gdb/sparc-stub.c

   1 /****************************************************************************
   2
   3                 THIS SOFTWARE IS NOT COPYRIGHTED
   4
   5    HP offers the following for use in the public domain.  HP makes no
   6    warranty with regard to the software or it's performance and the
   7    user accepts the software "AS IS" with all faults.
   8
   9    HP DISCLAIMS ANY WARRANTIES, EXPRESS OR IMPLIED, WITH REGARD
  10    TO THIS SOFTWARE INCLUDING BUT NOT LIMITED TO THE WARRANTIES
  11    OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  12
  13 ****************************************************************************/
  14
  15 /****************************************************************************
  16  *  Header: remcom.c,v 1.34 91/03/09 12:29:49 glenne Exp $
  17  *
  18  *  Module name: remcom.c $
  19  *  Revision: 1.34 $
  20  *  Date: 91/03/09 12:29:49 $
  21  *  Contributor:     Lake Stevens Instrument Division$
  22  *
  23  *  Description:     low level support for gdb debugger. $
  24  *
  25  *  Considerations:  only works on target hardware $
  26  *
  27  *  Written by:      Glenn Engel $
  28  *  ModuleState:     Experimental $
  29  *
  30  *  NOTES:           See Below $
  31  *
  32  *  Modified for SPARC by Stu Grossman, Cygnus Support.
  33  *
  34  *  This code has been extensively tested on the Fujitsu SPARClite demo board.
  35  *
  36  *  To enable debugger support, two things need to happen.  One, a
  37  *  call to set_debug_traps() is necessary in order to allow any breakpoints
  38  *  or error conditions to be properly intercepted and reported to gdb.
  39  *  Two, a breakpoint needs to be generated to begin communication.  This
  40  *  is most easily accomplished by a call to breakpoint().  Breakpoint()
  41  *  simulates a breakpoint by executing a trap #1.
  42  *
  43  *************
  44  *
  45  *    The following gdb commands are supported:
  46  *
  47  * command          function                               Return value
  48  *
  49  *    g             return the value of the CPU registers  hex data or ENN
  50  *    G             set the value of the CPU registers     OK or ENN
  51  *
  52  *    mAA..AA,LLLL  Read LLLL bytes at address AA..AA      hex data or ENN
  53  *    MAA..AA,LLLL: Write LLLL bytes at address AA.AA      OK or ENN
  54  *
  55  *    c             Resume at current address              SNN   ( signal NN)
  56  *    cAA..AA       Continue at address AA..AA             SNN
  57  *
  58  *    s             Step one instruction                   SNN
  59  *    sAA..AA       Step one instruction from AA..AA       SNN
  60  *
  61  *    k             kill
  62  *
  63  *    ?             What was the last sigval ?             SNN   (signal NN)
  64  *
  65  * All commands and responses are sent with a packet which includes a
  66  * checksum.  A packet consists of
  67  *
  68  * $<packet info>#<checksum>.
  69  *
  70  * where
  71  * <packet info> :: <characters representing the command or response>
  72  * <checksum>    :: < two hex digits computed as modulo 256 sum of <packetinfo>>
  73  *
  74  * When a packet is received, it is first acknowledged with either '+' or '-'.
  75  * '+' indicates a successful transfer.  '-' indicates a failed transfer.
  76  *
  77  * Example:
  78  *
  79  * Host:                  Reply:
  80  * $m0,10#2a               +$00010203040506070809101112131415#42
  81  *
  82  ****************************************************************************/
  83
  84 #include <string.h>
  85 #include <signal.h>
  86
  87 /************************************************************************
  88  *
  89  * external low-level support routines
  90  */
  91
  92 extern void putDebugChar();     /* write a single character      */
  93 extern int getDebugChar();      /* read and return a single char */
  94
  95 /************************************************************************/
  96 /* BUFMAX defines the maximum number of characters in inbound/outbound buffers*/
  97 /* at least NUMREGBYTES*2 are needed for register packets */
  98 #define BUFMAX 2048
  99
 100 static int initialized = 0;     /* !0 means we've been initialized */
 101
 102 static void set_mem_fault_trap();
 103
 104 static const char hexchars[]="0123456789abcdef";
 105
 106 #define NUMREGS 72
 107
 108 /* Number of bytes of registers.  */
 109 #define NUMREGBYTES (NUMREGS * 4)
 110 enum regnames {G0, G1, G2, G3, G4, G5, G6, G7,
 111                  O0, O1, O2, O3, O4, O5, SP, O7,
 112                  L0, L1, L2, L3, L4, L5, L6, L7,
 113                  I0, I1, I2, I3, I4, I5, FP, I7,
 114
 115                  F0, F1, F2, F3, F4, F5, F6, F7,
 116                  F8, F9, F10, F11, F12, F13, F14, F15,
 117                  F16, F17, F18, F19, F20, F21, F22, F23,
 118                  F24, F25, F26, F27, F28, F29, F30, F31,
 119                  Y, PSR, WIM, TBR, PC, NPC, FPSR, CPSR };
 120
 121 /***************************  ASSEMBLY CODE MACROS *************************/
 122 /*                                                                         */
 123
 124 extern void trap_low();
 125
 126 asm("
 127         .reserve trapstack, 1000 * 4, \"bss\", 8
 128
 129         .data
 130         .align  4
 131
 132 in_trap_handler:
 133         .word   0
 134
 135         .text
 136         .align 4
 137
 138 ! This function is called when any SPARC trap (except window overflow or
 139 ! underflow) occurs.  It makes sure that the invalid register window is still
 140 ! available before jumping into C code.  It will also restore the world if you
 141 ! return from handle_exception.
 142
 143         .globl _trap_low
 144 _trap_low:
 145         mov     %psr, %l0
 146         mov     %wim, %l3
 147
 148         srl     %l3, %l0, %l4           ! wim >> cwp
 149         cmp     %l4, 1
 150         bne     window_fine             ! Branch if not in the invalid window
 151         nop
 152
 153 ! Handle window overflow
 154
 155         mov     %g1, %l4                ! Save g1, we use it to hold the wim
 156         srl     %l3, 1, %g1             ! Rotate wim right
 157         tst     %g1
 158         bg      good_wim                ! Branch if new wim is non-zero
 159         nop
 160
 161 ! At this point, we need to bring a 1 into the high order bit of the wim.
 162 ! Since we don't want to make any assumptions about the number of register
 163 ! windows, we figure it out dynamically so as to setup the wim correctly.
 164
 165         not     %g1                     ! Fill g1 with ones
 166         mov     %g1, %wim               ! Fill the wim with ones
 167         nop
 168         nop
 169         nop
 170         mov     %wim, %g1               ! Read back the wim
 171         inc     %g1                     ! Now g1 has 1 just to left of wim
 172         srl     %g1, 1, %g1             ! Now put 1 at top of wim
 173         mov     %g0, %wim               ! Clear wim so that subsequent save
 174         nop                             !  won't trap
 175         nop
 176         nop
 177
 178 good_wim:
 179         save    %g0, %g0, %g0           ! Slip into next window
 180         mov     %g1, %wim               ! Install the new wim
 181
 182         std     %l0, [%sp + 0 * 4]      ! save L & I registers
 183         std     %l2, [%sp + 2 * 4]
 184         std     %l4, [%sp + 4 * 4]
 185         std     %l6, [%sp + 6 * 4]
 186
 187         std     %i0, [%sp + 8 * 4]
 188         std     %i2, [%sp + 10 * 4]
 189         std     %i4, [%sp + 12 * 4]
 190         std     %i6, [%sp + 14 * 4]
 191
 192         restore                         ! Go back to trap window.
 193         mov     %l4, %g1                ! Restore %g1
 194
 195 window_fine:
 196         sethi   %hi(in_trap_handler), %l4
 197         ld      [%lo(in_trap_handler) + %l4], %l5
 198         tst     %l5
 199         bg      recursive_trap
 200         inc     %l5
 201
 202         set     trapstack+1000*4, %sp   ! Switch to trap stack
 203
 204 recursive_trap:
 205         st      %l5, [%lo(in_trap_handler) + %l4]
 206         sub     %sp,(16+1+6+1+72)*4,%sp ! Make room for input & locals
 207                                         ! + hidden arg + arg spill
 208                                         ! + doubleword alignment
 209                                         ! + registers[72] local var
 210
 211         std     %g0, [%sp + (24 + 0) * 4] ! registers[Gx]
 212         std     %g2, [%sp + (24 + 2) * 4]
 213         std     %g4, [%sp + (24 + 4) * 4]
 214         std     %g6, [%sp + (24 + 6) * 4]
 215
 216         std     %i0, [%sp + (24 + 8) * 4] ! registers[Ox]
 217         std     %i2, [%sp + (24 + 10) * 4]
 218         std     %i4, [%sp + (24 + 12) * 4]
 219         std     %i6, [%sp + (24 + 14) * 4]
 220                                         ! F0->F31 not implemented
 221         mov     %y, %l4
 222         mov     %tbr, %l5
 223         st      %l4, [%sp + (24 + 64) * 4] ! Y
 224         st      %l0, [%sp + (24 + 65) * 4] ! PSR
 225         st      %l3, [%sp + (24 + 66) * 4] ! WIM
 226         st      %l5, [%sp + (24 + 67) * 4] ! TBR
 227         st      %l1, [%sp + (24 + 68) * 4] ! PC
 228         st      %l2, [%sp + (24 + 69) * 4] ! NPC
 229
 230                                         ! CPSR and FPSR not impl
 231
 232         or      %l0, 0xf20, %l4
 233         mov     %l4, %psr               ! Turn on traps, disable interrupts
 234
 235         call    _handle_exception
 236         add     %sp, 24 * 4, %o0        ! Pass address of registers
 237
 238 ! Reload all of the registers that aren't on the stack
 239
 240         ld      [%sp + (24 + 1) * 4], %g1 ! registers[Gx]
 241         ldd     [%sp + (24 + 2) * 4], %g2
 242         ldd     [%sp + (24 + 4) * 4], %g4
 243         ldd     [%sp + (24 + 6) * 4], %g6
 244
 245         ldd     [%sp + (24 + 8) * 4], %i0 ! registers[Ox]
 246         ldd     [%sp + (24 + 10) * 4], %i2
 247         ldd     [%sp + (24 + 12) * 4], %i4
 248         ldd     [%sp + (24 + 14) * 4], %i6
 249
 250         ldd     [%sp + (24 + 64) * 4], %l0 ! Y & PSR
 251         ldd     [%sp + (24 + 68) * 4], %l2 ! PC & NPC
 252
 253         restore                         ! Ensure that previous window is valid
 254         save    %g0, %g0, %g0           !  by causing a window_underflow trap
 255
 256         mov     %l0, %y
 257         mov     %l1, %psr               ! Make sure that traps are disabled
 258                                         ! for rett
 259
 260         sethi   %hi(in_trap_handler), %l4
 261         ld      [%lo(in_trap_handler) + %l4], %l5
 262         dec     %l5
 263         st      %l5, [%lo(in_trap_handler) + %l4]
 264
 265         jmpl    %l2, %g0                ! Restore old PC
 266         rett    %l3                     ! Restore old nPC
 267 ");
 268
 269 /* Convert ch from a hex digit to an int */
 270
 271 static int
 272 hex (unsigned char ch)
 273 {
 274   if (ch >= 'a' && ch <= 'f')
 275     return ch-'a'+10;
 276   if (ch >= '0' && ch <= '9')
 277     return ch-'0';
 278   if (ch >= 'A' && ch <= 'F')
 279     return ch-'A'+10;
 280   return -1;
 281 }
 282
 283 static char remcomInBuffer[BUFMAX];
 284 static char remcomOutBuffer[BUFMAX];
 285
 286 /* scan for the sequence $<data>#<checksum>     */
 287
 288 unsigned char *
 289 getpacket (void)
 290 {
 291   unsigned char *buffer = &remcomInBuffer[0];
 292   unsigned char checksum;
 293   unsigned char xmitcsum;
 294   int count;
 295   char ch;
 296
 297   while (1)
 298     {
 299       /* wait around for the start character, ignore all other characters */
 300       while ((ch = getDebugChar ()) != '$')
 301         ;
 302
 303 retry:
 304       checksum = 0;
 305       xmitcsum = -1;
 306       count = 0;
 307
 308       /* now, read until a # or end of buffer is found */
 309       while (count < BUFMAX)
 310         {
 311           ch = getDebugChar ();
 312           if (ch == '$')
 313             goto retry;
 314           if (ch == '#')
 315             break;
 316           checksum = checksum + ch;
 317           buffer[count] = ch;
 318           count = count + 1;
 319         }
 320       buffer[count] = 0;
 321
 322       if (ch == '#')
 323         {
 324           ch = getDebugChar ();
 325           xmitcsum = hex (ch) << 4;
 326           ch = getDebugChar ();
 327           xmitcsum += hex (ch);
 328
 329           if (checksum != xmitcsum)
 330             {
 331               putDebugChar ('-');       /* failed checksum */
 332             }
 333           else
 334             {
 335               putDebugChar ('+');       /* successful transfer */
 336
 337               /* if a sequence char is present, reply the sequence ID */
 338               if (buffer[2] == ':')
 339                 {
 340                   putDebugChar (buffer[0]);
 341                   putDebugChar (buffer[1]);
 342
 343                   return &buffer[3];
 344                 }
 345
 346               return &buffer[0];
 347             }
 348         }
 349     }
 350 }
 351
 352 /* send the packet in buffer.  */
 353
 354 static void
 355 putpacket (unsigned char *buffer)
 356 {
 357   unsigned char checksum;
 358   int count;
 359   unsigned char ch;
 360
 361   /*  $<packet info>#<checksum>. */
 362   do
 363     {
 364       putDebugChar('$');
 365       checksum = 0;
 366       count = 0;
 367
 368       while (ch = buffer[count])
 369         {
 370           putDebugChar(ch);
 371           checksum += ch;
 372           count += 1;
 373         }
 374
 375       putDebugChar('#');
 376       putDebugChar(hexchars[checksum >> 4]);
 377       putDebugChar(hexchars[checksum & 0xf]);
 378
 379     }
 380   while (getDebugChar() != '+');
 381 }
 382
 383 /* Indicate to caller of mem2hex or hex2mem that there has been an
 384    error.  */
 385 static volatile int mem_err = 0;
 386
 387 /* Convert the memory pointed to by mem into hex, placing result in buf.
 388  * Return a pointer to the last char put in buf (null), in case of mem fault,
 389  * return 0.
 390  * If MAY_FAULT is non-zero, then we will handle memory faults by returning
 391  * a 0, else treat a fault like any other fault in the stub.
 392  */
 393
 394 static unsigned char *
 395 mem2hex (unsigned char *mem, unsigned char *buf, int count, int may_fault)
 396 {
 397   unsigned char ch;
 398
 399   set_mem_fault_trap(may_fault);
 400
 401   while (count-- > 0)
 402     {
 403       ch = *mem++;
 404       if (mem_err)
 405         return 0;
 406       *buf++ = hexchars[ch >> 4];
 407       *buf++ = hexchars[ch & 0xf];
 408     }
 409
 410   *buf = 0;
 411
 412   set_mem_fault_trap(0);
 413
 414   return buf;
 415 }
 416
 417 /* convert the hex array pointed to by buf into binary to be placed in mem
 418  * return a pointer to the character AFTER the last byte written */
 419
 420 static char *
 421 hex2mem (unsigned char *buf, unsigned char *mem, int count, int may_fault)
 422 {
 423   int i;
 424   unsigned char ch;
 425
 426   set_mem_fault_trap(may_fault);
 427
 428   for (i=0; i<count; i++)
 429     {
 430       ch = hex(*buf++) << 4;
 431       ch |= hex(*buf++);
 432       *mem++ = ch;
 433       if (mem_err)
 434         return 0;
 435     }
 436
 437   set_mem_fault_trap(0);
 438
 439   return mem;
 440 }
 441
 442 /* This table contains the mapping between SPARC hardware trap types, and
 443    signals, which are primarily what GDB understands.  It also indicates
 444    which hardware traps we need to commandeer when initializing the stub. */
 445
 446 static struct hard_trap_info
 447 {
 448   unsigned char tt;             /* Trap type code for SPARClite */
 449   unsigned char signo;          /* Signal that we map this trap into */
 450 } hard_trap_info[] = {
 451   {1, SIGSEGV},                 /* instruction access error */
 452   {2, SIGILL},                  /* privileged instruction */
 453   {3, SIGILL},                  /* illegal instruction */
 454   {4, SIGEMT},                  /* fp disabled */
 455   {36, SIGEMT},                 /* cp disabled */
 456   {7, SIGBUS},                  /* mem address not aligned */
 457   {9, SIGSEGV},                 /* data access exception */
 458   {10, SIGEMT},                 /* tag overflow */
 459   {128+1, SIGTRAP},             /* ta 1 - normal breakpoint instruction */
 460   {0, 0}                        /* Must be last */
 461 };
 462
 463 /* Set up exception handlers for tracing and breakpoints */
 464
 465 void
 466 set_debug_traps (void)
 467 {
 468   struct hard_trap_info *ht;
 469
 470   for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
 471     exceptionHandler(ht->tt, trap_low);
 472
 473   initialized = 1;
 474 }
 475
 476 asm ("
 477 ! Trap handler for memory errors.  This just sets mem_err to be non-zero.  It
 478 ! assumes that %l1 is non-zero.  This should be safe, as it is doubtful that
 479 ! 0 would ever contain code that could mem fault.  This routine will skip
 480 ! past the faulting instruction after setting mem_err.
 481
 482         .text
 483         .align 4
 484
 485 _fltr_set_mem_err:
 486         sethi %hi(_mem_err), %l0
 487         st %l1, [%l0 + %lo(_mem_err)]
 488         jmpl %l2, %g0
 489         rett %l2+4
 490 ");
 491
 492 static void
 493 set_mem_fault_trap (int enable)
 494 {
 495   extern void fltr_set_mem_err();
 496   mem_err = 0;
 497
 498   if (enable)
 499     exceptionHandler(9, fltr_set_mem_err);
 500   else
 501     exceptionHandler(9, trap_low);
 502 }
 503
 504 /* Convert the SPARC hardware trap type code to a unix signal number. */
 505
 506 static int
 507 computeSignal (int tt)
 508 {
 509   struct hard_trap_info *ht;
 510
 511   for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
 512     if (ht->tt == tt)
 513       return ht->signo;
 514
 515   return SIGHUP;                /* default for things we don't know about */
 516 }
 517
 518 /*
 519  * While we find nice hex chars, build an int.
 520  * Return number of chars processed.
 521  */
 522
 523 static int
 524 hexToInt(char **ptr, int *intValue)
 525 {
 526   int numChars = 0;
 527   int hexValue;
 528
 529   *intValue = 0;
 530
 531   while (**ptr)
 532     {
 533       hexValue = hex(**ptr);
 534       if (hexValue < 0)
 535         break;
 536
 537       *intValue = (*intValue << 4) | hexValue;
 538       numChars ++;
 539
 540       (*ptr)++;
 541     }
 542
 543   return (numChars);
 544 }
 545
 546 /*
 547  * This function does all command procesing for interfacing to gdb.  It
 548  * returns 1 if you should skip the instruction at the trap address, 0
 549  * otherwise.
 550  */
 551
 552 extern void breakinst();
 553
 554 static void
 555 handle_exception (unsigned long *registers)
 556 {
 557   int tt;                       /* Trap type */
 558   int sigval;
 559   int addr;
 560   int length;
 561   char *ptr;
 562   unsigned long *sp;
 563
 564 /* First, we must force all of the windows to be spilled out */
 565
 566   asm(" save %sp, -64, %sp
 567         save %sp, -64, %sp
 568         save %sp, -64, %sp
 569         save %sp, -64, %sp
 570         save %sp, -64, %sp
 571         save %sp, -64, %sp
 572         save %sp, -64, %sp
 573         save %sp, -64, %sp
 574         restore
 575         restore
 576         restore
 577         restore
 578         restore
 579         restore
 580         restore
 581         restore
 582 ");
 583
 584   if (registers[PC] == (unsigned long)breakinst)
 585     {
 586       registers[PC] = registers[NPC];
 587       registers[NPC] += 4;
 588     }
 589
 590   sp = (unsigned long *)registers[SP];
 591
 592   tt = (registers[TBR] >> 4) & 0xff;
 593
 594   /* reply to host that an exception has occurred */
 595   sigval = computeSignal(tt);
 596   ptr = remcomOutBuffer;
 597
 598   *ptr++ = 'T';
 599   *ptr++ = hexchars[sigval >> 4];
 600   *ptr++ = hexchars[sigval & 0xf];
 601
 602   *ptr++ = hexchars[PC >> 4];
 603   *ptr++ = hexchars[PC & 0xf];
 604   *ptr++ = ':';
 605   ptr = mem2hex((char *)&registers[PC], ptr, 4, 0);
 606   *ptr++ = ';';
 607
 608   *ptr++ = hexchars[FP >> 4];
 609   *ptr++ = hexchars[FP & 0xf];
 610   *ptr++ = ':';
 611   ptr = mem2hex(sp + 8 + 6, ptr, 4, 0); /* FP */
 612   *ptr++ = ';';
 613
 614   *ptr++ = hexchars[SP >> 4];
 615   *ptr++ = hexchars[SP & 0xf];
 616   *ptr++ = ':';
 617   ptr = mem2hex((char *)&sp, ptr, 4, 0);
 618   *ptr++ = ';';
 619
 620   *ptr++ = hexchars[NPC >> 4];
 621   *ptr++ = hexchars[NPC & 0xf];
 622   *ptr++ = ':';
 623   ptr = mem2hex((char *)&registers[NPC], ptr, 4, 0);
 624   *ptr++ = ';';
 625
 626   *ptr++ = hexchars[O7 >> 4];
 627   *ptr++ = hexchars[O7 & 0xf];
 628   *ptr++ = ':';
 629   ptr = mem2hex((char *)&registers[O7], ptr, 4, 0);
 630   *ptr++ = ';';
 631
 632   *ptr++ = 0;
 633
 634   putpacket(remcomOutBuffer);
 635
 636   while (1)
 637     {
 638       remcomOutBuffer[0] = 0;
 639
 640       ptr = getpacket();
 641       switch (*ptr++)
 642         {
 643         case '?':
 644           remcomOutBuffer[0] = 'S';
 645           remcomOutBuffer[1] = hexchars[sigval >> 4];
 646           remcomOutBuffer[2] = hexchars[sigval & 0xf];
 647           remcomOutBuffer[3] = 0;
 648           break;
 649
 650         case 'd':               /* toggle debug flag */
 651           break;
 652
 653         case 'g':               /* return the value of the CPU registers */
 654           {
 655             ptr = remcomOutBuffer;
 656             ptr = mem2hex((char *)registers, ptr, 16 * 4, 0); /* G & O regs */
 657             ptr = mem2hex(sp + 0, ptr, 16 * 4, 0); /* L & I regs */
 658             memset(ptr, '0', 32 * 8); /* Floating point */
 659             mem2hex((char *)&registers[Y],
 660                     ptr + 32 * 4 * 2,
 661                     8 * 4,
 662                     0);         /* Y, PSR, WIM, TBR, PC, NPC, FPSR, CPSR */
 663           }
 664           break;
 665
 666         case 'G':          /* set the value of the CPU registers - return OK */
 667           {
 668             unsigned long *newsp, psr;
 669
 670             psr = registers[PSR];
 671
 672             hex2mem(ptr, (char *)registers, 16 * 4, 0); /* G & O regs */
 673             hex2mem(ptr + 16 * 4 * 2, sp + 0, 16 * 4, 0); /* L & I regs */
 674             hex2mem(ptr + 64 * 4 * 2, (char *)&registers[Y],
 675                     8 * 4, 0);  /* Y, PSR, WIM, TBR, PC, NPC, FPSR, CPSR */
 676
 677             /* See if the stack pointer has moved.  If so, then copy the saved
 678                locals and ins to the new location.  This keeps the window
 679                overflow and underflow routines happy.  */
 680
 681             newsp = (unsigned long *)registers[SP];
 682             if (sp != newsp)
 683               sp = memcpy(newsp, sp, 16 * 4);
 684
 685             /* Don't allow CWP to be modified. */
 686
 687             if (psr != registers[PSR])
 688               registers[PSR] = (psr & 0x1f) | (registers[PSR] & ~0x1f);
 689
 690             strcpy(remcomOutBuffer,"OK");
 691           }
 692           break;
 693
 694         case 'm':         /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
 695           /* Try to read %x,%x.  */
 696
 697           if (hexToInt(&ptr, &addr)
 698               && *ptr++ == ','
 699               && hexToInt(&ptr, &length))
 700             {
 701               if (mem2hex((char *)addr, remcomOutBuffer, length, 1))
 702                 break;
 703
 704               strcpy (remcomOutBuffer, "E03");
 705             }
 706           else
 707             strcpy(remcomOutBuffer,"E01");
 708           break;
 709
 710         case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK */
 711           /* Try to read '%x,%x:'.  */
 712
 713           if (hexToInt(&ptr, &addr)
 714               && *ptr++ == ','
 715               && hexToInt(&ptr, &length)
 716               && *ptr++ == ':')
 717             {
 718               if (hex2mem(ptr, (char *)addr, length, 1))
 719                 strcpy(remcomOutBuffer, "OK");
 720               else
 721                 strcpy(remcomOutBuffer, "E03");
 722             }
 723           else
 724             strcpy(remcomOutBuffer, "E02");
 725           break;
 726
 727         case 'c':    /* cAA..AA    Continue at address AA..AA(optional) */
 728           /* try to read optional parameter, pc unchanged if no parm */
 729
 730           if (hexToInt(&ptr, &addr))
 731             {
 732               registers[PC] = addr;
 733               registers[NPC] = addr + 4;
 734             }
 735
 736 /* Need to flush the instruction cache here, as we may have deposited a
 737    breakpoint, and the icache probably has no way of knowing that a data ref to
 738    some location may have changed something that is in the instruction cache.
 739  */
 740
 741           flush_i_cache();
 742           return;
 743
 744           /* kill the program */
 745         case 'k' :              /* do nothing */
 746           break;
 747 #if 0
 748         case 't':               /* Test feature */
 749           asm (" std %f30,[%sp]");
 750           break;
 751 #endif
 752         case 'r':               /* Reset */
 753           asm ("call 0
 754                 nop ");
 755           break;
 756         }                       /* switch */
 757
 758       /* reply to the request */
 759       putpacket(remcomOutBuffer);
 760     }
 761 }
 762
 763 /* This function will generate a breakpoint exception.  It is used at the
 764    beginning of a program to sync up with a debugger and can be used
 765    otherwise as a quick means to stop program execution and "break" into
 766    the debugger. */
 767
 768 void
 769 breakpoint (void)
 770 {
 771   if (!initialized)
 772     return;
 773
 774   asm(" .globl _breakinst
 775
 776         _breakinst: ta 1
 777       ");
 778 }