summaryrefslogtreecommitdiff
path: root/src/arch/i386/llshell/llshell.inc
blob: a66ac150b5fd4888065051e40192424ee141bfea (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

#define RET_LABEL(label)        \
	jmp label##_done

#define CALL_LABEL(label)       \
	jmp label               ;\
label##_done:

#define CALLSP(func) \
	lea     0f, %esp        ; \
	jmp func                ; \
0:

#define RETSP \
	jmp *%esp


#include "console.inc"
#include "pci.inc"
#include "ramtest.inc"

jmp llshell_out

// (c) 2004 Bryan Chafy,  This program is released under the GPL

// LLShell, A low level interactive debug shell
// Designed to be an interactive shell that operates with zero
// system resources.  For example at initial boot.

// to use, jump to label "low_level_shell"
// set %esp to the return address for exiting


#define UART_BASEADDR $0x3f8
#define resultreg %esi
#define subroutinereg %edi
#define freqtime $2193  // 1.93 * freq
#define timertime $6000
.equ	sys_IOPL, 110

// .data
// .text

welcome:
 	.string "\r\n! Low Level Shell (LLShell)  (c)2004 Bryan Chafy \r\n\r\n"
prompt:
	.string "\r\n!> "
badcmd:
 	.string "bad command\r\n"
sorry:
 	.string "sorry, not yet implemented\r\n"
cmds:
       	.string "\r\nList of commands:\r\n \
\r\nbeep                    -- pc speaker beep \
\r\nrst (or RST)            -- reset \
\r\nout(b,w,l) <val> <port> -- raw out val at port \
\r\nin(b,w,l)  <port>       -- show raw port value \
\r\njmp  <address>          -- jmp to address (llshell addr is in eax) \
\r\ncall <address>          -- funcion call (assumes a working stack) \
\r\ncli                     -- clear interrupts \
\r\nsti                     -- enable interrupts \
\r\npush <value>            -- push value onto stack \
\r\npop                     -- pop from stack and display \
\r\nwm(b,w,l) <addr> <val>  -- write mem \
\r\ndm   <addr> <lines>     -- dump mem  \
\r\nmcp  <src> <dst> <size> -- mem copy  \
\r\nmpat <pat> <dst> <size> -- mem pattern \
\r\nmemt <begin> <end>      -- memory test \
\r\npcir(b,w,l) <loc>       -- pci read config \
\r\npciw(b,w,l) <loc> <val> -- pci write config  \
\r\ndl   <addr> <size>      -- memory download (display xor cheksum at completion) \
\r\ncram <addr> <size>      -- enable cache to be ram (experimental) \
\r\nbaud <val>              -- change baudrate (not yet implemented)  \
\r\nexit                    -- exit shell \
\r\nAll values in hex (0x prefixing ok)  \
\r\n"

cr:
	.string "\r\n"
spaces:
	.string "   "

// .globl _start
//ASSUME CS:@CODE, DS:@DATA

// _start:

// call ioperms

low_level_shell:

mov $preamble,subroutinereg
jmp beep
preamble:
mov $welcome,resultreg
mov $readcommand,subroutinereg
jmp displaystring

readcommand:
mov $prompt,resultreg
mov $rcmd,subroutinereg
jmp displaystring

rcmd:
mov $readcommand,subroutinereg
movl $0x0, resultreg

readchar:
mov  UART_BASEADDR+5,%dx
in   %dx, %al
and  $0x9f,%al
test $0x01,%al
jz   readchar
mov  UART_BASEADDR,%dx
in   %dx,%al             //char in al
xchg %al,%ah

send_char:
mov  UART_BASEADDR+5,%dx
us_wait:
in   %dx,%al
test $0x20,%al
jz us_wait
mov  UART_BASEADDR,%dx
xchg %al,%ah
out  %al,%dx            // output char

cmp  $0x0D,%al      //CR
jnz  eval_char
mov  $0x0A,%ah
jmp  send_char

eval_char:
cmp  $0x20,%al      //space
jz   cmdtable
cmp  $0x0A,%al      //CR
jz   cmdtable
cmp  $0x08,%al      //BS
jnz  additup
//subit:
shr  $0x8,resultreg
jmp  readchar
additup:
shl  $0x8,resultreg
and  $0xff,%eax
add  %eax,resultreg
jmp  readchar

cmdtable:
mov resultreg,%eax
cmp $0,%eax
jz  readcommand
cmp $0x74657374,%eax
jz  dotest
cmp $0x68656c70,%eax
jz  dohelp
cmp $0x0000003f,%eax
jz  dohelp
cmp $0x6f757462,%eax
jz  dooutb
cmp $0x6f757477,%eax
jz  dooutw
cmp $0x6f75746c,%eax
jz  dooutd
cmp $0x00696e62,%eax
jz doinb
cmp $0x00696e77,%eax
jz doinw
cmp $0x00696e6c,%eax
jz doind
cmp $0x63697262,%eax
jz pcirb
cmp $0x63697277,%eax
jz pcirw
cmp $0x6369726c,%eax
jz pcirl
cmp $0x63697762,%eax
jz pciwb
cmp $0x63697777,%eax
jz pciww
cmp $0x6369776c,%eax
jz pciwl
cmp $0x00776d62,%eax
jz  wmemb
cmp $0x00776d77,%eax
jz  wmemw
cmp $0x00776d6c,%eax
jz  wmeml
cmp $0x0000646d,%eax
jz  dodmem
cmp $0x6d656d74,%eax
jz  memt                    // mem test
cmp $0x00727374,%eax
jz  rst                     // reset
cmp $0x00525354,%eax
jz  RST
cmp $0x62656570,%eax
jz  beep
cmp $0x0000646c,%eax
jz  dodl                    // download to mem <loc> <size>
cmp $0x006a6d70,%eax
jz  jmpto                   // jump to location (eax holds return addr)
cmp $0x62617564,%eax
jz  baud                    // change baudrate
cmp $0x00696e74,%eax
jz  doint                   // trigger an interrupt
cmp $0x63616c6c,%eax
jz  callto                  // call assumes memory
cmp $0x70757368,%eax
jz  dopush                  // assumes mem
cmp $0x00706f70,%eax
jz  dopop                   // assumes mem
cmp $0x6372616d,%eax
jz  cram                    // cache ram trick <location> <size>
cmp $0x006d6370,%eax
jz  mcp                     // mem copy <src> <dst> <size>
cmp $0x6d706174,%eax
jz  dopattern
cmp $0x00636c69,%eax
jz docli
cmp $0x00737469,%eax
jz dosti
cmp $0x65786974,%eax
jz  doexit
mov $badcmd,resultreg
mov $readcommand,subroutinereg
jmp displaystring


readnibbles:
movl $0x0, resultreg
readit:
mov  UART_BASEADDR+5,%dx
in   %dx, %al
and  $0x9f,%al
test $0x1,%al
jz   readit
mov  UART_BASEADDR,%dx
in   %dx,%al
xchg %al,%ah

sendchar:
mov  UART_BASEADDR+5,%dx
us_waitit:
in   %dx,%al
test $0x20,%al
jz   us_waitit
mov  UART_BASEADDR,%dx
xchg %al,%ah
out  %al,%dx            // output char

cmp  $0x78,%al
jz   readit
cmp  $0x0D,%al      //CR
jnz  evalchar
mov  $0x0A,%ah
jmp  sendchar

evalchar:
cmp  $0x20,%al        //space
jz   gosub
cmp  $0x0A,%al      //CR
jz   gosub
cmp  $0x08,%al      //BS
jnz  processchar
//subit:
shr  $0x04,resultreg
jmp  readit
processchar:
cmp  $0x3A,%al
jl   subnum
cmp  $0x47,%al
jl   subcaps
//sublc:
sub  $0x57,%al
jmp  additupn
subcaps:
sub  $0x37,%al
jmp  additupn
subnum:
sub  $0x30,%al
additupn:
shl  $0x04,resultreg
and  $0xf,%eax
add  %eax,resultreg
jmp  readit

gosub:
jmp  *subroutinereg

//intersubcall
// eax,edx,esi,edi

// ebx,ecx,ebp,esp(?)
// ds,es,fs,gs

dotest:
mov $ramtest,resultreg
mov $test1a,subroutinereg
jmp displayhex
test1a:
mov $welcome,resultreg
mov $readcommand,subroutinereg
jmp displayhex

dodmem:

movl $dmem1a, subroutinereg
jmp  readnibbles
dmem1a:
mov  resultreg,%ebx    // address
movl $dmem1b, subroutinereg
jmp  readnibbles
dmem1b:
mov  resultreg,%ecx    // length

dmemloop:
mov %ebx,resultreg
mov $daddr1,subroutinereg
jmp displayhex
daddr1:
mov $spaces,resultreg
mov $startshowm,subroutinereg
jmp displaystring

startshowm:
mov (%ebx),resultreg
mov $showm1,subroutinereg
jmp displayhexlinear
showm1:
add $0x04,%ebx
mov (%ebx),resultreg
mov $showm2,subroutinereg
jmp displayhexlinear
showm2:
add $0x04,%ebx
mov (%ebx),resultreg
mov $showm3,subroutinereg
jmp displayhexlinear
showm3:
add $0x04,%ebx
mov (%ebx),resultreg
mov $showa0,subroutinereg
jmp displayhexlinear

showa0:
sub $0xC,%ebx
mov (%ebx),resultreg
mov $showa1,subroutinereg
jmp displayasciilinear
showa1:
add $0x04,%ebx
mov (%ebx),resultreg
mov $showa2,subroutinereg
jmp displayasciilinear
showa2:
add $0x04,%ebx
mov (%ebx),resultreg
mov $showa3,subroutinereg
jmp displayasciilinear
showa3:
add $0x04,%ebx
mov (%ebx),resultreg
mov $doneshow,subroutinereg
jmp displayasciilinear
doneshow:
mov $cr,resultreg
mov $doneshow1,subroutinereg
jmp displaystring
doneshow1:
dec %cx
cmp $0x0,%cx
jz  exitdmem
add $0x04,%ebx
jmp dmemloop
exitdmem:
jmp readcommand

dooutb:
// out val,port
movl $outb1a, subroutinereg
jmp  readnibbles
outb1a:
mov  resultreg,%ebx
movl $outb1b, subroutinereg
jmp  readnibbles
outb1b:
mov  resultreg,%edx
mov  %ebx,%eax
out  %al,%dx
jmp  readcommand

dooutw:
// out val,port
movl $outw1a, subroutinereg
jmp  readnibbles
outw1a:
mov  resultreg,%ebx
movl $outw1b, subroutinereg
jmp  readnibbles
outw1b:
mov  resultreg,%edx
mov  %ebx,%eax
out  %ax,%dx
jmp  readcommand

dooutd:
// out val,port
movl $outd1a, subroutinereg
jmp  readnibbles
outd1a:
mov  resultreg,%ebx
movl $outd1b, subroutinereg
jmp  readnibbles
outd1b:
mov  resultreg,%edx
mov  %ebx,%eax
out  %eax,%dx
jmp  readcommand

wmemb:
movl $wmemba, subroutinereg
jmp  readnibbles
wmemba:
mov  resultreg,%ebx
movl $wmembb, subroutinereg
jmp  readnibbles
wmembb:
mov  resultreg,%eax
mov  %al,(%ebx)
jmp  readcommand

wmemw:
movl $wmemwa, subroutinereg
jmp  readnibbles
wmemwa:
mov  resultreg,%ebx
movl $wmemwb, subroutinereg
jmp  readnibbles
wmemwb:
mov  resultreg,%eax
mov  %ax,(%ebx)
jmp  readcommand

wmeml:
movl $wmemla, subroutinereg
jmp  readnibbles
wmemla:
mov  resultreg,%ebx
movl $wmemlb, subroutinereg
jmp  readnibbles
wmemlb:
mov  resultreg,%eax
mov  %eax,(%ebx)
jmp  readcommand

doinb:
// in port
movl $inb1a, subroutinereg
jmp  readnibbles
inb1a:
mov  resultreg,%edx
mov  $0x0,%eax
in   %dx,%al
mov  %eax,resultreg
mov  $readcommand,subroutinereg
jmp  displayhex

doinw:
// in port
movl $inw1a, subroutinereg
jmp  readnibbles
inw1a:
mov  resultreg,%edx
mov  $0x0,%eax
in   %dx,%ax
mov  %eax,resultreg
mov  $readcommand,subroutinereg
jmp  displayhex

doind:
// in port
movl $ind1a, subroutinereg
jmp  readnibbles
ind1a:
mov  resultreg,%edx
in   %dx,%eax
mov  %eax,resultreg
mov  $readcommand,subroutinereg
jmp  displayhex

jmpto:
movl $jmp1a, subroutinereg
jmp  readnibbles
jmp1a:
mov  $readcommand,%eax
jmp  *resultreg

callto:
movl $call1a, subroutinereg
jmp  readnibbles
call1a:
mov  $readcommand,%eax
call *resultreg
jmp  readcommand

dopush:
movl $push1a, subroutinereg
jmp  readnibbles
push1a:
mov  resultreg,%eax
push %eax
jmp  readcommand

doint:
movl $int1a, subroutinereg
jmp  readnibbles
int1a:
mov  resultreg,%eax
// need to lookup int table?
// int  %eax
jmp  readcommand

doenter:
//setup stack frame


dopop:
movl $readcommand, subroutinereg
pop  resultreg
jmp  displayhex

docli:
cli
jmp  readcommand

dosti:
sti
jmp  readcommand


displaystring:
// resultreg= pointer to string terminated by \0
dsloop:
movb  (resultreg),%ah
cmp  $0x0, %ah
jz   displaystringexit
mov  UART_BASEADDR+5,%dx
us_waits:
in   %dx,%al
test $0x20,%al
jz us_waits
mov  UART_BASEADDR,%dx
xchg %al,%ah
out  %al,%dx            // output char
inc  resultreg
jmp  dsloop
displaystringexit:
jmp  *subroutinereg

displayhexlinear:
mov  resultreg,%eax
xchg %al,%ah
rol  $0x10,%eax
xchg %al,%ah
mov  %eax,resultreg
displayhex:
rol  $0x10,%ecx
mov  $0x8,%cx
dhloop:
cmp  $0xf,%cl
je   exitdisplayhex
rol  $0x04,resultreg
movl resultreg,%eax
and  $0xf,%al
cmp  $0xa,%al
jl   addnum
//addcaps
add $0x37,%al
jmp  outcharhex
addnum:
add  $0x30,%al
outcharhex:
xchg %al,%ah
mov  UART_BASEADDR+5,%dx
us_waith:
in   %dx,%al
test $0x20,%al
jz us_waith
mov  UART_BASEADDR,%dx
xchg %al,%ah
out  %al,%dx            // output char
dec  %cx
cmp  $0x0,%cx
jne  dhloop
mov  $0x20,%al
mov  $0x10,%cl
jmp  outcharhex
exitdisplayhex:
rol  $0x10,%ecx
jmp  *subroutinereg

displayasciilinear:
mov  resultreg,%eax
xchg %al,%ah
rol  $0x10,%eax
xchg %al,%ah
mov  %eax,resultreg
displayascii:
rol  $0x10,%ecx
mov  $0x4,%cx
daloop:
rol  $0x08,resultreg
movl resultreg,%eax
cmp  $0x7e,%al
jg   unprintable
cmp  $0x20,%al
jl   unprintable
jmp  outcharascii
unprintable:
mov  $0x2e,%al          // dot
outcharascii:
xchg %al,%ah
mov  UART_BASEADDR+5,%dx
us_waita:
in   %dx,%al
test $0x20,%al
jz us_waita
mov  UART_BASEADDR,%dx
xchg %al,%ah
out  %al,%dx            // output char
dec  %cx
cmp  $0x0,%cx
jne  daloop
rol  $0x10,%ecx
jmp  *subroutinereg

rst:
cli
movb $0x0fe,%al
out  %al,$0x64
hlt

RST:
cli
lidt %cs:0x03fff
int  $0x3
hlt


beep:
mov  timertime,%eax
rol  $0x10,%eax
mov  $0xb6,%al
out  %al,$0x43
mov  freqtime,%ax
out  %al,$0x42
xchg %al,%ah
out  %al,$0x42

in   $0x61,%al
or   $0x03,%al
out  %al,$0x61

//timer here
timer:
in   $0x42,%al
// xchg %al,%ah
in   $0x42,%al
// xchg %al,%ah
cmp  $0x0,%al
jnz  timer
rol  $0x10,%eax
dec  %ax
cmp  $0x0,%ax;
rol  $0x10,%eax
jnz  timer
// timer

in   $0x61,%al
and  $0xfc,%al
out  %al,$0x61
jmp  *subroutinereg

dohelp:
mov $cmds,resultreg
mov $readcommand,subroutinereg
jmp displaystring

memt:
movl $memt1, subroutinereg
jmp  readnibbles
memt1:
mov  resultreg,%ecx
movl $memt2, subroutinereg
jmp  readnibbles
memt2:
mov  resultreg,%ebx
xchg %ecx,%eax
mov  $readcommand,%esp   // internal to linux bios
jmp ramtest

pcirb:
movl $pcirb1, subroutinereg
jmp  readnibbles
pcirb1:
mov  resultreg,%eax
PCI_READ_CONFIG_BYTE
and  $0xff,%eax
mov  %eax,resultreg
mov  $readcommand,subroutinereg
jmp  displayhex

pcirw:
movl $pcirw1, subroutinereg
jmp  readnibbles
pcirw1:
mov  resultreg,%eax
PCI_READ_CONFIG_WORD
and  $0xffff,%eax
mov  %eax,resultreg
mov  $readcommand,subroutinereg
jmp  displayhex

pcirl:
movl $pcirl1, subroutinereg
jmp  readnibbles
pcirl1:
mov  resultreg,%eax
PCI_READ_CONFIG_DWORD
mov  %eax,resultreg
mov  $readcommand,subroutinereg
jmp  displayhex




pciwb:
movl $pciwb1, subroutinereg
jmp  readnibbles
pciwb1:
mov  resultreg,%ebx
movl $pciwb2, subroutinereg
jmp  readnibbles
pciwb2:
mov  resultreg,%edx
mov  %ebx,%eax
PCI_WRITE_CONFIG_BYTE
jmp  readcommand

pciww:
movl $pciww1, subroutinereg
jmp  readnibbles
pciww1:
mov  resultreg,%ebx
movl $pciww2, subroutinereg
jmp  readnibbles
pciww2:
mov  resultreg,%ecx
mov  %ebx,%eax
PCI_WRITE_CONFIG_WORD
jmp  readcommand

pciwl:
movl $pciwl1, subroutinereg
jmp  readnibbles
pciwl1:
mov  resultreg,%ebx
movl $pciwl2, subroutinereg
jmp  readnibbles
pciwl2:
mov  resultreg,%ecx
mov  %ebx,%eax
PCI_WRITE_CONFIG_DWORD
jmp  readcommand

cram:
//likely not working.  Just testing for now
movl $cram1, subroutinereg
jmp  readnibbles
cram1:
mov resultreg,%ebx
movl $cram1, subroutinereg
jmp  readnibbles
cram2:
mov resultreg,%ecx
// enable it
mov %cr0,%eax
and $0x9fffffff,%eax  // also try 0x0fff, 0x2ff(write back)...
mov %eax,%cr0
//wbinvd ??
cacheloop:
mov (%ebx),%eax
inc %ebx
loop cacheloop
// disable it
mov %cr0,%eax
or  $0x60000000,%eax
mov %eax,%cr0
//wbinvd ??

dodl:
movl $dl1, subroutinereg
jmp  readnibbles
dl1:
mov  resultreg,%ebx
movl $dl2, subroutinereg
jmp  readnibbles
dl2:
mov  resultreg,%ecx
mov  resultreg,subroutinereg
mov  %ebx,resultreg
dlloop:
mov  UART_BASEADDR+5,%dx
in   %dx, %al
and  $0x9f,%al
test $0x01,%al
jz   dlloop
mov  UART_BASEADDR,%dx
in   %dx,%al
mov  %al,(%ebx)
inc  %ebx
loop dlloop
csum:
mov subroutinereg,%ecx
shr $0x02,%ecx
mov resultreg,%ebx
mov $0x0,%eax
csumloop:
rol $0x03,%eax
mov (%ebx),%dl
xor  %dl,%al
inc  %ebx
loop csumloop
mov $readcommand,subroutinereg
mov %eax,resultreg
jmp displayhex

baud:
mov $sorry,resultreg
mov $readcommand,subroutinereg
jmp displaystring

mcp:
movl $mcp1, subroutinereg
jmp  readnibbles
mcp1:
mov  resultreg,%ebx
movl $mcp2, subroutinereg
jmp  readnibbles
mcp2:
mov  resultreg,%ecx
movl $mcp3, subroutinereg
jmp  readnibbles
mcp3:
mov  resultreg,%eax
xchg %ecx,%eax
mcploop:
mov  (%ebx),%dl
mov  %dl,(%eax)
inc  %ebx
inc  %eax
loop mcploop
jmp  readcommand

dopattern:
movl $pat1, subroutinereg
jmp  readnibbles
pat1:
mov  resultreg,%ebx
movl $pat2, subroutinereg
jmp  readnibbles
pat2:
mov  resultreg,%ecx
movl $pat3, subroutinereg
jmp  readnibbles
pat3:
mov  resultreg,%eax
xchg %ecx,%eax
patloop:
rol $0x08,%ebx
mov %bl,(%eax)
inc %eax
loop patloop
jmp readcommand


doexit:
         // LB specific:
RETSP    // if there's no stack yet, caller must set %esp manually
// RET_LABEL(low_level_shell)


//Linux OS Specific
ioperms:
movl	$sys_IOPL, %eax		# system-call ID-number
movl	$3, %ebx		# new value for IO0PL
int	$0x80			# enter the kernel
ret

llshell_out: