This file is indexed.

/usr/share/systemtap/runtime/sym.c is in systemtap-common 2.9-2ubuntu2.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

   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
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
/* -*- linux-c -*- 
 * Symbolic Lookup Functions
 * Copyright (C) 2005-2014 Red Hat Inc.
 * Copyright (C) 2006 Intel Corporation.
 *
 * This file is part of systemtap, and is free software.  You can
 * redistribute it and/or modify it under the terms of the GNU General
 * Public License (GPL); either version 2, or (at your option) any
 * later version.
 */

#ifndef _STP_SYM_C_
#define _STP_SYM_C_

#include "sym.h"
#include "vma.c"
#include "stp_string.c"
#ifdef STP_NEED_LINE_DATA
#include "unwind/unwind.h"
#endif
#include <asm/unaligned.h>
#include <asm/uaccess.h>
#include <linux/list.h>
#include <linux/module.h>
#ifdef STAPCONF_PROBE_KERNEL
#include <linux/uaccess.h>
#endif

/* Returns absolute address of offset into kernel module/section.
   Returns zero when module and section couldn't be found
   (aren't in memory yet). */
static unsigned long _stp_kmodule_relocate(const char *module,
					   const char *section,
					   unsigned long offset)
{
  unsigned i, j;

  dbug_sym(1, "%s, %s, %lx\n", module, section, offset);

  /* absolute, unrelocated address */
  if (!module || !strcmp(section, "")
      ||_stp_num_modules == 0) {
    return offset;
  }

  for (i = 0; i < _stp_num_modules; i++) {
    struct _stp_module *m = _stp_modules[i];
    if (strcmp(module, m->name)) /* duplication apprx. not possible for kernel */
      continue;

    for (j = 0; j < m->num_sections; j++) {
      struct _stp_section *s = &m->sections[j];
      if (!strcmp(section, s->name)) {
	/* mod and sec name match. tsk should match dynamic/static. */
	if (s->static_addr != 0) {
	  unsigned long addr = offset + s->static_addr;
	  dbug_sym(1, "address=%lx\n", addr);
	  return addr;
	} else {
	  /* static section, not in memory yet? */
	  dbug_sym(1, "section %s, not in memory yet?", s->name);
	  return 0;
	}
      }
    }
  }

  return 0;
}

static unsigned long _stp_umodule_relocate(const char *path,
					   unsigned long offset,
					   struct task_struct *tsk)
{
  unsigned i;
  unsigned long vm_start = 0;

  dbug_sym(1, "[%d] %s, %lx\n", tsk->pid, path, offset);

  for (i = 0; i < _stp_num_modules; i++) {
    struct _stp_module *m = _stp_modules[i];

    if (strcmp(path, m->path)
        || m->num_sections != 1)
      continue;

    if (!strcmp(m->sections[0].name, ".absolute"))
      return offset;
    if (strcmp(m->sections[0].name, ".dynamic"))
      continue;

    if (stap_find_vma_map_info_user(tsk->group_leader, m,
				    &vm_start, NULL, NULL) == 0) {
      offset += vm_start;
      dbug_sym(1, "address=%lx\n", offset);
      return offset;
    }
  }

  return 0;
}

/* Return (kernel) module owner and, if sec != NULL, fills in closest
   section of the address if found, return NULL otherwise. */
static struct _stp_module *_stp_kmod_sec_lookup(unsigned long addr,
						struct _stp_section **sec)
{
  unsigned midx = 0;

  for (midx = 0; midx < _stp_num_modules; midx++)
    {
      unsigned secidx;
      for (secidx = 0; secidx < _stp_modules[midx]->num_sections; secidx++)
	{
	  unsigned long sec_addr;
	  unsigned long sec_size;
	  sec_addr = _stp_modules[midx]->sections[secidx].static_addr;
	  sec_size = _stp_modules[midx]->sections[secidx].size;
	  if (addr >= sec_addr && addr < sec_addr + sec_size)
            {
	      if (sec)
		*sec = & _stp_modules[midx]->sections[secidx];
	      return _stp_modules[midx];
	    }
	}
      }
  return NULL;
}

/* Return (user) module in which the the given addr falls.  Returns
   NULL when no module can be found that contains the addr.  Fills in
   vm_start (addr where module is mapped in) and (base) name of module
   when given.  Note that user modules always have exactly one section
   (.dynamic or .absolute). */
static struct _stp_module *_stp_umod_lookup(unsigned long addr,
					    struct task_struct *task,
					    const char **name,
					    unsigned long *vm_start,
					    unsigned long *vm_end)
{
  void *user = NULL;
#ifdef CONFIG_COMPAT
        /* Handle 32bit signed values in 64bit longs, chop off top bits. */
        if (test_tsk_thread_flag(task, TIF_32BIT))
          addr &= ((compat_ulong_t) ~0);
#endif
  if (stap_find_vma_map_info(task->group_leader, addr,
			     vm_start, vm_end, name, &user) == 0)
    if (user != NULL)
      {
	struct _stp_module *m = (struct _stp_module *)user;
	dbug_sym(1, "found module %s at 0x%lx\n", m->path,
		 vm_start ? *vm_start : 0);
	return m;
      }
  return NULL;
}

static const char *_stp_kallsyms_lookup(unsigned long addr,
                                        unsigned long *symbolsize,
                                        unsigned long *offset, 
                                        const char **modname, 
                                        /* char ** secname? */
					struct task_struct *task)
{
	struct _stp_module *m = NULL;
	struct _stp_section *sec = NULL;
	struct _stp_symbol *s = NULL;
	unsigned end, begin = 0;
	unsigned long rel_addr = 0;

	if (addr == 0)
	  return NULL;

	if (task)
	  {
	    unsigned long vm_start = 0;
	    unsigned long vm_end = 0;
#ifdef CONFIG_COMPAT
        /* Handle 32bit signed values in 64bit longs, chop off top bits.
           _stp_umod_lookup does the same, but we need it here for the
           binary search on addr below. */
        if (test_tsk_thread_flag(task, TIF_32BIT))
          addr &= ((compat_ulong_t) ~0);
#endif
	    m = _stp_umod_lookup(addr, task, modname, &vm_start, &vm_end);
	    if (m)
	      {
		sec = &m->sections[0];
		/* XXX .absolute sections really shouldn't be here... */
		if (strcmp(".dynamic", m->sections[0].name) == 0)
		  rel_addr = addr - vm_start;
		else
		  rel_addr = addr;
	      }
	    if (modname && *modname)
	      {
		/* In case no symbol is found, fill in based on module. */
		if (offset)
		  *offset = addr - vm_start;
		if (symbolsize)
		  *symbolsize = vm_end - vm_start;
	      }
	  }
	else
	  {
	    m = _stp_kmod_sec_lookup(addr, &sec);
	    if (m)
	      {
	        rel_addr = addr - sec->static_addr;
		if (modname)
		  *modname = m->name;
	      }
	  }

        if (unlikely (m == NULL || sec == NULL))
          return NULL;
        
        /* NB: relativize the address to the section. */
        addr = rel_addr;
	end = sec->num_symbols;

	/* binary search for symbols within the module */
	do {
		unsigned mid = (begin + end) / 2;
		if (addr < sec->symbols[mid].addr)
			end = mid;
		else
			begin = mid;
	} while (begin + 1 < end);
	/* result index in $begin */

	s = & sec->symbols[begin];
	if (likely(addr >= s->addr)) {
		if (offset)
			*offset = addr - s->addr;
                /* We could also pass sec->name here. */
		if (symbolsize) {
			if ((begin + 1) < sec->num_symbols)
				*symbolsize = sec->symbols[begin + 1].addr - s->addr;
			else
				*symbolsize = 0;
			// NB: This is only a heuristic.  Sometimes there are large
			// gaps between text areas of modules.
		}
		return s->symbol;
	}
	return NULL;
}

#ifdef STP_NEED_LINE_DATA
static void _stp_filename_lookup(struct _stp_module *mod, char ** filename,
                                 uint8_t *dirsecp, uint8_t *enddirsecp,
                                 unsigned fileidx, int user, int compat_task)
{
  uint8_t *linep = dirsecp;
  static char fullpath [MAXSTRINGLEN];
  char *dirname_entry = NULL, *filename_entry = NULL;
  unsigned diridx = 0, i, j;

  // skip past the directory table in the debug_line info
  while (*linep != 0 && linep < enddirsecp)
    {
      char *entry = (char *) linep;
      uint8_t *endnamep = (uint8_t *) memchr (entry, '\0', (size_t) (enddirsecp-linep));
      if (endnamep == NULL || (endnamep + 1) > enddirsecp)
        return;
      linep = endnamep + 1;
    }

  if ((char) linep[0] != '\0')
    return;
  ++linep;

  // at the filename table
  for (i = 1; *linep != 0 && linep < enddirsecp; ++i)
    {
      uint8_t *endnamep = NULL;
      filename_entry = (char *) linep;
      endnamep = (uint8_t *) memchr (filename_entry, '\0', (size_t) (enddirsecp-linep));
      if (endnamep == NULL || (endnamep + 1) > enddirsecp)
        return;

      // move the line pointer past the file name. account for the null byte
      linep = endnamep + 1;

      // save the directory index
      diridx = read_pointer ((const uint8_t **) &linep, enddirsecp, DW_EH_PE_leb128, user, compat_task);

      if (linep > enddirsecp)
        return;
      if (i == fileidx)
        break;

      filename_entry = NULL;

      // modification time
      read_pointer ((const uint8_t **) &linep, enddirsecp, DW_EH_PE_leb128, user, compat_task);
      // length of a file
      read_pointer ((const uint8_t **) &linep, enddirsecp, DW_EH_PE_leb128, user, compat_task);
      // check that nothing went wrong with reading the ulebs
      if (linep > enddirsecp)
        return;
    }

  if (filename_entry == NULL)
    return; // return just the linenumber

  // if  dirid == 0, it's the compilation directory. otherwise retrieve the
  // directory path if the file path was relative
  if (diridx != 0 && filename_entry[0] != '/')
    {
      linep = dirsecp;
      for (j = 1; *linep != 0 && linep < enddirsecp; j++)
        {
          uint8_t *endnamep = NULL;
          dirname_entry = (char *) linep;
          endnamep = (uint8_t *) memchr (dirname_entry, '\0', (size_t) (enddirsecp-linep));
          if (endnamep == NULL || (endnamep + 1) > enddirsecp)
            return;

          if (j == diridx)
            break;

          dirname_entry = NULL;
          linep = endnamep + 1;
        }

      if (dirname_entry == NULL)
        return;
    }

  // bring it all together
  // the filename was the full path
  if (filename_entry[0] == '/')
    *filename = filename_entry;
  // relative filename, and the dir corresponds to the compilation dir
  else if (diridx == 0)
    {
      char *slash = strrchr (mod->path, '/');
      strlcpy(fullpath, mod->path, (size_t) (2 + slash - mod->path));
      strlcat(fullpath, filename_entry, MAXSTRINGLEN);
      *filename = fullpath;
    }
  // relative filename and a directory from the table in the debug line data
  else
    {
      strlcpy(fullpath, dirname_entry, MAXSTRINGLEN);
      strlcat(fullpath, "/", MAXSTRINGLEN);
      strlcat(fullpath, filename_entry, MAXSTRINGLEN);
      *filename = fullpath;
    }
}

#endif /* STP_NEED_LINE_DATA */

unsigned long _stp_linenumber_lookup(unsigned long addr, struct task_struct *task, char ** filename, int need_filename)
{
  struct _stp_module *m;
  struct _stp_section *sec;
  const char *modname = NULL;
  uint8_t *linep, *enddatap;
  int compat_task = _stp_is_compat_task();
  int user = (task ? 1 : 0);

// the portion below is encased in this conditional because some of the functions
// and constants needed are encased in a similar condition
#ifdef STP_NEED_LINE_DATA
  if (addr == 0)
      return 0;

  if (task)
    {
	    unsigned long vm_start = 0;
	    unsigned long vm_end = 0;
#ifdef CONFIG_COMPAT
      /* Handle 32bit signed values in 64bit longs, chop off top bits. */
      if (test_tsk_thread_flag(task, TIF_32BIT))
        addr &= ((compat_ulong_t) ~0);
#endif
	    m = _stp_umod_lookup(addr, task, &modname, &vm_start, &vm_end);
    }
  else
    m = _stp_kmod_sec_lookup(addr, &sec);

  if (m == NULL || m->debug_line == NULL)
    return 0;

  // if addr is a kernel address, it will need to be adjusted
  if (!task)
    {
      int i;
      unsigned long offset = 0;
      // have to factor in the load_offset of (specifically) the .text section
      for (i=0; i<m->num_sections; i++)
        if (!strcmp(m->sections[i].name, ".text"))
          {
            offset = (m->sections[i].static_addr - m->sections[i].sec_load_offset);
            break;
          }

      if (addr < offset)
        return 0;
      addr = addr - offset;
    }


  linep = m->debug_line;
  enddatap = m->debug_line + m->debug_line_len;

  while (linep < enddatap)
    {
      // State machine "curr" values are updated directly.
      // A "row" is committed line data that we should compare against, only
      // updated for DW_LNS_copy, DW_LNE_end_sequence, and special opcodes.
      uint64_t curr_addr = 0, row_addr = 0;
      unsigned int curr_file_idx = 1, row_file_idx = 1;
      unsigned long curr_linenum = 1, row_linenum = 1;
      unsigned int row_end_sequence = 1;

      unsigned int length = 4;
      unsigned int skip_to_seq_end = 0, op_index = 0;
      uint64_t unit_length, hdr_length;
      uint8_t *endunitp, *endhdrp, *dirsecp, *stdopcode_lens_secp;
      uint16_t version;
      uint8_t opcode_base, line_range, min_instr_len = 0, max_ops = 1;
      int8_t line_base;

      unit_length = (uint64_t) read_pointer ((const uint8_t **) &linep, enddatap, DW_EH_PE_data4, user, compat_task);
      if (unit_length == 0xffffffff)
        {
          if (unlikely (linep + 8 > enddatap))
            return 0;
          unit_length = (uint64_t) read_pointer ((const uint8_t **) &linep, enddatap, DW_EH_PE_data8, user, compat_task);
          length = 8;
        }
      if (unit_length < (length + 2) || (linep + unit_length) > enddatap)
        return 0;

      endunitp = linep + unit_length;

      version = read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_data2, user, compat_task);

      if (length == 4)
        hdr_length = (uint64_t) read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_data4, user, compat_task);
      else
        hdr_length = (uint64_t) read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_data8, user, compat_task);

      if ((linep + hdr_length) > endunitp || hdr_length < (version >= 4 ? 6 : 5))
        return 0;

      endhdrp = linep + hdr_length;

      // minimum instruction length
      min_instr_len = *linep++;
      // max operations per instruction
      if (version >= 4)
        {
          max_ops = *linep++;
          if (max_ops == 0)
              return 0; // max operations per instruction is supposed to > 0;
        }
      // default value of the is_stmt register
      ++linep;
      // line base. this is a signed value.
      line_base = *linep++;
      // line range
      line_range = *linep++;
      if (line_range == 0)
        return 0;
      // opcode base
      opcode_base = *linep++;
      // opcodes
      stdopcode_lens_secp = linep - 1;
      // need this check if the header length check covers this region?
      if ((linep + opcode_base - 1) >= endhdrp)
        return 0;
      linep += opcode_base - 1;

      // at the directory table. don't need an other information from the header
      // in order to find the desired line number, so we will save a pointer to
      // this point and skip ahead to the end of the header. this portion of the
      // header will be visited again after a line number has been found if a
      // filename is needed.
      dirsecp = linep;
      linep = endhdrp;

      // iterating through the opcodes. will deal with three defined types of
      // opcode: special, extended and standard. there is also a portion at
      // the end of this loop that will deal with unknown (standard) opcodes.
      while (linep < endunitp)
        {
          uint8_t opcode = *linep++;
          long addr_adv = 0;
          unsigned int commit_row = 0;
          unsigned int end_sequence = 0;

          if (opcode >= opcode_base) // special opcode
            {
              // line range was checked before this point. this variable is not altered after it is initialized.
              curr_linenum += (line_base + ((opcode - opcode_base) % line_range));
              addr_adv = ((opcode - opcode_base) / line_range);
              commit_row = 1;
            }

          else if (opcode == 0) // extended opcode
            {
              int len;
              uint8_t subopcode;

              if (linep + 1 > endunitp)
                return 0;

              len = *linep++;
              if (linep + len > endunitp || len < 1)
                return 0;

              subopcode = *linep++; // the sub opcode
              switch (subopcode)
                {
                  case DW_LNE_end_sequence:
                    // NB: we don't clear "curr" values until after the row is compared.
                    op_index = 0;
                    skip_to_seq_end = 0;
                    end_sequence = 1;
                    commit_row = 1;
                    break;
                  case DW_LNE_set_address:
                    if ((len - 1) == 4) // account for the opcode (the -1)
                      curr_addr = (uint64_t) read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_data4, user, compat_task);
                    else if ((len - 1) == 8)
                      curr_addr = (uint64_t) read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_data8, user, compat_task);
                    else
                      return 0;

                    // if the set address is past the address we want, iterate
                    // to the end of the sequence without doing more address
                    // and linenumber calcs than necessary
                    if (curr_addr > addr)
                      skip_to_seq_end = 1;
                    op_index = 0;
                    break;
                  default: // advance the ptr by the specified amount
                    linep += len-1;
                    break;
                }
            }
          else if (opcode <= DW_LNS_set_isa) // known standard opcode
            {
              uint8_t *linep_before = linep;
              switch (opcode)
                {
                  case DW_LNS_copy:
                    commit_row = 1;
                    break;
                  case DW_LNS_advance_pc:
                    addr_adv = read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_leb128, user, compat_task);
                    break;
                  case DW_LNS_fixed_advance_pc:
                    addr_adv = read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_data2, user, compat_task);
                    if (linep_before == linep) // the read failed
                      return 0;
                    op_index = 0;
                    break;
                  case DW_LNS_advance_line:
                    curr_linenum += read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_leb128+DW_EH_PE_signed, user, compat_task);
                    break;
                  case DW_LNS_set_file:
                    curr_file_idx = read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_leb128, user, compat_task);
                    break;
                  case DW_LNS_set_column:
                    read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_leb128, user, compat_task);
                    break;
                  case DW_LNS_const_add_pc:
                    addr_adv = ((255 - opcode_base) / line_range);
                    break;
                  case DW_LNS_set_isa:
                    read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_leb128, user, compat_task);
                    break;
                }
                if (linep > endunitp) // reading in the leb128 failed
                  return 0;
            }
          else
            {
              int i;
              for (i=stdopcode_lens_secp[opcode]; i>0; --i)
                {
                  read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_leb128, user, compat_task);
                  if (linep > endunitp)
                    return 0;
                }
            }

          // don't worry about doing address advances since we are waiting
          // till we hit the end of the sequence or the end of the unit at which
          // point the address and linenumber will be reset
          if (skip_to_seq_end)
            continue;

          // calculate actual address advance
          if (addr_adv != 0 && opcode != DW_LNS_fixed_advance_pc)
            {
              addr_adv = min_instr_len * (op_index + addr_adv) / max_ops;
              op_index =  (op_index + addr_adv) % max_ops;
            }
          curr_addr += addr_adv;

          if (commit_row) {
            // compare the whole range from the prior committed row
            // (except an end_sequence can't be the base)
            if (row_end_sequence == 0 && row_addr <= addr && addr < curr_addr)
              {
                if (need_filename)
                  _stp_filename_lookup(m, filename, dirsecp, endhdrp,
                                       row_file_idx, user, compat_task);
                return row_linenum;
              }

            if (end_sequence) {
              curr_addr = 0;
              curr_file_idx = 1;
              curr_linenum = 1;
            }

            row_addr = curr_addr;
            row_file_idx = curr_file_idx;
            row_linenum = curr_linenum;
            row_end_sequence = end_sequence;
          }
        }
    }
#endif /* STP_NEED_LINE_DATA */

  // no linenumber was found otherwise this function would have returned before this point
  return 0;
}

static int _stp_build_id_check (struct _stp_module *m,
				unsigned long notes_addr,
				struct task_struct *tsk)
{
  int j;

  for (j = 0; j < m->build_id_len; j++) {
    /* Use set_fs / get_user to access conceivably invalid addresses.
     * If loc2c-runtime.h were more easily usable, a deref() loop
     * could do it too. */
    mm_segment_t oldfs = get_fs();
    int rc;
    unsigned char theory, practice = 0;

#ifdef STAPCONF_PROBE_KERNEL
    if (!tsk) {
      theory = m->build_id_bits[j];
      set_fs(KERNEL_DS);
      rc = probe_kernel_read(&practice, (void*)(notes_addr + j), 1);
    }
    else
#endif
    {
      theory = m->build_id_bits[j];
      set_fs (tsk ? USER_DS : KERNEL_DS);

      /*
       * Why check CONFIG_UTRACE here? If we're using real in-kernel
       * utrace, we can always just call get_user() (since we're
       * either reading kernel memory or tsk == current).
       *
       * Since we're only reading here, we can call
       * __access_process_vm_noflush(), which only calls things that
       * are exported.
       */
#ifdef CONFIG_UTRACE
      rc = get_user(practice, ((unsigned char*)(void*)(notes_addr + j)));
#else
      if (!tsk || tsk == current) {
	rc = get_user(practice, ((unsigned char*)(void*)(notes_addr + j)));
      }
      else {
	rc = (__access_process_vm_noflush(tsk, (notes_addr + j), &practice,
					  1, 0) != 1);
      }
#endif
    }
    set_fs(oldfs);

    if (rc || (theory != practice)) {
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,27)
      _stp_error ("Build-id mismatch [man error::buildid]: \"%s\" byte %d (0x%02x vs 0x%02x) address %#lx rc %d\n",
		  m->path, j, theory, practice, notes_addr, rc);
      return 1;
#else
      /* This branch is a surrogate for kernels affected by Fedora bug
       * #465873. */
      _stp_warn (KERN_WARNING
		 "Build-id mismatch [man error::buildid]: \"%s\" byte %d (0x%02x vs 0x%02x) rc %d\n",
		 m->path, j, theory, practice, rc);
#endif
      break;
    } /* end mismatch */
  } /* end per-byte check loop */
  return 0;
}


/* Validate all-modules + kernel based on build-id (if present).
*  The completed case is the following combination:
*	   Debuginfo 		 Module			         Kernel	
* 			   X				X
* 	has build-id/not	unloaded		      has build-id/not	
*				loaded && (has build-id/not)  
*
*  NB: build-id exists only if ld>=2.18 and kernel>= 2.6.23
*/
static int _stp_module_check(void)
{
  struct _stp_module *m = NULL;
  unsigned long notes_addr, base_addr;
  unsigned i,j;
  int rc = 0;

#ifdef STP_NO_BUILDID_CHECK
  return 0;
#endif

  for (i = 0; i < _stp_num_modules; i++)
    {
      m = _stp_modules[i];

      if (m->build_id_len > 0 && m->notes_sect != 0) {
          dbug_sym(1, "build-id validation [%s]\n", m->name); /* kernel only */

          /* skip userspace program */
          if (m->name[0] != '/') continue;

          /* notes end address */
          if (!strcmp(m->name, "kernel")) {
              notes_addr = _stp_kmodule_relocate("kernel",
                  "_stext", m->build_id_offset);
              base_addr = _stp_kmodule_relocate("kernel",
                  "_stext", 0);
          } else {
              notes_addr = m->notes_sect + m->build_id_offset;
              base_addr = m->notes_sect;
          }

          if (notes_addr <= base_addr) { /* shouldn't happen */
              _stp_warn ("build-id address %lx <= base %lx\n",
                  notes_addr, base_addr);
              continue;
          }

          rc |=  _stp_build_id_check (m, notes_addr, NULL);
      } /* end checking */
    } /* end loop */

  return rc;
}



/* Iterate over _stp_modules, looking for a kernel module of given
   name.  Run build-id checking for it.  Return 0 on ok. */
static int _stp_kmodule_check (const char *name)
{
  struct _stp_module *m = NULL;
  unsigned long notes_addr, base_addr;
  unsigned i,j;

#ifdef STP_NO_BUILDID_CHECK
  return 0;
#endif

  WARN_ON(!name || name[0]=='/'); // non-userspace only

  for (i = 0; i < _stp_num_modules; i++)
    {
      m = _stp_modules[i];

      /* PR16406 must be unique kernel module name (non-/-prefixed path) */
      if (strcmp (name, m->name)) continue;

      if (m->build_id_len > 0 && m->notes_sect != 0) {
          dbug_sym(1, "build-id validation [%s]\n", m->name);

          /* notes end address */
          notes_addr = m->notes_sect + m->build_id_offset;
          base_addr = m->notes_sect;

          if (notes_addr <= base_addr) { /* shouldn't happen */
              _stp_warn ("build-id address %lx < base %lx\n",
                  notes_addr, base_addr);
              continue;
          }
          return _stp_build_id_check (m, notes_addr, NULL);
      } /* end checking */
    } /* end loop */

  return 0; /* not found */
}



/* Validate user module based on build-id (if present) */
static int _stp_usermodule_check(struct task_struct *tsk, const char *path_name, unsigned long addr)
{
  struct _stp_module *m = NULL;
  unsigned long notes_addr;
  unsigned i, j;
  unsigned char practice_id_bits[MAXSTRINGLEN];
  unsigned long vm_end = 0;

#ifdef STP_NO_BUILDID_CHECK
  return 0;
#endif

  WARN_ON(!path_name || path_name[0]!='/'); // user-space only

  for (i = 0; i < _stp_num_modules; i++)
    {
      m = _stp_modules[i];

      /* PR16406 must be unique userspace name (/-prefixed path); it's also in m->name */
      if (strcmp(path_name, m->path) != 0) continue;

      if (m->build_id_len > 0) {
	int ret, build_id_len;

	notes_addr = addr + m->build_id_offset /* + m->module_base */;

        dbug_sym(1, "build-id validation [%d %s] address=%#lx build_id_offset=%#lx\n",
                 tsk->pid, m->path, addr, m->build_id_offset);

	if (notes_addr <= addr) {
	  _stp_warn ("build-id address %lx < base %lx\n", notes_addr, addr);
	  continue;
	}
	return _stp_build_id_check (m, notes_addr, tsk);
      }
    }

  return 0; /* not found */
}


/** Prints an address based on the _STP_SYM flags.
 * @param address The address to lookup.
 * @param task The address to lookup (if NULL lookup kernel/module address).
 * @note Symbolic lookups should not normally be done within
 * a probe because it is too time-consuming. Use at module exit time. */
static int _stp_snprint_addr(char *str, size_t len, unsigned long address,
			     int flags, struct task_struct *task)
{
  const char *modname = NULL;
  const char *name = NULL;
  char *filename = NULL;
  unsigned long offset = 0, size = 0, linenumber = 0;
  char *exstr, *poststr, *prestr;

  prestr = (flags & _STP_SYM_PRE_SPACE) ? " " : "";
  exstr = (((flags & _STP_SYM_INEXACT) && (flags & _STP_SYM_SYMBOL))
	   ? " (inexact)" : "");
  if (flags & _STP_SYM_POST_SPACE)
    poststr = " ";
  else if (flags & _STP_SYM_NEWLINE)
    poststr = "\n";
  else
    poststr = "";

  if (flags & (_STP_SYM_SYMBOL | _STP_SYM_MODULE)) {
    name = _stp_kallsyms_lookup(address, &size, &offset, &modname, task);
    if (name && name[0] == '.')
      name++;
  }

  if (modname && (flags & _STP_SYM_MODULE_BASENAME)) {
     char *slash = strrchr (modname, '/');
     if (slash)
        modname = slash+1;
  }

  if ((flags & _STP_SYM_LINENUMBER) || (flags & _STP_SYM_FILENAME)) {
      linenumber = _stp_linenumber_lookup (address, task, &filename,
                                           (int) (flags & _STP_SYM_FILENAME));
  }

  if (name && (flags & _STP_SYM_SYMBOL)) {
    if ((flags & _STP_SYM_MODULE) && modname && *modname) {
      if (flags & _STP_SYM_OFFSET) {
	if (flags & _STP_SYM_SIZE) {
	  /* symbol, module, offset and size. */
	  if (flags & _STP_SYM_HEX_SYMBOL)
	    return _stp_snprintf(str, len, "%s%p : %s+%#lx/%#lx [%s]%s%s",
				 prestr, (int64_t) address,
				 name, offset, size, modname,
				 exstr, poststr);
	  else
	    return _stp_snprintf(str, len, "%s%s+%#lx/%#lx [%s]%s%s",
				 prestr, name, offset, size,
				 modname, exstr, poststr);
	} else {
	  /* symbol, module, offset. */
	  if (flags & _STP_SYM_HEX_SYMBOL)
	    return _stp_snprintf(str, len, "%s%p : %s+%#lx [%s]%s%s",
				 prestr, (int64_t) address,
				 name, offset, modname,
				 exstr, poststr);
	  else
	    return _stp_snprintf(str, len, "%s%s+%#lx [%s]%s%s",
				 prestr, name, offset,
				 modname, exstr, poststr);
	}
      } else {
	/* symbol plus module */
	if (flags & _STP_SYM_HEX_SYMBOL)
	  return _stp_snprintf(str, len, "%s%p : %s [%s]%s%s", prestr,
			       (int64_t) address, name, modname,
			       exstr, poststr);
	else
	  return _stp_snprintf(str, len, "%s%s [%s]%s%s", prestr, name,
			       modname, exstr, poststr);
      }
    } else if (flags & _STP_SYM_OFFSET) {
      if (flags & _STP_SYM_SIZE) {
	/* symbol name, offset + size, no module name */
	if (flags & _STP_SYM_HEX_SYMBOL)
	  return _stp_snprintf(str, len, "%s%p : %s+%#lx/%#lx%s%s", prestr,
			       (int64_t) address, name, offset,
			       size, exstr, poststr);
	else
	  return _stp_snprintf(str, len, "%s%s+%#lx/%#lx%s%s", prestr, name,
			       offset, size, exstr, poststr);
      } else {
	/* symbol name, offset, no module name */
	if (flags & _STP_SYM_HEX_SYMBOL)
	  return _stp_snprintf(str, len, "%s%p : %s+%#lx%s%s", prestr,
			       (int64_t) address, name, offset,
			       exstr, poststr);
	else
	  return _stp_snprintf(str, len, "%s%s+%#lx%s%s", prestr, name,
			       offset, exstr, poststr);
      }
    } else {
      /* symbol name only */
      if (flags & _STP_SYM_HEX_SYMBOL)
	return _stp_snprintf(str, len, "%s%p : %s%s%s", prestr,
			     (int64_t) address, name, exstr, poststr);
      else
	return _stp_snprintf(str, len, "%s%s%s%s", prestr, name,
			     exstr, poststr);
    }
  } else {
    /* no symbol name */
    if (modname && *modname && (flags & _STP_SYM_MODULE)) {
      if (flags & _STP_SYM_OFFSET) {
        if (flags & _STP_SYM_SIZE) {
          /* hex address, module name, offset + size */
          return _stp_snprintf(str, len, "%s%p [%s+%#lx/%#lx]%s%s", prestr,
			       (int64_t) address, modname, offset,
			       size, exstr, poststr);
        } else {
          /* hex address, module name, offset */
	  return _stp_snprintf(str, len, "%s%p [%s+%#lx]%s%s", prestr,
			       (int64_t) address, modname, offset,
			       exstr, poststr);
        }
      } else {
	/* hex address, module name */
        return _stp_snprintf(str, len, "%s%p [%s]%s%s", prestr,
			     (int64_t) address, modname, exstr, poststr);
      }
#ifdef STAPCONF_MODULE_TEXT_ADDRESS
    } if ((flags & _STP_SYM_MODULE) && ! task) {
      /* No symbol, nor module name, but user really wants one, do one
	 last try. */
      struct module *ko;
      preempt_disable();
      ko = __module_text_address (address);
      if (ko && ko->name)
	{
	  /* hex address, module name */
	  int ret = _stp_snprintf(str, len, "%s%p [%s]%s%s", prestr,
				  (int64_t) address, ko->name, exstr, poststr);
	  preempt_enable_no_resched();
	  return ret;
        }
      preempt_enable_no_resched();
      /* no names, hex only */
      return _stp_snprintf(str, len, "%s%p%s%s", prestr,
			   (int64_t) address, exstr, poststr);
#endif
    } else if ((flags & _STP_SYM_LINENUMBER) && linenumber) {
        if (flags & _STP_SYM_FILENAME) {
          if (filename) {
            /* filename, linenumber */
            return _stp_snprintf(str, len, "%s%s:%#lu%s%s", prestr,
                 filename,  linenumber, exstr, poststr);
          } else {
            /* filename=??, linenumber */
            return _stp_snprintf(str, len, "%s??:%#lu%s%s", prestr,
                 linenumber, exstr, poststr);
          }
        } else {
          /* linenumber */
          return _stp_snprintf(str, len, "%s%#lu%s%s", prestr,
               linenumber, exstr, poststr);
        }
    } else if ((flags & _STP_SYM_FILENAME) && filename) {
      /* filename */
      return _stp_snprintf(str, len, "%s%s%s%s", prestr,
           filename, exstr, poststr);
    }else {
      /* no names, hex only */
      return _stp_snprintf(str, len, "%s%p%s%s", prestr,
			   (int64_t) address, exstr, poststr);
    }
  }
}

static void _stp_print_addr(unsigned long address, int flags,
			    struct task_struct *task)
{
  _stp_snprint_addr(NULL, 0, address, flags, task);
}

/** @} */



/* Update the given module/section's offset value.  Assume that there
   is no need for locking or for super performance.  NB: this is only
   for kernel modules, which exist singly at run time.  User-space
   modules (executables, shared libraries) exist at different
   addresses in different processes, so are tracked in the
   _stp_tf_vma_map. */
static void _stp_kmodule_update_address(const char* module,
                                        const char* reloc, /* NULL="all" */
                                        unsigned long address)
{
  unsigned mi, si;
  for (mi=0; mi<_stp_num_modules; mi++)
    {
      const char *note_sectname = ".note.gnu.build-id";
      if (strcmp (_stp_modules[mi]->name, module))
        continue;

      if (reloc && !strcmp (note_sectname, reloc)) {
        dbug_sym(1, "module %s special section %s address %#lx\n",
                 _stp_modules[mi]->name,
                 note_sectname,
                 address);
        _stp_modules[mi]->notes_sect = address;   /* cache this particular address  */
      }

      for (si=0; si<_stp_modules[mi]->num_sections; si++)
        {
          if (reloc && strcmp (_stp_modules[mi]->sections[si].name, reloc))
            continue;
          else
            {
              dbug_sym(1, "module %s section %s address %#lx\n",
                       _stp_modules[mi]->name,
                       _stp_modules[mi]->sections[si].name,
                       address);
              _stp_modules[mi]->sections[si].static_addr = address;

              if (reloc) break;
              else continue; /* wildcarded - will have more hits */
            }
        } /* loop over sections */
    } /* loop over modules */
}


#ifndef STAPCONF_KALLSYMS
unsigned long kallsyms_lookup_name (const char *name)
{
        /* NB: PR14804: don't use _stp_error here.  It's called too
           early for the actual message buffer goo to be allocated. */
        /* Don't even printk.  A user can't do anything about it. */
        /* printk (KERN_ERR "kallsyms_lookup_name unavailable for %s\n", name); */
        return 0;
}
#endif



#endif /* _STP_SYM_C_ */