summaryrefslogtreecommitdiff
path: root/gdb/solib-svr4.c
blob: bae72006675f79dd0f210c9a676d0f8165a275ae (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
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
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
/* Handle SVR4 shared libraries for GDB, the GNU Debugger.

   Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000,
   2001, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
   Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"

#include "elf/external.h"
#include "elf/common.h"
#include "elf/mips.h"

#include "symtab.h"
#include "bfd.h"
#include "symfile.h"
#include "objfiles.h"
#include "gdbcore.h"
#include "target.h"
#include "inferior.h"
#include "regcache.h"
#include "gdbthread.h"
#include "observer.h"

#include "gdb_assert.h"

#include "solist.h"
#include "solib.h"
#include "solib-svr4.h"

#include "bfd-target.h"
#include "elf-bfd.h"
#include "exec.h"
#include "auxv.h"
#include "exceptions.h"

static struct link_map_offsets *svr4_fetch_link_map_offsets (void);
static int svr4_have_link_map_offsets (void);
static void svr4_relocate_main_executable (void);

/* Link map info to include in an allocated so_list entry */

struct lm_info
  {
    /* Pointer to copy of link map from inferior.  The type is char *
       rather than void *, so that we may use byte offsets to find the
       various fields without the need for a cast.  */
    gdb_byte *lm;

    /* Amount by which addresses in the binary should be relocated to
       match the inferior.  This could most often be taken directly
       from lm, but when prelinking is involved and the prelink base
       address changes, we may need a different offset, we want to
       warn about the difference and compute it only once.  */
    CORE_ADDR l_addr;

    /* The target location of lm.  */
    CORE_ADDR lm_addr;
  };

/* On SVR4 systems, a list of symbols in the dynamic linker where
   GDB can try to place a breakpoint to monitor shared library
   events.

   If none of these symbols are found, or other errors occur, then
   SVR4 systems will fall back to using a symbol as the "startup
   mapping complete" breakpoint address.  */

static char *solib_break_names[] =
{
  "r_debug_state",
  "_r_debug_state",
  "_dl_debug_state",
  "rtld_db_dlactivity",
  "__dl_rtld_db_dlactivity",
  "_rtld_debug_state",

  NULL
};

static char *bkpt_names[] =
{
  "_start",
  "__start",
  "main",
  NULL
};

static char *main_name_list[] =
{
  "main_$main",
  NULL
};

/* Return non-zero if GDB_SO_NAME and INFERIOR_SO_NAME represent
   the same shared library.  */

static int
svr4_same_1 (const char *gdb_so_name, const char *inferior_so_name)
{
  if (strcmp (gdb_so_name, inferior_so_name) == 0)
    return 1;

  /* On Solaris, when starting inferior we think that dynamic linker is
     /usr/lib/ld.so.1, but later on, the table of loaded shared libraries 
     contains /lib/ld.so.1.  Sometimes one file is a link to another, but 
     sometimes they have identical content, but are not linked to each
     other.  We don't restrict this check for Solaris, but the chances
     of running into this situation elsewhere are very low.  */
  if (strcmp (gdb_so_name, "/usr/lib/ld.so.1") == 0
      && strcmp (inferior_so_name, "/lib/ld.so.1") == 0)
    return 1;

  /* Similarly, we observed the same issue with sparc64, but with
     different locations.  */
  if (strcmp (gdb_so_name, "/usr/lib/sparcv9/ld.so.1") == 0
      && strcmp (inferior_so_name, "/lib/sparcv9/ld.so.1") == 0)
    return 1;

  return 0;
}

static int
svr4_same (struct so_list *gdb, struct so_list *inferior)
{
  return (svr4_same_1 (gdb->so_original_name, inferior->so_original_name));
}

/* link map access functions */

static CORE_ADDR
LM_ADDR_FROM_LINK_MAP (struct so_list *so)
{
  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
  struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;

  return extract_typed_address (so->lm_info->lm + lmo->l_addr_offset,
				ptr_type);
}

static int
HAS_LM_DYNAMIC_FROM_LINK_MAP (void)
{
  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();

  return lmo->l_ld_offset >= 0;
}

static CORE_ADDR
LM_DYNAMIC_FROM_LINK_MAP (struct so_list *so)
{
  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
  struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;

  return extract_typed_address (so->lm_info->lm + lmo->l_ld_offset,
				ptr_type);
}

static CORE_ADDR
LM_ADDR_CHECK (struct so_list *so, bfd *abfd)
{
  if (so->lm_info->l_addr == (CORE_ADDR)-1)
    {
      struct bfd_section *dyninfo_sect;
      CORE_ADDR l_addr, l_dynaddr, dynaddr;

      l_addr = LM_ADDR_FROM_LINK_MAP (so);

      if (! abfd || ! HAS_LM_DYNAMIC_FROM_LINK_MAP ())
	goto set_addr;

      l_dynaddr = LM_DYNAMIC_FROM_LINK_MAP (so);

      dyninfo_sect = bfd_get_section_by_name (abfd, ".dynamic");
      if (dyninfo_sect == NULL)
	goto set_addr;

      dynaddr = bfd_section_vma (abfd, dyninfo_sect);

      if (dynaddr + l_addr != l_dynaddr)
	{
	  CORE_ADDR align = 0x1000;
	  CORE_ADDR minpagesize = align;

	  if (bfd_get_flavour (abfd) == bfd_target_elf_flavour)
	    {
	      Elf_Internal_Ehdr *ehdr = elf_tdata (abfd)->elf_header;
	      Elf_Internal_Phdr *phdr = elf_tdata (abfd)->phdr;
	      int i;

	      align = 1;

	      for (i = 0; i < ehdr->e_phnum; i++)
		if (phdr[i].p_type == PT_LOAD && phdr[i].p_align > align)
		  align = phdr[i].p_align;

	      minpagesize = get_elf_backend_data (abfd)->minpagesize;
	    }

	  /* Turn it into a mask.  */
	  align--;

	  /* If the changes match the alignment requirements, we
	     assume we're using a core file that was generated by the
	     same binary, just prelinked with a different base offset.
	     If it doesn't match, we may have a different binary, the
	     same binary with the dynamic table loaded at an unrelated
	     location, or anything, really.  To avoid regressions,
	     don't adjust the base offset in the latter case, although
	     odds are that, if things really changed, debugging won't
	     quite work.

	     One could expect more the condition
	       ((l_addr & align) == 0 && ((l_dynaddr - dynaddr) & align) == 0)
	     but the one below is relaxed for PPC.  The PPC kernel supports
	     either 4k or 64k page sizes.  To be prepared for 64k pages,
	     PPC ELF files are built using an alignment requirement of 64k.
	     However, when running on a kernel supporting 4k pages, the memory
	     mapping of the library may not actually happen on a 64k boundary!

	     (In the usual case where (l_addr & align) == 0, this check is
	     equivalent to the possibly expected check above.)

	     Even on PPC it must be zero-aligned at least for MINPAGESIZE.  */

	  if ((l_addr & (minpagesize - 1)) == 0
	      && (l_addr & align) == ((l_dynaddr - dynaddr) & align))
	    {
	      l_addr = l_dynaddr - dynaddr;

	      if (info_verbose)
		printf_unfiltered (_("Using PIC (Position Independent Code) "
				     "prelink displacement %s for \"%s\".\n"),
				   paddress (target_gdbarch, l_addr),
				   so->so_name);
	    }
	  else
	    warning (_(".dynamic section for \"%s\" "
		       "is not at the expected address "
		       "(wrong library or version mismatch?)"), so->so_name);
	}

    set_addr:
      so->lm_info->l_addr = l_addr;
    }

  return so->lm_info->l_addr;
}

static CORE_ADDR
LM_NEXT (struct so_list *so)
{
  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
  struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;

  return extract_typed_address (so->lm_info->lm + lmo->l_next_offset,
				ptr_type);
}

static CORE_ADDR
LM_NAME (struct so_list *so)
{
  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
  struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;

  return extract_typed_address (so->lm_info->lm + lmo->l_name_offset,
				ptr_type);
}

static int
IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list *so)
{
  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
  struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;

  /* Assume that everything is a library if the dynamic loader was loaded
     late by a static executable.  */
  if (exec_bfd && bfd_get_section_by_name (exec_bfd, ".dynamic") == NULL)
    return 0;

  return extract_typed_address (so->lm_info->lm + lmo->l_prev_offset,
				ptr_type) == 0;
}

/* Per pspace SVR4 specific data.  */

struct svr4_info
{
  CORE_ADDR debug_base;	/* Base of dynamic linker structures */

  /* Validity flag for debug_loader_offset.  */
  int debug_loader_offset_p;

  /* Load address for the dynamic linker, inferred.  */
  CORE_ADDR debug_loader_offset;

  /* Name of the dynamic linker, valid if debug_loader_offset_p.  */
  char *debug_loader_name;

  /* Load map address for the main executable.  */
  CORE_ADDR main_lm_addr;

  CORE_ADDR interp_text_sect_low;
  CORE_ADDR interp_text_sect_high;
  CORE_ADDR interp_plt_sect_low;
  CORE_ADDR interp_plt_sect_high;
};

/* Per-program-space data key.  */
static const struct program_space_data *solib_svr4_pspace_data;

static void
svr4_pspace_data_cleanup (struct program_space *pspace, void *arg)
{
  struct svr4_info *info;

  info = program_space_data (pspace, solib_svr4_pspace_data);
  xfree (info);
}

/* Get the current svr4 data.  If none is found yet, add it now.  This
   function always returns a valid object.  */

static struct svr4_info *
get_svr4_info (void)
{
  struct svr4_info *info;

  info = program_space_data (current_program_space, solib_svr4_pspace_data);
  if (info != NULL)
    return info;

  info = XZALLOC (struct svr4_info);
  set_program_space_data (current_program_space, solib_svr4_pspace_data, info);
  return info;
}

/* Local function prototypes */

static int match_main (char *);

static CORE_ADDR bfd_lookup_symbol (bfd *, char *);

/*

   LOCAL FUNCTION

   bfd_lookup_symbol -- lookup the value for a specific symbol

   SYNOPSIS

   CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname)

   DESCRIPTION

   An expensive way to lookup the value of a single symbol for
   bfd's that are only temporary anyway.  This is used by the
   shared library support to find the address of the debugger
   notification routine in the shared library.

   The returned symbol may be in a code or data section; functions
   will normally be in a code section, but may be in a data section
   if this architecture uses function descriptors.

   Note that 0 is specifically allowed as an error return (no
   such symbol).
 */

static CORE_ADDR
bfd_lookup_symbol (bfd *abfd, char *symname)
{
  long storage_needed;
  asymbol *sym;
  asymbol **symbol_table;
  unsigned int number_of_symbols;
  unsigned int i;
  struct cleanup *back_to;
  CORE_ADDR symaddr = 0;

  storage_needed = bfd_get_symtab_upper_bound (abfd);

  if (storage_needed > 0)
    {
      symbol_table = (asymbol **) xmalloc (storage_needed);
      back_to = make_cleanup (xfree, symbol_table);
      number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);

      for (i = 0; i < number_of_symbols; i++)
	{
	  sym = *symbol_table++;
	  if (strcmp (sym->name, symname) == 0
              && (sym->section->flags & (SEC_CODE | SEC_DATA)) != 0)
	    {
	      /* BFD symbols are section relative.  */
	      symaddr = sym->value + sym->section->vma;
	      break;
	    }
	}
      do_cleanups (back_to);
    }

  if (symaddr)
    return symaddr;

  /* On FreeBSD, the dynamic linker is stripped by default.  So we'll
     have to check the dynamic string table too.  */

  storage_needed = bfd_get_dynamic_symtab_upper_bound (abfd);

  if (storage_needed > 0)
    {
      symbol_table = (asymbol **) xmalloc (storage_needed);
      back_to = make_cleanup (xfree, symbol_table);
      number_of_symbols = bfd_canonicalize_dynamic_symtab (abfd, symbol_table);

      for (i = 0; i < number_of_symbols; i++)
	{
	  sym = *symbol_table++;

	  if (strcmp (sym->name, symname) == 0
              && (sym->section->flags & (SEC_CODE | SEC_DATA)) != 0)
	    {
	      /* BFD symbols are section relative.  */
	      symaddr = sym->value + sym->section->vma;
	      break;
	    }
	}
      do_cleanups (back_to);
    }

  return symaddr;
}


/* Read program header TYPE from inferior memory.  The header is found
   by scanning the OS auxillary vector.

   If TYPE == -1, return the program headers instead of the contents of
   one program header.

   Return a pointer to allocated memory holding the program header contents,
   or NULL on failure.  If sucessful, and unless P_SECT_SIZE is NULL, the
   size of those contents is returned to P_SECT_SIZE.  Likewise, the target
   architecture size (32-bit or 64-bit) is returned to P_ARCH_SIZE.  */

static gdb_byte *
read_program_header (int type, int *p_sect_size, int *p_arch_size)
{
  enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
  CORE_ADDR at_phdr, at_phent, at_phnum;
  int arch_size, sect_size;
  CORE_ADDR sect_addr;
  gdb_byte *buf;

  /* Get required auxv elements from target.  */
  if (target_auxv_search (&current_target, AT_PHDR, &at_phdr) <= 0)
    return 0;
  if (target_auxv_search (&current_target, AT_PHENT, &at_phent) <= 0)
    return 0;
  if (target_auxv_search (&current_target, AT_PHNUM, &at_phnum) <= 0)
    return 0;
  if (!at_phdr || !at_phnum)
    return 0;

  /* Determine ELF architecture type.  */
  if (at_phent == sizeof (Elf32_External_Phdr))
    arch_size = 32;
  else if (at_phent == sizeof (Elf64_External_Phdr))
    arch_size = 64;
  else
    return 0;

  /* Find the requested segment.  */
  if (type == -1)
    {
      sect_addr = at_phdr;
      sect_size = at_phent * at_phnum;
    }
  else if (arch_size == 32)
    {
      Elf32_External_Phdr phdr;
      int i;

      /* Search for requested PHDR.  */
      for (i = 0; i < at_phnum; i++)
	{
	  if (target_read_memory (at_phdr + i * sizeof (phdr),
				  (gdb_byte *)&phdr, sizeof (phdr)))
	    return 0;

	  if (extract_unsigned_integer ((gdb_byte *)phdr.p_type,
					4, byte_order) == type)
	    break;
	}

      if (i == at_phnum)
	return 0;

      /* Retrieve address and size.  */
      sect_addr = extract_unsigned_integer ((gdb_byte *)phdr.p_vaddr,
					    4, byte_order);
      sect_size = extract_unsigned_integer ((gdb_byte *)phdr.p_memsz,
					    4, byte_order);
    }
  else
    {
      Elf64_External_Phdr phdr;
      int i;

      /* Search for requested PHDR.  */
      for (i = 0; i < at_phnum; i++)
	{
	  if (target_read_memory (at_phdr + i * sizeof (phdr),
				  (gdb_byte *)&phdr, sizeof (phdr)))
	    return 0;

	  if (extract_unsigned_integer ((gdb_byte *)phdr.p_type,
					4, byte_order) == type)
	    break;
	}

      if (i == at_phnum)
	return 0;

      /* Retrieve address and size.  */
      sect_addr = extract_unsigned_integer ((gdb_byte *)phdr.p_vaddr,
					    8, byte_order);
      sect_size = extract_unsigned_integer ((gdb_byte *)phdr.p_memsz,
					    8, byte_order);
    }

  /* Read in requested program header.  */
  buf = xmalloc (sect_size);
  if (target_read_memory (sect_addr, buf, sect_size))
    {
      xfree (buf);
      return NULL;
    }

  if (p_arch_size)
    *p_arch_size = arch_size;
  if (p_sect_size)
    *p_sect_size = sect_size;

  return buf;
}


/* Return program interpreter string.  */
static gdb_byte *
find_program_interpreter (void)
{
  gdb_byte *buf = NULL;

  /* If we have an exec_bfd, use its section table.  */
  if (exec_bfd
      && bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
   {
     struct bfd_section *interp_sect;

     interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
     if (interp_sect != NULL)
      {
	CORE_ADDR sect_addr = bfd_section_vma (exec_bfd, interp_sect);
	int sect_size = bfd_section_size (exec_bfd, interp_sect);

	buf = xmalloc (sect_size);
	bfd_get_section_contents (exec_bfd, interp_sect, buf, 0, sect_size);
      }
   }

  /* If we didn't find it, use the target auxillary vector.  */
  if (!buf)
    buf = read_program_header (PT_INTERP, NULL, NULL);

  return buf;
}


/* Scan for DYNTAG in .dynamic section of ABFD. If DYNTAG is found 1 is
   returned and the corresponding PTR is set.  */

static int
scan_dyntag (int dyntag, bfd *abfd, CORE_ADDR *ptr)
{
  int arch_size, step, sect_size;
  long dyn_tag;
  CORE_ADDR dyn_ptr, dyn_addr;
  gdb_byte *bufend, *bufstart, *buf;
  Elf32_External_Dyn *x_dynp_32;
  Elf64_External_Dyn *x_dynp_64;
  struct bfd_section *sect;
  struct target_section *target_section;

  if (abfd == NULL)
    return 0;

  if (bfd_get_flavour (abfd) != bfd_target_elf_flavour)
    return 0;

  arch_size = bfd_get_arch_size (abfd);
  if (arch_size == -1)
    return 0;

  /* Find the start address of the .dynamic section.  */
  sect = bfd_get_section_by_name (abfd, ".dynamic");
  if (sect == NULL)
    return 0;

  for (target_section = current_target_sections->sections;
       target_section < current_target_sections->sections_end;
       target_section++)
    if (sect == target_section->the_bfd_section)
      break;
  if (target_section < current_target_sections->sections_end)
    dyn_addr = target_section->addr;
  else
    {
      /* ABFD may come from OBJFILE acting only as a symbol file without being
	 loaded into the target (see add_symbol_file_command).  This case is
	 such fallback to the file VMA address without the possibility of
	 having the section relocated to its actual in-memory address.  */

      dyn_addr = bfd_section_vma (abfd, sect);
    }

  /* Read in .dynamic from the BFD.  We will get the actual value
     from memory later.  */
  sect_size = bfd_section_size (abfd, sect);
  buf = bufstart = alloca (sect_size);
  if (!bfd_get_section_contents (abfd, sect,
				 buf, 0, sect_size))
    return 0;

  /* Iterate over BUF and scan for DYNTAG.  If found, set PTR and return.  */
  step = (arch_size == 32) ? sizeof (Elf32_External_Dyn)
			   : sizeof (Elf64_External_Dyn);
  for (bufend = buf + sect_size;
       buf < bufend;
       buf += step)
  {
    if (arch_size == 32)
      {
	x_dynp_32 = (Elf32_External_Dyn *) buf;
	dyn_tag = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp_32->d_tag);
	dyn_ptr = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp_32->d_un.d_ptr);
      }
    else
      {
	x_dynp_64 = (Elf64_External_Dyn *) buf;
	dyn_tag = bfd_h_get_64 (abfd, (bfd_byte *) x_dynp_64->d_tag);
	dyn_ptr = bfd_h_get_64 (abfd, (bfd_byte *) x_dynp_64->d_un.d_ptr);
      }
     if (dyn_tag == DT_NULL)
       return 0;
     if (dyn_tag == dyntag)
       {
	 /* If requested, try to read the runtime value of this .dynamic
	    entry.  */
	 if (ptr)
	   {
	     struct type *ptr_type;
	     gdb_byte ptr_buf[8];
	     CORE_ADDR ptr_addr;

	     ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
	     ptr_addr = dyn_addr + (buf - bufstart) + arch_size / 8;
	     if (target_read_memory (ptr_addr, ptr_buf, arch_size / 8) == 0)
	       dyn_ptr = extract_typed_address (ptr_buf, ptr_type);
	     *ptr = dyn_ptr;
	   }
	 return 1;
       }
  }

  return 0;
}

/* Scan for DYNTAG in .dynamic section of the target's main executable,
   found by consulting the OS auxillary vector.  If DYNTAG is found 1 is
   returned and the corresponding PTR is set.  */

static int
scan_dyntag_auxv (int dyntag, CORE_ADDR *ptr)
{
  enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
  int sect_size, arch_size, step;
  long dyn_tag;
  CORE_ADDR dyn_ptr;
  gdb_byte *bufend, *bufstart, *buf;

  /* Read in .dynamic section.  */
  buf = bufstart = read_program_header (PT_DYNAMIC, &sect_size, &arch_size);
  if (!buf)
    return 0;

  /* Iterate over BUF and scan for DYNTAG.  If found, set PTR and return.  */
  step = (arch_size == 32) ? sizeof (Elf32_External_Dyn)
			   : sizeof (Elf64_External_Dyn);
  for (bufend = buf + sect_size;
       buf < bufend;
       buf += step)
  {
    if (arch_size == 32)
      {
	Elf32_External_Dyn *dynp = (Elf32_External_Dyn *) buf;
	dyn_tag = extract_unsigned_integer ((gdb_byte *) dynp->d_tag,
					    4, byte_order);
	dyn_ptr = extract_unsigned_integer ((gdb_byte *) dynp->d_un.d_ptr,
					    4, byte_order);
      }
    else
      {
	Elf64_External_Dyn *dynp = (Elf64_External_Dyn *) buf;
	dyn_tag = extract_unsigned_integer ((gdb_byte *) dynp->d_tag,
					    8, byte_order);
	dyn_ptr = extract_unsigned_integer ((gdb_byte *) dynp->d_un.d_ptr,
					    8, byte_order);
      }
    if (dyn_tag == DT_NULL)
      break;

    if (dyn_tag == dyntag)
      {
	if (ptr)
	  *ptr = dyn_ptr;

	xfree (bufstart);
	return 1;
      }
  }

  xfree (bufstart);
  return 0;
}


/*

   LOCAL FUNCTION

   elf_locate_base -- locate the base address of dynamic linker structs
   for SVR4 elf targets.

   SYNOPSIS

   CORE_ADDR elf_locate_base (void)

   DESCRIPTION

   For SVR4 elf targets the address of the dynamic linker's runtime
   structure is contained within the dynamic info section in the
   executable file.  The dynamic section is also mapped into the
   inferior address space.  Because the runtime loader fills in the
   real address before starting the inferior, we have to read in the
   dynamic info section from the inferior address space.
   If there are any errors while trying to find the address, we
   silently return 0, otherwise the found address is returned.

 */

static CORE_ADDR
elf_locate_base (void)
{
  struct minimal_symbol *msymbol;
  CORE_ADDR dyn_ptr;

  /* Look for DT_MIPS_RLD_MAP first.  MIPS executables use this
     instead of DT_DEBUG, although they sometimes contain an unused
     DT_DEBUG.  */
  if (scan_dyntag (DT_MIPS_RLD_MAP, exec_bfd, &dyn_ptr)
      || scan_dyntag_auxv (DT_MIPS_RLD_MAP, &dyn_ptr))
    {
      struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
      gdb_byte *pbuf;
      int pbuf_size = TYPE_LENGTH (ptr_type);
      pbuf = alloca (pbuf_size);
      /* DT_MIPS_RLD_MAP contains a pointer to the address
	 of the dynamic link structure.  */
      if (target_read_memory (dyn_ptr, pbuf, pbuf_size))
	return 0;
      return extract_typed_address (pbuf, ptr_type);
    }

  /* Find DT_DEBUG.  */
  if (scan_dyntag (DT_DEBUG, exec_bfd, &dyn_ptr)
      || scan_dyntag_auxv (DT_DEBUG, &dyn_ptr))
    return dyn_ptr;

  /* This may be a static executable.  Look for the symbol
     conventionally named _r_debug, as a last resort.  */
  msymbol = lookup_minimal_symbol ("_r_debug", NULL, symfile_objfile);
  if (msymbol != NULL)
    return SYMBOL_VALUE_ADDRESS (msymbol);

  /* DT_DEBUG entry not found.  */
  return 0;
}

/*

   LOCAL FUNCTION

   locate_base -- locate the base address of dynamic linker structs

   SYNOPSIS

   CORE_ADDR locate_base (struct svr4_info *)

   DESCRIPTION

   For both the SunOS and SVR4 shared library implementations, if the
   inferior executable has been linked dynamically, there is a single
   address somewhere in the inferior's data space which is the key to
   locating all of the dynamic linker's runtime structures.  This
   address is the value of the debug base symbol.  The job of this
   function is to find and return that address, or to return 0 if there
   is no such address (the executable is statically linked for example).

   For SunOS, the job is almost trivial, since the dynamic linker and
   all of it's structures are statically linked to the executable at
   link time.  Thus the symbol for the address we are looking for has
   already been added to the minimal symbol table for the executable's
   objfile at the time the symbol file's symbols were read, and all we
   have to do is look it up there.  Note that we explicitly do NOT want
   to find the copies in the shared library.

   The SVR4 version is a bit more complicated because the address
   is contained somewhere in the dynamic info section.  We have to go
   to a lot more work to discover the address of the debug base symbol.
   Because of this complexity, we cache the value we find and return that
   value on subsequent invocations.  Note there is no copy in the
   executable symbol tables.

 */

static CORE_ADDR
locate_base (struct svr4_info *info)
{
  /* Check to see if we have a currently valid address, and if so, avoid
     doing all this work again and just return the cached address.  If
     we have no cached address, try to locate it in the dynamic info
     section for ELF executables.  There's no point in doing any of this
     though if we don't have some link map offsets to work with.  */

  if (info->debug_base == 0 && svr4_have_link_map_offsets ())
    info->debug_base = elf_locate_base ();
  return info->debug_base;
}

/* Find the first element in the inferior's dynamic link map, and
   return its address in the inferior.

   FIXME: Perhaps we should validate the info somehow, perhaps by
   checking r_version for a known version number, or r_state for
   RT_CONSISTENT.  */

static CORE_ADDR
solib_svr4_r_map (struct svr4_info *info)
{
  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
  struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
  CORE_ADDR addr = 0;
  volatile struct gdb_exception ex;

  TRY_CATCH (ex, RETURN_MASK_ERROR)
    {
      addr = read_memory_typed_address (info->debug_base + lmo->r_map_offset,
                                        ptr_type);
    }
  exception_print (gdb_stderr, ex);
  return addr;
}

/* Find r_brk from the inferior's debug base.  */

static CORE_ADDR
solib_svr4_r_brk (struct svr4_info *info)
{
  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
  struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;

  return read_memory_typed_address (info->debug_base + lmo->r_brk_offset,
				    ptr_type);
}

/* Find the link map for the dynamic linker (if it is not in the
   normal list of loaded shared objects).  */

static CORE_ADDR
solib_svr4_r_ldsomap (struct svr4_info *info)
{
  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
  struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
  enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
  ULONGEST version;

  /* Check version, and return zero if `struct r_debug' doesn't have
     the r_ldsomap member.  */
  version
    = read_memory_unsigned_integer (info->debug_base + lmo->r_version_offset,
				    lmo->r_version_size, byte_order);
  if (version < 2 || lmo->r_ldsomap_offset == -1)
    return 0;

  return read_memory_typed_address (info->debug_base + lmo->r_ldsomap_offset,
				    ptr_type);
}

/* On Solaris systems with some versions of the dynamic linker,
   ld.so's l_name pointer points to the SONAME in the string table
   rather than into writable memory.  So that GDB can find shared
   libraries when loading a core file generated by gcore, ensure that
   memory areas containing the l_name string are saved in the core
   file.  */

static int
svr4_keep_data_in_core (CORE_ADDR vaddr, unsigned long size)
{
  struct svr4_info *info;
  CORE_ADDR ldsomap;
  struct so_list *new;
  struct cleanup *old_chain;
  struct link_map_offsets *lmo;
  CORE_ADDR lm_name;

  info = get_svr4_info ();

  info->debug_base = 0;
  locate_base (info);
  if (!info->debug_base)
    return 0;

  ldsomap = solib_svr4_r_ldsomap (info);
  if (!ldsomap)
    return 0;

  lmo = svr4_fetch_link_map_offsets ();
  new = XZALLOC (struct so_list);
  old_chain = make_cleanup (xfree, new);
  new->lm_info = xmalloc (sizeof (struct lm_info));
  make_cleanup (xfree, new->lm_info);
  new->lm_info->l_addr = (CORE_ADDR)-1;
  new->lm_info->lm_addr = ldsomap;
  new->lm_info->lm = xzalloc (lmo->link_map_size);
  make_cleanup (xfree, new->lm_info->lm);
  read_memory (ldsomap, new->lm_info->lm, lmo->link_map_size);
  lm_name = LM_NAME (new);
  do_cleanups (old_chain);

  return (lm_name >= vaddr && lm_name < vaddr + size);
}

/*

  LOCAL FUNCTION

  open_symbol_file_object

  SYNOPSIS

  void open_symbol_file_object (void *from_tty)

  DESCRIPTION

  If no open symbol file, attempt to locate and open the main symbol
  file.  On SVR4 systems, this is the first link map entry.  If its
  name is here, we can open it.  Useful when attaching to a process
  without first loading its symbol file.

  If FROM_TTYP dereferences to a non-zero integer, allow messages to
  be printed.  This parameter is a pointer rather than an int because
  open_symbol_file_object() is called via catch_errors() and
  catch_errors() requires a pointer argument. */

static int
open_symbol_file_object (void *from_ttyp)
{
  CORE_ADDR lm, l_name;
  char *filename;
  int errcode;
  int from_tty = *(int *)from_ttyp;
  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
  struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
  int l_name_size = TYPE_LENGTH (ptr_type);
  gdb_byte *l_name_buf = xmalloc (l_name_size);
  struct cleanup *cleanups = make_cleanup (xfree, l_name_buf);
  struct svr4_info *info = get_svr4_info ();

  if (symfile_objfile)
    if (!query (_("Attempt to reload symbols from process? ")))
      return 0;

  /* Always locate the debug struct, in case it has moved.  */
  info->debug_base = 0;
  if (locate_base (info) == 0)
    return 0;	/* failed somehow... */

  /* First link map member should be the executable.  */
  lm = solib_svr4_r_map (info);
  if (lm == 0)
    return 0;	/* failed somehow... */

  /* Read address of name from target memory to GDB.  */
  read_memory (lm + lmo->l_name_offset, l_name_buf, l_name_size);

  /* Convert the address to host format.  */
  l_name = extract_typed_address (l_name_buf, ptr_type);

  /* Free l_name_buf.  */
  do_cleanups (cleanups);

  if (l_name == 0)
    return 0;		/* No filename.  */

  /* Now fetch the filename from target memory.  */
  target_read_string (l_name, &filename, SO_NAME_MAX_PATH_SIZE - 1, &errcode);
  make_cleanup (xfree, filename);

  if (errcode)
    {
      warning (_("failed to read exec filename from attached file: %s"),
	       safe_strerror (errcode));
      return 0;
    }

  /* Have a pathname: read the symbol file.  */
  symbol_file_add_main (filename, from_tty);

  return 1;
}

/* If no shared library information is available from the dynamic
   linker, build a fallback list from other sources.  */

static struct so_list *
svr4_default_sos (void)
{
  struct svr4_info *info = get_svr4_info ();

  struct so_list *head = NULL;
  struct so_list **link_ptr = &head;

  if (info->debug_loader_offset_p)
    {
      struct so_list *new = XZALLOC (struct so_list);

      new->lm_info = xmalloc (sizeof (struct lm_info));

      /* Nothing will ever check the cached copy of the link
	 map if we set l_addr.  */
      new->lm_info->l_addr = info->debug_loader_offset;
      new->lm_info->lm_addr = 0;
      new->lm_info->lm = NULL;

      strncpy (new->so_name, info->debug_loader_name,
	       SO_NAME_MAX_PATH_SIZE - 1);
      new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
      strcpy (new->so_original_name, new->so_name);

      *link_ptr = new;
      link_ptr = &new->next;
    }

  return head;
}

/* LOCAL FUNCTION

   current_sos -- build a list of currently loaded shared objects

   SYNOPSIS

   struct so_list *current_sos ()

   DESCRIPTION

   Build a list of `struct so_list' objects describing the shared
   objects currently loaded in the inferior.  This list does not
   include an entry for the main executable file.

   Note that we only gather information directly available from the
   inferior --- we don't examine any of the shared library files
   themselves.  The declaration of `struct so_list' says which fields
   we provide values for.  */

static struct so_list *
svr4_current_sos (void)
{
  CORE_ADDR lm;
  struct so_list *head = 0;
  struct so_list **link_ptr = &head;
  CORE_ADDR ldsomap = 0;
  struct svr4_info *info;

  info = get_svr4_info ();

  /* Always locate the debug struct, in case it has moved.  */
  info->debug_base = 0;
  locate_base (info);

  /* If we can't find the dynamic linker's base structure, this
     must not be a dynamically linked executable.  Hmm.  */
  if (! info->debug_base)
    return svr4_default_sos ();

  /* Walk the inferior's link map list, and build our list of
     `struct so_list' nodes.  */
  lm = solib_svr4_r_map (info);

  while (lm)
    {
      struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
      struct so_list *new = XZALLOC (struct so_list);
      struct cleanup *old_chain = make_cleanup (xfree, new);

      new->lm_info = xmalloc (sizeof (struct lm_info));
      make_cleanup (xfree, new->lm_info);

      new->lm_info->l_addr = (CORE_ADDR)-1;
      new->lm_info->lm_addr = lm;
      new->lm_info->lm = xzalloc (lmo->link_map_size);
      make_cleanup (xfree, new->lm_info->lm);

      read_memory (lm, new->lm_info->lm, lmo->link_map_size);

      lm = LM_NEXT (new);

      /* For SVR4 versions, the first entry in the link map is for the
         inferior executable, so we must ignore it.  For some versions of
         SVR4, it has no name.  For others (Solaris 2.3 for example), it
         does have a name, so we can no longer use a missing name to
         decide when to ignore it. */
      if (IGNORE_FIRST_LINK_MAP_ENTRY (new) && ldsomap == 0)
	{
	  info->main_lm_addr = new->lm_info->lm_addr;
	  free_so (new);
	}
      else
	{
	  int errcode;
	  char *buffer;

	  /* Extract this shared object's name.  */
	  target_read_string (LM_NAME (new), &buffer,
			      SO_NAME_MAX_PATH_SIZE - 1, &errcode);
	  if (errcode != 0)
	    warning (_("Can't read pathname for load map: %s."),
		     safe_strerror (errcode));
	  else
	    {
	      strncpy (new->so_name, buffer, SO_NAME_MAX_PATH_SIZE - 1);
	      new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
	      strcpy (new->so_original_name, new->so_name);
	    }
	  xfree (buffer);

	  /* If this entry has no name, or its name matches the name
	     for the main executable, don't include it in the list.  */
	  if (! new->so_name[0]
	      || match_main (new->so_name))
	    free_so (new);
	  else
	    {
	      new->next = 0;
	      *link_ptr = new;
	      link_ptr = &new->next;
	    }
	}

      /* On Solaris, the dynamic linker is not in the normal list of
	 shared objects, so make sure we pick it up too.  Having
	 symbol information for the dynamic linker is quite crucial
	 for skipping dynamic linker resolver code.  */
      if (lm == 0 && ldsomap == 0)
	lm = ldsomap = solib_svr4_r_ldsomap (info);

      discard_cleanups (old_chain);
    }

  if (head == NULL)
    return svr4_default_sos ();

  return head;
}

/* Get the address of the link_map for a given OBJFILE.  */

CORE_ADDR
svr4_fetch_objfile_link_map (struct objfile *objfile)
{
  struct so_list *so;
  struct svr4_info *info = get_svr4_info ();

  /* Cause svr4_current_sos() to be run if it hasn't been already.  */
  if (info->main_lm_addr == 0)
    solib_add (NULL, 0, &current_target, auto_solib_add);

  /* svr4_current_sos() will set main_lm_addr for the main executable.  */
  if (objfile == symfile_objfile)
    return info->main_lm_addr;

  /* The other link map addresses may be found by examining the list
     of shared libraries.  */
  for (so = master_so_list (); so; so = so->next)
    if (so->objfile == objfile)
      return so->lm_info->lm_addr;

  /* Not found!  */
  return 0;
}

/* On some systems, the only way to recognize the link map entry for
   the main executable file is by looking at its name.  Return
   non-zero iff SONAME matches one of the known main executable names.  */

static int
match_main (char *soname)
{
  char **mainp;

  for (mainp = main_name_list; *mainp != NULL; mainp++)
    {
      if (strcmp (soname, *mainp) == 0)
	return (1);
    }

  return (0);
}

/* Return 1 if PC lies in the dynamic symbol resolution code of the
   SVR4 run time loader.  */

int
svr4_in_dynsym_resolve_code (CORE_ADDR pc)
{
  struct svr4_info *info = get_svr4_info ();

  return ((pc >= info->interp_text_sect_low
	   && pc < info->interp_text_sect_high)
	  || (pc >= info->interp_plt_sect_low
	      && pc < info->interp_plt_sect_high)
	  || in_plt_section (pc, NULL));
}

/* Given an executable's ABFD and target, compute the entry-point
   address.  */

static CORE_ADDR
exec_entry_point (struct bfd *abfd, struct target_ops *targ)
{
  /* KevinB wrote ... for most targets, the address returned by
     bfd_get_start_address() is the entry point for the start
     function.  But, for some targets, bfd_get_start_address() returns
     the address of a function descriptor from which the entry point
     address may be extracted.  This address is extracted by
     gdbarch_convert_from_func_ptr_addr().  The method
     gdbarch_convert_from_func_ptr_addr() is the merely the identify
     function for targets which don't use function descriptors.  */
  return gdbarch_convert_from_func_ptr_addr (target_gdbarch,
					     bfd_get_start_address (abfd),
					     targ);
}

/*

   LOCAL FUNCTION

   enable_break -- arrange for dynamic linker to hit breakpoint

   SYNOPSIS

   int enable_break (void)

   DESCRIPTION

   Both the SunOS and the SVR4 dynamic linkers have, as part of their
   debugger interface, support for arranging for the inferior to hit
   a breakpoint after mapping in the shared libraries.  This function
   enables that breakpoint.

   For SunOS, there is a special flag location (in_debugger) which we
   set to 1.  When the dynamic linker sees this flag set, it will set
   a breakpoint at a location known only to itself, after saving the
   original contents of that place and the breakpoint address itself,
   in it's own internal structures.  When we resume the inferior, it
   will eventually take a SIGTRAP when it runs into the breakpoint.
   We handle this (in a different place) by restoring the contents of
   the breakpointed location (which is only known after it stops),
   chasing around to locate the shared libraries that have been
   loaded, then resuming.

   For SVR4, the debugger interface structure contains a member (r_brk)
   which is statically initialized at the time the shared library is
   built, to the offset of a function (_r_debug_state) which is guaran-
   teed to be called once before mapping in a library, and again when
   the mapping is complete.  At the time we are examining this member,
   it contains only the unrelocated offset of the function, so we have
   to do our own relocation.  Later, when the dynamic linker actually
   runs, it relocates r_brk to be the actual address of _r_debug_state().

   The debugger interface structure also contains an enumeration which
   is set to either RT_ADD or RT_DELETE prior to changing the mapping,
   depending upon whether or not the library is being mapped or unmapped,
   and then set to RT_CONSISTENT after the library is mapped/unmapped.
 */

static int
enable_break (struct svr4_info *info, int from_tty)
{
  struct minimal_symbol *msymbol;
  char **bkpt_namep;
  asection *interp_sect;
  gdb_byte *interp_name;
  CORE_ADDR sym_addr;

  info->interp_text_sect_low = info->interp_text_sect_high = 0;
  info->interp_plt_sect_low = info->interp_plt_sect_high = 0;

  /* If we already have a shared library list in the target, and
     r_debug contains r_brk, set the breakpoint there - this should
     mean r_brk has already been relocated.  Assume the dynamic linker
     is the object containing r_brk.  */

  solib_add (NULL, from_tty, &current_target, auto_solib_add);
  sym_addr = 0;
  if (info->debug_base && solib_svr4_r_map (info) != 0)
    sym_addr = solib_svr4_r_brk (info);

  if (sym_addr != 0)
    {
      struct obj_section *os;

      sym_addr = gdbarch_addr_bits_remove
	(target_gdbarch, gdbarch_convert_from_func_ptr_addr (target_gdbarch,
							      sym_addr,
							      &current_target));

      /* On at least some versions of Solaris there's a dynamic relocation
	 on _r_debug.r_brk and SYM_ADDR may not be relocated yet, e.g., if
	 we get control before the dynamic linker has self-relocated.
	 Check if SYM_ADDR is in a known section, if it is assume we can
	 trust its value.  This is just a heuristic though, it could go away
	 or be replaced if it's getting in the way.

	 On ARM we need to know whether the ISA of rtld_db_dlactivity (or
	 however it's spelled in your particular system) is ARM or Thumb.
	 That knowledge is encoded in the address, if it's Thumb the low bit
	 is 1.  However, we've stripped that info above and it's not clear
	 what all the consequences are of passing a non-addr_bits_remove'd
	 address to create_solib_event_breakpoint.  The call to
	 find_pc_section verifies we know about the address and have some
	 hope of computing the right kind of breakpoint to use (via
	 symbol info).  It does mean that GDB needs to be pointed at a
	 non-stripped version of the dynamic linker in order to obtain
	 information it already knows about.  Sigh.  */

      os = find_pc_section (sym_addr);
      if (os != NULL)
	{
	  /* Record the relocated start and end address of the dynamic linker
	     text and plt section for svr4_in_dynsym_resolve_code.  */
	  bfd *tmp_bfd;
	  CORE_ADDR load_addr;

	  tmp_bfd = os->objfile->obfd;
	  load_addr = ANOFFSET (os->objfile->section_offsets,
				os->objfile->sect_index_text);

	  interp_sect = bfd_get_section_by_name (tmp_bfd, ".text");
	  if (interp_sect)
	    {
	      info->interp_text_sect_low =
		bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
	      info->interp_text_sect_high =
		info->interp_text_sect_low
		+ bfd_section_size (tmp_bfd, interp_sect);
	    }
	  interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt");
	  if (interp_sect)
	    {
	      info->interp_plt_sect_low =
		bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
	      info->interp_plt_sect_high =
		info->interp_plt_sect_low
		+ bfd_section_size (tmp_bfd, interp_sect);
	    }

	  create_solib_event_breakpoint (target_gdbarch, sym_addr);
	  return 1;
	}
    }

  /* Find the program interpreter; if not found, warn the user and drop
     into the old breakpoint at symbol code.  */
  interp_name = find_program_interpreter ();
  if (interp_name)
    {
      CORE_ADDR load_addr = 0;
      int load_addr_found = 0;
      int loader_found_in_list = 0;
      struct so_list *so;
      bfd *tmp_bfd = NULL;
      struct target_ops *tmp_bfd_target;
      volatile struct gdb_exception ex;

      sym_addr = 0;

      /* Now we need to figure out where the dynamic linker was
         loaded so that we can load its symbols and place a breakpoint
         in the dynamic linker itself.

         This address is stored on the stack.  However, I've been unable
         to find any magic formula to find it for Solaris (appears to
         be trivial on GNU/Linux).  Therefore, we have to try an alternate
         mechanism to find the dynamic linker's base address.  */

      TRY_CATCH (ex, RETURN_MASK_ALL)
        {
	  tmp_bfd = solib_bfd_open (interp_name);
	}
      if (tmp_bfd == NULL)
	goto bkpt_at_symbol;

      /* Now convert the TMP_BFD into a target.  That way target, as
         well as BFD operations can be used.  Note that closing the
         target will also close the underlying bfd.  */
      tmp_bfd_target = target_bfd_reopen (tmp_bfd);

      /* On a running target, we can get the dynamic linker's base
         address from the shared library table.  */
      so = master_so_list ();
      while (so)
	{
	  if (svr4_same_1 (interp_name, so->so_original_name))
	    {
	      load_addr_found = 1;
	      loader_found_in_list = 1;
	      load_addr = LM_ADDR_CHECK (so, tmp_bfd);
	      break;
	    }
	  so = so->next;
	}

      /* If we were not able to find the base address of the loader
         from our so_list, then try using the AT_BASE auxilliary entry.  */
      if (!load_addr_found)
        if (target_auxv_search (&current_target, AT_BASE, &load_addr) > 0)
	  {
	    int addr_bit = gdbarch_addr_bit (target_gdbarch);

	    /* Ensure LOAD_ADDR has proper sign in its possible upper bits so
	       that `+ load_addr' will overflow CORE_ADDR width not creating
	       invalid addresses like 0x101234567 for 32bit inferiors on 64bit
	       GDB.  */

	    if (addr_bit < (sizeof (CORE_ADDR) * HOST_CHAR_BIT))
	      {
		CORE_ADDR space_size = (CORE_ADDR) 1 << addr_bit;
		CORE_ADDR tmp_entry_point = exec_entry_point (tmp_bfd,
							      tmp_bfd_target);

		gdb_assert (load_addr < space_size);

		/* TMP_ENTRY_POINT exceeding SPACE_SIZE would be for prelinked
		   64bit ld.so with 32bit executable, it should not happen.  */

		if (tmp_entry_point < space_size
		    && tmp_entry_point + load_addr >= space_size)
		  load_addr -= space_size;
	      }

	    load_addr_found = 1;
	  }

      /* Otherwise we find the dynamic linker's base address by examining
	 the current pc (which should point at the entry point for the
	 dynamic linker) and subtracting the offset of the entry point.

         This is more fragile than the previous approaches, but is a good
         fallback method because it has actually been working well in
         most cases.  */
      if (!load_addr_found)
	{
	  struct regcache *regcache
	    = get_thread_arch_regcache (inferior_ptid, target_gdbarch);
	  load_addr = (regcache_read_pc (regcache)
		       - exec_entry_point (tmp_bfd, tmp_bfd_target));
	}

      if (!loader_found_in_list)
	{
	  info->debug_loader_name = xstrdup (interp_name);
	  info->debug_loader_offset_p = 1;
	  info->debug_loader_offset = load_addr;
	  solib_add (NULL, from_tty, &current_target, auto_solib_add);
	}

      /* Record the relocated start and end address of the dynamic linker
         text and plt section for svr4_in_dynsym_resolve_code.  */
      interp_sect = bfd_get_section_by_name (tmp_bfd, ".text");
      if (interp_sect)
	{
	  info->interp_text_sect_low =
	    bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
	  info->interp_text_sect_high =
	    info->interp_text_sect_low
	    + bfd_section_size (tmp_bfd, interp_sect);
	}
      interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt");
      if (interp_sect)
	{
	  info->interp_plt_sect_low =
	    bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
	  info->interp_plt_sect_high =
	    info->interp_plt_sect_low
	    + bfd_section_size (tmp_bfd, interp_sect);
	}

      /* Now try to set a breakpoint in the dynamic linker.  */
      for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++)
	{
	  sym_addr = bfd_lookup_symbol (tmp_bfd, *bkpt_namep);
	  if (sym_addr != 0)
	    break;
	}

      if (sym_addr != 0)
	/* Convert 'sym_addr' from a function pointer to an address.
	   Because we pass tmp_bfd_target instead of the current
	   target, this will always produce an unrelocated value.  */
	sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
						       sym_addr,
						       tmp_bfd_target);

      /* We're done with both the temporary bfd and target.  Remember,
         closing the target closes the underlying bfd.  */
      target_close (tmp_bfd_target, 0);

      if (sym_addr != 0)
	{
	  create_solib_event_breakpoint (target_gdbarch, load_addr + sym_addr);
	  xfree (interp_name);
	  return 1;
	}

      /* For whatever reason we couldn't set a breakpoint in the dynamic
         linker.  Warn and drop into the old code.  */
    bkpt_at_symbol:
      xfree (interp_name);
      warning (_("Unable to find dynamic linker breakpoint function.\n"
               "GDB will be unable to debug shared library initializers\n"
               "and track explicitly loaded dynamic code."));
    }

  /* Scan through the lists of symbols, trying to look up the symbol and
     set a breakpoint there.  Terminate loop when we/if we succeed.  */

  for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++)
    {
      msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
      if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
	{
	  sym_addr = SYMBOL_VALUE_ADDRESS (msymbol);
	  sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
							 sym_addr,
							 &current_target);
	  create_solib_event_breakpoint (target_gdbarch, sym_addr);
	  return 1;
	}
    }

  for (bkpt_namep = bkpt_names; *bkpt_namep != NULL; bkpt_namep++)
    {
      msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
      if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
	{
	  sym_addr = SYMBOL_VALUE_ADDRESS (msymbol);
	  sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
							 sym_addr,
							 &current_target);
	  create_solib_event_breakpoint (target_gdbarch, sym_addr);
	  return 1;
	}
    }
  return 0;
}

/*

   LOCAL FUNCTION

   special_symbol_handling -- additional shared library symbol handling

   SYNOPSIS

   void special_symbol_handling ()

   DESCRIPTION

   Once the symbols from a shared object have been loaded in the usual
   way, we are called to do any system specific symbol handling that 
   is needed.

   For SunOS4, this consisted of grunging around in the dynamic
   linkers structures to find symbol definitions for "common" symbols
   and adding them to the minimal symbol table for the runtime common
   objfile.

   However, for SVR4, there's nothing to do.

 */

static void
svr4_special_symbol_handling (void)
{
  svr4_relocate_main_executable ();
}

/* Read the ELF program headers from ABFD.  Return the contents and
   set *PHDRS_SIZE to the size of the program headers.  */

static gdb_byte *
read_program_headers_from_bfd (bfd *abfd, int *phdrs_size)
{
  Elf_Internal_Ehdr *ehdr;
  gdb_byte *buf;

  ehdr = elf_elfheader (abfd);

  *phdrs_size = ehdr->e_phnum * ehdr->e_phentsize;
  if (*phdrs_size == 0)
    return NULL;

  buf = xmalloc (*phdrs_size);
  if (bfd_seek (abfd, ehdr->e_phoff, SEEK_SET) != 0
      || bfd_bread (buf, *phdrs_size, abfd) != *phdrs_size)
    {
      xfree (buf);
      return NULL;
    }

  return buf;
}

/* Return 1 and fill *DISPLACEMENTP with detected PIE offset of inferior
   exec_bfd.  Otherwise return 0.

   We relocate all of the sections by the same amount.  This
   behavior is mandated by recent editions of the System V ABI. 
   According to the System V Application Binary Interface,
   Edition 4.1, page 5-5:

     ...  Though the system chooses virtual addresses for
     individual processes, it maintains the segments' relative
     positions.  Because position-independent code uses relative
     addressesing between segments, the difference between
     virtual addresses in memory must match the difference
     between virtual addresses in the file.  The difference
     between the virtual address of any segment in memory and
     the corresponding virtual address in the file is thus a
     single constant value for any one executable or shared
     object in a given process.  This difference is the base
     address.  One use of the base address is to relocate the
     memory image of the program during dynamic linking.

   The same language also appears in Edition 4.0 of the System V
   ABI and is left unspecified in some of the earlier editions.

   Decide if the objfile needs to be relocated.  As indicated above, we will
   only be here when execution is stopped.  But during attachment PC can be at
   arbitrary address therefore regcache_read_pc can be misleading (contrary to
   the auxv AT_ENTRY value).  Moreover for executable with interpreter section
   regcache_read_pc would point to the interpreter and not the main executable.

   So, to summarize, relocations are necessary when the start address obtained
   from the executable is different from the address in auxv AT_ENTRY entry.
   
   [ The astute reader will note that we also test to make sure that
     the executable in question has the DYNAMIC flag set.  It is my
     opinion that this test is unnecessary (undesirable even).  It
     was added to avoid inadvertent relocation of an executable
     whose e_type member in the ELF header is not ET_DYN.  There may
     be a time in the future when it is desirable to do relocations
     on other types of files as well in which case this condition
     should either be removed or modified to accomodate the new file
     type.  - Kevin, Nov 2000. ]  */

static int
svr4_exec_displacement (CORE_ADDR *displacementp)
{
  /* ENTRY_POINT is a possible function descriptor - before
     a call to gdbarch_convert_from_func_ptr_addr.  */
  CORE_ADDR entry_point, displacement;

  if (exec_bfd == NULL)
    return 0;

  /* Therefore for ELF it is ET_EXEC and not ET_DYN.  Both shared libraries
     being executed themselves and PIE (Position Independent Executable)
     executables are ET_DYN.  */

  if ((bfd_get_file_flags (exec_bfd) & DYNAMIC) == 0)
    return 0;

  if (target_auxv_search (&current_target, AT_ENTRY, &entry_point) <= 0)
    return 0;

  displacement = entry_point - bfd_get_start_address (exec_bfd);

  /* Verify the DISPLACEMENT candidate complies with the required page
     alignment.  It is cheaper than the program headers comparison below.  */

  if (bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
    {
      const struct elf_backend_data *elf = get_elf_backend_data (exec_bfd);

      /* p_align of PT_LOAD segments does not specify any alignment but
	 only congruency of addresses:
	   p_offset % p_align == p_vaddr % p_align
	 Kernel is free to load the executable with lower alignment.  */

      if ((displacement & (elf->minpagesize - 1)) != 0)
	return 0;
    }

  /* Verify that the auxilliary vector describes the same file as exec_bfd, by
     comparing their program headers.  If the program headers in the auxilliary
     vector do not match the program headers in the executable, then we are
     looking at a different file than the one used by the kernel - for
     instance, "gdb program" connected to "gdbserver :PORT ld.so program".  */

  if (bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
    {
      /* Be optimistic and clear OK only if GDB was able to verify the headers
	 really do not match.  */
      int phdrs_size, phdrs2_size, ok = 1;
      gdb_byte *buf, *buf2;

      buf = read_program_header (-1, &phdrs_size, NULL);
      buf2 = read_program_headers_from_bfd (exec_bfd, &phdrs2_size);
      if (buf != NULL && buf2 != NULL
	  && (phdrs_size != phdrs2_size
	      || memcmp (buf, buf2, phdrs_size) != 0))
	ok = 0;

      xfree (buf);
      xfree (buf2);

      if (!ok)
	return 0;
    }

  if (info_verbose)
    {
      /* It can be printed repeatedly as there is no easy way to check
	 the executable symbols/file has been already relocated to
	 displacement.  */

      printf_unfiltered (_("Using PIE (Position Independent Executable) "
			   "displacement %s for \"%s\".\n"),
			 paddress (target_gdbarch, displacement),
			 bfd_get_filename (exec_bfd));
    }

  *displacementp = displacement;
  return 1;
}

/* Relocate the main executable.  This function should be called upon
   stopping the inferior process at the entry point to the program. 
   The entry point from BFD is compared to the AT_ENTRY of AUXV and if they are
   different, the main executable is relocated by the proper amount.  */

static void
svr4_relocate_main_executable (void)
{
  CORE_ADDR displacement;

  if (symfile_objfile)
    {
      int i;

      /* Remote target may have already set specific offsets by `qOffsets'
	 which should be preferred.  */

      for (i = 0; i < symfile_objfile->num_sections; i++)
	if (ANOFFSET (symfile_objfile->section_offsets, i) != 0)
	  return;
    }

  if (! svr4_exec_displacement (&displacement))
    return;

  /* Even DISPLACEMENT 0 is a valid new difference of in-memory vs. in-file
     addresses.  */

  if (symfile_objfile)
    {
      struct section_offsets *new_offsets;
      int i;

      new_offsets = alloca (symfile_objfile->num_sections
			    * sizeof (*new_offsets));

      for (i = 0; i < symfile_objfile->num_sections; i++)
	new_offsets->offsets[i] = displacement;

      objfile_relocate (symfile_objfile, new_offsets);
    }
  else if (exec_bfd)
    {
      asection *asect;

      for (asect = exec_bfd->sections; asect != NULL; asect = asect->next)
	exec_set_section_address (bfd_get_filename (exec_bfd), asect->index,
				  (bfd_section_vma (exec_bfd, asect)
				   + displacement));
    }
}

/*

   GLOBAL FUNCTION

   svr4_solib_create_inferior_hook -- shared library startup support

   SYNOPSIS

   void svr4_solib_create_inferior_hook (int from_tty)

   DESCRIPTION

   When gdb starts up the inferior, it nurses it along (through the
   shell) until it is ready to execute it's first instruction.  At this
   point, this function gets called via expansion of the macro
   SOLIB_CREATE_INFERIOR_HOOK.

   For SunOS executables, this first instruction is typically the
   one at "_start", or a similar text label, regardless of whether
   the executable is statically or dynamically linked.  The runtime
   startup code takes care of dynamically linking in any shared
   libraries, once gdb allows the inferior to continue.

   For SVR4 executables, this first instruction is either the first
   instruction in the dynamic linker (for dynamically linked
   executables) or the instruction at "start" for statically linked
   executables.  For dynamically linked executables, the system
   first exec's /lib/libc.so.N, which contains the dynamic linker,
   and starts it running.  The dynamic linker maps in any needed
   shared libraries, maps in the actual user executable, and then
   jumps to "start" in the user executable.

   For both SunOS shared libraries, and SVR4 shared libraries, we
   can arrange to cooperate with the dynamic linker to discover the
   names of shared libraries that are dynamically linked, and the
   base addresses to which they are linked.

   This function is responsible for discovering those names and
   addresses, and saving sufficient information about them to allow
   their symbols to be read at a later time.

   FIXME

   Between enable_break() and disable_break(), this code does not
   properly handle hitting breakpoints which the user might have
   set in the startup code or in the dynamic linker itself.  Proper
   handling will probably have to wait until the implementation is
   changed to use the "breakpoint handler function" method.

   Also, what if child has exit()ed?  Must exit loop somehow.
 */

static void
svr4_solib_create_inferior_hook (int from_tty)
{
  struct inferior *inf;
  struct thread_info *tp;
  struct svr4_info *info;

  info = get_svr4_info ();

  /* Relocate the main executable if necessary.  */
  if (current_inferior ()->attach_flag == 0)
    svr4_relocate_main_executable ();

  if (!svr4_have_link_map_offsets ())
    return;

  if (!enable_break (info, from_tty))
    return;

#if defined(_SCO_DS)
  /* SCO needs the loop below, other systems should be using the
     special shared library breakpoints and the shared library breakpoint
     service routine.

     Now run the target.  It will eventually hit the breakpoint, at
     which point all of the libraries will have been mapped in and we
     can go groveling around in the dynamic linker structures to find
     out what we need to know about them. */

  inf = current_inferior ();
  tp = inferior_thread ();

  clear_proceed_status ();
  inf->stop_soon = STOP_QUIETLY;
  tp->stop_signal = TARGET_SIGNAL_0;
  do
    {
      target_resume (pid_to_ptid (-1), 0, tp->stop_signal);
      wait_for_inferior (0);
    }
  while (tp->stop_signal != TARGET_SIGNAL_TRAP);
  inf->stop_soon = NO_STOP_QUIETLY;
#endif /* defined(_SCO_DS) */
}

static void
svr4_clear_solib (void)
{
  struct svr4_info *info;

  info = get_svr4_info ();
  info->debug_base = 0;
  info->debug_loader_offset_p = 0;
  info->debug_loader_offset = 0;
  xfree (info->debug_loader_name);
  info->debug_loader_name = NULL;
}

static void
svr4_free_so (struct so_list *so)
{
  xfree (so->lm_info->lm);
  xfree (so->lm_info);
}


/* Clear any bits of ADDR that wouldn't fit in a target-format
   data pointer.  "Data pointer" here refers to whatever sort of
   address the dynamic linker uses to manage its sections.  At the
   moment, we don't support shared libraries on any processors where
   code and data pointers are different sizes.

   This isn't really the right solution.  What we really need here is
   a way to do arithmetic on CORE_ADDR values that respects the
   natural pointer/address correspondence.  (For example, on the MIPS,
   converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to
   sign-extend the value.  There, simply truncating the bits above
   gdbarch_ptr_bit, as we do below, is no good.)  This should probably
   be a new gdbarch method or something.  */
static CORE_ADDR
svr4_truncate_ptr (CORE_ADDR addr)
{
  if (gdbarch_ptr_bit (target_gdbarch) == sizeof (CORE_ADDR) * 8)
    /* We don't need to truncate anything, and the bit twiddling below
       will fail due to overflow problems.  */
    return addr;
  else
    return addr & (((CORE_ADDR) 1 << gdbarch_ptr_bit (target_gdbarch)) - 1);
}


static void
svr4_relocate_section_addresses (struct so_list *so,
                                 struct target_section *sec)
{
  sec->addr    = svr4_truncate_ptr (sec->addr    + LM_ADDR_CHECK (so,
								  sec->bfd));
  sec->endaddr = svr4_truncate_ptr (sec->endaddr + LM_ADDR_CHECK (so,
								  sec->bfd));
}


/* Architecture-specific operations.  */

/* Per-architecture data key.  */
static struct gdbarch_data *solib_svr4_data;

struct solib_svr4_ops
{
  /* Return a description of the layout of `struct link_map'.  */
  struct link_map_offsets *(*fetch_link_map_offsets)(void);
};

/* Return a default for the architecture-specific operations.  */

static void *
solib_svr4_init (struct obstack *obstack)
{
  struct solib_svr4_ops *ops;

  ops = OBSTACK_ZALLOC (obstack, struct solib_svr4_ops);
  ops->fetch_link_map_offsets = NULL;
  return ops;
}

/* Set the architecture-specific `struct link_map_offsets' fetcher for
   GDBARCH to FLMO.  Also, install SVR4 solib_ops into GDBARCH.  */

void
set_solib_svr4_fetch_link_map_offsets (struct gdbarch *gdbarch,
                                       struct link_map_offsets *(*flmo) (void))
{
  struct solib_svr4_ops *ops = gdbarch_data (gdbarch, solib_svr4_data);

  ops->fetch_link_map_offsets = flmo;

  set_solib_ops (gdbarch, &svr4_so_ops);
}

/* Fetch a link_map_offsets structure using the architecture-specific
   `struct link_map_offsets' fetcher.  */

static struct link_map_offsets *
svr4_fetch_link_map_offsets (void)
{
  struct solib_svr4_ops *ops = gdbarch_data (target_gdbarch, solib_svr4_data);

  gdb_assert (ops->fetch_link_map_offsets);
  return ops->fetch_link_map_offsets ();
}

/* Return 1 if a link map offset fetcher has been defined, 0 otherwise.  */

static int
svr4_have_link_map_offsets (void)
{
  struct solib_svr4_ops *ops = gdbarch_data (target_gdbarch, solib_svr4_data);
  return (ops->fetch_link_map_offsets != NULL);
}


/* Most OS'es that have SVR4-style ELF dynamic libraries define a
   `struct r_debug' and a `struct link_map' that are binary compatible
   with the origional SVR4 implementation.  */

/* Fetch (and possibly build) an appropriate `struct link_map_offsets'
   for an ILP32 SVR4 system.  */
  
struct link_map_offsets *
svr4_ilp32_fetch_link_map_offsets (void)
{
  static struct link_map_offsets lmo;
  static struct link_map_offsets *lmp = NULL;

  if (lmp == NULL)
    {
      lmp = &lmo;

      lmo.r_version_offset = 0;
      lmo.r_version_size = 4;
      lmo.r_map_offset = 4;
      lmo.r_brk_offset = 8;
      lmo.r_ldsomap_offset = 20;

      /* Everything we need is in the first 20 bytes.  */
      lmo.link_map_size = 20;
      lmo.l_addr_offset = 0;
      lmo.l_name_offset = 4;
      lmo.l_ld_offset = 8;
      lmo.l_next_offset = 12;
      lmo.l_prev_offset = 16;
    }

  return lmp;
}

/* Fetch (and possibly build) an appropriate `struct link_map_offsets'
   for an LP64 SVR4 system.  */
  
struct link_map_offsets *
svr4_lp64_fetch_link_map_offsets (void)
{
  static struct link_map_offsets lmo;
  static struct link_map_offsets *lmp = NULL;

  if (lmp == NULL)
    {
      lmp = &lmo;

      lmo.r_version_offset = 0;
      lmo.r_version_size = 4;
      lmo.r_map_offset = 8;
      lmo.r_brk_offset = 16;
      lmo.r_ldsomap_offset = 40;

      /* Everything we need is in the first 40 bytes.  */
      lmo.link_map_size = 40;
      lmo.l_addr_offset = 0;
      lmo.l_name_offset = 8;
      lmo.l_ld_offset = 16;
      lmo.l_next_offset = 24;
      lmo.l_prev_offset = 32;
    }

  return lmp;
}


struct target_so_ops svr4_so_ops;

/* Lookup global symbol for ELF DSOs linked with -Bsymbolic. Those DSOs have a
   different rule for symbol lookup.  The lookup begins here in the DSO, not in
   the main executable.  */

static struct symbol *
elf_lookup_lib_symbol (const struct objfile *objfile,
		       const char *name,
		       const domain_enum domain)
{
  bfd *abfd;

  if (objfile == symfile_objfile)
    abfd = exec_bfd;
  else
    {
      /* OBJFILE should have been passed as the non-debug one.  */
      gdb_assert (objfile->separate_debug_objfile_backlink == NULL);

      abfd = objfile->obfd;
    }

  if (abfd == NULL || scan_dyntag (DT_SYMBOLIC, abfd, NULL) != 1)
    return NULL;

  return lookup_global_symbol_from_objfile (objfile, name, domain);
}

extern initialize_file_ftype _initialize_svr4_solib; /* -Wmissing-prototypes */

void
_initialize_svr4_solib (void)
{
  solib_svr4_data = gdbarch_data_register_pre_init (solib_svr4_init);
  solib_svr4_pspace_data
    = register_program_space_data_with_cleanup (svr4_pspace_data_cleanup);

  svr4_so_ops.relocate_section_addresses = svr4_relocate_section_addresses;
  svr4_so_ops.free_so = svr4_free_so;
  svr4_so_ops.clear_solib = svr4_clear_solib;
  svr4_so_ops.solib_create_inferior_hook = svr4_solib_create_inferior_hook;
  svr4_so_ops.special_symbol_handling = svr4_special_symbol_handling;
  svr4_so_ops.current_sos = svr4_current_sos;
  svr4_so_ops.open_symbol_file_object = open_symbol_file_object;
  svr4_so_ops.in_dynsym_resolve_code = svr4_in_dynsym_resolve_code;
  svr4_so_ops.bfd_open = solib_bfd_open;
  svr4_so_ops.lookup_lib_global_symbol = elf_lookup_lib_symbol;
  svr4_so_ops.same = svr4_same;
  svr4_so_ops.keep_data_in_core = svr4_keep_data_in_core;
}