m68k-stub.c

早期freebsd实现

	movel   a0,a1           /* copy save pointer            */
	subql   #1,d0           /* predecrement loop counter    */
#
# copy the frame
saveFrameLoop:
	movew  	sp@+,a1@+
	dbf     d0,saveFrameLoop
#
# now that the stack has been clenaed,
# save the a7 in use at time of exception
        movel   sp,_superStack  /* save supervisor sp           */
        andiw   #0x2000,d1      /* were we in supervisor mode ? */
        beq     userMode       
        movel   a7,a5@(60)      /* save a7                  */
        bra     a7saveDone
userMode:  
	movel   usp,a1    	
        movel   a1,a5@(60)      /* save user stack pointer	*/
a7saveDone:

#
# save size of frame
        movew   d3,a0@-

#
# compute exception number
	andl    #0xfff,d2   	/* mask off vector offset	*/
	lsrw    #2,d2   	/* divide by 4 to get vect num	*/
        movel   d2,a0@-         /* save it                      */
#
# save pc causing exception
        movel   a4,a0@-
#
# save old frame link and set the new value
	movel	_lastFrame,a1	/* last frame pointer */
	movel   a1,a0@-		/* save pointer to prev frame	*/
        movel   a0,_lastFrame

        movel   d2,sp@-		/* push exception num           */
	movel   _exceptionHook,a0  /* get address of handler */
        jbsr    a0@             /* and call it */
        clrl    sp@             /* replace exception num parm with frame ptr */
        jbsr     __returnFromException   /* jbsr, but never returns */
");
#else /* mc68000 */
/* This function is called when an exception occurs.  It translates the
 * return address found on the stack into an exception vector # which
 * is then handled by either handle_exception or a system handler.
 * _catchException provides a front end for both.  
 *
 * stack on entry:                       stack on exit:
 *   Program counter MSWord              exception # MSWord 
 *   Program counter LSWord              exception # MSWord
 *   Status Register                     
 *   Return Address  MSWord              
 *   Return Address  LSWord             
 */
asm("
.text
.globl __catchException
__catchException:");
DISABLE_INTERRUPTS();
asm("
        moveml d0-d7/a0-a6,_registers  /* save registers               */
	movel	_lastFrame,a0	/* last frame pointer */
");
SAVE_FP_REGS();        
asm("
        lea     _registers,a5   /* get address of registers     */
        movel   sp@+,d2         /* pop return address           */
	addl 	#1530,d2        /* convert return addr to 	*/
	divs 	#6,d2   	/*  exception number		*/
	extl    d2   

        moveql  #3,d3           /* assume a three word frame     */

        cmpiw   #3,d2           /* bus error or address error ? */
        bgt     normal          /* if >3 then normal error      */
        movel   sp@+,a0@-       /* copy error info to frame buff*/
        movel   sp@+,a0@-       /* these are never used         */
        moveql  #7,d3           /* this is a 7 word frame       */
     
normal:   
	movew   sp@+,d1         /* pop status register          */
        movel   sp@+,a4         /* pop program counter          */
        movew   d1,a5@(66)      /* save sr		 	*/	
        movel   a4,a5@(68)      /* save pc in _regisers[]      	*/
        movel   a4,a0@-         /* copy pc to frame buffer      */
	movew   d1,a0@-         /* copy sr to frame buffer      */

        movel   sp,_superStack  /* save supervisor sp          */

        andiw   #0x2000,d1      /* were we in supervisor mode ? */
        beq     userMode       
        movel   a7,a5@(60)      /* save a7                  */
        bra     saveDone             
userMode:
        movel   usp,a1    	/* save user stack pointer 	*/
        movel   a1,a5@(60)      /* save user stack pointer	*/
saveDone:

        movew   d3,a0@-         /* push frame size in words     */
        movel   d2,a0@-         /* push vector number           */
        movel   a4,a0@-         /* push exception pc            */

#
# save old frame link and set the new value
	movel	_lastFrame,a1	/* last frame pointer */
	movel   a1,a0@-		/* save pointer to prev frame	*/
        movel   a0,_lastFrame

        movel   d2,sp@-		/* push exception num           */
	movel   _exceptionHook,a0  /* get address of handler */
        jbsr    a0@             /* and call it */
        clrl    sp@             /* replace exception num parm with frame ptr */
        jbsr     __returnFromException   /* jbsr, but never returns */
");
#endif


/*
 * remcomHandler is a front end for handle_exception.  It moves the
 * stack pointer into an area reserved for debugger use in case the
 * breakpoint happened in supervisor mode.
 */
asm("_remcomHandler:");
asm("           addl    #4,sp");        /* pop off return address     */
asm("           movel   sp@+,d0");      /* get the exception number   */
asm("		movel   _stackPtr,sp"); /* move to remcom stack area  */
asm("		movel   d0,sp@-");	/* push exception onto stack  */
asm("		jbsr    _handle_exception");    /* this never returns */
asm("           rts");                  /* return */

void _returnFromException( Frame *frame )
{
    /* if no passed in frame, use the last one */
    if (! frame)
    {
        frame = lastFrame;
	frame->frameSize = 4;
        frame->format = 0;
        frame->fsaveHeader = -1; /* restore regs, but we dont have fsave info*/
    }

#ifndef mc68020
    /* a 68000 cannot use the internal info pushed onto a bus error
     * or address error frame when doing an RTE so don't put this info
     * onto the stack or the stack will creep every time this happens.
     */
    frame->frameSize=3;
#endif

    /* throw away any frames in the list after this frame */
    lastFrame = frame;

    frame->sr = registers[(int) PS];
    frame->pc = registers[(int) PC];

    if (registers[(int) PS] & 0x2000)
    { 
        /* return to supervisor mode... */
        return_to_super();
    }
    else
    { /* return to user mode */
        return_to_user();
    }
}

int hex(ch)
char ch;
{
  if ((ch >= 'a') && (ch <= 'f')) return (ch-'a'+10);
  if ((ch >= '0') && (ch <= '9')) return (ch-'0');
  if ((ch >= 'A') && (ch <= 'F')) return (ch-'A'+10);
  return (-1);
}


/* 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.  The host get's one chance to read it.  
   This routine does not wait for a positive acknowledge.  */


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 (1 == 0);  /* (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);
}

/* convert the memory pointed to by mem into hex, placing result in buf */
/* return a pointer to the last char put in buf (null) */
char* mem2hex(mem, buf, count)
char* mem;
char* buf;
int   count;
{
      int i;
      unsigned char ch;
      for (i=0;i<count;i++) {
          ch = *mem++;
          *buf++ = hexchars[ch >> 4];
          *buf++ = hexchars[ch % 16];
      }
      *buf = 0; 
      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)
char* buf;
char* mem;
int   count;
{
      int i;
      unsigned char ch;
      for (i=0;i<count;i++) {
          ch = hex(*buf++) << 4;
          ch = ch + hex(*buf++);
          *mem++ = ch;
      }
      return(mem);
}

/* a bus error has occurred, perform a longjmp
   to return execution and allow handling of the error */

void handle_buserror()
{
  longjmp(remcomEnv,1);
}

/* this function takes the 68000 exception number and attempts to 
   translate this number into a unix compatible signal value */
int computeSignal( exceptionVector )
int exceptionVector;
{
  int sigval;
  switch (exceptionVector) {
    case 2 : sigval = 10; break; /* bus error           */
    case 3 : sigval = 10; break; /* address error       */
    case 4 : sigval = 4;  break; /* illegal instruction */