m68k-stub.c

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

      *optr++ = 'd';
      *optr++ = ':';
      optr   = thread2vhstr(optr, thread);
      *optr++ = ';';
   }
#endif
   *optr++ = '\0';
}

/*
 * This function does all command procesing for interfacing to gdb.
 */
void handle_exception(int exceptionVector)
{
  int    host_has_detached = 0;
  int    addr, length;
  char * ptr;
  int    newPC;
  Frame  *frame;
  int          current_thread;  /* current generic thread */
  int          thread;          /* stopped thread: context exception happened in */
   void         *regptr;
   int binary;

  if (remote_debug) printf("vector=%d, sr=0x%x, pc=0x%x\n", 
			    exceptionVector,
			    registers[ PS ], 
			    registers[ PC ]);

   thread = 0;
#if defined(GDB_STUB_ENABLE_THREAD_SUPPORT)
   if (do_threads) {
      thread = rtems_gdb_stub_get_current_thread();
   }
#endif
   current_thread = thread;
  
#if 0
  /* reply to host that an exception has occurred */
  sigval = computeSignal( exceptionVector );
  remcomOutBuffer[0] = 'S';
  remcomOutBuffer[1] =  gdb_hexchars[sigval >> 4];
  remcomOutBuffer[2] =  gdb_hexchars[sigval % 16];
  remcomOutBuffer[3] = 0;
#else
   /* reply to host that an exception has occurred with some basic info */
   gdb_stub_report_exception_info(exceptionVector, registers, thread);
#endif

  putpacket(remcomOutBuffer); 

  while (!(host_has_detached)) { 
    binary = 0;
    error = 0;
    remcomOutBuffer[0] = 0;
    getpacket(remcomInBuffer);
    switch (remcomInBuffer[0]) {
#if 0
      case '?' :   remcomOutBuffer[0] = 'S';
                   remcomOutBuffer[1] =  gdb_hexchars[sigval >> 4];
                   remcomOutBuffer[2] =  gdb_hexchars[sigval % 16];
                   remcomOutBuffer[3] = 0;
                 break; 
#else
      case '?' : gdb_stub_report_exception_info(exceptionVector,
						registers,
						thread);
	         break;
#endif
      case 'd' : remote_debug = !(remote_debug);  /* toggle debug flag */
                 break; 
      case 'D' : /* host has detached */
	         strcpy(remcomOutBuffer,"OK");
	         host_has_detached = 1;
                 break; 
         case 'g':               /* return the values of the CPU registers */
            regptr = registers;
#if defined(GDB_STUB_ENABLE_THREAD_SUPPORT)
            if (do_threads && current_thread != thread )
               regptr = &current_thread_registers;
#endif
            mem2hex (regptr, remcomOutBuffer, sizeof registers);
            break;


         case 'G':       /* set the values of the CPU registers - return OK */
	   regptr = registers;
#if defined(GDB_STUB_ENABLE_THREAD_SUPPORT)
	   if (do_threads && current_thread != thread )
	     regptr = &current_thread_registers;
#endif
	   if (hex2mem (&remcomInBuffer[1], 
			regptr, 
			sizeof registers)) {
	     strcpy (remcomOutBuffer, "OK");
	   }
	   else {
	     strcpy (remcomOutBuffer, "E00"); /* E00 = bad "set register" command */
	   }
	   break;
      
      /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
      case 'm' : 
	        if (setjmp(remcomEnv) == 0)
                {
                    m68k_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");
		      debug_error("malformed read memory command: %s",remcomInBuffer);
                  }     
                } 
		else {
		  m68k_exceptionHandler(2,_catchException);   
		  strcpy(remcomOutBuffer,"E03");
		  debug_error("bus error", 0);
		  }     
                
		/* restore handler for bus error */
		m68k_exceptionHandler(2,_catchException);   
		break;
      
      /* XAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK */
      /* Transfer is in binary, '$', '#' and 0x7d is escaped with 0x7d */
      case 'X' : 
                binary = 1;
      /* MAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK */
      case 'M' : 
	        if (setjmp(remcomEnv) == 0) {
		    m68k_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++) == ':')
                                {
				  if (binary) {
				    bin2mem(ptr,(char *)addr,length);
				  }
				  else {
                                    hex2mem(ptr, (char*) addr, length);
				  }
				  ptr = 0;
				  strcpy(remcomOutBuffer,"OK");
                                }
                    if (ptr)
                    {
		      strcpy(remcomOutBuffer,"E02");
		      debug_error("malformed write memory command: %s",remcomInBuffer);
		      }     
                } 
		else {
		  m68k_exceptionHandler(2,_catchException);   
		  strcpy(remcomOutBuffer,"E03");
		  debug_error("bus error", 0);
		  }     

                /* restore handler for bus error */
                m68k_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) printf("new pc = 0x%x\n",newPC);
          frame = lastFrame;
          while (frame)
          {
              if (remote_debug)
                  printf("frame at 0x%x has pc=0x%x, except#=%d\n",
                         (unsigned32) frame,
			 (unsigned32) frame->exceptionPC,
                         (unsigned32) 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+2))) 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)
                          printf("frame at 0x%x has pc=0x%x, except#=%d\n",
                                 (unsigned32) frame,
				 frame->exceptionPC,
                                 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;
          
         case 'q':   /* queries */
#if defined(GDB_STUB_ENABLE_THREAD_SUPPORT)
            rtems_gdb_process_query( remcomInBuffer, 
				     remcomOutBuffer, 
				     do_threads, 
				     thread );
#endif
            break;

#if defined(GDB_STUB_ENABLE_THREAD_SUPPORT)
         case 'T':
         {
            int testThread;

            if( vhstr2thread(&remcomInBuffer[1], &testThread) == NULL ) 
            {
               strcpy(remcomOutBuffer, "E01");
               break;
            }

            if( rtems_gdb_index_to_stub_id(testThread) == NULL )
            {
               strcpy(remcomOutBuffer, "E02");
            }
            else
            {
               strcpy(remcomOutBuffer, "OK");
            }
         }
         break;
#endif
        
         case 'H':  /* set new thread */
#if defined(GDB_STUB_ENABLE_THREAD_SUPPORT)
            if (remcomInBuffer[1] != 'g') {
               break;
            }
	  
            if (!do_threads) {
               break;
            }
	  
            {
               int tmp, ret;
	    
               /* Set new generic thread */
               if (vhstr2thread(&remcomInBuffer[2], &tmp) == NULL) {
                  strcpy(remcomOutBuffer, "E01");
                  break;
               }

               /* 0 means `thread' */
               if (tmp == 0) {
                  tmp = thread;
               }

               if (tmp == current_thread) {
                  /* No changes */
                  strcpy(remcomOutBuffer, "OK");
                  break;
               }

               /* Save current thread registers if necessary */ 
               if (current_thread != thread) {
                  ret = rtems_gdb_stub_set_thread_regs(
                     current_thread, (unsigned int *) &current_thread_registers);
               }

               /* Read new registers if necessary */
               if (tmp != thread) {
                  ret = rtems_gdb_stub_get_thread_regs(
                     tmp, (unsigned int *) &current_thread_registers);

                  if (!ret) {
                     /* Thread does not exist */
                     strcpy(remcomOutBuffer, "E02");
                     break;
                  }
               }
	    
               current_thread = tmp;
               strcpy(remcomOutBuffer, "OK");
            }
#endif
            break;

      /* kill the program */
      case 'k' :  /* do nothing */
                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();
  extern void remcomHandler();
  int exception;

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

  for (exception = 2; exception <= 23; exception++)
      m68k_exceptionHandler(exception,_catchException);   

  /* level 7 interrupt              */
  m68k_exceptionHandler(31,_debug_level7);    
  
  /* GDB breakpoint exception (trap #1) */
  m68k_exceptionHandler(33,_catchException);

  /* coded breakpoint exception (trap #2) */
  m68k_exceptionHandler(34,_catchException);
  
  /* 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?  */
  m68k_exceptionHandler(40,_catchException);
  
  /* 48 to 54 are floating point coprocessor errors */
  for (exception = 48; exception <= 54; exception++)
      m68k_exceptionHandler(exception,_catchException);   

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

}

/* 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();
}