File: elf.c

package info (click to toggle)
heaptrack 1.1.0%2B20180922.gitf752536-4
  • links: PTS, VCS
  • area: main
  • in suites: buster
  • size: 2,320 kB
  • sloc: cpp: 15,621; ansic: 5,886; sh: 358; xml: 199; python: 118; makefile: 11
file content (3194 lines) | stat: -rw-r--r-- 83,557 bytes parent folder | download | duplicates (3)
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
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
/* elf.c -- Get debug data from an ELF file for backtraces.
   Copyright (C) 2012-2017 Free Software Foundation, Inc.
   Written by Ian Lance Taylor, Google.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

    (1) Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.

    (2) Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in
    the documentation and/or other materials provided with the
    distribution.

    (3) The name of the author may not be used to
    endorse or promote products derived from this software without
    specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.  */

#include "config.h"

#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

#ifdef HAVE_DL_ITERATE_PHDR
#include <link.h>
#endif

#include "backtrace.h"
#include "internal.h"

#ifndef S_ISLNK
 #ifndef S_IFLNK
  #define S_IFLNK 0120000
 #endif
 #ifndef S_IFMT
  #define S_IFMT 0170000
 #endif
 #define S_ISLNK(m) (((m) & S_IFMT) == S_IFLNK)
#endif

#ifndef __GNUC__
#define __builtin_prefetch(p, r, l)
#define unlikely(x) (x)
#else
#define unlikely(x) __builtin_expect(!!(x), 0)
#endif

#if !defined(HAVE_DECL_STRNLEN) || !HAVE_DECL_STRNLEN

/* If strnlen is not declared, provide our own version.  */

static size_t
xstrnlen (const char *s, size_t maxlen)
{
  size_t i;

  for (i = 0; i < maxlen; ++i)
    if (s[i] == '\0')
      break;
  return i;
}

#define strnlen xstrnlen

#endif

#ifndef HAVE_LSTAT

/* Dummy version of lstat for systems that don't have it.  */

static int
xlstat (const char *path ATTRIBUTE_UNUSED, struct stat *st ATTRIBUTE_UNUSED)
{
  return -1;
}

#define lstat xlstat

#endif

#ifndef HAVE_READLINK

/* Dummy version of readlink for systems that don't have it.  */

static ssize_t
xreadlink (const char *path ATTRIBUTE_UNUSED, char *buf ATTRIBUTE_UNUSED,
	   size_t bufsz ATTRIBUTE_UNUSED)
{
  return -1;
}

#define readlink xreadlink

#endif

#ifndef HAVE_DL_ITERATE_PHDR

/* Dummy version of dl_iterate_phdr for systems that don't have it.  */

#define dl_phdr_info x_dl_phdr_info
#define dl_iterate_phdr x_dl_iterate_phdr

struct dl_phdr_info
{
  uintptr_t dlpi_addr;
  const char *dlpi_name;
};

static int
dl_iterate_phdr (int (*callback) (struct dl_phdr_info *,
				  size_t, void *) ATTRIBUTE_UNUSED,
		 void *data ATTRIBUTE_UNUSED)
{
  return 0;
}

#endif /* ! defined (HAVE_DL_ITERATE_PHDR) */

/* The configure script must tell us whether we are 32-bit or 64-bit
   ELF.  We could make this code test and support either possibility,
   but there is no point.  This code only works for the currently
   running executable, which means that we know the ELF mode at
   configure time.  */

#if BACKTRACE_ELF_SIZE != 32 && BACKTRACE_ELF_SIZE != 64
#error "Unknown BACKTRACE_ELF_SIZE"
#endif

/* <link.h> might #include <elf.h> which might define our constants
   with slightly different values.  Undefine them to be safe.  */

#undef EI_NIDENT
#undef EI_MAG0
#undef EI_MAG1
#undef EI_MAG2
#undef EI_MAG3
#undef EI_CLASS
#undef EI_DATA
#undef EI_VERSION
#undef ELF_MAG0
#undef ELF_MAG1
#undef ELF_MAG2
#undef ELF_MAG3
#undef ELFCLASS32
#undef ELFCLASS64
#undef ELFDATA2LSB
#undef ELFDATA2MSB
#undef EV_CURRENT
#undef ET_DYN
#undef SHN_LORESERVE
#undef SHN_XINDEX
#undef SHN_UNDEF
#undef SHT_SYMTAB
#undef SHT_STRTAB
#undef SHT_DYNSYM
#undef SHF_COMPRESSED
#undef STT_OBJECT
#undef STT_FUNC
#undef NT_GNU_BUILD_ID
#undef ELFCOMPRESS_ZLIB

/* Basic types.  */

typedef uint16_t b_elf_half;    /* Elf_Half.  */
typedef uint32_t b_elf_word;    /* Elf_Word.  */
typedef int32_t  b_elf_sword;   /* Elf_Sword.  */

#if BACKTRACE_ELF_SIZE == 32

typedef uint32_t b_elf_addr;    /* Elf_Addr.  */
typedef uint32_t b_elf_off;     /* Elf_Off.  */

typedef uint32_t b_elf_wxword;  /* 32-bit Elf_Word, 64-bit ELF_Xword.  */

#else

typedef uint64_t b_elf_addr;    /* Elf_Addr.  */
typedef uint64_t b_elf_off;     /* Elf_Off.  */
typedef uint64_t b_elf_xword;   /* Elf_Xword.  */
typedef int64_t  b_elf_sxword;  /* Elf_Sxword.  */

typedef uint64_t b_elf_wxword;  /* 32-bit Elf_Word, 64-bit ELF_Xword.  */

#endif

/* Data structures and associated constants.  */

#define EI_NIDENT 16

typedef struct {
  unsigned char	e_ident[EI_NIDENT];	/* ELF "magic number" */
  b_elf_half	e_type;			/* Identifies object file type */
  b_elf_half	e_machine;		/* Specifies required architecture */
  b_elf_word	e_version;		/* Identifies object file version */
  b_elf_addr	e_entry;		/* Entry point virtual address */
  b_elf_off	e_phoff;		/* Program header table file offset */
  b_elf_off	e_shoff;		/* Section header table file offset */
  b_elf_word	e_flags;		/* Processor-specific flags */
  b_elf_half	e_ehsize;		/* ELF header size in bytes */
  b_elf_half	e_phentsize;		/* Program header table entry size */
  b_elf_half	e_phnum;		/* Program header table entry count */
  b_elf_half	e_shentsize;		/* Section header table entry size */
  b_elf_half	e_shnum;		/* Section header table entry count */
  b_elf_half	e_shstrndx;		/* Section header string table index */
} b_elf_ehdr;  /* Elf_Ehdr.  */

#define EI_MAG0 0
#define EI_MAG1 1
#define EI_MAG2 2
#define EI_MAG3 3
#define EI_CLASS 4
#define EI_DATA 5
#define EI_VERSION 6

#define ELFMAG0 0x7f
#define ELFMAG1 'E'
#define ELFMAG2 'L'
#define ELFMAG3 'F'

#define ELFCLASS32 1
#define ELFCLASS64 2

#define ELFDATA2LSB 1
#define ELFDATA2MSB 2

#define EV_CURRENT 1

#define ET_DYN 3

typedef struct {
  b_elf_word	sh_name;		/* Section name, index in string tbl */
  b_elf_word	sh_type;		/* Type of section */
  b_elf_wxword	sh_flags;		/* Miscellaneous section attributes */
  b_elf_addr	sh_addr;		/* Section virtual addr at execution */
  b_elf_off	sh_offset;		/* Section file offset */
  b_elf_wxword	sh_size;		/* Size of section in bytes */
  b_elf_word	sh_link;		/* Index of another section */
  b_elf_word	sh_info;		/* Additional section information */
  b_elf_wxword	sh_addralign;		/* Section alignment */
  b_elf_wxword	sh_entsize;		/* Entry size if section holds table */
} b_elf_shdr;  /* Elf_Shdr.  */

#define SHN_UNDEF	0x0000		/* Undefined section */
#define SHN_LORESERVE	0xFF00		/* Begin range of reserved indices */
#define SHN_XINDEX	0xFFFF		/* Section index is held elsewhere */

#define SHT_SYMTAB 2
#define SHT_STRTAB 3
#define SHT_DYNSYM 11

#define SHF_COMPRESSED 0x800

#if BACKTRACE_ELF_SIZE == 32

typedef struct
{
  b_elf_word	st_name;		/* Symbol name, index in string tbl */
  b_elf_addr	st_value;		/* Symbol value */
  b_elf_word	st_size;		/* Symbol size */
  unsigned char	st_info;		/* Symbol binding and type */
  unsigned char	st_other;		/* Visibility and other data */
  b_elf_half	st_shndx;		/* Symbol section index */
} b_elf_sym;  /* Elf_Sym.  */

#else /* BACKTRACE_ELF_SIZE != 32 */

typedef struct
{
  b_elf_word	st_name;		/* Symbol name, index in string tbl */
  unsigned char	st_info;		/* Symbol binding and type */
  unsigned char	st_other;		/* Visibility and other data */
  b_elf_half	st_shndx;		/* Symbol section index */
  b_elf_addr	st_value;		/* Symbol value */
  b_elf_xword	st_size;		/* Symbol size */
} b_elf_sym;  /* Elf_Sym.  */

#endif /* BACKTRACE_ELF_SIZE != 32 */

#define STT_OBJECT 1
#define STT_FUNC 2

typedef struct
{
  uint32_t namesz;
  uint32_t descsz;
  uint32_t type;
  char name[1];
} b_elf_note;

#define NT_GNU_BUILD_ID 3

#if BACKTRACE_ELF_SIZE == 32

typedef struct
{
  b_elf_word	ch_type;		/* Compresstion algorithm */
  b_elf_word	ch_size;		/* Uncompressed size */
  b_elf_word	ch_addralign;		/* Alignment for uncompressed data */
} b_elf_chdr;  /* Elf_Chdr */

#else /* BACKTRACE_ELF_SIZE != 32 */

typedef struct
{
  b_elf_word	ch_type;		/* Compression algorithm */
  b_elf_word	ch_reserved;		/* Reserved */
  b_elf_xword	ch_size;		/* Uncompressed size */
  b_elf_xword	ch_addralign;		/* Alignment for uncompressed data */
} b_elf_chdr;  /* Elf_Chdr */

#endif /* BACKTRACE_ELF_SIZE != 32 */

#define ELFCOMPRESS_ZLIB 1

/* An index of ELF sections we care about.  */

enum debug_section
{
  DEBUG_INFO,
  DEBUG_LINE,
  DEBUG_ABBREV,
  DEBUG_RANGES,
  DEBUG_STR,

  /* The old style compressed sections.  This list must correspond to
     the list of normal debug sections.  */
  ZDEBUG_INFO,
  ZDEBUG_LINE,
  ZDEBUG_ABBREV,
  ZDEBUG_RANGES,
  ZDEBUG_STR,

  DEBUG_MAX
};

/* Names of sections, indexed by enum elf_section.  */

static const char * const debug_section_names[DEBUG_MAX] =
{
  ".debug_info",
  ".debug_line",
  ".debug_abbrev",
  ".debug_ranges",
  ".debug_str",
  ".zdebug_info",
  ".zdebug_line",
  ".zdebug_abbrev",
  ".zdebug_ranges",
  ".zdebug_str"
};

/* Information we gather for the sections we care about.  */

struct debug_section_info
{
  /* Section file offset.  */
  off_t offset;
  /* Section size.  */
  size_t size;
  /* Section contents, after read from file.  */
  const unsigned char *data;
  /* Whether the SHF_COMPRESSED flag is set for the section.  */
  int compressed;
};

/* Information we keep for an ELF symbol.  */

struct elf_symbol
{
  /* The name of the symbol.  */
  const char *name;
  /* The address of the symbol.  */
  uintptr_t address;
  /* The size of the symbol.  */
  size_t size;
};

/* Information to pass to elf_syminfo.  */

struct elf_syminfo_data
{
  /* Symbols for the next module.  */
  struct elf_syminfo_data *next;
  /* The ELF symbols, sorted by address.  */
  struct elf_symbol *symbols;
  /* The number of symbols.  */
  size_t count;
};

/* Compute the CRC-32 of BUF/LEN.  This uses the CRC used for
   .gnu_debuglink files.  */

static uint32_t
elf_crc32 (uint32_t crc, const unsigned char *buf, size_t len)
{
  static const uint32_t crc32_table[256] =
    {
      0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
      0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
      0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
      0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
      0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
      0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
      0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
      0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
      0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
      0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
      0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
      0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
      0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
      0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
      0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
      0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
      0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
      0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
      0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
      0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
      0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
      0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
      0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
      0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
      0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
      0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
      0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
      0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
      0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
      0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
      0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
      0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
      0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
      0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
      0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
      0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
      0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
      0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
      0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
      0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
      0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
      0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
      0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
      0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
      0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
      0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
      0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
      0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
      0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
      0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
      0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
      0x2d02ef8d
    };
  const unsigned char *end;

  crc = ~crc;
  for (end = buf + len; buf < end; ++ buf)
    crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
  return ~crc;
}

/* Return the CRC-32 of the entire file open at DESCRIPTOR.  */

static uint32_t
elf_crc32_file (struct backtrace_state *state, int descriptor,
		backtrace_error_callback error_callback, void *data)
{
  struct stat st;
  struct backtrace_view file_view;
  uint32_t ret;

  if (fstat (descriptor, &st) < 0)
    {
      error_callback (data, "fstat", errno);
      return 0;
    }

  if (!backtrace_get_view (state, descriptor, 0, st.st_size, error_callback,
			   data, &file_view))
    return 0;

  ret = elf_crc32 (0, (const unsigned char *) file_view.data, st.st_size);

  backtrace_release_view (state, &file_view, error_callback, data);

  return ret;
}

/* A dummy callback function used when we can't find any debug info.  */

static int
elf_nodebug (struct backtrace_state *state ATTRIBUTE_UNUSED,
	     uintptr_t pc ATTRIBUTE_UNUSED,
	     backtrace_full_callback callback ATTRIBUTE_UNUSED,
	     backtrace_error_callback error_callback, void *data)
{
  error_callback (data, "no debug info in ELF executable", -1);
  return 0;
}

/* A dummy callback function used when we can't find a symbol
   table.  */

void
elf_nosyms (struct backtrace_state *state ATTRIBUTE_UNUSED,
	    uintptr_t addr ATTRIBUTE_UNUSED,
	    backtrace_syminfo_callback callback ATTRIBUTE_UNUSED,
	    backtrace_error_callback error_callback, void *data)
{
  error_callback (data, "no symbol table in ELF executable", -1);
}

/* Compare struct elf_symbol for qsort.  */

static int
elf_symbol_compare (const void *v1, const void *v2)
{
  const struct elf_symbol *e1 = (const struct elf_symbol *) v1;
  const struct elf_symbol *e2 = (const struct elf_symbol *) v2;

  if (e1->address < e2->address)
    return -1;
  else if (e1->address > e2->address)
    return 1;
  else
    return 0;
}

/* Compare an ADDR against an elf_symbol for bsearch.  We allocate one
   extra entry in the array so that this can look safely at the next
   entry.  */

static int
elf_symbol_search (const void *vkey, const void *ventry)
{
  const uintptr_t *key = (const uintptr_t *) vkey;
  const struct elf_symbol *entry = (const struct elf_symbol *) ventry;
  uintptr_t addr;

  addr = *key;
  if (addr < entry->address)
    return -1;
  else if (addr >= entry->address + entry->size)
    return 1;
  else
    return 0;
}

/* Initialize the symbol table info for elf_syminfo.  */

static int
elf_initialize_syminfo (struct backtrace_state *state,
			uintptr_t base_address,
			const unsigned char *symtab_data, size_t symtab_size,
			const unsigned char *strtab, size_t strtab_size,
			backtrace_error_callback error_callback,
			void *data, struct elf_syminfo_data *sdata)
{
  size_t sym_count;
  const b_elf_sym *sym;
  size_t elf_symbol_count;
  size_t elf_symbol_size;
  struct elf_symbol *elf_symbols;
  size_t i;
  unsigned int j;

  sym_count = symtab_size / sizeof (b_elf_sym);

  /* We only care about function symbols.  Count them.  */
  sym = (const b_elf_sym *) symtab_data;
  elf_symbol_count = 0;
  for (i = 0; i < sym_count; ++i, ++sym)
    {
      int info;

      info = sym->st_info & 0xf;
      if ((info == STT_FUNC || info == STT_OBJECT)
	  && sym->st_shndx != SHN_UNDEF)
	++elf_symbol_count;
    }

  elf_symbol_size = elf_symbol_count * sizeof (struct elf_symbol);
  elf_symbols = ((struct elf_symbol *)
		 backtrace_alloc (state, elf_symbol_size, error_callback,
				  data));
  if (elf_symbols == NULL)
    return 0;

  sym = (const b_elf_sym *) symtab_data;
  j = 0;
  for (i = 0; i < sym_count; ++i, ++sym)
    {
      int info;

      info = sym->st_info & 0xf;
      if (info != STT_FUNC && info != STT_OBJECT)
	continue;
      if (sym->st_shndx == SHN_UNDEF)
	continue;
      if (sym->st_name >= strtab_size)
	{
	  error_callback (data, "symbol string index out of range", 0);
	  backtrace_free (state, elf_symbols, elf_symbol_size, error_callback,
			  data);
	  return 0;
	}
      elf_symbols[j].name = (const char *) strtab + sym->st_name;
      elf_symbols[j].address = sym->st_value + base_address;
      elf_symbols[j].size = sym->st_size;
      ++j;
    }

  backtrace_qsort (elf_symbols, elf_symbol_count, sizeof (struct elf_symbol),
		   elf_symbol_compare);

  sdata->next = NULL;
  sdata->symbols = elf_symbols;
  sdata->count = elf_symbol_count;

  return 1;
}

/* Add EDATA to the list in STATE.  */

static void
elf_add_syminfo_data (struct backtrace_state *state,
		      struct elf_syminfo_data *edata)
{
  if (!state->threaded)
    {
      struct elf_syminfo_data **pp;

      for (pp = (struct elf_syminfo_data **) (void *) &state->syminfo_data;
	   *pp != NULL;
	   pp = &(*pp)->next)
	;
      *pp = edata;
    }
  else
    {
      while (1)
	{
	  struct elf_syminfo_data **pp;

	  pp = (struct elf_syminfo_data **) (void *) &state->syminfo_data;

	  while (1)
	    {
	      struct elf_syminfo_data *p;

	      p = backtrace_atomic_load_pointer (pp);

	      if (p == NULL)
		break;

	      pp = &p->next;
	    }

	  if (__sync_bool_compare_and_swap (pp, NULL, edata))
	    break;
	}
    }
}

/* Return the symbol name and value for an ADDR.  */

void
elf_syminfo (struct backtrace_state *state, uintptr_t addr,
	     backtrace_syminfo_callback callback,
	     backtrace_error_callback error_callback ATTRIBUTE_UNUSED,
	     void *data)
{
  struct elf_syminfo_data *edata;
  struct elf_symbol *sym = NULL;

  if (!state->threaded)
    {
      for (edata = (struct elf_syminfo_data *) state->syminfo_data;
	   edata != NULL;
	   edata = edata->next)
	{
	  sym = ((struct elf_symbol *)
		 bsearch (&addr, edata->symbols, edata->count,
			  sizeof (struct elf_symbol), elf_symbol_search));
	  if (sym != NULL)
	    break;
	}
    }
  else
    {
      struct elf_syminfo_data **pp;

      pp = (struct elf_syminfo_data **) (void *) &state->syminfo_data;
      while (1)
	{
	  edata = backtrace_atomic_load_pointer (pp);
	  if (edata == NULL)
	    break;

	  sym = ((struct elf_symbol *)
		 bsearch (&addr, edata->symbols, edata->count,
			  sizeof (struct elf_symbol), elf_symbol_search));
	  if (sym != NULL)
	    break;

	  pp = &edata->next;
	}
    }

  if (sym == NULL)
    callback (data, addr, NULL, 0, 0);
  else
    callback (data, addr, sym->name, sym->address, sym->size);
}

/* Return whether FILENAME is a symlink.  */

static int
elf_is_symlink (const char *filename)
{
  struct stat st;

  if (lstat (filename, &st) < 0)
    return 0;
  return S_ISLNK (st.st_mode);
}

/* Return the results of reading the symlink FILENAME in a buffer
   allocated by backtrace_alloc.  Return the length of the buffer in
   *LEN.  */

static char *
elf_readlink (struct backtrace_state *state, const char *filename,
	      backtrace_error_callback error_callback, void *data,
	      size_t *plen)
{
  size_t len;
  char *buf;

  len = 128;
  while (1)
    {
      ssize_t rl;

      buf = backtrace_alloc (state, len, error_callback, data);
      if (buf == NULL)
	return NULL;
      rl = readlink (filename, buf, len);
      if (rl < 0)
	{
	  backtrace_free (state, buf, len, error_callback, data);
	  return NULL;
	}
      if ((size_t) rl < len - 1)
	{
	  buf[rl] = '\0';
	  *plen = len;
	  return buf;
	}
      backtrace_free (state, buf, len, error_callback, data);
      len *= 2;
    }
}

/* Open a separate debug info file, using the build ID to find it.
   Returns an open file descriptor, or -1.

   The GDB manual says that the only place gdb looks for a debug file
   when the build ID is known is in /usr/lib/debug/.build-id.  */

static int
elf_open_debugfile_by_buildid (struct backtrace_state *state,
			       const char *buildid_data, size_t buildid_size,
			       backtrace_error_callback error_callback,
			       void *data)
{
  const char * const prefix = "/usr/lib/debug/.build-id/";
  const size_t prefix_len = strlen (prefix);
  const char * const suffix = ".debug";
  const size_t suffix_len = strlen (suffix);
  size_t len;
  char *bd_filename;
  char *t;
  size_t i;
  int ret;
  int does_not_exist;

  len = prefix_len + buildid_size * 2 + suffix_len + 2;
  bd_filename = backtrace_alloc (state, len, error_callback, data);
  if (bd_filename == NULL)
    return -1;

  t = bd_filename;
  memcpy (t, prefix, prefix_len);
  t += prefix_len;
  for (i = 0; i < buildid_size; i++)
    {
      unsigned char b;
      unsigned char nib;

      b = (unsigned char) buildid_data[i];
      nib = (b & 0xf0) >> 4;
      *t++ = nib < 10 ? '0' + nib : 'a' + nib - 10;
      nib = b & 0x0f;
      *t++ = nib < 10 ? '0' + nib : 'a' + nib - 10;
      if (i == 0)
	*t++ = '/';
    }
  memcpy (t, suffix, suffix_len);
  t[suffix_len] = '\0';

  ret = backtrace_open (bd_filename, error_callback, data, &does_not_exist);

  backtrace_free (state, bd_filename, len, error_callback, data);

  /* gdb checks that the debuginfo file has the same build ID note.
     That seems kind of pointless to me--why would it have the right
     name but not the right build ID?--so skipping the check.  */

  return ret;
}

/* Try to open a file whose name is PREFIX (length PREFIX_LEN)
   concatenated with PREFIX2 (length PREFIX2_LEN) concatenated with
   DEBUGLINK_NAME.  Returns an open file descriptor, or -1.  */

static int
elf_try_debugfile (struct backtrace_state *state, const char *prefix,
		   size_t prefix_len, const char *prefix2, size_t prefix2_len,
		   const char *debuglink_name,
		   backtrace_error_callback error_callback, void *data)
{
  size_t debuglink_len;
  size_t try_len;
  char *try;
  int does_not_exist;
  int ret;

  debuglink_len = strlen (debuglink_name);
  try_len = prefix_len + prefix2_len + debuglink_len + 1;
  try = backtrace_alloc (state, try_len, error_callback, data);
  if (try == NULL)
    return -1;

  memcpy (try, prefix, prefix_len);
  memcpy (try + prefix_len, prefix2, prefix2_len);
  memcpy (try + prefix_len + prefix2_len, debuglink_name, debuglink_len);
  try[prefix_len + prefix2_len + debuglink_len] = '\0';

  ret = backtrace_open (try, error_callback, data, &does_not_exist);

  backtrace_free (state, try, try_len, error_callback, data);

  return ret;
}

/* Find a separate debug info file, using the debuglink section data
   to find it.  Returns an open file descriptor, or -1.  */

static int
elf_find_debugfile_by_debuglink (struct backtrace_state *state,
				 const char *filename,
				 const char *debuglink_name,
				 backtrace_error_callback error_callback,
				 void *data)
{
  int ret;
  char *alc;
  size_t alc_len;
  const char *slash;
  int ddescriptor;
  const char *prefix;
  size_t prefix_len;

  /* Resolve symlinks in FILENAME.  Since FILENAME is fairly likely to
     be /proc/self/exe, symlinks are common.  We don't try to resolve
     the whole path name, just the base name.  */
  ret = -1;
  alc = NULL;
  alc_len = 0;
  while (elf_is_symlink (filename))
    {
      char *new_buf;
      size_t new_len;

      new_buf = elf_readlink (state, filename, error_callback, data, &new_len);
      if (new_buf == NULL)
	break;

      if (new_buf[0] == '/')
	filename = new_buf;
      else
	{
	  slash = strrchr (filename, '/');
	  if (slash == NULL)
	    filename = new_buf;
	  else
	    {
	      size_t clen;
	      char *c;

	      slash++;
	      clen = slash - filename + strlen (new_buf) + 1;
	      c = backtrace_alloc (state, clen, error_callback, data);
	      if (c == NULL)
		goto done;

	      memcpy (c, filename, slash - filename);
	      memcpy (c + (slash - filename), new_buf, strlen (new_buf));
	      c[slash - filename + strlen (new_buf)] = '\0';
	      backtrace_free (state, new_buf, new_len, error_callback, data);
	      filename = c;
	      new_buf = c;
	      new_len = clen;
	    }
	}

      if (alc != NULL)
	backtrace_free (state, alc, alc_len, error_callback, data);
      alc = new_buf;
      alc_len = new_len;
    }

  /* Look for DEBUGLINK_NAME in the same directory as FILENAME.  */

  slash = strrchr (filename, '/');
  if (slash == NULL)
    {
      prefix = "";
      prefix_len = 0;
    }
  else
    {
      slash++;
      prefix = filename;
      prefix_len = slash - filename;
    }

  ddescriptor = elf_try_debugfile (state, prefix, prefix_len, "", 0,
				   debuglink_name, error_callback, data);
  if (ddescriptor >= 0)
    {
      ret = ddescriptor;
      goto done;
    }

  /* Look for DEBUGLINK_NAME in a .debug subdirectory of FILENAME.  */

  ddescriptor = elf_try_debugfile (state, prefix, prefix_len, ".debug/",
				   strlen (".debug/"), debuglink_name,
				   error_callback, data);
  if (ddescriptor >= 0)
    {
      ret = ddescriptor;
      goto done;
    }

  /* Look for DEBUGLINK_NAME in /usr/lib/debug.  */

  ddescriptor = elf_try_debugfile (state, "/usr/lib/debug/",
				   strlen ("/usr/lib/debug/"), prefix,
				   prefix_len, debuglink_name,
				   error_callback, data);
  if (ddescriptor >= 0)
    ret = ddescriptor;

 done:
  if (alc != NULL && alc_len > 0)
    backtrace_free (state, alc, alc_len, error_callback, data);
  return ret;
}

/* Open a separate debug info file, using the debuglink section data
   to find it.  Returns an open file descriptor, or -1.  */

static int
elf_open_debugfile_by_debuglink (struct backtrace_state *state,
				 const char *filename,
				 const char *debuglink_name,
				 uint32_t debuglink_crc,
				 backtrace_error_callback error_callback,
				 void *data)
{
  int ddescriptor;
  uint32_t got_crc;

  ddescriptor = elf_find_debugfile_by_debuglink (state, filename,
						 debuglink_name,
						 error_callback, data);
  if (ddescriptor < 0)
    return -1;

  // HEAPTRACK: only compare crc if available
  got_crc = debuglink_crc ? elf_crc32_file (state, ddescriptor, error_callback, data) : 0;
  if (got_crc != debuglink_crc)
    {
      backtrace_close (ddescriptor, error_callback, data);
      return -1;
    }

  return ddescriptor;
}

/* A function useful for setting a breakpoint for an inflation failure
   when this code is compiled with -g.  */

static void
elf_zlib_failed(void)
{
}

/* *PVAL is the current value being read from the stream, and *PBITS
   is the number of valid bits.  Ensure that *PVAL holds at least 15
   bits by reading additional bits from *PPIN, up to PINEND, as
   needed.  Updates *PPIN, *PVAL and *PBITS.  Returns 1 on success, 0
   on error.  */

static int
elf_zlib_fetch (const unsigned char **ppin, const unsigned char *pinend,
		uint64_t *pval, unsigned int *pbits)
{
  unsigned int bits;
  const unsigned char *pin;
  uint64_t val;
  uint32_t next;

  bits = *pbits;
  if (bits >= 15)
    return 1;
  pin = *ppin;
  val = *pval;

  if (unlikely (pinend - pin < 4))
    {
      elf_zlib_failed ();
      return 0;
    }

  /* We've ensured that PIN is aligned.  */
  next = *(const uint32_t *)pin;

#if __BYTE_ORDER == __ORDER_BIG_ENDIAN
  next = __builtin_bswap32 (next);
#endif

  val |= (uint64_t)next << bits;
  bits += 32;
  pin += 4;

  /* We will need the next four bytes soon.  */
  __builtin_prefetch (pin, 0, 0);

  *ppin = pin;
  *pval = val;
  *pbits = bits;
  return 1;
}

/* Huffman code tables, like the rest of the zlib format, are defined
   by RFC 1951.  We store a Huffman code table as a series of tables
   stored sequentially in memory.  Each entry in a table is 16 bits.
   The first, main, table has 256 entries.  It is followed by a set of
   secondary tables of length 2 to 128 entries.  The maximum length of
   a code sequence in the deflate format is 15 bits, so that is all we
   need.  Each secondary table has an index, which is the offset of
   the table in the overall memory storage.

   The deflate format says that all codes of a given bit length are
   lexicographically consecutive.  Perhaps we could have 130 values
   that require a 15-bit code, perhaps requiring three secondary
   tables of size 128.  I don't know if this is actually possible, but
   it suggests that the maximum size required for secondary tables is
   3 * 128 + 3 * 64 ... == 768.  The zlib enough program reports 660
   as the maximum.  We permit 768, since in addition to the 256 for
   the primary table, with two bytes per entry, and with the two
   tables we need, that gives us a page.

   A single table entry needs to store a value or (for the main table
   only) the index and size of a secondary table.  Values range from 0
   to 285, inclusive.  Secondary table indexes, per above, range from
   0 to 510.  For a value we need to store the number of bits we need
   to determine that value (one value may appear multiple times in the
   table), which is 1 to 8.  For a secondary table we need to store
   the number of bits used to index into the table, which is 1 to 7.
   And of course we need 1 bit to decide whether we have a value or a
   secondary table index.  So each entry needs 9 bits for value/table
   index, 3 bits for size, 1 bit what it is.  For simplicity we use 16
   bits per entry.  */

/* Number of entries we allocate to for one code table.  We get a page
   for the two code tables we need.  */

#define HUFFMAN_TABLE_SIZE (1024)

/* Bit masks and shifts for the values in the table.  */

#define HUFFMAN_VALUE_MASK 0x01ff
#define HUFFMAN_BITS_SHIFT 9
#define HUFFMAN_BITS_MASK 0x7
#define HUFFMAN_SECONDARY_SHIFT 12

/* For working memory while inflating we need two code tables, we need
   an array of code lengths (max value 15, so we use unsigned char),
   and an array of unsigned shorts used while building a table.  The
   latter two arrays must be large enough to hold the maximum number
   of code lengths, which RFC 1951 defines as 286 + 30.  */

#define ZDEBUG_TABLE_SIZE \
  (2 * HUFFMAN_TABLE_SIZE * sizeof (uint16_t) \
   + (286 + 30) * sizeof (uint16_t)	      \
   + (286 + 30) * sizeof (unsigned char))

#define ZDEBUG_TABLE_CODELEN_OFFSET \
  (2 * HUFFMAN_TABLE_SIZE * sizeof (uint16_t) \
   + (286 + 30) * sizeof (uint16_t))

#define ZDEBUG_TABLE_WORK_OFFSET \
  (2 * HUFFMAN_TABLE_SIZE * sizeof (uint16_t))

#ifdef BACKTRACE_GENERATE_FIXED_HUFFMAN_TABLE

/* Used by the main function that generates the fixed table to learn
   the table size.  */
static size_t final_next_secondary;

#endif

/* Build a Huffman code table from an array of lengths in CODES of
   length CODES_LEN.  The table is stored into *TABLE.  ZDEBUG_TABLE
   is the same as for elf_zlib_inflate, used to find some work space.
   Returns 1 on success, 0 on error.  */

static int
elf_zlib_inflate_table (unsigned char *codes, size_t codes_len,
			uint16_t *zdebug_table, uint16_t *table)
{
  uint16_t count[16];
  uint16_t start[16];
  uint16_t prev[16];
  uint16_t firstcode[7];
  uint16_t *next;
  size_t i;
  size_t j;
  unsigned int code;
  size_t next_secondary;

  /* Count the number of code of each length.  Set NEXT[val] to be the
     next value after VAL with the same bit length.  */

  next = (uint16_t *) (((unsigned char *) zdebug_table)
		       + ZDEBUG_TABLE_WORK_OFFSET);

  memset (&count[0], 0, 16 * sizeof (uint16_t));
  for (i = 0; i < codes_len; ++i)
    {
      if (unlikely (codes[i] >= 16))
	{
	  elf_zlib_failed ();
	  return 0;
	}

      if (count[codes[i]] == 0)
	{
	  start[codes[i]] = i;
	  prev[codes[i]] = i;
	}
      else
	{
	  next[prev[codes[i]]] = i;
	  prev[codes[i]] = i;
	}

      ++count[codes[i]];
    }

  /* For each length, fill in the table for the codes of that
     length.  */

  memset (table, 0, HUFFMAN_TABLE_SIZE * sizeof (uint16_t));

  /* Handle the values that do not require a secondary table.  */

  code = 0;
  for (j = 1; j <= 8; ++j)
    {
      unsigned int jcnt;
      unsigned int val;

      jcnt = count[j];
      if (jcnt == 0)
	continue;

      if (unlikely (jcnt > (1U << j)))
	{
	  elf_zlib_failed ();
	  return 0;
	}

      /* There are JCNT values that have this length, the values
	 starting from START[j] continuing through NEXT[VAL].  Those
	 values are assigned consecutive values starting at CODE.  */

      val = start[j];
      for (i = 0; i < jcnt; ++i)
	{
	  uint16_t tval;
	  size_t ind;
	  unsigned int incr;

	  /* In the compressed bit stream, the value VAL is encoded as
	     J bits with the value C.  */

	  if (unlikely ((val & ~HUFFMAN_VALUE_MASK) != 0))
	    {
	      elf_zlib_failed ();
	      return 0;
	    }

	  tval = val | ((j - 1) << HUFFMAN_BITS_SHIFT);

	  /* The table lookup uses 8 bits.  If J is less than 8, we
	     don't know what the other bits will be.  We need to fill
	     in all possibilities in the table.  Since the Huffman
	     code is unambiguous, those entries can't be used for any
	     other code.  */

	  for (ind = code; ind < 0x100; ind += 1 << j)
	    {
	      if (unlikely (table[ind] != 0))
		{
		  elf_zlib_failed ();
		  return 0;
		}
	      table[ind] = tval;
	    }

	  /* Advance to the next value with this length.  */
	  if (i + 1 < jcnt)
	    val = next[val];

	  /* The Huffman codes are stored in the bitstream with the
	     most significant bit first, as is required to make them
	     unambiguous.  The effect is that when we read them from
	     the bitstream we see the bit sequence in reverse order:
	     the most significant bit of the Huffman code is the least
	     significant bit of the value we read from the bitstream.
	     That means that to make our table lookups work, we need
	     to reverse the bits of CODE.  Since reversing bits is
	     tedious and in general requires using a table, we instead
	     increment CODE in reverse order.  That is, if the number
	     of bits we are currently using, here named J, is 3, we
	     count as 000, 100, 010, 110, 001, 101, 011, 111, which is
	     to say the numbers from 0 to 7 but with the bits
	     reversed.  Going to more bits, aka incrementing J,
	     effectively just adds more zero bits as the beginning,
	     and as such does not change the numeric value of CODE.

	     To increment CODE of length J in reverse order, find the
	     most significant zero bit and set it to one while
	     clearing all higher bits.  In other words, add 1 modulo
	     2^J, only reversed.  */

	  incr = 1U << (j - 1);
	  while ((code & incr) != 0)
	    incr >>= 1;
	  if (incr == 0)
	    code = 0;
	  else
	    {
	      code &= incr - 1;
	      code += incr;
	    }
	}
    }

  /* Handle the values that require a secondary table.  */

  /* Set FIRSTCODE, the number at which the codes start, for each
     length.  */

  for (j = 9; j < 16; j++)
    {
      unsigned int jcnt;
      unsigned int k;

      jcnt = count[j];
      if (jcnt == 0)
	continue;

      /* There are JCNT values that have this length, the values
	 starting from START[j].  Those values are assigned
	 consecutive values starting at CODE.  */

      firstcode[j - 9] = code;

      /* Reverse add JCNT to CODE modulo 2^J.  */
      for (k = 0; k < j; ++k)
	{
	  if ((jcnt & (1U << k)) != 0)
	    {
	      unsigned int m;
	      unsigned int bit;

	      bit = 1U << (j - k - 1);
	      for (m = 0; m < j - k; ++m, bit >>= 1)
		{
		  if ((code & bit) == 0)
		    {
		      code += bit;
		      break;
		    }
		  code &= ~bit;
		}
	      jcnt &= ~(1U << k);
	    }
	}
      if (unlikely (jcnt != 0))
	{
	  elf_zlib_failed ();
	  return 0;
	}
    }

  /* For J from 9 to 15, inclusive, we store COUNT[J] consecutive
     values starting at START[J] with consecutive codes starting at
     FIRSTCODE[J - 9].  In the primary table we need to point to the
     secondary table, and the secondary table will be indexed by J - 9
     bits.  We count down from 15 so that we install the larger
     secondary tables first, as the smaller ones may be embedded in
     the larger ones.  */

  next_secondary = 0; /* Index of next secondary table (after primary).  */
  for (j = 15; j >= 9; j--)
    {
      unsigned int jcnt;
      unsigned int val;
      size_t primary; /* Current primary index.  */
      size_t secondary; /* Offset to current secondary table.  */
      size_t secondary_bits; /* Bit size of current secondary table.  */

      jcnt = count[j];
      if (jcnt == 0)
	continue;

      val = start[j];
      code = firstcode[j - 9];
      primary = 0x100;
      secondary = 0;
      secondary_bits = 0;
      for (i = 0; i < jcnt; ++i)
	{
	  uint16_t tval;
	  size_t ind;
	  unsigned int incr;

	  if ((code & 0xff) != primary)
	    {
	      uint16_t tprimary;

	      /* Fill in a new primary table entry.  */

	      primary = code & 0xff;

	      tprimary = table[primary];
	      if (tprimary == 0)
		{
		  /* Start a new secondary table.  */

		  if (unlikely ((next_secondary & HUFFMAN_VALUE_MASK)
				!= next_secondary))
		    {
		      elf_zlib_failed ();
		      return 0;
		    }

		  secondary = next_secondary;
		  secondary_bits = j - 8;
		  next_secondary += 1 << secondary_bits;
		  table[primary] = (secondary
				    + ((j - 8) << HUFFMAN_BITS_SHIFT)
				    + (1U << HUFFMAN_SECONDARY_SHIFT));
		}
	      else
		{
		  /* There is an existing entry.  It had better be a
		     secondary table with enough bits.  */
		  if (unlikely ((tprimary & (1U << HUFFMAN_SECONDARY_SHIFT))
				== 0))
		    {
		      elf_zlib_failed ();
		      return 0;
		    }
		  secondary = tprimary & HUFFMAN_VALUE_MASK;
		  secondary_bits = ((tprimary >> HUFFMAN_BITS_SHIFT)
				    & HUFFMAN_BITS_MASK);
		  if (unlikely (secondary_bits < j - 8))
		    {
		      elf_zlib_failed ();
		      return 0;
		    }
		}
	    }

	  /* Fill in secondary table entries.  */

	  tval = val | ((j - 8) << HUFFMAN_BITS_SHIFT);

	  for (ind = code >> 8;
	       ind < (1U << secondary_bits);
	       ind += 1U << (j - 8))
	    {
	      if (unlikely (table[secondary + 0x100 + ind] != 0))
		{
		  elf_zlib_failed ();
		  return 0;
		}
	      table[secondary + 0x100 + ind] = tval;
	    }

	  if (i + 1 < jcnt)
	    val = next[val];

	  incr = 1U << (j - 1);
	  while ((code & incr) != 0)
	    incr >>= 1;
	  if (incr == 0)
	    code = 0;
	  else
	    {
	      code &= incr - 1;
	      code += incr;
	    }
	}
    }

#ifdef BACKTRACE_GENERATE_FIXED_HUFFMAN_TABLE
  final_next_secondary = next_secondary;
#endif

  return 1;
}

#ifdef BACKTRACE_GENERATE_FIXED_HUFFMAN_TABLE

/* Used to generate the fixed Huffman table for block type 1.  */

#include <stdio.h>

static uint16_t table[ZDEBUG_TABLE_SIZE];
static unsigned char codes[287];

int
main ()
{
  size_t i;

  for (i = 0; i <= 143; ++i)
    codes[i] = 8;
  for (i = 144; i <= 255; ++i)
    codes[i] = 9;
  for (i = 256; i <= 279; ++i)
    codes[i] = 7;
  for (i = 280; i <= 287; ++i)
    codes[i] = 8;
  if (!elf_zlib_inflate_table (&codes[0], 287, &table[0], &table[0]))
    {
      fprintf (stderr, "elf_zlib_inflate_table failed\n");
      exit (EXIT_FAILURE);
    }

  printf ("static const uint16_t elf_zlib_default_table[%#zx] =\n",
	  final_next_secondary + 0x100);
  printf ("{\n");
  for (i = 0; i < final_next_secondary + 0x100; i += 8)
    {
      size_t j;

      printf (" ");
      for (j = i; j < final_next_secondary + 0x100 && j < i + 8; ++j)
	printf (" %#x,", table[j]);
      printf ("\n");
    }
  printf ("};\n");
  return 0;
}

#endif

/* The fixed table generated by the #ifdef'ed out main function
   above.  */

static const uint16_t elf_zlib_default_table[0x170] =
{
  0xd00, 0xe50, 0xe10, 0xf18, 0xd10, 0xe70, 0xe30, 0x1232,
  0xd08, 0xe60, 0xe20, 0x1212, 0xe00, 0xe80, 0xe40, 0x1252,
  0xd04, 0xe58, 0xe18, 0x1202, 0xd14, 0xe78, 0xe38, 0x1242,
  0xd0c, 0xe68, 0xe28, 0x1222, 0xe08, 0xe88, 0xe48, 0x1262,
  0xd02, 0xe54, 0xe14, 0xf1c, 0xd12, 0xe74, 0xe34, 0x123a,
  0xd0a, 0xe64, 0xe24, 0x121a, 0xe04, 0xe84, 0xe44, 0x125a,
  0xd06, 0xe5c, 0xe1c, 0x120a, 0xd16, 0xe7c, 0xe3c, 0x124a,
  0xd0e, 0xe6c, 0xe2c, 0x122a, 0xe0c, 0xe8c, 0xe4c, 0x126a,
  0xd01, 0xe52, 0xe12, 0xf1a, 0xd11, 0xe72, 0xe32, 0x1236,
  0xd09, 0xe62, 0xe22, 0x1216, 0xe02, 0xe82, 0xe42, 0x1256,
  0xd05, 0xe5a, 0xe1a, 0x1206, 0xd15, 0xe7a, 0xe3a, 0x1246,
  0xd0d, 0xe6a, 0xe2a, 0x1226, 0xe0a, 0xe8a, 0xe4a, 0x1266,
  0xd03, 0xe56, 0xe16, 0xf1e, 0xd13, 0xe76, 0xe36, 0x123e,
  0xd0b, 0xe66, 0xe26, 0x121e, 0xe06, 0xe86, 0xe46, 0x125e,
  0xd07, 0xe5e, 0xe1e, 0x120e, 0xd17, 0xe7e, 0xe3e, 0x124e,
  0xd0f, 0xe6e, 0xe2e, 0x122e, 0xe0e, 0xe8e, 0xe4e, 0x126e,
  0xd00, 0xe51, 0xe11, 0xf19, 0xd10, 0xe71, 0xe31, 0x1234,
  0xd08, 0xe61, 0xe21, 0x1214, 0xe01, 0xe81, 0xe41, 0x1254,
  0xd04, 0xe59, 0xe19, 0x1204, 0xd14, 0xe79, 0xe39, 0x1244,
  0xd0c, 0xe69, 0xe29, 0x1224, 0xe09, 0xe89, 0xe49, 0x1264,
  0xd02, 0xe55, 0xe15, 0xf1d, 0xd12, 0xe75, 0xe35, 0x123c,
  0xd0a, 0xe65, 0xe25, 0x121c, 0xe05, 0xe85, 0xe45, 0x125c,
  0xd06, 0xe5d, 0xe1d, 0x120c, 0xd16, 0xe7d, 0xe3d, 0x124c,
  0xd0e, 0xe6d, 0xe2d, 0x122c, 0xe0d, 0xe8d, 0xe4d, 0x126c,
  0xd01, 0xe53, 0xe13, 0xf1b, 0xd11, 0xe73, 0xe33, 0x1238,
  0xd09, 0xe63, 0xe23, 0x1218, 0xe03, 0xe83, 0xe43, 0x1258,
  0xd05, 0xe5b, 0xe1b, 0x1208, 0xd15, 0xe7b, 0xe3b, 0x1248,
  0xd0d, 0xe6b, 0xe2b, 0x1228, 0xe0b, 0xe8b, 0xe4b, 0x1268,
  0xd03, 0xe57, 0xe17, 0x1200, 0xd13, 0xe77, 0xe37, 0x1240,
  0xd0b, 0xe67, 0xe27, 0x1220, 0xe07, 0xe87, 0xe47, 0x1260,
  0xd07, 0xe5f, 0xe1f, 0x1210, 0xd17, 0xe7f, 0xe3f, 0x1250,
  0xd0f, 0xe6f, 0xe2f, 0x1230, 0xe0f, 0xe8f, 0xe4f, 0,
  0x290, 0x291, 0x292, 0x293, 0x294, 0x295, 0x296, 0x297,
  0x298, 0x299, 0x29a, 0x29b, 0x29c, 0x29d, 0x29e, 0x29f,
  0x2a0, 0x2a1, 0x2a2, 0x2a3, 0x2a4, 0x2a5, 0x2a6, 0x2a7,
  0x2a8, 0x2a9, 0x2aa, 0x2ab, 0x2ac, 0x2ad, 0x2ae, 0x2af,
  0x2b0, 0x2b1, 0x2b2, 0x2b3, 0x2b4, 0x2b5, 0x2b6, 0x2b7,
  0x2b8, 0x2b9, 0x2ba, 0x2bb, 0x2bc, 0x2bd, 0x2be, 0x2bf,
  0x2c0, 0x2c1, 0x2c2, 0x2c3, 0x2c4, 0x2c5, 0x2c6, 0x2c7,
  0x2c8, 0x2c9, 0x2ca, 0x2cb, 0x2cc, 0x2cd, 0x2ce, 0x2cf,
  0x2d0, 0x2d1, 0x2d2, 0x2d3, 0x2d4, 0x2d5, 0x2d6, 0x2d7,
  0x2d8, 0x2d9, 0x2da, 0x2db, 0x2dc, 0x2dd, 0x2de, 0x2df,
  0x2e0, 0x2e1, 0x2e2, 0x2e3, 0x2e4, 0x2e5, 0x2e6, 0x2e7,
  0x2e8, 0x2e9, 0x2ea, 0x2eb, 0x2ec, 0x2ed, 0x2ee, 0x2ef,
  0x2f0, 0x2f1, 0x2f2, 0x2f3, 0x2f4, 0x2f5, 0x2f6, 0x2f7,
  0x2f8, 0x2f9, 0x2fa, 0x2fb, 0x2fc, 0x2fd, 0x2fe, 0x2ff,
};

/* Inflate a zlib stream from PIN/SIN to POUT/SOUT.  Return 1 on
   success, 0 on some error parsing the stream.  */

static int
elf_zlib_inflate (const unsigned char *pin, size_t sin, uint16_t *zdebug_table,
		  unsigned char *pout, size_t sout)
{
  unsigned char *porigout;
  const unsigned char *pinend;
  unsigned char *poutend;

  /* We can apparently see multiple zlib streams concatenated
     together, so keep going as long as there is something to read.
     The last 4 bytes are the checksum.  */
  porigout = pout;
  pinend = pin + sin;
  poutend = pout + sout;
  while ((pinend - pin) > 4)
    {
      uint64_t val;
      unsigned int bits;
      int last;

      /* Read the two byte zlib header.  */

      if (unlikely ((pin[0] & 0xf) != 8)) /* 8 is zlib encoding.  */
	{
	  /* Unknown compression method.  */
	  elf_zlib_failed ();
	  return 0;
	}
      if (unlikely ((pin[0] >> 4) > 7))
	{
	  /* Window size too large.  Other than this check, we don't
	     care about the window size.  */
	  elf_zlib_failed ();
	  return 0;
	}
      if (unlikely ((pin[1] & 0x20) != 0))
	{
	  /* Stream expects a predefined dictionary, but we have no
	     dictionary.  */
	  elf_zlib_failed ();
	  return 0;
	}
      val = (pin[0] << 8) | pin[1];
      if (unlikely (val % 31 != 0))
	{
	  /* Header check failure.  */
	  elf_zlib_failed ();
	  return 0;
	}
      pin += 2;

      /* Align PIN to a 32-bit boundary.  */

      val = 0;
      bits = 0;
      while ((((uintptr_t) pin) & 3) != 0)
	{
	  val |= (uint64_t)*pin << bits;
	  bits += 8;
	  ++pin;
	}

      /* Read blocks until one is marked last.  */

      last = 0;

      while (!last)
	{
	  unsigned int type;
	  const uint16_t *tlit;
	  const uint16_t *tdist;

	  if (!elf_zlib_fetch (&pin, pinend, &val, &bits))
	    return 0;

	  last = val & 1;
	  type = (val >> 1) & 3;
	  val >>= 3;
	  bits -= 3;

	  if (unlikely (type == 3))
	    {
	      /* Invalid block type.  */
	      elf_zlib_failed ();
	      return 0;
	    }

	  if (type == 0)
	    {
	      uint16_t len;
	      uint16_t lenc;

	      /* An uncompressed block.  */

	      /* If we've read ahead more than a byte, back up.  */
	      while (bits > 8)
		{
		  --pin;
		  bits -= 8;
		}

	      val = 0;
	      bits = 0;
	      if (unlikely ((pinend - pin) < 4))
		{
		  /* Missing length.  */
		  elf_zlib_failed ();
		  return 0;
		}
	      len = pin[0] | (pin[1] << 8);
	      lenc = pin[2] | (pin[3] << 8);
	      pin += 4;
	      lenc = ~lenc;
	      if (unlikely (len != lenc))
		{
		  /* Corrupt data.  */
		  elf_zlib_failed ();
		  return 0;
		}
	      if (unlikely (len > (unsigned int) (pinend - pin)
			    || len > (unsigned int) (poutend - pout)))
		{
		  /* Not enough space in buffers.  */
		  elf_zlib_failed ();
		  return 0;
		}
	      memcpy (pout, pin, len);
	      pout += len;
	      pin += len;

	      /* Align PIN.  */
	      while ((((uintptr_t) pin) & 3) != 0)
		{
		  val |= (uint64_t)*pin << bits;
		  bits += 8;
		  ++pin;
		}

	      /* Go around to read the next block.  */
	      continue;
	    }

	  if (type == 1)
	    {
	      tlit = elf_zlib_default_table;
	      tdist = elf_zlib_default_table;
	    }
	  else
	    {
	      unsigned int nlit;
	      unsigned int ndist;
	      unsigned int nclen;
	      unsigned char codebits[19];
	      unsigned char *plenbase;
	      unsigned char *plen;
	      unsigned char *plenend;

	      /* Read a Huffman encoding table.  The various magic
		 numbers here are from RFC 1951.  */

	      if (!elf_zlib_fetch (&pin, pinend, &val, &bits))
		return 0;

	      nlit = (val & 0x1f) + 257;
	      val >>= 5;
	      ndist = (val & 0x1f) + 1;
	      val >>= 5;
	      nclen = (val & 0xf) + 4;
	      val >>= 4;
	      bits -= 14;
	      if (unlikely (nlit > 286 || ndist > 30))
		{
		  /* Values out of range.  */
		  elf_zlib_failed ();
		  return 0;
		}

	      /* Read and build the table used to compress the
		 literal, length, and distance codes.  */

	      memset(&codebits[0], 0, 19);

	      /* There are always at least 4 elements in the
		 table.  */

	      if (!elf_zlib_fetch (&pin, pinend, &val, &bits))
		return 0;

	      codebits[16] = val & 7;
	      codebits[17] = (val >> 3) & 7;
	      codebits[18] = (val >> 6) & 7;
	      codebits[0] = (val >> 9) & 7;
	      val >>= 12;
	      bits -= 12;

	      if (nclen == 4)
		goto codebitsdone;

	      codebits[8] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 5)
		goto codebitsdone;

	      if (!elf_zlib_fetch (&pin, pinend, &val, &bits))
		return 0;

	      codebits[7] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 6)
		goto codebitsdone;

	      codebits[9] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 7)
		goto codebitsdone;

	      codebits[6] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 8)
		goto codebitsdone;

	      codebits[10] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 9)
		goto codebitsdone;

	      codebits[5] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 10)
		goto codebitsdone;

	      if (!elf_zlib_fetch (&pin, pinend, &val, &bits))
		return 0;

	      codebits[11] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 11)
		goto codebitsdone;

	      codebits[4] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 12)
		goto codebitsdone;

	      codebits[12] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 13)
		goto codebitsdone;

	      codebits[3] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 14)
		goto codebitsdone;

	      codebits[13] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 15)
		goto codebitsdone;

	      if (!elf_zlib_fetch (&pin, pinend, &val, &bits))
		return 0;

	      codebits[2] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 16)
		goto codebitsdone;

	      codebits[14] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 17)
		goto codebitsdone;

	      codebits[1] = val & 7;
	      val >>= 3;
	      bits -= 3;

	      if (nclen == 18)
		goto codebitsdone;

	      codebits[15] = val & 7;
	      val >>= 3;
	      bits -= 3;

	    codebitsdone:

	      if (!elf_zlib_inflate_table (codebits, 19, zdebug_table,
					   zdebug_table))
		return 0;

	      /* Read the compressed bit lengths of the literal,
		 length, and distance codes.  We have allocated space
		 at the end of zdebug_table to hold them.  */

	      plenbase = (((unsigned char *) zdebug_table)
			  + ZDEBUG_TABLE_CODELEN_OFFSET);
	      plen = plenbase;
	      plenend = plen + nlit + ndist;
	      while (plen < plenend)
		{
		  uint16_t t;
		  unsigned int b;
		  uint16_t v;

		  if (!elf_zlib_fetch (&pin, pinend, &val, &bits))
		    return 0;

		  t = zdebug_table[val & 0xff];

		  /* The compression here uses bit lengths up to 7, so
		     a secondary table is never necessary.  */
		  if (unlikely ((t & (1U << HUFFMAN_SECONDARY_SHIFT)) != 0))
		    {
		      elf_zlib_failed ();
		      return 0;
		    }

		  b = (t >> HUFFMAN_BITS_SHIFT) & HUFFMAN_BITS_MASK;
		  val >>= b + 1;
		  bits -= b + 1;

		  v = t & HUFFMAN_VALUE_MASK;
		  if (v < 16)
		    *plen++ = v;
		  else if (v == 16)
		    {
		      unsigned int c;
		      unsigned int prev;

		      /* Copy previous entry 3 to 6 times.  */

		      if (unlikely (plen == plenbase))
			{
			  elf_zlib_failed ();
			  return 0;
			}

		      /* We used up to 7 bits since the last
			 elf_zlib_fetch, so we have at least 8 bits
			 available here.  */

		      c = 3 + (val & 0x3);
		      val >>= 2;
		      bits -= 2;
		      if (unlikely ((unsigned int) (plenend - plen) < c))
			{
			  elf_zlib_failed ();
			  return 0;
			}

		      prev = plen[-1];
		      switch (c)
			{
			case 6:
			  *plen++ = prev;
			  /* fallthrough */
			case 5:
			  *plen++ = prev;
			  /* fallthrough */
			case 4:
			  *plen++ = prev;
			}
		      *plen++ = prev;
		      *plen++ = prev;
		      *plen++ = prev;
		    }
		  else if (v == 17)
		    {
		      unsigned int c;

		      /* Store zero 3 to 10 times.  */

		      /* We used up to 7 bits since the last
			 elf_zlib_fetch, so we have at least 8 bits
			 available here.  */

		      c = 3 + (val & 0x7);
		      val >>= 3;
		      bits -= 3;
		      if (unlikely ((unsigned int) (plenend - plen) < c))
			{
			  elf_zlib_failed ();
			  return 0;
			}

		      switch (c)
			{
			case 10:
			  *plen++ = 0;
			  /* fallthrough */
			case 9:
			  *plen++ = 0;
			  /* fallthrough */
			case 8:
			  *plen++ = 0;
			  /* fallthrough */
			case 7:
			  *plen++ = 0;
			  /* fallthrough */
			case 6:
			  *plen++ = 0;
			  /* fallthrough */
			case 5:
			  *plen++ = 0;
			  /* fallthrough */
			case 4:
			  *plen++ = 0;
			}
		      *plen++ = 0;
		      *plen++ = 0;
		      *plen++ = 0;
		    }
		  else if (v == 18)
		    {
		      unsigned int c;

		      /* Store zero 11 to 138 times.  */

		      /* We used up to 7 bits since the last
			 elf_zlib_fetch, so we have at least 8 bits
			 available here.  */

		      c = 11 + (val & 0x7f);
		      val >>= 7;
		      bits -= 7;
		      if (unlikely ((unsigned int) (plenend - plen) < c))
			{
			  elf_zlib_failed ();
			  return 0;
			}

		      memset (plen, 0, c);
		      plen += c;
		    }
		  else
		    {
		      elf_zlib_failed ();
		      return 0;
		    }
		}

	      /* Make sure that the stop code can appear.  */

	      plen = plenbase;
	      if (unlikely (plen[256] == 0))
		{
		  elf_zlib_failed ();
		  return 0;
		}

	      /* Build the decompression tables.  */

	      if (!elf_zlib_inflate_table (plen, nlit, zdebug_table,
					   zdebug_table))
		return 0;
	      if (!elf_zlib_inflate_table (plen + nlit, ndist, zdebug_table,
					   zdebug_table + HUFFMAN_TABLE_SIZE))
		return 0;
	      tlit = zdebug_table;
	      tdist = zdebug_table + HUFFMAN_TABLE_SIZE;
	    }

	  /* Inflate values until the end of the block.  This is the
	     main loop of the inflation code.  */

	  while (1)
	    {
	      uint16_t t;
	      unsigned int b;
	      uint16_t v;
	      unsigned int lit;

	      if (!elf_zlib_fetch (&pin, pinend, &val, &bits))
		return 0;

	      t = tlit[val & 0xff];
	      b = (t >> HUFFMAN_BITS_SHIFT) & HUFFMAN_BITS_MASK;
	      v = t & HUFFMAN_VALUE_MASK;

	      if ((t & (1U << HUFFMAN_SECONDARY_SHIFT)) == 0)
		{
		  lit = v;
		  val >>= b + 1;
		  bits -= b + 1;
		}
	      else
		{
		  t = tlit[v + 0x100 + ((val >> 8) & ((1U << b) - 1))];
		  b = (t >> HUFFMAN_BITS_SHIFT) & HUFFMAN_BITS_MASK;
		  lit = t & HUFFMAN_VALUE_MASK;
		  val >>= b + 8;
		  bits -= b + 8;
		}

	      if (lit < 256)
		{
		  if (unlikely (pout == poutend))
		    {
		      elf_zlib_failed ();
		      return 0;
		    }

		  *pout++ = lit;

		  /* We will need to write the next byte soon.  We ask
		     for high temporal locality because we will write
		     to the whole cache line soon.  */
		  __builtin_prefetch (pout, 1, 3);
		}
	      else if (lit == 256)
		{
		  /* The end of the block.  */
		  break;
		}
	      else
		{
		  unsigned int dist;
		  unsigned int len;

		  /* Convert lit into a length.  */

		  if (lit < 265)
		    len = lit - 257 + 3;
		  else if (lit == 285)
		    len = 258;
		  else if (unlikely (lit > 285))
		    {
		      elf_zlib_failed ();
		      return 0;
		    }
		  else
		    {
		      unsigned int extra;

		      if (!elf_zlib_fetch (&pin, pinend, &val, &bits))
			return 0;

		      /* This is an expression for the table of length
			 codes in RFC 1951 3.2.5.  */
		      lit -= 265;
		      extra = (lit >> 2) + 1;
		      len = (lit & 3) << extra;
		      len += 11;
		      len += ((1U << (extra - 1)) - 1) << 3;
		      len += val & ((1U << extra) - 1);
		      val >>= extra;
		      bits -= extra;
		    }

		  if (!elf_zlib_fetch (&pin, pinend, &val, &bits))
		    return 0;

		  t = tdist[val & 0xff];
		  b = (t >> HUFFMAN_BITS_SHIFT) & HUFFMAN_BITS_MASK;
		  v = t & HUFFMAN_VALUE_MASK;

		  if ((t & (1U << HUFFMAN_SECONDARY_SHIFT)) == 0)
		    {
		      dist = v;
		      val >>= b + 1;
		      bits -= b + 1;
		    }
		  else
		    {
		      t = tdist[v + 0x100 + ((val >> 8) & ((1U << b) - 1))];
		      b = (t >> HUFFMAN_BITS_SHIFT) & HUFFMAN_BITS_MASK;
		      dist = t & HUFFMAN_VALUE_MASK;
		      val >>= b + 8;
		      bits -= b + 8;
		    }

		  /* Convert dist to a distance.  */

		  if (dist == 0)
		    {
		      /* A distance of 1.  A common case, meaning
			 repeat the last character LEN times.  */

		      if (unlikely (pout == porigout))
			{
			  elf_zlib_failed ();
			  return 0;
			}

		      if (unlikely ((unsigned int) (poutend - pout) < len))
			{
			  elf_zlib_failed ();
			  return 0;
			}

		      memset (pout, pout[-1], len);
		      pout += len;
		    }
		  else if (unlikely (dist > 29))
		    {
		      elf_zlib_failed ();
		      return 0;
		    }
		  else
		    {
		      if (dist < 4)
			dist = dist + 1;
		      else
			{
			  unsigned int extra;

			  if (!elf_zlib_fetch (&pin, pinend, &val, &bits))
			    return 0;

			  /* This is an expression for the table of
			     distance codes in RFC 1951 3.2.5.  */
			  dist -= 4;
			  extra = (dist >> 1) + 1;
			  dist = (dist & 1) << extra;
			  dist += 5;
			  dist += ((1U << (extra - 1)) - 1) << 2;
			  dist += val & ((1U << extra) - 1);
			  val >>= extra;
			  bits -= extra;
			}

		      /* Go back dist bytes, and copy len bytes from
			 there.  */

		      if (unlikely ((unsigned int) (pout - porigout) < dist))
			{
			  elf_zlib_failed ();
			  return 0;
			}

		      if (unlikely ((unsigned int) (poutend - pout) < len))
			{
			  elf_zlib_failed ();
			  return 0;
			}

		      if (dist >= len)
			{
			  memcpy (pout, pout - dist, len);
			  pout += len;
			}
		      else
			{
			  while (len > 0)
			    {
			      unsigned int copy;

			      copy = len < dist ? len : dist;
			      memcpy (pout, pout - dist, copy);
			      len -= copy;
			      pout += copy;
			    }
			}
		    }
		}
	    }
	}
    }

  /* We should have filled the output buffer.  */
  if (unlikely (pout != poutend))
    {
      elf_zlib_failed ();
      return 0;
    }

  return 1;
}

/* Verify the zlib checksum.  The checksum is in the 4 bytes at
   CHECKBYTES, and the uncompressed data is at UNCOMPRESSED /
   UNCOMPRESSED_SIZE.  Returns 1 on success, 0 on failure.  */

static int
elf_zlib_verify_checksum (const unsigned char *checkbytes,
			  const unsigned char *uncompressed,
			  size_t uncompressed_size)
{
  unsigned int i;
  unsigned int cksum;
  const unsigned char *p;
  uint32_t s1;
  uint32_t s2;
  size_t hsz;

  cksum = 0;
  for (i = 0; i < 4; i++)
    cksum = (cksum << 8) | checkbytes[i];

  s1 = 1;
  s2 = 0;

  /* Minimize modulo operations.  */

  p = uncompressed;
  hsz = uncompressed_size;
  while (hsz >= 5552)
    {
      for (i = 0; i < 5552; i += 16)
	{
	  /* Manually unroll loop 16 times.  */
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	  s1 = s1 + *p++;
	  s2 = s2 + s1;
	}
      hsz -= 5552;
      s1 %= 65521;
      s2 %= 65521;
    }

  while (hsz >= 16)
    {
      /* Manually unroll loop 16 times.  */
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;
      s1 = s1 + *p++;
      s2 = s2 + s1;

      hsz -= 16;
    }

  for (i = 0; i < hsz; ++i)
    {
      s1 = s1 + *p++;
      s2 = s2 + s1;
    }

  s1 %= 65521;
  s2 %= 65521;

  if (unlikely ((s2 << 16) + s1 != cksum))
    {
      elf_zlib_failed ();
      return 0;
    }

  return 1;
}

/* Inflate a zlib stream from PIN/SIN to POUT/SOUT, and verify the
   checksum.  Return 1 on success, 0 on error.  */

static int
elf_zlib_inflate_and_verify (const unsigned char *pin, size_t sin,
			     uint16_t *zdebug_table, unsigned char *pout,
			     size_t sout)
{
  if (!elf_zlib_inflate (pin, sin, zdebug_table, pout, sout))
    return 0;
  if (!elf_zlib_verify_checksum (pin + sin - 4, pout, sout))
    return 0;
  return 1;
}

/* Uncompress the old compressed debug format, the one emitted by
   --compress-debug-sections=zlib-gnu.  The compressed data is in
   COMPRESSED / COMPRESSED_SIZE, and the function writes to
   *UNCOMPRESSED / *UNCOMPRESSED_SIZE.  ZDEBUG_TABLE is work space to
   hold Huffman tables.  Returns 0 on error, 1 on successful
   decompression or if something goes wrong.  In general we try to
   carry on, by returning 1, even if we can't decompress.  */

static int
elf_uncompress_zdebug (struct backtrace_state *state,
		       const unsigned char *compressed, size_t compressed_size,
		       uint16_t *zdebug_table,
		       backtrace_error_callback error_callback, void *data,
		       unsigned char **uncompressed, size_t *uncompressed_size)
{
  size_t sz;
  size_t i;
  unsigned char *po;

  *uncompressed = NULL;
  *uncompressed_size = 0;

  /* The format starts with the four bytes ZLIB, followed by the 8
     byte length of the uncompressed data in big-endian order,
     followed by a zlib stream.  */

  if (compressed_size < 12 || memcmp (compressed, "ZLIB", 4) != 0)
    return 1;

  sz = 0;
  for (i = 0; i < 8; i++)
    sz = (sz << 8) | compressed[i + 4];

  if (*uncompressed != NULL && *uncompressed_size >= sz)
    po = *uncompressed;
  else
    {
      po = (unsigned char *) backtrace_alloc (state, sz, error_callback, data);
      if (po == NULL)
	return 0;
    }

  if (!elf_zlib_inflate_and_verify (compressed + 12, compressed_size - 12,
				    zdebug_table, po, sz))
    return 1;

  *uncompressed = po;
  *uncompressed_size = sz;

  return 1;
}

/* Uncompress the new compressed debug format, the official standard
   ELF approach emitted by --compress-debug-sections=zlib-gabi.  The
   compressed data is in COMPRESSED / COMPRESSED_SIZE, and the
   function writes to *UNCOMPRESSED / *UNCOMPRESSED_SIZE.
   ZDEBUG_TABLE is work space as for elf_uncompress_zdebug.  Returns 0
   on error, 1 on successful decompression or if something goes wrong.
   In general we try to carry on, by returning 1, even if we can't
   decompress.  */

static int
elf_uncompress_chdr (struct backtrace_state *state,
		     const unsigned char *compressed, size_t compressed_size,
		     uint16_t *zdebug_table,
		     backtrace_error_callback error_callback, void *data,
		     unsigned char **uncompressed, size_t *uncompressed_size)
{
  const b_elf_chdr *chdr;
  unsigned char *po;

  *uncompressed = NULL;
  *uncompressed_size = 0;

  /* The format starts with an ELF compression header.  */
  if (compressed_size < sizeof (b_elf_chdr))
    return 1;

  chdr = (const b_elf_chdr *) compressed;

  if (chdr->ch_type != ELFCOMPRESS_ZLIB)
    {
      /* Unsupported compression algorithm.  */
      return 1;
    }

  if (*uncompressed != NULL && *uncompressed_size >= chdr->ch_size)
    po = *uncompressed;
  else
    {
      po = (unsigned char *) backtrace_alloc (state, chdr->ch_size,
					      error_callback, data);
      if (po == NULL)
	return 0;
    }

  if (!elf_zlib_inflate_and_verify (compressed + sizeof (b_elf_chdr),
				    compressed_size - sizeof (b_elf_chdr),
				    zdebug_table, po, chdr->ch_size))
    return 1;

  *uncompressed = po;
  *uncompressed_size = chdr->ch_size;

  return 1;
}

/* This function is a hook for testing the zlib support.  It is only
   used by tests.  */

int
backtrace_uncompress_zdebug (struct backtrace_state *state,
			     const unsigned char *compressed,
			     size_t compressed_size,
			     backtrace_error_callback error_callback,
			     void *data, unsigned char **uncompressed,
			     size_t *uncompressed_size)
{
  uint16_t *zdebug_table;
  int ret;

  zdebug_table = ((uint16_t *) backtrace_alloc (state, ZDEBUG_TABLE_SIZE,
						error_callback, data));
  if (zdebug_table == NULL)
    return 0;
  ret = elf_uncompress_zdebug (state, compressed, compressed_size,
			       zdebug_table, error_callback, data,
			       uncompressed, uncompressed_size);
  backtrace_free (state, zdebug_table, ZDEBUG_TABLE_SIZE,
		  error_callback, data);
  return ret;
}

/* Add the backtrace data for one ELF file.  Returns 1 on success,
   0 on failure (in both cases descriptor is closed) or -1 if exe
   is non-zero and the ELF file is ET_DYN, which tells the caller that
   elf_add will need to be called on the descriptor again after
   base_address is determined.  */

int
elf_add (struct backtrace_state *state, const char *filename, int descriptor,
	 uintptr_t base_address, backtrace_error_callback error_callback,
	 void *data, fileline *fileline_fn, int *found_sym, int *found_dwarf,
	 int exe, int debuginfo)
{
  struct backtrace_view ehdr_view;
  b_elf_ehdr ehdr;
  off_t shoff;
  unsigned int shnum;
  unsigned int shstrndx;
  struct backtrace_view shdrs_view;
  int shdrs_view_valid;
  const b_elf_shdr *shdrs;
  const b_elf_shdr *shstrhdr;
  size_t shstr_size;
  off_t shstr_off;
  struct backtrace_view names_view;
  int names_view_valid;
  const char *names;
  unsigned int symtab_shndx;
  unsigned int dynsym_shndx;
  unsigned int i;
  struct debug_section_info sections[DEBUG_MAX];
  struct backtrace_view symtab_view;
  int symtab_view_valid;
  struct backtrace_view strtab_view;
  int strtab_view_valid;
  struct backtrace_view buildid_view;
  int buildid_view_valid;
  const char *buildid_data;
  uint32_t buildid_size;
  struct backtrace_view debuglink_view;
  int debuglink_view_valid;
  const char *debuglink_name;
  uint32_t debuglink_crc;
  off_t min_offset;
  off_t max_offset;
  struct backtrace_view debug_view;
  int debug_view_valid;
  unsigned int using_debug_view;
  uint16_t *zdebug_table;

  *found_sym = 0;
  *found_dwarf = 0;

  shdrs_view_valid = 0;
  names_view_valid = 0;
  symtab_view_valid = 0;
  strtab_view_valid = 0;
  buildid_view_valid = 0;
  buildid_data = NULL;
  buildid_size = 0;
  debuglink_view_valid = 0;
  debuglink_name = NULL;
  debuglink_crc = 0;
  debug_view_valid = 0;

  if (!backtrace_get_view (state, descriptor, 0, sizeof ehdr, error_callback,
			   data, &ehdr_view))
    goto fail;

  memcpy (&ehdr, ehdr_view.data, sizeof ehdr);

  backtrace_release_view (state, &ehdr_view, error_callback, data);

  if (ehdr.e_ident[EI_MAG0] != ELFMAG0
      || ehdr.e_ident[EI_MAG1] != ELFMAG1
      || ehdr.e_ident[EI_MAG2] != ELFMAG2
      || ehdr.e_ident[EI_MAG3] != ELFMAG3)
    {
      error_callback (data, "executable file is not ELF", 0);
      goto fail;
    }
  if (ehdr.e_ident[EI_VERSION] != EV_CURRENT)
    {
      error_callback (data, "executable file is unrecognized ELF version", 0);
      goto fail;
    }

#if BACKTRACE_ELF_SIZE == 32
#define BACKTRACE_ELFCLASS ELFCLASS32
#else
#define BACKTRACE_ELFCLASS ELFCLASS64
#endif

  if (ehdr.e_ident[EI_CLASS] != BACKTRACE_ELFCLASS)
    {
      error_callback (data, "executable file is unexpected ELF class", 0);
      goto fail;
    }

  if (ehdr.e_ident[EI_DATA] != ELFDATA2LSB
      && ehdr.e_ident[EI_DATA] != ELFDATA2MSB)
    {
      error_callback (data, "executable file has unknown endianness", 0);
      goto fail;
    }

  /* If the executable is ET_DYN, it is either a PIE, or we are running
     directly a shared library with .interp.  We need to wait for
     dl_iterate_phdr in that case to determine the actual base_address.  */
  if (exe && ehdr.e_type == ET_DYN)
    return -1;

  shoff = ehdr.e_shoff;
  shnum = ehdr.e_shnum;
  shstrndx = ehdr.e_shstrndx;

  if ((shnum == 0 || shstrndx == SHN_XINDEX)
      && shoff != 0)
    {
      struct backtrace_view shdr_view;
      const b_elf_shdr *shdr;

      if (!backtrace_get_view (state, descriptor, shoff, sizeof shdr,
			       error_callback, data, &shdr_view))
	goto fail;

      shdr = (const b_elf_shdr *) shdr_view.data;

      if (shnum == 0)
	shnum = shdr->sh_size;

      if (shstrndx == SHN_XINDEX)
	{
	  shstrndx = shdr->sh_link;

	  /* Versions of the GNU binutils between 2.12 and 2.18 did
	     not handle objects with more than SHN_LORESERVE sections
	     correctly.  All large section indexes were offset by
	     0x100.  There is more information at
	     http://sourceware.org/bugzilla/show_bug.cgi?id-5900 .
	     Fortunately these object files are easy to detect, as the
	     GNU binutils always put the section header string table
	     near the end of the list of sections.  Thus if the
	     section header string table index is larger than the
	     number of sections, then we know we have to subtract
	     0x100 to get the real section index.  */
	  if (shstrndx >= shnum && shstrndx >= SHN_LORESERVE + 0x100)
	    shstrndx -= 0x100;
	}

      backtrace_release_view (state, &shdr_view, error_callback, data);
    }

  /* To translate PC to file/line when using DWARF, we need to find
     the .debug_info and .debug_line sections.  */

  /* Read the section headers, skipping the first one.  */

  if (!backtrace_get_view (state, descriptor, shoff + sizeof (b_elf_shdr),
			   (shnum - 1) * sizeof (b_elf_shdr),
			   error_callback, data, &shdrs_view))
    goto fail;
  shdrs_view_valid = 1;
  shdrs = (const b_elf_shdr *) shdrs_view.data;

  /* Read the section names.  */

  shstrhdr = &shdrs[shstrndx - 1];
  shstr_size = shstrhdr->sh_size;
  shstr_off = shstrhdr->sh_offset;

  if (!backtrace_get_view (state, descriptor, shstr_off, shstr_size,
			   error_callback, data, &names_view))
    goto fail;
  names_view_valid = 1;
  names = (const char *) names_view.data;

  symtab_shndx = 0;
  dynsym_shndx = 0;

  memset (sections, 0, sizeof sections);

  /* Look for the symbol table.  */
  for (i = 1; i < shnum; ++i)
    {
      const b_elf_shdr *shdr;
      unsigned int sh_name;
      const char *name;
      int j;

      shdr = &shdrs[i - 1];

      if (shdr->sh_type == SHT_SYMTAB)
	symtab_shndx = i;
      else if (shdr->sh_type == SHT_DYNSYM)
	dynsym_shndx = i;

      sh_name = shdr->sh_name;
      if (sh_name >= shstr_size)
	{
	  error_callback (data, "ELF section name out of range", 0);
	  goto fail;
	}

      name = names + sh_name;

      for (j = 0; j < (int) DEBUG_MAX; ++j)
	{
	  if (strcmp (name, debug_section_names[j]) == 0)
	    {
	      sections[j].offset = shdr->sh_offset;
	      sections[j].size = shdr->sh_size;
	      sections[j].compressed = (shdr->sh_flags & SHF_COMPRESSED) != 0;
	      break;
	    }
	}

      /* Read the build ID if present.  This could check for any
	 SHT_NOTE section with the right note name and type, but gdb
	 looks for a specific section name.  */
      if (!debuginfo
	  && !buildid_view_valid
	  && strcmp (name, ".note.gnu.build-id") == 0)
	{
	  const b_elf_note *note;

	  if (!backtrace_get_view (state, descriptor, shdr->sh_offset,
				   shdr->sh_size, error_callback, data,
				   &buildid_view))
	    goto fail;

	  buildid_view_valid = 1;
	  note = (const b_elf_note *) buildid_view.data;
	  if (note->type == NT_GNU_BUILD_ID
	      && note->namesz == 4
	      && strncmp (note->name, "GNU", 4) == 0
	      && shdr->sh_size < 12 + ((note->namesz + 3) & ~ 3) + note->descsz)
	    {
	      buildid_data = &note->name[0] + ((note->namesz + 3) & ~ 3);
	      buildid_size = note->descsz;
	    }
	}

      /* Read the debuglink file if present.  */
      if (!debuginfo
	  && !debuglink_view_valid
	  && strcmp (name, ".gnu_debuglink") == 0)
	{
	  const char *debuglink_data;
	  size_t crc_offset;

	  if (!backtrace_get_view (state, descriptor, shdr->sh_offset,
				   shdr->sh_size, error_callback, data,
				   &debuglink_view))
	    goto fail;

	  debuglink_view_valid = 1;
	  debuglink_data = (const char *) debuglink_view.data;
	  crc_offset = strnlen (debuglink_data, shdr->sh_size);
	  crc_offset = (crc_offset + 3) & ~3;
	  if (crc_offset + 4 <= shdr->sh_size)
	    {
	      debuglink_name = debuglink_data;
	      debuglink_crc = *(const uint32_t*)(debuglink_data + crc_offset);
	    }
	}
    }

  if (symtab_shndx == 0)
    symtab_shndx = dynsym_shndx;
  if (symtab_shndx != 0 /* HEAPTRACK: also read symbols from debuginfo file && !debuginfo */)
    {
      const b_elf_shdr *symtab_shdr;
      unsigned int strtab_shndx;
      const b_elf_shdr *strtab_shdr;
      struct elf_syminfo_data *sdata;

      symtab_shdr = &shdrs[symtab_shndx - 1];
      strtab_shndx = symtab_shdr->sh_link;
      if (strtab_shndx >= shnum)
	{
	  error_callback (data,
			  "ELF symbol table strtab link out of range", 0);
	  goto fail;
	}
      strtab_shdr = &shdrs[strtab_shndx - 1];

      if (!backtrace_get_view (state, descriptor, symtab_shdr->sh_offset,
			       symtab_shdr->sh_size, error_callback, data,
			       &symtab_view))
	goto fail;
      symtab_view_valid = 1;

      if (!backtrace_get_view (state, descriptor, strtab_shdr->sh_offset,
			       strtab_shdr->sh_size, error_callback, data,
			       &strtab_view))
	goto fail;
      strtab_view_valid = 1;

      sdata = ((struct elf_syminfo_data *)
	       backtrace_alloc (state, sizeof *sdata, error_callback, data));
      if (sdata == NULL)
	goto fail;

      if (!elf_initialize_syminfo (state, base_address,
				   symtab_view.data, symtab_shdr->sh_size,
				   strtab_view.data, strtab_shdr->sh_size,
				   error_callback, data, sdata))
	{
	  backtrace_free (state, sdata, sizeof *sdata, error_callback, data);
	  goto fail;
	}

      /* We no longer need the symbol table, but we hold on to the
	 string table permanently.  */
      backtrace_release_view (state, &symtab_view, error_callback, data);
      symtab_view_valid = 0;

      *found_sym = 1;

      elf_add_syminfo_data (state, sdata);
    }

  backtrace_release_view (state, &shdrs_view, error_callback, data);
  shdrs_view_valid = 0;
  backtrace_release_view (state, &names_view, error_callback, data);
  names_view_valid = 0;

  /* If the debug info is in a separate file, read that one instead.  */

  if (buildid_data != NULL)
    {
      int d;

      d = elf_open_debugfile_by_buildid (state, buildid_data, buildid_size,
					 error_callback, data);
      if (d >= 0)
	{
	  backtrace_release_view (state, &buildid_view, error_callback, data);
	  if (debuglink_view_valid)
	    backtrace_release_view (state, &debuglink_view, error_callback,
				    data);
	  return elf_add (state, NULL, d, base_address, error_callback, data,
			  fileline_fn, found_sym, found_dwarf, 0, 1);
	}
    }

  if (buildid_view_valid)
    {
      backtrace_release_view (state, &buildid_view, error_callback, data);
      buildid_view_valid = 0;
    }

  if (debuglink_name != NULL)
    {
      int d;

      d = elf_open_debugfile_by_debuglink (state, filename, debuglink_name,
					   debuglink_crc, error_callback,
					   data);
      if (d >= 0)
	{
	  backtrace_release_view (state, &debuglink_view, error_callback,
				  data);
	  return elf_add (state, NULL, d, base_address, error_callback, data,
			  fileline_fn, found_sym, found_dwarf, 0, 1);
	}
    }

  if (debuglink_view_valid)
    {
      backtrace_release_view (state, &debuglink_view, error_callback, data);
      debuglink_view_valid = 0;
    }

  /* Read all the debug sections in a single view, since they are
     probably adjacent in the file.  We never release this view.  */

  min_offset = 0;
  max_offset = 0;
  for (i = 0; i < (int) DEBUG_MAX; ++i)
    {
      off_t end;

      if (sections[i].size == 0)
	continue;
      if (min_offset == 0 || sections[i].offset < min_offset)
	min_offset = sections[i].offset;
      end = sections[i].offset + sections[i].size;
      if (end > max_offset)
	max_offset = end;
    }
  if (min_offset == 0 || max_offset == 0)
    {
      if (!backtrace_close (descriptor, error_callback, data))
	goto fail;
      return 1;
    }

  if (!backtrace_get_view (state, descriptor, min_offset,
			   max_offset - min_offset,
			   error_callback, data, &debug_view))
    goto fail;
  debug_view_valid = 1;

  /* We've read all we need from the executable.  */
  if (!backtrace_close (descriptor, error_callback, data))
    goto fail;
  descriptor = -1;

  using_debug_view = 0;
  for (i = 0; i < (int) DEBUG_MAX; ++i)
    {
      if (sections[i].size == 0)
	sections[i].data = NULL;
      else
	{
	  sections[i].data = ((const unsigned char *) debug_view.data
			      + (sections[i].offset - min_offset));
	  if (i < ZDEBUG_INFO)
	    ++using_debug_view;
	}
    }

  /* Uncompress the old format (--compress-debug-sections=zlib-gnu).  */

  zdebug_table = NULL;
  for (i = 0; i < ZDEBUG_INFO; ++i)
    {
      struct debug_section_info *pz;

      pz = &sections[i + ZDEBUG_INFO - DEBUG_INFO];
      if (sections[i].size == 0 && pz->size > 0)
	{
	  unsigned char *uncompressed_data;
	  size_t uncompressed_size;

	  if (zdebug_table == NULL)
	    {
	      zdebug_table = ((uint16_t *)
			      backtrace_alloc (state, ZDEBUG_TABLE_SIZE,
					       error_callback, data));
	      if (zdebug_table == NULL)
		goto fail;
	    }

	  uncompressed_data = NULL;
	  uncompressed_size = 0;
	  if (!elf_uncompress_zdebug (state, pz->data, pz->size, zdebug_table,
				      error_callback, data,
				      &uncompressed_data, &uncompressed_size))
	    goto fail;
	  sections[i].data = uncompressed_data;
	  sections[i].size = uncompressed_size;
	  sections[i].compressed = 0;
	}
    }

  /* Uncompress the official ELF format
     (--compress-debug-sections=zlib-gabi).  */
  for (i = 0; i < ZDEBUG_INFO; ++i)
    {
      unsigned char *uncompressed_data;
      size_t uncompressed_size;

      if (sections[i].size == 0 || !sections[i].compressed)
	continue;

      if (zdebug_table == NULL)
	{
	  zdebug_table = ((uint16_t *)
			  backtrace_alloc (state, ZDEBUG_TABLE_SIZE,
					   error_callback, data));
	  if (zdebug_table == NULL)
	    goto fail;
	}

      uncompressed_data = NULL;
      uncompressed_size = 0;
      if (!elf_uncompress_chdr (state, sections[i].data, sections[i].size,
				zdebug_table, error_callback, data,
				&uncompressed_data, &uncompressed_size))
	goto fail;
      sections[i].data = uncompressed_data;
      sections[i].size = uncompressed_size;
      sections[i].compressed = 0;

      --using_debug_view;
    }

  if (zdebug_table != NULL)
    backtrace_free (state, zdebug_table, ZDEBUG_TABLE_SIZE,
		    error_callback, data);

  if (debug_view_valid && using_debug_view == 0)
    {
      backtrace_release_view (state, &debug_view, error_callback, data);
      debug_view_valid = 0;
    }

  if (!backtrace_dwarf_add (state, base_address,
			    sections[DEBUG_INFO].data,
			    sections[DEBUG_INFO].size,
			    sections[DEBUG_LINE].data,
			    sections[DEBUG_LINE].size,
			    sections[DEBUG_ABBREV].data,
			    sections[DEBUG_ABBREV].size,
			    sections[DEBUG_RANGES].data,
			    sections[DEBUG_RANGES].size,
			    sections[DEBUG_STR].data,
			    sections[DEBUG_STR].size,
			    ehdr.e_ident[EI_DATA] == ELFDATA2MSB,
			    error_callback, data, fileline_fn))
    goto fail;

  *found_dwarf = 1;

  return 1;

 fail:
  if (shdrs_view_valid)
    backtrace_release_view (state, &shdrs_view, error_callback, data);
  if (names_view_valid)
    backtrace_release_view (state, &names_view, error_callback, data);
  if (symtab_view_valid)
    backtrace_release_view (state, &symtab_view, error_callback, data);
  if (strtab_view_valid)
    backtrace_release_view (state, &strtab_view, error_callback, data);
  if (debuglink_view_valid)
    backtrace_release_view (state, &debuglink_view, error_callback, data);
  if (buildid_view_valid)
    backtrace_release_view (state, &buildid_view, error_callback, data);
  if (debug_view_valid)
    backtrace_release_view (state, &debug_view, error_callback, data);
  if (descriptor != -1)
    backtrace_close (descriptor, error_callback, data);
  return 0;
}

/* Data passed to phdr_callback.  */

struct phdr_data
{
  struct backtrace_state *state;
  backtrace_error_callback error_callback;
  void *data;
  fileline *fileline_fn;
  int *found_sym;
  int *found_dwarf;
  const char *exe_filename;
  int exe_descriptor;
};

/* Callback passed to dl_iterate_phdr.  Load debug info from shared
   libraries.  */

static int
#ifdef __i386__
__attribute__ ((__force_align_arg_pointer__))
#endif
phdr_callback (struct dl_phdr_info *info, size_t size ATTRIBUTE_UNUSED,
	       void *pdata)
{
  struct phdr_data *pd = (struct phdr_data *) pdata;
  const char *filename;
  int descriptor;
  int does_not_exist;
  fileline elf_fileline_fn;
  int found_dwarf;

  /* There is not much we can do if we don't have the module name,
     unless executable is ET_DYN, where we expect the very first
     phdr_callback to be for the PIE.  */
  if (info->dlpi_name == NULL || info->dlpi_name[0] == '\0')
    {
      if (pd->exe_descriptor == -1)
	return 0;
      filename = pd->exe_filename;
      descriptor = pd->exe_descriptor;
      pd->exe_descriptor = -1;
    }
  else
    {
      if (pd->exe_descriptor != -1)
	{
	  backtrace_close (pd->exe_descriptor, pd->error_callback, pd->data);
	  pd->exe_descriptor = -1;
	}

      filename = info->dlpi_name;
      descriptor = backtrace_open (info->dlpi_name, pd->error_callback,
				   pd->data, &does_not_exist);
      if (descriptor < 0)
	return 0;
    }

  if (elf_add (pd->state, filename, descriptor, info->dlpi_addr,
	       pd->error_callback, pd->data, &elf_fileline_fn, pd->found_sym,
	       &found_dwarf, 0, 0))
    {
      if (found_dwarf)
	{
	  *pd->found_dwarf = 1;
	  *pd->fileline_fn = elf_fileline_fn;
	}
    }

  return 0;
}

/* Initialize the backtrace data we need from an ELF executable.  At
   the ELF level, all we need to do is find the debug info
   sections.  */

int
backtrace_initialize (struct backtrace_state *state, const char *filename,
		      int descriptor, backtrace_error_callback error_callback,
		      void *data, fileline *fileline_fn)
{
  int ret;
  int found_sym;
  int found_dwarf;
  fileline elf_fileline_fn = elf_nodebug;
  struct phdr_data pd;

  ret = elf_add (state, filename, descriptor, 0, error_callback, data,
		 &elf_fileline_fn, &found_sym, &found_dwarf, 1, 0);
  if (!ret)
    return 0;

  pd.state = state;
  pd.error_callback = error_callback;
  pd.data = data;
  pd.fileline_fn = &elf_fileline_fn;
  pd.found_sym = &found_sym;
  pd.found_dwarf = &found_dwarf;
  pd.exe_filename = filename;
  pd.exe_descriptor = ret < 0 ? descriptor : -1;

  dl_iterate_phdr (phdr_callback, (void *) &pd);

  if (!state->threaded)
    {
      if (found_sym)
	state->syminfo_fn = elf_syminfo;
      else if (state->syminfo_fn == NULL)
	state->syminfo_fn = elf_nosyms;
    }
  else
    {
      if (found_sym)
	backtrace_atomic_store_pointer (&state->syminfo_fn, elf_syminfo);
      else
	(void) __sync_bool_compare_and_swap (&state->syminfo_fn, NULL,
					     elf_nosyms);
    }

  if (!state->threaded)
    *fileline_fn = state->fileline_fn;
  else
    *fileline_fn = backtrace_atomic_load_pointer (&state->fileline_fn);

  if (*fileline_fn == NULL || *fileline_fn == elf_nodebug)
    *fileline_fn = elf_fileline_fn;

  return 1;
}