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
|
/* start.S -- bootup code for the Bender board using the Or1k
* architecture.
*
* Copyright (C) 2001 Chris Ziomkowski, chris@asics.ws
*
* This file is distributed as part of the RTEMS package from
* OAR Corporation, and follows the licensing and distribution
* terms as stated for RTEMS.
*
* COPYRIGHT (c) 1989-1999.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.com/license/LICENSE.
*/
#include <rtems/asm.h>
/* Since we don't yet have a memory map for Bender, I am
assuming the following. Hopefully, this will be easily
modified once we get the real values.
0x00000000 - 0x00200000: Flash/ROM (boot code / 2 MB)
0x01000000 - 0x010FFFFF: Synchronous SRAM (area 2 / 1 MB)
0x10000000 - 0x1FFFFFFF: External SDRAM (area 3 / 256 MB)
0x20000000 - 0x2FFFFFFF: External SDRAM (area 4 / 256 MB)
0x80000000 - 0x8000001F: 4 16550 UART controllers
0x80010000 - 0x80017FFF: Internal Bender RAM
0x80020000 - 0xFFFFFFFF: Memory mapped Bender Peripherals
For this version, I assume that only the flash and 32 MB
of RAM in area 3 are populated. Everything else should
return a bus error when accessed.
*/
.file "start.S"
.data
PUBLIC(Or1k_Interrupt_Vectors)
SYM (Or1k_Interrupt_Vectors):
.word 0x00000000 # No Vector
.word _start # Reset Vector (Ignored)
.word __Internal_error_Occurred # Bus Error
.word __Internal_error_Occurred # Data Page Fault
.word __Internal_error_Occurred # Instruction Page Fault
.word __int_reenable # Low Priority Interrupt
.word __Internal_error_Occurred # Alignment Exception
.word __Internal_error_Occurred # Illegal Instruction Exception
.word __int_reenable # High Priority Interrupt
.word __Internal_error_Occurred # ITBL Miss
.word __Internal_error_Occurred # DTBL Miss
.word 0x00000000 # Range Exception
.word 0x00000000 # System Call
.word 0x00000000 # Breakpoint
.word 0x00000000 # Trap
/*
PUBLIC(BOTTOM_OF_MEMORY)
SYM (BOTTOM_OF_MEMORY):
.word 0x10000000 # Assume RAM @ 0 for the sim
PUBLIC(TOP_OF_MEMORY)
SYM (TOP_OF_MEMORY):
.word 0x10800000 # Assume RAM @ 0 for the sim
*/
PUBLIC(_mem_end)
SYM (_mem_end):
.word 0x10800000
BEGIN_CODE
.org 0x0
/**************/
/* _panic */
/**************/
/* Place the panic vector at 0 */
.proc __panic
.def __panic
.val __panic
.scl 2
.type 044
.endef
.global __panic
__panic:
l.jal __exit
l.nop
.endproc __panic
.def __panic
.val .
.scl -1
.endef
/* Exception processing...first, we will save the
16 non callee saved registers which could be
corrupted by calling a C function. We have no
way of knowing which of these will be used, so
we have to save all of them. We will then save
the EPCR and ESR, in case a nested exception is
called. Next, we call the user function. We then
restore all the registers to their original
values, and finally disable exceptions, restore
EPCR and ESR (EEAR is not essential to restore)
and then return from the interrupt. */
/******************************************/
/* Normal exception handling */
/* Called with 80 bytes allocated on the */
/* stack, the vector function in r11, and */
/* the vector number in r3. Original */
/* values at 28(r1) and 0(r1). */
/******************************************/
.proc ___standard_exception
.def ___standard_exception
.val ___standard_exception
.scl 2
.type 044
.endef
.global ___standard_exception
___standard_exception:
l.sfeqi r11,0 /* Ignore it if it is zero */
l.bf L2_2
l.sw 4(r1),r4 /* Save r4 */
/* Ignore fast context switching in this release. */
/* It's poorly conceived, and will probably never */
/* be implemented... */
l.sw 8(r1),r5
l.sw 12(r1),r6
l.sw 16(r1),r7
l.mfspr r4,r0,0x20 /* Save EPCR */
l.mfspr r5,r0,0x30 /* Save EEAR */
l.mfspr r6,r0,0x40 /* Save ESR */
l.mfspr r7,r0,17
l.ori r7,r7,2
l.mtspr r0,r7,17 /* Reenable exceptions */
l.sw 20(r1),r8
l.sw 24(r1),r9
l.sw 32(r1),r12
l.sw 36(r1),r14
l.sw 40(r1),r16
l.sw 44(r1),r18
l.sw 48(r1),r20
l.sw 52(r1),r22
l.sw 56(r1),r24
l.sw 60(r1),r26
l.sw 64(r1),r28
l.sw 68(r1),r30
l.sw 72(r1),r4 /* Save EPCR. User could change r4 */
/* Now, call the installed handler with the arguments:
r3 ==> vector # (1-14)
r4 ==> EPCR
r5 ==> EEAR
r6 ==> ESR
r11 ==> User function
*/
l.jal ___user_function /* Call the user routine */
l.sw 76(r1),r6 /* Save ESR. User could change r6 */
/* Ignore r5 (EEAR). It is not critical for state */
l.lwz r30,68(r1)
l.lwz r28,64(r1)
l.lwz r26,60(r1)
l.lwz r24,56(r1)
l.lwz r22,52(r1)
l.lwz r20,48(r1)
l.lwz r18,44(r1)
l.lwz r16,40(r1)
l.lwz r14,36(r1)
l.lwz r12,32(r1)
l.lwz r9,24(r1)
l.lwz r8,20(r1)
l.lwz r7,16(r1)
l.lwz r5,8(r1)
l.addi r6,r0,-3 /* Set r6 to 0xFFFFFFFD */
l.mfspr r3,r0,17 /* Get SR value */
l.and r3,r3,r6 /* Clear exception bit */
l.mfspr r0,r3,17 /* Disable exceptions */
l.lwz r6,76(r1) /* Recover ESR */
l.lwz r4,72(r1) /* Recover EPCR */
l.mtspr r0,r4,0x20 /* Restore ESR */
l.mtspr r0,r6,0x40 /* Restore EPCR */
l.lwz r6,12(r1)
l.lwz r4,4(r1)
L2_2:
l.lwz r11,28(r1)
l.lwz r3,0(r1)
l.addi r1,r1,80
l.rfe
l.nop /* The document doesn't say this is
a delay slot instruction, but the
simulator doesn't work without this. */
.endproc ___standard_exception
.def ___standard_exception
.val .
.scl -1
.endef
/****************************************************************************/
/* These constants must be in .text section in order to be */
/* properly addressed in code. */
PUBLIC(BOTTOM_OF_MEMORY)
SYM (BOTTOM_OF_MEMORY):
.word 0x10000000 # Assume RAM @ 0 for the sim
PUBLIC(TOP_OF_MEMORY)
SYM (TOP_OF_MEMORY):
.word 0x10800000 # Assume RAM @ 0 for the sim
/****************************************************************************/
/** Currently, about 57 of the 64 valid address locations
are being used here. If you add code to the above
routine, make sure it isn't more than 7 instructions
or you will overflow into the reset vector. **/
/****************************/
/* Reset vector static code */
/****************************/
.org 0x100
.proc ___rst
.global ___rst
___rst:
/* Set the stack pointer */
l.movhi r1,hi(_TOP_OF_MEMORY)
l.ori r1,r1,lo(_TOP_OF_MEMORY)
l.lwz r1,0(r1) /* Dereference it */
/* Set the frame pointer */
l.add r2,r0,r1
l.mfspr r3,r0,17 /* Get SR value */
l.ori r3,r3,2 /* Set exception enable bit */
l.j _start /* Jump to main routine */
l.mtspr r0,r3,17 /* Enable exceptions (DELAY) */
.endproc ___rst
/***********************************************************/
/* Note: right after the reset vector, we are going to */
/* place a table with the necessary values to initialize */
/* the memory controller. This pointer will be set and */
/* passed to the _start routine in r4. The first thing the */
/* the _start routine will do is to initialize the memory */
/* controller. The code to initialze the memory controller */
/* is expected to be larger than the 50 some odd */
/* instructions that are remaining here before the bus */
/* error vector, which is why it is left to the _start */
/* routine. */
/***********************************************************/
/********************************/
/* Bus Error vector static code */
/********************************/
.org 0x200
.proc ___bus_error
.global ___bus_error
___bus_error:
l.addi r1,r1,-80
l.sw 0(r1),r3
l.sw 28(r1),r11
l.movhi r11,hi(_Or1k_Interrupt_Vectors)
l.ori r11,r11,lo(_Or1k_Interrupt_Vectors)
l.lwz r11,8(r11)
l.j ___standard_exception
l.addi r3,r0,2
.endproc ___bus_error
/* Put _Internal_error_Occurred and _int_reenable here */
/* No reason to waste space...it'll be filled with 0 if */
/* we don't... */
/********************************/
/* _Internal_error_Occurred */
/********************************/
.proc __Internal_error_Occurred
.def __Internal_error_Occurred
.val __Internal_error_Occurred
.scl 2
.type 044
.endef
.global __Internal_error_Occurred
__Internal_error_Occurred:
l.jal __panic
l.nop
.endproc __Internal_error_Occurred
.def __Internal_error_Occurred
.val .
.scl -1
.endef
/*********************/
/* _int_reenable */
/*********************/
.proc __int_reenable
.def __int_reenable
.val __int_reenable
.scl 2
.type 044
.endef
.global __int_reenable
__int_reenable:
l.mfspr r11,r0,17
l.ori r11,r11,0x04
l.jr r9
l.mtspr r0,r11,17
.endproc __int_reenable
.def __int_reenable
.val .
.scl -1
.endef
/*********************&**/
/* ___user_function */
/************************/
.proc ___user_function
.def ___user_function
.val ___user_function
.scl 2
.type 044
.endef
.global ___user_function
___user_function:
/* r11 contains the address to call. We can
modify r7, r8, r12, and r14 at will */
l.movhi r7,hi(__Thread_Dispatch_disable_level)
l.ori r7,r7,lo(__Thread_Dispatch_disable_level)
l.lwz r8,0(r7)
l.addi r1,r1,-8 # Stack must be DWORD aligned
l.sw 0(r1),r9 # Save the return address
l.addi r8,r8,1 # Increment __Thread_Dispatch...
l.jalr r11
l.sw 0(r7),r8 # Disable thread dispatching
/* Now, we need to determine if we need to
service the RTEMS environment. RTEMS tries
to draw a distinction between a RAW handler
(where this isn't necessary) and an RTEMS
handler. However, it appears almost all ISR's
will not be RAW under this definition, and
those that are will not honestly be hurt by
the 20 or so extra cycles it will take to do
the following code. If there is a very frequent
interrupt, then it should probably be hard
coded into the static routine anyway, rather
than suffer the hit of calling it indirectly */
/* Note: RTEMS recommends incrementing and
decrementing the _ISR_Nest_Level as well.
We are specifically not doing this because
in the Or1k architecture it is impossible
to nest interrupts. Interrupts must run to
completion before reenabling. If there is a
significant task to be done, then it should
run in a bottom half handler, similar to the
way Linux works. In theory though, even if
we do allow nested interrupts, there is no
reason for this flag, as it seems to be for
the purpose of restoring the normal stack in
place of the interrupt stack. We don't use a
separate exception stack, so this should not
be an issue for us. */
l.movhi r7,hi(__Thread_Dispatch_disable_level)
l.ori r7,r7,lo(__Thread_Dispatch_disable_level)
l.lwz r8,0(r7)
l.addi r8,r8,-1 # Decrement __Thread_Dispatch...
l.sw 0(r7),r8 # Memory stall likely here...
l.sfeqi r8,0 # Skip if _Thread_Dispatch != 0
l.bnf L4_2
l.movhi r7,hi(__Context_Switch_necessary)
l.ori r7,r7,lo(__Context_Switch_necessary)
l.lwz r8,0(r7)
l.movhi r7,hi(__ISR_Signals_to_thread_executing)
l.ori r7,r7,lo(__ISR_Signals_to_thread_executing)
l.lwz r12,0(r7)
l.sfeqi r8,0 # Skip if __Context... is false
l.bf L4_2
l.movhi r14,hi(__Thread_Dispatch)
l.sfeqi r12,0 # Skip if __ISR... is true
l.bnf L4_2
l.ori r14,r14,lo(__Thread_Dispatch)
l.jalr r14
l.sw 0(r7),r0 # Set __ISR... to false
L4_2:
l.lwz r9,0(r1) # Recover the return address
l.jr r9
l.addi r1,r1,8 # Reset the stack
.endproc ___user_function
.def ___user_function
.val .
.scl -1
.endef
/* Code wasted between here and 0x300 */
/**************************************/
/* Data Page Fault vector static code */
/**************************************/
.org 0x300
.proc ___data_page_fault
.global ___data_page_fault
___data_page_fault:
l.addi r1,r1,-80
l.sw 0(r1),r3
l.sw 28(r1),r11
l.movhi r11,hi(_Or1k_Interrupt_Vectors)
l.ori r11,r11,lo(_Or1k_Interrupt_Vectors)
l.lwz r11,12(r11)
l.j ___standard_exception
l.addi r3,r0,3
.endproc ___data_page_fault
/* Code wasted between here and 0x400 */
/*********************************************/
/* Instruction Page Fault vector static code */
/*********************************************/
.org 0x400
.proc ___insn_page_fault
.global ___insn_page_fault
___insn_page_fault:
l.addi r1,r1,-80
l.sw 0(r1),r3
l.sw 28(r1),r11
l.movhi r11,hi(_Or1k_Interrupt_Vectors)
l.ori r11,r11,lo(_Or1k_Interrupt_Vectors)
l.lwz r11,16(r11)
l.j ___standard_exception
l.addi r3,r0,4
.endproc ___insn_page_fault
/* Code wasted between here and 0x500 */
/**************************************/
/* Low Priority Interrupt static code */
/**************************************/
.org 0x500
.proc ___low_priority_int
.global ___low_priority_int
___low_priority_int:
l.addi r1,r1,-80
l.sw 0(r1),r3
l.sw 28(r1),r11
l.mfspr r3,r0,17 # Get the SR
l.addi r11,r0,-5 # r11 = 0xFFFFFFFB
l.and r11,r11,r3 # Clear the EIR bit
l.mtspr r0,r11,17 # Set the SR w/o INT
l.movhi r11,hi(_Or1k_Interrupt_Vectors)
l.ori r11,r11,lo(_Or1k_Interrupt_Vectors)
l.lwz r11,20(r11)
l.j ___standard_exception
l.addi r3,r0,5
.endproc ___low_priority_int
/* Code wasted between here and 0x600 */
/******************************************/
/* Alignment Exception vector static code */
/******************************************/
.org 0x600
.proc ___alignment_exception
.global ___alignment_exception
___alignment_exception:
l.addi r1,r1,-80
l.sw 0(r1),r3
l.sw 28(r1),r11
l.movhi r11,hi(_Or1k_Interrupt_Vectors)
l.ori r11,r11,lo(_Or1k_Interrupt_Vectors)
l.lwz r11,24(r11)
l.j ___standard_exception
l.addi r3,r0,6
.endproc ___alignment_exception
/* Code wasted between here and 0x700 */
/******************************************/
/* Illegal Instruction vector static code */
/******************************************/
.org 0x700
.proc ___illegal_instruction
.global ___illegal_instruction
___illegal_instruction:
l.addi r1,r1,-80
l.sw 0(r1),r3
l.sw 28(r1),r11
l.movhi r11,hi(_Or1k_Interrupt_Vectors)
l.ori r11,r11,lo(_Or1k_Interrupt_Vectors)
l.lwz r11,28(r11)
l.j ___standard_exception
l.addi r3,r0,7
.endproc ___illegal_instruction
/* Code wasted between here and 0x800 */
/***************************************/
/* High Priority Interrupt static code */
/***************************************/
.org 0x800
.proc ___high_priority_int
.global ___high_priority_int
___high_priority_int:
l.addi r1,r1,-80
l.sw 0(r1),r3
l.sw 28(r1),r11
l.mfspr r3,r0,17 # Get the SR
l.addi r11,r0,-5 # r11 = 0xFFFFFFFB
l.and r11,r11,r3 # Clear the EIR bit
l.mtspr r0,r11,17 # Set the SR w/o INT
l.movhi r11,hi(_Or1k_Interrupt_Vectors)
l.ori r11,r11,lo(_Or1k_Interrupt_Vectors)
l.lwz r11,32(r11)
l.j ___standard_exception
l.addi r3,r0,8
.endproc ___high_priority_int
/* Code wasted between here and 0x900 */
/********************************/
/* ITBL Miss vector static code */
/********************************/
.org 0x900
.proc ___ITBL_miss_exception
.global ___ITBL_miss_exception
___ITBL_miss_exception:
l.addi r1,r1,-80
l.sw 0(r1),r3
l.sw 28(r1),r11
l.movhi r11,hi(_Or1k_Interrupt_Vectors)
l.ori r11,r11,lo(_Or1k_Interrupt_Vectors)
l.lwz r11,36(r11)
l.j ___standard_exception
l.addi r3,r0,9
.endproc ___ITBL_miss_exception
/* Code wasted between here and 0xA00 */
/********************************/
/* DTBL Miss vector static code */
/********************************/
.org 0xA00
.proc ___DTBL_miss_exception
.global ___DTBL_miss_exception
___DTBL_miss_exception:
l.addi r1,r1,-80
l.sw 0(r1),r3
l.sw 28(r1),r11
l.movhi r11,hi(_Or1k_Interrupt_Vectors)
l.ori r11,r11,lo(_Or1k_Interrupt_Vectors)
l.lwz r11,40(r11)
l.j ___standard_exception
l.addi r3,r0,10
.endproc ___DTBL_miss_exception
/* Code wasted between here and 0xB00 */
/**************************************/
/* Range Exception vector static code */
/**************************************/
.org 0xB00
.proc ___range_exception
.global ___range_exception
___range_exception:
l.addi r1,r1,-80
l.sw 0(r1),r3
l.sw 28(r1),r11
l.movhi r11,hi(_Or1k_Interrupt_Vectors)
l.ori r11,r11,lo(_Or1k_Interrupt_Vectors)
l.lwz r11,44(r11)
l.j ___standard_exception
l.addi r3,r0,11
.endproc ___range_exception
/* Code wasted between here and 0xC00 */
/**********************************/
/* System Call vector static code */
/**********************************/
.org 0xC00
.proc ___system_call
.global ___system_call
___system_call:
l.addi r1,r1,-80
l.sw 0(r1),r3
l.sw 28(r1),r11
l.movhi r11,hi(_Or1k_Interrupt_Vectors)
l.ori r11,r11,lo(_Or1k_Interrupt_Vectors)
l.lwz r11,48(r11)
l.j ___standard_exception
l.addi r3,r0,12
.endproc ___system_call
/* Code wasted between here and 0xD00 */
/**********************************/
/* Breakpoint vector static code */
/**********************************/
.org 0xD00
.proc ___breakpoint
.global ___breakpoint
___breakpoint:
/* In keeping with the necessary requirements for
gdb to work, we are limiting this vector to
only 2 statements, which effect an immediate
return. At a later date, we may insert a debug
monitor here that will do even more, but for
now, this is all we want. */
l.rfe
l.nop
.endproc ___breakpoint
/* Code wasted between here and 0xE00 */
/*************************************/
/* Trap Exception vector static code */
/*************************************/
.org 0xE00
.proc ___trap_exception
.global ___trap_exception
___trap_exception:
l.addi r1,r1,-80
l.sw 0(r1),r3
l.sw 28(r1),r11
l.movhi r11,hi(_Or1k_Interrupt_Vectors)
l.ori r11,r11,lo(_Or1k_Interrupt_Vectors)
l.lwz r11,56(r11)
l.j ___standard_exception
l.addi r3,r0,14
.endproc ___trap_exception
/* Code wasted between here and 0x2000 */
/* Exceptions from 0xF00 to 0x1F00 are not defined */
/* in the Or1k architecture. They should be filled */
/* in here for other implementations. */
.org 0x2000 /* Start after exception vector table */
/*********************/
/* start */
/*********************/
/* This is where we jump to right after the reset exception
handler. The system configuration information should
be passed to us in a pointer in r4. Generally, the
reset vector will call this routine directly, and
the memory configuration information will be stored
in the ROM/Flash image. It was decided no attempt
would be made to automatically determine this
information by probing, as the scheme would be too
complex and inherently unreliable. */
/* Initialize strings and structures here */
L_program:
.ascii "RTEMS_or1k\000"
.align 4
L_argv:
.word L_program
.proc _start
.def _start
.val _start
.scl 2
.type 044
.endef
.global _start
_start:
/* Initialize the memory controller here!
Discussions with Rudi have stated that
the first few bytes of the ROM image should
contain a RAM map as opposed to trying to
figure out what to do based on probing. This
means a separate build of the OS for every
possible board configuration, but there
doesn't seem to be a better alternative. */
/*** FIX ME! Initialize the external memory controller! ***/
/* Move the data segment to RAM. Alternatively, we may
copy the text segment as well. For now, we'll assume
that the cache gives us sufficient performance that this
is not necessary. It will be very easy to add this later.
*/
l.movhi r4,hi(_etext)
l.ori r4,r4,lo(_etext)
l.movhi r5,hi(_BOTTOM_OF_MEMORY)
l.ori r5,r5,lo(_BOTTOM_OF_MEMORY)
l.lwz r5,0(r5) # Dereference it
/* l.add r5,r5,r4 # Place it in memory above the text segment*/
l.movhi r3,hi(_edata)
l.ori r3,r3,lo(_edata)
l.movhi r5,hi(_data_start)
l.ori r5,r5,lo(_data_start)
L3_0:
l.lwz r6,0(r4)
l.addi r5,r5,4
l.addi r4,r4,4
l.sfeq r3,r5
l.bnf L3_0
l.sw -4(r5),r6 # Minimize write after read stalls
/* Initialize the BSS segment */
l.movhi r3,hi(__end)
l.ori r3,r3,lo(__end)
/* l.sub r3,r3,r4
l.add r3,r3,r5*/
l.sfleu r3,r5
l.bf L3_2 # Check for no BSS segment!
l.nop
L3_1:
l.addi r5,r5,4
l.sfeq r5,r3
l.bnf L3_1
l.sw -4(r5),r0
L3_2:
/* Tell everyone where the heap begins */
l.movhi r4,hi(__mem_end)
l.ori r4,r4,lo(__mem_end)
l.sw 0(r4),r5
/* Due to what I consider a bug in RTEMS, the entire
heap must be zeroed. I think this is the dumbest thing
I've ever heard, but whatever turns them on. I'd rather
see the code which depends on this behavior fixed. I
myself have never written code which assumes zeroes
will be returned from memory allocated from the heap.
Anyway, if I don't do it here, I have to set a flag in
the CPU structure which then will do it anyway, but
from less efficient C code! Zero from here to the
stack pointer... One day when I'm old and gray maybe
I'll set this to random values instead and fix
whatever breaks. */
l.sw 0(r5),r0
l.sfeq r5,r1
l.bnf L3_3
l.addi r5,r5,4
L3_3:
l.addi r3,r0,1 /* Set argc to 1 */
l.movhi r4,hi(L_argv) /* Initialize argv */
l.ori r4,r4,lo(L_argv)
l.addi r5,r5,0 /* Set envp to NULL */
l.mfspr r11,r0,17 /* Get SR value */
l.ori r11,r11,0x4 /* Set interrupt enable bit */
l.jal _boot_card /* Boot up the card...run the OS */
l.mtspr r0,r11,17 /* Enable exceptions (DELAY) */
/* We're done. We exited normally. Shut down. */
l.jal __exit
l.nop
.endproc _start
.def _start
.val .
.scl -1
.endef
END_CODE
|