aboutsummaryrefslogtreecommitdiff
path: root/arch/mips/kernel/gdb-stub.c
blob: c33f6f22d86a5651e503e001360ae379905e3cee (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
/*
 *  arch/mips/kernel/gdb-stub.c
 *
 *  Originally written by Glenn Engel, Lake Stevens Instrument Division
 *
 *  Contributed by HP Systems
 *
 *  Modified for SPARC by Stu Grossman, Cygnus Support.
 *
 *  Modified for Linux/MIPS (and MIPS in general) by Andreas Busse
 *  Send complaints, suggestions etc. to <andy@waldorf-gmbh.de>
 *
 *  Copyright (C) 1995 Andreas Busse
 *
 *  Copyright (C) 2003 MontaVista Software Inc.
 *  Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
 */

/*
 *  To enable debugger support, two things need to happen.  One, a
 *  call to set_debug_traps() is necessary in order to allow any breakpoints
 *  or error conditions to be properly intercepted and reported to gdb.
 *  Two, a breakpoint needs to be generated to begin communication.  This
 *  is most easily accomplished by a call to breakpoint().  Breakpoint()
 *  simulates a breakpoint by executing a BREAK instruction.
 *
 *
 *    The following gdb commands are supported:
 *
 * command          function                               Return value
 *
 *    g             return the value of the CPU registers  hex data or ENN
 *    G             set the value of the CPU registers     OK or ENN
 *
 *    mAA..AA,LLLL  Read LLLL bytes at address AA..AA      hex data or ENN
 *    MAA..AA,LLLL: Write LLLL bytes at address AA.AA      OK or ENN
 *
 *    c             Resume at current address              SNN   ( signal NN)
 *    cAA..AA       Continue at address AA..AA             SNN
 *
 *    s             Step one instruction                   SNN
 *    sAA..AA       Step one instruction from AA..AA       SNN
 *
 *    k             kill
 *
 *    ?             What was the last sigval ?             SNN   (signal NN)
 *
 *    bBB..BB	    Set baud rate to BB..BB		   OK or BNN, then sets
 *							   baud rate
 *
 * All commands and responses are sent with a packet which includes a
 * checksum.  A packet consists of
 *
 * $<packet info>#<checksum>.
 *
 * where
 * <packet info> :: <characters representing the command or response>
 * <checksum>    :: < two hex digits computed as modulo 256 sum of <packetinfo>>
 *
 * When a packet is received, it is first acknowledged with either '+' or '-'.
 * '+' indicates a successful transfer.  '-' indicates a failed transfer.
 *
 * Example:
 *
 * Host:                  Reply:
 * $m0,10#2a               +$00010203040506070809101112131415#42
 *
 *
 *  ==============
 *  MORE EXAMPLES:
 *  ==============
 *
 *  For reference -- the following are the steps that one
 *  company took (RidgeRun Inc) to get remote gdb debugging
 *  going. In this scenario the host machine was a PC and the
 *  target platform was a Galileo EVB64120A MIPS evaluation
 *  board.
 *
 *  Step 1:
 *  First download gdb-5.0.tar.gz from the internet.
 *  and then build/install the package.
 *
 *  Example:
 *    $ tar zxf gdb-5.0.tar.gz
 *    $ cd gdb-5.0
 *    $ ./configure --target=mips-linux-elf
 *    $ make
 *    $ install
 *    $ which mips-linux-elf-gdb
 *    /usr/local/bin/mips-linux-elf-gdb
 *
 *  Step 2:
 *  Configure linux for remote debugging and build it.
 *
 *  Example:
 *    $ cd ~/linux
 *    $ make menuconfig <go to "Kernel Hacking" and turn on remote debugging>
 *    $ make
 *
 *  Step 3:
 *  Download the kernel to the remote target and start
 *  the kernel running. It will promptly halt and wait
 *  for the host gdb session to connect. It does this
 *  since the "Kernel Hacking" option has defined
 *  CONFIG_KGDB which in turn enables your calls
 *  to:
 *     set_debug_traps();
 *     breakpoint();
 *
 *  Step 4:
 *  Start the gdb session on the host.
 *
 *  Example:
 *    $ mips-linux-elf-gdb vmlinux
 *    (gdb) set remotebaud 115200
 *    (gdb) target remote /dev/ttyS1
 *    ...at this point you are connected to
 *       the remote target and can use gdb
 *       in the normal fasion. Setting
 *       breakpoints, single stepping,
 *       printing variables, etc.
 */
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/console.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/reboot.h>

#include <asm/asm.h>
#include <asm/cacheflush.h>
#include <asm/mipsregs.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/gdb-stub.h>
#include <asm/inst.h>
#include <asm/smp.h>

/*
 * external low-level support routines
 */

extern int putDebugChar(char c);    /* write a single character      */
extern char getDebugChar(void);     /* read and return a single char */
extern void trap_low(void);

/*
 * breakpoint and test functions
 */
extern void breakpoint(void);
extern void breakinst(void);
extern void async_breakpoint(void);
extern void async_breakinst(void);
extern void adel(void);

/*
 * local prototypes
 */

static void getpacket(char *buffer);
static void putpacket(char *buffer);
static int computeSignal(int tt);
static int hex(unsigned char ch);
static int hexToInt(char **ptr, int *intValue);
static int hexToLong(char **ptr, long *longValue);
static unsigned char *mem2hex(char *mem, char *buf, int count, int may_fault);
void handle_exception(struct gdb_regs *regs);

int kgdb_enabled;

/*
 * spin locks for smp case
 */
static DEFINE_SPINLOCK(kgdb_lock);
static raw_spinlock_t kgdb_cpulock[NR_CPUS] = {
	[0 ... NR_CPUS-1] = __RAW_SPIN_LOCK_UNLOCKED,
};

/*
 * BUFMAX defines the maximum number of characters in inbound/outbound buffers
 * at least NUMREGBYTES*2 are needed for register packets
 */
#define BUFMAX 2048

static char input_buffer[BUFMAX];
static char output_buffer[BUFMAX];
static int initialized;	/* !0 means we've been initialized */
static int kgdb_started;
static const char hexchars[]="0123456789abcdef";

/* Used to prevent crashes in memory access.  Note that they'll crash anyway if
   we haven't set up fault handlers yet... */
int kgdb_read_byte(unsigned char *address, unsigned char *dest);
int kgdb_write_byte(unsigned char val, unsigned char *dest);

/*
 * Convert ch from a hex digit to an int
 */
static int hex(unsigned char ch)
{
	if (ch >= 'a' && ch <= 'f')
		return ch-'a'+10;
	if (ch >= '0' && ch <= '9')
		return ch-'0';
	if (ch >= 'A' && ch <= 'F')
		return ch-'A'+10;
	return -1;
}

/*
 * scan for the sequence $<data>#<checksum>
 */
static void getpacket(char *buffer)
{
	unsigned char checksum;
	unsigned char xmitcsum;
	int i;
	int count;
	unsigned char ch;

	do {
		/*
		 * wait around for the start character,
		 * ignore all other characters
		 */
		while ((ch = (getDebugChar() & 0x7f)) != '$') ;

		checksum = 0;
		xmitcsum = -1;
		count = 0;

		/*
		 * now, read until a # or end of buffer is found
		 */
		while (count < BUFMAX) {
			ch = getDebugChar();
			if (ch == '#')
				break;
			checksum = checksum + ch;
			buffer[count] = ch;
			count = count + 1;
		}

		if (count >= BUFMAX)
			continue;

		buffer[count] = 0;

		if (ch == '#') {
			xmitcsum = hex(getDebugChar() & 0x7f) << 4;
			xmitcsum |= hex(getDebugChar() & 0x7f);

			if (checksum != xmitcsum)
				putDebugChar('-');	/* failed checksum */
			else {
				putDebugChar('+'); /* successful transfer */

				/*
				 * if a sequence char is present,
				 * reply the sequence ID
				 */
				if (buffer[2] == ':') {
					putDebugChar(buffer[0]);
					putDebugChar(buffer[1]);

					/*
					 * remove sequence chars from buffer
					 */
					count = strlen(buffer);
					for (i=3; i <= count; i++)
						buffer[i-3] = buffer[i];
				}
			}
		}
	}
	while (checksum != xmitcsum);
}

/*
 * send the packet in buffer.
 */
static void putpacket(char *buffer)
{
	unsigned char checksum;
	int count;
	unsigned char ch;

	/*
	 * $<packet info>#<checksum>.
	 */

	do {
		putDebugChar('$');
		checksum = 0;
		count = 0;

		while ((ch = buffer[count]) != 0) {
			if (!(putDebugChar(ch)))
				return;
			checksum += ch;
			count += 1;
		}

		putDebugChar('#');
		putDebugChar(hexchars[checksum >> 4]);
		putDebugChar(hexchars[checksum & 0xf]);

	}
	while ((getDebugChar() & 0x7f) != '+');
}


/*
 * Convert the memory pointed to by mem into hex, placing result in buf.
 * Return a pointer to the last char put in buf (null), in case of mem fault,
 * return 0.
 * may_fault is non-zero if we are reading from arbitrary memory, but is currently
 * not used.
 */
static unsigned char *mem2hex(char *mem, char *buf, int count, int may_fault)
{
	unsigned char ch;

	while (count-- > 0) {
		if (kgdb_read_byte(mem++, &ch) != 0)
			return 0;
		*buf++ = hexchars[ch >> 4];
		*buf++ = hexchars[ch & 0xf];
	}

	*buf = 0;

	return buf;
}

/*
 * convert the hex array pointed to by buf into binary to be placed in mem
 * return a pointer to the character AFTER the last byte written
 * may_fault is non-zero if we are reading from arbitrary memory, but is currently
 * not used.
 */
static char *hex2mem(char *buf, char *mem, int count, int binary, int may_fault)
{
	int i;
	unsigned char ch;

	for (i=0; i<count; i++)
	{
		if (binary) {
			ch = *buf++;
			if (ch == 0x7d)
				ch = 0x20 ^ *buf++;
		}
		else {
			ch = hex(*buf++) << 4;
			ch |= hex(*buf++);
		}
		if (kgdb_write_byte(ch, mem++) != 0)
			return 0;
	}

	return mem;
}

/*
 * This table contains the mapping between SPARC hardware trap types, and
 * signals, which are primarily what GDB understands.  It also indicates
 * which hardware traps we need to commandeer when initializing the stub.
 */
static struct hard_trap_info {
	unsigned char tt;		/* Trap type code for MIPS R3xxx and R4xxx */
	unsigned char signo;		/* Signal that we map this trap into */
} hard_trap_info[] = {
	{ 6, SIGBUS },			/* instruction bus error */
	{ 7, SIGBUS },			/* data bus error */
	{ 9, SIGTRAP },			/* break */
	{ 10, SIGILL },			/* reserved instruction */
/*	{ 11, SIGILL },		*/	/* CPU unusable */
	{ 12, SIGFPE },			/* overflow */
	{ 13, SIGTRAP },		/* trap */
	{ 14, SIGSEGV },		/* virtual instruction cache coherency */
	{ 15, SIGFPE },			/* floating point exception */
	{ 23, SIGSEGV },		/* watch */
	{ 31, SIGSEGV },		/* virtual data cache coherency */
	{ 0, 0}				/* Must be last */
};

/* Save the normal trap handlers for user-mode traps. */
void *saved_vectors[32];

/*
 * Set up exception handlers for tracing and breakpoints
 */
void set_debug_traps(void)
{
	struct hard_trap_info *ht;
	unsigned long flags;
	unsigned char c;

	local_irq_save(flags);
	for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
		saved_vectors[ht->tt] = set_except_vector(ht->tt, trap_low);

	putDebugChar('+'); /* 'hello world' */
	/*
	 * In case GDB is started before us, ack any packets
	 * (presumably "$?#xx") sitting there.
	 */
	while((c = getDebugChar()) != '$');
	while((c = getDebugChar()) != '#');
	c = getDebugChar(); /* eat first csum byte */
	c = getDebugChar(); /* eat second csum byte */
	putDebugChar('+'); /* ack it */

	initialized = 1;
	local_irq_restore(flags);
}

void restore_debug_traps(void)
{
	struct hard_trap_info *ht;
	unsigned long flags;

	local_irq_save(flags);
	for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
		set_except_vector(ht->tt, saved_vectors[ht->tt]);
	local_irq_restore(flags);
}

/*
 * Convert the MIPS hardware trap type code to a Unix signal number.
 */
static int computeSignal(int tt)
{
	struct hard_trap_info *ht;

	for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
		if (ht->tt == tt)
			return ht->signo;

	return SIGHUP;		/* default for things we don't know about */
}

/*
 * While we find nice hex chars, build an int.
 * Return number of chars processed.
 */
static int hexToInt(char **ptr, int *intValue)
{
	int numChars = 0;
	int hexValue;

	*intValue = 0;

	while (**ptr) {
		hexValue = hex(**ptr);
		if (hexValue < 0)
			break;

		*intValue = (*intValue << 4) | hexValue;
		numChars ++;

		(*ptr)++;
	}

	return (numChars);
}

static int hexToLong(char **ptr, long *longValue)
{
	int numChars = 0;
	int hexValue;

	*longValue = 0;

	while (**ptr) {
		hexValue = hex(**ptr);
		if (hexValue < 0)
			break;

		*longValue = (*longValue << 4) | hexValue;
		numChars ++;

		(*ptr)++;
	}

	return numChars;
}


#if 0
/*
 * Print registers (on target console)
 * Used only to debug the stub...
 */
void show_gdbregs(struct gdb_regs * regs)
{
	/*
	 * Saved main processor registers
	 */
	printk("$0 : %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
	       regs->reg0, regs->reg1, regs->reg2, regs->reg3,
	       regs->reg4, regs->reg5, regs->reg6, regs->reg7);
	printk("$8 : %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
	       regs->reg8, regs->reg9, regs->reg10, regs->reg11,
	       regs->reg12, regs->reg13, regs->reg14, regs->reg15);
	printk("$16: %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
	       regs->reg16, regs->reg17, regs->reg18, regs->reg19,
	       regs->reg20, regs->reg21, regs->reg22, regs->reg23);
	printk("$24: %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
	       regs->reg24, regs->reg25, regs->reg26, regs->reg27,
	       regs->reg28, regs->reg29, regs->reg30, regs->reg31);

	/*
	 * Saved cp0 registers
	 */
	printk("epc  : %08lx\nStatus: %08lx\nCause : %08lx\n",
	       regs->cp0_epc, regs->cp0_status, regs->cp0_cause);
}
#endif /* dead code */

/*
 * We single-step by setting breakpoints. When an exception
 * is handled, we need to restore the instructions hoisted
 * when the breakpoints were set.
 *
 * This is where we save the original instructions.
 */
static struct gdb_bp_save {
	unsigned long addr;
	unsigned int val;
} step_bp[2];

#define BP 0x0000000d  /* break opcode */

/*
 * Set breakpoint instructions for single stepping.
 */
static void single_step(struct gdb_regs *regs)
{
	union mips_instruction insn;
	unsigned long targ;
	int is_branch, is_cond, i;

	targ = regs->cp0_epc;
	insn.word = *(unsigned int *)targ;
	is_branch = is_cond = 0;

	switch (insn.i_format.opcode) {
	/*
	 * jr and jalr are in r_format format.
	 */
	case spec_op:
		switch (insn.r_format.func) {
		case jalr_op:
		case jr_op:
			targ = *(&regs->reg0 + insn.r_format.rs);
			is_branch = 1;
			break;
		}
		break;

	/*
	 * This group contains:
	 * bltz_op, bgez_op, bltzl_op, bgezl_op,
	 * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
	 */
	case bcond_op:
		is_branch = is_cond = 1;
		targ += 4 + (insn.i_format.simmediate << 2);
		break;

	/*
	 * These are unconditional and in j_format.
	 */
	case jal_op:
	case j_op:
		is_branch = 1;
		targ += 4;
		targ >>= 28;
		targ <<= 28;
		targ |= (insn.j_format.target << 2);
		break;

	/*
	 * These are conditional.
	 */
	case beq_op:
	case beql_op:
	case bne_op:
	case bnel_op:
	case blez_op:
	case blezl_op:
	case bgtz_op:
	case bgtzl_op:
	case cop0_op:
	case cop1_op:
	case cop2_op:
	case cop1x_op:
		is_branch = is_cond = 1;
		targ += 4 + (insn.i_format.simmediate << 2);
		break;
	}

	if (is_branch) {
		i = 0;
		if (is_cond && targ != (regs->cp0_epc + 8)) {
			step_bp[i].addr = regs->cp0_epc + 8;
			step_bp[i++].val = *(unsigned *)(regs->cp0_epc + 8);
			*(unsigned *)(regs->cp0_epc + 8) = BP;
		}
		step_bp[i].addr = targ;
		step_bp[i].val  = *(unsigned *)targ;
		*(unsigned *)targ = BP;
	} else {
		step_bp[0].addr = regs->cp0_epc + 4;
		step_bp[0].val  = *(unsigned *)(regs->cp0_epc + 4);
		*(unsigned *)(regs->cp0_epc + 4) = BP;
	}
}

/*
 *  If asynchronously interrupted by gdb, then we need to set a breakpoint
 *  at the interrupted instruction so that we wind up stopped with a
 *  reasonable stack frame.
 */
static struct gdb_bp_save async_bp;

/*
 * Swap the interrupted EPC with our asynchronous breakpoint routine.
 * This is safer than stuffing the breakpoint in-place, since no cache
 * flushes (or resulting smp_call_functions) are required.  The
 * assumption is that only one CPU will be handling asynchronous bp's,
 * and only one can be active at a time.
 */
extern spinlock_t smp_call_lock;

void set_async_breakpoint(unsigned long *epc)
{
	/* skip breaking into userland */
	if ((*epc & 0x80000000) == 0)
		return;

#ifdef CONFIG_SMP
	/* avoid deadlock if someone is make IPC */
	if (spin_is_locked(&smp_call_lock))
		return;
#endif

	async_bp.addr = *epc;
	*epc = (unsigned long)async_breakpoint;
}

static void kgdb_wait(void *arg)
{
	unsigned flags;
	int cpu = smp_processor_id();

	local_irq_save(flags);

	__raw_spin_lock(&kgdb_cpulock[cpu]);
	__raw_spin_unlock(&kgdb_cpulock[cpu]);

	local_irq_restore(flags);
}

/*
 * GDB stub needs to call kgdb_wait on all processor with interrupts
 * disabled, so it uses it's own special variant.
 */
static int kgdb_smp_call_kgdb_wait(void)
{
#ifdef CONFIG_SMP
	struct call_data_struct data;
	int i, cpus = num_online_cpus() - 1;
	int cpu = smp_processor_id();

	/*
	 * Can die spectacularly if this CPU isn't yet marked online
	 */
	BUG_ON(!cpu_online(cpu));

	if (!cpus)
		return 0;

	if (spin_is_locked(&smp_call_lock)) {
		/*
		 * Some other processor is trying to make us do something
		 * but we're not going to respond... give up
		 */
		return -1;
		}

	/*
	 * We will continue here, accepting the fact that
	 * the kernel may deadlock if another CPU attempts
	 * to call smp_call_function now...
	 */

	data.func = kgdb_wait;
	data.info = NULL;
	atomic_set(&data.started, 0);
	data.wait = 0;

	spin_lock(&smp_call_lock);
	call_data = &data;
	mb();

	/* Send a message to all other CPUs and wait for them to respond */
	for (i = 0; i < NR_CPUS; i++)
		if (cpu_online(i) && i != cpu)
			core_send_ipi(i, SMP_CALL_FUNCTION);

	/* Wait for response */
	/* FIXME: lock-up detection, backtrace on lock-up */
	while (atomic_read(&data.started) != cpus)
		barrier();

	call_data = NULL;
	spin_unlock(&smp_call_lock);
#endif

	return 0;
}

/*
 * This function does all command processing for interfacing to gdb.  It
 * returns 1 if you should skip the instruction at the trap address, 0
 * otherwise.
 */
void handle_exception(struct gdb_regs *regs)
{
	int trap;			/* Trap type */
	int sigval;
	long addr;
	int length;
	char *ptr;
	unsigned long *stack;
	int i;
	int bflag = 0;

	kgdb_started = 1;

	/*
	 * acquire the big kgdb spinlock
	 */
	if (!spin_trylock(&kgdb_lock)) {
		/*
		 * some other CPU has the lock, we should go back to
		 * receive the gdb_wait IPC
		 */
		return;
	}

	/*
	 * If we're in async_breakpoint(), restore the real EPC from
	 * the breakpoint.
	 */
	if (regs->cp0_epc == (unsigned long)async_breakinst) {
		regs->cp0_epc = async_bp.addr;
		async_bp.addr = 0;
	}

	/*
	 * acquire the CPU spinlocks
	 */
	for (i = num_online_cpus()-1; i >= 0; i--)
		if (__raw_spin_trylock(&kgdb_cpulock[i]) == 0)
			panic("kgdb: couldn't get cpulock %d\n", i);

	/*
	 * force other cpus to enter kgdb
	 */
	kgdb_smp_call_kgdb_wait();

	/*
	 * If we're in breakpoint() increment the PC
	 */
	trap = (regs->cp0_cause & 0x7c) >> 2;
	if (trap == 9 && regs->cp0_epc == (unsigned long)breakinst)
		regs->cp0_epc += 4;

	/*
	 * If we were single_stepping, restore the opcodes hoisted
	 * for the breakpoint[s].
	 */
	if (step_bp[0].addr) {
		*(unsigned *)step_bp[0].addr = step_bp[0].val;
		step_bp[0].addr = 0;

		if (step_bp[1].addr) {
			*(unsigned *)step_bp[1].addr = step_bp[1].val;
			step_bp[1].addr = 0;
		}
	}

	stack = (long *)regs->reg29;			/* stack ptr */
	sigval = computeSignal(trap);

	/*
	 * reply to host that an exception has occurred
	 */
	ptr = output_buffer;

	/*
	 * Send trap type (converted to signal)
	 */
	*ptr++ = 'T';
	*ptr++ = hexchars[sigval >> 4];
	*ptr++ = hexchars[sigval & 0xf];

	/*
	 * Send Error PC
	 */
	*ptr++ = hexchars[REG_EPC >> 4];
	*ptr++ = hexchars[REG_EPC & 0xf];
	*ptr++ = ':';
	ptr = mem2hex((char *)&regs->cp0_epc, ptr, sizeof(long), 0);
	*ptr++ = ';';

	/*
	 * Send frame pointer
	 */
	*ptr++ = hexchars[REG_FP >> 4];
	*ptr++ = hexchars[REG_FP & 0xf];
	*ptr++ = ':';
	ptr = mem2hex((char *)&regs->reg30, ptr, sizeof(long), 0);
	*ptr++ = ';';

	/*
	 * Send stack pointer
	 */
	*ptr++ = hexchars[REG_SP >> 4];
	*ptr++ = hexchars[REG_SP & 0xf];
	*ptr++ = ':';
	ptr = mem2hex((char *)&regs->reg29, ptr, sizeof(long), 0);
	*ptr++ = ';';

	*ptr++ = 0;
	putpacket(output_buffer);	/* send it off... */

	/*
	 * Wait for input from remote GDB
	 */
	while (1) {
		output_buffer[0] = 0;
		getpacket(input_buffer);

		switch (input_buffer[0])
		{
		case '?':
			output_buffer[0] = 'S';
			output_buffer[1] = hexchars[sigval >> 4];
			output_buffer[2] = hexchars[sigval & 0xf];
			output_buffer[3] = 0;
			break;

		/*
		 * Detach debugger; let CPU run
		 */
		case 'D':
			putpacket(output_buffer);
			goto finish_kgdb;
			break;

		case 'd':
			/* toggle debug flag */
			break;

		/*
		 * Return the value of the CPU registers
		 */
		case 'g':
			ptr = output_buffer;
			ptr = mem2hex((char *)&regs->reg0, ptr, 32*sizeof(long), 0); /* r0...r31 */
			ptr = mem2hex((char *)&regs->cp0_status, ptr, 6*sizeof(long), 0); /* cp0 */
			ptr = mem2hex((char *)&regs->fpr0, ptr, 32*sizeof(long), 0); /* f0...31 */
			ptr = mem2hex((char *)&regs->cp1_fsr, ptr, 2*sizeof(long), 0); /* cp1 */
			ptr = mem2hex((char *)&regs->frame_ptr, ptr, 2*sizeof(long), 0); /* frp */
			ptr = mem2hex((char *)&regs->cp0_index, ptr, 16*sizeof(long), 0); /* cp0 */
			break;

		/*
		 * set the value of the CPU registers - return OK
		 */
		case 'G':
		{
			ptr = &input_buffer[1];
			hex2mem(ptr, (char *)&regs->reg0, 32*sizeof(long), 0, 0);
			ptr += 32*(2*sizeof(long));
			hex2mem(ptr, (char *)&regs->cp0_status, 6*sizeof(long), 0, 0);
			ptr += 6*(2*sizeof(long));
			hex2mem(ptr, (char *)&regs->fpr0, 32*sizeof(long), 0, 0);
			ptr += 32*(2*sizeof(long));
			hex2mem(ptr, (char *)&regs->cp1_fsr, 2*sizeof(long), 0, 0);
			ptr += 2*(2*sizeof(long));
			hex2mem(ptr, (char *)&regs->frame_ptr, 2*sizeof(long), 0, 0);
			ptr += 2*(2*sizeof(long));
			hex2mem(ptr, (char *)&regs->cp0_index, 16*sizeof(long), 0, 0);
			strcpy(output_buffer, "OK");
		 }
		break;

		/*
		 * mAA..AA,LLLL  Read LLLL bytes at address AA..AA
		 */
		case 'm':
			ptr = &input_buffer[1];

			if (hexToLong(&ptr, &addr)
				&& *ptr++ == ','
				&& hexToInt(&ptr, &length)) {
				if (mem2hex((char *)addr, output_buffer, length, 1))
					break;
				strcpy(output_buffer, "E03");
			} else
				strcpy(output_buffer, "E01");
			break;

		/*
		 * XAA..AA,LLLL: Write LLLL escaped binary bytes at address AA.AA
		 */
		case 'X':
			bflag = 1;
			/* fall through */

		/*
		 * MAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK
		 */
		case 'M':
			ptr = &input_buffer[1];

			if (hexToLong(&ptr, &addr)
				&& *ptr++ == ','
				&& hexToInt(&ptr, &length)
				&& *ptr++ == ':') {
				if (hex2mem(ptr, (char *)addr, length, bflag, 1))
					strcpy(output_buffer, "OK");
				else
					strcpy(output_buffer, "E03");
			}
			else
				strcpy(output_buffer, "E02");
			break;

		/*
		 * cAA..AA    Continue at address AA..AA(optional)
		 */
		case 'c':
			/* try to read optional parameter, pc unchanged if no parm */

			ptr = &input_buffer[1];
			if (hexToLong(&ptr, &addr))
				regs->cp0_epc = addr;

			goto exit_kgdb_exception;
			break;

		/*
		 * kill the program; let us try to restart the machine
		 * Reset the whole machine.
		 */
		case 'k':
		case 'r':
			machine_restart("kgdb restarts machine");
			break;

		/*
		 * Step to next instruction
		 */
		case 's':
			/*
			 * There is no single step insn in the MIPS ISA, so we
			 * use breakpoints and continue, instead.
			 */
			single_step(regs);
			goto exit_kgdb_exception;
			/* NOTREACHED */
			break;

		/*
		 * Set baud rate (bBB)
		 * FIXME: Needs to be written
		 */
		case 'b':
		{
#if 0
			int baudrate;
			extern void set_timer_3();

			ptr = &input_buffer[1];
			if (!hexToInt(&ptr, &baudrate))
			{
				strcpy(output_buffer, "B01");
				break;
			}

			/* Convert baud rate to uart clock divider */

			switch (baudrate)
			{
				case 38400:
					baudrate = 16;
					break;
				case 19200:
					baudrate = 33;
					break;
				case 9600:
					baudrate = 65;
					break;
				default:
					baudrate = 0;
					strcpy(output_buffer, "B02");
					goto x1;
			}

			if (baudrate) {
				putpacket("OK");	/* Ack before changing speed */
				set_timer_3(baudrate); /* Set it */
			}
#endif
		}
		break;

		}			/* switch */

		/*
		 * reply to the request
		 */

		putpacket(output_buffer);

	} /* while */

	return;

finish_kgdb:
	restore_debug_traps();

exit_kgdb_exception:
	/* release locks so other CPUs can go */
	for (i = num_online_cpus()-1; i >= 0; i--)
		__raw_spin_unlock(&kgdb_cpulock[i]);
	spin_unlock(&kgdb_lock);

	__flush_cache_all();
	return;
}

/*
 * This function will generate a breakpoint exception.  It is used at the
 * beginning of a program to sync up with a debugger and can be used
 * otherwise as a quick means to stop program execution and "break" into
 * the debugger.
 */
void breakpoint(void)
{
	if (!initialized)
		return;

	__asm__ __volatile__(
			".globl	breakinst\n\t"
			".set\tnoreorder\n\t"
			"nop\n"
			"breakinst:\tbreak\n\t"
			"nop\n\t"
			".set\treorder"
			);
}

/* Nothing but the break; don't pollute any registers */
void async_breakpoint(void)
{
	__asm__ __volatile__(
			".globl	async_breakinst\n\t"
			".set\tnoreorder\n\t"
			"nop\n"
			"async_breakinst:\tbreak\n\t"
			"nop\n\t"
			".set\treorder"
			);
}

void adel(void)
{
	__asm__ __volatile__(
			".globl\tadel\n\t"
			"lui\t$8,0x8000\n\t"
			"lw\t$9,1($8)\n\t"
			);
}

/*
 * malloc is needed by gdb client in "call func()", even a private one
 * will make gdb happy
 */
static void __used *malloc(size_t size)
{
	return kmalloc(size, GFP_ATOMIC);
}

static void __used free(void *where)
{
	kfree(where);
}

#ifdef CONFIG_GDB_CONSOLE

void gdb_putsn(const char *str, int l)
{
	char outbuf[18];

	if (!kgdb_started)
		return;

	outbuf[0]='O';

	while(l) {
		int i = (l>8)?8:l;
		mem2hex((char *)str, &outbuf[1], i, 0);
		outbuf[(i*2)+1]=0;
		putpacket(outbuf);
		str += i;
		l -= i;
	}
}

static void gdb_console_write(struct console *con, const char *s, unsigned n)
{
	gdb_putsn(s, n);
}

static struct console gdb_console = {
	.name	= "gdb",
	.write	= gdb_console_write,
	.flags	= CON_PRINTBUFFER,
	.index	= -1
};

static int __init register_gdb_console(void)
{
	register_console(&gdb_console);

	return 0;
}

console_initcall(register_gdb_console);

#endif