summaryrefslogtreecommitdiff
path: root/arch/xtensa/kernel/vectors.S
blob: 407ece204e7caad11c6f070a28b2977d1b60a7e8 (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
/*
 * arch/xtensa/kernel/vectors.S
 *
 * This file contains all exception vectors (user, kernel, and double),
 * as well as the window vectors (overflow and underflow), and the debug
 * vector. These are the primary vectors executed by the processor if an
 * exception occurs.
 *
 * 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) 2005 - 2008 Tensilica, Inc.
 *
 * Chris Zankel <chris@zankel.net>
 *
 */

/*
 * We use a two-level table approach. The user and kernel exception vectors
 * use a first-level dispatch table to dispatch the exception to a registered
 * fast handler or the default handler, if no fast handler was registered.
 * The default handler sets up a C-stack and dispatches the exception to a
 * registerd C handler in the second-level dispatch table.
 *
 * Fast handler entry condition:
 *
 *   a0:	trashed, original value saved on stack (PT_AREG0)
 *   a1:	a1
 *   a2:	new stack pointer, original value in depc
 *   a3:	dispatch table
 *   depc:	a2, original value saved on stack (PT_DEPC)
 *   excsave_1:	a3
 *
 * The value for PT_DEPC saved to stack also functions as a boolean to
 * indicate that the exception is either a double or a regular exception:
 *
 *   PT_DEPC	>= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception
 *		<  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
 *
 * Note:  Neither the kernel nor the user exception handler generate literals.
 *
 */

#include <linux/linkage.h>
#include <linux/pgtable.h>
#include <asm/asmmacro.h>
#include <asm/ptrace.h>
#include <asm/current.h>
#include <asm/asm-offsets.h>
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/thread_info.h>
#include <asm/vectors.h>

#define WINDOW_VECTORS_SIZE   0x180


/*
 * User exception vector. (Exceptions with PS.UM == 1, PS.EXCM == 0)
 *
 * We get here when an exception occurred while we were in userland.
 * We switch to the kernel stack and jump to the first level handler
 * associated to the exception cause.
 *
 * Note: the saved kernel stack pointer (EXC_TABLE_KSTK) is already
 *       decremented by PT_USER_SIZE.
 */

	.section .UserExceptionVector.text, "ax"

ENTRY(_UserExceptionVector)

	xsr	a3, excsave1		# save a3 and get dispatch table
	wsr	a2, depc		# save a2
	l32i	a2, a3, EXC_TABLE_KSTK	# load kernel stack to a2
	s32i	a0, a2, PT_AREG0	# save a0 to ESF
	rsr	a0, exccause		# retrieve exception cause
	s32i	a0, a2, PT_DEPC		# mark it as a regular exception
	addx4	a0, a0, a3		# find entry in table
	l32i	a0, a0, EXC_TABLE_FAST_USER	# load handler
	xsr	a3, excsave1		# restore a3 and dispatch table
	jx	a0

ENDPROC(_UserExceptionVector)

/*
 * Kernel exception vector. (Exceptions with PS.UM == 0, PS.EXCM == 0)
 *
 * We get this exception when we were already in kernel space.
 * We decrement the current stack pointer (kernel) by PT_SIZE and
 * jump to the first-level handler associated with the exception cause.
 *
 * Note: we need to preserve space for the spill region.
 */

	.section .KernelExceptionVector.text, "ax"

ENTRY(_KernelExceptionVector)

	xsr	a3, excsave1		# save a3, and get dispatch table
	wsr	a2, depc		# save a2
	addi	a2, a1, -16-PT_SIZE	# adjust stack pointer
	s32i	a0, a2, PT_AREG0	# save a0 to ESF
	rsr	a0, exccause		# retrieve exception cause
	s32i	a0, a2, PT_DEPC		# mark it as a regular exception
	addx4	a0, a0, a3		# find entry in table
	l32i	a0, a0, EXC_TABLE_FAST_KERNEL	# load handler address
	xsr	a3, excsave1		# restore a3 and dispatch table
	jx	a0

ENDPROC(_KernelExceptionVector)

/*
 * Double exception vector (Exceptions with PS.EXCM == 1)
 * We get this exception when another exception occurs while were are
 * already in an exception, such as window overflow/underflow exception,
 * or 'expected' exceptions, for example memory exception when we were trying
 * to read data from an invalid address in user space.
 *
 * Note that this vector is never invoked for level-1 interrupts, because such
 * interrupts are disabled (masked) when PS.EXCM is set.
 *
 * We decode the exception and take the appropriate action.  However, the
 * double exception vector is much more careful, because a lot more error
 * cases go through the double exception vector than through the user and
 * kernel exception vectors.
 *
 * Occasionally, the kernel expects a double exception to occur.  This usually
 * happens when accessing user-space memory with the user's permissions
 * (l32e/s32e instructions).  The kernel state, though, is not always suitable
 * for immediate transfer of control to handle_double, where "normal" exception
 * processing occurs. Also in kernel mode, TLB misses can occur if accessing
 * vmalloc memory, possibly requiring repair in a double exception handler.
 *
 * The variable at TABLE_FIXUP offset from the pointer in EXCSAVE_1 doubles as
 * a boolean variable and a pointer to a fixup routine. If the variable
 * EXC_TABLE_FIXUP is non-zero, this handler jumps to that address. A value of
 * zero indicates to use the default kernel/user exception handler.
 * There is only one exception, when the value is identical to the exc_table
 * label, the kernel is in trouble. This mechanism is used to protect critical
 * sections, mainly when the handler writes to the stack to assert the stack
 * pointer is valid. Once the fixup/default handler leaves that area, the
 * EXC_TABLE_FIXUP variable is reset to the fixup handler or zero.
 *
 * Procedures wishing to use this mechanism should set EXC_TABLE_FIXUP to the
 * nonzero address of a fixup routine before it could cause a double exception
 * and reset it before it returns.
 *
 * Some other things to take care of when a fast exception handler doesn't
 * specify a particular fixup handler but wants to use the default handlers:
 *
 *  - The original stack pointer (in a1) must not be modified. The fast
 *    exception handler should only use a2 as the stack pointer.
 *
 *  - If the fast handler manipulates the stack pointer (in a2), it has to
 *    register a valid fixup handler and cannot use the default handlers.
 *
 *  - The handler can use any other generic register from a3 to a15, but it
 *    must save the content of these registers to stack (PT_AREG3...PT_AREGx)
 *
 *  - These registers must be saved before a double exception can occur.
 *
 *  - If we ever implement handling signals while in double exceptions, the
 *    number of registers a fast handler has saved (excluding a0 and a1) must
 *    be written to  PT_AREG1. (1 if only a3 is used, 2 for a3 and a4, etc. )
 *
 * The fixup handlers are special handlers:
 *
 *  - Fixup entry conditions differ from regular exceptions:
 *
 *	a0:	   DEPC
 *	a1: 	   a1
 *	a2:	   trashed, original value in EXC_TABLE_DOUBLE_SAVE
 *	a3:	   exctable
 *	depc:	   a0
 *	excsave_1: a3
 *
 *  - When the kernel enters the fixup handler, it still assumes it is in a
 *    critical section, so EXC_TABLE_FIXUP variable is set to exc_table.
 *    The fixup handler, therefore, has to re-register itself as the fixup
 *    handler before it returns from the double exception.
 *
 *  - Fixup handler can share the same exception frame with the fast handler.
 *    The kernel stack pointer is not changed when entering the fixup handler.
 *
 *  - Fixup handlers can jump to the default kernel and user exception
 *    handlers. Before it jumps, though, it has to setup a exception frame
 *    on stack. Because the default handler resets the register fixup handler
 *    the fixup handler must make sure that the default handler returns to
 *    it instead of the exception address, so it can re-register itself as
 *    the fixup handler.
 *
 * In case of a critical condition where the kernel cannot recover, we jump
 * to unrecoverable_exception with the following entry conditions.
 * All registers a0...a15 are unchanged from the last exception, except:
 *
 *	a0:	   last address before we jumped to the unrecoverable_exception.
 *	excsave_1: a0
 *
 *
 * See the handle_alloca_user and spill_registers routines for example clients.
 *
 * FIXME: Note: we currently don't allow signal handling coming from a double
 *        exception, so the item markt with (*) is not required.
 */

	.section .DoubleExceptionVector.text, "ax"

ENTRY(_DoubleExceptionVector)

	xsr	a3, excsave1
	s32i	a2, a3, EXC_TABLE_DOUBLE_SAVE

	/* Check for kernel double exception (usually fatal). */

	rsr	a2, ps
	_bbsi.l	a2, PS_UM_BIT, 1f
	j	.Lksp

	.align	4
	.literal_position
1:
	/* Check if we are currently handling a window exception. */
	/* Note: We don't need to indicate that we enter a critical section. */

	xsr	a0, depc		# get DEPC, save a0

#ifdef SUPPORT_WINDOWED
	movi	a2, WINDOW_VECTORS_VADDR
	_bltu	a0, a2, .Lfixup
	addi	a2, a2, WINDOW_VECTORS_SIZE
	_bgeu	a0, a2, .Lfixup

	/* Window overflow/underflow exception. Get stack pointer. */

	l32i	a2, a3, EXC_TABLE_KSTK

	/* Check for overflow/underflow exception, jump if overflow. */

	bbci.l	a0, 6, _DoubleExceptionVector_WindowOverflow

	/*
	 * Restart window underflow exception.
	 * Currently:
	 *	depc = orig a0,
	 *	a0 = orig DEPC,
	 *	a2 = new sp based on KSTK from exc_table
	 *	a3 = excsave_1
	 *	excsave_1 = orig a3
	 *
	 * We return to the instruction in user space that caused the window
	 * underflow exception. Therefore, we change window base to the value
	 * before we entered the window underflow exception and prepare the
	 * registers to return as if we were coming from a regular exception
	 * by changing depc (in a0).
	 * Note: We can trash the current window frame (a0...a3) and depc!
	 */
_DoubleExceptionVector_WindowUnderflow:
	xsr	a3, excsave1
	wsr	a2, depc		# save stack pointer temporarily
	rsr	a0, ps
	extui	a0, a0, PS_OWB_SHIFT, PS_OWB_WIDTH
	wsr	a0, windowbase
	rsync

	/* We are now in the previous window frame. Save registers again. */

	xsr	a2, depc		# save a2 and get stack pointer
	s32i	a0, a2, PT_AREG0
	xsr	a3, excsave1
	rsr	a0, exccause
	s32i	a0, a2, PT_DEPC		# mark it as a regular exception
	addx4	a0, a0, a3
	xsr	a3, excsave1
	l32i	a0, a0, EXC_TABLE_FAST_USER
	jx	a0

#else
	j	.Lfixup
#endif

	/*
	 * We only allow the ITLB miss exception if we are in kernel space.
	 * All other exceptions are unexpected and thus unrecoverable!
	 */

#ifdef CONFIG_MMU
	.extern fast_second_level_miss_double_kernel

.Lksp:	/* a0: a0, a1: a1, a2: a2, a3: trashed, depc: depc, excsave: a3 */

	rsr	a3, exccause
	beqi	a3, EXCCAUSE_ITLB_MISS, 1f
	addi	a3, a3, -EXCCAUSE_DTLB_MISS
	bnez	a3, .Lunrecoverable
1:	movi	a3, fast_second_level_miss_double_kernel
	jx	a3
#else
.equ	.Lksp,	.Lunrecoverable
#endif

	/* Critical! We can't handle this situation. PANIC! */

	.extern unrecoverable_exception

.Lunrecoverable_fixup:
	l32i	a2, a3, EXC_TABLE_DOUBLE_SAVE
	xsr	a0, depc

.Lunrecoverable:
	rsr	a3, excsave1
	wsr	a0, excsave1
	call0	unrecoverable_exception

.Lfixup:/* Check for a fixup handler or if we were in a critical section. */

	/* a0: depc, a1: a1, a2: trash, a3: exctable, depc: a0, excsave1: a3 */

	/* Enter critical section. */

	l32i	a2, a3, EXC_TABLE_FIXUP
	s32i	a3, a3, EXC_TABLE_FIXUP
	beq	a2, a3, .Lunrecoverable_fixup	# critical section
	beqz	a2, .Ldflt			# no handler was registered

	/* a0: depc, a1: a1, a2: trash, a3: exctable, depc: a0, excsave: a3 */

	jx	a2

.Ldflt:	/* Get stack pointer. */

	l32i	a2, a3, EXC_TABLE_DOUBLE_SAVE
	addi	a2, a2, -PT_USER_SIZE

	/* a0: depc, a1: a1, a2: kstk, a3: exctable, depc: a0, excsave: a3 */

	s32i	a0, a2, PT_DEPC
	l32i	a0, a3, EXC_TABLE_DOUBLE_SAVE
	xsr	a0, depc
	s32i	a0, a2, PT_AREG0

	/* a0: avail, a1: a1, a2: kstk, a3: exctable, depc: a2, excsave: a3 */

	rsr	a0, exccause
	addx4	a0, a0, a3
	xsr	a3, excsave1
	l32i	a0, a0, EXC_TABLE_FAST_USER
	jx	a0

#ifdef SUPPORT_WINDOWED
	/*
	 * Restart window OVERFLOW exception.
	 * Currently:
	 *	depc = orig a0,
	 *	a0 = orig DEPC,
	 *	a2 = new sp based on KSTK from exc_table
	 *	a3 = EXCSAVE_1
	 *	excsave_1 = orig a3
	 *
	 * We return to the instruction in user space that caused the window
	 * overflow exception. Therefore, we change window base to the value
	 * before we entered the window overflow exception and prepare the
	 * registers to return as if we were coming from a regular exception
	 * by changing DEPC (in a0).
	 *
	 * NOTE: We CANNOT trash the current window frame (a0...a3), but we
	 * can clobber depc.
	 *
	 * The tricky part here is that overflow8 and overflow12 handlers
	 * save a0, then clobber a0.  To restart the handler, we have to restore
	 * a0 if the double exception was past the point where a0 was clobbered.
	 *
	 * To keep things simple, we take advantage of the fact all overflow
	 * handlers save a0 in their very first instruction.  If DEPC was past
	 * that instruction, we can safely restore a0 from where it was saved
	 * on the stack.
	 *
	 * a0: depc, a1: a1, a2: kstk, a3: exc_table, depc: a0, excsave1: a3
	 */
_DoubleExceptionVector_WindowOverflow:
	extui	a2, a0, 0, 6	# get offset into 64-byte vector handler
	beqz	a2, 1f		# if at start of vector, don't restore

	addi	a0, a0, -128
	bbsi.l	a0, 8, 1f	# don't restore except for overflow 8 and 12

	/*
	 * This fixup handler is for the extremely unlikely case where the
	 * overflow handler's reference thru a0 gets a hardware TLB refill
	 * that bumps out the (distinct, aliasing) TLB entry that mapped its
	 * prior references thru a9/a13, and where our reference now thru
	 * a9/a13 gets a 2nd-level miss exception (not hardware TLB refill).
	 */
	movi	a2, window_overflow_restore_a0_fixup
	s32i	a2, a3, EXC_TABLE_FIXUP
	l32i	a2, a3, EXC_TABLE_DOUBLE_SAVE
	xsr	a3, excsave1

	bbsi.l	a0, 7, 2f

	/*
	 * Restore a0 as saved by _WindowOverflow8().
	 */

	l32e	a0, a9, -16
	wsr	a0, depc	# replace the saved a0
	j	3f

2:
	/*
	 * Restore a0 as saved by _WindowOverflow12().
	 */

	l32e	a0, a13, -16
	wsr	a0, depc	# replace the saved a0
3:
	xsr	a3, excsave1
	movi	a0, 0
	s32i	a0, a3, EXC_TABLE_FIXUP
	s32i	a2, a3, EXC_TABLE_DOUBLE_SAVE
1:
	/*
	 * Restore WindowBase while leaving all address registers restored.
	 * We have to use ROTW for this, because WSR.WINDOWBASE requires
	 * an address register (which would prevent restore).
	 *
	 * Window Base goes from 0 ... 7 (Module 8)
	 * Window Start is 8 bits; Ex: (0b1010 1010):0x55 from series of call4s
	 */

	rsr	a0, ps
	extui	a0, a0, PS_OWB_SHIFT, PS_OWB_WIDTH
	rsr	a2, windowbase
	sub	a0, a2, a0
	extui	a0, a0, 0, 3

	l32i	a2, a3, EXC_TABLE_DOUBLE_SAVE
	xsr	a3, excsave1
	beqi	a0, 1, .L1pane
	beqi	a0, 3, .L3pane

	rsr	a0, depc
	rotw	-2

	/*
	 * We are now in the user code's original window frame.
	 * Process the exception as a user exception as if it was
	 * taken by the user code.
	 *
	 * This is similar to the user exception vector,
	 * except that PT_DEPC isn't set to EXCCAUSE.
	 */
1:
	xsr	a3, excsave1
	wsr	a2, depc
	l32i	a2, a3, EXC_TABLE_KSTK
	s32i	a0, a2, PT_AREG0
	rsr	a0, exccause

	s32i	a0, a2, PT_DEPC

_DoubleExceptionVector_handle_exception:
	addi	a0, a0, -EXCCAUSE_UNALIGNED
	beqz	a0, 2f
	addx4	a0, a0, a3
	l32i	a0, a0, EXC_TABLE_FAST_USER + 4 * EXCCAUSE_UNALIGNED
	xsr	a3, excsave1
	jx	a0
2:
	movi	a0, user_exception
	xsr	a3, excsave1
	jx	a0

.L1pane:
	rsr	a0, depc
	rotw	-1
	j	1b

.L3pane:
	rsr	a0, depc
	rotw	-3
	j	1b
#endif

ENDPROC(_DoubleExceptionVector)

#ifdef SUPPORT_WINDOWED

/*
 * Fixup handler for TLB miss in double exception handler for window owerflow.
 * We get here with windowbase set to the window that was being spilled and
 * a0 trashed. a0 bit 7 determines if this is a call8 (bit clear) or call12
 * (bit set) window.
 *
 * We do the following here:
 * - go to the original window retaining a0 value;
 * - set up exception stack to return back to appropriate a0 restore code
 *   (we'll need to rotate window back and there's no place to save this
 *    information, use different return address for that);
 * - handle the exception;
 * - go to the window that was being spilled;
 * - set up window_overflow_restore_a0_fixup as a fixup routine;
 * - reload a0;
 * - restore the original window;
 * - reset the default fixup routine;
 * - return to user. By the time we get to this fixup handler all information
 *   about the conditions of the original double exception that happened in
 *   the window overflow handler is lost, so we just return to userspace to
 *   retry overflow from start.
 *
 * a0: value of depc, original value in depc
 * a2: trashed, original value in EXC_TABLE_DOUBLE_SAVE
 * a3: exctable, original value in excsave1
 */

	__XTENSA_HANDLER
	.literal_position

ENTRY(window_overflow_restore_a0_fixup)

	rsr	a0, ps
	extui	a0, a0, PS_OWB_SHIFT, PS_OWB_WIDTH
	rsr	a2, windowbase
	sub	a0, a2, a0
	extui	a0, a0, 0, 3
	l32i	a2, a3, EXC_TABLE_DOUBLE_SAVE
	xsr	a3, excsave1

	_beqi	a0, 1, .Lhandle_1
	_beqi	a0, 3, .Lhandle_3

	.macro	overflow_fixup_handle_exception_pane n

	rsr	a0, depc
	rotw	-\n

	xsr	a3, excsave1
	wsr	a2, depc
	l32i	a2, a3, EXC_TABLE_KSTK
	s32i	a0, a2, PT_AREG0

	movi	a0, .Lrestore_\n
	s32i	a0, a2, PT_DEPC
	rsr	a0, exccause
	j	_DoubleExceptionVector_handle_exception

	.endm

	overflow_fixup_handle_exception_pane 2
.Lhandle_1:
	overflow_fixup_handle_exception_pane 1
.Lhandle_3:
	overflow_fixup_handle_exception_pane 3

	.macro	overflow_fixup_restore_a0_pane n

	rotw	\n
	/* Need to preserve a0 value here to be able to handle exception
	 * that may occur on a0 reload from stack. It may occur because
	 * TLB miss handler may not be atomic and pointer to page table
	 * may be lost before we get here. There are no free registers,
	 * so we need to use EXC_TABLE_DOUBLE_SAVE area.
	 */
	xsr	a3, excsave1
	s32i	a2, a3, EXC_TABLE_DOUBLE_SAVE
	movi	a2, window_overflow_restore_a0_fixup
	s32i	a2, a3, EXC_TABLE_FIXUP
	l32i	a2, a3, EXC_TABLE_DOUBLE_SAVE
	xsr	a3, excsave1
	bbsi.l	a0, 7, 1f
	l32e	a0, a9, -16
	j	2f
1:
	l32e	a0, a13, -16
2:
	rotw	-\n

	.endm

.Lrestore_2:
	overflow_fixup_restore_a0_pane 2

.Lset_default_fixup:
	xsr	a3, excsave1
	s32i	a2, a3, EXC_TABLE_DOUBLE_SAVE
	movi	a2, 0
	s32i	a2, a3, EXC_TABLE_FIXUP
	l32i	a2, a3, EXC_TABLE_DOUBLE_SAVE
	xsr	a3, excsave1
	rfe

.Lrestore_1:
	overflow_fixup_restore_a0_pane 1
	j	.Lset_default_fixup
.Lrestore_3:
	overflow_fixup_restore_a0_pane 3
	j	.Lset_default_fixup

ENDPROC(window_overflow_restore_a0_fixup)

#endif

/*
 * Debug interrupt vector
 *
 * There is not much space here, so simply jump to another handler.
 * EXCSAVE[DEBUGLEVEL] has been set to that handler.
 */

	.section .DebugInterruptVector.text, "ax"

ENTRY(_DebugInterruptVector)

	xsr	a3, SREG_EXCSAVE + XCHAL_DEBUGLEVEL
	s32i	a0, a3, DT_DEBUG_SAVE
	l32i	a0, a3, DT_DEBUG_EXCEPTION
	jx	a0

ENDPROC(_DebugInterruptVector)



/*
 * Medium priority level interrupt vectors
 *
 * Each takes less than 16 (0x10) bytes, no literals, by placing
 * the extra 8 bytes that would otherwise be required in the window
 * vectors area where there is space.  With relocatable vectors,
 * all vectors are within ~ 4 kB range of each other, so we can
 * simply jump (J) to another vector without having to use JX.
 *
 * common_exception code gets current IRQ level in PS.INTLEVEL
 * and preserves it for the IRQ handling time.
 */

	.macro	irq_entry_level level

	.if	XCHAL_EXCM_LEVEL >= \level
	.section .Level\level\()InterruptVector.text, "ax"
ENTRY(_Level\level\()InterruptVector)
	wsr	a0, excsave2
	rsr	a0, epc\level
	wsr	a0, epc1
	.if	\level <= LOCKLEVEL
	movi	a0, EXCCAUSE_LEVEL1_INTERRUPT
	.else
	movi	a0, EXCCAUSE_MAPPED_NMI
	.endif
	wsr	a0, exccause
	rsr	a0, eps\level
					# branch to user or kernel vector
	j	_SimulateUserKernelVectorException
	.endif

	.endm

	irq_entry_level 2
	irq_entry_level 3
	irq_entry_level 4
	irq_entry_level 5
	irq_entry_level 6

#if XCHAL_EXCM_LEVEL >= 2
	/*
	 *  Continuation of medium priority interrupt dispatch code.
	 *  On entry here, a0 contains PS, and EPC2 contains saved a0:
	 */
	__XTENSA_HANDLER
	.align 4
_SimulateUserKernelVectorException:
	addi	a0, a0, (1 << PS_EXCM_BIT)
#if !XTENSA_FAKE_NMI
	wsr	a0, ps
#endif
	bbsi.l	a0, PS_UM_BIT, 1f	# branch if user mode
	xsr	a0, excsave2		# restore a0
	j	_KernelExceptionVector	# simulate kernel vector exception
1:	xsr	a0, excsave2		# restore a0
	j	_UserExceptionVector	# simulate user vector exception
#endif


/* Window overflow and underflow handlers.
 * The handlers must be 64 bytes apart, first starting with the underflow
 * handlers underflow-4 to underflow-12, then the overflow handlers
 * overflow-4 to overflow-12.
 *
 * Note: We rerun the underflow handlers if we hit an exception, so
 *	 we try to access any page that would cause a page fault early.
 */

#define ENTRY_ALIGN64(name)	\
	.globl name;		\
	.align 64;		\
	name:

	.section		.WindowVectors.text, "ax"


#ifdef SUPPORT_WINDOWED

/* 4-Register Window Overflow Vector (Handler) */

ENTRY_ALIGN64(_WindowOverflow4)

	s32e	a0, a5, -16
	s32e	a1, a5, -12
	s32e	a2, a5,  -8
	s32e	a3, a5,  -4
	rfwo

ENDPROC(_WindowOverflow4)

/* 4-Register Window Underflow Vector (Handler) */

ENTRY_ALIGN64(_WindowUnderflow4)

	l32e	a0, a5, -16
	l32e	a1, a5, -12
	l32e	a2, a5,  -8
	l32e	a3, a5,  -4
	rfwu

ENDPROC(_WindowUnderflow4)

/* 8-Register Window Overflow Vector (Handler) */

ENTRY_ALIGN64(_WindowOverflow8)

	s32e	a0, a9, -16
	l32e	a0, a1, -12
	s32e	a2, a9,  -8
	s32e	a1, a9, -12
	s32e	a3, a9,  -4
	s32e	a4, a0, -32
	s32e	a5, a0, -28
	s32e	a6, a0, -24
	s32e	a7, a0, -20
	rfwo

ENDPROC(_WindowOverflow8)

/* 8-Register Window Underflow Vector (Handler) */

ENTRY_ALIGN64(_WindowUnderflow8)

	l32e	a1, a9, -12
	l32e	a0, a9, -16
	l32e	a7, a1, -12
	l32e	a2, a9,  -8
	l32e	a4, a7, -32
	l32e	a3, a9,  -4
	l32e	a5, a7, -28
	l32e	a6, a7, -24
	l32e	a7, a7, -20
	rfwu

ENDPROC(_WindowUnderflow8)

/* 12-Register Window Overflow Vector (Handler) */

ENTRY_ALIGN64(_WindowOverflow12)

	s32e	a0,  a13, -16
	l32e	a0,  a1,  -12
	s32e	a1,  a13, -12
	s32e	a2,  a13,  -8
	s32e	a3,  a13,  -4
	s32e	a4,  a0,  -48
	s32e	a5,  a0,  -44
	s32e	a6,  a0,  -40
	s32e	a7,  a0,  -36
	s32e	a8,  a0,  -32
	s32e	a9,  a0,  -28
	s32e	a10, a0,  -24
	s32e	a11, a0,  -20
	rfwo

ENDPROC(_WindowOverflow12)

/* 12-Register Window Underflow Vector (Handler) */

ENTRY_ALIGN64(_WindowUnderflow12)

	l32e	a1,  a13, -12
	l32e	a0,  a13, -16
	l32e	a11, a1,  -12
	l32e	a2,  a13,  -8
	l32e	a4,  a11, -48
	l32e	a8,  a11, -32
	l32e	a3,  a13,  -4
	l32e	a5,  a11, -44
	l32e	a6,  a11, -40
	l32e	a7,  a11, -36
	l32e	a9,  a11, -28
	l32e	a10, a11, -24
	l32e	a11, a11, -20
	rfwu

ENDPROC(_WindowUnderflow12)

#endif

	.text