aboutsummaryrefslogtreecommitdiffstats
path: root/tools/objtool/check.c
blob: bae6b261481db0ba9322321b1a06c034a676187c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
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
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
 */

#include <string.h>
#include <stdlib.h>

#include "builtin.h"
#include "check.h"
#include "elf.h"
#include "special.h"
#include "arch.h"
#include "warn.h"

#include <linux/hashtable.h>
#include <linux/kernel.h>

#define FAKE_JUMP_OFFSET -1

#define C_JUMP_TABLE_SECTION ".rodata..c_jump_table"

struct alternative {
	struct list_head list;
	struct instruction *insn;
	bool skip_orig;
};

const char *objname;
struct cfi_state initial_func_cfi;

struct instruction *find_insn(struct objtool_file *file,
			      struct section *sec, unsigned long offset)
{
	struct instruction *insn;

	hash_for_each_possible(file->insn_hash, insn, hash, offset)
		if (insn->sec == sec && insn->offset == offset)
			return insn;

	return NULL;
}

static struct instruction *next_insn_same_sec(struct objtool_file *file,
					      struct instruction *insn)
{
	struct instruction *next = list_next_entry(insn, list);

	if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
		return NULL;

	return next;
}

static struct instruction *next_insn_same_func(struct objtool_file *file,
					       struct instruction *insn)
{
	struct instruction *next = list_next_entry(insn, list);
	struct symbol *func = insn->func;

	if (!func)
		return NULL;

	if (&next->list != &file->insn_list && next->func == func)
		return next;

	/* Check if we're already in the subfunction: */
	if (func == func->cfunc)
		return NULL;

	/* Move to the subfunction: */
	return find_insn(file, func->cfunc->sec, func->cfunc->offset);
}

#define func_for_each_insn_all(file, func, insn)			\
	for (insn = find_insn(file, func->sec, func->offset);		\
	     insn;							\
	     insn = next_insn_same_func(file, insn))

#define func_for_each_insn(file, func, insn)				\
	for (insn = find_insn(file, func->sec, func->offset);		\
	     insn && &insn->list != &file->insn_list &&			\
		insn->sec == func->sec &&				\
		insn->offset < func->offset + func->len;		\
	     insn = list_next_entry(insn, list))

#define func_for_each_insn_continue_reverse(file, func, insn)		\
	for (insn = list_prev_entry(insn, list);			\
	     &insn->list != &file->insn_list &&				\
		insn->sec == func->sec && insn->offset >= func->offset;	\
	     insn = list_prev_entry(insn, list))

#define sec_for_each_insn_from(file, insn)				\
	for (; insn; insn = next_insn_same_sec(file, insn))

#define sec_for_each_insn_continue(file, insn)				\
	for (insn = next_insn_same_sec(file, insn); insn;		\
	     insn = next_insn_same_sec(file, insn))

static bool is_sibling_call(struct instruction *insn)
{
	/* An indirect jump is either a sibling call or a jump to a table. */
	if (insn->type == INSN_JUMP_DYNAMIC)
		return list_empty(&insn->alts);

	if (insn->type != INSN_JUMP_CONDITIONAL &&
	    insn->type != INSN_JUMP_UNCONDITIONAL)
		return false;

	/* add_jump_destinations() sets insn->call_dest for sibling calls. */
	return !!insn->call_dest;
}

/*
 * This checks to see if the given function is a "noreturn" function.
 *
 * For global functions which are outside the scope of this object file, we
 * have to keep a manual list of them.
 *
 * For local functions, we have to detect them manually by simply looking for
 * the lack of a return instruction.
 */
static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
				int recursion)
{
	int i;
	struct instruction *insn;
	bool empty = true;

	/*
	 * Unfortunately these have to be hard coded because the noreturn
	 * attribute isn't provided in ELF data.
	 */
	static const char * const global_noreturns[] = {
		"__stack_chk_fail",
		"panic",
		"do_exit",
		"do_task_dead",
		"__module_put_and_exit",
		"complete_and_exit",
		"__reiserfs_panic",
		"lbug_with_loc",
		"fortify_panic",
		"usercopy_abort",
		"machine_real_restart",
		"rewind_stack_do_exit",
		"cpu_bringup_and_idle",
	};

	if (!func)
		return false;

	if (func->bind == STB_WEAK)
		return false;

	if (func->bind == STB_GLOBAL)
		for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
			if (!strcmp(func->name, global_noreturns[i]))
				return true;

	if (!func->len)
		return false;

	insn = find_insn(file, func->sec, func->offset);
	if (!insn->func)
		return false;

	func_for_each_insn_all(file, func, insn) {
		empty = false;

		if (insn->type == INSN_RETURN)
			return false;
	}

	if (empty)
		return false;

	/*
	 * A function can have a sibling call instead of a return.  In that
	 * case, the function's dead-end status depends on whether the target
	 * of the sibling call returns.
	 */
	func_for_each_insn_all(file, func, insn) {
		if (is_sibling_call(insn)) {
			struct instruction *dest = insn->jump_dest;

			if (!dest)
				/* sibling call to another file */
				return false;

			/* local sibling call */
			if (recursion == 5) {
				/*
				 * Infinite recursion: two functions have
				 * sibling calls to each other.  This is a very
				 * rare case.  It means they aren't dead ends.
				 */
				return false;
			}

			return __dead_end_function(file, dest->func, recursion+1);
		}
	}

	return true;
}

static bool dead_end_function(struct objtool_file *file, struct symbol *func)
{
	return __dead_end_function(file, func, 0);
}

static void clear_insn_state(struct insn_state *state)
{
	int i;

	memset(state, 0, sizeof(*state));
	state->cfa.base = CFI_UNDEFINED;
	for (i = 0; i < CFI_NUM_REGS; i++) {
		state->regs[i].base = CFI_UNDEFINED;
		state->vals[i].base = CFI_UNDEFINED;
	}
	state->drap_reg = CFI_UNDEFINED;
	state->drap_offset = -1;
}

/*
 * Call the arch-specific instruction decoder for all the instructions and add
 * them to the global instruction list.
 */
static int decode_instructions(struct objtool_file *file)
{
	struct section *sec;
	struct symbol *func;
	unsigned long offset;
	struct instruction *insn;
	int ret;

	for_each_sec(file, sec) {

		if (!(sec->sh.sh_flags & SHF_EXECINSTR))
			continue;

		if (strcmp(sec->name, ".altinstr_replacement") &&
		    strcmp(sec->name, ".altinstr_aux") &&
		    strncmp(sec->name, ".discard.", 9))
			sec->text = true;

		for (offset = 0; offset < sec->len; offset += insn->len) {
			insn = malloc(sizeof(*insn));
			if (!insn) {
				WARN("malloc failed");
				return -1;
			}
			memset(insn, 0, sizeof(*insn));
			INIT_LIST_HEAD(&insn->alts);
			clear_insn_state(&insn->state);

			insn->sec = sec;
			insn->offset = offset;

			ret = arch_decode_instruction(file->elf, sec, offset,
						      sec->len - offset,
						      &insn->len, &insn->type,
						      &insn->immediate,
						      &insn->stack_op);
			if (ret)
				goto err;

			hash_add(file->insn_hash, &insn->hash, insn->offset);
			list_add_tail(&insn->list, &file->insn_list);
		}

		list_for_each_entry(func, &sec->symbol_list, list) {
			if (func->type != STT_FUNC || func->alias != func)
				continue;

			if (!find_insn(file, sec, func->offset)) {
				WARN("%s(): can't find starting instruction",
				     func->name);
				return -1;
			}

			func_for_each_insn(file, func, insn)
				insn->func = func;
		}
	}

	return 0;

err:
	free(insn);
	return ret;
}

/*
 * Mark "ud2" instructions and manually annotated dead ends.
 */
static int add_dead_ends(struct objtool_file *file)
{
	struct section *sec;
	struct rela *rela;
	struct instruction *insn;
	bool found;

	/*
	 * By default, "ud2" is a dead end unless otherwise annotated, because
	 * GCC 7 inserts it for certain divide-by-zero cases.
	 */
	for_each_insn(file, insn)
		if (insn->type == INSN_BUG)
			insn->dead_end = true;

	/*
	 * Check for manually annotated dead ends.
	 */
	sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
	if (!sec)
		goto reachable;

	list_for_each_entry(rela, &sec->rela_list, list) {
		if (rela->sym->type != STT_SECTION) {
			WARN("unexpected relocation symbol type in %s", sec->name);
			return -1;
		}
		insn = find_insn(file, rela->sym->sec, rela->addend);
		if (insn)
			insn = list_prev_entry(insn, list);
		else if (rela->addend == rela->sym->sec->len) {
			found = false;
			list_for_each_entry_reverse(insn, &file->insn_list, list) {
				if (insn->sec == rela->sym->sec) {
					found = true;
					break;
				}
			}

			if (!found) {
				WARN("can't find unreachable insn at %s+0x%x",
				     rela->sym->sec->name, rela->addend);
				return -1;
			}
		} else {
			WARN("can't find unreachable insn at %s+0x%x",
			     rela->sym->sec->name, rela->addend);
			return -1;
		}

		insn->dead_end = true;
	}

reachable:
	/*
	 * These manually annotated reachable checks are needed for GCC 4.4,
	 * where the Linux unreachable() macro isn't supported.  In that case
	 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
	 * not a dead end.
	 */
	sec = find_section_by_name(file->elf, ".rela.discard.reachable");
	if (!sec)
		return 0;

	list_for_each_entry(rela, &sec->rela_list, list) {
		if (rela->sym->type != STT_SECTION) {
			WARN("unexpected relocation symbol type in %s", sec->name);
			return -1;
		}
		insn = find_insn(file, rela->sym->sec, rela->addend);
		if (insn)
			insn = list_prev_entry(insn, list);
		else if (rela->addend == rela->sym->sec->len) {
			found = false;
			list_for_each_entry_reverse(insn, &file->insn_list, list) {
				if (insn->sec == rela->sym->sec) {
					found = true;
					break;
				}
			}

			if (!found) {
				WARN("can't find reachable insn at %s+0x%x",
				     rela->sym->sec->name, rela->addend);
				return -1;
			}
		} else {
			WARN("can't find reachable insn at %s+0x%x",
			     rela->sym->sec->name, rela->addend);
			return -1;
		}

		insn->dead_end = false;
	}

	return 0;
}

/*
 * Warnings shouldn't be reported for ignored functions.
 */
static void add_ignores(struct objtool_file *file)
{
	struct instruction *insn;
	struct section *sec;
	struct symbol *func;
	struct rela *rela;

	sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
	if (!sec)
		return;

	list_for_each_entry(rela, &sec->rela_list, list) {
		switch (rela->sym->type) {
		case STT_FUNC:
			func = rela->sym;
			break;

		case STT_SECTION:
			func = find_symbol_by_offset(rela->sym->sec, rela->addend);
			if (!func || func->type != STT_FUNC)
				continue;
			break;

		default:
			WARN("unexpected relocation symbol type in %s: %d", sec->name, rela->sym->type);
			continue;
		}

		func_for_each_insn_all(file, func, insn)
			insn->ignore = true;
	}
}

/*
 * This is a whitelist of functions that is allowed to be called with AC set.
 * The list is meant to be minimal and only contains compiler instrumentation
 * ABI and a few functions used to implement *_{to,from}_user() functions.
 *
 * These functions must not directly change AC, but may PUSHF/POPF.
 */
static const char *uaccess_safe_builtin[] = {
	/* KASAN */
	"kasan_report",
	"check_memory_region",
	/* KASAN out-of-line */
	"__asan_loadN_noabort",
	"__asan_load1_noabort",
	"__asan_load2_noabort",
	"__asan_load4_noabort",
	"__asan_load8_noabort",
	"__asan_load16_noabort",
	"__asan_storeN_noabort",
	"__asan_store1_noabort",
	"__asan_store2_noabort",
	"__asan_store4_noabort",
	"__asan_store8_noabort",
	"__asan_store16_noabort",
	/* KASAN in-line */
	"__asan_report_load_n_noabort",
	"__asan_report_load1_noabort",
	"__asan_report_load2_noabort",
	"__asan_report_load4_noabort",
	"__asan_report_load8_noabort",
	"__asan_report_load16_noabort",
	"__asan_report_store_n_noabort",
	"__asan_report_store1_noabort",
	"__asan_report_store2_noabort",
	"__asan_report_store4_noabort",
	"__asan_report_store8_noabort",
	"__asan_report_store16_noabort",
	/* KCOV */
	"write_comp_data",
	"__sanitizer_cov_trace_pc",
	"__sanitizer_cov_trace_const_cmp1",
	"__sanitizer_cov_trace_const_cmp2",
	"__sanitizer_cov_trace_const_cmp4",
	"__sanitizer_cov_trace_const_cmp8",
	"__sanitizer_cov_trace_cmp1",
	"__sanitizer_cov_trace_cmp2",
	"__sanitizer_cov_trace_cmp4",
	"__sanitizer_cov_trace_cmp8",
	/* UBSAN */
	"ubsan_type_mismatch_common",
	"__ubsan_handle_type_mismatch",
	"__ubsan_handle_type_mismatch_v1",
	"__ubsan_handle_shift_out_of_bounds",
	/* misc */
	"csum_partial_copy_generic",
	"__memcpy_mcsafe",
	"mcsafe_handle_tail",
	"ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
	NULL
};

static void add_uaccess_safe(struct objtool_file *file)
{
	struct symbol *func;
	const char **name;

	if (!uaccess)
		return;

	for (name = uaccess_safe_builtin; *name; name++) {
		func = find_symbol_by_name(file->elf, *name);
		if (!func)
			continue;

		func->uaccess_safe = true;
	}
}

/*
 * FIXME: For now, just ignore any alternatives which add retpolines.  This is
 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
 * But it at least allows objtool to understand the control flow *around* the
 * retpoline.
 */
static int add_ignore_alternatives(struct objtool_file *file)
{
	struct section *sec;
	struct rela *rela;
	struct instruction *insn;

	sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
	if (!sec)
		return 0;

	list_for_each_entry(rela, &sec->rela_list, list) {
		if (rela->sym->type != STT_SECTION) {
			WARN("unexpected relocation symbol type in %s", sec->name);
			return -1;
		}

		insn = find_insn(file, rela->sym->sec, rela->addend);
		if (!insn) {
			WARN("bad .discard.ignore_alts entry");
			return -1;
		}

		insn->ignore_alts = true;
	}

	return 0;
}

/*
 * Find the destination instructions for all jumps.
 */
static int add_jump_destinations(struct objtool_file *file)
{
	struct instruction *insn;
	struct rela *rela;
	struct section *dest_sec;
	unsigned long dest_off;

	for_each_insn(file, insn) {
		if (insn->type != INSN_JUMP_CONDITIONAL &&
		    insn->type != INSN_JUMP_UNCONDITIONAL)
			continue;

		if (insn->offset == FAKE_JUMP_OFFSET)
			continue;

		rela = find_rela_by_dest_range(insn->sec, insn->offset,
					       insn->len);
		if (!rela) {
			dest_sec = insn->sec;
			dest_off = insn->offset + insn->len + insn->immediate;
		} else if (rela->sym->type == STT_SECTION) {
			dest_sec = rela->sym->sec;
			dest_off = rela->addend + 4;
		} else if (rela->sym->sec->idx) {
			dest_sec = rela->sym->sec;
			dest_off = rela->sym->sym.st_value + rela->addend + 4;
		} else if (strstr(rela->sym->name, "_indirect_thunk_")) {
			/*
			 * Retpoline jumps are really dynamic jumps in
			 * disguise, so convert them accordingly.
			 */
			if (insn->type == INSN_JUMP_UNCONDITIONAL)
				insn->type = INSN_JUMP_DYNAMIC;
			else
				insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;

			insn->retpoline_safe = true;
			continue;
		} else {
			/* external sibling call */
			insn->call_dest = rela->sym;
			continue;
		}

		insn->jump_dest = find_insn(file, dest_sec, dest_off);
		if (!insn->jump_dest) {

			/*
			 * This is a special case where an alt instruction
			 * jumps past the end of the section.  These are
			 * handled later in handle_group_alt().
			 */
			if (!strcmp(insn->sec->name, ".altinstr_replacement"))
				continue;

			WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
				  insn->sec, insn->offset, dest_sec->name,
				  dest_off);
			return -1;
		}

		/*
		 * Cross-function jump.
		 */
		if (insn->func && insn->jump_dest->func &&
		    insn->func != insn->jump_dest->func) {

			/*
			 * For GCC 8+, create parent/child links for any cold
			 * subfunctions.  This is _mostly_ redundant with a
			 * similar initialization in read_symbols().
			 *
			 * If a function has aliases, we want the *first* such
			 * function in the symbol table to be the subfunction's
			 * parent.  In that case we overwrite the
			 * initialization done in read_symbols().
			 *
			 * However this code can't completely replace the
			 * read_symbols() code because this doesn't detect the
			 * case where the parent function's only reference to a
			 * subfunction is through a jump table.
			 */
			if (!strstr(insn->func->name, ".cold") &&
			    strstr(insn->jump_dest->func->name, ".cold")) {
				insn->func->cfunc = insn->jump_dest->func;
				insn->jump_dest->func->pfunc = insn->func;

			} else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
				   insn->jump_dest->offset == insn->jump_dest->func->offset) {

				/* internal sibling call */
				insn->call_dest = insn->jump_dest->func;
			}
		}
	}

	return 0;
}

/*
 * Find the destination instructions for all calls.
 */
static int add_call_destinations(struct objtool_file *file)
{
	struct instruction *insn;
	unsigned long dest_off;
	struct rela *rela;

	for_each_insn(file, insn) {
		if (insn->type != INSN_CALL)
			continue;

		rela = find_rela_by_dest_range(insn->sec, insn->offset,
					       insn->len);
		if (!rela) {
			dest_off = insn->offset + insn->len + insn->immediate;
			insn->call_dest = find_symbol_by_offset(insn->sec,
								dest_off);

			if (!insn->call_dest && !insn->ignore) {
				WARN_FUNC("unsupported intra-function call",
					  insn->sec, insn->offset);
				if (retpoline)
					WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
				return -1;
			}

		} else if (rela->sym->type == STT_SECTION) {
			insn->call_dest = find_symbol_by_offset(rela->sym->sec,
								rela->addend+4);
			if (!insn->call_dest ||
			    insn->call_dest->type != STT_FUNC) {
				WARN_FUNC("can't find call dest symbol at %s+0x%x",
					  insn->sec, insn->offset,
					  rela->sym->sec->name,
					  rela->addend + 4);
				return -1;
			}
		} else
			insn->call_dest = rela->sym;
	}

	return 0;
}

/*
 * The .alternatives section requires some extra special care, over and above
 * what other special sections require:
 *
 * 1. Because alternatives are patched in-place, we need to insert a fake jump
 *    instruction at the end so that validate_branch() skips all the original
 *    replaced instructions when validating the new instruction path.
 *
 * 2. An added wrinkle is that the new instruction length might be zero.  In
 *    that case the old instructions are replaced with noops.  We simulate that
 *    by creating a fake jump as the only new instruction.
 *
 * 3. In some cases, the alternative section includes an instruction which
 *    conditionally jumps to the _end_ of the entry.  We have to modify these
 *    jumps' destinations to point back to .text rather than the end of the
 *    entry in .altinstr_replacement.
 */
static int handle_group_alt(struct objtool_file *file,
			    struct special_alt *special_alt,
			    struct instruction *orig_insn,
			    struct instruction **new_insn)
{
	struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
	unsigned long dest_off;

	last_orig_insn = NULL;
	insn = orig_insn;
	sec_for_each_insn_from(file, insn) {
		if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
			break;

		insn->alt_group = true;
		last_orig_insn = insn;
	}

	if (next_insn_same_sec(file, last_orig_insn)) {
		fake_jump = malloc(sizeof(*fake_jump));
		if (!fake_jump) {
			WARN("malloc failed");
			return -1;
		}
		memset(fake_jump, 0, sizeof(*fake_jump));
		INIT_LIST_HEAD(&fake_jump->alts);
		clear_insn_state(&fake_jump->state);

		fake_jump->sec = special_alt->new_sec;
		fake_jump->offset = FAKE_JUMP_OFFSET;
		fake_jump->type = INSN_JUMP_UNCONDITIONAL;
		fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
		fake_jump->func = orig_insn->func;
	}

	if (!special_alt->new_len) {
		if (!fake_jump) {
			WARN("%s: empty alternative at end of section",
			     special_alt->orig_sec->name);
			return -1;
		}

		*new_insn = fake_jump;
		return 0;
	}

	last_new_insn = NULL;
	insn = *new_insn;
	sec_for_each_insn_from(file, insn) {
		if (insn->offset >= special_alt->new_off + special_alt->new_len)
			break;

		last_new_insn = insn;

		insn->ignore = orig_insn->ignore_alts;
		insn->func = orig_insn->func;

		if (insn->type != INSN_JUMP_CONDITIONAL &&
		    insn->type != INSN_JUMP_UNCONDITIONAL)
			continue;

		if (!insn->immediate)
			continue;

		dest_off = insn->offset + insn->len + insn->immediate;
		if (dest_off == special_alt->new_off + special_alt->new_len) {
			if (!fake_jump) {
				WARN("%s: alternative jump to end of section",
				     special_alt->orig_sec->name);
				return -1;
			}
			insn->jump_dest = fake_jump;
		}

		if (!insn->jump_dest) {
			WARN_FUNC("can't find alternative jump destination",
				  insn->sec, insn->offset);
			return -1;
		}
	}

	if (!last_new_insn) {
		WARN_FUNC("can't find last new alternative instruction",
			  special_alt->new_sec, special_alt->new_off);
		return -1;
	}

	if (fake_jump)
		list_add(&fake_jump->list, &last_new_insn->list);

	return 0;
}

/*
 * A jump table entry can either convert a nop to a jump or a jump to a nop.
 * If the original instruction is a jump, make the alt entry an effective nop
 * by just skipping the original instruction.
 */
static int handle_jump_alt(struct objtool_file *file,
			   struct special_alt *special_alt,
			   struct instruction *orig_insn,
			   struct instruction **new_insn)
{
	if (orig_insn->type == INSN_NOP)
		return 0;

	if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
		WARN_FUNC("unsupported instruction at jump label",
			  orig_insn->sec, orig_insn->offset);
		return -1;
	}

	*new_insn = list_next_entry(orig_insn, list);
	return 0;
}

/*
 * Read all the special sections which have alternate instructions which can be
 * patched in or redirected to at runtime.  Each instruction having alternate
 * instruction(s) has them added to its insn->alts list, which will be
 * traversed in validate_branch().
 */
static int add_special_section_alts(struct objtool_file *file)
{
	struct list_head special_alts;
	struct instruction *orig_insn, *new_insn;
	struct special_alt *special_alt, *tmp;
	struct alternative *alt;
	int ret;

	ret = special_get_alts(file->elf, &special_alts);
	if (ret)
		return ret;

	list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {

		orig_insn = find_insn(file, special_alt->orig_sec,
				      special_alt->orig_off);
		if (!orig_insn) {
			WARN_FUNC("special: can't find orig instruction",
				  special_alt->orig_sec, special_alt->orig_off);
			ret = -1;
			goto out;
		}

		new_insn = NULL;
		if (!special_alt->group || special_alt->new_len) {
			new_insn = find_insn(file, special_alt->new_sec,
					     special_alt->new_off);
			if (!new_insn) {
				WARN_FUNC("special: can't find new instruction",
					  special_alt->new_sec,
					  special_alt->new_off);
				ret = -1;
				goto out;
			}
		}

		if (special_alt->group) {
			if (!special_alt->orig_len) {
				WARN_FUNC("empty alternative entry",
					  orig_insn->sec, orig_insn->offset);
				continue;
			}

			ret = handle_group_alt(file, special_alt, orig_insn,
					       &new_insn);
			if (ret)
				goto out;
		} else if (special_alt->jump_or_nop) {
			ret = handle_jump_alt(file, special_alt, orig_insn,
					      &new_insn);
			if (ret)
				goto out;
		}

		alt = malloc(sizeof(*alt));
		if (!alt) {
			WARN("malloc failed");
			ret = -1;
			goto out;
		}

		alt->insn = new_insn;
		alt->skip_orig = special_alt->skip_orig;
		orig_insn->ignore_alts |= special_alt->skip_alt;
		list_add_tail(&alt->list, &orig_insn->alts);

		list_del(&special_alt->list);
		free(special_alt);
	}

out:
	return ret;
}

static int add_jump_table(struct objtool_file *file, struct instruction *insn,
			    struct rela *table)
{
	struct rela *rela = table;
	struct instruction *dest_insn;
	struct alternative *alt;
	struct symbol *pfunc = insn->func->pfunc;
	unsigned int prev_offset = 0;

	/*
	 * Each @rela is a switch table relocation which points to the target
	 * instruction.
	 */
	list_for_each_entry_from(rela, &table->sec->rela_list, list) {

		/* Check for the end of the table: */
		if (rela != table && rela->jump_table_start)
			break;

		/* Make sure the table entries are consecutive: */
		if (prev_offset && rela->offset != prev_offset + 8)
			break;

		/* Detect function pointers from contiguous objects: */
		if (rela->sym->sec == pfunc->sec &&
		    rela->addend == pfunc->offset)
			break;

		dest_insn = find_insn(file, rela->sym->sec, rela->addend);
		if (!dest_insn)
			break;

		/* Make sure the destination is in the same function: */
		if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
			break;

		alt = malloc(sizeof(*alt));
		if (!alt) {
			WARN("malloc failed");
			return -1;
		}

		alt->insn = dest_insn;
		list_add_tail(&alt->list, &insn->alts);
		prev_offset = rela->offset;
	}

	if (!prev_offset) {
		WARN_FUNC("can't find switch jump table",
			  insn->sec, insn->offset);
		return -1;
	}

	return 0;
}

/*
 * find_jump_table() - Given a dynamic jump, find the switch jump table in
 * .rodata associated with it.
 *
 * There are 3 basic patterns:
 *
 * 1. jmpq *[rodata addr](,%reg,8)
 *
 *    This is the most common case by far.  It jumps to an address in a simple
 *    jump table which is stored in .rodata.
 *
 * 2. jmpq *[rodata addr](%rip)
 *
 *    This is caused by a rare GCC quirk, currently only seen in three driver
 *    functions in the kernel, only with certain obscure non-distro configs.
 *
 *    As part of an optimization, GCC makes a copy of an existing switch jump
 *    table, modifies it, and then hard-codes the jump (albeit with an indirect
 *    jump) to use a single entry in the table.  The rest of the jump table and
 *    some of its jump targets remain as dead code.
 *
 *    In such a case we can just crudely ignore all unreachable instruction
 *    warnings for the entire object file.  Ideally we would just ignore them
 *    for the function, but that would require redesigning the code quite a
 *    bit.  And honestly that's just not worth doing: unreachable instruction
 *    warnings are of questionable value anyway, and this is such a rare issue.
 *
 * 3. mov [rodata addr],%reg1
 *    ... some instructions ...
 *    jmpq *(%reg1,%reg2,8)
 *
 *    This is a fairly uncommon pattern which is new for GCC 6.  As of this
 *    writing, there are 11 occurrences of it in the allmodconfig kernel.
 *
 *    As of GCC 7 there are quite a few more of these and the 'in between' code
 *    is significant. Esp. with KASAN enabled some of the code between the mov
 *    and jmpq uses .rodata itself, which can confuse things.
 *
 *    TODO: Once we have DWARF CFI and smarter instruction decoding logic,
 *    ensure the same register is used in the mov and jump instructions.
 *
 *    NOTE: RETPOLINE made it harder still to decode dynamic jumps.
 */
static struct rela *find_jump_table(struct objtool_file *file,
				      struct symbol *func,
				      struct instruction *insn)
{
	struct rela *text_rela, *table_rela;
	struct instruction *orig_insn = insn;
	struct section *table_sec;
	unsigned long table_offset;

	/*
	 * Backward search using the @first_jump_src links, these help avoid
	 * much of the 'in between' code. Which avoids us getting confused by
	 * it.
	 */
	for (;
	     &insn->list != &file->insn_list && insn->func && insn->func->pfunc == func;
	     insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {

		if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
			break;

		/* allow small jumps within the range */
		if (insn->type == INSN_JUMP_UNCONDITIONAL &&
		    insn->jump_dest &&
		    (insn->jump_dest->offset <= insn->offset ||
		     insn->jump_dest->offset > orig_insn->offset))
		    break;

		/* look for a relocation which references .rodata */
		text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
						    insn->len);
		if (!text_rela || text_rela->sym->type != STT_SECTION ||
		    !text_rela->sym->sec->rodata)
			continue;

		table_offset = text_rela->addend;
		table_sec = text_rela->sym->sec;

		if (text_rela->type == R_X86_64_PC32)
			table_offset += 4;

		/*
		 * Make sure the .rodata address isn't associated with a
		 * symbol.  GCC jump tables are anonymous data.
		 *
		 * Also support C jump tables which are in the same format as
		 * switch jump tables.  For objtool to recognize them, they
		 * need to be placed in the C_JUMP_TABLE_SECTION section.  They
		 * have symbols associated with them.
		 */
		if (find_symbol_containing(table_sec, table_offset) &&
		    strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
			continue;

		/* Each table entry has a rela associated with it. */
		table_rela = find_rela_by_dest(table_sec, table_offset);
		if (!table_rela)
			continue;

		/*
		 * Use of RIP-relative switch jumps is quite rare, and
		 * indicates a rare GCC quirk/bug which can leave dead code
		 * behind.
		 */
		if (text_rela->type == R_X86_64_PC32)
			file->ignore_unreachables = true;

		return table_rela;
	}

	return NULL;
}

/*
 * First pass: Mark the head of each jump table so that in the next pass,
 * we know when a given jump table ends and the next one starts.
 */
static void mark_func_jump_tables(struct objtool_file *file,
				    struct symbol *func)
{
	struct instruction *insn, *last = NULL;
	struct rela *rela;

	func_for_each_insn_all(file, func, insn) {
		if (!last)
			last = insn;

		/*
		 * Store back-pointers for unconditional forward jumps such
		 * that find_jump_table() can back-track using those and
		 * avoid some potentially confusing code.
		 */
		if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
		    insn->offset > last->offset &&
		    insn->jump_dest->offset > insn->offset &&
		    !insn->jump_dest->first_jump_src) {

			insn->jump_dest->first_jump_src = insn;
			last = insn->jump_dest;
		}

		if (insn->type != INSN_JUMP_DYNAMIC)
			continue;

		rela = find_jump_table(file, func, insn);
		if (rela) {
			rela->jump_table_start = true;
			insn->jump_table = rela;
		}
	}
}

static int add_func_jump_tables(struct objtool_file *file,
				  struct symbol *func)
{
	struct instruction *insn;
	int ret;

	func_for_each_insn_all(file, func, insn) {
		if (!insn->jump_table)
			continue;

		ret = add_jump_table(file, insn, insn->jump_table);
		if (ret)
			return ret;
	}

	return 0;
}

/*
 * For some switch statements, gcc generates a jump table in the .rodata
 * section which contains a list of addresses within the function to jump to.
 * This finds these jump tables and adds them to the insn->alts lists.
 */
static int add_jump_table_alts(struct objtool_file *file)
{
	struct section *sec;
	struct symbol *func;
	int ret;

	if (!file->rodata)
		return 0;

	for_each_sec(file, sec) {
		list_for_each_entry(func, &sec->symbol_list, list) {
			if (func->type != STT_FUNC)
				continue;

			mark_func_jump_tables(file, func);
			ret = add_func_jump_tables(file, func);
			if (ret)
				return ret;
		}
	}

	return 0;
}

static int read_unwind_hints(struct objtool_file *file)
{
	struct section *sec, *relasec;
	struct rela *rela;
	struct unwind_hint *hint;
	struct instruction *insn;
	struct cfi_reg *cfa;
	int i;

	sec = find_section_by_name(file->elf, ".discard.unwind_hints");
	if (!sec)
		return 0;

	relasec = sec->rela;
	if (!relasec) {
		WARN("missing .rela.discard.unwind_hints section");
		return -1;
	}

	if (sec->len % sizeof(struct unwind_hint)) {
		WARN("struct unwind_hint size mismatch");
		return -1;
	}

	file->hints = true;

	for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
		hint = (struct unwind_hint *)sec->data->d_buf + i;

		rela = find_rela_by_dest(sec, i * sizeof(*hint));
		if (!rela) {
			WARN("can't find rela for unwind_hints[%d]", i);
			return -1;
		}

		insn = find_insn(file, rela->sym->sec, rela->addend);
		if (!insn) {
			WARN("can't find insn for unwind_hints[%d]", i);
			return -1;
		}

		cfa = &insn->state.cfa;

		if (hint->type == UNWIND_HINT_TYPE_SAVE) {
			insn->save = true;
			continue;

		} else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
			insn->restore = true;
			insn->hint = true;
			continue;
		}

		insn->hint = true;

		switch (hint->sp_reg) {
		case ORC_REG_UNDEFINED:
			cfa->base = CFI_UNDEFINED;
			break;
		case ORC_REG_SP:
			cfa->base = CFI_SP;
			break;
		case ORC_REG_BP:
			cfa->base = CFI_BP;
			break;
		case ORC_REG_SP_INDIRECT:
			cfa->base = CFI_SP_INDIRECT;
			break;
		case ORC_REG_R10:
			cfa->base = CFI_R10;
			break;
		case ORC_REG_R13:
			cfa->base = CFI_R13;
			break;
		case ORC_REG_DI:
			cfa->base = CFI_DI;
			break;
		case ORC_REG_DX:
			cfa->base = CFI_DX;
			break;
		default:
			WARN_FUNC("unsupported unwind_hint sp base reg %d",
				  insn->sec, insn->offset, hint->sp_reg);
			return -1;
		}

		cfa->offset = hint->sp_offset;
		insn->state.type = hint->type;
		insn->state.end = hint->end;
	}

	return 0;
}

static int read_retpoline_hints(struct objtool_file *file)
{
	struct section *sec;
	struct instruction *insn;
	struct rela *rela;

	sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
	if (!sec)
		return 0;

	list_for_each_entry(rela, &sec->rela_list, list) {
		if (rela->sym->type != STT_SECTION) {
			WARN("unexpected relocation symbol type in %s", sec->name);
			return -1;
		}

		insn = find_insn(file, rela->sym->sec, rela->addend);
		if (!insn) {
			WARN("bad .discard.retpoline_safe entry");
			return -1;
		}

		if (insn->type != INSN_JUMP_DYNAMIC &&
		    insn->type != INSN_CALL_DYNAMIC) {
			WARN_FUNC("retpoline_safe hint not an indirect jump/call",
				  insn->sec, insn->offset);
			return -1;
		}

		insn->retpoline_safe = true;
	}

	return 0;
}

static void mark_rodata(struct objtool_file *file)
{
	struct section *sec;
	bool found = false;

	/*
	 * Search for the following rodata sections, each of which can
	 * potentially contain jump tables:
	 *
	 * - .rodata: can contain GCC switch tables
	 * - .rodata.<func>: same, if -fdata-sections is being used
	 * - .rodata..c_jump_table: contains C annotated jump tables
	 *
	 * .rodata.str1.* sections are ignored; they don't contain jump tables.
	 */
	for_each_sec(file, sec) {
		if ((!strncmp(sec->name, ".rodata", 7) && !strstr(sec->name, ".str1.")) ||
		    !strcmp(sec->name, C_JUMP_TABLE_SECTION)) {
			sec->rodata = true;
			found = true;
		}
	}

	file->rodata = found;
}

static int decode_sections(struct objtool_file *file)
{
	int ret;

	mark_rodata(file);

	ret = decode_instructions(file);
	if (ret)
		return ret;

	ret = add_dead_ends(file);
	if (ret)
		return ret;

	add_ignores(file);
	add_uaccess_safe(file);

	ret = add_ignore_alternatives(file);
	if (ret)
		return ret;

	ret = add_jump_destinations(file);
	if (ret)
		return ret;

	ret = add_special_section_alts(file);
	if (ret)
		return ret;

	ret = add_call_destinations(file);
	if (ret)
		return ret;

	ret = add_jump_table_alts(file);
	if (ret)
		return ret;

	ret = read_unwind_hints(file);
	if (ret)
		return ret;

	ret = read_retpoline_hints(file);
	if (ret)
		return ret;

	return 0;
}

static bool is_fentry_call(struct instruction *insn)
{
	if (insn->type == INSN_CALL &&
	    insn->call_dest->type == STT_NOTYPE &&
	    !strcmp(insn->call_dest->name, "__fentry__"))
		return true;

	return false;
}

static bool has_modified_stack_frame(struct insn_state *state)
{
	int i;

	if (state->cfa.base != initial_func_cfi.cfa.base ||
	    state->cfa.offset != initial_func_cfi.cfa.offset ||
	    state->stack_size != initial_func_cfi.cfa.offset ||
	    state->drap)
		return true;

	for (i = 0; i < CFI_NUM_REGS; i++)
		if (state->regs[i].base != initial_func_cfi.regs[i].base ||
		    state->regs[i].offset != initial_func_cfi.regs[i].offset)
			return true;

	return false;
}

static bool has_valid_stack_frame(struct insn_state *state)
{
	if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
	    state->regs[CFI_BP].offset == -16)
		return true;

	if (state->drap && state->regs[CFI_BP].base == CFI_BP)
		return true;

	return false;
}

static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
{
	struct cfi_reg *cfa = &state->cfa;
	struct stack_op *op = &insn->stack_op;

	if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
		return 0;

	/* push */
	if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
		cfa->offset += 8;

	/* pop */
	if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
		cfa->offset -= 8;

	/* add immediate to sp */
	if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
	    op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
		cfa->offset -= op->src.offset;

	return 0;
}

static void save_reg(struct insn_state *state, unsigned char reg, int base,
		     int offset)
{
	if (arch_callee_saved_reg(reg) &&
	    state->regs[reg].base == CFI_UNDEFINED) {
		state->regs[reg].base = base;
		state->regs[reg].offset = offset;
	}
}

static void restore_reg(struct insn_state *state, unsigned char reg)
{
	state->regs[reg].base = CFI_UNDEFINED;
	state->regs[reg].offset = 0;
}

/*
 * A note about DRAP stack alignment:
 *
 * GCC has the concept of a DRAP register, which is used to help keep track of
 * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
 * register.  The typical DRAP pattern is:
 *
 *   4c 8d 54 24 08		lea    0x8(%rsp),%r10
 *   48 83 e4 c0		and    $0xffffffffffffffc0,%rsp
 *   41 ff 72 f8		pushq  -0x8(%r10)
 *   55				push   %rbp
 *   48 89 e5			mov    %rsp,%rbp
 *				(more pushes)
 *   41 52			push   %r10
 *				...
 *   41 5a			pop    %r10
 *				(more pops)
 *   5d				pop    %rbp
 *   49 8d 62 f8		lea    -0x8(%r10),%rsp
 *   c3				retq
 *
 * There are some variations in the epilogues, like:
 *
 *   5b				pop    %rbx
 *   41 5a			pop    %r10
 *   41 5c			pop    %r12
 *   41 5d			pop    %r13
 *   41 5e			pop    %r14
 *   c9				leaveq
 *   49 8d 62 f8		lea    -0x8(%r10),%rsp
 *   c3				retq
 *
 * and:
 *
 *   4c 8b 55 e8		mov    -0x18(%rbp),%r10
 *   48 8b 5d e0		mov    -0x20(%rbp),%rbx
 *   4c 8b 65 f0		mov    -0x10(%rbp),%r12
 *   4c 8b 6d f8		mov    -0x8(%rbp),%r13
 *   c9				leaveq
 *   49 8d 62 f8		lea    -0x8(%r10),%rsp
 *   c3				retq
 *
 * Sometimes r13 is used as the DRAP register, in which case it's saved and
 * restored beforehand:
 *
 *   41 55			push   %r13
 *   4c 8d 6c 24 10		lea    0x10(%rsp),%r13
 *   48 83 e4 f0		and    $0xfffffffffffffff0,%rsp
 *				...
 *   49 8d 65 f0		lea    -0x10(%r13),%rsp
 *   41 5d			pop    %r13
 *   c3				retq
 */
static int update_insn_state(struct instruction *insn, struct insn_state *state)
{
	struct stack_op *op = &insn->stack_op;
	struct cfi_reg *cfa = &state->cfa;
	struct cfi_reg *regs = state->regs;

	/* stack operations don't make sense with an undefined CFA */
	if (cfa->base == CFI_UNDEFINED) {
		if (insn->func) {
			WARN_FUNC("undefined stack state", insn->sec, insn->offset);
			return -1;
		}
		return 0;
	}

	if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
		return update_insn_state_regs(insn, state);

	switch (op->dest.type) {

	case OP_DEST_REG:
		switch (op->src.type) {

		case OP_SRC_REG:
			if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
			    cfa->base == CFI_SP &&
			    regs[CFI_BP].base == CFI_CFA &&
			    regs[CFI_BP].offset == -cfa->offset) {

				/* mov %rsp, %rbp */
				cfa->base = op->dest.reg;
				state->bp_scratch = false;
			}

			else if (op->src.reg == CFI_SP &&
				 op->dest.reg == CFI_BP && state->drap) {

				/* drap: mov %rsp, %rbp */
				regs[CFI_BP].base = CFI_BP;
				regs[CFI_BP].offset = -state->stack_size;
				state->bp_scratch = false;
			}

			else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {

				/*
				 * mov %rsp, %reg
				 *
				 * This is needed for the rare case where GCC
				 * does:
				 *
				 *   mov    %rsp, %rax
				 *   ...
				 *   mov    %rax, %rsp
				 */
				state->vals[op->dest.reg].base = CFI_CFA;
				state->vals[op->dest.reg].offset = -state->stack_size;
			}

			else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
				 cfa->base == CFI_BP) {

				/*
				 * mov %rbp, %rsp
				 *
				 * Restore the original stack pointer (Clang).
				 */
				state->stack_size = -state->regs[CFI_BP].offset;
			}

			else if (op->dest.reg == cfa->base) {

				/* mov %reg, %rsp */
				if (cfa->base == CFI_SP &&
				    state->vals[op->src.reg].base == CFI_CFA) {

					/*
					 * This is needed for the rare case
					 * where GCC does something dumb like:
					 *
					 *   lea    0x8(%rsp), %rcx
					 *   ...
					 *   mov    %rcx, %rsp
					 */
					cfa->offset = -state->vals[op->src.reg].offset;
					state->stack_size = cfa->offset;

				} else {
					cfa->base = CFI_UNDEFINED;
					cfa->offset = 0;
				}
			}

			break;

		case OP_SRC_ADD:
			if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {

				/* add imm, %rsp */
				state->stack_size -= op->src.offset;
				if (cfa->base == CFI_SP)
					cfa->offset -= op->src.offset;
				break;
			}

			if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {

				/* lea disp(%rbp), %rsp */
				state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
				break;
			}

			if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {

				/* drap: lea disp(%rsp), %drap */
				state->drap_reg = op->dest.reg;

				/*
				 * lea disp(%rsp), %reg
				 *
				 * This is needed for the rare case where GCC
				 * does something dumb like:
				 *
				 *   lea    0x8(%rsp), %rcx
				 *   ...
				 *   mov    %rcx, %rsp
				 */
				state->vals[op->dest.reg].base = CFI_CFA;
				state->vals[op->dest.reg].offset = \
					-state->stack_size + op->src.offset;

				break;
			}

			if (state->drap && op->dest.reg == CFI_SP &&
			    op->src.reg == state->drap_reg) {

				 /* drap: lea disp(%drap), %rsp */
				cfa->base = CFI_SP;
				cfa->offset = state->stack_size = -op->src.offset;
				state->drap_reg = CFI_UNDEFINED;
				state->drap = false;
				break;
			}

			if (op->dest.reg == state->cfa.base) {
				WARN_FUNC("unsupported stack register modification",
					  insn->sec, insn->offset);
				return -1;
			}

			break;

		case OP_SRC_AND:
			if (op->dest.reg != CFI_SP ||
			    (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
			    (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
				WARN_FUNC("unsupported stack pointer realignment",
					  insn->sec, insn->offset);
				return -1;
			}

			if (state->drap_reg != CFI_UNDEFINED) {
				/* drap: and imm, %rsp */
				cfa->base = state->drap_reg;
				cfa->offset = state->stack_size = 0;
				state->drap = true;
			}

			/*
			 * Older versions of GCC (4.8ish) realign the stack
			 * without DRAP, with a frame pointer.
			 */

			break;

		case OP_SRC_POP:
		case OP_SRC_POPF:
			if (!state->drap && op->dest.type == OP_DEST_REG &&
			    op->dest.reg == cfa->base) {

				/* pop %rbp */
				cfa->base = CFI_SP;
			}

			if (state->drap && cfa->base == CFI_BP_INDIRECT &&
			    op->dest.type == OP_DEST_REG &&
			    op->dest.reg == state->drap_reg &&
			    state->drap_offset == -state->stack_size) {

				/* drap: pop %drap */
				cfa->base = state->drap_reg;
				cfa->offset = 0;
				state->drap_offset = -1;

			} else if (regs[op->dest.reg].offset == -state->stack_size) {

				/* pop %reg */
				restore_reg(state, op->dest.reg);
			}

			state->stack_size -= 8;
			if (cfa->base == CFI_SP)
				cfa->offset -= 8;

			break;

		case OP_SRC_REG_INDIRECT:
			if (state->drap && op->src.reg == CFI_BP &&
			    op->src.offset == state->drap_offset) {

				/* drap: mov disp(%rbp), %drap */
				cfa->base = state->drap_reg;
				cfa->offset = 0;
				state->drap_offset = -1;
			}

			if (state->drap && op->src.reg == CFI_BP &&
			    op->src.offset == regs[op->dest.reg].offset) {

				/* drap: mov disp(%rbp), %reg */
				restore_reg(state, op->dest.reg);

			} else if (op->src.reg == cfa->base &&
			    op->src.offset == regs[op->dest.reg].offset + cfa->offset) {

				/* mov disp(%rbp), %reg */
				/* mov disp(%rsp), %reg */
				restore_reg(state, op->dest.reg);
			}

			break;

		default:
			WARN_FUNC("unknown stack-related instruction",
				  insn->sec, insn->offset);
			return -1;
		}

		break;

	case OP_DEST_PUSH:
	case OP_DEST_PUSHF:
		state->stack_size += 8;
		if (cfa->base == CFI_SP)
			cfa->offset += 8;

		if (op->src.type != OP_SRC_REG)
			break;

		if (state->drap) {
			if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {

				/* drap: push %drap */
				cfa->base = CFI_BP_INDIRECT;
				cfa->offset = -state->stack_size;

				/* save drap so we know when to restore it */
				state->drap_offset = -state->stack_size;

			} else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {

				/* drap: push %rbp */
				state->stack_size = 0;

			} else if (regs[op->src.reg].base == CFI_UNDEFINED) {

				/* drap: push %reg */
				save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
			}

		} else {

			/* push %reg */
			save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
		}

		/* detect when asm code uses rbp as a scratch register */
		if (!no_fp && insn->func && op->src.reg == CFI_BP &&
		    cfa->base != CFI_BP)
			state->bp_scratch = true;
		break;

	case OP_DEST_REG_INDIRECT:

		if (state->drap) {
			if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {

				/* drap: mov %drap, disp(%rbp) */
				cfa->base = CFI_BP_INDIRECT;
				cfa->offset = op->dest.offset;

				/* save drap offset so we know when to restore it */
				state->drap_offset = op->dest.offset;
			}

			else if (regs[op->src.reg].base == CFI_UNDEFINED) {

				/* drap: mov reg, disp(%rbp) */
				save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
			}

		} else if (op->dest.reg == cfa->base) {

			/* mov reg, disp(%rbp) */
			/* mov reg, disp(%rsp) */
			save_reg(state, op->src.reg, CFI_CFA,
				 op->dest.offset - state->cfa.offset);
		}

		break;

	case OP_DEST_LEAVE:
		if ((!state->drap && cfa->base != CFI_BP) ||
		    (state->drap && cfa->base != state->drap_reg)) {
			WARN_FUNC("leave instruction with modified stack frame",
				  insn->sec, insn->offset);
			return -1;
		}

		/* leave (mov %rbp, %rsp; pop %rbp) */

		state->stack_size = -state->regs[CFI_BP].offset - 8;
		restore_reg(state, CFI_BP);

		if (!state->drap) {
			cfa->base = CFI_SP;
			cfa->offset -= 8;
		}

		break;

	case OP_DEST_MEM:
		if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
			WARN_FUNC("unknown stack-related memory operation",
				  insn->sec, insn->offset);
			return -1;
		}

		/* pop mem */
		state->stack_size -= 8;
		if (cfa->base == CFI_SP)
			cfa->offset -= 8;

		break;

	default:
		WARN_FUNC("unknown stack-related instruction",
			  insn->sec, insn->offset);
		return -1;
	}

	return 0;
}

static bool insn_state_match(struct instruction *insn, struct insn_state *state)
{
	struct insn_state *state1 = &insn->state, *state2 = state;
	int i;

	if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
		WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
			  insn->sec, insn->offset,
			  state1->cfa.base, state1->cfa.offset,
			  state2->cfa.base, state2->cfa.offset);

	} else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
		for (i = 0; i < CFI_NUM_REGS; i++) {
			if (!memcmp(&state1->regs[i], &state2->regs[i],
				    sizeof(struct cfi_reg)))
				continue;

			WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
				  insn->sec, insn->offset,
				  i, state1->regs[i].base, state1->regs[i].offset,
				  i, state2->regs[i].base, state2->regs[i].offset);
			break;
		}

	} else if (state1->type != state2->type) {
		WARN_FUNC("stack state mismatch: type1=%d type2=%d",
			  insn->sec, insn->offset, state1->type, state2->type);

	} else if (state1->drap != state2->drap ||
		 (state1->drap && state1->drap_reg != state2->drap_reg) ||
		 (state1->drap && state1->drap_offset != state2->drap_offset)) {
		WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
			  insn->sec, insn->offset,
			  state1->drap, state1->drap_reg, state1->drap_offset,
			  state2->drap, state2->drap_reg, state2->drap_offset);

	} else
		return true;

	return false;
}

static inline bool func_uaccess_safe(struct symbol *func)
{
	if (func)
		return func->uaccess_safe;

	return false;
}

static inline const char *call_dest_name(struct instruction *insn)
{
	if (insn->call_dest)
		return insn->call_dest->name;

	return "{dynamic}";
}

static int validate_call(struct instruction *insn, struct insn_state *state)
{
	if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
		WARN_FUNC("call to %s() with UACCESS enabled",
				insn->sec, insn->offset, call_dest_name(insn));
		return 1;
	}

	if (state->df) {
		WARN_FUNC("call to %s() with DF set",
				insn->sec, insn->offset, call_dest_name(insn));
		return 1;
	}

	return 0;
}

static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
{
	if (has_modified_stack_frame(state)) {
		WARN_FUNC("sibling call from callable instruction with modified stack frame",
				insn->sec, insn->offset);
		return 1;
	}

	return validate_call(insn, state);
}

/*
 * Follow the branch starting at the given instruction, and recursively follow
 * any other branches (jumps).  Meanwhile, track the frame pointer state at
 * each instruction and validate all the rules described in
 * tools/objtool/Documentation/stack-validation.txt.
 */
static int validate_branch(struct objtool_file *file, struct symbol *func,
			   struct instruction *first, struct insn_state state)
{
	struct alternative *alt;
	struct instruction *insn, *next_insn;
	struct section *sec;
	u8 visited;
	int ret;

	insn = first;
	sec = insn->sec;

	if (insn->alt_group && list_empty(&insn->alts)) {
		WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
			  sec, insn->offset);
		return 1;
	}

	while (1) {
		next_insn = next_insn_same_sec(file, insn);

		if (file->c_file && func && insn->func && func != insn->func->pfunc) {
			WARN("%s() falls through to next function %s()",
			     func->name, insn->func->name);
			return 1;
		}

		if (func && insn->ignore) {
			WARN_FUNC("BUG: why am I validating an ignored function?",
				  sec, insn->offset);
			return 1;
		}

		visited = 1 << state.uaccess;
		if (insn->visited) {
			if (!insn->hint && !insn_state_match(insn, &state))
				return 1;

			if (insn->visited & visited)
				return 0;
		}

		if (insn->hint) {
			if (insn->restore) {
				struct instruction *save_insn, *i;

				i = insn;
				save_insn = NULL;
				func_for_each_insn_continue_reverse(file, func, i) {
					if (i->save) {
						save_insn = i;
						break;
					}
				}

				if (!save_insn) {
					WARN_FUNC("no corresponding CFI save for CFI restore",
						  sec, insn->offset);
					return 1;
				}

				if (!save_insn->visited) {
					/*
					 * Oops, no state to copy yet.
					 * Hopefully we can reach this
					 * instruction from another branch
					 * after the save insn has been
					 * visited.
					 */
					if (insn == first)
						return 0;

					WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
						  sec, insn->offset);
					return 1;
				}

				insn->state = save_insn->state;
			}

			state = insn->state;

		} else
			insn->state = state;

		insn->visited |= visited;

		if (!insn->ignore_alts) {
			bool skip_orig = false;

			list_for_each_entry(alt, &insn->alts, list) {
				if (alt->skip_orig)
					skip_orig = true;

				ret = validate_branch(file, func, alt->insn, state);
				if (ret) {
					if (backtrace)
						BT_FUNC("(alt)", insn);
					return ret;
				}
			}

			if (skip_orig)
				return 0;
		}

		switch (insn->type) {

		case INSN_RETURN:
			if (state.uaccess && !func_uaccess_safe(func)) {
				WARN_FUNC("return with UACCESS enabled", sec, insn->offset);
				return 1;
			}

			if (!state.uaccess && func_uaccess_safe(func)) {
				WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function", sec, insn->offset);
				return 1;
			}

			if (state.df) {
				WARN_FUNC("return with DF set", sec, insn->offset);
				return 1;
			}

			if (func && has_modified_stack_frame(&state)) {
				WARN_FUNC("return with modified stack frame",
					  sec, insn->offset);
				return 1;
			}

			if (state.bp_scratch) {
				WARN("%s uses BP as a scratch register",
				     func->name);
				return 1;
			}

			return 0;

		case INSN_CALL:
		case INSN_CALL_DYNAMIC:
			ret = validate_call(insn, &state);
			if (ret)
				return ret;

			if (!no_fp && func && !is_fentry_call(insn) &&
			    !has_valid_stack_frame(&state)) {
				WARN_FUNC("call without frame pointer save/setup",
					  sec, insn->offset);
				return 1;
			}

			if (dead_end_function(file, insn->call_dest))
				return 0;

			break;

		case INSN_JUMP_CONDITIONAL:
		case INSN_JUMP_UNCONDITIONAL:
			if (func && is_sibling_call(insn)) {
				ret = validate_sibling_call(insn, &state);
				if (ret)
					return ret;

			} else if (insn->jump_dest) {
				ret = validate_branch(file, func,
						      insn->jump_dest, state);
				if (ret) {
					if (backtrace)
						BT_FUNC("(branch)", insn);
					return ret;
				}
			}

			if (insn->type == INSN_JUMP_UNCONDITIONAL)
				return 0;

			break;

		case INSN_JUMP_DYNAMIC:
		case INSN_JUMP_DYNAMIC_CONDITIONAL:
			if (func && is_sibling_call(insn)) {
				ret = validate_sibling_call(insn, &state);
				if (ret)
					return ret;
			}

			if (insn->type == INSN_JUMP_DYNAMIC)
				return 0;

			break;

		case INSN_CONTEXT_SWITCH:
			if (func && (!next_insn || !next_insn->hint)) {
				WARN_FUNC("unsupported instruction in callable function",
					  sec, insn->offset);
				return 1;
			}
			return 0;

		case INSN_STACK:
			if (update_insn_state(insn, &state))
				return 1;

			if (insn->stack_op.dest.type == OP_DEST_PUSHF) {
				if (!state.uaccess_stack) {
					state.uaccess_stack = 1;
				} else if (state.uaccess_stack >> 31) {
					WARN_FUNC("PUSHF stack exhausted", sec, insn->offset);
					return 1;
				}
				state.uaccess_stack <<= 1;
				state.uaccess_stack  |= state.uaccess;
			}

			if (insn->stack_op.src.type == OP_SRC_POPF) {
				if (state.uaccess_stack) {
					state.uaccess = state.uaccess_stack & 1;
					state.uaccess_stack >>= 1;
					if (state.uaccess_stack == 1)
						state.uaccess_stack = 0;
				}
			}

			break;

		case INSN_STAC:
			if (state.uaccess) {
				WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
				return 1;
			}

			state.uaccess = true;
			break;

		case INSN_CLAC:
			if (!state.uaccess && func) {
				WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
				return 1;
			}

			if (func_uaccess_safe(func) && !state.uaccess_stack) {
				WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
				return 1;
			}

			state.uaccess = false;
			break;

		case INSN_STD:
			if (state.df) {
				WARN_FUNC("recursive STD", sec, insn->offset);
				return 1;
			}

			state.df = true;
			break;

		case INSN_CLD:
			if (!state.df && func) {
				WARN_FUNC("redundant CLD", sec, insn->offset);
				return 1;
			}

			state.df = false;
			break;

		default:
			break;
		}

		if (insn->dead_end)
			return 0;

		if (!next_insn) {
			if (state.cfa.base == CFI_UNDEFINED)
				return 0;
			WARN("%s: unexpected end of section", sec->name);
			return 1;
		}

		insn = next_insn;
	}

	return 0;
}

static int validate_unwind_hints(struct objtool_file *file)
{
	struct instruction *insn;
	int ret, warnings = 0;
	struct insn_state state;

	if (!file->hints)
		return 0;

	clear_insn_state(&state);

	for_each_insn(file, insn) {
		if (insn->hint && !insn->visited) {
			ret = validate_branch(file, insn->func, insn, state);
			if (ret && backtrace)
				BT_FUNC("<=== (hint)", insn);
			warnings += ret;
		}
	}

	return warnings;
}

static int validate_retpoline(struct objtool_file *file)
{
	struct instruction *insn;
	int warnings = 0;

	for_each_insn(file, insn) {
		if (insn->type != INSN_JUMP_DYNAMIC &&
		    insn->type != INSN_CALL_DYNAMIC)
			continue;

		if (insn->retpoline_safe)
			continue;

		/*
		 * .init.text code is ran before userspace and thus doesn't
		 * strictly need retpolines, except for modules which are
		 * loaded late, they very much do need retpoline in their
		 * .init.text
		 */
		if (!strcmp(insn->sec->name, ".init.text") && !module)
			continue;

		WARN_FUNC("indirect %s found in RETPOLINE build",
			  insn->sec, insn->offset,
			  insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");

		warnings++;
	}

	return warnings;
}

static bool is_kasan_insn(struct instruction *insn)
{
	return (insn->type == INSN_CALL &&
		!strcmp(insn->call_dest->name, "__asan_handle_no_return"));
}

static bool is_ubsan_insn(struct instruction *insn)
{
	return (insn->type == INSN_CALL &&
		!strcmp(insn->call_dest->name,
			"__ubsan_handle_builtin_unreachable"));
}

static bool ignore_unreachable_insn(struct instruction *insn)
{
	int i;

	if (insn->ignore || insn->type == INSN_NOP)
		return true;

	/*
	 * Ignore any unused exceptions.  This can happen when a whitelisted
	 * function has an exception table entry.
	 *
	 * Also ignore alternative replacement instructions.  This can happen
	 * when a whitelisted function uses one of the ALTERNATIVE macros.
	 */
	if (!strcmp(insn->sec->name, ".fixup") ||
	    !strcmp(insn->sec->name, ".altinstr_replacement") ||
	    !strcmp(insn->sec->name, ".altinstr_aux"))
		return true;

	if (!insn->func)
		return false;

	/*
	 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
	 * __builtin_unreachable().  The BUG() macro has an unreachable() after
	 * the UD2, which causes GCC's undefined trap logic to emit another UD2
	 * (or occasionally a JMP to UD2).
	 */
	if (list_prev_entry(insn, list)->dead_end &&
	    (insn->type == INSN_BUG ||
	     (insn->type == INSN_JUMP_UNCONDITIONAL &&
	      insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
		return true;

	/*
	 * Check if this (or a subsequent) instruction is related to
	 * CONFIG_UBSAN or CONFIG_KASAN.
	 *
	 * End the search at 5 instructions to avoid going into the weeds.
	 */
	for (i = 0; i < 5; i++) {

		if (is_kasan_insn(insn) || is_ubsan_insn(insn))
			return true;

		if (insn->type == INSN_JUMP_UNCONDITIONAL) {
			if (insn->jump_dest &&
			    insn->jump_dest->func == insn->func) {
				insn = insn->jump_dest;
				continue;
			}

			break;
		}

		if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
			break;

		insn = list_next_entry(insn, list);
	}

	return false;
}

static int validate_functions(struct objtool_file *file)
{
	struct section *sec;
	struct symbol *func;
	struct instruction *insn;
	struct insn_state state;
	int ret, warnings = 0;

	clear_insn_state(&state);

	state.cfa = initial_func_cfi.cfa;
	memcpy(&state.regs, &initial_func_cfi.regs,
	       CFI_NUM_REGS * sizeof(struct cfi_reg));
	state.stack_size = initial_func_cfi.cfa.offset;

	for_each_sec(file, sec) {
		list_for_each_entry(func, &sec->symbol_list, list) {
			if (func->type != STT_FUNC)
				continue;

			if (!func->len) {
				WARN("%s() is missing an ELF size annotation",
				     func->name);
				warnings++;
			}

			if (func->pfunc != func || func->alias != func)
				continue;

			insn = find_insn(file, sec, func->offset);
			if (!insn || insn->ignore || insn->visited)
				continue;

			state.uaccess = func->uaccess_safe;

			ret = validate_branch(file, func, insn, state);
			if (ret && backtrace)
				BT_FUNC("<=== (func)", insn);
			warnings += ret;
		}
	}

	return warnings;
}

static int validate_reachable_instructions(struct objtool_file *file)
{
	struct instruction *insn;

	if (file->ignore_unreachables)
		return 0;

	for_each_insn(file, insn) {
		if (insn->visited || ignore_unreachable_insn(insn))
			continue;

		WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
		return 1;
	}

	return 0;
}

static void cleanup(struct objtool_file *file)
{
	struct instruction *insn, *tmpinsn;
	struct alternative *alt, *tmpalt;

	list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
		list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
			list_del(&alt->list);
			free(alt);
		}
		list_del(&insn->list);
		hash_del(&insn->hash);
		free(insn);
	}
	elf_close(file->elf);
}

static struct objtool_file file;

int check(const char *_objname, bool orc)
{
	int ret, warnings = 0;

	objname = _objname;

	file.elf = elf_read(objname, orc ? O_RDWR : O_RDONLY);
	if (!file.elf)
		return 1;

	INIT_LIST_HEAD(&file.insn_list);
	hash_init(file.insn_hash);
	file.c_file = find_section_by_name(file.elf, ".comment");
	file.ignore_unreachables = no_unreachable;
	file.hints = false;

	arch_initial_func_cfi_state(&initial_func_cfi);

	ret = decode_sections(&file);
	if (ret < 0)
		goto out;
	warnings += ret;

	if (list_empty(&file.insn_list))
		goto out;

	if (retpoline) {
		ret = validate_retpoline(&file);
		if (ret < 0)
			return ret;
		warnings += ret;
	}

	ret = validate_functions(&file);
	if (ret < 0)
		goto out;
	warnings += ret;

	ret = validate_unwind_hints(&file);
	if (ret < 0)
		goto out;
	warnings += ret;

	if (!warnings) {
		ret = validate_reachable_instructions(&file);
		if (ret < 0)
			goto out;
		warnings += ret;
	}

	if (orc) {
		ret = create_orc(&file);
		if (ret < 0)
			goto out;

		ret = create_orc_sections(&file);
		if (ret < 0)
			goto out;

		ret = elf_write(file.elf);
		if (ret < 0)
			goto out;
	}

out:
	cleanup(&file);

	/* ignore warnings for now until we get all the code cleaned up */
	if (ret || warnings)
		return 0;
	return 0;
}