i386-stub.c

早期freebsd实现

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

  do {
    /* wait around for the start character, ignore all other characters */
    while ((ch = getDebugChar()) != '$');
    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;
      }
    buffer[count] = 0;

    if (ch == '#') {
      xmitcsum = hex(getDebugChar()) << 4;
      xmitcsum += hex(getDebugChar());
      if ((remote_debug ) && (checksum != xmitcsum)) {
        fprintf(stderr,"bad checksum.  My count = 0x%x, sent=0x%x. buf=%s\n",
						     checksum,xmitcsum,buffer);
      }

      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.  */


void putpacket(buffer)
char * buffer;
{
  unsigned char checksum;
  int  count;
  char ch;

  /*  $<packet info>#<checksum>. */
  do {
  putDebugChar('$');
  checksum = 0;
  count    = 0;

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

  putDebugChar('#');
  putDebugChar(hexchars[checksum >> 4]);
  putDebugChar(hexchars[checksum % 16]);

  } while (getDebugChar() != '+');

}

char  remcomInBuffer[BUFMAX];
char  remcomOutBuffer[BUFMAX];
static short error;


void debug_error(format, parm)
char * format;
char * parm;
{
  if (remote_debug) fprintf(stderr,format,parm);
}

/* Address of a routine to RTE to if we get a memory fault.  */
static NORETURN void (*mem_fault_routine)() = NULL;

/* Indicate to caller of mem2hex or hex2mem that there has been an
   error.  */
static volatile int mem_err = 0;

void
set_mem_err ()
{
  mem_err = 1;
}

/* These are separate functions so that they are so short and sweet
   that the compiler won't save any registers (if there is a fault
   to mem_fault, they won't get restored, so there better not be any
   saved).  */
int
get_char (addr)
     char *addr;
{
  return *addr;
}

void
set_char (addr, val)
     char *addr;
     int val;
{
  *addr = val;
}

/* convert the memory pointed to by mem into hex, placing result in buf */
/* return a pointer to the last char put in buf (null) */
/* If MAY_FAULT is non-zero, then we should set mem_err in response to
   a fault; if zero treat a fault like any other fault in the stub.  */
char* mem2hex(mem, buf, count, may_fault)
char* mem;
char* buf;
int   count;
int may_fault;
{
      int i;
      unsigned char ch;

      if (may_fault)
	  mem_fault_routine = set_mem_err;
      for (i=0;i<count;i++) {
          ch = get_char (mem++);
	  if (may_fault && mem_err)
	    return (buf);
          *buf++ = hexchars[ch >> 4];
          *buf++ = hexchars[ch % 16];
      }
      *buf = 0;
      if (may_fault)
	  mem_fault_routine = NULL;
      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 */
char* hex2mem(buf, mem, count, may_fault)
char* buf;
char* mem;
int   count;
int may_fault;
{
      int i;
      unsigned char ch;

      if (may_fault)
	  mem_fault_routine = set_mem_err;
      for (i=0;i<count;i++) {
          ch = hex(*buf++) << 4;
          ch = ch + hex(*buf++);
          set_char (mem++, ch);
	  if (may_fault && mem_err)
	    return (mem);
      }
      if (may_fault)
	  mem_fault_routine = NULL;
      return(mem);
}

/* this function takes the 386 exception vector and attempts to
   translate this number into a unix compatible signal value */
int computeSignal( exceptionVector )
int exceptionVector;
{
  int sigval;
  switch (exceptionVector) {
    case 0 : sigval = 8; break; /* divide by zero */
    case 1 : sigval = 5; break; /* debug exception */
    case 3 : sigval = 5; break; /* breakpoint */
    case 4 : sigval = 16; break; /* into instruction (overflow) */
    case 5 : sigval = 16; break; /* bound instruction */
    case 6 : sigval = 4; break; /* Invalid opcode */
    case 7 : sigval = 8; break; /* coprocessor not available */
    case 8 : sigval = 7; break; /* double fault */
    case 9 : sigval = 11; break; /* coprocessor segment overrun */
    case 10 : sigval = 11; break; /* Invalid TSS */
    case 11 : sigval = 11; break; /* Segment not present */
    case 12 : sigval = 11; break; /* stack exception */
    case 13 : sigval = 11; break; /* general protection */
    case 14 : sigval = 11; break; /* page fault */
    case 16 : sigval = 7; break; /* coprocessor error */
    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;

  gdb_i386vector = exceptionVector;

  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 */
                 break;
      case 'g' : /* return the value of the CPU registers */
                mem2hex((char*) registers, remcomOutBuffer, NUMREGBYTES, 0);
                break;
      case 'G' : /* set the value of the CPU registers - return OK */
                hex2mem(&remcomInBuffer[1], (char*) registers, NUMREGBYTES, 0);
                strcpy(remcomOutBuffer,"OK");
                break;

      /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
      case 'm' :
		    /* 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;
				mem_err = 0;
                                mem2hex((char*) addr, remcomOutBuffer, length, 1);
				if (mem_err) {
				    strcpy (remcomOutBuffer, "E03");
				    debug_error ("memory fault");
				}
                            }

                    if (ptr)
                    {
		      strcpy(remcomOutBuffer,"E01");
		      debug_error("malformed read memory command: %s",remcomInBuffer);
		    }
	          break;

      /* MAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK */
      case 'M' :
		    /* 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++) == ':')
                                {
				    mem_err = 0;
                                    hex2mem(ptr, (char*) addr, length, 1);

				    if (mem_err) {
					strcpy (remcomOutBuffer, "E03");
					debug_error ("memory fault");
				    } else {
				        strcpy(remcomOutBuffer,"OK");
				    }

                                    ptr = 0;
                                }
                    if (ptr)
                    {
		      strcpy(remcomOutBuffer,"E02");
		      debug_error("malformed write memory command: %s",remcomInBuffer);
		    }
                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 ] &= 0xfffffeff;

          /* set the trace bit if we're stepping */
          if (remcomInBuffer[0] == 's') registers[ PS ] |= 0x100;

          /*
           * 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 0
	  /* Don't really think we need this, except maybe for protection
	     exceptions.  */
                  /*
                   * invoke the previous handler.
                   */
                  if (oldExceptionHook)
                      (*oldExceptionHook) (frame->exceptionVector);
                  newPC = registers[ PC ];    /* pc may have changed  */
#endif /* 0 */

	  _returnFromException(); /* this is a jump */

          break;

      /* kill the program */
      case 'k' :  /* do nothing */
		BREAKPOINT();
                break;
      } /* switch */

    /* reply to the request */
    putpacket(remcomOutBuffer);
    }
}

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

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

  exceptionHandler (0, _catchException0);
  exceptionHandler (1, _catchException1);
  exceptionHandler (3, _catchException3);
  exceptionHandler (4, _catchException4);
  exceptionHandler (5, _catchException5);
  exceptionHandler (6, _catchException6);
  exceptionHandler (7, _catchException7);
  exceptionHandler (8, _catchException8);
  exceptionHandler (9, _catchException9);
  exceptionHandler (10, _catchException10);
  exceptionHandler (11, _catchException11);
  exceptionHandler (12, _catchException12);
  exceptionHandler (13, _catchException13);
  exceptionHandler (14, _catchException14);
  exceptionHandler (16, _catchException16);

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

  /* In case GDB is started before us, ack any packets (presumably
     "$?#xx") sitting there.  */
  putDebugChar ('+');

  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)
#if 0
    handle_exception(3);
#else
    BREAKPOINT();
#endif
  waitabit();
}

int waitlimit = 1000000;

#if 0
void
bogon()
{
  waitabit();
}
#endif

void
waitabit()
{
  int i;
  for (i = 0; i < waitlimit; i++) ;
}