summaryrefslogtreecommitdiffstats
path: root/arch/sh/kernel/entry.S
blob: fe8221855b282648f25472cd64286814728f7843 (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
/* $Id: entry.S,v 1.37 2004/06/11 13:02:46 doyu Exp $
 *
 *  linux/arch/sh/entry.S
 *
 *  Copyright (C) 1999, 2000, 2002  Niibe Yutaka
 *  Copyright (C) 2003  Paul Mundt
 *
 * 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.
 *
 */

#include <linux/sys.h>
#include <linux/linkage.h>
#include <asm/asm-offsets.h>
#include <asm/thread_info.h>
#include <asm/cpu/mmu_context.h>
#include <asm/unistd.h>

! NOTE:
! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
! to be jumped is too far, but it causes illegal slot exception.

/*	
 * entry.S contains the system-call and fault low-level handling routines.
 * This also contains the timer-interrupt handler, as well as all interrupts
 * and faults that can result in a task-switch.
 *
 * NOTE: This code handles signal-recognition, which happens every time
 * after a timer-interrupt and after each system call.
 *
 * NOTE: This code uses a convention that instructions in the delay slot
 * of a transfer-control instruction are indented by an extra space, thus:
 *
 *    jmp	@k0	    ! control-transfer instruction
 *     ldc	k1, ssr     ! delay slot
 *
 * Stack layout in 'ret_from_syscall':
 * 	ptrace needs to have all regs on the stack.
 *	if the order here is changed, it needs to be
 *	updated in ptrace.c and ptrace.h
 *
 *	r0
 *      ...
 *	r15 = stack pointer
 *	spc
 *	pr
 *	ssr
 *	gbr
 *	mach
 *	macl
 *	syscall #
 *
 */

ENOSYS = 38
EINVAL = 22

#if defined(CONFIG_KGDB_NMI)
NMI_VEC = 0x1c0			! Must catch early for debounce
#endif

/* Offsets to the stack */
OFF_R0  =  0		/* Return value. New ABI also arg4 */
OFF_R1  =  4     	/* New ABI: arg5 */
OFF_R2  =  8     	/* New ABI: arg6 */
OFF_R3  =  12     	/* New ABI: syscall_nr */
OFF_R4  =  16     	/* New ABI: arg0 */
OFF_R5  =  20     	/* New ABI: arg1 */
OFF_R6  =  24     	/* New ABI: arg2 */
OFF_R7  =  28     	/* New ABI: arg3 */
OFF_SP	=  (15*4)
OFF_PC  =  (16*4)
OFF_SR	=  (16*4+8)
OFF_TRA	=  (16*4+6*4)


#define k0	r0
#define k1	r1
#define k2	r2
#define k3	r3
#define k4	r4

#define k_ex_code	r2_bank	/* r2_bank1 */
#define g_imask		r6	/* r6_bank1 */
#define k_g_imask	r6_bank	/* r6_bank1 */
#define current		r7	/* r7_bank1 */

/*
 * Kernel mode register usage:
 *	k0	scratch
 *	k1	scratch
 *	k2	scratch (Exception code)
 *	k3	scratch (Return address)
 *	k4	scratch
 *	k5	reserved
 *	k6	Global Interrupt Mask (0--15 << 4)
 *	k7	CURRENT_THREAD_INFO (pointer to current thread info)
 */

!
! TLB Miss / Initial Page write exception handling
!			_and_
! TLB hits, but the access violate the protection.
! It can be valid access, such as stack grow and/or C-O-W.
!
!
! Find the pmd/pte entry and loadtlb
! If it's not found, cause address error (SEGV)
!
! Although this could be written in assembly language (and it'd be faster),
! this first version depends *much* on C implementation.
!

#define CLI()				\
	stc	sr, r0;			\
	or	#0xf0, r0;		\
	ldc	r0, sr

#define STI()				\
	mov.l	__INV_IMASK, r11;	\
	stc	sr, r10;		\
	and	r11, r10;		\
	stc	k_g_imask, r11;		\
	or	r11, r10;		\
	ldc	r10, sr

#if defined(CONFIG_PREEMPT)
#  define preempt_stop()	CLI()
#else
#  define preempt_stop()
#  define resume_kernel		restore_all
#endif

#if defined(CONFIG_MMU)
	.align	2
ENTRY(tlb_miss_load)
	bra	call_dpf
	 mov	#0, r5

	.align	2
ENTRY(tlb_miss_store)
	bra	call_dpf
	 mov	#1, r5

	.align	2
ENTRY(initial_page_write)
	bra	call_dpf
	 mov	#1, r5

	.align	2
ENTRY(tlb_protection_violation_load)
	bra	call_dpf
	 mov	#0, r5

	.align	2
ENTRY(tlb_protection_violation_store)
	bra	call_dpf
	 mov	#1, r5

call_dpf:
	mov.l	1f, r0
	mov	r5, r8
	mov.l	@r0, r6
	mov	r6, r9
	mov.l	2f, r0
	sts	pr, r10
	jsr	@r0
	 mov	r15, r4
	!
	tst	r0, r0
	bf/s	0f
	 lds	r10, pr
	rts
	 nop
0:	STI()
	mov.l	3f, r0
	mov	r9, r6
	mov	r8, r5
	jmp	@r0
	 mov	r15, r4

	.align 2
1:	.long	MMU_TEA
2:	.long	__do_page_fault
3:	.long	do_page_fault

	.align	2
ENTRY(address_error_load)
	bra	call_dae
	 mov	#0,r5		! writeaccess = 0

	.align	2
ENTRY(address_error_store)
	bra	call_dae
	 mov	#1,r5		! writeaccess = 1

	.align	2
call_dae:
	mov.l	1f, r0
	mov.l	@r0, r6		! address
	mov.l	2f, r0
	jmp	@r0
	 mov	r15, r4		! regs

	.align 2
1:	.long	MMU_TEA
2:	.long   do_address_error
#endif /* CONFIG_MMU */

#if defined(CONFIG_SH_STANDARD_BIOS) || defined(CONFIG_SH_KGDB)
! Handle kernel debug if either kgdb (SW) or gdb-stub (FW) is present.
! If both are configured, handle the debug traps (breakpoints) in SW,
! but still allow BIOS traps to FW.

	.align	2
debug_kernel:
#if defined(CONFIG_SH_STANDARD_BIOS) && defined(CONFIG_SH_KGDB)
	/* Force BIOS call to FW (debug_trap put TRA in r8) */
	mov	r8,r0
	shlr2	r0
	cmp/eq	#0x3f,r0
	bt	debug_kernel_fw
#endif /* CONFIG_SH_STANDARD_BIOS && CONFIG_SH_KGDB */

debug_enter:		
#if defined(CONFIG_SH_KGDB)
	/* Jump to kgdb, pass stacked regs as arg */
debug_kernel_sw:
	mov.l	3f, r0
	jmp	@r0
	 mov	r15, r4
	.align	2
3:	.long	kgdb_handle_exception
#endif /* CONFIG_SH_KGDB */

#if defined(CONFIG_SH_STANDARD_BIOS)
	/* Unwind the stack and jmp to the debug entry */
debug_kernel_fw:
	mov.l	@r15+, r0
	mov.l	@r15+, r1
	mov.l	@r15+, r2
	mov.l	@r15+, r3
	mov.l	@r15+, r4
	mov.l	@r15+, r5
	mov.l	@r15+, r6
	mov.l	@r15+, r7
	stc	sr, r8
	mov.l	1f, r9			! BL =1, RB=1, IMASK=0x0F
	or	r9, r8
	ldc	r8, sr			! here, change the register bank
	mov.l	@r15+, r8
	mov.l	@r15+, r9
	mov.l	@r15+, r10
	mov.l	@r15+, r11
	mov.l	@r15+, r12
	mov.l	@r15+, r13
	mov.l	@r15+, r14
	mov.l	@r15+, k0
	ldc.l	@r15+, spc
	lds.l	@r15+, pr
	mov.l	@r15+, k1
	ldc.l	@r15+, gbr
	lds.l	@r15+, mach
	lds.l	@r15+, macl
	mov	k0, r15
	!
	mov.l	2f, k0
	mov.l	@k0, k0
	jmp	@k0
	 ldc	k1, ssr
	.align	2
1:	.long	0x300000f0
2:	.long	gdb_vbr_vector
#endif /* CONFIG_SH_STANDARD_BIOS */

#endif /* CONFIG_SH_STANDARD_BIOS || CONFIG_SH_KGDB */


	.align	2
debug_trap:	
#if defined(CONFIG_SH_STANDARD_BIOS) || defined(CONFIG_SH_KGDB)
	mov	#OFF_SR, r0
	mov.l	@(r0,r15), r0		! get status register
	shll	r0
	shll	r0			! kernel space?
	bt/s	debug_kernel
#endif
	 mov.l	@r15, r0		! Restore R0 value
	mov.l	1f, r8
	jmp	@r8
	 nop

	.align	2
ENTRY(exception_error)
	!
	STI()
	mov.l	2f, r0
	jmp	@r0
	 nop

!
	.align	2
1:	.long	break_point_trap_software
2:	.long	do_exception_error

	.align	2
ret_from_exception:
	preempt_stop()
ENTRY(ret_from_irq)
	!
	mov	#OFF_SR, r0
	mov.l	@(r0,r15), r0	! get status register
	shll	r0
	shll	r0		! kernel space?
	bt/s	resume_kernel	! Yes, it's from kernel, go back soon
	 GET_THREAD_INFO(r8)

#ifdef CONFIG_PREEMPT
	bra	resume_userspace
	 nop
ENTRY(resume_kernel)
	mov.l	@(TI_PRE_COUNT,r8), r0	! current_thread_info->preempt_count
	tst	r0, r0
	bf	noresched
need_resched:
	mov.l	@(TI_FLAGS,r8), r0	! current_thread_info->flags
	tst	#_TIF_NEED_RESCHED, r0	! need_resched set?
	bt	noresched

	mov	#OFF_SR, r0
	mov.l	@(r0,r15), r0		! get status register
	and	#0xf0, r0		! interrupts off (exception path)?
	cmp/eq	#0xf0, r0
	bt	noresched

	mov.l	1f, r0
	mov.l	r0, @(TI_PRE_COUNT,r8)

	STI()
	mov.l	2f, r0
	jsr	@r0
	 nop
	mov	#0, r0
	mov.l	r0, @(TI_PRE_COUNT,r8)
	CLI()

	bra	need_resched
	 nop
noresched:
	bra	restore_all
	 nop

	.align 2
1:	.long	PREEMPT_ACTIVE
2:	.long	schedule
#endif

ENTRY(resume_userspace)
	! r8: current_thread_info
	CLI()
	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
	tst	#_TIF_WORK_MASK, r0
	bt/s	restore_all
	 tst	#_TIF_NEED_RESCHED, r0

	.align	2
work_pending:
	! r0: current_thread_info->flags
	! r8: current_thread_info
	! t:  result of "tst	#_TIF_NEED_RESCHED, r0"
	bf/s	work_resched
	 tst	#(_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK), r0
work_notifysig:
	bt/s	restore_all
	 mov	r15, r4
	mov	r12, r5		! set arg1(save_r0)
	mov	r0, r6
	mov.l	2f, r1
	mova	restore_all, r0
	jmp	@r1
	 lds	r0, pr
work_resched:
#ifndef CONFIG_PREEMPT
	! gUSA handling
	mov.l	@(OFF_SP,r15), r0	! get user space stack pointer
	mov	r0, r1
	shll	r0
	bf/s	1f
	 shll	r0
	bf/s	1f
	 mov	#OFF_PC, r0
	! 				  SP >= 0xc0000000 : gUSA mark
	mov.l	@(r0,r15), r2		! get user space PC (program counter)
	mov.l	@(OFF_R0,r15), r3	! end point
	cmp/hs	r3, r2			! r2 >= r3? 
	bt	1f
	add	r3, r1			! rewind point #2
	mov.l	r1, @(r0,r15)		! reset PC to rewind point #2
	!
1:
#endif
	mov.l	1f, r1
	jsr	@r1				! schedule
	 nop
	CLI()
	!
	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
	tst	#_TIF_WORK_MASK, r0
	bt	restore_all
	bra	work_pending
	 tst	#_TIF_NEED_RESCHED, r0

	.align	2
1:	.long	schedule
2:	.long	do_notify_resume

	.align	2
syscall_exit_work:
	! r0: current_thread_info->flags
	! r8: current_thread_info
	tst	#_TIF_SYSCALL_TRACE, r0
	bt/s	work_pending
	 tst	#_TIF_NEED_RESCHED, r0
	STI()
	! XXX setup arguments...
	mov.l	4f, r0			! do_syscall_trace
	jsr	@r0
	 nop
	bra	resume_userspace
	 nop

	.align	2
syscall_trace_entry:
	!                     	Yes it is traced.
	! XXX setup arguments...
	mov.l	4f, r11		! Call do_syscall_trace which notifies
	jsr	@r11	    	! superior (will chomp R[0-7])
	 nop
	!			Reload R0-R4 from kernel stack, where the
	!   	    	    	parent may have modified them using
	!   	    	    	ptrace(POKEUSR).  (Note that R0-R2 are
	!   	    	    	used by the system call handler directly
	!   	    	    	from the kernel stack anyway, so don't need
	!   	    	    	to be reloaded here.)  This allows the parent
	!   	    	    	to rewrite system calls and args on the fly.
	mov.l	@(OFF_R4,r15), r4   ! arg0
	mov.l	@(OFF_R5,r15), r5
	mov.l	@(OFF_R6,r15), r6
	mov.l	@(OFF_R7,r15), r7   ! arg3
	mov.l	@(OFF_R3,r15), r3   ! syscall_nr
	!   	    	    Arrange for do_syscall_trace to be called
	!   	    	    again as the system call returns.
	mov.l	2f, r10			! Number of syscalls
	cmp/hs	r10, r3
	bf	syscall_call
	mov	#-ENOSYS, r0
	bra	syscall_exit
	 mov.l	r0, @(OFF_R0,r15)	! Return value

/*
 * Syscall interface:
 *
 *	Syscall #: R3
 *	Arguments #0 to #3: R4--R7
 *	Arguments #4 to #6: R0, R1, R2
 *	TRA: (number of arguments + 0x10) x 4
 *
 * This code also handles delegating other traps to the BIOS/gdb stub
 * according to:
 *
 * Trap number
 * (TRA>>2) 	    Purpose
 * -------- 	    -------
 * 0x0-0xf  	    old syscall ABI
 * 0x10-0x1f  	    new syscall ABI
 * 0x20-0xff  	    delegated through debug_trap to BIOS/gdb stub.
 *
 * Note: When we're first called, the TRA value must be shifted
 * right 2 bits in order to get the value that was used as the "trapa"
 * argument.
 */

	.align	2
	.globl	ret_from_fork
ret_from_fork:
	mov.l	1f, r8
	jsr	@r8
	 mov	r0, r4
	bra	syscall_exit
	 nop
	.align	2
1:	.long	schedule_tail
	!
ENTRY(system_call)
	mov.l	1f, r9
	mov.l	@r9, r8		! Read from TRA (Trap Address) Register
	!
	! Is the trap argument >= 0x20? (TRA will be >= 0x80)
	mov	#0x7f, r9
	cmp/hi	r9, r8
	bt/s	0f
	 mov	#OFF_TRA, r9
	add	r15, r9
	!
	mov.l	r8, @r9			! set TRA value to tra
	STI()
	!   	    	    Call the system call handler through the table.
	!   	    	    First check for bad syscall number
	mov	r3, r9
	mov.l	2f, r8			! Number of syscalls
	cmp/hs	r8, r9
	bf/s	good_system_call
	 GET_THREAD_INFO(r8)
syscall_badsys:			! Bad syscall number
	mov	#-ENOSYS, r0
	bra	resume_userspace
	 mov.l	r0, @(OFF_R0,r15)	! Return value
	!
0:
	bra	debug_trap
	 nop
	!
good_system_call:		! Good syscall number
	mov.l	@(TI_FLAGS,r8), r8
	mov	#_TIF_SYSCALL_TRACE, r10
	tst	r10, r8
	bf	syscall_trace_entry
	!
syscall_call:
	shll2	r9		! x4
	mov.l	3f, r8		! Load the address of sys_call_table
	add	r8, r9
	mov.l	@r9, r8
	jsr	@r8	    	! jump to specific syscall handler
	 nop
	mov.l	@(OFF_R0,r15), r12		! save r0
	mov.l	r0, @(OFF_R0,r15)		! save the return value
	!
syscall_exit:
	CLI()
	!
	GET_THREAD_INFO(r8)
	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
	tst	#_TIF_ALLWORK_MASK, r0
	bf	syscall_exit_work
restore_all:
	mov.l	@r15+, r0
	mov.l	@r15+, r1
	mov.l	@r15+, r2
	mov.l	@r15+, r3
	mov.l	@r15+, r4
	mov.l	@r15+, r5
	mov.l	@r15+, r6
	mov.l	@r15+, r7
	!
	stc	sr, r8
	mov.l	7f, r9
	or	r9, r8			! BL =1, RB=1
	ldc	r8, sr			! here, change the register bank
	!
	mov.l	@r15+, r8
	mov.l	@r15+, r9
	mov.l	@r15+, r10
	mov.l	@r15+, r11
	mov.l	@r15+, r12
	mov.l	@r15+, r13
	mov.l	@r15+, r14
	mov.l	@r15+, k4		! original stack pointer
	ldc.l	@r15+, spc
	lds.l	@r15+, pr
	mov.l	@r15+, k3		! original SR
	ldc.l	@r15+, gbr
	lds.l	@r15+, mach
	lds.l	@r15+, macl
	add	#4, r15			! Skip syscall number
	!
#ifdef CONFIG_SH_DSP
	mov.l	@r15+, k0		! DSP mode marker
	mov.l	5f, k1
	cmp/eq	k0, k1			! Do we have a DSP stack frame?
	bf	skip_restore

	stc	sr, k0			! Enable CPU DSP mode
	or	k1, k0			! (within kernel it may be disabled)
	ldc	k0, sr
	mov	r2, k0			! Backup r2

	! Restore DSP registers from stack
	mov	r15, r2
	movs.l	@r2+, a1
	movs.l	@r2+, a0g
	movs.l	@r2+, a1g
	movs.l	@r2+, m0
	movs.l	@r2+, m1
	mov	r2, r15

	lds.l	@r15+, a0
	lds.l	@r15+, x0
	lds.l	@r15+, x1
	lds.l	@r15+, y0
	lds.l	@r15+, y1
	lds.l	@r15+, dsr
	ldc.l	@r15+, rs
	ldc.l	@r15+, re
	ldc.l	@r15+, mod

	mov	k0, r2			! Restore r2
skip_restore:
#endif
	!
	! Calculate new SR value
	mov	k3, k2			! original SR value
	mov.l	9f, k1
	and	k1, k2			! Mask orignal SR value
	!
	mov	k3, k0			! Calculate IMASK-bits
	shlr2	k0
	and	#0x3c, k0
	cmp/eq	#0x3c, k0
	bt/s	6f
	 shll2	k0
	mov	g_imask, k0
	!
6:	or	k0, k2			! Set the IMASK-bits
	ldc	k2, ssr
	!
#if defined(CONFIG_KGDB_NMI)
	! Clear in_nmi
	mov.l	6f, k0
	mov	#0, k1
	mov.b	k1, @k0
#endif
	mov.l	@r15+, k2		! restore EXPEVT
	mov	k4, r15
	rte
	 nop

	.align	2
1:	.long	TRA
2:	.long	NR_syscalls
3:	.long	sys_call_table
4:	.long	do_syscall_trace
5:	.long	0x00001000	! DSP
7:	.long	0x30000000
9:
__INV_IMASK:
	.long	0xffffff0f	! ~(IMASK)

! Exception Vector Base
!
!	Should be aligned page boundary.
!
	.balign 	4096,0,4096
ENTRY(vbr_base)
	.long	0
!
	.balign 	256,0,256
general_exception:
	mov.l	1f, k2
	mov.l	2f, k3
	bra	handle_exception
	 mov.l	@k2, k2
	.align	2
1:	.long	EXPEVT
2:	.long	ret_from_exception
!
!
	.balign 	1024,0,1024
tlb_miss:
	mov.l	1f, k2
	mov.l	4f, k3
	bra	handle_exception
	 mov.l	@k2, k2
!
	.balign 	512,0,512
interrupt:
	mov.l	2f, k2
	mov.l	3f, k3
#if defined(CONFIG_KGDB_NMI)
	! Debounce (filter nested NMI)
	mov.l	@k2, k0
	mov.l	5f, k1
	cmp/eq	k1, k0
	bf	0f
	mov.l	6f, k1
	tas.b	@k1
	bt	0f
	rte
	 nop
	.align	2
5:	.long	NMI_VEC
6:	.long	in_nmi
0:
#endif /* defined(CONFIG_KGDB_NMI) */
	bra	handle_exception
	 mov.l	@k2, k2

	.align	2
1:	.long	EXPEVT
2:	.long	INTEVT
3:	.long	ret_from_irq
4:	.long	ret_from_exception

!
!
	.align	2
ENTRY(handle_exception)
	! Using k0, k1 for scratch registers (r0_bank1, r1_bank),
	! save all registers onto stack.
	!
	stc	ssr, k0		! Is it from kernel space?
	shll	k0		! Check MD bit (bit30) by shifting it into...
	shll	k0		!       ...the T bit
	bt/s	1f		! It's a kernel to kernel transition.
	 mov	r15, k0		! save original stack to k0
	/* User space to kernel */
	mov	#(THREAD_SIZE >> 8), k1
	shll8	k1		! k1 := THREAD_SIZE
	add	current, k1
	mov	k1, r15		! change to kernel stack
	!
1:  	mov	#-1, k4
	mov.l	2f, k1
	!
#ifdef CONFIG_SH_DSP
	mov.l	r2, @-r15		! Save r2, we need another reg
	stc	sr, k4
	mov.l	1f, r2
	tst	r2, k4			! Check if in DSP mode
	mov.l	@r15+, r2		! Restore r2 now
	bt/s	skip_save
	 mov	#0, k4			! Set marker for no stack frame

	mov	r2, k4			! Backup r2 (in k4) for later

	! Save DSP registers on stack
	stc.l	mod, @-r15
	stc.l	re, @-r15
	stc.l	rs, @-r15
	sts.l	dsr, @-r15
	sts.l	y1, @-r15
	sts.l	y0, @-r15
	sts.l	x1, @-r15
	sts.l	x0, @-r15
	sts.l	a0, @-r15

	! GAS is broken, does not generate correct "movs.l Ds,@-As" instr.

	! FIXME: Make sure that this is still the case with newer toolchains,
	! as we're not at all interested in supporting ancient toolchains at
	! this point. -- PFM.

	mov	r15, r2
	.word	0xf653			! movs.l	a1, @-r2
	.word	0xf6f3			! movs.l	a0g, @-r2
	.word	0xf6d3			! movs.l	a1g, @-r2
	.word	0xf6c3			! movs.l	m0, @-r2
	.word	0xf6e3			! movs.l	m1, @-r2
	mov	r2, r15

	mov	k4, r2			! Restore r2
	mov.l	1f, k4			! Force DSP stack frame
skip_save:
	mov.l	k4, @-r15		! Push DSP mode marker onto stack
#endif
	! Save the user registers on the stack.
	mov.l	k2, @-r15	! EXPEVT
	mov.l	k4, @-r15	! set TRA (default: -1)
	!
	sts.l	macl, @-r15
	sts.l	mach, @-r15
	stc.l	gbr, @-r15
	stc.l	ssr, @-r15
	sts.l	pr, @-r15
	stc.l	spc, @-r15
	!
	lds	k3, pr		! Set the return address to pr
	!
	mov.l	k0, @-r15	! save orignal stack
	mov.l	r14, @-r15
	mov.l	r13, @-r15
	mov.l	r12, @-r15
	mov.l	r11, @-r15
	mov.l	r10, @-r15
	mov.l	r9, @-r15
	mov.l	r8, @-r15
	!
	stc	sr, r8		! Back to normal register bank, and
	or	k1, r8		! Block all interrupts
	mov.l	3f, k1
	and	k1, r8		! ...
	ldc	r8, sr		! ...changed here.
	!
	mov.l	r7, @-r15
	mov.l	r6, @-r15
	mov.l	r5, @-r15
	mov.l	r4, @-r15
	mov.l	r3, @-r15
	mov.l	r2, @-r15
	mov.l	r1, @-r15
	mov.l	r0, @-r15
	! Then, dispatch to the handler, according to the exception code.
	stc	k_ex_code, r8
	shlr2	r8
	shlr	r8
	mov.l	4f, r9
	add	r8, r9
	mov.l	@r9, r9
	jmp	@r9
	 nop

	.align	2
1:	.long	0x00001000	! DSP=1
2:	.long	0x000080f0	! FD=1, IMASK=15
3:	.long	0xcfffffff	! RB=0, BL=0
4:	.long	exception_handling_table

	.align	2
ENTRY(exception_none)
	rts
	 nop