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*/
1 /*
2 * arch/mips/kernel/gdb-stub.c
3 *
4 * Originally written by Glenn Engel, Lake Stevens Instrument Division
5 *
6 * Contributed by HP Systems
7 *
8 * Modified for SPARC by Stu Grossman, Cygnus Support.
9 *
10 * Modified for Linux/MIPS (and MIPS in general) by Andreas Busse
11 * Send complaints, suggestions etc. to <andy@waldorf-gmbh.de>
12 *
13 * Copyright (C) 1995 Andreas Busse
14 */
15
16 /*
17 * To enable debugger support, two things need to happen. One, a
18 * call to set_debug_traps() is necessary in order to allow any breakpoints
19 * or error conditions to be properly intercepted and reported to gdb.
20 * Two, a breakpoint needs to be generated to begin communication. This
21 * is most easily accomplished by a call to breakpoint(). Breakpoint()
22 * simulates a breakpoint by executing a BREAK instruction.
23 *
24 *
25 * The following gdb commands are supported:
26 *
27 * command function Return value
28 *
29 * g return the value of the CPU registers hex data or ENN
30 * G set the value of the CPU registers OK or ENN
31 *
32 * mAA..AA,LLLL Read LLLL bytes at address AA..AA hex data or ENN
33 * MAA..AA,LLLL: Write LLLL bytes at address AA.AA OK or ENN
34 *
35 * c Resume at current address SNN ( signal NN)
36 * cAA..AA Continue at address AA..AA SNN
37 *
38 * s Step one instruction SNN
39 * sAA..AA Step one instruction from AA..AA SNN
40 *
41 * k kill
42 *
43 * ? What was the last sigval ? SNN (signal NN)
44 *
45 * bBB..BB Set baud rate to BB..BB OK or BNN, then sets
46 * baud rate
47 *
48 * All commands and responses are sent with a packet which includes a
49 * checksum. A packet consists of
50 *
51 * $<packet info>#<checksum>.
52 *
53 * where
54 * <packet info> :: <characters representing the command or response>
55 * <checksum> :: < two hex digits computed as modulo 256 sum of <packetinfo>>
56 *
57 * When a packet is received, it is first acknowledged with either '+' or '-'.
58 * '+' indicates a successful transfer. '-' indicates a failed transfer.
59 *
60 * Example:
61 *
62 * Host: Reply:
63 * $m0,10#2a +$00010203040506070809101112131415#42
64 *
65 */
66
67 #include <linux/string.h>
68 #include <linux/signal.h>
69 #include <linux/kernel.h>
70
71 #include <asm/asm.h>
72 #include <asm/mipsregs.h>
73 #include <asm/segment.h>
74 #include <asm/cachectl.h>
75 #include <asm/system.h>
76 #include <asm/gdb-stub.h>
77
78 /*
79 * external low-level support routines
80 */
81
82 extern int putDebugChar(char c); /* write a single character */
83 extern char getDebugChar(void); /* read and return a single char */
84 extern void fltr_set_mem_err(void);
85 extern void trap_low(void);
86
87 /*
88 * breakpoint and test functions
89 */
90 extern void breakpoint(void);
91 extern void breakinst(void);
92 extern void adel(void);
93
94 /*
95 * local prototypes
96 */
97
98 static void getpacket(char *buffer);
99 static void putpacket(char *buffer);
100 static void set_mem_fault_trap(int enable);
101 static int computeSignal(int tt);
102 static int hex(unsigned char ch);
103 static int hexToInt(char **ptr, int *intValue);
104 static unsigned char *mem2hex(char *mem, char *buf, int count, int may_fault);
105 void handle_exception(struct gdb_regs *regs);
106 static void show_gdbregs(struct gdb_regs *regs);
107
108 /*
109 * BUFMAX defines the maximum number of characters in inbound/outbound buffers
110 * at least NUMREGBYTES*2 are needed for register packets
111 */
112 #define BUFMAX 2048
113
114 static char input_buffer[BUFMAX];
115 static char output_buffer[BUFMAX];
116 static int initialized = 0; /* !0 means we've been initialized */
117 static const char hexchars[]="0123456789abcdef";
118
119
120 /*
121 * Convert ch from a hex digit to an int
122 */
123 static int hex(unsigned char ch)
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*/
124 {
125 if (ch >= 'a' && ch <= 'f')
126 return ch-'a'+10;
127 if (ch >= '0' && ch <= '9')
128 return ch-'0';
129 if (ch >= 'A' && ch <= 'F')
130 return ch-'A'+10;
131 return -1;
132 }
133
134 /*
135 * scan for the sequence $<data>#<checksum>
136 */
137 static void getpacket(char *buffer)
/* ![[previous]](../icons/left.png)
*/
138 {
139 unsigned char checksum;
140 unsigned char xmitcsum;
141 int i;
142 int count;
143 unsigned char ch;
144
145 do {
146 /*
147 * wait around for the start character,
148 * ignore all other characters
149 */
150 while ((ch = (getDebugChar() & 0x7f)) != '$') ;
151
152 checksum = 0;
153 xmitcsum = -1;
154 count = 0;
155
156 /*
157 * now, read until a # or end of buffer is found
158 */
159 while (count < BUFMAX) {
160 ch = getDebugChar() & 0x7f;
161 if (ch == '#')
162 break;
163 checksum = checksum + ch;
164 buffer[count] = ch;
165 count = count + 1;
166 }
167
168 if (count >= BUFMAX)
169 continue;
170
171 buffer[count] = 0;
172
173 if (ch == '#') {
174 xmitcsum = hex(getDebugChar() & 0x7f) << 4;
175 xmitcsum |= hex(getDebugChar() & 0x7f);
176
177 if (checksum != xmitcsum)
178 putDebugChar('-'); /* failed checksum */
179 else {
180 putDebugChar('+'); /* successful transfer */
181
182 /*
183 * if a sequence char is present,
184 * reply the sequence ID
185 */
186 if (buffer[2] == ':') {
187 putDebugChar(buffer[0]);
188 putDebugChar(buffer[1]);
189
190 /*
191 * remove sequence chars from buffer
192 */
193 count = strlen(buffer);
194 for (i=3; i <= count; i++)
195 buffer[i-3] = buffer[i];
196 }
197 }
198 }
199 }
200 while (checksum != xmitcsum);
201 }
202
203 /*
204 * send the packet in buffer.
205 */
206 static void putpacket(char *buffer)
/* */
207 {
208 unsigned char checksum;
209 int count;
210 unsigned char ch;
211
212 /*
213 * $<packet info>#<checksum>.
214 */
215
216 do {
217 putDebugChar('$');
218 checksum = 0;
219 count = 0;
220
221 while ((ch = buffer[count]) != 0) {
222 if (!(putDebugChar(ch)))
223 return;
224 checksum += ch;
225 count += 1;
226 }
227
228 putDebugChar('#');
229 putDebugChar(hexchars[checksum >> 4]);
230 putDebugChar(hexchars[checksum & 0xf]);
231
232 }
233 while ((getDebugChar() & 0x7f) != '+');
234 }
235
236
237 /*
238 * Indicate to caller of mem2hex or hex2mem that there
239 * has been an error.
240 */
241 static volatile int mem_err = 0;
242
243 /*
244 * Convert the memory pointed to by mem into hex, placing result in buf.
245 * Return a pointer to the last char put in buf (null), in case of mem fault,
246 * return 0.
247 * If MAY_FAULT is non-zero, then we will handle memory faults by returning
248 * a 0, else treat a fault like any other fault in the stub.
249 */
250 static unsigned char *mem2hex(char *mem, char *buf, int count, int may_fault)
/* */
251 {
252 unsigned char ch;
253
254 /* set_mem_fault_trap(may_fault); */
255
256 while (count-- > 0) {
257 ch = *(mem++);
258 if (mem_err)
259 return 0;
260 *buf++ = hexchars[ch >> 4];
261 *buf++ = hexchars[ch & 0xf];
262 }
263
264 *buf = 0;
265
266 /* set_mem_fault_trap(0); */
267
268 return buf;
269 }
270
271 /*
272 * convert the hex array pointed to by buf into binary to be placed in mem
273 * return a pointer to the character AFTER the last byte written
274 */
275 static char *hex2mem(char *buf, char *mem, int count, int may_fault)
/* */
276 {
277 int i;
278 unsigned char ch;
279
280 /* set_mem_fault_trap(may_fault); */
281
282 for (i=0; i<count; i++)
283 {
284 ch = hex(*buf++) << 4;
285 ch |= hex(*buf++);
286 *(mem++) = ch;
287 if (mem_err)
288 return 0;
289 }
290
291 /* set_mem_fault_trap(0); */
292
293 return mem;
294 }
295
296 /*
297 * This table contains the mapping between SPARC hardware trap types, and
298 * signals, which are primarily what GDB understands. It also indicates
299 * which hardware traps we need to commandeer when initializing the stub.
300 */
301 static struct hard_trap_info
302 {
303 unsigned char tt; /* Trap type code for MIPS R3xxx and R4xxx */
304 unsigned char signo; /* Signal that we map this trap into */
305 } hard_trap_info[] = {
306 { 4, SIGBUS }, /* address error (load) */
307 { 5, SIGBUS }, /* address error (store) */
308 { 6, SIGBUS }, /* instruction bus error */
309 { 7, SIGBUS }, /* data bus error */
310 { 9, SIGTRAP }, /* break */
311 { 10, SIGILL }, /* reserved instruction */
312 /* { 11, SIGILL }, */ /* cpu unusable */
313 { 12, SIGFPE }, /* overflow */
314 { 13, SIGTRAP }, /* trap */
315 { 14, SIGSEGV }, /* virtual instruction cache coherency */
316 { 15, SIGFPE }, /* floating point exception */
317 { 23, SIGSEGV }, /* watch */
318 { 31, SIGSEGV }, /* virtual data cache coherency */
319 { 0, 0} /* Must be last */
320 };
321
322
323 /*
324 * Set up exception handlers for tracing and breakpoints
325 */
326 void set_debug_traps(void)
/* */
327 {
328 struct hard_trap_info *ht;
329
330 for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
331 set_except_vector(ht->tt, trap_low);
332
333 /*
334 * In case GDB is started before us, ack any packets
335 * (presumably "$?#xx") sitting there.
336 */
337
338 putDebugChar ('+');
339 initialized = 1;
340
341 breakpoint();
342 }
343
344
345 /*
346 * Trap handler for memory errors. This just sets mem_err to be non-zero. It
347 * assumes that %l1 is non-zero. This should be safe, as it is doubtful that
348 * 0 would ever contain code that could mem fault. This routine will skip
349 * past the faulting instruction after setting mem_err.
350 */
351 extern void fltr_set_mem_err(void)
/* */
352 {
353 /* FIXME: Needs to be written... */
354 }
355
356
357 static void set_mem_fault_trap(int enable)
/* */
358 {
359 mem_err = 0;
360
361 #if 0
362 if (enable)
363 exceptionHandler(9, fltr_set_mem_err);
364 else
365 exceptionHandler(9, trap_low);
366 #endif
367 }
368
369 /*
370 * Convert the MIPS hardware trap type code to a unix signal number.
371 */
372 static int computeSignal(int tt)
/* */
373 {
374 struct hard_trap_info *ht;
375
376 for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
377 if (ht->tt == tt)
378 return ht->signo;
379
380 return SIGHUP; /* default for things we don't know about */
381 }
382
383 /*
384 * While we find nice hex chars, build an int.
385 * Return number of chars processed.
386 */
387 static int hexToInt(char **ptr, int *intValue)
/* */
388 {
389 int numChars = 0;
390 int hexValue;
391
392 *intValue = 0;
393
394 while (**ptr)
395 {
396 hexValue = hex(**ptr);
397 if (hexValue < 0)
398 break;
399
400 *intValue = (*intValue << 4) | hexValue;
401 numChars ++;
402
403 (*ptr)++;
404 }
405
406 return (numChars);
407 }
408
409 /*
410 * This function does all command procesing for interfacing to gdb. It
411 * returns 1 if you should skip the instruction at the trap address, 0
412 * otherwise.
413 */
414 void handle_exception (struct gdb_regs *regs)
/* */
415 {
416 int trap; /* Trap type */
417 int sigval;
418 int addr;
419 int length;
420 char *ptr;
421 unsigned long *stack;
422
423 #if 0
424 printk("in handle_exception()\n");
425 show_gdbregs(regs);
426 #endif
427
428 /*
429 * First check trap type. If this is CPU_UNUSABLE and CPU_ID is 1,
430 * the simply switch the FPU on and return since this is no error
431 * condition. kernel/traps.c does the same.
432 * FIXME: This doesn't work yet, so we don't catch CPU_UNUSABLE
433 * traps for now.
434 */
435 trap = (regs->cp0_cause & 0x7c) >> 2;
436 /* printk("trap=%d\n",trap); */
437 if (trap == 11) {
438 if (((regs->cp0_cause >> CAUSEB_CE) & 3) == 1) {
439 regs->cp0_status |= ST0_CU1;
440 return;
441 }
442 }
443
444 /*
445 * If we're in breakpoint() increment the PC
446 */
447 if (trap == 9 && regs->cp0_epc == (unsigned long)breakinst)
448 regs->cp0_epc += 4;
449
450 stack = (long *)regs->reg29; /* stack ptr */
451 sigval = computeSignal(trap);
452
453 /*
454 * reply to host that an exception has occurred
455 */
456 ptr = output_buffer;
457
458 /*
459 * Send trap type (converted to signal)
460 */
461 *ptr++ = 'T';
462 *ptr++ = hexchars[sigval >> 4];
463 *ptr++ = hexchars[sigval & 0xf];
464
465 /*
466 * Send Error PC
467 */
468 *ptr++ = hexchars[REG_EPC >> 4];
469 *ptr++ = hexchars[REG_EPC & 0xf];
470 *ptr++ = ':';
471 ptr = mem2hex((char *)®s->cp0_epc, ptr, 4, 0);
472 *ptr++ = ';';
473
474 /*
475 * Send frame pointer
476 */
477 *ptr++ = hexchars[REG_FP >> 4];
478 *ptr++ = hexchars[REG_FP & 0xf];
479 *ptr++ = ':';
480 ptr = mem2hex((char *)®s->reg30, ptr, 4, 0);
481 *ptr++ = ';';
482
483 /*
484 * Send stack pointer
485 */
486 *ptr++ = hexchars[REG_SP >> 4];
487 *ptr++ = hexchars[REG_SP & 0xf];
488 *ptr++ = ':';
489 ptr = mem2hex((char *)®s->reg29, ptr, 4, 0);
490 *ptr++ = ';';
491
492 *ptr++ = 0;
493 putpacket(output_buffer); /* send it off... */
494
495 /*
496 * Wait for input from remote GDB
497 */
498 while (1) {
499 output_buffer[0] = 0;
500 getpacket(input_buffer);
501
502 switch (input_buffer[0])
503 {
504 case '?':
505 output_buffer[0] = 'S';
506 output_buffer[1] = hexchars[sigval >> 4];
507 output_buffer[2] = hexchars[sigval & 0xf];
508 output_buffer[3] = 0;
509 break;
510
511 case 'd':
512 /* toggle debug flag */
513 break;
514
515 /*
516 * Return the value of the CPU registers
517 */
518 case 'g':
519 ptr = output_buffer;
520 ptr = mem2hex((char *)®s->reg0, ptr, 32*4, 0); /* r0...r31 */
521 ptr = mem2hex((char *)®s->cp0_status, ptr, 6*4, 0); /* cp0 */
522 ptr = mem2hex((char *)®s->fpr0, ptr, 32*4, 0); /* f0...31 */
523 ptr = mem2hex((char *)®s->cp1_fsr, ptr, 2*4, 0); /* cp1 */
524 ptr = mem2hex((char *)®s->frame_ptr, ptr, 2*4, 0); /* frp */
525 ptr = mem2hex((char *)®s->cp0_index, ptr, 16*4, 0); /* cp0 */
526 break;
527
528 /*
529 * set the value of the CPU registers - return OK
530 * FIXME: Needs to be written
531 */
532 case 'G':
533 {
534 #if 0
535 unsigned long *newsp, psr;
536
537 ptr = &input_buffer[1];
538 hex2mem(ptr, (char *)registers, 16 * 4, 0); /* G & O regs */
539
540 /*
541 * See if the stack pointer has moved. If so, then copy the
542 * saved locals and ins to the new location.
543 */
544
545 newsp = (unsigned long *)registers[SP];
546 if (sp != newsp)
547 sp = memcpy(newsp, sp, 16 * 4);
548
549 #endif
550 strcpy(output_buffer,"OK");
551 }
552 break;
553
554 /*
555 * mAA..AA,LLLL Read LLLL bytes at address AA..AA
556 */
557 case 'm':
558 ptr = &input_buffer[1];
559
560 if (hexToInt(&ptr, &addr)
561 && *ptr++ == ','
562 && hexToInt(&ptr, &length)) {
563 if (mem2hex((char *)addr, output_buffer, length, 1))
564 break;
565 strcpy (output_buffer, "E03");
566 } else
567 strcpy(output_buffer,"E01");
568 break;
569
570 /*
571 * MAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK
572 */
573 case 'M':
574 ptr = &input_buffer[1];
575
576 if (hexToInt(&ptr, &addr)
577 && *ptr++ == ','
578 && hexToInt(&ptr, &length)
579 && *ptr++ == ':') {
580 if (hex2mem(ptr, (char *)addr, length, 1))
581 strcpy(output_buffer, "OK");
582 else
583 strcpy(output_buffer, "E03");
584 }
585 else
586 strcpy(output_buffer, "E02");
587 break;
588
589 /*
590 * cAA..AA Continue at address AA..AA(optional)
591 */
592 case 'c':
593 /* try to read optional parameter, pc unchanged if no parm */
594
595 ptr = &input_buffer[1];
596 if (hexToInt(&ptr, &addr))
597 regs->cp0_epc = addr;
598
599 /*
600 * Need to flush the instruction cache here, as we may
601 * have deposited a breakpoint, and the icache probably
602 * has no way of knowing that a data ref to some location
603 * may have changed something that is in the instruction
604 * cache.
605 * NB: We flush both caches, just to be sure...
606 */
607
608 sys_cacheflush((void *)KSEG0,KSEG1-KSEG0,BCACHE);
609 return;
610 /* NOTREACHED */
611 break;
612
613
614 /*
615 * kill the program
616 */
617 case 'k' :
618 break; /* do nothing */
619
620
621 /*
622 * Reset the whole machine (FIXME: system dependent)
623 */
624 case 'r':
625 break;
626
627
628 /*
629 * Step to next instruction
630 * FIXME: Needs to be written
631 */
632 case 's':
633 strcpy (output_buffer, "S01");
634 break;
635
636 /*
637 * Set baud rate (bBB)
638 * FIXME: Needs to be written
639 */
640 case 'b':
641 {
642 #if 0
643 int baudrate;
644 extern void set_timer_3();
645
646 ptr = &input_buffer[1];
647 if (!hexToInt(&ptr, &baudrate))
648 {
649 strcpy(output_buffer,"B01");
650 break;
651 }
652
653 /* Convert baud rate to uart clock divider */
654
655 switch (baudrate)
656 {
657 case 38400:
658 baudrate = 16;
659 break;
660 case 19200:
661 baudrate = 33;
662 break;
663 case 9600:
664 baudrate = 65;
665 break;
666 default:
667 baudrate = 0;
668 strcpy(output_buffer,"B02");
669 goto x1;
670 }
671
672 if (baudrate) {
673 putpacket("OK"); /* Ack before changing speed */
674 set_timer_3(baudrate); /* Set it */
675 }
676 #endif
677 }
678 break;
679
680 } /* switch */
681
682 /*
683 * reply to the request
684 */
685
686 putpacket(output_buffer);
687
688 } /* while */
689 }
690
691 /*
692 * This function will generate a breakpoint exception. It is used at the
693 * beginning of a program to sync up with a debugger and can be used
694 * otherwise as a quick means to stop program execution and "break" into
695 * the debugger.
696 */
697 void breakpoint(void)
/* */
698 {
699 if (!initialized)
700 return;
701
702 __asm__ __volatile__("
703 .globl breakinst
704 .set noreorder
705 nop
706 breakinst: break
707 nop
708 .set reorder
709 ");
710 }
711
712 void adel(void)
/* */
713 {
714 __asm__ __volatile__("
715 .globl adel
716 la $8,0x80000001
717 lw $9,0($8)
718 ");
719 }
720
721 /*
722 * Print registers (on target console)
723 * Used only to debug the stub...
724 */
725 void show_gdbregs(struct gdb_regs * regs)
/* ![[last]](../icons/n_last.png)
*/
726 {
727 /*
728 * Saved main processor registers
729 */
730 printk("$0 : %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
731 regs->reg0, regs->reg1, regs->reg2, regs->reg3,
732 regs->reg4, regs->reg5, regs->reg6, regs->reg7);
733 printk("$8 : %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
734 regs->reg8, regs->reg9, regs->reg10, regs->reg11,
735 regs->reg12, regs->reg13, regs->reg14, regs->reg15);
736 printk("$16: %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
737 regs->reg16, regs->reg17, regs->reg18, regs->reg19,
738 regs->reg20, regs->reg21, regs->reg22, regs->reg23);
739 printk("$24: %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
740 regs->reg24, regs->reg25, regs->reg26, regs->reg27,
741 regs->reg28, regs->reg29, regs->reg30, regs->reg31);
742
743 /*
744 * Saved cp0 registers
745 */
746 printk("epc : %08lx\nStatus: %08lx\nCause : %08lx\n",
747 regs->cp0_epc, regs->cp0_status, regs->cp0_cause);
748 }
![[bottom]](../icons/n_bottom.png){kind=icon}
*/