summaryrefslogtreecommitdiff
path: root/coregrind/m_signals.c
blob: 05916223b2aae0b24387b4650317b7ded006da6f (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

/*--------------------------------------------------------------------*/
/*--- Implementation of POSIX signals.                 m_signals.c ---*/
/*--------------------------------------------------------------------*/
 
/*
   This file is part of Valgrind, a dynamic binary instrumentation
   framework.

   Copyright (C) 2000-2005 Julian Seward 
      jseward@acm.org

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

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

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307, USA.

   The GNU General Public License is contained in the file COPYING.
*/

/* 
   Signal handling.

   There are 4 distinct classes of signal:

   1. Synchronous, instruction-generated (SIGILL, FPE, BUS, SEGV and
   TRAP): these are signals as a result of an instruction fault.  If
   we get one while running client code, then we just do the
   appropriate thing.  If it happens while running Valgrind code, then
   it indicates a Valgrind bug.  Note that we "manually" implement
   automatic stack growth, such that if a fault happens near the
   client process stack, it is extended in the same way the kernel
   would, and the fault is never reported to the client program.

   2. Asynchronous varients of the above signals: If the kernel tries
   to deliver a sync signal while it is blocked, it just kills the
   process.  Therefore, we can't block those signals if we want to be
   able to report on bugs in Valgrind.  This means that we're also
   open to receiving those signals from other processes, sent with
   kill.  We could get away with just dropping them, since they aren't
   really signals that processes send to each other.

   3. Synchronous, general signals.  If a thread/process sends itself
   a signal with kill, its expected to be synchronous: ie, the signal
   will have been delivered by the time the syscall finishes.
   
   4. Asyncronous, general signals.  All other signals, sent by
   another process with kill.  These are generally blocked, except for
   two special cases: we poll for them each time we're about to run a
   thread for a time quanta, and while running blocking syscalls.


   In addition, we define two signals for internal use: SIGVGCHLD and
   SIGVGKILL.  SIGVGCHLD is used to indicate thread death to any
   reaping thread (the master thread).  It is always blocked and never
   delivered as a signal; it is always polled with sigtimedwait.

   SIGVGKILL is used to terminate threads.  When one thread wants
   another to exit, it will set its exitreason and send it SIGVGKILL
   if it appears to be blocked in a syscall.


   We use a kernel thread for each application thread.  When the
   thread allows itself to be open to signals, it sets the thread
   signal mask to what the client application set it to.  This means
   that we get the kernel to do all signal routing: under Valgrind,
   signals get delivered in the same way as in the non-Valgrind case
   (the exception being for the sync signal set, since they're almost
   always unblocked).
 */

#include "pub_core_basics.h"
#include "pub_core_debuglog.h"
#include "pub_core_threadstate.h"
#include "pub_core_clientstate.h"
#include "pub_core_aspacemgr.h"
#include "pub_core_debugger.h"      // For VG_(start_debugger)
#include "pub_core_errormgr.h"
#include "pub_core_libcbase.h"
#include "pub_core_libcassert.h"
#include "pub_core_libcprint.h"
#include "pub_core_libcproc.h"
#include "pub_core_libcsignal.h"
#include "pub_core_machine.h"
#include "pub_core_mallocfree.h"
#include "pub_core_options.h"
#include "pub_core_scheduler.h"
#include "pub_core_signals.h"
#include "pub_core_sigframe.h"      // For VG_(sigframe_create)()
#include "pub_core_stacks.h"        // For VG_(change_stack)()
#include "pub_core_stacktrace.h"    // For VG_(get_and_pp_StackTrace)()
#include "pub_core_syscall.h"
#include "pub_core_syswrap.h"
#include "pub_core_tooliface.h"
#include "pub_core_coredump.h"
#include "vki_unistd.h"


/* ---------------------------------------------------------------------
   Forwards decls.
   ------------------------------------------------------------------ */

static void sync_signalhandler  ( Int sigNo, vki_siginfo_t *info, struct vki_ucontext * );
static void async_signalhandler ( Int sigNo, vki_siginfo_t *info, struct vki_ucontext * );
static void sigvgkill_handler	   ( Int sigNo, vki_siginfo_t *info, struct vki_ucontext * );

static const Char *signame(Int sigNo);

/* Maximum usable signal. */
Int VG_(max_signal) = _VKI_NSIG;

#define N_QUEUED_SIGNALS	8

typedef struct SigQueue {
   Int	next;
   vki_siginfo_t sigs[N_QUEUED_SIGNALS];
} SigQueue;

#if defined(VGP_x86_linux)
#  define VG_UCONTEXT_INSTR_PTR(uc)       ((uc)->uc_mcontext.eip)
#  define VG_UCONTEXT_STACK_PTR(uc)       ((uc)->uc_mcontext.esp)
#  define VG_UCONTEXT_FRAME_PTR(uc)       ((uc)->uc_mcontext.ebp)
#  define VG_UCONTEXT_SYSCALL_NUM(uc)     ((uc)->uc_mcontext.eax)
#  define VG_UCONTEXT_SYSCALL_SYSRES(uc)                        \
      /* Convert the value in uc_mcontext.eax into a SysRes. */ \
      VG_(mk_SysRes_x86_linux)( (uc)->uc_mcontext.eax )
#  define VG_UCONTEXT_LINK_REG(uc)        0 /* Dude, where's my LR? */

#elif defined(VGP_amd64_linux)
#  define VG_UCONTEXT_INSTR_PTR(uc)       ((uc)->uc_mcontext.rip)
#  define VG_UCONTEXT_STACK_PTR(uc)       ((uc)->uc_mcontext.rsp)
#  define VG_UCONTEXT_FRAME_PTR(uc)       ((uc)->uc_mcontext.rbp)
#  define VG_UCONTEXT_SYSCALL_NUM(uc)     ((uc)->uc_mcontext.rax)
#  define VG_UCONTEXT_SYSCALL_SYSRES(uc)                        \
      /* Convert the value in uc_mcontext.rax into a SysRes. */ \
      VG_(mk_SysRes_amd64_linux)( (uc)->uc_mcontext.rax )
#  define VG_UCONTEXT_LINK_REG(uc)        0 /* No LR on amd64 either */

#elif defined(VGP_ppc32_linux)
/* Comments from Paul Mackerras 25 Nov 05:

   > I'm tracking down a problem where V's signal handling doesn't
   > work properly on a ppc440gx running 2.4.20.  The problem is that
   > the ucontext being presented to V's sighandler seems completely
   > bogus.

   > V's kernel headers and hence ucontext layout are derived from
   > 2.6.9.  I compared include/asm-ppc/ucontext.h from 2.4.20 and
   > 2.6.13.

   > Can I just check my interpretation: the 2.4.20 one contains the
   > uc_mcontext field in line, whereas the 2.6.13 one has a pointer
   > to said struct?  And so if V is using the 2.6.13 struct then a
   > 2.4.20 one will make no sense to it.

   Not quite... what is inline in the 2.4.20 version is a
   sigcontext_struct, not an mcontext.  The sigcontext looks like
   this:

     struct sigcontext_struct {
        unsigned long   _unused[4];
        int             signal;
        unsigned long   handler;
        unsigned long   oldmask;
        struct pt_regs  *regs;
     };

   The regs pointer of that struct ends up at the same offset as the
   uc_regs of the 2.6 struct ucontext, and a struct pt_regs is the
   same as the mc_gregs field of the mcontext.  In fact the integer
   regs are followed in memory by the floating point regs on 2.4.20.

   Thus if you are using the 2.6 definitions, it should work on 2.4.20
   provided that you go via uc->uc_regs rather than looking in
   uc->uc_mcontext directly.

   There is another subtlety: 2.4.20 doesn't save the vector regs when
   delivering a signal, and 2.6.x only saves the vector regs if the
   process has ever used an altivec instructions.  If 2.6.x does save
   the vector regs, it sets the MSR_VEC bit in
   uc->uc_regs->mc_gregs[PT_MSR], otherwise it clears it.  That bit
   will always be clear under 2.4.20.  So you can use that bit to tell
   whether uc->uc_regs->mc_vregs is valid. */
#  define VG_UCONTEXT_INSTR_PTR(uc)       ((uc)->uc_regs->mc_gregs[VKI_PT_NIP])
#  define VG_UCONTEXT_STACK_PTR(uc)       ((uc)->uc_regs->mc_gregs[VKI_PT_R1])
#  define VG_UCONTEXT_FRAME_PTR(uc)       ((uc)->uc_regs->mc_gregs[VKI_PT_R1])
#  define VG_UCONTEXT_SYSCALL_NUM(uc)     ((uc)->uc_regs->mc_gregs[VKI_PT_R0])
#  define VG_UCONTEXT_SYSCALL_SYSRES(uc)                            \
      /* Convert the values in uc_mcontext r3,cr into a SysRes. */  \
      VG_(mk_SysRes_ppc32_linux)(                                   \
         (uc)->uc_regs->mc_gregs[VKI_PT_R3],                        \
         (((uc)->uc_regs->mc_gregs[VKI_PT_CCR] >> 28) & 1)          \
      )
#  define VG_UCONTEXT_LINK_REG(uc)        ((uc)->uc_regs->mc_gregs[VKI_PT_LNK]) 

#elif defined(VGP_ppc64_linux)
#  define VG_UCONTEXT_INSTR_PTR(uc)       ((uc)->uc_mcontext.gp_regs[VKI_PT_NIP])
#  define VG_UCONTEXT_STACK_PTR(uc)       ((uc)->uc_mcontext.gp_regs[VKI_PT_R1])
#  define VG_UCONTEXT_FRAME_PTR(uc)       ((uc)->uc_mcontext.gp_regs[VKI_PT_R1])
#  define VG_UCONTEXT_SYSCALL_NUM(uc)     ((uc)->uc_mcontext.gp_regs[VKI_PT_R0])
#if 0
#  define VG_UCONTEXT_SYSCALL_SYSRES(uc)                            \
      /* Convert the values in uc_mcontext r3,cr into a SysRes. */  \
      VG_(mk_SysRes_ppc64_linux)(                                   \
         (uc)->uc_mcontext.gp_regs[VKI_PT_R3],                      \
         (((uc)->uc_mcontext.gp_regs[VKI_PT_CCR] >> 28) & 1)        \
      )
#else
   /* Dubious hack: if there is an error, only consider the lowest 8
      bits of r3.  memcheck/tests/post-syscall shows a case where an
      interrupted syscall should have produced a ucontext with 0x4
      (VKI_EINTR) in r3 but is in fact producing 0x204. */
   /* Awaiting clarification from PaulM.  Evidently 0x204 is
      ERESTART_RESTARTBLOCK, which shouldn't have made it into user
      space. */
   static inline SysRes VG_UCONTEXT_SYSCALL_SYSRES( struct vki_ucontext* uc )
   {
      ULong err = (uc->uc_mcontext.gp_regs[VKI_PT_CCR] >> 28) & 1;
      ULong r3  = uc->uc_mcontext.gp_regs[VKI_PT_R3];
      if (err) r3 &= 0xFF;
      return VG_(mk_SysRes_ppc64_linux)( r3, err );
   }
#endif
#  define VG_UCONTEXT_LINK_REG(uc)        ((uc)->uc_mcontext.gp_regs[VKI_PT_LNK]) 

#else
#  error Unknown platform
#endif

/* ---------------------------------------------------------------------
   HIGH LEVEL STUFF TO DO WITH SIGNALS: POLICY (MOSTLY)
   ------------------------------------------------------------------ */

/* ---------------------------------------------------------------------
   Signal state for this process.
   ------------------------------------------------------------------ */


/* Base-ment of these arrays[_VKI_NSIG].

   Valid signal numbers are 1 .. _VKI_NSIG inclusive.
   Rather than subtracting 1 for indexing these arrays, which
   is tedious and error-prone, they are simply dimensioned 1 larger,
   and entry [0] is not used. 
 */


/* -----------------------------------------------------
   Static client signal state (SCSS).  This is the state
   that the client thinks it has the kernel in.  
   SCSS records verbatim the client's settings.  These 
   are mashed around only when SKSS is calculated from it.
   -------------------------------------------------- */

typedef 
   struct {
      void* scss_handler;  /* VKI_SIG_DFL or VKI_SIG_IGN or ptr to
                              client's handler */
      UInt  scss_flags;
      vki_sigset_t scss_mask;
      void* scss_restorer; /* where sigreturn goes */
   }
   SCSS_Per_Signal;

typedef 
   struct {
      /* per-signal info */
      SCSS_Per_Signal scss_per_sig[1+_VKI_NSIG];

      /* Additional elements to SCSS not stored here:
         - for each thread, the thread's blocking mask
         - for each thread in WaitSIG, the set of waited-on sigs
      */
      } 
      SCSS;

static SCSS scss;


/* -----------------------------------------------------
   Static kernel signal state (SKSS).  This is the state
   that we have the kernel in.  It is computed from SCSS.
   -------------------------------------------------- */

/* Let's do: 
     sigprocmask assigns to all thread masks
     so that at least everything is always consistent
   Flags:
     SA_SIGINFO -- we always set it, and honour it for the client
     SA_NOCLDSTOP -- passed to kernel
     SA_ONESHOT or SA_RESETHAND -- pass through
     SA_RESTART -- we observe this but set our handlers to always restart
     SA_NOMASK or SA_NODEFER -- we observe this, but our handlers block everything
     SA_ONSTACK -- pass through
     SA_NOCLDWAIT -- pass through
*/


typedef 
   struct {
      void* skss_handler;  /* VKI_SIG_DFL or VKI_SIG_IGN 
                              or ptr to our handler */
      UInt skss_flags;
      /* There is no skss_mask, since we know that we will always ask
         for all signals to be blocked in our sighandlers. */
      /* Also there is no skss_restorer. */
   }
   SKSS_Per_Signal;

typedef 
   struct {
      SKSS_Per_Signal skss_per_sig[1+_VKI_NSIG];
   } 
   SKSS;

static SKSS skss;

static Bool is_sig_ign(Int sigNo)
{
   vg_assert(sigNo >= 1 && sigNo <= _VKI_NSIG);

   return scss.scss_per_sig[sigNo].scss_handler == VKI_SIG_IGN;
}

/* ---------------------------------------------------------------------
   Compute the SKSS required by the current SCSS.
   ------------------------------------------------------------------ */

static 
void pp_SKSS ( void )
{
   Int sig;
   VG_(printf)("\n\nSKSS:\n");
   for (sig = 1; sig <= _VKI_NSIG; sig++) {
      VG_(printf)("sig %d:  handler 0x%x,  flags 0x%x\n", sig,
                  skss.skss_per_sig[sig].skss_handler,
                  skss.skss_per_sig[sig].skss_flags );

   }
}

/* This is the core, clever bit.  Computation is as follows:

   For each signal
      handler = if client has a handler, then our handler
                else if client is DFL, then our handler as well
                else (client must be IGN)
			then hander is IGN
*/
static
void calculate_SKSS_from_SCSS ( SKSS* dst )
{
   Int   sig;
   UInt  scss_flags;
   UInt  skss_flags;

   for (sig = 1; sig <= _VKI_NSIG; sig++) {
      void *skss_handler;
      void *scss_handler;
      
      scss_handler = scss.scss_per_sig[sig].scss_handler;
      scss_flags   = scss.scss_per_sig[sig].scss_flags;

      switch(sig) {
      case VKI_SIGSEGV:
      case VKI_SIGBUS:
      case VKI_SIGFPE:
      case VKI_SIGILL:
      case VKI_SIGTRAP:
	 /* For these, we always want to catch them and report, even
	    if the client code doesn't. */
	 skss_handler = sync_signalhandler;
	 break;

      case VKI_SIGCONT:
	 /* Let the kernel handle SIGCONT unless the client is actually
	    catching it. */
      case VKI_SIGCHLD:                                                        
      case VKI_SIGWINCH:                                                       
      case VKI_SIGURG:                                                         
         /* For signals which are have a default action of Ignore,             
            only set a handler if the client has set a signal handler.         
            Otherwise the kernel will interrupt a syscall which                
            wouldn't have otherwise been interrupted. */                 
	 if (scss.scss_per_sig[sig].scss_handler == VKI_SIG_DFL)
	    skss_handler = VKI_SIG_DFL;
	 else if (scss.scss_per_sig[sig].scss_handler == VKI_SIG_IGN)
	    skss_handler = VKI_SIG_IGN;
	 else
	    skss_handler = async_signalhandler;
	 break;

      default:
         // VKI_SIGVG* are runtime variables, so we can't make them            
         // cases in the switch, so we handle them in the 'default' case.
	 if (sig == VG_SIGVGKILL)
	    skss_handler = sigvgkill_handler;
	 else {
	    if (scss_handler == VKI_SIG_IGN)
	       skss_handler = VKI_SIG_IGN;
	    else 
	       skss_handler = async_signalhandler;
	 }
	 break;
      }

      /* Flags */

      skss_flags = 0;

      /* SA_NOCLDSTOP, SA_NOCLDWAIT: pass to kernel */
      skss_flags |= scss_flags & (VKI_SA_NOCLDSTOP | VKI_SA_NOCLDWAIT);

      /* SA_ONESHOT: ignore client setting */
      
      /* SA_RESTART: ignore client setting and always set it for us.
	 Though we never rely on the kernel to restart a
	 syscall, we observe whether it wanted to restart the syscall
	 or not, which is needed by 
         VG_(fixup_guest_state_after_syscall_interrupted) */
      skss_flags |= VKI_SA_RESTART;

      /* SA_NOMASK: ignore it */

      /* SA_ONSTACK: client setting is irrelevant here */
      /* We don't set a signal stack, so ignore */

      /* always ask for SA_SIGINFO */
      skss_flags |= VKI_SA_SIGINFO;

      /* use our own restorer */
      skss_flags |= VKI_SA_RESTORER;

      /* Create SKSS entry for this signal. */
      if (sig != VKI_SIGKILL && sig != VKI_SIGSTOP)
         dst->skss_per_sig[sig].skss_handler = skss_handler;
      else
         dst->skss_per_sig[sig].skss_handler = VKI_SIG_DFL;

      dst->skss_per_sig[sig].skss_flags   = skss_flags;
   }

   /* Sanity checks. */
   vg_assert(dst->skss_per_sig[VKI_SIGKILL].skss_handler == VKI_SIG_DFL);
   vg_assert(dst->skss_per_sig[VKI_SIGSTOP].skss_handler == VKI_SIG_DFL);

   if (0)
      pp_SKSS();
}


/* ---------------------------------------------------------------------
   After a possible SCSS change, update SKSS and the kernel itself.
   ------------------------------------------------------------------ */

// We need two levels of macro-expansion here to convert __NR_rt_sigreturn
// to a number before converting it to a string... sigh.
extern void my_sigreturn(void);

#if defined(VGP_x86_linux)
#  define _MYSIG(name) \
   ".text\n" \
   "my_sigreturn:\n" \
   "	movl	$" #name ", %eax\n" \
   "	int	$0x80\n" \
   ".previous\n"
#elif defined(VGP_amd64_linux)
#  define _MYSIG(name) \
   ".text\n" \
   "my_sigreturn:\n" \
   "	movq	$" #name ", %rax\n" \
   "	syscall\n" \
   ".previous\n"
#elif defined(VGP_ppc32_linux)
#  define _MYSIG(name) \
   ".text\n" \
   "my_sigreturn:\n" \
   "	li	0, " #name "\n" \
   "	sc\n" \
   ".previous\n"
#elif defined(VGP_ppc64_linux)
#  define _MYSIG(name) \
   ".align   2\n" \
   ".globl   my_sigreturn\n" \
   ".section \".opd\",\"aw\"\n" \
   ".align   3\n" \
   "my_sigreturn:\n" \
   ".quad    .my_sigreturn,.TOC.@tocbase,0\n" \
   ".previous\n" \
   ".type    .my_sigreturn,@function\n" \
   ".globl   .my_sigreturn\n" \
   ".my_sigreturn:\n" \
   "	li	0, " #name "\n" \
   "	sc\n"
#else
#  error Unknown platform
#endif

#define MYSIG(name)  _MYSIG(name)
asm(
   MYSIG(__NR_rt_sigreturn)
);


static void handle_SCSS_change ( Bool force_update )
{
   Int  res, sig;
   SKSS skss_old;
   struct vki_sigaction ksa, ksa_old;

   /* Remember old SKSS and calculate new one. */
   skss_old = skss;
   calculate_SKSS_from_SCSS ( &skss );

   /* Compare the new SKSS entries vs the old ones, and update kernel
      where they differ. */
   for (sig = 1; sig <= VG_(max_signal); sig++) {

      /* Trying to do anything with SIGKILL is pointless; just ignore
         it. */
      if (sig == VKI_SIGKILL || sig == VKI_SIGSTOP)
         continue;

      if (!force_update) {
         if ((skss_old.skss_per_sig[sig].skss_handler
              == skss.skss_per_sig[sig].skss_handler)
             && (skss_old.skss_per_sig[sig].skss_flags
                 == skss.skss_per_sig[sig].skss_flags))
            /* no difference */
            continue;
      }

      ksa.ksa_handler = skss.skss_per_sig[sig].skss_handler;
      ksa.sa_flags    = skss.skss_per_sig[sig].skss_flags;
#     if !defined(VGP_ppc32_linux)
      ksa.sa_restorer = my_sigreturn;
#     endif
      /* Re above ifdef (also the assertion below), PaulM says:
         The sa_restorer field is not used at all on ppc.  Glibc
         converts the sigaction you give it into a kernel sigaction,
         but it doesn't put anything in the sa_restorer field.
      */

      /* block all signals in handler */
      VG_(sigfillset)( &ksa.sa_mask );
      VG_(sigdelset)( &ksa.sa_mask, VKI_SIGKILL );
      VG_(sigdelset)( &ksa.sa_mask, VKI_SIGSTOP );

      if (VG_(clo_trace_signals) && VG_(clo_verbosity) > 2)
         VG_(message)(Vg_DebugMsg, 
            "setting ksig %d to: hdlr 0x%x, flags 0x%x, "
            "mask(63..0) 0x%x 0x%x",
            sig, ksa.ksa_handler,
            ksa.sa_flags,
            ksa.sa_mask.sig[1], 
            ksa.sa_mask.sig[0] 
         );

      res = VG_(sigaction)( sig, &ksa, &ksa_old );
      vg_assert(res == 0);

      /* Since we got the old sigaction more or less for free, might
         as well extract the maximum sanity-check value from it. */
      if (!force_update) {
         vg_assert(ksa_old.ksa_handler 
                   == skss_old.skss_per_sig[sig].skss_handler);
         vg_assert(ksa_old.sa_flags 
                   == skss_old.skss_per_sig[sig].skss_flags);
#        if !defined(VGP_ppc32_linux)
         vg_assert(ksa_old.sa_restorer 
                   == my_sigreturn);
#        endif
         VG_(sigaddset)( &ksa_old.sa_mask, VKI_SIGKILL );
         VG_(sigaddset)( &ksa_old.sa_mask, VKI_SIGSTOP );
         vg_assert(VG_(isfullsigset)( &ksa_old.sa_mask ));
      }
   }
}


/* ---------------------------------------------------------------------
   Update/query SCSS in accordance with client requests.
   ------------------------------------------------------------------ */

/* Logic for this alt-stack stuff copied directly from do_sigaltstack
   in kernel/signal.[ch] */

/* True if we are on the alternate signal stack.  */
static Bool on_sig_stack ( ThreadId tid, Addr m_SP )
{
   ThreadState *tst = VG_(get_ThreadState)(tid);

   return (m_SP - (Addr)tst->altstack.ss_sp < tst->altstack.ss_size);
}

static Int sas_ss_flags ( ThreadId tid, Addr m_SP )
{
   ThreadState *tst = VG_(get_ThreadState)(tid);

   return (tst->altstack.ss_size == 0 
              ? VKI_SS_DISABLE
              : on_sig_stack(tid, m_SP) ? VKI_SS_ONSTACK : 0);
}


SysRes VG_(do_sys_sigaltstack) ( ThreadId tid, vki_stack_t* ss, vki_stack_t* oss )
{
   Addr m_SP;

   vg_assert(VG_(is_valid_tid)(tid));
   m_SP  = VG_(get_SP)(tid);

   if (VG_(clo_trace_signals))
      VG_(message)(Vg_DebugExtraMsg, 
         "sys_sigaltstack: tid %d, "
         "ss %p, oss %p (current SP %p)",
         tid, (void*)ss, (void*)oss, (void*)m_SP );

   if (oss != NULL) {
      oss->ss_sp    = VG_(threads)[tid].altstack.ss_sp;
      oss->ss_size  = VG_(threads)[tid].altstack.ss_size;
      oss->ss_flags = VG_(threads)[tid].altstack.ss_flags | sas_ss_flags(tid, m_SP);
   }

   if (ss != NULL) {
      if (on_sig_stack(tid, VG_(get_SP)(tid))) {
         return VG_(mk_SysRes_Error)( VKI_EPERM );
      }
      if (ss->ss_flags != VKI_SS_DISABLE 
          && ss->ss_flags != VKI_SS_ONSTACK 
          && ss->ss_flags != 0) {
         return VG_(mk_SysRes_Error)( VKI_EINVAL );
      }
      if (ss->ss_flags == VKI_SS_DISABLE) {
         VG_(threads)[tid].altstack.ss_flags = VKI_SS_DISABLE;
      } else {
         if (ss->ss_size < VKI_MINSIGSTKSZ) {
            return VG_(mk_SysRes_Error)( VKI_ENOMEM );
         }

	 VG_(threads)[tid].altstack.ss_sp    = ss->ss_sp;
	 VG_(threads)[tid].altstack.ss_size  = ss->ss_size;
	 VG_(threads)[tid].altstack.ss_flags = 0;
      }
   }
   return VG_(mk_SysRes_Success)( 0 );
}


SysRes VG_(do_sys_sigaction) ( Int signo, 
                               const struct vki_sigaction *new_act, 
                               struct vki_sigaction *old_act )
{
   if (VG_(clo_trace_signals))
      VG_(message)(Vg_DebugExtraMsg, 
         "sys_sigaction: sigNo %d, "
         "new %p, old %p, new flags 0x%llx",
         signo, (UWord)new_act, (UWord)old_act,
         (ULong)(new_act ? new_act->sa_flags : 0) );

   /* Rule out various error conditions.  The aim is to ensure that if
      when the call is passed to the kernel it will definitely
      succeed. */

   /* Reject out-of-range signal numbers. */
   if (signo < 1 || signo > VG_(max_signal)) goto bad_signo;

   /* don't let them use our signals */
   if ( (signo > VG_SIGVGRTUSERMAX)
	&& new_act
	&& !(new_act->ksa_handler == VKI_SIG_DFL 
             || new_act->ksa_handler == VKI_SIG_IGN) )
      goto bad_signo_reserved;

   /* Reject attempts to set a handler (or set ignore) for SIGKILL. */
   if ( (signo == VKI_SIGKILL || signo == VKI_SIGSTOP)
       && new_act
       && new_act->ksa_handler != VKI_SIG_DFL)
      goto bad_sigkill_or_sigstop;

   /* If the client supplied non-NULL old_act, copy the relevant SCSS
      entry into it. */
   if (old_act) {
      old_act->ksa_handler = scss.scss_per_sig[signo].scss_handler;
      old_act->sa_flags    = scss.scss_per_sig[signo].scss_flags;
      old_act->sa_mask     = scss.scss_per_sig[signo].scss_mask;
      old_act->sa_restorer = scss.scss_per_sig[signo].scss_restorer;
   }

   /* And now copy new SCSS entry from new_act. */
   if (new_act) {
      scss.scss_per_sig[signo].scss_handler  = new_act->ksa_handler;
      scss.scss_per_sig[signo].scss_flags    = new_act->sa_flags;
      scss.scss_per_sig[signo].scss_mask     = new_act->sa_mask;
      scss.scss_per_sig[signo].scss_restorer = new_act->sa_restorer;

      VG_(sigdelset)(&scss.scss_per_sig[signo].scss_mask, VKI_SIGKILL);
      VG_(sigdelset)(&scss.scss_per_sig[signo].scss_mask, VKI_SIGSTOP);
   }

   /* All happy bunnies ... */
   if (new_act) {
      handle_SCSS_change( False /* lazy update */ );
   }
   return VG_(mk_SysRes_Success)( 0 );

  bad_signo:
   if (VG_(showing_core_errors)()) {
      VG_(message)(Vg_UserMsg,
                   "Warning: bad signal number %d in sigaction()", 
                   signo);
   }
   return VG_(mk_SysRes_Error)( VKI_EINVAL );

  bad_signo_reserved:
   if (VG_(showing_core_errors)()) {
      VG_(message)(Vg_UserMsg,
		   "Warning: ignored attempt to set %s handler in sigaction();",
		   signame(signo));
      VG_(message)(Vg_UserMsg,
		   "         the %s signal is used internally by Valgrind", 
		   signame(signo));
   }
   return VG_(mk_SysRes_Error)( VKI_EINVAL );

  bad_sigkill_or_sigstop:
   if (VG_(showing_core_errors)()) {
      VG_(message)(Vg_UserMsg,
		   "Warning: ignored attempt to set %s handler in sigaction();",
		   signame(signo));
      VG_(message)(Vg_UserMsg,
		   "         the %s signal is uncatchable", 
		   signame(signo));
   }
   return VG_(mk_SysRes_Error)( VKI_EINVAL );
}


static
void do_sigprocmask_bitops ( Int vki_how, 
			     vki_sigset_t* orig_set,
			     vki_sigset_t* modifier )
{
   switch (vki_how) {
      case VKI_SIG_BLOCK: 
         VG_(sigaddset_from_set)( orig_set, modifier );
         break;
      case VKI_SIG_UNBLOCK:
         VG_(sigdelset_from_set)( orig_set, modifier );
         break;
      case VKI_SIG_SETMASK:
         *orig_set = *modifier;
         break;
      default:
         VG_(core_panic)("do_sigprocmask_bitops");
	 break;
   }
}

static
const Char *format_sigset ( const vki_sigset_t* set )
{
   static Char buf[128];
   int w;

   VG_(strcpy)(buf, "");

   for (w = _VKI_NSIG_WORDS - 1; w >= 0; w--)
   {
#if _VKI_NSIG_BPW == 32
      VG_(sprintf)(buf + VG_(strlen)(buf), "%08lx", set ? set->sig[w] : 0);
#elif _VKI_NSIG_BPW == 64
      VG_(sprintf)(buf + VG_(strlen)(buf), "%16lx", set ? set->sig[w] : 0);
#else
#error "Unsupported value for _VKI_NSIG_BPW"
#endif
   }

   return buf;
}

/* 
   This updates the thread's signal mask.  There's no such thing as a
   process-wide signal mask.

   Note that the thread signal masks are an implicit part of SCSS,
   which is why this routine is allowed to mess with them.  
*/
static
void do_setmask ( ThreadId tid,
                  Int how,
                  vki_sigset_t* newset,
		  vki_sigset_t* oldset )
{
   if (VG_(clo_trace_signals))
      VG_(message)(Vg_DebugExtraMsg, 
		   "do_setmask: tid = %d how = %d (%s), set = %p %s", 
		   tid, how,
		   how==VKI_SIG_BLOCK ? "SIG_BLOCK" : (
		      how==VKI_SIG_UNBLOCK ? "SIG_UNBLOCK" : (
			 how==VKI_SIG_SETMASK ? "SIG_SETMASK" : "???")),
		   newset, format_sigset(newset));

   /* Just do this thread. */
   vg_assert(VG_(is_valid_tid)(tid));
   if (oldset) {
      *oldset = VG_(threads)[tid].sig_mask;
      if (VG_(clo_trace_signals))
	      VG_(message)(Vg_DebugExtraMsg, 
			   "\toldset=%p %s",
			   oldset, format_sigset(oldset));
   }
   if (newset) {
      do_sigprocmask_bitops (how, &VG_(threads)[tid].sig_mask, newset );
      VG_(sigdelset)(&VG_(threads)[tid].sig_mask, VKI_SIGKILL);
      VG_(sigdelset)(&VG_(threads)[tid].sig_mask, VKI_SIGSTOP);
      VG_(threads)[tid].tmp_sig_mask = VG_(threads)[tid].sig_mask;
   }
}


SysRes VG_(do_sys_sigprocmask) ( ThreadId tid,
                                 Int how, 
                                 vki_sigset_t* set,
                                 vki_sigset_t* oldset )
{
   switch(how) {
   case VKI_SIG_BLOCK:
   case VKI_SIG_UNBLOCK:
   case VKI_SIG_SETMASK:
      vg_assert(VG_(is_valid_tid)(tid));
      do_setmask ( tid, how, set, oldset );
      return VG_(mk_SysRes_Success)( 0 );

   default:
      VG_(message)(Vg_DebugMsg, 
                  "sigprocmask: unknown 'how' field %d", how);
      return VG_(mk_SysRes_Error)( VKI_EINVAL );
   }
}


/* ---------------------------------------------------------------------
   LOW LEVEL STUFF TO DO WITH SIGNALS: IMPLEMENTATION
   ------------------------------------------------------------------ */

/* ---------------------------------------------------------------------
   Handy utilities to block/restore all host signals.
   ------------------------------------------------------------------ */

/* Block all host signals, dumping the old mask in *saved_mask. */
static void block_all_host_signals ( /* OUT */ vki_sigset_t* saved_mask )
{
   Int           ret;
   vki_sigset_t block_procmask;
   VG_(sigfillset)(&block_procmask);
   ret = VG_(sigprocmask)
            (VKI_SIG_SETMASK, &block_procmask, saved_mask);
   vg_assert(ret == 0);
}

/* Restore the blocking mask using the supplied saved one. */
static void restore_all_host_signals ( /* IN */ vki_sigset_t* saved_mask )
{
   Int ret;
   ret = VG_(sigprocmask)(VKI_SIG_SETMASK, saved_mask, NULL);
   vg_assert(ret == 0);
}

void VG_(clear_out_queued_signals)( ThreadId tid, vki_sigset_t* saved_mask )
{
   block_all_host_signals(saved_mask);
   if (VG_(threads)[tid].sig_queue != NULL) {
      VG_(arena_free)(VG_AR_CORE, VG_(threads)[tid].sig_queue);
      VG_(threads)[tid].sig_queue = NULL;
   }
   restore_all_host_signals(saved_mask);
}

/* ---------------------------------------------------------------------
   The signal simulation proper.  A simplified version of what the 
   Linux kernel does.
   ------------------------------------------------------------------ */

/* Set up a stack frame (VgSigContext) for the client's signal
   handler. */
static
void push_signal_frame ( ThreadId tid, const vki_siginfo_t *siginfo )
{
   Addr         esp_top_of_frame;
   ThreadState* tst;
   Int		sigNo = siginfo->si_signo;

   vg_assert(sigNo >= 1 && sigNo <= VG_(max_signal));
   vg_assert(VG_(is_valid_tid)(tid));
   tst = & VG_(threads)[tid];

   if (VG_(clo_trace_signals))
      VG_(message)(Vg_DebugMsg, 
         "push_signal_frame (thread %d): signal %d", tid, sigNo);

   if (/* this signal asked to run on an alt stack */
       (scss.scss_per_sig[sigNo].scss_flags & VKI_SA_ONSTACK )
       && /* there is a defined and enabled alt stack, which we're not
             already using.  Logic from get_sigframe in
             arch/i386/kernel/signal.c. */
          sas_ss_flags(tid, VG_(get_SP)(tid)) == 0
      ) {
      esp_top_of_frame 
         = (Addr)(tst->altstack.ss_sp) + tst->altstack.ss_size;
      if (VG_(clo_trace_signals))
         VG_(message)(Vg_DebugMsg,
		      "delivering signal %d (%s) to thread %d: on ALT STACK (%p-%p; %d bytes)", 
		      sigNo, signame(sigNo), tid, 
		      tst->altstack.ss_sp,
		      (UChar *)tst->altstack.ss_sp + tst->altstack.ss_size,
		      tst->altstack.ss_size );

      /* Signal delivery to tools */
      VG_TRACK( pre_deliver_signal, tid, sigNo, /*alt_stack*/True );
      
   } else {
      esp_top_of_frame = VG_(get_SP)(tid) - VG_STACK_REDZONE_SZB;

      /* Signal delivery to tools */
      VG_TRACK( pre_deliver_signal, tid, sigNo, /*alt_stack*/False );
   }

   vg_assert(scss.scss_per_sig[sigNo].scss_handler != VKI_SIG_IGN);
   vg_assert(scss.scss_per_sig[sigNo].scss_handler != VKI_SIG_DFL);

   /* This may fail if the client stack is busted; if that happens,
      the whole process will exit rather than simply calling the
      signal handler. */
   VG_(sigframe_create) (tid, esp_top_of_frame, siginfo,
                         scss.scss_per_sig[sigNo].scss_handler,
                         scss.scss_per_sig[sigNo].scss_flags,
                         &tst->sig_mask,
                         scss.scss_per_sig[sigNo].scss_restorer);
}


static const Char *signame(Int sigNo)
{
   static Char buf[10];

   switch(sigNo) {
#define S(x)	case VKI_##x: return #x
      S(SIGHUP);
      S(SIGINT);
      S(SIGQUIT);
      S(SIGILL);
      S(SIGTRAP);
      S(SIGABRT);
      S(SIGBUS);
      S(SIGFPE);
      S(SIGKILL);
      S(SIGUSR1);
      S(SIGUSR2);
      S(SIGSEGV);
      S(SIGPIPE);
      S(SIGALRM);
      S(SIGTERM);
      S(SIGSTKFLT);
      S(SIGCHLD);
      S(SIGCONT);
      S(SIGSTOP);
      S(SIGTSTP);
      S(SIGTTIN);
      S(SIGTTOU);
      S(SIGURG);
      S(SIGXCPU);
      S(SIGXFSZ);
      S(SIGVTALRM);
      S(SIGPROF);
      S(SIGWINCH);
      S(SIGIO);
      S(SIGPWR);
      S(SIGUNUSED);
#undef S

   case VKI_SIGRTMIN ... VKI_SIGRTMAX:
      VG_(sprintf)(buf, "SIGRT%d", sigNo-VKI_SIGRTMIN);
      return buf;

   default:
      VG_(sprintf)(buf, "SIG%d", sigNo);
      return buf;
   }
}

/* Hit ourselves with a signal using the default handler */
void VG_(kill_self)(Int sigNo)
{
   vki_sigset_t	        mask, origmask;
   struct vki_sigaction sa, origsa;   

   sa.ksa_handler = VKI_SIG_DFL;
   sa.sa_flags = 0;
   sa.sa_restorer = 0;
   VG_(sigemptyset)(&sa.sa_mask);
      
   VG_(sigaction)(sigNo, &sa, &origsa);

   VG_(sigemptyset)(&mask);
   VG_(sigaddset)(&mask, sigNo);
   VG_(sigprocmask)(VKI_SIG_UNBLOCK, &mask, &origmask);

   VG_(kill)(VG_(getpid)(), sigNo);

   VG_(sigaction)(sigNo, &origsa, NULL);
   VG_(sigprocmask)(VKI_SIG_SETMASK, &origmask, NULL);
}

/* 
   Perform the default action of a signal.  If the signal is fatal, it
   marks all threads as needing to exit, but it doesn't actually kill
   the process or thread.

   If we're not being quiet, then print out some more detail about
   fatal signals (esp. core dumping signals).
 */
static void default_action(const vki_siginfo_t *info, ThreadId tid)
{
   Int  sigNo     = info->si_signo;
   Bool terminate = False;	/* kills process         */
   Bool core      = False;	/* kills process w/ core */
   struct vki_rlimit corelim;
   Bool could_core;

   vg_assert(VG_(is_running_thread)(tid));
   
   switch(sigNo) {
   case VKI_SIGQUIT:	/* core */
   case VKI_SIGILL:	/* core */
   case VKI_SIGABRT:	/* core */
   case VKI_SIGFPE:	/* core */
   case VKI_SIGSEGV:	/* core */
   case VKI_SIGBUS:	/* core */
   case VKI_SIGTRAP:	/* core */
   case VKI_SIGXCPU:	/* core */
   case VKI_SIGXFSZ:	/* core */
      terminate = True;
      core = True;
      break;

   case VKI_SIGHUP:	/* term */
   case VKI_SIGINT:	/* term */
   case VKI_SIGKILL:	/* term - we won't see this */
   case VKI_SIGPIPE:	/* term */
   case VKI_SIGALRM:	/* term */
   case VKI_SIGTERM:	/* term */
   case VKI_SIGUSR1:	/* term */
   case VKI_SIGUSR2:	/* term */
   case VKI_SIGIO:	/* term */
   case VKI_SIGPWR:	/* term */
   case VKI_SIGSYS:	/* term */
   case VKI_SIGPROF:	/* term */
   case VKI_SIGVTALRM:	/* term */
   case VKI_SIGRTMIN ... VKI_SIGRTMAX: /* term */
      terminate = True;
      break;
   }

   vg_assert(!core || (core && terminate));

   if (VG_(clo_trace_signals))
      VG_(message)(Vg_DebugMsg, "delivering %d (code %d) to default handler; action: %s%s",
		   sigNo, info->si_code, terminate ? "terminate" : "ignore", core ? "+core" : "");

   if (!terminate)
      return;			/* nothing to do */

   could_core = core;

   if (core) {
      /* If they set the core-size limit to zero, don't generate a
	 core file */
	 
      VG_(getrlimit)(VKI_RLIMIT_CORE, &corelim);

      if (corelim.rlim_cur == 0)
	 core = False;
   }

   if (VG_(clo_verbosity) > 1 || (could_core && info->si_code > VKI_SI_USER)) {
      VG_(message)(Vg_UserMsg, "");
      VG_(message)(Vg_UserMsg, 
                   "Process terminating with default action of signal %d (%s)%s", 
		   sigNo, signame(sigNo), core ? ": dumping core" : "");

      /* Be helpful - decode some more details about this fault */
      if (info->si_code > VKI_SI_USER) {
	 const Char *event = NULL;
	 Bool haveaddr = True;

	 switch(sigNo) {
	 case VKI_SIGSEGV:
	    switch(info->si_code) {
	    case VKI_SEGV_MAPERR: event = "Access not within mapped region"; break;
	    case VKI_SEGV_ACCERR: event = "Bad permissions for mapped region"; break;
	    case 128:
	       /* General Protection Fault: The CPU/kernel
		  isn't telling us anything useful, but this
		  is commonly the result of exceeding a
		  segment limit. */
	       event = "General Protection Fault"; 
	       haveaddr = False;
	       break;
	    }
#if 0
            {
              HChar buf[110];
              VG_(am_show_nsegments)(0,"post segfault");
              VG_(sprintf)(buf, "/bin/cat /proc/%d/maps", VG_(getpid)());
              VG_(system)(buf);
            }
#endif
	    break;

	 case VKI_SIGILL:
	    switch(info->si_code) {
	    case VKI_ILL_ILLOPC: event = "Illegal opcode"; break;
	    case VKI_ILL_ILLOPN: event = "Illegal operand"; break;
	    case VKI_ILL_ILLADR: event = "Illegal addressing mode"; break;
	    case VKI_ILL_ILLTRP: event = "Illegal trap"; break;
	    case VKI_ILL_PRVOPC: event = "Privileged opcode"; break;
	    case VKI_ILL_PRVREG: event = "Privileged register"; break;
	    case VKI_ILL_COPROC: event = "Coprocessor error"; break;
	    case VKI_ILL_BADSTK: event = "Internal stack error"; break;
	    }
	    break;

	 case VKI_SIGFPE:
	    switch (info->si_code) {
	    case VKI_FPE_INTDIV: event = "Integer divide by zero"; break;
	    case VKI_FPE_INTOVF: event = "Integer overflow"; break;
	    case VKI_FPE_FLTDIV: event = "FP divide by zero"; break;
	    case VKI_FPE_FLTOVF: event = "FP overflow"; break;
	    case VKI_FPE_FLTUND: event = "FP underflow"; break;
	    case VKI_FPE_FLTRES: event = "FP inexact"; break;
	    case VKI_FPE_FLTINV: event = "FP invalid operation"; break;
	    case VKI_FPE_FLTSUB: event = "FP subscript out of range"; break;
	    }
	    break;

	 case VKI_SIGBUS:
	    switch (info->si_code) {
	    case VKI_BUS_ADRALN: event = "Invalid address alignment"; break;
	    case VKI_BUS_ADRERR: event = "Non-existent physical address"; break;
	    case VKI_BUS_OBJERR: event = "Hardware error"; break;
	    }
	    break;
	 }

	 if (event != NULL) {
	    if (haveaddr)
	       VG_(message)(Vg_UserMsg, " %s at address %p", 
			    event, info->_sifields._sigfault._addr);
	    else
	       VG_(message)(Vg_UserMsg, " %s", event);
	 }
      }

      if (tid != VG_INVALID_THREADID) {
         VG_(get_and_pp_StackTrace)(tid, VG_(clo_backtrace_size));
      }
   }

   if (VG_(is_action_requested)( "Attach to debugger", & VG_(clo_db_attach) )) {
      VG_(start_debugger)( tid );
   }

   if (core) {
      const static struct vki_rlimit zero = { 0, 0 };

      VG_(make_coredump)(tid, info, corelim.rlim_cur);

      /* Make sure we don't get a confusing kernel-generated
	 coredump when we finally exit */
      VG_(setrlimit)(VKI_RLIMIT_CORE, &zero);
   }

   /* stash fatal signal in main thread */
   // what's this for?
   //VG_(threads)[VG_(master_tid)].os_state.fatalsig = sigNo;

   /* everyone dies */
   VG_(nuke_all_threads_except)(tid, VgSrc_FatalSig);
   VG_(threads)[tid].exitreason = VgSrc_FatalSig;
   VG_(threads)[tid].os_state.fatalsig = sigNo;
}

/* 
   This does the business of delivering a signal to a thread.  It may
   be called from either a real signal handler, or from normal code to
   cause the thread to enter the signal handler.

   This updates the thread state, but it does not set it to be
   Runnable.
*/
static void deliver_signal ( ThreadId tid, const vki_siginfo_t *info )
{
   Int			sigNo = info->si_signo;
   SCSS_Per_Signal	*handler = &scss.scss_per_sig[sigNo];
   void			*handler_fn;
   ThreadState		*tst = VG_(get_ThreadState)(tid);

   if (VG_(clo_trace_signals))
      VG_(message)(Vg_DebugMsg,"delivering signal %d (%s):%d to thread %d", 
		   sigNo, signame(sigNo), info->si_code, tid );

   if (sigNo == VG_SIGVGKILL) {
      /* If this is a SIGVGKILL, we're expecting it to interrupt any
	 blocked syscall.  It doesn't matter whether the VCPU state is
	 set to restart or not, because we don't expect it will
	 execute any more client instructions. */
      vg_assert(VG_(is_exiting)(tid));
      return;
   }

   /* If the client specifies SIG_IGN, treat it as SIG_DFL.

      If deliver_signal() is being called on a thread, we want
      the signal to get through no matter what; if they're ignoring
      it, then we do this override (this is so we can send it SIGSEGV,
      etc). */
   handler_fn = handler->scss_handler;
   if (handler_fn == VKI_SIG_IGN) 
      handler_fn = VKI_SIG_DFL;

   vg_assert(handler_fn != VKI_SIG_IGN);

   if (handler_fn == VKI_SIG_DFL) {
      default_action(info, tid);
   } else {
      /* Create a signal delivery frame, and set the client's %ESP and
	 %EIP so that when execution continues, we will enter the
	 signal handler with the frame on top of the client's stack,
	 as it expects.

	 Signal delivery can fail if the client stack is too small or
	 missing, and we can't push the frame.  If that happens,
	 push_signal_frame will cause the whole process to exit when
	 we next hit the scheduler.
      */
      vg_assert(VG_(is_valid_tid)(tid));

      push_signal_frame ( tid, info );

      if (handler->scss_flags & VKI_SA_ONESHOT) {
	 /* Do the ONESHOT thing. */
	 handler->scss_handler = VKI_SIG_DFL;

	 handle_SCSS_change( False /* lazy update */ );
      }

      /* At this point:
	 tst->sig_mask is the current signal mask
	 tst->tmp_sig_mask is the same as sig_mask, unless we're in sigsuspend
	 handler->scss_mask is the mask set by the handler

	 Handler gets a mask of tmp_sig_mask|handler_mask|signo
       */
      tst->sig_mask = tst->tmp_sig_mask;
      if (!(handler->scss_flags & VKI_SA_NOMASK)) {
	 VG_(sigaddset_from_set)(&tst->sig_mask, &handler->scss_mask);
	 VG_(sigaddset)(&tst->sig_mask, sigNo);

	 tst->tmp_sig_mask = tst->sig_mask;
      }
   }

   /* Thread state is ready to go - just add Runnable */
}

static void resume_scheduler(ThreadId tid)
{
   ThreadState *tst = VG_(get_ThreadState)(tid);

   vg_assert(tst->os_state.lwpid == VG_(gettid)());

   if (tst->sched_jmpbuf_valid) {
      /* Can't continue; must longjmp back to the scheduler and thus
         enter the sighandler immediately. */
      __builtin_longjmp(tst->sched_jmpbuf, True);
   }
}

static void synth_fault_common(ThreadId tid, Addr addr, Int si_code)
{
   vki_siginfo_t info;

   vg_assert(VG_(threads)[tid].status == VgTs_Runnable);

   info.si_signo = VKI_SIGSEGV;
   info.si_code = si_code;
   info._sifields._sigfault._addr = (void*)addr;

   /* If they're trying to block the signal, force it to be delivered */
   if (VG_(sigismember)(&VG_(threads)[tid].sig_mask, VKI_SIGSEGV))
      VG_(set_default_handler)(VKI_SIGSEGV);

   deliver_signal(tid, &info);
}

// Synthesize a fault where the address is OK, but the page
// permissions are bad.
void VG_(synth_fault_perms)(ThreadId tid, Addr addr)
{
   synth_fault_common(tid, addr, 2);
}

// Synthesize a fault where the address there's nothing mapped at the address.
void VG_(synth_fault_mapping)(ThreadId tid, Addr addr)
{
   synth_fault_common(tid, addr, 1);
}

// Synthesize a misc memory fault.
void VG_(synth_fault)(ThreadId tid)
{
   synth_fault_common(tid, 0, 0x80);
}

// Synthesise a SIGILL.
void VG_(synth_sigill)(ThreadId tid, Addr addr)
{
   vki_siginfo_t info;

   vg_assert(VG_(threads)[tid].status == VgTs_Runnable);

   info.si_signo = VKI_SIGILL;
   info.si_code = VKI_ILL_ILLOPC; /* jrs: no idea what this should be */
   info._sifields._sigfault._addr = (void*)addr;

   resume_scheduler(tid);
   deliver_signal(tid, &info);
}

// Synthesise a SIGTRAP.
void VG_(synth_sigtrap)(ThreadId tid)
{
   vki_siginfo_t info;

   vg_assert(VG_(threads)[tid].status == VgTs_Runnable);

   info.si_signo = VKI_SIGTRAP;
   info.si_code = VKI_TRAP_TRACE; /* jrs: no idea what this should be */

   resume_scheduler(tid);
   deliver_signal(tid, &info);
}

/* Make a signal pending for a thread, for later delivery.
   VG_(poll_signals) will arrange for it to be delivered at the right
   time. 

   tid==0 means add it to the process-wide queue, and not sent it to a
   specific thread.
*/
static 
void queue_signal(ThreadId tid, const vki_siginfo_t *si)
{
   ThreadState *tst;
   SigQueue *sq;
   vki_sigset_t savedmask;

   tst = VG_(get_ThreadState)(tid);

   /* Protect the signal queue against async deliveries */
   block_all_host_signals(&savedmask);

   if (tst->sig_queue == NULL) {
      tst->sig_queue = VG_(arena_malloc)(VG_AR_CORE, sizeof(*tst->sig_queue));
      VG_(memset)(tst->sig_queue, 0, sizeof(*tst->sig_queue));
   }
   sq = tst->sig_queue;

   if (VG_(clo_trace_signals))
      VG_(message)(Vg_DebugMsg, "Queueing signal %d (idx %d) to thread %d",
		   si->si_signo, sq->next, tid);

   /* Add signal to the queue.  If the queue gets overrun, then old
      queued signals may get lost. 

      XXX We should also keep a sigset of pending signals, so that at
      least a non-siginfo signal gets deliviered.
   */
   if (sq->sigs[sq->next].si_signo != 0)
      VG_(message)(Vg_UserMsg, "Signal %d being dropped from thread %d's queue",
		   sq->sigs[sq->next].si_signo, tid);

   sq->sigs[sq->next] = *si;
   sq->next = (sq->next+1) % N_QUEUED_SIGNALS;

   restore_all_host_signals(&savedmask);
}

/*
   Returns the next queued signal for thread tid which is in "set".
   tid==0 means process-wide signal.  Set si_signo to 0 when the
   signal has been delivered.

   Must be called with all signals blocked, to protect against async
   deliveries.
*/
static vki_siginfo_t *next_queued(ThreadId tid, const vki_sigset_t *set)
{
   ThreadState *tst = VG_(get_ThreadState)(tid);
   SigQueue *sq;
   Int idx;
   vki_siginfo_t *ret = NULL;

   sq = tst->sig_queue;
   if (sq == NULL)
      goto out;
   
   idx = sq->next;
   do {
      if (0)
	 VG_(printf)("idx=%d si_signo=%d inset=%d\n", idx,
		     sq->sigs[idx].si_signo, VG_(sigismember)(set, sq->sigs[idx].si_signo));

      if (sq->sigs[idx].si_signo != 0 && VG_(sigismember)(set, sq->sigs[idx].si_signo)) {
	 if (VG_(clo_trace_signals))
	    VG_(message)(Vg_DebugMsg, "Returning queued signal %d (idx %d) for thread %d",
			 sq->sigs[idx].si_signo, idx, tid);
	 ret = &sq->sigs[idx];
	 goto out;
      }

      idx = (idx + 1) % N_QUEUED_SIGNALS;
   } while(idx != sq->next);
  out:   
   return ret;   
}

/* 
   Receive an async signal from the kernel.

   This should only happen when the thread is blocked in a syscall,
   since that's the only time this set of signals is unblocked.
*/
static 
void async_signalhandler ( Int sigNo, vki_siginfo_t *info, struct vki_ucontext *uc )
{
   ThreadId tid = VG_(get_lwp_tid)(VG_(gettid)());
   ThreadState *tst = VG_(get_ThreadState)(tid);

   vg_assert(tst->status == VgTs_WaitSys);

#ifdef VGO_linux
   /* The linux kernel uses the top 16 bits of si_code for it's own
      use and only exports the bottom 16 bits to user space - at least
      that is the theory, but it turns out that there are some kernels
      around that forget to mask out the top 16 bits so we do it here.

      The kernel treats the bottom 16 bits as signed and (when it does
      mask them off) sign extends them when exporting to user space so
      we do the same thing here. */
   info->si_code = (Short)info->si_code;
#endif

   /* The thread isn't currently running, make it so before going on */
   VG_(set_running)(tid);

   if (VG_(clo_trace_signals))
      VG_(message)(Vg_DebugMsg, "Async handler got signal %d for tid %d info %d",
		   sigNo, tid, info->si_code);

   /* Update thread state properly */
   VG_(fixup_guest_state_after_syscall_interrupted)(
      tid, 
      VG_UCONTEXT_INSTR_PTR(uc), 
      VG_UCONTEXT_SYSCALL_NUM(uc), 
      VG_UCONTEXT_SYSCALL_SYSRES(uc),  
      !!(scss.scss_per_sig[sigNo].scss_flags & VKI_SA_RESTART)
   );

   /* Set up the thread's state to deliver a signal */
   if (!is_sig_ign(info->si_signo))
      deliver_signal(tid, info);

   /* longjmp back to the thread's main loop to start executing the
      handler. */
   resume_scheduler(tid);

   VG_(core_panic)("async_signalhandler: got unexpected signal while outside of scheduler");
}

/* Extend the stack to cover addr.  maxsize is the limit the stack can grow to.

   Returns True on success, False on failure.

   Succeeds without doing anything if addr is already within a segment.

   Failure could be caused by:
   - addr not below a growable segment
   - new stack size would exceed maxsize
   - mmap failed for some other reason
 */
Bool VG_(extend_stack)(Addr addr, UInt maxsize)
{
   SizeT udelta;

   /* Find the next Segment above addr */
   NSegment* seg      = VG_(am_find_nsegment)(addr);
   NSegment* seg_next = seg ? VG_(am_next_nsegment)( seg, True/*fwds*/ )
                            : NULL;

   if (seg && seg->kind == SkAnonC)
      /* addr is already mapped.  Nothing to do. */
      return True;

   /* Check that the requested new base is in a shrink-down
      reservation section which abuts an anonymous mapping that
      belongs to the client. */
   if ( ! (seg
           && seg->kind == SkResvn
           && seg->smode == SmUpper
           && seg_next
           && seg_next->kind == SkAnonC
           && seg->end+1 == seg_next->start))
      return False;

   udelta = VG_PGROUNDUP(seg_next->start - addr);
   VG_(debugLog)(1, "signals", 
                    "extending a stack base 0x%llx down by %lld\n",
                    (ULong)seg_next->start, (ULong)udelta);
   if (! VG_(am_extend_into_adjacent_reservation_client)
            ( seg_next, -(SSizeT)udelta )) {
      VG_(debugLog)(1, "signals", "extending a stack base: FAILED\n");
      return False;
   }

   /* When we change the main stack, we have to let the stack handling
      code know about it. */
   VG_(change_stack)(VG_(clstk_id), addr, VG_(clstk_end));

   if (VG_(clo_sanity_level) > 2)
      VG_(sanity_check_general)(False);

   return True;
}

static void (*fault_catcher)(Int sig, Addr addr);

void VG_(set_fault_catcher)(void (*catcher)(Int, Addr))
{
   vg_assert2(NULL == catcher || NULL == fault_catcher,
              "Fault catcher is already registered");

   fault_catcher = catcher;
}


/* 
   Receive a sync signal from the host. 
*/
static
void sync_signalhandler ( Int sigNo, vki_siginfo_t *info, struct vki_ucontext *uc )
{
   ThreadId tid = VG_(get_lwp_tid)(VG_(gettid)());

   vg_assert(info != NULL);
   vg_assert(info->si_signo == sigNo);
   vg_assert(sigNo == VKI_SIGSEGV ||
	     sigNo == VKI_SIGBUS  ||
	     sigNo == VKI_SIGFPE  ||
	     sigNo == VKI_SIGILL  ||
	     sigNo == VKI_SIGTRAP);

#ifdef VGO_linux
   /* The linux kernel uses the top 16 bits of si_code for it's own
      use and only exports the bottom 16 bits to user space - at least
      that is the theory, but it turns out that there are some kernels
      around that forget to mask out the top 16 bits so we do it here.

      The kernel treats the bottom 16 bits as signed and (when it does
      mask them off) sign extends them when exporting to user space so
      we do the same thing here. */
   info->si_code = (Short)info->si_code;
#endif

   if (info->si_code <= VKI_SI_USER) {
      /* If some user-process sent us one of these signals (ie,
	 they're not the result of a faulting instruction), then treat
	 it as an async signal.  This is tricky because we could get
	 this almost anywhere:
	  - while generated client code
	    Action: queue signal and return
	  - while running Valgrind code
	    Action: queue signal and return
	  - while blocked in a syscall
	    Action: make thread runnable, queue signal, resume scheduler
      */
      if (VG_(threads)[tid].status == VgTs_WaitSys) {
	 /* Since this signal interrupted a syscall, it means the
	    client's signal mask was applied, so we can't get here
	    unless the client wants this signal right now.  This means
	    we can simply use the async_signalhandler. */
	 async_signalhandler(sigNo, info, uc);
	 VG_(core_panic)("async_signalhandler returned!?\n");
      }

      if (info->_sifields._kill._pid == 0) {
	 /* There's a per-user limit of pending siginfo signals.  If
	    you exceed this, by having more than that number of
	    pending signals with siginfo, then new signals are
	    delivered without siginfo.  This condition can be caused
	    by any unrelated program you're running at the same time
	    as Valgrind, if it has a large number of pending siginfo
	    signals which it isn't taking delivery of.

	    Since we depend on siginfo to work out why we were sent a
	    signal and what we should do about it, we really can't
	    continue unless we get it. */
	 VG_(message)(Vg_UserMsg, "Signal %d (%s) appears to have lost its siginfo; I can't go on.",
		      sigNo, signame(sigNo));
	 VG_(message)(Vg_UserMsg, "  This may be because one of your programs has consumed your");
	 VG_(message)(Vg_UserMsg, "  ration of siginfo structures.");
         VG_(printf)(
"  For more information, see:\n"
"    http://kerneltrap.org/mailarchive/1/message/25599/thread\n"
"  Basically, some program on your system is building up a large queue of\n"
"  pending signals, and this causes the siginfo data for other signals to\n"
"  be dropped because it's exceeding a system limit.  However, Valgrind\n"
"  absolutely needs siginfo for SIGSEGV.  A workaround is to track down the\n"
"  offending program and avoid running it while using Valgrind, but there\n"
"  is no easy way to do this.  Apparently the problem was fixed in kernel\n"
"  2.6.12.\n");

	 /* It's a fatal signal, so we force the default handler. */
	 VG_(set_default_handler)(sigNo);
	 deliver_signal(tid, info);
	 resume_scheduler(tid);
	 VG_(exit)(99);		/* If we can't resume, then just exit */
      }

      if (VG_(clo_trace_signals))
	 VG_(message)(Vg_DebugMsg, "Routing user-sent sync signal %d via queue",
		      sigNo);

      /* Since every thread has these signals unblocked, we can't rely
	 on the kernel to route them properly, so we need to queue
	 them manually. */
      if (info->si_code == VKI_SI_TKILL)
	 queue_signal(tid, info); /* directed to us specifically */
      else
	 queue_signal(0, info);	/* shared pending */

      return;
   } 

   if (VG_(clo_trace_signals)) {
      VG_(message)(Vg_DebugMsg, "signal %d arrived ... si_code=%d, "
                                "EIP=%p, eip=%p",
                   sigNo, info->si_code, VG_(get_IP)(tid), 
		   VG_UCONTEXT_INSTR_PTR(uc) );
   }
   vg_assert(sigNo >= 1 && sigNo <= VG_(max_signal));

   /* Special fault-handling case. We can now get signals which can
      act upon and immediately restart the faulting instruction.
    */
   if (info->si_signo == VKI_SIGSEGV) {
      Addr fault = (Addr)info->_sifields._sigfault._addr;
      Addr esp   =  VG_(get_SP)(tid);
      NSegment* seg      = VG_(am_find_nsegment)(fault);
      NSegment* seg_next = seg ? VG_(am_next_nsegment)( seg, True/*fwds*/ )
                               : NULL;

      if (VG_(clo_trace_signals)) {
	 if (seg == NULL)
	    VG_(message)(Vg_DebugMsg,
			 "SIGSEGV: si_code=%d faultaddr=%p tid=%d ESP=%p "
                         "seg=NULL",
			 info->si_code, fault, tid, esp);
	 else
	    VG_(message)(Vg_DebugMsg,
			 "SIGSEGV: si_code=%d faultaddr=%p tid=%d ESP=%p "
                          "seg=%p-%p",
			 info->si_code, fault, tid, esp, seg->start, seg->end);
      }
      if (info->si_code == VKI_SEGV_MAPERR
          && seg
          && seg->kind == SkResvn
          && seg->smode == SmUpper
          && seg_next
          && seg_next->kind == SkAnonC
          && seg->end+1 == seg_next->start
	  && fault >= (esp - VG_STACK_REDZONE_SZB)) {
	 /* If the fault address is above esp but below the current known
	    stack segment base, and it was a fault because there was
	    nothing mapped there (as opposed to a permissions fault),
	    then extend the stack segment. 
	 */
         Addr base = VG_PGROUNDDN(esp - VG_STACK_REDZONE_SZB);
	 if (VG_(extend_stack)(base, VG_(threads)[tid].client_stack_szB)) {
	    if (VG_(clo_trace_signals))
	       VG_(message)(Vg_DebugMsg, 
			    "       -> extended stack base to %p", 
                            VG_PGROUNDDN(fault));
            return; // extension succeeded, restart host (hence guest)
                    // instruction
	 } else
	    VG_(message)(Vg_UserMsg, 
                         "Stack overflow in thread %d: can't grow stack to %p", 
			 tid, fault);
      }
      /* Fall into normal signal handling for all other cases */
   }

   /* OK, this is a signal we really have to deal with.  If it came
      from the client's code, then we can jump back into the scheduler
      and have it delivered.  Otherwise it's a Valgrind bug. */
   {   
      ThreadState *tst = VG_(get_ThreadState)(VG_(get_lwp_tid)(VG_(gettid)()));

      if (VG_(sigismember)(&tst->sig_mask, sigNo)) {
	 /* signal is blocked, but they're not allowed to block faults */
	 VG_(set_default_handler)(sigNo);
      }

      if (VG_(in_generated_code)) {
	 /* Can't continue; must longjmp back to the scheduler and thus
	    enter the sighandler immediately. */
	 deliver_signal(tid, info);
	 resume_scheduler(tid);
      }

      /* Check to see if someone is interested in faults. */
      if (fault_catcher) {
	 (*fault_catcher)(sigNo, (Addr)info->_sifields._sigfault._addr);

	 /* If the catcher returns, then it didn't handle the fault,
	    so carry on panicing. */
      }

      /* If resume_scheduler returns or its our fault, it means we
	 don't have longjmp set up, implying that we weren't running
	 client code, and therefore it was actually generated by
	 Valgrind internally.
       */
      VG_(message)(Vg_DebugMsg, 
		   "VALGRIND INTERNAL ERROR: Valgrind received a signal %d (%s) - exiting",
		   sigNo, signame(sigNo));

      VG_(message)(Vg_DebugMsg, 
		   "si_code=%x;  Faulting address: %p;  sp: %p",
		   info->si_code, info->_sifields._sigfault._addr,
                   VG_UCONTEXT_STACK_PTR(uc));

      if (0)
	 VG_(kill_self)(sigNo);		/* generate a core dump */

      //if (tid == 0)            /* could happen after everyone has exited */
      //  tid = VG_(master_tid);
      vg_assert(tid != 0);

      VG_(core_panic_at)("Killed by fatal signal",
                         VG_UCONTEXT_INSTR_PTR(uc),
                         VG_UCONTEXT_STACK_PTR(uc),
                         VG_UCONTEXT_FRAME_PTR(uc),
                         VG_UCONTEXT_LINK_REG(uc));
   }
}


/* 
   Kill this thread.  Makes it leave any syscall it might be currently
   blocked in, and return to the scheduler.  This doesn't mark the thread
   as exiting; that's the caller's job.
 */
static void sigvgkill_handler(int signo, vki_siginfo_t *si, struct vki_ucontext *uc)
{
   ThreadId tid = VG_(get_lwp_tid)(VG_(gettid)());

   if (VG_(clo_trace_signals))
      VG_(message)(Vg_DebugMsg, "sigvgkill for lwp %d tid %d", VG_(gettid)(), tid);

   vg_assert(signo == VG_SIGVGKILL);
   vg_assert(si->si_signo == signo);
   vg_assert(VG_(threads)[tid].status == VgTs_WaitSys);

   VG_(set_running)(tid);
   VG_(post_syscall)(tid);

   resume_scheduler(tid);

   VG_(core_panic)("sigvgkill_handler couldn't return to the scheduler\n");
}

static __attribute((unused))
void pp_ksigaction ( struct vki_sigaction* sa )
{
   Int i;
   VG_(printf)("pp_ksigaction: handler %p, flags 0x%x, restorer %p\n", 
               sa->ksa_handler, (UInt)sa->sa_flags, sa->sa_restorer);
   VG_(printf)("pp_ksigaction: { ");
   for (i = 1; i <= VG_(max_signal); i++)
      if (VG_(sigismember(&(sa->sa_mask),i)))
         VG_(printf)("%d ", i);
   VG_(printf)("}\n");
}

/* 
   Force signal handler to default
 */
void VG_(set_default_handler)(Int signo)
{
   struct vki_sigaction sa;   

   sa.ksa_handler = VKI_SIG_DFL;
   sa.sa_flags = 0;
   sa.sa_restorer = 0;
   VG_(sigemptyset)(&sa.sa_mask);
      
   VG_(do_sys_sigaction)(signo, &sa, NULL);
}

/* 
   Poll for pending signals, and set the next one up for delivery.
 */
void VG_(poll_signals)(ThreadId tid)
{
   static const struct vki_timespec zero = { 0, 0 };
   vki_siginfo_t si, *sip;
   vki_sigset_t pollset;
   ThreadState *tst = VG_(get_ThreadState)(tid);
   Int i;
   vki_sigset_t saved_mask;

   /* look for all the signals this thread isn't blocking */
   for(i = 0; i < _VKI_NSIG_WORDS; i++)
      pollset.sig[i] = ~tst->sig_mask.sig[i];

   //VG_(printf)("tid %d pollset=%08x%08x\n", tid, pollset.sig[1], pollset.sig[0]);

   block_all_host_signals(&saved_mask); // protect signal queue

   /* First look for any queued pending signals */
   sip = next_queued(tid, &pollset); /* this thread */

   if (sip == NULL)
      sip = next_queued(0, &pollset); /* process-wide */

   /* If there was nothing queued, ask the kernel for a pending signal */
   if (sip == NULL && VG_(sigtimedwait)(&pollset, &si, &zero) > 0) {
      if (VG_(clo_trace_signals))
	 VG_(message)(Vg_DebugMsg, "poll_signals: got signal %d "
                                   "for thread %d", si.si_signo, tid);
      sip = &si;
   }

   if (sip != NULL) {
      /* OK, something to do; deliver it */
      if (VG_(clo_trace_signals))
	 VG_(message)(Vg_DebugMsg, "Polling found signal %d for tid %d", 
		      sip->si_signo, tid);
      if (!is_sig_ign(sip->si_signo))
	 deliver_signal(tid, sip);
      else if (VG_(clo_trace_signals))
	 VG_(message)(Vg_DebugMsg, "   signal %d ignored", sip->si_signo);
	 
      sip->si_signo = 0;	/* remove from signal queue, if that's
				   where it came from */
   }

   restore_all_host_signals(&saved_mask);
}

/* At startup, copy the process' real signal state to the SCSS.
   Whilst doing this, block all real signals.  Then calculate SKSS and
   set the kernel to that.  Also initialise DCSS. 
*/
void VG_(sigstartup_actions) ( void )
{
   Int i, ret;
   vki_sigset_t saved_procmask;
   struct vki_sigaction sa;

   /* VG_(printf)("SIGSTARTUP\n"); */
   /* Block all signals.  saved_procmask remembers the previous mask,
      which the first thread inherits.
   */
   block_all_host_signals( &saved_procmask );

   /* Copy per-signal settings to SCSS. */
   for (i = 1; i <= _VKI_NSIG; i++) {
      /* Get the old host action */
      ret = VG_(sigaction)(i, NULL, &sa);

      if (ret != 0)
	 break;

      /* Try setting it back to see if this signal is really
	 available */
      if (i >= VKI_SIGRTMIN) {
	 struct vki_sigaction tsa;

	 tsa.ksa_handler = (void *)sync_signalhandler;
	 tsa.sa_flags = VKI_SA_SIGINFO;
	 tsa.sa_restorer = 0;
	 VG_(sigfillset)(&tsa.sa_mask);

	 /* try setting it to some arbitrary handler */
	 if (VG_(sigaction)(i, &tsa, NULL) != 0) {
	    /* failed - not really usable */
	    break;
	 }

	 ret = VG_(sigaction)(i, &sa, NULL);
	 vg_assert(ret == 0);
      }

      VG_(max_signal) = i;

      if (VG_(clo_trace_signals) && VG_(clo_verbosity) > 2)
         VG_(printf)("snaffling handler 0x%x for signal %d\n", 
                     (Addr)(sa.ksa_handler), i );

      scss.scss_per_sig[i].scss_handler  = sa.ksa_handler;
      scss.scss_per_sig[i].scss_flags    = sa.sa_flags;
      scss.scss_per_sig[i].scss_mask     = sa.sa_mask;
      scss.scss_per_sig[i].scss_restorer = sa.sa_restorer;
   }

   if (VG_(clo_trace_signals))
      VG_(message)(Vg_DebugMsg, "Max kernel-supported signal is %d", VG_(max_signal));

   /* Our private internal signals are treated as ignored */
   scss.scss_per_sig[VG_SIGVGKILL].scss_handler = VKI_SIG_IGN;
   scss.scss_per_sig[VG_SIGVGKILL].scss_flags   = VKI_SA_SIGINFO;
   VG_(sigfillset)(&scss.scss_per_sig[VG_SIGVGKILL].scss_mask);

   /* Copy the process' signal mask into the root thread. */
   vg_assert(VG_(threads)[1].status == VgTs_Init);
   for (i = 2; i < VG_N_THREADS; i++)
      vg_assert(VG_(threads)[i].status == VgTs_Empty);

   VG_(threads)[1].sig_mask = saved_procmask;
   VG_(threads)[1].tmp_sig_mask = saved_procmask;

   /* Calculate SKSS and apply it.  This also sets the initial kernel
      mask we need to run with. */
   handle_SCSS_change( True /* forced update */ );

   /* Leave with all signals still blocked; the thread scheduler loop
      will set the appropriate mask at the appropriate time. */
}

/*--------------------------------------------------------------------*/
/*--- end                                                          ---*/
/*--------------------------------------------------------------------*/