summaryrefslogtreecommitdiffstats
path: root/arch/xtensa/kernel/entry.S
blob: 9e3676879168ab920696c4e0809696edcda44ffe (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
/*
 * Low-level exception handling
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2004 - 2008 by Tensilica Inc.
 * Copyright (C) 2015 Cadence Design Systems Inc.
 *
 * Chris Zankel <chris@zankel.net>
 *
 */

#include <linux/linkage.h>
#include <asm/asm-offsets.h>
#include <asm/asmmacro.h>
#include <asm/processor.h>
#include <asm/coprocessor.h>
#include <asm/thread_info.h>
#include <asm/asm-uaccess.h>
#include <asm/unistd.h>
#include <asm/ptrace.h>
#include <asm/current.h>
#include <asm/pgtable.h>
#include <asm/page.h>
#include <asm/signal.h>
#include <asm/tlbflush.h>
#include <variant/tie-asm.h>

/* Unimplemented features. */

#undef KERNEL_STACK_OVERFLOW_CHECK

/* Not well tested.
 *
 * - fast_coprocessor
 */

/*
 * Macro to find first bit set in WINDOWBASE from the left + 1
 *
 * 100....0 -> 1
 * 010....0 -> 2
 * 000....1 -> WSBITS
 */

	.macro ffs_ws bit mask

#if XCHAL_HAVE_NSA
	nsau    \bit, \mask			# 32-WSBITS ... 31 (32 iff 0)
	addi    \bit, \bit, WSBITS - 32 + 1   	# uppest bit set -> return 1
#else
	movi    \bit, WSBITS
#if WSBITS > 16
	_bltui  \mask, 0x10000, 99f
	addi    \bit, \bit, -16
	extui   \mask, \mask, 16, 16
#endif
#if WSBITS > 8
99:	_bltui  \mask, 0x100, 99f
	addi    \bit, \bit, -8
	srli    \mask, \mask, 8
#endif
99:	_bltui  \mask, 0x10, 99f
	addi    \bit, \bit, -4
	srli    \mask, \mask, 4
99:	_bltui  \mask, 0x4, 99f
	addi    \bit, \bit, -2
	srli    \mask, \mask, 2
99:	_bltui  \mask, 0x2, 99f
	addi    \bit, \bit, -1
99:

#endif
	.endm


	.macro	irq_save flags tmp
#if XTENSA_FAKE_NMI
#if defined(CONFIG_DEBUG_KERNEL) && (LOCKLEVEL | TOPLEVEL) >= XCHAL_DEBUGLEVEL
	rsr	\flags, ps
	extui	\tmp, \flags, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
	bgei	\tmp, LOCKLEVEL, 99f
	rsil	\tmp, LOCKLEVEL
99:
#else
	movi	\tmp, LOCKLEVEL
	rsr	\flags, ps
	or	\flags, \flags, \tmp
	xsr	\flags, ps
	rsync
#endif
#else
	rsil	\flags, LOCKLEVEL
#endif
	.endm

/* ----------------- DEFAULT FIRST LEVEL EXCEPTION HANDLERS ----------------- */

/*
 * First-level exception handler for user exceptions.
 * Save some special registers, extra states and all registers in the AR
 * register file that were in use in the user task, and jump to the common
 * exception code.
 * We save SAR (used to calculate WMASK), and WB and WS (we don't have to
 * save them for kernel exceptions).
 *
 * Entry condition for user_exception:
 *
 *   a0:	trashed, original value saved on stack (PT_AREG0)
 *   a1:	a1
 *   a2:	new stack pointer, original value in depc
 *   a3:	a3
 *   depc:	a2, original value saved on stack (PT_DEPC)
 *   excsave1:	dispatch table
 *
 *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
 *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
 *
 * Entry condition for _user_exception:
 *
 *   a0-a3 and depc have been saved to PT_AREG0...PT_AREG3 and PT_DEPC
 *   excsave has been restored, and
 *   stack pointer (a1) has been set.
 *
 * Note: _user_exception might be at an odd address. Don't use call0..call12
 */
	.literal_position

ENTRY(user_exception)

	/* Save a1, a2, a3, and set SP. */

	rsr	a0, depc
	s32i	a1, a2, PT_AREG1
	s32i	a0, a2, PT_AREG2
	s32i	a3, a2, PT_AREG3
	mov	a1, a2

	.globl _user_exception
_user_exception:

	/* Save SAR and turn off single stepping */

	movi	a2, 0
	wsr	a2, depc		# terminate user stack trace with 0
	rsr	a3, sar
	xsr	a2, icountlevel
	s32i	a3, a1, PT_SAR
	s32i	a2, a1, PT_ICOUNTLEVEL

#if XCHAL_HAVE_THREADPTR
	rur	a2, threadptr
	s32i	a2, a1, PT_THREADPTR
#endif

	/* Rotate ws so that the current windowbase is at bit0. */
	/* Assume ws = xxwww1yyyy. Rotate ws right, so that a2 = yyyyxxwww1 */

	rsr	a2, windowbase
	rsr	a3, windowstart
	ssr	a2
	s32i	a2, a1, PT_WINDOWBASE
	s32i	a3, a1, PT_WINDOWSTART
	slli	a2, a3, 32-WSBITS
	src	a2, a3, a2
	srli	a2, a2, 32-WSBITS
	s32i	a2, a1, PT_WMASK	# needed for restoring registers

	/* Save only live registers. */

	_bbsi.l	a2, 1, 1f
	s32i	a4, a1, PT_AREG4
	s32i	a5, a1, PT_AREG5
	s32i	a6, a1, PT_AREG6
	s32i	a7, a1, PT_AREG7
	_bbsi.l	a2, 2, 1f
	s32i	a8, a1, PT_AREG8
	s32i	a9, a1, PT_AREG9
	s32i	a10, a1, PT_AREG10
	s32i	a11, a1, PT_AREG11
	_bbsi.l	a2, 3, 1f
	s32i	a12, a1, PT_AREG12
	s32i	a13, a1, PT_AREG13
	s32i	a14, a1, PT_AREG14
	s32i	a15, a1, PT_AREG15
	_bnei	a2, 1, 1f		# only one valid frame?

	/* Only one valid frame, skip saving regs. */

	j	2f

	/* Save the remaining registers.
	 * We have to save all registers up to the first '1' from
	 * the right, except the current frame (bit 0).
	 * Assume a2 is:  001001000110001
	 * All register frames starting from the top field to the marked '1'
	 * must be saved.
	 */

1:	addi	a3, a2, -1		# eliminate '1' in bit 0: yyyyxxww0
	neg	a3, a3			# yyyyxxww0 -> YYYYXXWW1+1
	and	a3, a3, a2		# max. only one bit is set

	/* Find number of frames to save */

	ffs_ws	a0, a3			# number of frames to the '1' from left

	/* Store information into WMASK:
	 * bits 0..3: xxx1 masked lower 4 bits of the rotated windowstart,
	 * bits 4...: number of valid 4-register frames
	 */

	slli	a3, a0, 4		# number of frames to save in bits 8..4
	extui	a2, a2, 0, 4		# mask for the first 16 registers
	or	a2, a3, a2
	s32i	a2, a1, PT_WMASK	# needed when we restore the reg-file

	/* Save 4 registers at a time */

1:	rotw	-1
	s32i	a0, a5, PT_AREG_END - 16
	s32i	a1, a5, PT_AREG_END - 12
	s32i	a2, a5, PT_AREG_END - 8
	s32i	a3, a5, PT_AREG_END - 4
	addi	a0, a4, -1
	addi	a1, a5, -16
	_bnez	a0, 1b

	/* WINDOWBASE still in SAR! */

	rsr	a2, sar			# original WINDOWBASE
	movi	a3, 1
	ssl	a2
	sll	a3, a3
	wsr	a3, windowstart		# set corresponding WINDOWSTART bit
	wsr	a2, windowbase		# and WINDOWSTART
	rsync

	/* We are back to the original stack pointer (a1) */

2:	/* Now, jump to the common exception handler. */

	j	common_exception

ENDPROC(user_exception)

/*
 * First-level exit handler for kernel exceptions
 * Save special registers and the live window frame.
 * Note: Even though we changes the stack pointer, we don't have to do a
 *	 MOVSP here, as we do that when we return from the exception.
 *	 (See comment in the kernel exception exit code)
 *
 * Entry condition for kernel_exception:
 *
 *   a0:	trashed, original value saved on stack (PT_AREG0)
 *   a1:	a1
 *   a2:	new stack pointer, original in DEPC
 *   a3:	a3
 *   depc:	a2, original value saved on stack (PT_DEPC)
 *   excsave_1:	dispatch table
 *
 *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
 *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
 *
 * Entry condition for _kernel_exception:
 *
 *   a0-a3 and depc have been saved to PT_AREG0...PT_AREG3 and PT_DEPC
 *   excsave has been restored, and
 *   stack pointer (a1) has been set.
 *
 * Note: _kernel_exception might be at an odd address. Don't use call0..call12
 */

ENTRY(kernel_exception)

	/* Save a1, a2, a3, and set SP. */

	rsr	a0, depc		# get a2
	s32i	a1, a2, PT_AREG1
	s32i	a0, a2, PT_AREG2
	s32i	a3, a2, PT_AREG3
	mov	a1, a2

	.globl _kernel_exception
_kernel_exception:

	/* Save SAR and turn off single stepping */

	movi	a2, 0
	rsr	a3, sar
	xsr	a2, icountlevel
	s32i	a3, a1, PT_SAR
	s32i	a2, a1, PT_ICOUNTLEVEL

	/* Rotate ws so that the current windowbase is at bit0. */
	/* Assume ws = xxwww1yyyy. Rotate ws right, so that a2 = yyyyxxwww1 */

	rsr	a2, windowbase		# don't need to save these, we only
	rsr	a3, windowstart		# need shifted windowstart: windowmask
	ssr	a2
	slli	a2, a3, 32-WSBITS
	src	a2, a3, a2
	srli	a2, a2, 32-WSBITS
	s32i	a2, a1, PT_WMASK	# needed for kernel_exception_exit

	/* Save only the live window-frame */

	_bbsi.l	a2, 1, 1f
	s32i	a4, a1, PT_AREG4
	s32i	a5, a1, PT_AREG5
	s32i	a6, a1, PT_AREG6
	s32i	a7, a1, PT_AREG7
	_bbsi.l	a2, 2, 1f
	s32i	a8, a1, PT_AREG8
	s32i	a9, a1, PT_AREG9
	s32i	a10, a1, PT_AREG10
	s32i	a11, a1, PT_AREG11
	_bbsi.l	a2, 3, 1f
	s32i	a12, a1, PT_AREG12
	s32i	a13, a1, PT_AREG13
	s32i	a14, a1, PT_AREG14
	s32i	a15, a1, PT_AREG15

	_bnei	a2, 1, 1f

	/* Copy spill slots of a0 and a1 to imitate movsp
	 * in order to keep exception stack continuous
	 */
	l32i	a3, a1, PT_SIZE
	l32i	a0, a1, PT_SIZE + 4
	s32e	a3, a1, -16
	s32e	a0, a1, -12
1:
	l32i	a0, a1, PT_AREG0	# restore saved a0
	wsr	a0, depc

#ifdef KERNEL_STACK_OVERFLOW_CHECK

	/*  Stack overflow check, for debugging  */
	extui	a2, a1, TASK_SIZE_BITS,XX
	movi	a3, SIZE??
	_bge	a2, a3, out_of_stack_panic

#endif

/*
 * This is the common exception handler.
 * We get here from the user exception handler or simply by falling through
 * from the kernel exception handler.
 * Save the remaining special registers, switch to kernel mode, and jump
 * to the second-level exception handler.
 *
 */

common_exception:

	/* Save some registers, disable loops and clear the syscall flag. */

	rsr	a2, debugcause
	rsr	a3, epc1
	s32i	a2, a1, PT_DEBUGCAUSE
	s32i	a3, a1, PT_PC

	movi	a2, NO_SYSCALL
	rsr	a3, excvaddr
	s32i	a2, a1, PT_SYSCALL
	movi	a2, 0
	s32i	a3, a1, PT_EXCVADDR
#if XCHAL_HAVE_LOOPS
	xsr	a2, lcount
	s32i	a2, a1, PT_LCOUNT
#endif

	/* It is now save to restore the EXC_TABLE_FIXUP variable. */

	rsr	a2, exccause
	movi	a3, 0
	rsr	a0, excsave1
	s32i	a2, a1, PT_EXCCAUSE
	s32i	a3, a0, EXC_TABLE_FIXUP

	/* All unrecoverable states are saved on stack, now, and a1 is valid.
	 * Now we can allow exceptions again. In case we've got an interrupt
	 * PS.INTLEVEL is set to LOCKLEVEL disabling furhter interrupts,
	 * otherwise it's left unchanged.
	 *
	 * Set PS(EXCM = 0, UM = 0, RING = 0, OWB = 0, WOE = 1, INTLEVEL = X)
	 */

	rsr	a3, ps
	s32i	a3, a1, PT_PS		# save ps

#if XTENSA_FAKE_NMI
	/* Correct PS needs to be saved in the PT_PS:
	 * - in case of exception or level-1 interrupt it's in the PS,
	 *   and is already saved.
	 * - in case of medium level interrupt it's in the excsave2.
	 */
	movi	a0, EXCCAUSE_MAPPED_NMI
	extui	a3, a3, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
	beq	a2, a0, .Lmedium_level_irq
	bnei	a2, EXCCAUSE_LEVEL1_INTERRUPT, .Lexception
	beqz	a3, .Llevel1_irq	# level-1 IRQ sets ps.intlevel to 0

.Lmedium_level_irq:
	rsr	a0, excsave2
	s32i	a0, a1, PT_PS		# save medium-level interrupt ps
	bgei	a3, LOCKLEVEL, .Lexception

.Llevel1_irq:
	movi	a3, LOCKLEVEL

.Lexception:
	movi	a0, PS_WOE_MASK
	or	a3, a3, a0
#else
	addi	a2, a2, -EXCCAUSE_LEVEL1_INTERRUPT
	movi	a0, LOCKLEVEL
	extui	a3, a3, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
					# a3 = PS.INTLEVEL
	moveqz	a3, a0, a2		# a3 = LOCKLEVEL iff interrupt
	movi	a2, PS_WOE_MASK
	or	a3, a3, a2
	rsr	a2, exccause
#endif

	/* restore return address (or 0 if return to userspace) */
	rsr	a0, depc
	wsr	a3, ps
	rsync				# PS.WOE => rsync => overflow

	/* Save lbeg, lend */
#if XCHAL_HAVE_LOOPS
	rsr	a4, lbeg
	rsr	a3, lend
	s32i	a4, a1, PT_LBEG
	s32i	a3, a1, PT_LEND
#endif

	/* Save SCOMPARE1 */

#if XCHAL_HAVE_S32C1I
	rsr     a3, scompare1
	s32i    a3, a1, PT_SCOMPARE1
#endif

	/* Save optional registers. */

	save_xtregs_opt a1 a3 a4 a5 a6 a7 PT_XTREGS_OPT
	
	/* Go to second-level dispatcher. Set up parameters to pass to the
	 * exception handler and call the exception handler.
	 */

	rsr	a4, excsave1
	mov	a6, a1			# pass stack frame
	mov	a7, a2			# pass EXCCAUSE
	addx4	a4, a2, a4
	l32i	a4, a4, EXC_TABLE_DEFAULT		# load handler

	/* Call the second-level handler */

	callx4	a4

	/* Jump here for exception exit */
	.global common_exception_return
common_exception_return:

#if XTENSA_FAKE_NMI
	l32i	a2, a1, PT_EXCCAUSE
	movi	a3, EXCCAUSE_MAPPED_NMI
	beq	a2, a3, .LNMIexit
#endif
1:
	irq_save a2, a3
#ifdef CONFIG_TRACE_IRQFLAGS
	call4	trace_hardirqs_off
#endif

	/* Jump if we are returning from kernel exceptions. */

	l32i	a3, a1, PT_PS
	GET_THREAD_INFO(a2, a1)
	l32i	a4, a2, TI_FLAGS
	_bbci.l	a3, PS_UM_BIT, 6f

	/* Specific to a user exception exit:
	 * We need to check some flags for signal handling and rescheduling,
	 * and have to restore WB and WS, extra states, and all registers
	 * in the register file that were in use in the user task.
	 * Note that we don't disable interrupts here. 
	 */

	_bbsi.l	a4, TIF_NEED_RESCHED, 3f
	_bbsi.l	a4, TIF_NOTIFY_RESUME, 2f
	_bbci.l	a4, TIF_SIGPENDING, 5f

2:	l32i	a4, a1, PT_DEPC
	bgeui	a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 4f

	/* Call do_signal() */

#ifdef CONFIG_TRACE_IRQFLAGS
	call4	trace_hardirqs_on
#endif
	rsil	a2, 0
	mov	a6, a1
	call4	do_notify_resume	# int do_notify_resume(struct pt_regs*)
	j	1b

3:	/* Reschedule */

#ifdef CONFIG_TRACE_IRQFLAGS
	call4	trace_hardirqs_on
#endif
	rsil	a2, 0
	call4	schedule	# void schedule (void)
	j	1b

#ifdef CONFIG_PREEMPT
6:
	_bbci.l	a4, TIF_NEED_RESCHED, 4f

	/* Check current_thread_info->preempt_count */

	l32i	a4, a2, TI_PRE_COUNT
	bnez	a4, 4f
	call4	preempt_schedule_irq
	j	1b
#endif

#if XTENSA_FAKE_NMI
.LNMIexit:
	l32i	a3, a1, PT_PS
	_bbci.l	a3, PS_UM_BIT, 4f
#endif

5:
#ifdef CONFIG_HAVE_HW_BREAKPOINT
	_bbci.l	a4, TIF_DB_DISABLED, 7f
	call4	restore_dbreak
7:
#endif
#ifdef CONFIG_DEBUG_TLB_SANITY
	l32i	a4, a1, PT_DEPC
	bgeui	a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 4f
	call4	check_tlb_sanity
#endif
6:
4:
#ifdef CONFIG_TRACE_IRQFLAGS
	extui	a4, a3, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
	bgei	a4, LOCKLEVEL, 1f
	call4	trace_hardirqs_on
1:
#endif
	/* Restore optional registers. */

	load_xtregs_opt a1 a2 a4 a5 a6 a7 PT_XTREGS_OPT

	/* Restore SCOMPARE1 */

#if XCHAL_HAVE_S32C1I
	l32i    a2, a1, PT_SCOMPARE1
	wsr     a2, scompare1
#endif
	wsr	a3, ps		/* disable interrupts */

	_bbci.l	a3, PS_UM_BIT, kernel_exception_exit

user_exception_exit:

	/* Restore the state of the task and return from the exception. */

	/* Switch to the user thread WINDOWBASE. Save SP temporarily in DEPC */

	l32i	a2, a1, PT_WINDOWBASE
	l32i	a3, a1, PT_WINDOWSTART
	wsr	a1, depc		# use DEPC as temp storage
	wsr	a3, windowstart		# restore WINDOWSTART
	ssr	a2			# preserve user's WB in the SAR
	wsr	a2, windowbase		# switch to user's saved WB
	rsync
	rsr	a1, depc		# restore stack pointer
	l32i	a2, a1, PT_WMASK	# register frames saved (in bits 4...9)
	rotw	-1			# we restore a4..a7
	_bltui	a6, 16, 1f		# only have to restore current window?

	/* The working registers are a0 and a3.  We are restoring to
	 * a4..a7.  Be careful not to destroy what we have just restored.
	 * Note: wmask has the format YYYYM:
	 *       Y: number of registers saved in groups of 4
	 *       M: 4 bit mask of first 16 registers
	 */

	mov	a2, a6
	mov	a3, a5

2:	rotw	-1			# a0..a3 become a4..a7
	addi	a3, a7, -4*4		# next iteration
	addi	a2, a6, -16		# decrementing Y in WMASK
	l32i	a4, a3, PT_AREG_END + 0
	l32i	a5, a3, PT_AREG_END + 4
	l32i	a6, a3, PT_AREG_END + 8
	l32i	a7, a3, PT_AREG_END + 12
	_bgeui	a2, 16, 2b

	/* Clear unrestored registers (don't leak anything to user-land */

1:	rsr	a0, windowbase
	rsr	a3, sar
	sub	a3, a0, a3
	beqz	a3, 2f
	extui	a3, a3, 0, WBBITS

1:	rotw	-1
	addi	a3, a7, -1
	movi	a4, 0
	movi	a5, 0
	movi	a6, 0
	movi	a7, 0
	bgei	a3, 1, 1b

	/* We are back were we were when we started.
	 * Note: a2 still contains WMASK (if we've returned to the original
	 *	 frame where we had loaded a2), or at least the lower 4 bits
	 *	 (if we have restored WSBITS-1 frames).
	 */

2:
#if XCHAL_HAVE_THREADPTR
	l32i	a3, a1, PT_THREADPTR
	wur	a3, threadptr
#endif

	j	common_exception_exit

	/* This is the kernel exception exit.
	 * We avoided to do a MOVSP when we entered the exception, but we
	 * have to do it here.
	 */

kernel_exception_exit:

	/* Check if we have to do a movsp.
	 *
	 * We only have to do a movsp if the previous window-frame has
	 * been spilled to the *temporary* exception stack instead of the
	 * task's stack. This is the case if the corresponding bit in
	 * WINDOWSTART for the previous window-frame was set before
	 * (not spilled) but is zero now (spilled).
	 * If this bit is zero, all other bits except the one for the
	 * current window frame are also zero. So, we can use a simple test:
	 * 'and' WINDOWSTART and WINDOWSTART-1:
	 *
	 *  (XXXXXX1[0]* - 1) AND XXXXXX1[0]* = XXXXXX0[0]*
	 *
	 * The result is zero only if one bit was set.
	 *
	 * (Note: We might have gone through several task switches before
	 *        we come back to the current task, so WINDOWBASE might be
	 *        different from the time the exception occurred.)
	 */

	/* Test WINDOWSTART before and after the exception.
	 * We actually have WMASK, so we only have to test if it is 1 or not.
	 */

	l32i	a2, a1, PT_WMASK
	_beqi	a2, 1, common_exception_exit	# Spilled before exception,jump

	/* Test WINDOWSTART now. If spilled, do the movsp */

	rsr     a3, windowstart
	addi	a0, a3, -1
	and     a3, a3, a0
	_bnez	a3, common_exception_exit

	/* Do a movsp (we returned from a call4, so we have at least a0..a7) */

	addi    a0, a1, -16
	l32i    a3, a0, 0
	l32i    a4, a0, 4
	s32i    a3, a1, PT_SIZE+0
	s32i    a4, a1, PT_SIZE+4
	l32i    a3, a0, 8
	l32i    a4, a0, 12
	s32i    a3, a1, PT_SIZE+8
	s32i    a4, a1, PT_SIZE+12

	/* Common exception exit.
	 * We restore the special register and the current window frame, and
	 * return from the exception.
	 *
	 * Note: We expect a2 to hold PT_WMASK
	 */

common_exception_exit:

	/* Restore address registers. */

	_bbsi.l	a2, 1, 1f
	l32i	a4,  a1, PT_AREG4
	l32i	a5,  a1, PT_AREG5
	l32i	a6,  a1, PT_AREG6
	l32i	a7,  a1, PT_AREG7
	_bbsi.l	a2, 2, 1f
	l32i	a8,  a1, PT_AREG8
	l32i	a9,  a1, PT_AREG9
	l32i	a10, a1, PT_AREG10
	l32i	a11, a1, PT_AREG11
	_bbsi.l	a2, 3, 1f
	l32i	a12, a1, PT_AREG12
	l32i	a13, a1, PT_AREG13
	l32i	a14, a1, PT_AREG14
	l32i	a15, a1, PT_AREG15

	/* Restore PC, SAR */

1:	l32i	a2, a1, PT_PC
	l32i	a3, a1, PT_SAR
	wsr	a2, epc1
	wsr	a3, sar

	/* Restore LBEG, LEND, LCOUNT */
#if XCHAL_HAVE_LOOPS
	l32i	a2, a1, PT_LBEG
	l32i	a3, a1, PT_LEND
	wsr	a2, lbeg
	l32i	a2, a1, PT_LCOUNT
	wsr	a3, lend
	wsr	a2, lcount
#endif

	/* We control single stepping through the ICOUNTLEVEL register. */

	l32i	a2, a1, PT_ICOUNTLEVEL
	movi	a3, -2
	wsr	a2, icountlevel
	wsr	a3, icount

	/* Check if it was double exception. */

	l32i	a0, a1, PT_DEPC
	l32i	a3, a1, PT_AREG3
	l32i	a2, a1, PT_AREG2
	_bgeui	a0, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f

	/* Restore a0...a3 and return */

	l32i	a0, a1, PT_AREG0
	l32i	a1, a1, PT_AREG1
	rfe

1: 	wsr	a0, depc
	l32i	a0, a1, PT_AREG0
	l32i	a1, a1, PT_AREG1
	rfde

ENDPROC(kernel_exception)

/*
 * Debug exception handler.
 *
 * Currently, we don't support KGDB, so only user application can be debugged.
 *
 * When we get here,  a0 is trashed and saved to excsave[debuglevel]
 */

	.literal_position

ENTRY(debug_exception)

	rsr	a0, SREG_EPS + XCHAL_DEBUGLEVEL
	bbsi.l	a0, PS_EXCM_BIT, 1f	# exception mode

	/* Set EPC1 and EXCCAUSE */

	wsr	a2, depc		# save a2 temporarily
	rsr	a2, SREG_EPC + XCHAL_DEBUGLEVEL
	wsr	a2, epc1

	movi	a2, EXCCAUSE_MAPPED_DEBUG
	wsr	a2, exccause

	/* Restore PS to the value before the debug exc but with PS.EXCM set.*/

	movi	a2, 1 << PS_EXCM_BIT
	or	a2, a0, a2
	wsr	a2, ps

	/* Switch to kernel/user stack, restore jump vector, and save a0 */

	bbsi.l	a2, PS_UM_BIT, 2f	# jump if user mode

	addi	a2, a1, -16-PT_SIZE	# assume kernel stack
3:
	l32i	a0, a3, DT_DEBUG_SAVE
	s32i	a1, a2, PT_AREG1
	s32i	a0, a2, PT_AREG0
	movi	a0, 0
	s32i	a0, a2, PT_DEPC		# mark it as a regular exception
	xsr	a3, SREG_EXCSAVE + XCHAL_DEBUGLEVEL
	xsr	a0, depc
	s32i	a3, a2, PT_AREG3
	s32i	a0, a2, PT_AREG2
	mov	a1, a2

	/* Debug exception is handled as an exception, so interrupts will
	 * likely be enabled in the common exception handler. Disable
	 * preemption if we have HW breakpoints to preserve DEBUGCAUSE.DBNUM
	 * meaning.
	 */
#if defined(CONFIG_PREEMPT_COUNT) && defined(CONFIG_HAVE_HW_BREAKPOINT)
	GET_THREAD_INFO(a2, a1)
	l32i	a3, a2, TI_PRE_COUNT
	addi	a3, a3, 1
	s32i	a3, a2, TI_PRE_COUNT
#endif

	rsr	a2, ps
	bbsi.l	a2, PS_UM_BIT, _user_exception
	j	_kernel_exception

2:	rsr	a2, excsave1
	l32i	a2, a2, EXC_TABLE_KSTK	# load kernel stack pointer
	j	3b

#ifdef CONFIG_HAVE_HW_BREAKPOINT
	/* Debug exception while in exception mode. This may happen when
	 * window overflow/underflow handler or fast exception handler hits
	 * data breakpoint, in which case save and disable all data
	 * breakpoints, single-step faulting instruction and restore data
	 * breakpoints.
	 */
1:
	bbci.l	a0, PS_UM_BIT, 1b	# jump if kernel mode

	rsr	a0, debugcause
	bbsi.l	a0, DEBUGCAUSE_DBREAK_BIT, .Ldebug_save_dbreak

	.set	_index, 0
	.rept	XCHAL_NUM_DBREAK
	l32i	a0, a3, DT_DBREAKC_SAVE + _index * 4
	wsr	a0, SREG_DBREAKC + _index
	.set	_index, _index + 1
	.endr

	l32i	a0, a3, DT_ICOUNT_LEVEL_SAVE
	wsr	a0, icountlevel

	l32i	a0, a3, DT_ICOUNT_SAVE
	xsr	a0, icount

	l32i	a0, a3, DT_DEBUG_SAVE
	xsr	a3, SREG_EXCSAVE + XCHAL_DEBUGLEVEL
	rfi	XCHAL_DEBUGLEVEL

.Ldebug_save_dbreak:
	.set	_index, 0
	.rept	XCHAL_NUM_DBREAK
	movi	a0, 0
	xsr	a0, SREG_DBREAKC + _index
	s32i	a0, a3, DT_DBREAKC_SAVE + _index * 4
	.set	_index, _index + 1
	.endr

	movi	a0, XCHAL_EXCM_LEVEL + 1
	xsr	a0, icountlevel
	s32i	a0, a3, DT_ICOUNT_LEVEL_SAVE

	movi	a0, 0xfffffffe
	xsr	a0, icount
	s32i	a0, a3, DT_ICOUNT_SAVE

	l32i	a0, a3, DT_DEBUG_SAVE
	xsr	a3, SREG_EXCSAVE + XCHAL_DEBUGLEVEL
	rfi	XCHAL_DEBUGLEVEL
#else
	/* Debug exception while in exception mode. Should not happen. */
1:	j	1b	// FIXME!!
#endif

ENDPROC(debug_exception)

/*
 * We get here in case of an unrecoverable exception.
 * The only thing we can do is to be nice and print a panic message.
 * We only produce a single stack frame for panic, so ???
 *
 *
 * Entry conditions:
 *
 *   - a0 contains the caller address; original value saved in excsave1.
 *   - the original a0 contains a valid return address (backtrace) or 0.
 *   - a2 contains a valid stackpointer
 *
 * Notes:
 *
 *   - If the stack pointer could be invalid, the caller has to setup a
 *     dummy stack pointer (e.g. the stack of the init_task)
 *
 *   - If the return address could be invalid, the caller has to set it
 *     to 0, so the backtrace would stop.
 *
 */
	.align 4
unrecoverable_text:
	.ascii "Unrecoverable error in exception handler\0"

	.literal_position

ENTRY(unrecoverable_exception)

	movi	a0, 1
	movi	a1, 0

	wsr	a0, windowstart
	wsr	a1, windowbase
	rsync

	movi	a1, PS_WOE_MASK | LOCKLEVEL
	wsr	a1, ps
	rsync

	movi	a1, init_task
	movi	a0, 0
	addi	a1, a1, PT_REGS_OFFSET

	movi	a6, unrecoverable_text
	call4	panic

1:	j	1b

ENDPROC(unrecoverable_exception)

/* -------------------------- FAST EXCEPTION HANDLERS ----------------------- */

/*
 * Fast-handler for alloca exceptions
 *
 *  The ALLOCA handler is entered when user code executes the MOVSP
 *  instruction and the caller's frame is not in the register file.
 *
 * This algorithm was taken from the Ross Morley's RTOS Porting Layer:
 *
 *    /home/ross/rtos/porting/XtensaRTOS-PortingLayer-20090507/xtensa_vectors.S
 *
 * It leverages the existing window spill/fill routines and their support for
 * double exceptions. The 'movsp' instruction will only cause an exception if
 * the next window needs to be loaded. In fact this ALLOCA exception may be
 * replaced at some point by changing the hardware to do a underflow exception
 * of the proper size instead.
 *
 * This algorithm simply backs out the register changes started by the user
 * excpetion handler, makes it appear that we have started a window underflow
 * by rotating the window back and then setting the old window base (OWB) in
 * the 'ps' register with the rolled back window base. The 'movsp' instruction
 * will be re-executed and this time since the next window frames is in the
 * active AR registers it won't cause an exception.
 *
 * If the WindowUnderflow code gets a TLB miss the page will get mapped
 * the the partial windeowUnderflow will be handeled in the double exception
 * handler.
 *
 * Entry condition:
 *
 *   a0:	trashed, original value saved on stack (PT_AREG0)
 *   a1:	a1
 *   a2:	new stack pointer, original in DEPC
 *   a3:	a3
 *   depc:	a2, original value saved on stack (PT_DEPC)
 *   excsave_1:	dispatch table
 *
 *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
 *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
 */

ENTRY(fast_alloca)
	rsr	a0, windowbase
	rotw	-1
	rsr	a2, ps
	extui	a3, a2, PS_OWB_SHIFT, PS_OWB_WIDTH
	xor	a3, a3, a4
	l32i	a4, a6, PT_AREG0
	l32i	a1, a6, PT_DEPC
	rsr	a6, depc
	wsr	a1, depc
	slli	a3, a3, PS_OWB_SHIFT
	xor	a2, a2, a3
	wsr	a2, ps
	rsync

	_bbci.l	a4, 31, 4f
	rotw	-1
	_bbci.l	a8, 30, 8f
	rotw	-1
	j	_WindowUnderflow12
8:	j	_WindowUnderflow8
4:	j	_WindowUnderflow4
ENDPROC(fast_alloca)

#ifdef CONFIG_USER_ABI_CALL0_PROBE
/*
 * fast illegal instruction handler.
 *
 * This is used to fix up user PS.WOE on the exception caused
 * by the first opcode related to register window. If PS.WOE is
 * already set it goes directly to the common user exception handler.
 *
 * Entry condition:
 *
 *   a0:	trashed, original value saved on stack (PT_AREG0)
 *   a1:	a1
 *   a2:	new stack pointer, original in DEPC
 *   a3:	a3
 *   depc:	a2, original value saved on stack (PT_DEPC)
 *   excsave_1:	dispatch table
 */

ENTRY(fast_illegal_instruction_user)

	rsr	a0, ps
	bbsi.l	a0, PS_WOE_BIT, user_exception
	s32i	a3, a2, PT_AREG3
	movi	a3, PS_WOE_MASK
	or	a0, a0, a3
	wsr	a0, ps
	l32i	a3, a2, PT_AREG3
	l32i	a0, a2, PT_AREG0
	rsr	a2, depc
	rfe

ENDPROC(fast_illegal_instruction_user)
#endif

	/*
 * fast system calls.
 *
 * WARNING:  The kernel doesn't save the entire user context before
 * handling a fast system call.  These functions are small and short,
 * usually offering some functionality not available to user tasks.
 *
 * BE CAREFUL TO PRESERVE THE USER'S CONTEXT.
 *
 * Entry condition:
 *
 *   a0:	trashed, original value saved on stack (PT_AREG0)
 *   a1:	a1
 *   a2:	new stack pointer, original in DEPC
 *   a3:	a3
 *   depc:	a2, original value saved on stack (PT_DEPC)
 *   excsave_1:	dispatch table
 */

ENTRY(fast_syscall_user)

	/* Skip syscall. */

	rsr	a0, epc1
	addi	a0, a0, 3
	wsr	a0, epc1

	l32i	a0, a2, PT_DEPC
	bgeui	a0, VALID_DOUBLE_EXCEPTION_ADDRESS, fast_syscall_unrecoverable

	rsr	a0, depc			# get syscall-nr
	_beqz	a0, fast_syscall_spill_registers
	_beqi	a0, __NR_xtensa, fast_syscall_xtensa

	j	user_exception

ENDPROC(fast_syscall_user)

ENTRY(fast_syscall_unrecoverable)

	/* Restore all states. */

	l32i    a0, a2, PT_AREG0        # restore a0
	xsr     a2, depc                # restore a2, depc

	wsr     a0, excsave1
	call0	unrecoverable_exception

ENDPROC(fast_syscall_unrecoverable)

/*
 * sysxtensa syscall handler
 *
 * int sysxtensa (SYS_XTENSA_ATOMIC_SET,     ptr, val,    unused);
 * int sysxtensa (SYS_XTENSA_ATOMIC_ADD,     ptr, val,    unused);
 * int sysxtensa (SYS_XTENSA_ATOMIC_EXG_ADD, ptr, val,    unused);
 * int sysxtensa (SYS_XTENSA_ATOMIC_CMP_SWP, ptr, oldval, newval);
 *        a2            a6                   a3    a4      a5
 *
 * Entry condition:
 *
 *   a0:	a2 (syscall-nr), original value saved on stack (PT_AREG0)
 *   a1:	a1
 *   a2:	new stack pointer, original in a0 and DEPC
 *   a3:	a3
 *   a4..a15:	unchanged
 *   depc:	a2, original value saved on stack (PT_DEPC)
 *   excsave_1:	dispatch table
 *
 *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
 *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
 *
 * Note: we don't have to save a2; a2 holds the return value
 */

	.literal_position

#ifdef CONFIG_FAST_SYSCALL_XTENSA

ENTRY(fast_syscall_xtensa)

	s32i	a7, a2, PT_AREG7	# we need an additional register
	movi	a7, 4			# sizeof(unsigned int)
	access_ok a3, a7, a0, a2, .Leac	# a0: scratch reg, a2: sp

	_bgeui	a6, SYS_XTENSA_COUNT, .Lill
	_bnei	a6, SYS_XTENSA_ATOMIC_CMP_SWP, .Lnswp

	/* Fall through for ATOMIC_CMP_SWP. */

.Lswp:	/* Atomic compare and swap */

EX(.Leac) l32i	a0, a3, 0		# read old value
	bne	a0, a4, 1f		# same as old value? jump
EX(.Leac) s32i	a5, a3, 0		# different, modify value
	l32i	a7, a2, PT_AREG7	# restore a7
	l32i	a0, a2, PT_AREG0	# restore a0
	movi	a2, 1			# and return 1
	rfe

1:	l32i	a7, a2, PT_AREG7	# restore a7
	l32i	a0, a2, PT_AREG0	# restore a0
	movi	a2, 0			# return 0 (note that we cannot set
	rfe

.Lnswp:	/* Atomic set, add, and exg_add. */

EX(.Leac) l32i	a7, a3, 0		# orig
	addi	a6, a6, -SYS_XTENSA_ATOMIC_SET
	add	a0, a4, a7		# + arg
	moveqz	a0, a4, a6		# set
	addi	a6, a6, SYS_XTENSA_ATOMIC_SET
EX(.Leac) s32i	a0, a3, 0		# write new value

	mov	a0, a2
	mov	a2, a7
	l32i	a7, a0, PT_AREG7	# restore a7
	l32i	a0, a0, PT_AREG0	# restore a0
	rfe

.Leac:	l32i	a7, a2, PT_AREG7	# restore a7
	l32i	a0, a2, PT_AREG0	# restore a0
	movi	a2, -EFAULT
	rfe

.Lill:	l32i	a7, a2, PT_AREG7	# restore a7
	l32i	a0, a2, PT_AREG0	# restore a0
	movi	a2, -EINVAL
	rfe

ENDPROC(fast_syscall_xtensa)

#else /* CONFIG_FAST_SYSCALL_XTENSA */

ENTRY(fast_syscall_xtensa)

	l32i    a0, a2, PT_AREG0        # restore a0
	movi	a2, -ENOSYS
	rfe

ENDPROC(fast_syscall_xtensa)

#endif /* CONFIG_FAST_SYSCALL_XTENSA */


/* fast_syscall_spill_registers.
 *
 * Entry condition:
 *
 *   a0:	trashed, original value saved on stack (PT_AREG0)
 *   a1:	a1
 *   a2:	new stack pointer, original in DEPC
 *   a3:	a3
 *   depc:	a2, original value saved on stack (PT_DEPC)
 *   excsave_1:	dispatch table
 *
 * Note: We assume the stack pointer is EXC_TABLE_KSTK in the fixup handler.
 */

#ifdef CONFIG_FAST_SYSCALL_SPILL_REGISTERS

ENTRY(fast_syscall_spill_registers)

	/* Register a FIXUP handler (pass current wb as a parameter) */

	xsr	a3, excsave1
	movi	a0, fast_syscall_spill_registers_fixup
	s32i	a0, a3, EXC_TABLE_FIXUP
	rsr	a0, windowbase
	s32i	a0, a3, EXC_TABLE_PARAM
	xsr	a3, excsave1		# restore a3 and excsave_1

	/* Save a3, a4 and SAR on stack. */

	rsr	a0, sar
	s32i	a3, a2, PT_AREG3
	s32i	a0, a2, PT_SAR

	/* The spill routine might clobber a4, a7, a8, a11, a12, and a15. */

	s32i	a4, a2, PT_AREG4
	s32i	a7, a2, PT_AREG7
	s32i	a8, a2, PT_AREG8
	s32i	a11, a2, PT_AREG11
	s32i	a12, a2, PT_AREG12
	s32i	a15, a2, PT_AREG15

	/*
	 * Rotate ws so that the current windowbase is at bit 0.
	 * Assume ws = xxxwww1yy (www1 current window frame).
	 * Rotate ws right so that a4 = yyxxxwww1.
	 */

	rsr	a0, windowbase
	rsr	a3, windowstart		# a3 = xxxwww1yy
	ssr	a0			# holds WB
	slli	a0, a3, WSBITS
	or	a3, a3, a0		# a3 = xxxwww1yyxxxwww1yy
	srl	a3, a3			# a3 = 00xxxwww1yyxxxwww1

	/* We are done if there are no more than the current register frame. */

	extui	a3, a3, 1, WSBITS-1	# a3 = 0yyxxxwww
	movi	a0, (1 << (WSBITS-1))
	_beqz	a3, .Lnospill		# only one active frame? jump

	/* We want 1 at the top, so that we return to the current windowbase */

	or	a3, a3, a0		# 1yyxxxwww

	/* Skip empty frames - get 'oldest' WINDOWSTART-bit. */

	wsr	a3, windowstart		# save shifted windowstart
	neg	a0, a3
	and	a3, a0, a3		# first bit set from right: 000010000

	ffs_ws	a0, a3			# a0: shifts to skip empty frames
	movi	a3, WSBITS
	sub	a0, a3, a0		# WSBITS-a0:number of 0-bits from right
	ssr	a0			# save in SAR for later.

	rsr	a3, windowbase
	add	a3, a3, a0
	wsr	a3, windowbase
	rsync

	rsr	a3, windowstart
	srl	a3, a3			# shift windowstart

	/* WB is now just one frame below the oldest frame in the register
	   window. WS is shifted so the oldest frame is in bit 0, thus, WB
	   and WS differ by one 4-register frame. */

	/* Save frames. Depending what call was used (call4, call8, call12),
	 * we have to save 4,8. or 12 registers.
	 */


.Lloop: _bbsi.l	a3, 1, .Lc4
	_bbci.l	a3, 2, .Lc12

.Lc8:	s32e	a4, a13, -16
	l32e	a4, a5, -12
	s32e	a8, a4, -32
	s32e	a5, a13, -12
	s32e	a6, a13, -8
	s32e	a7, a13, -4
	s32e	a9, a4, -28
	s32e	a10, a4, -24
	s32e	a11, a4, -20
	srli	a11, a3, 2		# shift windowbase by 2
	rotw	2
	_bnei	a3, 1, .Lloop
	j	.Lexit

.Lc4:	s32e	a4, a9, -16
	s32e	a5, a9, -12
	s32e	a6, a9, -8
	s32e	a7, a9, -4

	srli	a7, a3, 1
	rotw	1
	_bnei	a3, 1, .Lloop
	j	.Lexit

.Lc12:	_bbci.l	a3, 3, .Linvalid_mask	# bit 2 shouldn't be zero!

	/* 12-register frame (call12) */

	l32e	a0, a5, -12
	s32e	a8, a0, -48
	mov	a8, a0

	s32e	a9, a8, -44
	s32e	a10, a8, -40
	s32e	a11, a8, -36
	s32e	a12, a8, -32
	s32e	a13, a8, -28
	s32e	a14, a8, -24
	s32e	a15, a8, -20
	srli	a15, a3, 3

	/* The stack pointer for a4..a7 is out of reach, so we rotate the
	 * window, grab the stackpointer, and rotate back.
	 * Alternatively, we could also use the following approach, but that
	 * makes the fixup routine much more complicated:
	 * rotw	1
	 * s32e	a0, a13, -16
	 * ...
	 * rotw 2
	 */

	rotw	1
	mov	a4, a13
	rotw	-1

	s32e	a4, a8, -16
	s32e	a5, a8, -12
	s32e	a6, a8, -8
	s32e	a7, a8, -4

	rotw	3

	_beqi	a3, 1, .Lexit
	j	.Lloop

.Lexit:

	/* Done. Do the final rotation and set WS */

	rotw	1
	rsr	a3, windowbase
	ssl	a3
	movi	a3, 1
	sll	a3, a3
	wsr	a3, windowstart
.Lnospill:

	/* Advance PC, restore registers and SAR, and return from exception. */

	l32i	a3, a2, PT_SAR
	l32i	a0, a2, PT_AREG0
	wsr	a3, sar
	l32i	a3, a2, PT_AREG3

	/* Restore clobbered registers. */

	l32i	a4, a2, PT_AREG4
	l32i	a7, a2, PT_AREG7
	l32i	a8, a2, PT_AREG8
	l32i	a11, a2, PT_AREG11
	l32i	a12, a2, PT_AREG12
	l32i	a15, a2, PT_AREG15

	movi	a2, 0
	rfe

.Linvalid_mask:

	/* We get here because of an unrecoverable error in the window
	 * registers, so set up a dummy frame and kill the user application.
	 * Note: We assume EXC_TABLE_KSTK contains a valid stack pointer.
	 */

	movi	a0, 1
	movi	a1, 0

	wsr	a0, windowstart
	wsr	a1, windowbase
	rsync

	movi	a0, 0

	rsr	a3, excsave1
	l32i	a1, a3, EXC_TABLE_KSTK

	movi	a4, PS_WOE_MASK | LOCKLEVEL
	wsr	a4, ps
	rsync

	movi	a6, SIGSEGV
	call4	do_exit

	/* shouldn't return, so panic */

	wsr	a0, excsave1
	call0	unrecoverable_exception		# should not return
1:	j	1b


ENDPROC(fast_syscall_spill_registers)

/* Fixup handler.
 *
 * We get here if the spill routine causes an exception, e.g. tlb miss.
 * We basically restore WINDOWBASE and WINDOWSTART to the condition when
 * we entered the spill routine and jump to the user exception handler.
 *
 * Note that we only need to restore the bits in windowstart that have not
 * been spilled yet by the _spill_register routine. Luckily, a3 contains a
 * rotated windowstart with only those bits set for frames that haven't been
 * spilled yet. Because a3 is rotated such that bit 0 represents the register
 * frame for the current windowbase - 1, we need to rotate a3 left by the
 * value of the current windowbase + 1 and move it to windowstart.
 *
 * a0: value of depc, original value in depc
 * a2: trashed, original value in EXC_TABLE_DOUBLE_SAVE
 * a3: exctable, original value in excsave1
 */

ENTRY(fast_syscall_spill_registers_fixup)

	rsr	a2, windowbase	# get current windowbase (a2 is saved)
	xsr	a0, depc	# restore depc and a0
	ssl	a2		# set shift (32 - WB)

	/* We need to make sure the current registers (a0-a3) are preserved.
	 * To do this, we simply set the bit for the current window frame
	 * in WS, so that the exception handlers save them to the task stack.
	 *
	 * Note: we use a3 to set the windowbase, so we take a special care
	 * of it, saving it in the original _spill_registers frame across
	 * the exception handler call.
	 */

	xsr	a3, excsave1	# get spill-mask
	slli	a3, a3, 1	# shift left by one
	addi	a3, a3, 1	# set the bit for the current window frame

	slli	a2, a3, 32-WSBITS
	src	a2, a3, a2	# a2 = xxwww1yyxxxwww1yy......
	wsr	a2, windowstart	# set corrected windowstart

	srli	a3, a3, 1
	rsr	a2, excsave1
	l32i	a2, a2, EXC_TABLE_DOUBLE_SAVE	# restore a2
	xsr	a2, excsave1
	s32i	a3, a2, EXC_TABLE_DOUBLE_SAVE	# save a3
	l32i	a3, a2, EXC_TABLE_PARAM	# original WB (in user task)
	xsr	a2, excsave1

	/* Return to the original (user task) WINDOWBASE.
	 * We leave the following frame behind:
	 * a0, a1, a2	same
	 * a3:		trashed (saved in EXC_TABLE_DOUBLE_SAVE)
	 * depc:	depc (we have to return to that address)
	 * excsave_1:	exctable
	 */

	wsr	a3, windowbase
	rsync

	/* We are now in the original frame when we entered _spill_registers:
	 *  a0: return address
	 *  a1: used, stack pointer
	 *  a2: kernel stack pointer
	 *  a3: available
	 *  depc: exception address
	 *  excsave: exctable
	 * Note: This frame might be the same as above.
	 */

	/* Setup stack pointer. */

	addi	a2, a2, -PT_USER_SIZE
	s32i	a0, a2, PT_AREG0

	/* Make sure we return to this fixup handler. */

	movi	a3, fast_syscall_spill_registers_fixup_return
	s32i	a3, a2, PT_DEPC		# setup depc

	/* Jump to the exception handler. */

	rsr	a3, excsave1
	rsr	a0, exccause
	addx4	a0, a0, a3              	# find entry in table
	l32i	a0, a0, EXC_TABLE_FAST_USER     # load handler
	l32i	a3, a3, EXC_TABLE_DOUBLE_SAVE
	jx	a0

ENDPROC(fast_syscall_spill_registers_fixup)

ENTRY(fast_syscall_spill_registers_fixup_return)

	/* When we return here, all registers have been restored (a2: DEPC) */

	wsr	a2, depc		# exception address

	/* Restore fixup handler. */

	rsr	a2, excsave1
	s32i	a3, a2, EXC_TABLE_DOUBLE_SAVE
	movi	a3, fast_syscall_spill_registers_fixup
	s32i	a3, a2, EXC_TABLE_FIXUP
	rsr	a3, windowbase
	s32i	a3, a2, EXC_TABLE_PARAM
	l32i	a2, a2, EXC_TABLE_KSTK

	/* Load WB at the time the exception occurred. */

	rsr	a3, sar			# WB is still in SAR
	neg	a3, a3
	wsr	a3, windowbase
	rsync

	rsr	a3, excsave1
	l32i	a3, a3, EXC_TABLE_DOUBLE_SAVE

	rfde

ENDPROC(fast_syscall_spill_registers_fixup_return)

#else /* CONFIG_FAST_SYSCALL_SPILL_REGISTERS */

ENTRY(fast_syscall_spill_registers)

	l32i    a0, a2, PT_AREG0        # restore a0
	movi	a2, -ENOSYS
	rfe

ENDPROC(fast_syscall_spill_registers)

#endif /* CONFIG_FAST_SYSCALL_SPILL_REGISTERS */

#ifdef CONFIG_MMU
/*
 * We should never get here. Bail out!
 */

ENTRY(fast_second_level_miss_double_kernel)

1:
	call0	unrecoverable_exception		# should not return
1:	j	1b

ENDPROC(fast_second_level_miss_double_kernel)

/* First-level entry handler for user, kernel, and double 2nd-level
 * TLB miss exceptions.  Note that for now, user and kernel miss
 * exceptions share the same entry point and are handled identically.
 *
 * An old, less-efficient C version of this function used to exist.
 * We include it below, interleaved as comments, for reference.
 *
 * Entry condition:
 *
 *   a0:	trashed, original value saved on stack (PT_AREG0)
 *   a1:	a1
 *   a2:	new stack pointer, original in DEPC
 *   a3:	a3
 *   depc:	a2, original value saved on stack (PT_DEPC)
 *   excsave_1:	dispatch table
 *
 *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
 *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
 */

ENTRY(fast_second_level_miss)

	/* Save a1 and a3. Note: we don't expect a double exception. */

	s32i	a1, a2, PT_AREG1
	s32i	a3, a2, PT_AREG3

	/* We need to map the page of PTEs for the user task.  Find
	 * the pointer to that page.  Also, it's possible for tsk->mm
	 * to be NULL while tsk->active_mm is nonzero if we faulted on
	 * a vmalloc address.  In that rare case, we must use
	 * active_mm instead to avoid a fault in this handler.  See
	 *
	 * http://mail.nl.linux.org/linux-mm/2002-08/msg00258.html
	 *   (or search Internet on "mm vs. active_mm")
	 *
	 *	if (!mm)
	 *		mm = tsk->active_mm;
	 *	pgd = pgd_offset (mm, regs->excvaddr);
	 *	pmd = pmd_offset (pgd, regs->excvaddr);
	 *	pmdval = *pmd;
	 */

	GET_CURRENT(a1,a2)
	l32i	a0, a1, TASK_MM		# tsk->mm
	beqz	a0, 9f

8:	rsr	a3, excvaddr		# fault address
	_PGD_OFFSET(a0, a3, a1)
	l32i	a0, a0, 0		# read pmdval
	beqz	a0, 2f

	/* Read ptevaddr and convert to top of page-table page.
	 *
	 * 	vpnval = read_ptevaddr_register() & PAGE_MASK;
	 * 	vpnval += DTLB_WAY_PGTABLE;
	 *	pteval = mk_pte (virt_to_page(pmd_val(pmdval)), PAGE_KERNEL);
	 *	write_dtlb_entry (pteval, vpnval);
	 *
	 * The messy computation for 'pteval' above really simplifies
	 * into the following:
	 *
	 * pteval = ((pmdval - PAGE_OFFSET + PHYS_OFFSET) & PAGE_MASK)
	 *                 | PAGE_DIRECTORY
	 */

	movi	a1, (PHYS_OFFSET - PAGE_OFFSET) & 0xffffffff
	add	a0, a0, a1		# pmdval - PAGE_OFFSET
	extui	a1, a0, 0, PAGE_SHIFT	# ... & PAGE_MASK
	xor	a0, a0, a1

	movi	a1, _PAGE_DIRECTORY
	or	a0, a0, a1		# ... | PAGE_DIRECTORY

	/*
	 * We utilize all three wired-ways (7-9) to hold pmd translations.
	 * Memory regions are mapped to the DTLBs according to bits 28 and 29.
	 * This allows to map the three most common regions to three different
	 * DTLBs:
	 *  0,1 -> way 7	program (0040.0000) and virtual (c000.0000)
	 *  2   -> way 8	shared libaries (2000.0000)
	 *  3   -> way 0	stack (3000.0000)
	 */

	extui	a3, a3, 28, 2		# addr. bit 28 and 29	0,1,2,3
	rsr	a1, ptevaddr
	addx2	a3, a3, a3		# ->			0,3,6,9
	srli	a1, a1, PAGE_SHIFT
	extui	a3, a3, 2, 2		# ->			0,0,1,2
	slli	a1, a1, PAGE_SHIFT	# ptevaddr & PAGE_MASK
	addi	a3, a3, DTLB_WAY_PGD
	add	a1, a1, a3		# ... + way_number

3:	wdtlb	a0, a1
	dsync

	/* Exit critical section. */

4:	rsr	a3, excsave1
	movi	a0, 0
	s32i	a0, a3, EXC_TABLE_FIXUP

	/* Restore the working registers, and return. */

	l32i	a0, a2, PT_AREG0
	l32i	a1, a2, PT_AREG1
	l32i	a3, a2, PT_AREG3
	l32i	a2, a2, PT_DEPC

	bgeui	a2, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f

	/* Restore excsave1 and return. */

	rsr	a2, depc
	rfe

	/* Return from double exception. */

1:	xsr	a2, depc
	esync
	rfde

9:	l32i	a0, a1, TASK_ACTIVE_MM	# unlikely case mm == 0
	bnez	a0, 8b

	/* Even more unlikely case active_mm == 0.
	 * We can get here with NMI in the middle of context_switch that
	 * touches vmalloc area.
	 */
	movi	a0, init_mm
	j	8b

#if (DCACHE_WAY_SIZE > PAGE_SIZE)

2:	/* Special case for cache aliasing.
	 * We (should) only get here if a clear_user_page, copy_user_page
	 * or the aliased cache flush functions got preemptively interrupted 
	 * by another task. Re-establish temporary mapping to the 
	 * TLBTEMP_BASE areas.
	 */

	/* We shouldn't be in a double exception */

	l32i	a0, a2, PT_DEPC
	bgeui	a0, VALID_DOUBLE_EXCEPTION_ADDRESS, 2f

	/* Make sure the exception originated in the special functions */

	movi	a0, __tlbtemp_mapping_start
	rsr	a3, epc1
	bltu	a3, a0, 2f
	movi	a0, __tlbtemp_mapping_end
	bgeu	a3, a0, 2f

	/* Check if excvaddr was in one of the TLBTEMP_BASE areas. */

	movi	a3, TLBTEMP_BASE_1
	rsr	a0, excvaddr
	bltu	a0, a3, 2f

	addi	a1, a0, -TLBTEMP_SIZE
	bgeu	a1, a3, 2f

	/* Check if we have to restore an ITLB mapping. */

	movi	a1, __tlbtemp_mapping_itlb
	rsr	a3, epc1
	sub	a3, a3, a1

	/* Calculate VPN */

	movi	a1, PAGE_MASK
	and	a1, a1, a0

	/* Jump for ITLB entry */

	bgez	a3, 1f

	/* We can use up to two TLBTEMP areas, one for src and one for dst. */

	extui	a3, a0, PAGE_SHIFT + DCACHE_ALIAS_ORDER, 1
	add	a1, a3, a1

	/* PPN is in a6 for the first TLBTEMP area and in a7 for the second. */

	mov	a0, a6
	movnez	a0, a7, a3
	j	3b

	/* ITLB entry. We only use dst in a6. */

1:	witlb	a6, a1
	isync
	j	4b


#endif	// DCACHE_WAY_SIZE > PAGE_SIZE


2:	/* Invalid PGD, default exception handling */

	rsr	a1, depc
	s32i	a1, a2, PT_AREG2
	mov	a1, a2

	rsr	a2, ps
	bbsi.l	a2, PS_UM_BIT, 1f
	j	_kernel_exception
1:	j	_user_exception

ENDPROC(fast_second_level_miss)

/*
 * StoreProhibitedException
 *
 * Update the pte and invalidate the itlb mapping for this pte.
 *
 * Entry condition:
 *
 *   a0:	trashed, original value saved on stack (PT_AREG0)
 *   a1:	a1
 *   a2:	new stack pointer, original in DEPC
 *   a3:	a3
 *   depc:	a2, original value saved on stack (PT_DEPC)
 *   excsave_1:	dispatch table
 *
 *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
 *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
 */

ENTRY(fast_store_prohibited)

	/* Save a1 and a3. */

	s32i	a1, a2, PT_AREG1
	s32i	a3, a2, PT_AREG3

	GET_CURRENT(a1,a2)
	l32i	a0, a1, TASK_MM		# tsk->mm
	beqz	a0, 9f

8:	rsr	a1, excvaddr		# fault address
	_PGD_OFFSET(a0, a1, a3)
	l32i	a0, a0, 0
	beqz	a0, 2f

	/*
	 * Note that we test _PAGE_WRITABLE_BIT only if PTE is present
	 * and is not PAGE_NONE. See pgtable.h for possible PTE layouts.
	 */

	_PTE_OFFSET(a0, a1, a3)
	l32i	a3, a0, 0		# read pteval
	movi	a1, _PAGE_CA_INVALID
	ball	a3, a1, 2f
	bbci.l	a3, _PAGE_WRITABLE_BIT, 2f

	movi	a1, _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_HW_WRITE
	or	a3, a3, a1
	rsr	a1, excvaddr
	s32i	a3, a0, 0

	/* We need to flush the cache if we have page coloring. */
#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
	dhwb	a0, 0
#endif
	pdtlb	a0, a1
	wdtlb	a3, a0

	/* Exit critical section. */

	movi	a0, 0
	rsr	a3, excsave1
	s32i	a0, a3, EXC_TABLE_FIXUP

	/* Restore the working registers, and return. */

	l32i	a3, a2, PT_AREG3
	l32i	a1, a2, PT_AREG1
	l32i	a0, a2, PT_AREG0
	l32i	a2, a2, PT_DEPC

	bgeui	a2, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f

	rsr	a2, depc
	rfe

	/* Double exception. Restore FIXUP handler and return. */

1:	xsr	a2, depc
	esync
	rfde

9:	l32i	a0, a1, TASK_ACTIVE_MM	# unlikely case mm == 0
	j	8b

2:	/* If there was a problem, handle fault in C */

	rsr	a3, depc	# still holds a2
	s32i	a3, a2, PT_AREG2
	mov	a1, a2

	rsr	a2, ps
	bbsi.l	a2, PS_UM_BIT, 1f
	j	_kernel_exception
1:	j	_user_exception

ENDPROC(fast_store_prohibited)

#endif /* CONFIG_MMU */

/*
 * System Calls.
 *
 * void system_call (struct pt_regs* regs, int exccause)
 *                            a2                 a3
 */
	.literal_position

ENTRY(system_call)

	/* reserve 4 bytes on stack for function parameter */
	abi_entry(4)

	/* regs->syscall = regs->areg[2] */

	l32i	a7, a2, PT_AREG2
	s32i	a7, a2, PT_SYSCALL

	GET_THREAD_INFO(a4, a1)
	l32i	a3, a4, TI_FLAGS
	movi	a4, _TIF_WORK_MASK
	and	a3, a3, a4
	beqz	a3, 1f

	mov	a6, a2
	call4	do_syscall_trace_enter
	l32i	a7, a2, PT_SYSCALL

1:
	s32i	a7, a1, 4

	/* syscall = sys_call_table[syscall_nr] */

	movi	a4, sys_call_table
	movi	a5, __NR_syscalls
	movi	a6, -ENOSYS
	bgeu	a7, a5, 1f

	addx4	a4, a7, a4
	l32i	a4, a4, 0
	movi	a5, sys_ni_syscall;
	beq	a4, a5, 1f

	/* Load args: arg0 - arg5 are passed via regs. */

	l32i	a6, a2, PT_AREG6
	l32i	a7, a2, PT_AREG3
	l32i	a8, a2, PT_AREG4
	l32i	a9, a2, PT_AREG5
	l32i	a10, a2, PT_AREG8
	l32i	a11, a2, PT_AREG9

	/* Pass one additional argument to the syscall: pt_regs (on stack) */
	s32i	a2, a1, 0

	callx4	a4

1:	/* regs->areg[2] = return_value */

	s32i	a6, a2, PT_AREG2
	bnez	a3, 1f
	abi_ret(4)

1:
	l32i	a4, a1, 4
	l32i	a3, a2, PT_SYSCALL
	s32i	a4, a2, PT_SYSCALL
	mov	a6, a2
	call4	do_syscall_trace_leave
	s32i	a3, a2, PT_SYSCALL
	abi_ret(4)

ENDPROC(system_call)

/*
 * Spill live registers on the kernel stack macro.
 *
 * Entry condition: ps.woe is set, ps.excm is cleared
 * Exit condition: windowstart has single bit set
 * May clobber: a12, a13
 */
	.macro	spill_registers_kernel

#if XCHAL_NUM_AREGS > 16
	call12	1f
	_j	2f
	retw
	.align	4
1:
	_entry	a1, 48
	addi	a12, a0, 3
#if XCHAL_NUM_AREGS > 32
	.rept	(XCHAL_NUM_AREGS - 32) / 12
	_entry	a1, 48
	mov	a12, a0
	.endr
#endif
	_entry	a1, 16
#if XCHAL_NUM_AREGS % 12 == 0
	mov	a8, a8
#elif XCHAL_NUM_AREGS % 12 == 4
	mov	a12, a12
#elif XCHAL_NUM_AREGS % 12 == 8
	mov	a4, a4
#endif
	retw
2:
#else
	mov	a12, a12
#endif
	.endm

/*
 * Task switch.
 *
 * struct task*  _switch_to (struct task* prev, struct task* next)
 *         a2                              a2                 a3
 */

ENTRY(_switch_to)

	abi_entry(XTENSA_SPILL_STACK_RESERVE)

	mov	a11, a3			# and 'next' (a3)

	l32i	a4, a2, TASK_THREAD_INFO
	l32i	a5, a3, TASK_THREAD_INFO

	save_xtregs_user a4 a6 a8 a9 a12 a13 THREAD_XTREGS_USER

#if THREAD_RA > 1020 || THREAD_SP > 1020
	addi	a10, a2, TASK_THREAD
	s32i	a0, a10, THREAD_RA - TASK_THREAD	# save return address
	s32i	a1, a10, THREAD_SP - TASK_THREAD	# save stack pointer
#else
	s32i	a0, a2, THREAD_RA	# save return address
	s32i	a1, a2, THREAD_SP	# save stack pointer
#endif

#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP)
	movi	a6, __stack_chk_guard
	l32i	a8, a3, TASK_STACK_CANARY
	s32i	a8, a6, 0
#endif

	/* Disable ints while we manipulate the stack pointer. */

	irq_save a14, a3
	rsync

	/* Switch CPENABLE */

#if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
	l32i	a3, a5, THREAD_CPENABLE
	xsr	a3, cpenable
	s32i	a3, a4, THREAD_CPENABLE
#endif

	/* Flush register file. */

	spill_registers_kernel

	/* Set kernel stack (and leave critical section)
	 * Note: It's save to set it here. The stack will not be overwritten
	 *       because the kernel stack will only be loaded again after
	 *       we return from kernel space.
	 */

	rsr	a3, excsave1		# exc_table
	addi	a7, a5, PT_REGS_OFFSET
	s32i	a7, a3, EXC_TABLE_KSTK

	/* restore context of the task 'next' */

	l32i	a0, a11, THREAD_RA	# restore return address
	l32i	a1, a11, THREAD_SP	# restore stack pointer

	load_xtregs_user a5 a6 a8 a9 a12 a13 THREAD_XTREGS_USER

	wsr	a14, ps
	rsync

	abi_ret(XTENSA_SPILL_STACK_RESERVE)

ENDPROC(_switch_to)

ENTRY(ret_from_fork)

	/* void schedule_tail (struct task_struct *prev)
	 * Note: prev is still in a6 (return value from fake call4 frame)
	 */
	call4	schedule_tail

	mov	a6, a1
	call4	do_syscall_trace_leave

	j	common_exception_return

ENDPROC(ret_from_fork)

/*
 * Kernel thread creation helper
 * On entry, set up by copy_thread: a2 = thread_fn, a3 = thread_fn arg
 *           left from _switch_to: a6 = prev
 */
ENTRY(ret_from_kernel_thread)

	call4	schedule_tail
	mov	a6, a3
	callx4	a2
	j	common_exception_return

ENDPROC(ret_from_kernel_thread)