m68k-stub.c

RTEMS (Real-Time Executive for Multiprocessor Systems) is a free open source real-time operating sys

    case 5 : sigval = 8;  break; /* zero divide         */
    case 6 : sigval = 8; break; /* chk instruction     */
    case 7 : sigval = 8; break; /* trapv instruction   */
    case 8 : sigval = 11; break; /* privilege violation */
    case 9 : sigval = 5;  break; /* trace trap          */
    case 10: sigval = 4;  break; /* line 1010 emulator  */
    case 11: sigval = 4;  break; /* line 1111 emulator  */

      /* Coprocessor protocol violation.  Using a standard MMU or FPU
         this cannot be triggered by software.  Call it a SIGBUS.  */
    case 13: sigval = 10;  break;

    case 31: sigval = 2;  break; /* interrupt           */
    case 33: sigval = 5;  break; /* breakpoint          */

      /* This is a trap #8 instruction.  Apparently it is someone's software
         convention for some sort of SIGFPE condition.  Whose?  How many
         people are being screwed by having this code the way it is?
         Is there a clean solution?  */
    case 40: sigval = 8;  break; /* floating point err  */

    case 48: sigval = 8;  break; /* floating point err  */
    case 49: sigval = 8;  break; /* floating point err  */
    case 50: sigval = 8;  break; /* zero divide         */
    case 51: sigval = 8;  break; /* underflow           */
    case 52: sigval = 8;  break; /* operand error       */
    case 53: sigval = 8;  break; /* overflow            */
    case 54: sigval = 8;  break; /* NAN                 */
    default: 
      sigval = 7;         /* "software generated"*/
  }
  return (sigval);
}

/**********************************************/
/* WHILE WE FIND NICE HEX CHARS, BUILD AN INT */
/* RETURN NUMBER OF CHARS PROCESSED           */
/**********************************************/
int hexToInt(char **ptr, int *intValue)
{
  int numChars = 0;
  int hexValue;
    
  *intValue = 0;

  while (**ptr)
  {
    hexValue = hex(**ptr);
    if (hexValue >=0)
    {
      *intValue = (*intValue <<4) | hexValue;
      numChars ++;
    }
    else
      break;
        
    (*ptr)++;
  }

  return (numChars);
}

/*
 * This function does all command procesing for interfacing to gdb.
 */
void handle_exception(int exceptionVector)
{
  int    sigval;
  int    addr, length;
  char * ptr;
  int    newPC;
  Frame  *frame;
  
  if (remote_debug)
    printf("vector=%d, sr=0x%x, pc=0x%x\n", 
           exceptionVector,
           registers[ PS ], 
           registers[ PC ]);

  /* reply to host that an exception has occurred */
  sigval = computeSignal( exceptionVector );
  remcomOutBuffer[0] = 'S';
  remcomOutBuffer[1] =  hexchars[sigval >> 4];
  remcomOutBuffer[2] =  hexchars[sigval % 16];
  remcomOutBuffer[3] = 0;

  putpacket(remcomOutBuffer); 

  while (1==1) { 
    error = 0;
    remcomOutBuffer[0] = 0;
    getpacket(remcomInBuffer);
    switch (remcomInBuffer[0]) {
      case '?' :   remcomOutBuffer[0] = 'S';
        remcomOutBuffer[1] =  hexchars[sigval >> 4];
        remcomOutBuffer[2] =  hexchars[sigval % 16];
        remcomOutBuffer[3] = 0;
        break; 
      case 'd' :
        remote_debug = !(remote_debug);  /* toggle debug flag */
        debug_port_printf("debug mode ");
        if (remote_debug)
        {          
          debug_port_printf("on\n");
        }
        else
        {          
          debug_port_printf("off\n");
        }    
        break; 
      case 'g' : /* return the value of the CPU registers */
        mem2hex((char*) registers, remcomOutBuffer, NUMREGBYTES);
        break;
      case 'G' : /* set the value of the CPU registers - return OK */
        hex2mem(&remcomInBuffer[1], (char*) registers, NUMREGBYTES);
        strcpy(remcomOutBuffer,"OK");
        break;
      
        /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
      case 'm' : 
        if (setjmp(remcomEnv) == 0)
        {
          exceptionHandler(2,handle_buserror); 

          /* TRY TO READ %x,%x.  IF SUCCEED, SET PTR = 0 */
          ptr = &remcomInBuffer[1];
          if (hexToInt(&ptr,&addr))
            if (*(ptr++) == ',')
              if (hexToInt(&ptr,&length)) 
              {
                ptr = 0;
                mem2hex((char*) addr, remcomOutBuffer, length);
              }

          if (ptr)
          {
            strcpy(remcomOutBuffer,"E01");
            if (remote_debug)
              printf("malformed read memory command: %s",remcomInBuffer);
          }     
        } 
        else {
          exceptionHandler(2,_catchException);   
          strcpy(remcomOutBuffer,"E03");
          if (remote_debug)
            printf("bus error");
        }     
                
        /* restore handler for bus error */
        exceptionHandler(2,_catchException);   
        break;
      
        /* MAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK */
      case 'M' : 
        if (setjmp(remcomEnv) == 0) {
          exceptionHandler(2,handle_buserror); 
                    
          /* TRY TO READ '%x,%x:'.  IF SUCCEED, SET PTR = 0 */
          ptr = &remcomInBuffer[1];
          if (hexToInt(&ptr,&addr))
            if (*(ptr++) == ',')
              if (hexToInt(&ptr,&length))
                if (*(ptr++) == ':')
                {
                  hex2mem(ptr, (char*) addr, length);
                  ptr = 0;
                  strcpy(remcomOutBuffer,"OK");
                }
          if (ptr)
          {
            strcpy(remcomOutBuffer,"E02");
            if (remote_debug)
              printf("malformed write memory command: %s",remcomInBuffer);
		      }     
        } 
        else {
          exceptionHandler(2,_catchException);   
          strcpy(remcomOutBuffer,"E03");
          if (remote_debug)
            printf("bus error");
        }     

        /* restore handler for bus error */
        exceptionHandler(2,_catchException);   
        break;
     
        /* cAA..AA    Continue at address AA..AA(optional) */
        /* sAA..AA   Step one instruction from AA..AA(optional) */
      case 'c' : 
      case 's' : 
        /* try to read optional parameter, pc unchanged if no parm */
        ptr = &remcomInBuffer[1];
        if (hexToInt(&ptr,&addr))
          registers[ PC ] = addr;
             
        newPC = registers[ PC];
          
        /* clear the trace bit */
        registers[ PS ] &= 0x7fff;
          
        /* set the trace bit if we're stepping */
        if (remcomInBuffer[0] == 's') registers[ PS ] |= 0x8000;
          
        /*
         * look for newPC in the linked list of exception frames.
         * if it is found, use the old frame it.  otherwise,
         * fake up a dummy frame in returnFromException().
         */
        if (remote_debug) debug_port_printf("new pc = 0x%x\n",newPC);
        
        frame = lastFrame;
        while (frame)
        {
          if (remote_debug)
            debug_port_printf("frame at 0x%x has pc=0x%x, except#=%d\n",
                              frame,frame->exceptionPC,
                              (unsigned int) frame->exceptionVector);
          if (frame->exceptionPC == newPC) break;  /* bingo! a match */
          /*
           * for a breakpoint instruction, the saved pc may
           * be off by two due to re-executing the instruction
           * replaced by the trap instruction.  Check for this.
           */
          if ((frame->exceptionVector == 33) &&
              (frame->exceptionPC == newPC)) break;
          if (frame == frame->previous)
          {
	          frame = 0; /* no match found */ 
	          break; 
          }
          frame = frame->previous;
        }
          
        /*
         * If we found a match for the PC AND we are not returning
         * as a result of a breakpoint (33),
         * trace exception (9), nmi (31), jmp to
         * the old exception handler as if this code never ran.
         */
        if (frame) 
        {
          if ((frame->exceptionVector != 9)  && 
              (frame->exceptionVector != 31) && 
              (frame->exceptionVector != 33))
          { 
            /*
             * invoke the previous handler.
             */
            if (oldExceptionHook)
              (*oldExceptionHook) (frame->exceptionVector);
            newPC = registers[ PC ];    /* pc may have changed  */
            if (newPC != frame->exceptionPC)
            {
              if (remote_debug)
                debug_port_printf("frame at 0x%x has pc=0x%x, except#=%d\n",
                                  frame,frame->exceptionPC,
                                  (unsigned int) frame->exceptionVector);
              /* re-use the last frame, we're skipping it (longjump?)*/
              frame = (Frame *) 0;
              _returnFromException( frame );  /* this is a jump */
            }
          }
        }         

    	  /* if we couldn't find a frame, create one */
        if (frame == 0)
        {
          frame = lastFrame -1 ;
	      
          /* by using a bunch of print commands with breakpoints,
             it's possible for the frame stack to creep down.  If it creeps
             too far, give up and reset it to the top.  Normal use should
             not see this happen.
             */
          if ((unsigned int) (frame-2) < (unsigned int) &gdbFrameStack)
          {
            initializeRemcomErrorFrame();
            frame = lastFrame; 
          }
          frame->previous = lastFrame;
          lastFrame = frame;
          frame = 0;  /* null so _return... will properly initialize it */ 
        }    
	  
        _returnFromException( frame ); /* this is a jump */

        break;
          
        /* kill the program */
      case 'k' :
        /* reset the board */
        WATCHDOG_TRIGGER();
        while (1 == 1);
        break;
        
    } /* switch */ 
    
    /* reply to the request */
    putpacket(remcomOutBuffer); 
  }
}


void initializeRemcomErrorFrame()
{
    lastFrame = ((Frame *) &gdbFrameStack[FRAMESIZE-1]) - 1;
    lastFrame->previous = lastFrame;
}

/* this function is used to set up exception handlers for tracing and 
   breakpoints */
void set_debug_traps()
{
  extern void _debug_level7(void);
  extern void remcomHandler(void);
  
  int exception;

  initializeRemcomErrorFrame();
  stackPtr  = &remcomStack[STACKSIZE/sizeof(int) - 1];

  registers[ PC ] = 0x400;
  registers[ PS ] = 0x2700;
  
  for (exception = 2; exception <= 30; exception++)
      exceptionHandler(exception,_catchException);   

  /* level 7 interrupt              */
  exceptionHandler(31,_debug_level7);    
  
  for (exception = 32; exception <= 47; exception++)
    exceptionHandler(exception,_catchException);   

  /* exclude the unassigned, reserved vector locations */
  
  for (exception = 64; exception <= 255; exception++)
    exceptionHandler(exception,_catchException);   

  if (oldExceptionHook != (ExceptionHook) remcomHandler)
  {
      oldExceptionHook = exceptionHook;
      exceptionHook    = (ExceptionHook) remcomHandler;
  }
  
  initialized = 1;

#if defined(UPDATE_DISPLAY)  
  UPDATE_DISPLAY("gdb ");
#endif  
}

/* 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()
{
  if (initialized) BREAKPOINT();
}