summaryrefslogtreecommitdiff
path: root/src/sim/syscall_emul.hh
blob: f7d87d44502101c2f278b647e186e65fafec1ea8 (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
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
/*
 * Copyright (c) 2012-2013, 2015, 2019 ARM Limited
 * Copyright (c) 2015 Advanced Micro Devices, Inc.
 * All rights reserved
 *
 * The license below extends only to copyright in the software and shall
 * not be construed as granting a license to any other intellectual
 * property including but not limited to intellectual property relating
 * to a hardware implementation of the functionality of the software
 * licensed hereunder.  You may use the software subject to the license
 * terms below provided that you ensure that this notice is replicated
 * unmodified and in its entirety in all distributions of the software,
 * modified or unmodified, in source code or in binary form.
 *
 * Copyright (c) 2003-2005 The Regents of The University of Michigan
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * 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;
 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "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 COPYRIGHT
 * OWNER OR CONTRIBUTORS 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.
 *
 * Authors: Steve Reinhardt
 *          Kevin Lim
 */

#ifndef __SIM_SYSCALL_EMUL_HH__
#define __SIM_SYSCALL_EMUL_HH__

#if (defined(__APPLE__) || defined(__OpenBSD__) ||      \
     defined(__FreeBSD__) || defined(__CYGWIN__) ||     \
     defined(__NetBSD__))
#define NO_STAT64 1
#else
#define NO_STAT64 0
#endif

///
/// @file syscall_emul.hh
///
/// This file defines objects used to emulate syscalls from the target
/// application on the host machine.

#if defined(__linux__)
#include <sys/eventfd.h>
#include <sys/statfs.h>

#else
#include <sys/mount.h>

#endif

#ifdef __CYGWIN32__
#include <sys/fcntl.h>

#endif
#include <fcntl.h>
#include <net/if.h>
#include <poll.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>

#include <cerrno>
#include <memory>
#include <string>

#include "arch/generic/tlb.hh"
#include "arch/utility.hh"
#include "base/intmath.hh"
#include "base/loader/object_file.hh"
#include "base/logging.hh"
#include "base/trace.hh"
#include "base/types.hh"
#include "config/the_isa.hh"
#include "cpu/base.hh"
#include "cpu/thread_context.hh"
#include "mem/page_table.hh"
#include "params/Process.hh"
#include "sim/emul_driver.hh"
#include "sim/futex_map.hh"
#include "sim/process.hh"
#include "sim/syscall_debug_macros.hh"
#include "sim/syscall_desc.hh"
#include "sim/syscall_emul_buf.hh"
#include "sim/syscall_return.hh"

#if defined(__APPLE__) && defined(__MACH__) && !defined(CMSG_ALIGN)
#define CMSG_ALIGN(len) (((len) + sizeof(size_t) - 1) & ~(sizeof(size_t) - 1))
#endif

//////////////////////////////////////////////////////////////////////
//
// The following emulation functions are generic enough that they
// don't need to be recompiled for different emulated OS's.  They are
// defined in sim/syscall_emul.cc.
//
//////////////////////////////////////////////////////////////////////

void warnUnsupportedOS(std::string syscall_name);

/// Handler for unimplemented syscalls that we haven't thought about.
SyscallReturn unimplementedFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Handler for unimplemented syscalls that we never intend to
/// implement (signal handling, etc.) and should not affect the correct
/// behavior of the program.  Prints a warning.  Return success to the target
/// program.
SyscallReturn ignoreFunc(SyscallDesc *desc, int num, ThreadContext *tc);
/// Like above, but only prints a warning once per syscall desc it's used with.
SyscallReturn
ignoreWarnOnceFunc(SyscallDesc *desc, int num, ThreadContext *tc);

// Target fallocateFunc() handler.
SyscallReturn fallocateFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target exit() handler: terminate current context.
SyscallReturn exitFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target exit_group() handler: terminate simulation. (exit all threads)
SyscallReturn exitGroupFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target set_tid_address() handler.
SyscallReturn setTidAddressFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target getpagesize() handler.
SyscallReturn getpagesizeFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target brk() handler: set brk address.
SyscallReturn brkFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target close() handler.
SyscallReturn closeFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target lseek() handler.
SyscallReturn lseekFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target _llseek() handler.
SyscallReturn _llseekFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target munmap() handler.
SyscallReturn munmapFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target shutdown() handler.
SyscallReturn shutdownFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target gethostname() handler.
SyscallReturn gethostnameFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target getcwd() handler.
SyscallReturn getcwdFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target readlink() handler.
SyscallReturn readlinkImpl(SyscallDesc *desc, int num, ThreadContext *tc,
                           int index);
SyscallReturn readlinkFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target unlink() handler.
SyscallReturn unlinkHelper(SyscallDesc *desc, int num, ThreadContext *tc,
                           int index);
SyscallReturn unlinkFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target link() handler
SyscallReturn linkFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target symlink() handler.
SyscallReturn symlinkFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target mkdir() handler.
SyscallReturn mkdirFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target mknod() handler.
SyscallReturn mknodFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target chdir() handler.
SyscallReturn chdirFunc(SyscallDesc *desc, int num, ThreadContext *tc);

// Target rmdir() handler.
SyscallReturn rmdirFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target rename() handler.
SyscallReturn renameFunc(SyscallDesc *desc, int num, ThreadContext *tc);


/// Target truncate() handler.
SyscallReturn truncateFunc(SyscallDesc *desc, int num, ThreadContext *tc);


/// Target ftruncate() handler.
SyscallReturn ftruncateFunc(SyscallDesc *desc, int num, ThreadContext *tc);


/// Target truncate64() handler.
SyscallReturn truncate64Func(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target ftruncate64() handler.
SyscallReturn ftruncate64Func(SyscallDesc *desc, int num, ThreadContext *tc);


/// Target umask() handler.
SyscallReturn umaskFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target gettid() handler.
SyscallReturn gettidFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target chown() handler.
SyscallReturn chownFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target getpgrpFunc() handler.
SyscallReturn getpgrpFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target setpgid() handler.
SyscallReturn setpgidFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target fchown() handler.
SyscallReturn fchownFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target dup() handler.
SyscallReturn dupFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target dup2() handler.
SyscallReturn dup2Func(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target fcntl() handler.
SyscallReturn fcntlFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target fcntl64() handler.
SyscallReturn fcntl64Func(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target setuid() handler.
SyscallReturn setuidFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target pipe() handler.
SyscallReturn pipeFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Internal pipe() handler.
SyscallReturn pipeImpl(SyscallDesc *desc, int num, ThreadContext *tc,
                       bool pseudo_pipe, bool is_pipe2=false);

/// Target pipe() handler.
SyscallReturn pipe2Func(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target getpid() handler.
SyscallReturn getpidFunc(SyscallDesc *desc, int num, ThreadContext *tc);

// Target getpeername() handler.
SyscallReturn getpeernameFunc(SyscallDesc *desc, int num, ThreadContext *tc);

// Target bind() handler.
SyscallReturn bindFunc(SyscallDesc *desc, int num, ThreadContext *tc);

// Target listen() handler.
SyscallReturn listenFunc(SyscallDesc *desc, int num, ThreadContext *tc);

// Target connect() handler.
SyscallReturn connectFunc(SyscallDesc *desc, int num, ThreadContext *tc);

#if defined(SYS_getdents)
// Target getdents() handler.
SyscallReturn getdentsFunc(SyscallDesc *desc, int num, ThreadContext *tc);
#endif

#if defined(SYS_getdents64)
// Target getdents() handler.
SyscallReturn getdents64Func(SyscallDesc *desc, int num, ThreadContext *tc);
#endif

// Target sendto() handler.
SyscallReturn sendtoFunc(SyscallDesc *desc, int num, ThreadContext *tc);

// Target recvfrom() handler.
SyscallReturn recvfromFunc(SyscallDesc *desc, int num, ThreadContext *tc);

// Target recvmsg() handler.
SyscallReturn recvmsgFunc(SyscallDesc *desc, int num, ThreadContext *tc);

// Target sendmsg() handler.
SyscallReturn sendmsgFunc(SyscallDesc *desc, int num, ThreadContext *tc);

// Target getuid() handler.
SyscallReturn getuidFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target getgid() handler.
SyscallReturn getgidFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target getppid() handler.
SyscallReturn getppidFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target geteuid() handler.
SyscallReturn geteuidFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target getegid() handler.
SyscallReturn getegidFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target access() handler
SyscallReturn accessImpl(SyscallDesc *desc, int num, ThreadContext *tc,
                         int index);
SyscallReturn accessFunc(SyscallDesc *desc, int num, ThreadContext *tc);

// Target getsockopt() handler.
SyscallReturn getsockoptFunc(SyscallDesc *desc, int num, ThreadContext *tc);

// Target setsockopt() handler.
SyscallReturn setsockoptFunc(SyscallDesc *desc, int num, ThreadContext *tc);

// Target getsockname() handler.
SyscallReturn getsocknameFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Futex system call
/// Implemented by Daniel Sanchez
/// Used by printf's in multi-threaded apps
template <class OS>
SyscallReturn
futexFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    using namespace std;

    int index = 0;
    auto process = tc->getProcessPtr();

    Addr uaddr = process->getSyscallArg(tc, index);
    int op = process->getSyscallArg(tc, index);
    int val = process->getSyscallArg(tc, index);
    int timeout M5_VAR_USED = process->getSyscallArg(tc, index);
    Addr uaddr2 M5_VAR_USED = process->getSyscallArg(tc, index);
    int val3 = process->getSyscallArg(tc, index);

    /*
     * Unsupported option that does not affect the correctness of the
     * application. This is a performance optimization utilized by Linux.
     */
    op &= ~OS::TGT_FUTEX_PRIVATE_FLAG;
    op &= ~OS::TGT_FUTEX_CLOCK_REALTIME_FLAG;

    FutexMap &futex_map = tc->getSystemPtr()->futexMap;

    if (OS::TGT_FUTEX_WAIT == op || OS::TGT_FUTEX_WAIT_BITSET == op) {
        // Ensure futex system call accessed atomically.
        BufferArg buf(uaddr, sizeof(int));
        buf.copyIn(tc->getVirtProxy());
        int mem_val = *(int*)buf.bufferPtr();

        /*
         * The value in memory at uaddr is not equal with the expected val
         * (a different thread must have changed it before the system call was
         * invoked). In this case, we need to throw an error.
         */
        if (val != mem_val)
            return -OS::TGT_EWOULDBLOCK;

        if (OS::TGT_FUTEX_WAIT == op) {
            futex_map.suspend(uaddr, process->tgid(), tc);
        } else {
            futex_map.suspend_bitset(uaddr, process->tgid(), tc, val3);
        }

        return 0;
    } else if (OS::TGT_FUTEX_WAKE == op) {
        return futex_map.wakeup(uaddr, process->tgid(), val);
    } else if (OS::TGT_FUTEX_WAKE_BITSET == op) {
        return futex_map.wakeup_bitset(uaddr, process->tgid(), val3);
    } else if (OS::TGT_FUTEX_REQUEUE == op ||
               OS::TGT_FUTEX_CMP_REQUEUE == op) {

        // Ensure futex system call accessed atomically.
        BufferArg buf(uaddr, sizeof(int));
        buf.copyIn(tc->getVirtProxy());
        int mem_val = *(int*)buf.bufferPtr();
        /*
         * For CMP_REQUEUE, the whole operation is only started only if
         * val3 is still the value of the futex pointed to by uaddr.
         */
        if (OS::TGT_FUTEX_CMP_REQUEUE && val3 != mem_val)
            return -OS::TGT_EWOULDBLOCK;
        return futex_map.requeue(uaddr, process->tgid(), val, timeout, uaddr2);
    } else if (OS::TGT_FUTEX_WAKE_OP == op) {
        /*
         * The FUTEX_WAKE_OP operation is equivalent to executing the
         * following code atomically and totally ordered with respect to
         * other futex operations on any of the two supplied futex words:
         *
         *   int oldval = *(int *) addr2;
         *   *(int *) addr2 = oldval op oparg;
         *   futex(addr1, FUTEX_WAKE, val, 0, 0, 0);
         *   if (oldval cmp cmparg)
         *        futex(addr2, FUTEX_WAKE, val2, 0, 0, 0);
         *
         * (op, oparg, cmp, cmparg are encoded in val3)
         *
         * +---+---+-----------+-----------+
         * |op |cmp|   oparg   |  cmparg   |
         * +---+---+-----------+-----------+
         *   4   4       12          12    <== # of bits
         *
         * reference: http://man7.org/linux/man-pages/man2/futex.2.html
         *
         */
        // get value from simulated-space
        BufferArg buf(uaddr2, sizeof(int));
        buf.copyIn(tc->getVirtProxy());
        int oldval = *(int*)buf.bufferPtr();
        int newval = oldval;
        // extract op, oparg, cmp, cmparg from val3
        int wake_cmparg =  val3 & 0xfff;
        int wake_oparg  = (val3 & 0xfff000)   >> 12;
        int wake_cmp    = (val3 & 0xf000000)  >> 24;
        int wake_op     = (val3 & 0xf0000000) >> 28;
        if ((wake_op & OS::TGT_FUTEX_OP_ARG_SHIFT) >> 3 == 1)
            wake_oparg = (1 << wake_oparg);
        wake_op &= ~OS::TGT_FUTEX_OP_ARG_SHIFT;
        // perform operation on the value of the second futex
        if (wake_op == OS::TGT_FUTEX_OP_SET)
            newval = wake_oparg;
        else if (wake_op == OS::TGT_FUTEX_OP_ADD)
            newval += wake_oparg;
        else if (wake_op == OS::TGT_FUTEX_OP_OR)
            newval |= wake_oparg;
        else if (wake_op == OS::TGT_FUTEX_OP_ANDN)
            newval &= ~wake_oparg;
        else if (wake_op == OS::TGT_FUTEX_OP_XOR)
            newval ^= wake_oparg;
        // copy updated value back to simulated-space
        *(int*)buf.bufferPtr() = newval;
        buf.copyOut(tc->getVirtProxy());
        // perform the first wake-up
        int woken1 = futex_map.wakeup(uaddr, process->tgid(), val);
        int woken2 = 0;
        // calculate the condition of the second wake-up
        bool is_wake2 = false;
        if (wake_cmp == OS::TGT_FUTEX_OP_CMP_EQ)
            is_wake2 = oldval == wake_cmparg;
        else if (wake_cmp == OS::TGT_FUTEX_OP_CMP_NE)
            is_wake2 = oldval != wake_cmparg;
        else if (wake_cmp == OS::TGT_FUTEX_OP_CMP_LT)
            is_wake2 = oldval < wake_cmparg;
        else if (wake_cmp == OS::TGT_FUTEX_OP_CMP_LE)
            is_wake2 = oldval <= wake_cmparg;
        else if (wake_cmp == OS::TGT_FUTEX_OP_CMP_GT)
            is_wake2 = oldval > wake_cmparg;
        else if (wake_cmp == OS::TGT_FUTEX_OP_CMP_GE)
            is_wake2 = oldval >= wake_cmparg;
        // perform the second wake-up
        if (is_wake2)
            woken2 = futex_map.wakeup(uaddr2, process->tgid(), timeout);

        return woken1 + woken2;
    }
    warn("futex: op %d not implemented; ignoring.", op);
    return -ENOSYS;
}


/// Pseudo Funcs  - These functions use a different return convension,
/// returning a second value in a register other than the normal return register
SyscallReturn pipePseudoFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target getpidPseudo() handler.
SyscallReturn getpidPseudoFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target getuidPseudo() handler.
SyscallReturn getuidPseudoFunc(SyscallDesc *desc, int num, ThreadContext *tc);

/// Target getgidPseudo() handler.
SyscallReturn getgidPseudoFunc(SyscallDesc *desc, int num, ThreadContext *tc);


/// A readable name for 1,000,000, for converting microseconds to seconds.
const int one_million = 1000000;
/// A readable name for 1,000,000,000, for converting nanoseconds to seconds.
const int one_billion = 1000000000;

/// Approximate seconds since the epoch (1/1/1970).  About a billion,
/// by my reckoning.  We want to keep this a constant (not use the
/// real-world time) to keep simulations repeatable.
const unsigned seconds_since_epoch = 1000000000;

/// Helper function to convert current elapsed time to seconds and
/// microseconds.
template <class T1, class T2>
void
getElapsedTimeMicro(T1 &sec, T2 &usec)
{
    uint64_t elapsed_usecs = curTick() / SimClock::Int::us;
    sec = elapsed_usecs / one_million;
    usec = elapsed_usecs % one_million;
}

/// Helper function to convert current elapsed time to seconds and
/// nanoseconds.
template <class T1, class T2>
void
getElapsedTimeNano(T1 &sec, T2 &nsec)
{
    uint64_t elapsed_nsecs = curTick() / SimClock::Int::ns;
    sec = elapsed_nsecs / one_billion;
    nsec = elapsed_nsecs % one_billion;
}

//////////////////////////////////////////////////////////////////////
//
// The following emulation functions are generic, but need to be
// templated to account for differences in types, constants, etc.
//
//////////////////////////////////////////////////////////////////////

    typedef struct statfs hst_statfs;
#if NO_STAT64
    typedef struct stat hst_stat;
    typedef struct stat hst_stat64;
#else
    typedef struct stat hst_stat;
    typedef struct stat64 hst_stat64;
#endif

//// Helper function to convert a host stat buffer to a target stat
//// buffer.  Also copies the target buffer out to the simulated
//// memory space.  Used by stat(), fstat(), and lstat().

template <typename target_stat, typename host_stat>
void
convertStatBuf(target_stat &tgt, host_stat *host,
               ByteOrder bo, bool fakeTTY=false)
{
    if (fakeTTY)
        tgt->st_dev = 0xA;
    else
        tgt->st_dev = host->st_dev;
    tgt->st_dev = htog(tgt->st_dev, bo);
    tgt->st_ino = host->st_ino;
    tgt->st_ino = htog(tgt->st_ino, bo);
    tgt->st_mode = host->st_mode;
    if (fakeTTY) {
        // Claim to be a character device
        tgt->st_mode &= ~S_IFMT;    // Clear S_IFMT
        tgt->st_mode |= S_IFCHR;    // Set S_IFCHR
    }
    tgt->st_mode = htog(tgt->st_mode, bo);
    tgt->st_nlink = host->st_nlink;
    tgt->st_nlink = htog(tgt->st_nlink, bo);
    tgt->st_uid = host->st_uid;
    tgt->st_uid = htog(tgt->st_uid, bo);
    tgt->st_gid = host->st_gid;
    tgt->st_gid = htog(tgt->st_gid, bo);
    if (fakeTTY)
        tgt->st_rdev = 0x880d;
    else
        tgt->st_rdev = host->st_rdev;
    tgt->st_rdev = htog(tgt->st_rdev, bo);
    tgt->st_size = host->st_size;
    tgt->st_size = htog(tgt->st_size, bo);
    tgt->st_atimeX = host->st_atime;
    tgt->st_atimeX = htog(tgt->st_atimeX, bo);
    tgt->st_mtimeX = host->st_mtime;
    tgt->st_mtimeX = htog(tgt->st_mtimeX, bo);
    tgt->st_ctimeX = host->st_ctime;
    tgt->st_ctimeX = htog(tgt->st_ctimeX, bo);
    // Force the block size to be 8KB. This helps to ensure buffered io works
    // consistently across different hosts.
    tgt->st_blksize = 0x2000;
    tgt->st_blksize = htog(tgt->st_blksize, bo);
    tgt->st_blocks = host->st_blocks;
    tgt->st_blocks = htog(tgt->st_blocks, bo);
}

// Same for stat64

template <typename target_stat, typename host_stat64>
void
convertStat64Buf(target_stat &tgt, host_stat64 *host,
                 ByteOrder bo, bool fakeTTY=false)
{
    convertStatBuf<target_stat, host_stat64>(tgt, host, bo, fakeTTY);
#if defined(STAT_HAVE_NSEC)
    tgt->st_atime_nsec = host->st_atime_nsec;
    tgt->st_atime_nsec = htog(tgt->st_atime_nsec, bo);
    tgt->st_mtime_nsec = host->st_mtime_nsec;
    tgt->st_mtime_nsec = htog(tgt->st_mtime_nsec, bo);
    tgt->st_ctime_nsec = host->st_ctime_nsec;
    tgt->st_ctime_nsec = htog(tgt->st_ctime_nsec, bo);
#else
    tgt->st_atime_nsec = 0;
    tgt->st_mtime_nsec = 0;
    tgt->st_ctime_nsec = 0;
#endif
}

// Here are a couple of convenience functions
template<class OS>
void
copyOutStatBuf(PortProxy &mem, Addr addr,
               hst_stat *host, bool fakeTTY = false)
{
    typedef TypedBufferArg<typename OS::tgt_stat> tgt_stat_buf;
    tgt_stat_buf tgt(addr);
    convertStatBuf<tgt_stat_buf, hst_stat>(tgt, host, OS::byteOrder, fakeTTY);
    tgt.copyOut(mem);
}

template<class OS>
void
copyOutStat64Buf(PortProxy &mem, Addr addr,
                 hst_stat64 *host, bool fakeTTY = false)
{
    typedef TypedBufferArg<typename OS::tgt_stat64> tgt_stat_buf;
    tgt_stat_buf tgt(addr);
    convertStat64Buf<tgt_stat_buf, hst_stat64>(
            tgt, host, OS::byteOrder, fakeTTY);
    tgt.copyOut(mem);
}

template <class OS>
void
copyOutStatfsBuf(PortProxy &mem, Addr addr,
                 hst_statfs *host)
{
    TypedBufferArg<typename OS::tgt_statfs> tgt(addr);

    const ByteOrder bo = OS::byteOrder;

    tgt->f_type = htog(host->f_type, bo);
#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__)
    tgt->f_bsize = htog(host->f_iosize, bo);
#else
    tgt->f_bsize = htog(host->f_bsize, bo);
#endif
    tgt->f_blocks = htog(host->f_blocks, bo);
    tgt->f_bfree = htog(host->f_bfree, bo);
    tgt->f_bavail = htog(host->f_bavail, bo);
    tgt->f_files = htog(host->f_files, bo);
    tgt->f_ffree = htog(host->f_ffree, bo);
    memcpy(&tgt->f_fsid, &host->f_fsid, sizeof(host->f_fsid));
#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__)
    tgt->f_namelen = htog(host->f_namemax, bo);
    tgt->f_frsize = htog(host->f_bsize, bo);
#elif defined(__APPLE__)
    tgt->f_namelen = 0;
    tgt->f_frsize = 0;
#else
    tgt->f_namelen = htog(host->f_namelen, bo);
    tgt->f_frsize = htog(host->f_frsize, bo);
#endif
#if defined(__linux__)
    memcpy(&tgt->f_spare, &host->f_spare, sizeof(host->f_spare));
#else
    /*
     * The fields are different sizes per OS. Don't bother with
     * f_spare or f_reserved on non-Linux for now.
     */
    memset(&tgt->f_spare, 0, sizeof(tgt->f_spare));
#endif

    tgt.copyOut(mem);
}

/// Target ioctl() handler.  For the most part, programs call ioctl()
/// only to find out if their stdout is a tty, to determine whether to
/// do line or block buffering.  We always claim that output fds are
/// not TTYs to provide repeatable results.
template <class OS>
SyscallReturn
ioctlFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();

    int tgt_fd = p->getSyscallArg(tc, index);
    unsigned req = p->getSyscallArg(tc, index);

    DPRINTF_SYSCALL(Verbose, "ioctl(%d, 0x%x, ...)\n", tgt_fd, req);

    if (OS::isTtyReq(req))
        return -ENOTTY;

    auto dfdp = std::dynamic_pointer_cast<DeviceFDEntry>((*p->fds)[tgt_fd]);
    if (dfdp) {
        EmulatedDriver *emul_driver = dfdp->getDriver();
        if (emul_driver)
            return emul_driver->ioctl(tc, req);
    }

    auto sfdp = std::dynamic_pointer_cast<SocketFDEntry>((*p->fds)[tgt_fd]);
    if (sfdp) {
        int status;

        switch (req) {
          case SIOCGIFCONF: {
            Addr conf_addr = p->getSyscallArg(tc, index);
            BufferArg conf_arg(conf_addr, sizeof(ifconf));
            conf_arg.copyIn(tc->getVirtProxy());

            ifconf *conf = (ifconf*)conf_arg.bufferPtr();
            Addr ifc_buf_addr = (Addr)conf->ifc_buf;
            BufferArg ifc_buf_arg(ifc_buf_addr, conf->ifc_len);
            ifc_buf_arg.copyIn(tc->getVirtProxy());

            conf->ifc_buf = (char*)ifc_buf_arg.bufferPtr();

            status = ioctl(sfdp->getSimFD(), req, conf_arg.bufferPtr());
            if (status != -1) {
                conf->ifc_buf = (char*)ifc_buf_addr;
                ifc_buf_arg.copyOut(tc->getVirtProxy());
                conf_arg.copyOut(tc->getVirtProxy());
            }

            return status;
          }
          case SIOCGIFFLAGS:
#if defined(__linux__)
          case SIOCGIFINDEX:
#endif
          case SIOCGIFNETMASK:
          case SIOCGIFADDR:
#if defined(__linux__)
          case SIOCGIFHWADDR:
#endif
          case SIOCGIFMTU: {
            Addr req_addr = p->getSyscallArg(tc, index);
            BufferArg req_arg(req_addr, sizeof(ifreq));
            req_arg.copyIn(tc->getVirtProxy());

            status = ioctl(sfdp->getSimFD(), req, req_arg.bufferPtr());
            if (status != -1)
                req_arg.copyOut(tc->getVirtProxy());
            return status;
          }
        }
    }

    /**
     * For lack of a better return code, return ENOTTY. Ideally, we should
     * return something better here, but at least we issue the warning.
     */
    warn("Unsupported ioctl call (return ENOTTY): ioctl(%d, 0x%x, ...) @ \n",
         tgt_fd, req, tc->pcState());
    return -ENOTTY;
}

template <class OS>
SyscallReturn
openImpl(SyscallDesc *desc, int callnum, ThreadContext *tc, bool isopenat)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    int tgt_dirfd = -1;

    /**
     * If using the openat variant, read in the target directory file
     * descriptor from the simulated process.
     */
    if (isopenat)
        tgt_dirfd = p->getSyscallArg(tc, index);

    /**
     * Retrieve the simulated process' memory proxy and then read in the path
     * string from that memory space into the host's working memory space.
     */
    std::string path;
    if (!tc->getVirtProxy().tryReadString(path, p->getSyscallArg(tc, index)))
        return -EFAULT;

#ifdef __CYGWIN32__
    int host_flags = O_BINARY;
#else
    int host_flags = 0;
#endif
    /**
     * Translate target flags into host flags. Flags exist which are not
     * ported between architectures which can cause check failures.
     */
    int tgt_flags = p->getSyscallArg(tc, index);
    for (int i = 0; i < OS::NUM_OPEN_FLAGS; i++) {
        if (tgt_flags & OS::openFlagTable[i].tgtFlag) {
            tgt_flags &= ~OS::openFlagTable[i].tgtFlag;
            host_flags |= OS::openFlagTable[i].hostFlag;
        }
    }
    if (tgt_flags) {
        warn("open%s: cannot decode flags 0x%x",
             isopenat ? "at" : "", tgt_flags);
    }
#ifdef __CYGWIN32__
    host_flags |= O_BINARY;
#endif

    int mode = p->getSyscallArg(tc, index);

    /**
     * If the simulated process called open or openat with AT_FDCWD specified,
     * take the current working directory value which was passed into the
     * process class as a Python parameter and append the current path to
     * create a full path.
     * Otherwise, openat with a valid target directory file descriptor has
     * been called. If the path option, which was passed in as a parameter,
     * is not absolute, retrieve the directory file descriptor's path and
     * prepend it to the path passed in as a parameter.
     * In every case, we should have a full path (which is relevant to the
     * host) to work with after this block has been passed.
     */
    std::string redir_path = path;
    std::string abs_path = path;
    if (!isopenat || tgt_dirfd == OS::TGT_AT_FDCWD) {
        abs_path = p->absolutePath(path, true);
        redir_path = p->checkPathRedirect(path);
    } else if (!startswith(path, "/")) {
        std::shared_ptr<FDEntry> fdep = ((*p->fds)[tgt_dirfd]);
        auto ffdp = std::dynamic_pointer_cast<FileFDEntry>(fdep);
        if (!ffdp)
            return -EBADF;
        abs_path = ffdp->getFileName() + path;
        redir_path = p->checkPathRedirect(abs_path);
    }

    /**
     * Since this is an emulated environment, we create pseudo file
     * descriptors for device requests that have been registered with
     * the process class through Python; this allows us to create a file
     * descriptor for subsequent ioctl or mmap calls.
     */
    if (startswith(abs_path, "/dev/")) {
        std::string filename = abs_path.substr(strlen("/dev/"));
        EmulatedDriver *drv = p->findDriver(filename);
        if (drv) {
            DPRINTF_SYSCALL(Verbose, "open%s: passing call to "
                            "driver open with path[%s]\n",
                            isopenat ? "at" : "", abs_path.c_str());
            return drv->open(tc, mode, host_flags);
        }
        /**
         * Fall through here for pass through to host devices, such
         * as /dev/zero
         */
    }

    /**
     * We make several attempts resolve a call to open.
     *
     * 1) Resolve any path redirection before hand. This will set the path
     * up with variable 'redir_path' which may contain a modified path or
     * the original path value. This should already be done in prior code.
     * 2) Try to handle the access using 'special_paths'. Some special_paths
     * and files cannot be called on the host and need to be handled as
     * special cases inside the simulator. These special_paths are handled by
     * C++ routines to provide output back to userspace.
     * 3) If the full path that was created above does not match any of the
     * special cases, pass it through to the open call on the __HOST__ to let
     * the host open the file on our behalf. Again, the openImpl tries to
     * USE_THE_HOST_FILESYSTEM_OPEN (with a possible redirection to the
     * faux-filesystem files). The faux-filesystem is dynamically created
     * during simulator configuration using Python functions.
     * 4) If the host cannot open the file, the open attempt failed in "3)".
     * Return the host's error code back through the system call to the
     * simulated process. If running a debug trace, also notify the user that
     * the open call failed.
     *
     * Any success will set sim_fd to something other than -1 and skip the
     * next conditions effectively bypassing them.
     */
    int sim_fd = -1;
    std::string used_path;
    std::vector<std::string> special_paths =
            { "/proc/meminfo/", "/system/", "/platform/", "/etc/passwd" };
    for (auto entry : special_paths) {
        if (startswith(path, entry)) {
            sim_fd = OS::openSpecialFile(abs_path, p, tc);
            used_path = abs_path;
        }
    }
    if (sim_fd == -1) {
        sim_fd = open(redir_path.c_str(), host_flags, mode);
        used_path = redir_path;
    }
    if (sim_fd == -1) {
        int local = -errno;
        DPRINTF_SYSCALL(Verbose, "open%s: failed -> path:%s "
                        "(inferred from:%s)\n", isopenat ? "at" : "",
                        used_path.c_str(), path.c_str());
        return local;
    }

    /**
     * The file was opened successfully and needs to be recorded in the
     * process' file descriptor array so that it can be retrieved later.
     * The target file descriptor that is chosen will be the lowest unused
     * file descriptor.
     * Return the indirect target file descriptor back to the simulated
     * process to act as a handle for the opened file.
     */
    auto ffdp = std::make_shared<FileFDEntry>(sim_fd, host_flags, path, 0);
    int tgt_fd = p->fds->allocFD(ffdp);
    DPRINTF_SYSCALL(Verbose, "open%s: sim_fd[%d], target_fd[%d] -> path:%s\n"
                    "(inferred from:%s)\n", isopenat ? "at" : "",
                    sim_fd, tgt_fd, used_path.c_str(), path.c_str());
    return tgt_fd;
}

/// Target open() handler.
template <class OS>
SyscallReturn
openFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    return openImpl<OS>(desc, callnum, tc, false);
}

/// Target openat() handler.
template <class OS>
SyscallReturn
openatFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    return openImpl<OS>(desc, callnum, tc, true);
}

/// Target unlinkat() handler.
template <class OS>
SyscallReturn
unlinkatFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto process = tc->getProcessPtr();
    int dirfd = process->getSyscallArg(tc, index);
    if (dirfd != OS::TGT_AT_FDCWD)
        warn("unlinkat: first argument not AT_FDCWD; unlikely to work");

    return unlinkHelper(desc, callnum, tc, 1);
}

/// Target facessat() handler
template <class OS>
SyscallReturn
faccessatFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto process = tc->getProcessPtr();
    int dirfd = process->getSyscallArg(tc, index);
    if (dirfd != OS::TGT_AT_FDCWD)
        warn("faccessat: first argument not AT_FDCWD; unlikely to work");
    return accessImpl(desc, callnum, tc, 1);
}

/// Target readlinkat() handler
template <class OS>
SyscallReturn
readlinkatFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto process = tc->getProcessPtr();
    int dirfd = process->getSyscallArg(tc, index);
    if (dirfd != OS::TGT_AT_FDCWD)
        warn("openat: first argument not AT_FDCWD; unlikely to work");
    return readlinkImpl(desc, callnum, tc, 1);
}

/// Target renameat() handler.
template <class OS>
SyscallReturn
renameatFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto process = tc->getProcessPtr();

    int olddirfd = process->getSyscallArg(tc, index);
    if (olddirfd != OS::TGT_AT_FDCWD)
        warn("renameat: first argument not AT_FDCWD; unlikely to work");

    std::string old_name;

    if (!tc->getVirtProxy().tryReadString(old_name,
                                         process->getSyscallArg(tc, index)))
        return -EFAULT;

    int newdirfd = process->getSyscallArg(tc, index);
    if (newdirfd != OS::TGT_AT_FDCWD)
        warn("renameat: third argument not AT_FDCWD; unlikely to work");

    std::string new_name;

    if (!tc->getVirtProxy().tryReadString(new_name,
                                         process->getSyscallArg(tc, index)))
        return -EFAULT;

    // Adjust path for cwd and redirection
    old_name = process->checkPathRedirect(old_name);
    new_name = process->checkPathRedirect(new_name);

    int result = rename(old_name.c_str(), new_name.c_str());
    return (result == -1) ? -errno : result;
}

/// Target sysinfo() handler.
template <class OS>
SyscallReturn
sysinfoFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto process = tc->getProcessPtr();

    TypedBufferArg<typename OS::tgt_sysinfo>
        sysinfo(process->getSyscallArg(tc, index));

    sysinfo->uptime = seconds_since_epoch;
    sysinfo->totalram = process->system->memSize();
    sysinfo->mem_unit = 1;

    sysinfo.copyOut(tc->getVirtProxy());

    return 0;
}

/// Target chmod() handler.
template <class OS>
SyscallReturn
chmodFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    std::string path;
    auto process = tc->getProcessPtr();

    int index = 0;
    if (!tc->getVirtProxy().tryReadString(path,
                process->getSyscallArg(tc, index))) {
        return -EFAULT;
    }

    uint32_t mode = process->getSyscallArg(tc, index);
    mode_t hostMode = 0;

    // XXX translate mode flags via OS::something???
    hostMode = mode;

    // Adjust path for cwd and redirection
    path = process->checkPathRedirect(path);

    // do the chmod
    int result = chmod(path.c_str(), hostMode);
    if (result < 0)
        return -errno;

    return 0;
}

template <class OS>
SyscallReturn
pollFunc(SyscallDesc *desc, int num, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    Addr fdsPtr = p->getSyscallArg(tc, index);
    int nfds = p->getSyscallArg(tc, index);
    int tmout = p->getSyscallArg(tc, index);

    BufferArg fdsBuf(fdsPtr, sizeof(struct pollfd) * nfds);
    fdsBuf.copyIn(tc->getVirtProxy());

    /**
     * Record the target file descriptors in a local variable. We need to
     * replace them with host file descriptors but we need a temporary copy
     * for later. Afterwards, replace each target file descriptor in the
     * poll_fd array with its host_fd.
     */
    int temp_tgt_fds[nfds];
    for (index = 0; index < nfds; index++) {
        temp_tgt_fds[index] = ((struct pollfd *)fdsBuf.bufferPtr())[index].fd;
        auto tgt_fd = temp_tgt_fds[index];
        auto hbfdp = std::dynamic_pointer_cast<HBFDEntry>((*p->fds)[tgt_fd]);
        if (!hbfdp)
            return -EBADF;
        auto host_fd = hbfdp->getSimFD();
        ((struct pollfd *)fdsBuf.bufferPtr())[index].fd = host_fd;
    }

    /**
     * We cannot allow an infinite poll to occur or it will inevitably cause
     * a deadlock in the gem5 simulator with clone. We must pass in tmout with
     * a non-negative value, however it also makes no sense to poll on the
     * underlying host for any other time than tmout a zero timeout.
     */
    int status;
    if (tmout < 0) {
        status = poll((struct pollfd *)fdsBuf.bufferPtr(), nfds, 0);
        if (status == 0) {
            /**
             * If blocking indefinitely, check the signal list to see if a
             * signal would break the poll out of the retry cycle and try
             * to return the signal interrupt instead.
             */
            System *sysh = tc->getSystemPtr();
            std::list<BasicSignal>::iterator it;
            for (it=sysh->signalList.begin(); it!=sysh->signalList.end(); it++)
                if (it->receiver == p)
                    return -EINTR;
            return SyscallReturn::retry();
        }
    } else
        status = poll((struct pollfd *)fdsBuf.bufferPtr(), nfds, 0);

    if (status == -1)
        return -errno;

    /**
     * Replace each host_fd in the returned poll_fd array with its original
     * target file descriptor.
     */
    for (index = 0; index < nfds; index++) {
        auto tgt_fd = temp_tgt_fds[index];
        ((struct pollfd *)fdsBuf.bufferPtr())[index].fd = tgt_fd;
    }

    /**
     * Copy out the pollfd struct because the host may have updated fields
     * in the structure.
     */
    fdsBuf.copyOut(tc->getVirtProxy());

    return status;
}

/// Target fchmod() handler.
template <class OS>
SyscallReturn
fchmodFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    int tgt_fd = p->getSyscallArg(tc, index);
    uint32_t mode = p->getSyscallArg(tc, index);

    auto ffdp = std::dynamic_pointer_cast<FileFDEntry>((*p->fds)[tgt_fd]);
    if (!ffdp)
        return -EBADF;
    int sim_fd = ffdp->getSimFD();

    mode_t hostMode = mode;

    int result = fchmod(sim_fd, hostMode);

    return (result < 0) ? -errno : 0;
}

/// Target mremap() handler.
template <class OS>
SyscallReturn
mremapFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto process = tc->getProcessPtr();
    Addr start = process->getSyscallArg(tc, index);
    uint64_t old_length = process->getSyscallArg(tc, index);
    uint64_t new_length = process->getSyscallArg(tc, index);
    uint64_t flags = process->getSyscallArg(tc, index);
    uint64_t provided_address = 0;
    bool use_provided_address = flags & OS::TGT_MREMAP_FIXED;

    if (use_provided_address)
        provided_address = process->getSyscallArg(tc, index);

    if ((start % TheISA::PageBytes != 0) ||
        (provided_address % TheISA::PageBytes != 0)) {
        warn("mremap failing: arguments not page aligned");
        return -EINVAL;
    }

    new_length = roundUp(new_length, TheISA::PageBytes);

    if (new_length > old_length) {
        std::shared_ptr<MemState> mem_state = process->memState;
        Addr mmap_end = mem_state->getMmapEnd();

        if ((start + old_length) == mmap_end &&
            (!use_provided_address || provided_address == start)) {
            // This case cannot occur when growing downward, as
            // start is greater than or equal to mmap_end.
            uint64_t diff = new_length - old_length;
            process->allocateMem(mmap_end, diff);
            mem_state->setMmapEnd(mmap_end + diff);
            return start;
        } else {
            if (!use_provided_address && !(flags & OS::TGT_MREMAP_MAYMOVE)) {
                warn("can't remap here and MREMAP_MAYMOVE flag not set\n");
                return -ENOMEM;
            } else {
                uint64_t new_start = provided_address;
                if (!use_provided_address) {
                    new_start = process->mmapGrowsDown() ?
                                mmap_end - new_length : mmap_end;
                    mmap_end = process->mmapGrowsDown() ?
                               new_start : mmap_end + new_length;
                    mem_state->setMmapEnd(mmap_end);
                }

                process->pTable->remap(start, old_length, new_start);
                warn("mremapping to new vaddr %08p-%08p, adding %d\n",
                     new_start, new_start + new_length,
                     new_length - old_length);
                // add on the remaining unallocated pages
                process->allocateMem(new_start + old_length,
                                     new_length - old_length,
                                     use_provided_address /* clobber */);
                if (use_provided_address &&
                    ((new_start + new_length > mem_state->getMmapEnd() &&
                      !process->mmapGrowsDown()) ||
                    (new_start < mem_state->getMmapEnd() &&
                      process->mmapGrowsDown()))) {
                    // something fishy going on here, at least notify the user
                    // @todo: increase mmap_end?
                    warn("mmap region limit exceeded with MREMAP_FIXED\n");
                }
                warn("returning %08p as start\n", new_start);
                return new_start;
            }
        }
    } else {
        if (use_provided_address && provided_address != start)
            process->pTable->remap(start, new_length, provided_address);
        process->pTable->unmap(start + new_length, old_length - new_length);
        return use_provided_address ? provided_address : start;
    }
}

/// Target stat() handler.
template <class OS>
SyscallReturn
statFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    std::string path;
    auto process = tc->getProcessPtr();

    int index = 0;
    if (!tc->getVirtProxy().tryReadString(path,
                process->getSyscallArg(tc, index))) {
        return -EFAULT;
    }
    Addr bufPtr = process->getSyscallArg(tc, index);

    // Adjust path for cwd and redirection
    path = process->checkPathRedirect(path);

    struct stat hostBuf;
    int result = stat(path.c_str(), &hostBuf);

    if (result < 0)
        return -errno;

    copyOutStatBuf<OS>(tc->getVirtProxy(), bufPtr, &hostBuf);

    return 0;
}


/// Target stat64() handler.
template <class OS>
SyscallReturn
stat64Func(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    std::string path;
    auto process = tc->getProcessPtr();

    int index = 0;
    if (!tc->getVirtProxy().tryReadString(path,
                process->getSyscallArg(tc, index)))
        return -EFAULT;
    Addr bufPtr = process->getSyscallArg(tc, index);

    // Adjust path for cwd and redirection
    path = process->checkPathRedirect(path);

#if NO_STAT64
    struct stat  hostBuf;
    int result = stat(path.c_str(), &hostBuf);
#else
    struct stat64 hostBuf;
    int result = stat64(path.c_str(), &hostBuf);
#endif

    if (result < 0)
        return -errno;

    copyOutStat64Buf<OS>(tc->getVirtProxy(), bufPtr, &hostBuf);

    return 0;
}


/// Target fstatat64() handler.
template <class OS>
SyscallReturn
fstatat64Func(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto process = tc->getProcessPtr();
    int dirfd = process->getSyscallArg(tc, index);
    if (dirfd != OS::TGT_AT_FDCWD)
        warn("fstatat64: first argument not AT_FDCWD; unlikely to work");

    std::string path;
    if (!tc->getVirtProxy().tryReadString(path,
                process->getSyscallArg(tc, index)))
        return -EFAULT;
    Addr bufPtr = process->getSyscallArg(tc, index);

    // Adjust path for cwd and redirection
    path = process->checkPathRedirect(path);

#if NO_STAT64
    struct stat  hostBuf;
    int result = stat(path.c_str(), &hostBuf);
#else
    struct stat64 hostBuf;
    int result = stat64(path.c_str(), &hostBuf);
#endif

    if (result < 0)
        return -errno;

    copyOutStat64Buf<OS>(tc->getVirtProxy(), bufPtr, &hostBuf);

    return 0;
}


/// Target fstat64() handler.
template <class OS>
SyscallReturn
fstat64Func(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    int tgt_fd = p->getSyscallArg(tc, index);
    Addr bufPtr = p->getSyscallArg(tc, index);

    auto ffdp = std::dynamic_pointer_cast<HBFDEntry>((*p->fds)[tgt_fd]);
    if (!ffdp)
        return -EBADF;
    int sim_fd = ffdp->getSimFD();

#if NO_STAT64
    struct stat  hostBuf;
    int result = fstat(sim_fd, &hostBuf);
#else
    struct stat64  hostBuf;
    int result = fstat64(sim_fd, &hostBuf);
#endif

    if (result < 0)
        return -errno;

    copyOutStat64Buf<OS>(tc->getVirtProxy(), bufPtr, &hostBuf, (sim_fd == 1));

    return 0;
}


/// Target lstat() handler.
template <class OS>
SyscallReturn
lstatFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    std::string path;
    auto process = tc->getProcessPtr();

    int index = 0;
    if (!tc->getVirtProxy().tryReadString(path,
                process->getSyscallArg(tc, index))) {
        return -EFAULT;
    }
    Addr bufPtr = process->getSyscallArg(tc, index);

    // Adjust path for cwd and redirection
    path = process->checkPathRedirect(path);

    struct stat hostBuf;
    int result = lstat(path.c_str(), &hostBuf);

    if (result < 0)
        return -errno;

    copyOutStatBuf<OS>(tc->getVirtProxy(), bufPtr, &hostBuf);

    return 0;
}

/// Target lstat64() handler.
template <class OS>
SyscallReturn
lstat64Func(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    std::string path;
    auto process = tc->getProcessPtr();

    int index = 0;
    if (!tc->getVirtProxy().tryReadString(path,
                process->getSyscallArg(tc, index))) {
        return -EFAULT;
    }
    Addr bufPtr = process->getSyscallArg(tc, index);

    // Adjust path for cwd and redirection
    path = process->checkPathRedirect(path);

#if NO_STAT64
    struct stat hostBuf;
    int result = lstat(path.c_str(), &hostBuf);
#else
    struct stat64 hostBuf;
    int result = lstat64(path.c_str(), &hostBuf);
#endif

    if (result < 0)
        return -errno;

    copyOutStat64Buf<OS>(tc->getVirtProxy(), bufPtr, &hostBuf);

    return 0;
}

/// Target fstat() handler.
template <class OS>
SyscallReturn
fstatFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    int tgt_fd = p->getSyscallArg(tc, index);
    Addr bufPtr = p->getSyscallArg(tc, index);

    DPRINTF_SYSCALL(Verbose, "fstat(%d, ...)\n", tgt_fd);

    auto ffdp = std::dynamic_pointer_cast<FileFDEntry>((*p->fds)[tgt_fd]);
    if (!ffdp)
        return -EBADF;
    int sim_fd = ffdp->getSimFD();

    struct stat hostBuf;
    int result = fstat(sim_fd, &hostBuf);

    if (result < 0)
        return -errno;

    copyOutStatBuf<OS>(tc->getVirtProxy(), bufPtr, &hostBuf, (sim_fd == 1));

    return 0;
}

/// Target statfs() handler.
template <class OS>
SyscallReturn
statfsFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
#if defined(__linux__)
    std::string path;
    auto process = tc->getProcessPtr();

    int index = 0;
    if (!tc->getVirtProxy().tryReadString(path,
                process->getSyscallArg(tc, index))) {
        return -EFAULT;
    }
    Addr bufPtr = process->getSyscallArg(tc, index);

    // Adjust path for cwd and redirection
    path = process->checkPathRedirect(path);

    struct statfs hostBuf;
    int result = statfs(path.c_str(), &hostBuf);

    if (result < 0)
        return -errno;

    copyOutStatfsBuf<OS>(tc->getVirtProxy(), bufPtr, &hostBuf);
    return 0;
#else
    warnUnsupportedOS("statfs");
    return -1;
#endif
}

template <class OS>
SyscallReturn
cloneFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;

    auto p = tc->getProcessPtr();
    RegVal flags = p->getSyscallArg(tc, index);
    RegVal newStack = p->getSyscallArg(tc, index);
    Addr ptidPtr = p->getSyscallArg(tc, index);

#if THE_ISA == RISCV_ISA or THE_ISA == ARM_ISA
    /**
     * Linux sets CLONE_BACKWARDS flag for RISC-V and Arm.
     * The flag defines the list of clone() arguments in the following
     * order: flags -> newStack -> ptidPtr -> tlsPtr -> ctidPtr
     */
    Addr tlsPtr = p->getSyscallArg(tc, index);
    Addr ctidPtr = p->getSyscallArg(tc, index);
#else
    Addr ctidPtr = p->getSyscallArg(tc, index);
    Addr tlsPtr = p->getSyscallArg(tc, index);
#endif

    if (((flags & OS::TGT_CLONE_SIGHAND)&& !(flags & OS::TGT_CLONE_VM)) ||
        ((flags & OS::TGT_CLONE_THREAD) && !(flags & OS::TGT_CLONE_SIGHAND)) ||
        ((flags & OS::TGT_CLONE_FS)     &&  (flags & OS::TGT_CLONE_NEWNS)) ||
        ((flags & OS::TGT_CLONE_NEWIPC) &&  (flags & OS::TGT_CLONE_SYSVSEM)) ||
        ((flags & OS::TGT_CLONE_NEWPID) &&  (flags & OS::TGT_CLONE_THREAD)) ||
        ((flags & OS::TGT_CLONE_VM)     && !(newStack)))
        return -EINVAL;

    ThreadContext *ctc;
    if (!(ctc = p->findFreeContext())) {
        DPRINTF_SYSCALL(Verbose, "clone: no spare thread context in system"
                        "[cpu %d, thread %d]", tc->cpuId(), tc->threadId());
        return -EAGAIN;
    }

    /**
     * Note that ProcessParams is generated by swig and there are no other
     * examples of how to create anything but this default constructor. The
     * fields are manually initialized instead of passing parameters to the
     * constructor.
     */
    ProcessParams *pp = new ProcessParams();
    pp->executable.assign(*(new std::string(p->progName())));
    pp->cmd.push_back(*(new std::string(p->progName())));
    pp->system = p->system;
    pp->cwd.assign(p->tgtCwd);
    pp->input.assign("stdin");
    pp->output.assign("stdout");
    pp->errout.assign("stderr");
    pp->uid = p->uid();
    pp->euid = p->euid();
    pp->gid = p->gid();
    pp->egid = p->egid();

    /* Find the first free PID that's less than the maximum */
    std::set<int> const& pids = p->system->PIDs;
    int temp_pid = *pids.begin();
    do {
        temp_pid++;
    } while (pids.find(temp_pid) != pids.end());
    if (temp_pid >= System::maxPID)
        fatal("temp_pid is too large: %d", temp_pid);

    pp->pid = temp_pid;
    pp->ppid = (flags & OS::TGT_CLONE_THREAD) ? p->ppid() : p->pid();
    pp->useArchPT = p->useArchPT;
    pp->kvmInSE = p->kvmInSE;
    Process *cp = pp->create();
    // TODO: there is no way to know when the Process SimObject is done with
    // the params pointer. Both the params pointer (pp) and the process
    // pointer (cp) are normally managed in python and are never cleaned up.

    Process *owner = ctc->getProcessPtr();
    ctc->setProcessPtr(cp);
    cp->assignThreadContext(ctc->contextId());
    owner->revokeThreadContext(ctc->contextId());

    if (flags & OS::TGT_CLONE_PARENT_SETTID) {
        BufferArg ptidBuf(ptidPtr, sizeof(long));
        long *ptid = (long *)ptidBuf.bufferPtr();
        *ptid = cp->pid();
        ptidBuf.copyOut(tc->getVirtProxy());
    }

    if (flags & OS::TGT_CLONE_THREAD) {
        cp->pTable->shared = true;
        cp->useForClone = true;
    }
    cp->initState();
    p->clone(tc, ctc, cp, flags);

    if (flags & OS::TGT_CLONE_THREAD) {
        delete cp->sigchld;
        cp->sigchld = p->sigchld;
    } else if (flags & OS::TGT_SIGCHLD) {
        *cp->sigchld = true;
    }

    if (flags & OS::TGT_CLONE_CHILD_SETTID) {
        BufferArg ctidBuf(ctidPtr, sizeof(long));
        long *ctid = (long *)ctidBuf.bufferPtr();
        *ctid = cp->pid();
        ctidBuf.copyOut(ctc->getVirtProxy());
    }

    if (flags & OS::TGT_CLONE_CHILD_CLEARTID)
        cp->childClearTID = (uint64_t)ctidPtr;

    ctc->clearArchRegs();

    OS::archClone(flags, p, cp, tc, ctc, newStack, tlsPtr);

    cp->setSyscallReturn(ctc, 0);

#if THE_ISA == ALPHA_ISA
    ctc->setIntReg(TheISA::SyscallSuccessReg, 0);
#elif THE_ISA == SPARC_ISA
    tc->setIntReg(TheISA::SyscallPseudoReturnReg, 0);
    ctc->setIntReg(TheISA::SyscallPseudoReturnReg, 1);
#endif

    if (p->kvmInSE) {
#if THE_ISA == X86_ISA
        ctc->pcState(tc->readIntReg(TheISA::INTREG_RCX));
#else
        panic("KVM CPU model is not supported for this ISA");
#endif
    } else {
        TheISA::PCState cpc = tc->pcState();
        cpc.advance();
        ctc->pcState(cpc);
    }
    ctc->activate();

    return cp->pid();
}

/// Target fstatfs() handler.
template <class OS>
SyscallReturn
fstatfsFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    int tgt_fd = p->getSyscallArg(tc, index);
    Addr bufPtr = p->getSyscallArg(tc, index);

    auto ffdp = std::dynamic_pointer_cast<FileFDEntry>((*p->fds)[tgt_fd]);
    if (!ffdp)
        return -EBADF;
    int sim_fd = ffdp->getSimFD();

    struct statfs hostBuf;
    int result = fstatfs(sim_fd, &hostBuf);

    if (result < 0)
        return -errno;

    copyOutStatfsBuf<OS>(tc->getVirtProxy(), bufPtr, &hostBuf);

    return 0;
}

/// Target readv() handler.
template <class OS>
SyscallReturn
readvFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    int tgt_fd = p->getSyscallArg(tc, index);

    auto ffdp = std::dynamic_pointer_cast<FileFDEntry>((*p->fds)[tgt_fd]);
    if (!ffdp)
        return -EBADF;
    int sim_fd = ffdp->getSimFD();

    PortProxy &prox = tc->getVirtProxy();
    uint64_t tiov_base = p->getSyscallArg(tc, index);
    size_t count = p->getSyscallArg(tc, index);
    typename OS::tgt_iovec tiov[count];
    struct iovec hiov[count];
    for (size_t i = 0; i < count; ++i) {
        prox.readBlob(tiov_base + (i * sizeof(typename OS::tgt_iovec)),
                      &tiov[i], sizeof(typename OS::tgt_iovec));
        hiov[i].iov_len = gtoh(tiov[i].iov_len, OS::byteOrder);
        hiov[i].iov_base = new char [hiov[i].iov_len];
    }

    int result = readv(sim_fd, hiov, count);
    int local_errno = errno;

    for (size_t i = 0; i < count; ++i) {
        if (result != -1) {
            prox.writeBlob(htog(tiov[i].iov_base, OS::byteOrder),
                           hiov[i].iov_base, hiov[i].iov_len);
        }
        delete [] (char *)hiov[i].iov_base;
    }

    return (result == -1) ? -local_errno : result;
}

/// Target writev() handler.
template <class OS>
SyscallReturn
writevFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    int tgt_fd = p->getSyscallArg(tc, index);

    auto hbfdp = std::dynamic_pointer_cast<HBFDEntry>((*p->fds)[tgt_fd]);
    if (!hbfdp)
        return -EBADF;
    int sim_fd = hbfdp->getSimFD();

    PortProxy &prox = tc->getVirtProxy();
    uint64_t tiov_base = p->getSyscallArg(tc, index);
    size_t count = p->getSyscallArg(tc, index);
    struct iovec hiov[count];
    for (size_t i = 0; i < count; ++i) {
        typename OS::tgt_iovec tiov;

        prox.readBlob(tiov_base + i*sizeof(typename OS::tgt_iovec),
                      &tiov, sizeof(typename OS::tgt_iovec));
        hiov[i].iov_len = gtoh(tiov.iov_len, OS::byteOrder);
        hiov[i].iov_base = new char [hiov[i].iov_len];
        prox.readBlob(gtoh(tiov.iov_base, OS::byteOrder), hiov[i].iov_base,
                      hiov[i].iov_len);
    }

    int result = writev(sim_fd, hiov, count);

    for (size_t i = 0; i < count; ++i)
        delete [] (char *)hiov[i].iov_base;

    return (result == -1) ? -errno : result;
}

/// Real mmap handler.
template <class OS>
SyscallReturn
mmapImpl(SyscallDesc *desc, int num, ThreadContext *tc, bool is_mmap2)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    Addr start = p->getSyscallArg(tc, index);
    uint64_t length = p->getSyscallArg(tc, index);
    int prot = p->getSyscallArg(tc, index);
    int tgt_flags = p->getSyscallArg(tc, index);
    int tgt_fd = p->getSyscallArg(tc, index);
    int offset = p->getSyscallArg(tc, index);

    if (is_mmap2)
        offset *= TheISA::PageBytes;

    if (start & (TheISA::PageBytes - 1) ||
        offset & (TheISA::PageBytes - 1) ||
        (tgt_flags & OS::TGT_MAP_PRIVATE &&
         tgt_flags & OS::TGT_MAP_SHARED) ||
        (!(tgt_flags & OS::TGT_MAP_PRIVATE) &&
         !(tgt_flags & OS::TGT_MAP_SHARED)) ||
        !length) {
        return -EINVAL;
    }

    if ((prot & PROT_WRITE) && (tgt_flags & OS::TGT_MAP_SHARED)) {
        // With shared mmaps, there are two cases to consider:
        // 1) anonymous: writes should modify the mapping and this should be
        // visible to observers who share the mapping. Currently, it's
        // difficult to update the shared mapping because there's no
        // structure which maintains information about the which virtual
        // memory areas are shared. If that structure existed, it would be
        // possible to make the translations point to the same frames.
        // 2) file-backed: writes should modify the mapping and the file
        // which is backed by the mapping. The shared mapping problem is the
        // same as what was mentioned about the anonymous mappings. For
        // file-backed mappings, the writes to the file are difficult
        // because it requires syncing what the mapping holds with the file
        // that resides on the host system. So, any write on a real system
        // would cause the change to be propagated to the file mapping at
        // some point in the future (the inode is tracked along with the
        // mapping). This isn't guaranteed to always happen, but it usually
        // works well enough. The guarantee is provided by the msync system
        // call. We could force the change through with shared mappings with
        // a call to msync, but that again would require more information
        // than we currently maintain.
        warn("mmap: writing to shared mmap region is currently "
             "unsupported. The write succeeds on the target, but it "
             "will not be propagated to the host or shared mappings");
    }

    length = roundUp(length, TheISA::PageBytes);

    int sim_fd = -1;
    uint8_t *pmap = nullptr;
    if (!(tgt_flags & OS::TGT_MAP_ANONYMOUS)) {
        std::shared_ptr<FDEntry> fdep = (*p->fds)[tgt_fd];

        auto dfdp = std::dynamic_pointer_cast<DeviceFDEntry>(fdep);
        if (dfdp) {
            EmulatedDriver *emul_driver = dfdp->getDriver();
            return emul_driver->mmap(tc, start, length, prot, tgt_flags,
                                     tgt_fd, offset);
        }

        auto ffdp = std::dynamic_pointer_cast<FileFDEntry>(fdep);
        if (!ffdp)
            return -EBADF;
        sim_fd = ffdp->getSimFD();

        pmap = (decltype(pmap))mmap(nullptr, length, PROT_READ, MAP_PRIVATE,
                                    sim_fd, offset);

        if (pmap == (decltype(pmap))-1) {
            warn("mmap: failed to map file into host address space");
            return -errno;
        }
    }

    // Extend global mmap region if necessary. Note that we ignore the
    // start address unless MAP_FIXED is specified.
    if (!(tgt_flags & OS::TGT_MAP_FIXED)) {
        std::shared_ptr<MemState> mem_state = p->memState;
        Addr mmap_end = mem_state->getMmapEnd();

        start = p->mmapGrowsDown() ? mmap_end - length : mmap_end;
        mmap_end = p->mmapGrowsDown() ? start : mmap_end + length;

        mem_state->setMmapEnd(mmap_end);
    }

    DPRINTF_SYSCALL(Verbose, " mmap range is 0x%x - 0x%x\n",
                    start, start + length - 1);

    // We only allow mappings to overwrite existing mappings if
    // TGT_MAP_FIXED is set. Otherwise it shouldn't be a problem
    // because we ignore the start hint if TGT_MAP_FIXED is not set.
    int clobber = tgt_flags & OS::TGT_MAP_FIXED;
    if (clobber) {
        for (auto tc : p->system->threadContexts) {
            // If we might be overwriting old mappings, we need to
            // invalidate potentially stale mappings out of the TLBs.
            tc->getDTBPtr()->flushAll();
            tc->getITBPtr()->flushAll();
        }
    }

    // Allocate physical memory and map it in. If the page table is already
    // mapped and clobber is not set, the simulator will issue throw a
    // fatal and bail out of the simulation.
    p->allocateMem(start, length, clobber);

    // Transfer content into target address space.
    PortProxy &tp = tc->getVirtProxy();
    if (tgt_flags & OS::TGT_MAP_ANONYMOUS) {
        // In general, we should zero the mapped area for anonymous mappings,
        // with something like:
        //     tp.memsetBlob(start, 0, length);
        // However, given that we don't support sparse mappings, and
        // some applications can map a couple of gigabytes of space
        // (intending sparse usage), that can get painfully expensive.
        // Fortunately, since we don't properly implement munmap either,
        // there's no danger of remapping used memory, so for now all
        // newly mapped memory should already be zeroed so we can skip it.
    } else {
        // It is possible to mmap an area larger than a file, however
        // accessing unmapped portions the system triggers a "Bus error"
        // on the host. We must know when to stop copying the file from
        // the host into the target address space.
        struct stat file_stat;
        if (fstat(sim_fd, &file_stat) > 0)
            fatal("mmap: cannot stat file");

        // Copy the portion of the file that is resident. This requires
        // checking both the mmap size and the filesize that we are
        // trying to mmap into this space; the mmap size also depends
        // on the specified offset into the file.
        uint64_t size = std::min((uint64_t)file_stat.st_size - offset,
                                 length);
        tp.writeBlob(start, pmap, size);

        // Cleanup the mmap region before exiting this function.
        munmap(pmap, length);

        // Maintain the symbol table for dynamic executables.
        // The loader will call mmap to map the images into its address
        // space and we intercept that here. We can verify that we are
        // executing inside the loader by checking the program counter value.
        // XXX: with multiprogrammed workloads or multi-node configurations,
        // this will not work since there is a single global symbol table.
        if (p->interpImage.contains(tc->pcState().instAddr())) {
            std::shared_ptr<FDEntry> fdep = (*p->fds)[tgt_fd];
            auto ffdp = std::dynamic_pointer_cast<FileFDEntry>(fdep);
            auto process = tc->getProcessPtr();
            ObjectFile *lib = createObjectFile(
                process->checkPathRedirect(
                    ffdp->getFileName()));

            if (lib) {
                lib->loadAllSymbols(debugSymbolTable,
                                    lib->buildImage().minAddr(), start);
            }
        }

        // Note that we do not zero out the remainder of the mapping. This
        // is done by a real system, but it probably will not affect
        // execution (hopefully).
    }

    return start;
}

template <class OS>
SyscallReturn
pwrite64Func(SyscallDesc *desc, int num, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    int tgt_fd = p->getSyscallArg(tc, index);
    Addr bufPtr = p->getSyscallArg(tc, index);
    int nbytes = p->getSyscallArg(tc, index);
    int offset = p->getSyscallArg(tc, index);

    auto ffdp = std::dynamic_pointer_cast<FileFDEntry>((*p->fds)[tgt_fd]);
    if (!ffdp)
        return -EBADF;
    int sim_fd = ffdp->getSimFD();

    BufferArg bufArg(bufPtr, nbytes);
    bufArg.copyIn(tc->getVirtProxy());

    int bytes_written = pwrite(sim_fd, bufArg.bufferPtr(), nbytes, offset);

    return (bytes_written == -1) ? -errno : bytes_written;
}

/// Target mmap() handler.
template <class OS>
SyscallReturn
mmapFunc(SyscallDesc *desc, int num, ThreadContext *tc)
{
    return mmapImpl<OS>(desc, num, tc, false);
}

/// Target mmap2() handler.
template <class OS>
SyscallReturn
mmap2Func(SyscallDesc *desc, int num, ThreadContext *tc)
{
    return mmapImpl<OS>(desc, num, tc, true);
}

/// Target getrlimit() handler.
template <class OS>
SyscallReturn
getrlimitFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto process = tc->getProcessPtr();
    unsigned resource = process->getSyscallArg(tc, index);
    TypedBufferArg<typename OS::rlimit> rlp(process->getSyscallArg(tc, index));

    const ByteOrder bo = OS::byteOrder;
    switch (resource) {
      case OS::TGT_RLIMIT_STACK:
        // max stack size in bytes: make up a number (8MB for now)
        rlp->rlim_cur = rlp->rlim_max = 8 * 1024 * 1024;
        rlp->rlim_cur = htog(rlp->rlim_cur, bo);
        rlp->rlim_max = htog(rlp->rlim_max, bo);
        break;

      case OS::TGT_RLIMIT_DATA:
        // max data segment size in bytes: make up a number
        rlp->rlim_cur = rlp->rlim_max = 256 * 1024 * 1024;
        rlp->rlim_cur = htog(rlp->rlim_cur, bo);
        rlp->rlim_max = htog(rlp->rlim_max, bo);
        break;

      case OS::TGT_RLIMIT_NPROC:
        rlp->rlim_cur = rlp->rlim_max = tc->getSystemPtr()->numContexts();
        rlp->rlim_cur = htog(rlp->rlim_cur, bo);
        rlp->rlim_max = htog(rlp->rlim_max, bo);
        break;

      default:
        warn("getrlimit: unimplemented resource %d", resource);
        return -EINVAL;
        break;
    }

    rlp.copyOut(tc->getVirtProxy());
    return 0;
}

template <class OS>
SyscallReturn
prlimitFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto process = tc->getProcessPtr();
    if (process->getSyscallArg(tc, index) != 0)
    {
        warn("prlimit: ignoring rlimits for nonzero pid");
        return -EPERM;
    }
    int resource = process->getSyscallArg(tc, index);
    Addr n = process->getSyscallArg(tc, index);
    if (n != 0)
        warn("prlimit: ignoring new rlimit");
    Addr o = process->getSyscallArg(tc, index);
    if (o != 0) {

        const ByteOrder bo = OS::byteOrder;
        TypedBufferArg<typename OS::rlimit> rlp(o);
        switch (resource) {
          case OS::TGT_RLIMIT_STACK:
            // max stack size in bytes: make up a number (8MB for now)
            rlp->rlim_cur = rlp->rlim_max = 8 * 1024 * 1024;
            rlp->rlim_cur = htog(rlp->rlim_cur, bo);
            rlp->rlim_max = htog(rlp->rlim_max, bo);
            break;
          case OS::TGT_RLIMIT_DATA:
            // max data segment size in bytes: make up a number
            rlp->rlim_cur = rlp->rlim_max = 256*1024*1024;
            rlp->rlim_cur = htog(rlp->rlim_cur, bo);
            rlp->rlim_max = htog(rlp->rlim_max, bo);
            break;
          default:
            warn("prlimit: unimplemented resource %d", resource);
            return -EINVAL;
            break;
        }
        rlp.copyOut(tc->getVirtProxy());
    }
    return 0;
}

/// Target clock_gettime() function.
template <class OS>
SyscallReturn
clock_gettimeFunc(SyscallDesc *desc, int num, ThreadContext *tc)
{
    int index = 1;
    auto p = tc->getProcessPtr();
    //int clk_id = p->getSyscallArg(tc, index);
    TypedBufferArg<typename OS::timespec> tp(p->getSyscallArg(tc, index));

    getElapsedTimeNano(tp->tv_sec, tp->tv_nsec);
    tp->tv_sec += seconds_since_epoch;
    tp->tv_sec = htog(tp->tv_sec, OS::byteOrder);
    tp->tv_nsec = htog(tp->tv_nsec, OS::byteOrder);

    tp.copyOut(tc->getVirtProxy());

    return 0;
}

/// Target clock_getres() function.
template <class OS>
SyscallReturn
clock_getresFunc(SyscallDesc *desc, int num, ThreadContext *tc)
{
    int index = 1;
    auto p = tc->getProcessPtr();
    TypedBufferArg<typename OS::timespec> tp(p->getSyscallArg(tc, index));

    // Set resolution at ns, which is what clock_gettime() returns
    tp->tv_sec = 0;
    tp->tv_nsec = 1;

    tp.copyOut(tc->getVirtProxy());

    return 0;
}

/// Target gettimeofday() handler.
template <class OS>
SyscallReturn
gettimeofdayFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto process = tc->getProcessPtr();
    TypedBufferArg<typename OS::timeval> tp(process->getSyscallArg(tc, index));

    getElapsedTimeMicro(tp->tv_sec, tp->tv_usec);
    tp->tv_sec += seconds_since_epoch;
    tp->tv_sec = htog(tp->tv_sec, OS::byteOrder);
    tp->tv_usec = htog(tp->tv_usec, OS::byteOrder);

    tp.copyOut(tc->getVirtProxy());

    return 0;
}


/// Target utimes() handler.
template <class OS>
SyscallReturn
utimesFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    std::string path;
    auto process = tc->getProcessPtr();

    int index = 0;
    if (!tc->getVirtProxy().tryReadString(path,
                process->getSyscallArg(tc, index))) {
        return -EFAULT;
    }

    TypedBufferArg<typename OS::timeval [2]>
        tp(process->getSyscallArg(tc, index));
    tp.copyIn(tc->getVirtProxy());

    struct timeval hostTimeval[2];
    for (int i = 0; i < 2; ++i) {
        hostTimeval[i].tv_sec = gtoh((*tp)[i].tv_sec, OS::byteOrder);
        hostTimeval[i].tv_usec = gtoh((*tp)[i].tv_usec, OS::byteOrder);
    }

    // Adjust path for cwd and redirection
    path = process->checkPathRedirect(path);

    int result = utimes(path.c_str(), hostTimeval);

    if (result < 0)
        return -errno;

    return 0;
}

template <class OS>
SyscallReturn
execveFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    auto p = tc->getProcessPtr();

    int index = 0;
    std::string path;
    PortProxy & mem_proxy = tc->getVirtProxy();
    if (!mem_proxy.tryReadString(path, p->getSyscallArg(tc, index)))
        return -EFAULT;

    if (access(path.c_str(), F_OK) == -1)
        return -EACCES;

    auto read_in = [](std::vector<std::string> &vect,
                      PortProxy &mem_proxy, Addr mem_loc)
    {
        for (int inc = 0; ; inc++) {
            BufferArg b((mem_loc + sizeof(Addr) * inc), sizeof(Addr));
            b.copyIn(mem_proxy);

            if (!*(Addr*)b.bufferPtr())
                break;

            vect.push_back(std::string());
            mem_proxy.tryReadString(vect[inc], *(Addr*)b.bufferPtr());
        }
    };

    /**
     * Note that ProcessParams is generated by swig and there are no other
     * examples of how to create anything but this default constructor. The
     * fields are manually initialized instead of passing parameters to the
     * constructor.
     */
    ProcessParams *pp = new ProcessParams();
    pp->executable = path;
    Addr argv_mem_loc = p->getSyscallArg(tc, index);
    read_in(pp->cmd, mem_proxy, argv_mem_loc);
    Addr envp_mem_loc = p->getSyscallArg(tc, index);
    read_in(pp->env, mem_proxy, envp_mem_loc);
    pp->uid = p->uid();
    pp->egid = p->egid();
    pp->euid = p->euid();
    pp->gid = p->gid();
    pp->ppid = p->ppid();
    pp->pid = p->pid();
    pp->input.assign("cin");
    pp->output.assign("cout");
    pp->errout.assign("cerr");
    pp->cwd.assign(p->tgtCwd);
    pp->system = p->system;
    /**
     * Prevent process object creation with identical PIDs (which will trip
     * a fatal check in Process constructor). The execve call is supposed to
     * take over the currently executing process' identity but replace
     * whatever it is doing with a new process image. Instead of hijacking
     * the process object in the simulator, we create a new process object
     * and bind to the previous process' thread below (hijacking the thread).
     */
    p->system->PIDs.erase(p->pid());
    Process *new_p = pp->create();
    delete pp;

    /**
     * Work through the file descriptor array and close any files marked
     * close-on-exec.
     */
    new_p->fds = p->fds;
    for (int i = 0; i < new_p->fds->getSize(); i++) {
        std::shared_ptr<FDEntry> fdep = (*new_p->fds)[i];
        if (fdep && fdep->getCOE())
            new_p->fds->closeFDEntry(i);
    }

    *new_p->sigchld = true;

    delete p;
    tc->clearArchRegs();
    tc->setProcessPtr(new_p);
    new_p->assignThreadContext(tc->contextId());
    new_p->initState();
    tc->activate();
    TheISA::PCState pcState = tc->pcState();
    tc->setNPC(pcState.instAddr());

    return SyscallReturn();
}

/// Target getrusage() function.
template <class OS>
SyscallReturn
getrusageFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto process = tc->getProcessPtr();
    int who = process->getSyscallArg(tc, index); // THREAD, SELF, or CHILDREN
    TypedBufferArg<typename OS::rusage> rup(process->getSyscallArg(tc, index));

    rup->ru_utime.tv_sec = 0;
    rup->ru_utime.tv_usec = 0;
    rup->ru_stime.tv_sec = 0;
    rup->ru_stime.tv_usec = 0;
    rup->ru_maxrss = 0;
    rup->ru_ixrss = 0;
    rup->ru_idrss = 0;
    rup->ru_isrss = 0;
    rup->ru_minflt = 0;
    rup->ru_majflt = 0;
    rup->ru_nswap = 0;
    rup->ru_inblock = 0;
    rup->ru_oublock = 0;
    rup->ru_msgsnd = 0;
    rup->ru_msgrcv = 0;
    rup->ru_nsignals = 0;
    rup->ru_nvcsw = 0;
    rup->ru_nivcsw = 0;

    switch (who) {
      case OS::TGT_RUSAGE_SELF:
        getElapsedTimeMicro(rup->ru_utime.tv_sec, rup->ru_utime.tv_usec);
        rup->ru_utime.tv_sec = htog(rup->ru_utime.tv_sec, OS::byteOrder);
        rup->ru_utime.tv_usec = htog(rup->ru_utime.tv_usec, OS::byteOrder);
        break;

      case OS::TGT_RUSAGE_CHILDREN:
        // do nothing.  We have no child processes, so they take no time.
        break;

      default:
        // don't really handle THREAD or CHILDREN, but just warn and
        // plow ahead
        warn("getrusage() only supports RUSAGE_SELF.  Parameter %d ignored.",
             who);
    }

    rup.copyOut(tc->getVirtProxy());

    return 0;
}

/// Target times() function.
template <class OS>
SyscallReturn
timesFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int index = 0;
    auto process = tc->getProcessPtr();
    TypedBufferArg<typename OS::tms> bufp(process->getSyscallArg(tc, index));

    // Fill in the time structure (in clocks)
    int64_t clocks = curTick() * OS::M5_SC_CLK_TCK / SimClock::Int::s;
    bufp->tms_utime = clocks;
    bufp->tms_stime = 0;
    bufp->tms_cutime = 0;
    bufp->tms_cstime = 0;

    // Convert to host endianness
    bufp->tms_utime = htog(bufp->tms_utime, OS::byteOrder);

    // Write back
    bufp.copyOut(tc->getVirtProxy());

    // Return clock ticks since system boot
    return clocks;
}

/// Target time() function.
template <class OS>
SyscallReturn
timeFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    typename OS::time_t sec, usec;
    getElapsedTimeMicro(sec, usec);
    sec += seconds_since_epoch;

    int index = 0;
    auto process = tc->getProcessPtr();
    Addr taddr = (Addr)process->getSyscallArg(tc, index);
    if (taddr != 0) {
        typename OS::time_t t = sec;
        t = htog(t, OS::byteOrder);
        PortProxy &p = tc->getVirtProxy();
        p.writeBlob(taddr, &t, (int)sizeof(typename OS::time_t));
    }
    return sec;
}

template <class OS>
SyscallReturn
tgkillFunc(SyscallDesc *desc, int num, ThreadContext *tc)
{
    int index = 0;
    auto process = tc->getProcessPtr();
    int tgid = process->getSyscallArg(tc, index);
    int tid = process->getSyscallArg(tc, index);
    int sig = process->getSyscallArg(tc, index);

    /**
     * This system call is intended to allow killing a specific thread
     * within an arbitrary thread group if sanctioned with permission checks.
     * It's usually true that threads share the termination signal as pointed
     * out by the pthread_kill man page and this seems to be the intended
     * usage. Due to this being an emulated environment, assume the following:
     * Threads are allowed to call tgkill because the EUID for all threads
     * should be the same. There is no signal handling mechanism for kernel
     * registration of signal handlers since signals are poorly supported in
     * emulation mode. Since signal handlers cannot be registered, all
     * threads within in a thread group must share the termination signal.
     * We never exhaust PIDs so there's no chance of finding the wrong one
     * due to PID rollover.
     */

    System *sys = tc->getSystemPtr();
    Process *tgt_proc = nullptr;
    for (int i = 0; i < sys->numContexts(); i++) {
        Process *temp = sys->threadContexts[i]->getProcessPtr();
        if (temp->pid() == tid) {
            tgt_proc = temp;
            break;
        }
    }

    if (sig != 0 || sig != OS::TGT_SIGABRT)
        return -EINVAL;

    if (tgt_proc == nullptr)
        return -ESRCH;

    if (tgid != -1 && tgt_proc->tgid() != tgid)
        return -ESRCH;

    if (sig == OS::TGT_SIGABRT)
        exitGroupFunc(desc, 252, tc);

    return 0;
}

template <class OS>
SyscallReturn
socketFunc(SyscallDesc *desc, int num, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    int domain = p->getSyscallArg(tc, index);
    int type = p->getSyscallArg(tc, index);
    int prot = p->getSyscallArg(tc, index);

    int sim_fd = socket(domain, type, prot);
    if (sim_fd == -1)
        return -errno;

    auto sfdp = std::make_shared<SocketFDEntry>(sim_fd, domain, type, prot);
    int tgt_fd = p->fds->allocFD(sfdp);

    return tgt_fd;
}

template <class OS>
SyscallReturn
socketpairFunc(SyscallDesc *desc, int num, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    int domain = p->getSyscallArg(tc, index);
    int type = p->getSyscallArg(tc, index);
    int prot = p->getSyscallArg(tc, index);
    Addr svPtr = p->getSyscallArg(tc, index);

    BufferArg svBuf((Addr)svPtr, 2 * sizeof(int));
    int status = socketpair(domain, type, prot, (int *)svBuf.bufferPtr());
    if (status == -1)
        return -errno;

    int *fds = (int *)svBuf.bufferPtr();

    auto sfdp1 = std::make_shared<SocketFDEntry>(fds[0], domain, type, prot);
    fds[0] = p->fds->allocFD(sfdp1);
    auto sfdp2 = std::make_shared<SocketFDEntry>(fds[1], domain, type, prot);
    fds[1] = p->fds->allocFD(sfdp2);
    svBuf.copyOut(tc->getVirtProxy());

    return status;
}

template <class OS>
SyscallReturn
selectFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
{
    int retval;

    int index = 0;
    auto p = tc->getProcessPtr();
    int nfds_t = p->getSyscallArg(tc, index);
    Addr fds_read_ptr = p->getSyscallArg(tc, index);
    Addr fds_writ_ptr = p->getSyscallArg(tc, index);
    Addr fds_excp_ptr = p->getSyscallArg(tc, index);
    Addr time_val_ptr = p->getSyscallArg(tc, index);

    TypedBufferArg<typename OS::fd_set> rd_t(fds_read_ptr);
    TypedBufferArg<typename OS::fd_set> wr_t(fds_writ_ptr);
    TypedBufferArg<typename OS::fd_set> ex_t(fds_excp_ptr);
    TypedBufferArg<typename OS::timeval> tp(time_val_ptr);

    /**
     * Host fields. Notice that these use the definitions from the system
     * headers instead of the gem5 headers and libraries. If the host and
     * target have different header file definitions, this will not work.
     */
    fd_set rd_h;
    FD_ZERO(&rd_h);
    fd_set wr_h;
    FD_ZERO(&wr_h);
    fd_set ex_h;
    FD_ZERO(&ex_h);

    /**
     * Copy in the fd_set from the target.
     */
    if (fds_read_ptr)
        rd_t.copyIn(tc->getVirtProxy());
    if (fds_writ_ptr)
        wr_t.copyIn(tc->getVirtProxy());
    if (fds_excp_ptr)
        ex_t.copyIn(tc->getVirtProxy());

    /**
     * We need to translate the target file descriptor set into a host file
     * descriptor set. This involves both our internal process fd array
     * and the fd_set defined in Linux header files. The nfds field also
     * needs to be updated as it will be only target specific after
     * retrieving it from the target; the nfds value is expected to be the
     * highest file descriptor that needs to be checked, so we need to extend
     * it out for nfds_h when we do the update.
     */
    int nfds_h = 0;
    std::map<int, int> trans_map;
    auto try_add_host_set = [&](fd_set *tgt_set_entry,
                                fd_set *hst_set_entry,
                                int iter) -> bool
    {
        /**
         * By this point, we know that we are looking at a valid file
         * descriptor set on the target. We need to check if the target file
         * descriptor value passed in as iter is part of the set.
         */
        if (FD_ISSET(iter, tgt_set_entry)) {
            /**
             * We know that the target file descriptor belongs to the set,
             * but we do not yet know if the file descriptor is valid or
             * that we have a host mapping. Check that now.
             */
            auto hbfdp = std::dynamic_pointer_cast<HBFDEntry>((*p->fds)[iter]);
            if (!hbfdp)
                return true;
            auto sim_fd = hbfdp->getSimFD();

            /**
             * Add the sim_fd to tgt_fd translation into trans_map for use
             * later when we need to zero the target fd_set structures and
             * then update them with hits returned from the host select call.
             */
            trans_map[sim_fd] = iter;

            /**
             * We know that the host file descriptor exists so now we check
             * if we need to update the max count for nfds_h before passing
             * the duplicated structure into the host.
             */
            nfds_h = std::max(nfds_h - 1, sim_fd + 1);

            /**
             * Add the host file descriptor to the set that we are going to
             * pass into the host.
             */
            FD_SET(sim_fd, hst_set_entry);
        }
        return false;
    };

    for (int i = 0; i < nfds_t; i++) {
        if (fds_read_ptr) {
            bool ebadf = try_add_host_set((fd_set*)&*rd_t, &rd_h, i);
            if (ebadf) return -EBADF;
        }
        if (fds_writ_ptr) {
            bool ebadf = try_add_host_set((fd_set*)&*wr_t, &wr_h, i);
            if (ebadf) return -EBADF;
        }
        if (fds_excp_ptr) {
            bool ebadf = try_add_host_set((fd_set*)&*ex_t, &ex_h, i);
            if (ebadf) return -EBADF;
        }
    }

    if (time_val_ptr) {
        /**
         * It might be possible to decrement the timeval based on some
         * derivation of wall clock determined from elapsed simulator ticks
         * but that seems like overkill. Rather, we just set the timeval with
         * zero timeout. (There is no reason to block during the simulation
         * as it only decreases simulator performance.)
         */
        tp->tv_sec = 0;
        tp->tv_usec = 0;

        retval = select(nfds_h,
                        fds_read_ptr ? &rd_h : nullptr,
                        fds_writ_ptr ? &wr_h : nullptr,
                        fds_excp_ptr ? &ex_h : nullptr,
                        (timeval*)&*tp);
    } else {
        /**
         * If the timeval pointer is null, setup a new timeval structure to
         * pass into the host select call. Unfortunately, we will need to
         * manually check the return value and throw a retry fault if the
         * return value is zero. Allowing the system call to block will
         * likely deadlock the event queue.
         */
        struct timeval tv = { 0, 0 };

        retval = select(nfds_h,
                        fds_read_ptr ? &rd_h : nullptr,
                        fds_writ_ptr ? &wr_h : nullptr,
                        fds_excp_ptr ? &ex_h : nullptr,
                        &tv);

        if (retval == 0) {
            /**
             * If blocking indefinitely, check the signal list to see if a
             * signal would break the poll out of the retry cycle and try to
             * return the signal interrupt instead.
             */
            for (auto sig : tc->getSystemPtr()->signalList)
                if (sig.receiver == p)
                    return -EINTR;
            return SyscallReturn::retry();
        }
    }

    if (retval == -1)
        return -errno;

    FD_ZERO((fd_set*)&*rd_t);
    FD_ZERO((fd_set*)&*wr_t);
    FD_ZERO((fd_set*)&*ex_t);

    /**
     * We need to translate the host file descriptor set into a target file
     * descriptor set. This involves both our internal process fd array
     * and the fd_set defined in header files.
     */
    for (int i = 0; i < nfds_h; i++) {
        if (fds_read_ptr) {
            if (FD_ISSET(i, &rd_h))
                FD_SET(trans_map[i], (fd_set*)&*rd_t);
        }

        if (fds_writ_ptr) {
            if (FD_ISSET(i, &wr_h))
                FD_SET(trans_map[i], (fd_set*)&*wr_t);
        }

        if (fds_excp_ptr) {
            if (FD_ISSET(i, &ex_h))
                FD_SET(trans_map[i], (fd_set*)&*ex_t);
        }
    }

    if (fds_read_ptr)
        rd_t.copyOut(tc->getVirtProxy());
    if (fds_writ_ptr)
        wr_t.copyOut(tc->getVirtProxy());
    if (fds_excp_ptr)
        ex_t.copyOut(tc->getVirtProxy());
    if (time_val_ptr)
        tp.copyOut(tc->getVirtProxy());

    return retval;
}

template <class OS>
SyscallReturn
readFunc(SyscallDesc *desc, int num, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    int tgt_fd = p->getSyscallArg(tc, index);
    Addr buf_ptr = p->getSyscallArg(tc, index);
    int nbytes = p->getSyscallArg(tc, index);

    auto hbfdp = std::dynamic_pointer_cast<HBFDEntry>((*p->fds)[tgt_fd]);
    if (!hbfdp)
        return -EBADF;
    int sim_fd = hbfdp->getSimFD();

    struct pollfd pfd;
    pfd.fd = sim_fd;
    pfd.events = POLLIN | POLLPRI;
    if ((poll(&pfd, 1, 0) == 0)
        && !(hbfdp->getFlags() & OS::TGT_O_NONBLOCK))
        return SyscallReturn::retry();

    BufferArg buf_arg(buf_ptr, nbytes);
    int bytes_read = read(sim_fd, buf_arg.bufferPtr(), nbytes);

    if (bytes_read > 0)
        buf_arg.copyOut(tc->getVirtProxy());

    return (bytes_read == -1) ? -errno : bytes_read;
}

template <class OS>
SyscallReturn
writeFunc(SyscallDesc *desc, int num, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    int tgt_fd = p->getSyscallArg(tc, index);
    Addr buf_ptr = p->getSyscallArg(tc, index);
    int nbytes = p->getSyscallArg(tc, index);

    auto hbfdp = std::dynamic_pointer_cast<HBFDEntry>((*p->fds)[tgt_fd]);
    if (!hbfdp)
        return -EBADF;
    int sim_fd = hbfdp->getSimFD();

    BufferArg buf_arg(buf_ptr, nbytes);
    buf_arg.copyIn(tc->getVirtProxy());

    struct pollfd pfd;
    pfd.fd = sim_fd;
    pfd.events = POLLOUT;

    /**
     * We don't want to poll on /dev/random. The kernel will not enable the
     * file descriptor for writing unless the entropy in the system falls
     * below write_wakeup_threshold. This is not guaranteed to happen
     * depending on host settings.
     */
    auto ffdp = std::dynamic_pointer_cast<FileFDEntry>(hbfdp);
    if (ffdp && (ffdp->getFileName() != "/dev/random")) {
        if (!poll(&pfd, 1, 0) && !(ffdp->getFlags() & OS::TGT_O_NONBLOCK))
            return SyscallReturn::retry();
    }

    int bytes_written = write(sim_fd, buf_arg.bufferPtr(), nbytes);

    if (bytes_written != -1)
        fsync(sim_fd);

    return (bytes_written == -1) ? -errno : bytes_written;
}

template <class OS>
SyscallReturn
wait4Func(SyscallDesc *desc, int num, ThreadContext *tc)
{
    int index = 0;
    auto p = tc->getProcessPtr();
    pid_t pid = p->getSyscallArg(tc, index);
    Addr statPtr = p->getSyscallArg(tc, index);
    int options = p->getSyscallArg(tc, index);
    Addr rusagePtr = p->getSyscallArg(tc, index);

    if (rusagePtr)
        DPRINTF_SYSCALL(Verbose, "wait4: rusage pointer provided %lx, however "
                 "functionality not supported. Ignoring rusage pointer.\n",
                 rusagePtr);

    /**
     * Currently, wait4 is only implemented so that it will wait for children
     * exit conditions which are denoted by a SIGCHLD signals posted into the
     * system signal list. We return no additional information via any of the
     * parameters supplied to wait4. If nothing is found in the system signal
     * list, we will wait indefinitely for SIGCHLD to post by retrying the
     * call.
     */
    System *sysh = tc->getSystemPtr();
    std::list<BasicSignal>::iterator iter;
    for (iter=sysh->signalList.begin(); iter!=sysh->signalList.end(); iter++) {
        if (iter->receiver == p) {
            if (pid < -1) {
                if ((iter->sender->pgid() == -pid)
                    && (iter->signalValue == OS::TGT_SIGCHLD))
                    goto success;
            } else if (pid == -1) {
                if (iter->signalValue == OS::TGT_SIGCHLD)
                    goto success;
            } else if (pid == 0) {
                if ((iter->sender->pgid() == p->pgid())
                    && (iter->signalValue == OS::TGT_SIGCHLD))
                    goto success;
            } else {
                if ((iter->sender->pid() == pid)
                    && (iter->signalValue == OS::TGT_SIGCHLD))
                    goto success;
            }
        }
    }

    return (options & OS::TGT_WNOHANG) ? 0 : SyscallReturn::retry();

success:
    // Set status to EXITED for WIFEXITED evaluations.
    const int EXITED = 0;
    BufferArg statusBuf(statPtr, sizeof(int));
    *(int *)statusBuf.bufferPtr() = EXITED;
    statusBuf.copyOut(tc->getVirtProxy());

    // Return the child PID.
    pid_t retval = iter->sender->pid();
    sysh->signalList.erase(iter);
    return retval;
}

template <class OS>
SyscallReturn
acceptFunc(SyscallDesc *desc, int num, ThreadContext *tc)
{
    struct sockaddr sa;
    socklen_t addrLen;
    int host_fd;
    int index = 0;
    auto p = tc->getProcessPtr();
    int tgt_fd = p->getSyscallArg(tc, index);
    Addr addrPtr = p->getSyscallArg(tc, index);
    Addr lenPtr = p->getSyscallArg(tc, index);

    BufferArg *lenBufPtr = nullptr;
    BufferArg *addrBufPtr = nullptr;

    auto sfdp = std::dynamic_pointer_cast<SocketFDEntry>((*p->fds)[tgt_fd]);
    if (!sfdp)
        return -EBADF;
    int sim_fd = sfdp->getSimFD();

    /**
     * We poll the socket file descriptor first to guarantee that we do not
     * block on our accept call. The socket can be opened without the
     * non-blocking flag (it blocks). This will cause deadlocks between
     * communicating processes.
     */
    struct pollfd pfd;
    pfd.fd = sim_fd;
    pfd.events = POLLIN | POLLPRI;
    if ((poll(&pfd, 1, 0) == 0)
        && !(sfdp->getFlags() & OS::TGT_O_NONBLOCK))
        return SyscallReturn::retry();

    if (lenPtr) {
        lenBufPtr = new BufferArg(lenPtr, sizeof(socklen_t));
        lenBufPtr->copyIn(tc->getVirtProxy());
        memcpy(&addrLen, (socklen_t *)lenBufPtr->bufferPtr(),
               sizeof(socklen_t));
    }

    if (addrPtr) {
        addrBufPtr = new BufferArg(addrPtr, sizeof(struct sockaddr));
        addrBufPtr->copyIn(tc->getVirtProxy());
        memcpy(&sa, (struct sockaddr *)addrBufPtr->bufferPtr(),
               sizeof(struct sockaddr));
    }

    host_fd = accept(sim_fd, &sa, &addrLen);

    if (host_fd == -1)
        return -errno;

    if (addrPtr) {
        memcpy(addrBufPtr->bufferPtr(), &sa, sizeof(sa));
        addrBufPtr->copyOut(tc->getVirtProxy());
        delete(addrBufPtr);
    }

    if (lenPtr) {
        *(socklen_t *)lenBufPtr->bufferPtr() = addrLen;
        lenBufPtr->copyOut(tc->getVirtProxy());
        delete(lenBufPtr);
    }

    auto afdp = std::make_shared<SocketFDEntry>(host_fd, sfdp->_domain,
                                                sfdp->_type, sfdp->_protocol);
    return p->fds->allocFD(afdp);
}

/// Target eventfd() function.
template <class OS>
SyscallReturn
eventfdFunc(SyscallDesc *desc, int num, ThreadContext *tc)
{
#if defined(__linux__)
    int index = 0;
    auto p = tc->getProcessPtr();
    unsigned initval = p->getSyscallArg(tc, index);
    int in_flags = p->getSyscallArg(tc, index);

    int sim_fd = eventfd(initval, in_flags);
    if (sim_fd == -1)
        return -errno;

    bool cloexec = in_flags & OS::TGT_O_CLOEXEC;

    int flags = cloexec ? OS::TGT_O_CLOEXEC : 0;
    flags |= (in_flags & OS::TGT_O_NONBLOCK) ? OS::TGT_O_NONBLOCK : 0;

    auto hbfdp = std::make_shared<HBFDEntry>(flags, sim_fd, cloexec);
    int tgt_fd = p->fds->allocFD(hbfdp);
    return tgt_fd;
#else
    warnUnsupportedOS("eventfd");
    return -1;
#endif
}

#endif // __SIM_SYSCALL_EMUL_HH__