sec, FREE_SPACE_FILLER, sizeof(sec));
    read_block(0, mbr, "Cannot read block 0 on DASD");

    if (magic_match(mbr->magic, IPL1_MAGIC)) {
        ipl_eckd_cdl();         /* only returns in case of error */
        return;
    }

    /* LDL/CMS? */
    memset(sec, FREE_SPACE_FILLER, sizeof(sec));
    read_block(2, vlbl, "Cannot read block 2");

    if (magic_match(vlbl->magic, CMS1_MAGIC)) {
        ipl_eckd_ldl(ECKD_CMS); /* no return */
    }
    if (magic_match(vlbl->magic, LNX1_MAGIC)) {
        ipl_eckd_ldl(ECKD_LDL); /* no return */
    }

    ipl_eckd_ldl(ECKD_LDL_UNLABELED); /* it still may return */
    /*
     * Ok, it is not a LDL by any means.
     * It still might be a CDL with zero record keys for IPL1 and IPL2
     */
    ipl_eckd_cdl();
}

/***********************************************************************
 * IPL a SCSI disk
 */

static void zipl_load_segment(ComponentEntry *entry)
{
    const int max_entries = (MAX_SECTOR_SIZE / sizeof(ScsiBlockPtr));
    ScsiBlockPtr *bprs = (void *)sec;
    const int bprs_size = sizeof(sec);
    block_number_t blockno;
    uint64_t address;
    int i;
    char err_msg[] = "zIPL failed to read BPRS at 0xZZZZZZZZZZZZZZZZ";
    char *blk_no = &err_msg[30]; /* where to print blockno in (those ZZs) */

    blockno = entry->data.blockno;
    address = entry->compdat.load_addr;

    debug_print_int("loading segment at block", blockno);
    debug_print_int("addr", address);

    do {
        memset(bprs, FREE_SPACE_FILLER, bprs_size);
        fill_hex_val(blk_no, &blockno, sizeof(blockno));
        read_block(blockno, bprs, err_msg);

        for (i = 0;; i++) {
            uint64_t *cur_desc = (void *)&bprs[i];

            blockno = bprs[i].blockno;
            if (!blockno) {
                break;
            }

            /* we need the updated blockno for the next indirect entry in the
               chain, but don't want to advance address */
            if (i == (max_entries - 1)) {
                break;
            }

            if (bprs[i].blockct == 0 && unused_space(&bprs[i + 1],
                sizeof(ScsiBlockPtr))) {
                /* This is a "continue" pointer.
                 * This ptr is the last one in the current script section.
                 * I.e. the next ptr must point to the unused memory area.
                 * The blockno is not zero, so the upper loop must continue
                 * reading next section of BPRS.
                 */
                break;
            }
            address = virtio_load_direct(cur_desc[0], cur_desc[1], 0,
                                         (void *)address);
            IPL_assert(address != -1, "zIPL load segment failed");
        }
    } while (blockno);
}

/* Run a zipl program */
static void zipl_run(ScsiBlockPtr *pte)
{
    ComponentHeader *header;
    ComponentEntry *entry;
    uint8_t tmp_sec[MAX_SECTOR_SIZE];

    read_block(pte->blockno, tmp_sec, "Cannot read header");
    header = (ComponentHeader *)tmp_sec;

    IPL_assert(magic_match(tmp_sec, ZIPL_MAGIC), "No zIPL magic in header");
    IPL_assert(header->type == ZIPL_COMP_HEADER_IPL, "Bad header type");

    dputs("start loading images\n");

    /* Load image(s) into RAM */
    entry = (ComponentEntry *)(&header[1]);
    while (entry->component_type == ZIPL_COMP_ENTRY_LOAD ||
           entry->component_type == ZIPL_COMP_ENTRY_SIGNATURE) {

        /* We don't support secure boot yet, so we skip signature entries */
        if (entry->component_type == ZIPL_COMP_ENTRY_SIGNATURE) {
            entry++;
            continue;
        }

        zipl_load_segment(entry);

        entry++;

        IPL_assert((uint8_t *)(&entry[1]) <= (tmp_sec + MAX_SECTOR_SIZE),
                   "Wrong entry value");
    }

    IPL_assert(entry->component_type == ZIPL_COMP_ENTRY_EXEC, "No EXEC entry");

    /* should not return */
    write_reset_psw(entry->compdat.load_psw);
    jump_to_IPL_code(0);
}

static void ipl_scsi(void)
{
    ScsiMbr *mbr = (void *)sec;
    int program_table_entries = 0;
    BootMapTable *prog_table = (void *)sec;
    unsigned int loadparm = get_loadparm_index();
    bool valid_entries[MAX_BOOT_ENTRIES] = {false};
    size_t i;

    /* Grab the MBR */
    memset(sec, FREE_SPACE_FILLER, sizeof(sec));
    read_block(0, mbr, "Cannot read block 0");

    if (!magic_match(mbr->magic, ZIPL_MAGIC)) {
        return;
    }

    sclp_print("Using SCSI scheme.\n");
    debug_print_int("MBR Version", mbr->version_id);
    IPL_check(mbr->version_id == 1,
              "Unknown MBR layout version, assuming version 1");
    debug_print_int("program table", mbr->pt.blockno);
    IPL_assert(mbr->pt.blockno, "No Program Table");

    /* Parse the program table */
    read_block(mbr->pt.blockno, sec, "Error reading Program Table");
    IPL_assert(magic_match(sec, ZIPL_MAGIC), "No zIPL magic in PT");

    for (i = 0; i < MAX_BOOT_ENTRIES; i++) {
        if (prog_table->entry[i].scsi.blockno) {
            valid_entries[i] = true;
            program_table_entries++;
        }
    }

    debug_print_int("program table entries", program_table_entries);
    IPL_assert(program_table_entries != 0, "Empty Program Table");

    if (menu_is_enabled_enum()) {
        loadparm = menu_get_enum_boot_index(valid_entries);
    }

    debug_print_int("loadparm", loadparm);
    IPL_assert(loadparm < MAX_BOOT_ENTRIES, "loadparm value greater than"
               " maximum number of boot entries allowed");

    zipl_run(&prog_table->entry[loadparm].scsi); /* no return */
}

/***********************************************************************
 * IPL El Torito ISO9660 image or DVD
 */

static bool is_iso_bc_entry_compatible(IsoBcSection *s)
{
    uint8_t *magic_sec = (uint8_t *)(sec + ISO_SECTOR_SIZE);

    if (s->unused || !s->sector_count) {
        return false;
    }
    read_iso_sector(bswap32(s->load_rba), magic_sec,
                    "Failed to read image sector 0");

    /* Checking bytes 8 - 32 for S390 Linux magic */
    return !memcmp(magic_sec + 8, linux_s390_magic, 24);
}

/* Location of the current sector of the directory */
static uint32_t sec_loc[ISO9660_MAX_DIR_DEPTH];
/* Offset in the current sector of the directory */
static uint32_t sec_offset[ISO9660_MAX_DIR_DEPTH];
/* Remained directory space in bytes */
static uint32_t dir_rem[ISO9660_MAX_DIR_DEPTH];

static inline uint32_t iso_get_file_size(uint32_t load_rba)
{
    IsoVolDesc *vd = (IsoVolDesc *)sec;
    IsoDirHdr *cur_record = &vd->vd.primary.rootdir;
    uint8_t *temp = sec + ISO_SECTOR_SIZE;
    int level = 0;

    read_iso_sector(ISO_PRIMARY_VD_SECTOR, sec,
                    "Failed to read ISO primary descriptor");
    sec_loc[0] = iso_733_to_u32(cur_record->ext_loc);
    dir_rem[0] = 0;
    sec_offset[0] = 0;

    while (level >= 0) {
        IPL_assert(sec_offset[level] <= ISO_SECTOR_SIZE,
                   "Directory tree structure violation");

        cur_record = (IsoDirHdr *)(temp + sec_offset[level]);

        if (sec_offset[level] == 0) {
            read_iso_sector(sec_loc[level], temp,
                            "Failed to read ISO directory");
            if (dir_rem[level] == 0) {
                /* Skip self and parent records */
                dir_rem[level] = iso_733_to_u32(cur_record->data_len) -
                                 cur_record->dr_len;
                sec_offset[level] += cur_record->dr_len;

                cur_record = (IsoDirHdr *)(temp + sec_offset[level]);
                dir_rem[level] -= cur_record->dr_len;
                sec_offset[level] += cur_record->dr_len;
                continue;
            }
        }

        if (!cur_record->dr_len || sec_offset[level] == ISO_SECTOR_SIZE) {
            /* Zero-padding and/or the end of current sector */
            dir_rem[level] -= ISO_SECTOR_SIZE - sec_offset[level];
            sec_offset[level] = 0;
            sec_loc[level]++;
        } else {
            /* The directory record is valid */
            if (load_rba == iso_733_to_u32(cur_record->ext_loc)) {
                return iso_733_to_u32(cur_record->data_len);
            }

            dir_rem[level] -= cur_record->dr_len;
            sec_offset[level] += cur_record->dr_len;

            if (cur_record->file_flags & 0x2) {
                /* Subdirectory */
                if (level == ISO9660_MAX_DIR_DEPTH - 1) {
                    sclp_print("ISO-9660 directory depth limit exceeded\n");
                } else {
                    level++;
                    sec_loc[level] = iso_733_to_u32(cur_record->ext_loc);
                    sec_offset[level] = 0;
                    dir_rem[level] = 0;
                    continue;
                }
            }
        }

        if (dir_rem[level] == 0) {
            /* Nothing remaining */
            level--;
            read_iso_sector(sec_loc[level], temp,
                            "Failed to read ISO directory");
        }
    }

    return 0;
}

static void load_iso_bc_entry(IsoBcSection *load)
{
    IsoBcSection s = *load;
    /*
     * According to spec, extent for each file
     * is padded and ISO_SECTOR_SIZE bytes aligned
     */
    uint32_t blks_to_load = bswap16(s.sector_count) >> ET_SECTOR_SHIFT;
    uint32_t real_size = iso_get_file_size(bswap32(s.load_rba));

    if (real_size) {
        /* Round up blocks to load */
        blks_to_load = (real_size + ISO_SECTOR_SIZE - 1) / ISO_SECTOR_SIZE;
        sclp_print("ISO boot image size verified\n");
    } else {
        sclp_print("ISO boot image size could not be verified\n");
    }

    read_iso_boot_image(bswap32(s.load_rba),
                        (void *)((uint64_t)bswap16(s.load_segment)),
                        blks_to_load);

    jump_to_low_kernel();
}

static uint32_t find_iso_bc(void)
{
    IsoVolDesc *vd = (IsoVolDesc *)sec;
    uint32_t block_num = ISO_PRIMARY_VD_SECTOR;

    if (virtio_read_many(block_num++, sec, 1)) {
        /* If primary vd cannot be read, there is no boot catalog */
        return 0;
    }

    while (is_iso_vd_valid(vd) && vd->type != VOL_DESC_TERMINATOR) {
        if (vd->type == VOL_DESC_TYPE_BOOT) {
            IsoVdElTorito *et = &vd->vd.boot;

            if (!memcmp(&et->el_torito[0], el_torito_magic, 32)) {
                return bswap32(et->bc_offset);
            }
        }
        read_iso_sector(block_num++, sec,
                        "Failed to read ISO volume descriptor");
    }

    return 0;
}

static IsoBcSection *find_iso_bc_entry(void)
{
    IsoBcEntry *e = (IsoBcEntry *)sec;
    uint32_t offset = find_iso_bc();
    int i;
    unsigned int loadparm = get_loadparm_index();

    if (!offset) {
        return NULL;
    }

    read_iso_sector(offset, sec, "Failed to read El Torito boot catalog");

    if (!is_iso_bc_valid(e)) {
        /* The validation entry is mandatory */
        panic("No valid boot catalog found!\n");
        return NULL;
    }

    /*
     * Each entry has 32 bytes size, so one sector cannot contain > 64 entries.
     * We consider only boot catalogs with no more than 64 entries.
     */
    for (i = 1; i < ISO_BC_ENTRY_PER_SECTOR; i++) {
        if (e[i].id == ISO_BC_BOOTABLE_SECTION) {
            if (is_iso_bc_entry_compatible(&e[i].body.sect)) {
                if (loadparm <= 1) {
                    /* found, default, or unspecified */
                    return &e[i].body.sect;
                }
                loadparm--;
            }
        }
    }

    panic("No suitable boot entry found on ISO-9660 media!\n");

    return NULL;
}

static void ipl_iso_el_torito(void)
{
    IsoBcSection *s = find_iso_bc_entry();

    if (s) {
        load_iso_bc_entry(s);
        /* no return */
    }
}

/***********************************************************************
 * Bus specific IPL sequences
 */

static void zipl_load_vblk(void)
{
    if (virtio_guessed_disk_nature()) {
        virtio_assume_iso9660();
    }
    ipl_iso_el_torito();

    if (virtio_guessed_disk_nature()) {
        sclp_print("Using guessed DASD geometry.\n");
        virtio_assume_eckd();
    }
    ipl_eckd();
}

static void zipl_load_vscsi(void)
{
    if (virtio_get_block_size() == VIRTIO_ISO_BLOCK_SIZE) {
        /* Is it an ISO image in non-CD drive? */
        ipl_iso_el_torito();
    }

    sclp_print("Using guessed DASD geometry.\n");
    virtio_assume_eckd();
    ipl_eckd();
}

/***********************************************************************
 * IPL starts here
 */

void zipl_load(void)
{
    VDev *vdev = virtio_get_device();

    if (vdev->is_cdrom) {
        ipl_iso_el_torito();
        panic("\n! Cannot IPL this ISO image !\n");
    }

    if (virtio_get_device_type() == VIRTIO_ID_NET) {
        jump_to_IPL_code(vdev->netboot_start_addr);
    }

    ipl_scsi();

    switch (virtio_get_device_type()) {
    case VIRTIO_ID_BLOCK:
        zipl_load_vblk();
        break;
    case VIRTIO_ID_SCSI:
        zipl_load_vscsi();
        break;
    default:
        panic("\n! Unknown IPL device type !\n");
    }

    sclp_print("zIPL load failed.\n");
}