/* taken from arch/powerpc/kernel/ppc-stub.c */
  
  /****************************************************************************
  
  		THIS SOFTWARE IS NOT COPYRIGHTED
  
     HP offers the following for use in the public domain.  HP makes no
     warranty with regard to the software or its performance and the
     user accepts the software "AS IS" with all faults.
  
     HP DISCLAIMS ANY WARRANTIES, EXPRESS OR IMPLIED, WITH REGARD
     TO THIS SOFTWARE INCLUDING BUT NOT LIMITED TO THE WARRANTIES
     OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  
  ****************************************************************************/
  
  /****************************************************************************
   *  Header: remcom.c,v 1.34 91/03/09 12:29:49 glenne Exp $
   *
   *  Module name: remcom.c $
   *  Revision: 1.34 $
   *  Date: 91/03/09 12:29:49 $
   *  Contributor:     Lake Stevens Instrument Division$
   *
   *  Description:     low level support for gdb debugger. $
   *
   *  Considerations:  only works on target hardware $
   *
   *  Written by:      Glenn Engel $
   *  ModuleState:     Experimental $
   *
   *  NOTES:           See Below $
   *
   *  Modified for SPARC by Stu Grossman, Cygnus Support.
   *
   *  This code has been extensively tested on the Fujitsu SPARClite demo board.
   *
   *  To enable debugger support, two things need to happen.  One, a
   *  call to set_debug_traps() is necessary in order to allow any breakpoints
   *  or error conditions to be properly intercepted and reported to gdb.
   *  Two, a breakpoint needs to be generated to begin communication.  This
   *  is most easily accomplished by a call to breakpoint().  Breakpoint()
   *  simulates a breakpoint by executing a trap #1.
   *
   *************
   *
   *    The following gdb commands are supported:
   *
   * command          function                               Return value
   *
   *    g             return the value of the CPU registers  hex data or ENN
   *    G             set the value of the CPU registers     OK or ENN
   *    qOffsets      Get section offsets.  Reply is Text=xxx;Data=yyy;Bss=zzz
   *
   *    mAA..AA,LLLL  Read LLLL bytes at address AA..AA      hex data or ENN
   *    MAA..AA,LLLL: Write LLLL bytes at address AA.AA      OK or ENN
   *
   *    c             Resume at current address              SNN   ( signal NN)
   *    cAA..AA       Continue at address AA..AA             SNN
   *
   *    s             Step one instruction                   SNN
   *    sAA..AA       Step one instruction from AA..AA       SNN
   *
   *    k             kill
   *
   *    ?             What was the last sigval ?             SNN   (signal NN)
   *
   *    bBB..BB	    Set baud rate to BB..BB		   OK or BNN, then sets
   *							   baud rate
   *
   * All commands and responses are sent with a packet which includes a
   * checksum.  A packet consists of
   *
   * $<packet info>#<checksum>.
   *
   * where
   * <packet info> :: <characters representing the command or response>
   * <checksum>    :: <two hex digits computed as modulo 256 sum of <packetinfo>>
   *
   * When a packet is received, it is first acknowledged with either '+' or '-'.
   * '+' indicates a successful transfer.  '-' indicates a failed transfer.
   *
   * Example:
   *
   * Host:                  Reply:
   * $m0,10#2a               +$00010203040506070809101112131415#42
   *
   ****************************************************************************/
  
  #include <common.h>
  
  #include <kgdb.h>
  #include <command.h>
  
  #undef KGDB_DEBUG
  
  /*
   * BUFMAX defines the maximum number of characters in inbound/outbound buffers
   */
  #define BUFMAX 1024
  static char remcomInBuffer[BUFMAX];
  static char remcomOutBuffer[BUFMAX];
  static char remcomRegBuffer[BUFMAX];
  
  static int initialized = 0;
  static int kgdb_active;
  static struct pt_regs entry_regs;
  static long error_jmp_buf[BUFMAX/2];
  static int longjmp_on_fault = 0;
  #ifdef KGDB_DEBUG
  static int kdebug = 1;
  #endif
  
  static const char hexchars[]="0123456789abcdef";
  
  /* Convert ch from a hex digit to an int */
  static int
  hex(unsigned 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;
  }
  
  /* Convert the memory pointed to by mem into hex, placing result in buf.
   * Return a pointer to the last char put in buf (null).
   */
  static unsigned char *
  mem2hex(char *mem, char *buf, int count)
  {
  	char *tmp;
  	unsigned char ch;
  
  	/*
  	 * We use the upper half of buf as an intermediate buffer for the
  	 * raw memory copy.  Hex conversion will work against this one.
  	 */
  	tmp = buf + count;
  	longjmp_on_fault = 1;
  
  	memcpy(tmp, mem, count);
  
  	while (count-- > 0) {
  		ch = *tmp++;
  		*buf++ = hexchars[ch >> 4];
  		*buf++ = hexchars[ch & 0xf];
  	}
  	*buf = 0;
  	longjmp_on_fault = 0;
  	return (unsigned char *)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 fetched from buf.
  */
  static char *
  hex2mem(char *buf, char *mem, int count)
  {
  	int hexValue;
  	char *tmp_raw, *tmp_hex;
  
  	/*
  	 * We use the upper half of buf as an intermediate buffer for the
  	 * raw memory that is converted from hex.
  	 */
  	tmp_raw = buf + count * 2;
  	tmp_hex = tmp_raw - 1;
  
  	longjmp_on_fault = 1;
  	while (tmp_hex >= buf) {
  		tmp_raw--;
  		hexValue = hex(*tmp_hex--);
  		if (hexValue < 0)
  			kgdb_error(KGDBERR_NOTHEXDIG);
  		*tmp_raw = hexValue;
  		hexValue = hex(*tmp_hex--);
  		if (hexValue < 0)
  			kgdb_error(KGDBERR_NOTHEXDIG);
  		*tmp_raw |= hexValue << 4;
  
  	}
  
  	memcpy(mem, tmp_raw, count);
  
  	kgdb_flush_cache_range((void *)mem, (void *)(mem+count));
  	longjmp_on_fault = 0;
  
  	return buf;
  }
  
  /*
   * While we find nice hex chars, build an int.
   * Return number of chars processed.
   */
  static int
  hexToInt(char **ptr, int *intValue)
  {
  	int numChars = 0;
  	int hexValue;
  
  	*intValue = 0;
  
  	longjmp_on_fault = 1;
  	while (**ptr) {
  		hexValue = hex(**ptr);
  		if (hexValue < 0)
  			break;
  
  		*intValue = (*intValue << 4) | hexValue;
  		numChars ++;
  
  		(*ptr)++;
  	}
  	longjmp_on_fault = 0;
  
  	return (numChars);
  }
  
  /* scan for the sequence $<data>#<checksum>     */
  static void
  getpacket(char *buffer)
  {
  	unsigned char checksum;
  	unsigned char xmitcsum;
  	int i;
  	int count;
  	unsigned char ch;
  
  	do {
  		/* wait around for the start character, ignore all other
  		 * characters */
  		while ((ch = (getDebugChar() & 0x7f)) != '$') {
  #ifdef KGDB_DEBUG
  			if (kdebug)
  				putc(ch);
  #endif
  			;
  		}
  
  		checksum = 0;
  		xmitcsum = -1;
  
  		count = 0;
  
  		/* now, read until a # or end of buffer is found */
  		while (count < BUFMAX) {
  			ch = getDebugChar() & 0x7f;
  			if (ch == '#')
  				break;
  			checksum = checksum + ch;
  			buffer[count] = ch;
  			count = count + 1;
  		}
  
  		if (count >= BUFMAX)
  			continue;
  
  		buffer[count] = 0;
  
  		if (ch == '#') {
  			xmitcsum = hex(getDebugChar() & 0x7f) << 4;
  			xmitcsum |= hex(getDebugChar() & 0x7f);
  			if (checksum != xmitcsum)
  				putDebugChar('-');	/* failed checksum */
  			else {
  				putDebugChar('+'); /* successful transfer */
  				/* if a sequence char is present, reply the 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.  */
  static void
  putpacket(unsigned char *buffer)
  {
  	unsigned char checksum;
  	int count;
  	unsigned char ch, recv;
  
  	/*  $<packet info>#<checksum>. */
  	do {
  		putDebugChar('$');
  		checksum = 0;
  		count = 0;
  
  		while ((ch = buffer[count])) {
  			putDebugChar(ch);
  			checksum += ch;
  			count += 1;
  		}
  
  		putDebugChar('#');
  		putDebugChar(hexchars[checksum >> 4]);
  		putDebugChar(hexchars[checksum & 0xf]);
  		recv = getDebugChar();
  	} while ((recv & 0x7f) != '+');
  }
  
  /*
   * This function does all command processing for interfacing to gdb.
   */
  static int
  handle_exception (struct pt_regs *regs)
  {
  	int addr;
  	int length;
  	char *ptr;
  	kgdb_data kd;
  	int i;
  
  	if (!initialized) {
  		printf("kgdb: exception before kgdb is initialized! huh?
  ");
  		return (0);
  	}
  
  	/* probably should check which exception occured as well */
  	if (longjmp_on_fault) {
  		longjmp_on_fault = 0;
  		kgdb_longjmp(error_jmp_buf, KGDBERR_MEMFAULT);
  		panic("kgdb longjump failed!
  ");
  	}
  
  	if (kgdb_active) {
  		printf("kgdb: unexpected exception from within kgdb
  ");
  		return (0);
  	}
  	kgdb_active = 1;
  
  	kgdb_interruptible(0);
  
  	printf("kgdb: handle_exception; trap [0x%x]
  ", kgdb_trap(regs));
  
  	if (kgdb_setjmp(error_jmp_buf) != 0)
  		panic("kgdb: error or fault in entry init!
  ");
  
  	kgdb_enter(regs, &kd);
  
  	entry_regs = *regs;
  
  	ptr = remcomOutBuffer;
  
  	*ptr++ = 'T';
  
  	*ptr++ = hexchars[kd.sigval >> 4];
  	*ptr++ = hexchars[kd.sigval & 0xf];
  
  	for (i = 0; i < kd.nregs; i++) {
  		kgdb_reg *rp = &kd.regs[i];
  
  		*ptr++ = hexchars[rp->num >> 4];
  		*ptr++ = hexchars[rp->num & 0xf];
  		*ptr++ = ':';
  		ptr = (char *)mem2hex((char *)&rp->val, ptr, 4);
  		*ptr++ = ';';
  	}
  
  	*ptr = 0;
  
  #ifdef KGDB_DEBUG
  	if (kdebug)
  		printf("kgdb: remcomOutBuffer: %s
  ", remcomOutBuffer);
  #endif
  
  	putpacket((unsigned char *)&remcomOutBuffer);
  
  	while (1) {
  		volatile int errnum;
  
  		remcomOutBuffer[0] = 0;
  
  		getpacket(remcomInBuffer);
  		ptr = &remcomInBuffer[1];
  
  #ifdef KGDB_DEBUG
  		if (kdebug)
  			printf("kgdb:  remcomInBuffer: %s
  ", remcomInBuffer);
  #endif
  
  		errnum = kgdb_setjmp(error_jmp_buf);
  
  		if (errnum == 0) switch (remcomInBuffer[0]) {
  
  		case '?':               /* report most recent signal */
  			remcomOutBuffer[0] = 'S';
  			remcomOutBuffer[1] = hexchars[kd.sigval >> 4];
  			remcomOutBuffer[2] = hexchars[kd.sigval & 0xf];
  			remcomOutBuffer[3] = 0;
  			break;
  
  #ifdef KGDB_DEBUG
  		case 'd':
  			/* toggle debug flag */
  			kdebug ^= 1;
  			break;
  #endif
  
  		case 'g':	/* return the value of the CPU registers. */
  			length = kgdb_getregs(regs, remcomRegBuffer, BUFMAX);
  			mem2hex(remcomRegBuffer, remcomOutBuffer, length);
  			break;
  
  		case 'G':   /* set the value of the CPU registers */
  			length = strlen(ptr);
  			if ((length & 1) != 0) kgdb_error(KGDBERR_BADPARAMS);
  			hex2mem(ptr, remcomRegBuffer, length/2);
  			kgdb_putregs(regs, remcomRegBuffer, length/2);
  			strcpy(remcomOutBuffer,"OK");
  			break;
  
  		case 'm':	/* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
  				/* Try to read %x,%x.  */
  
  			if (hexToInt(&ptr, &addr)
  			    && *ptr++ == ','
  			    && hexToInt(&ptr, &length))	{
  				mem2hex((char *)addr, remcomOutBuffer, length);
  			} else {
  				kgdb_error(KGDBERR_BADPARAMS);
  			}
  			break;
  
  		case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK */
  			/* Try to read '%x,%x:'.  */
  
  			if (hexToInt(&ptr, &addr)
  			    && *ptr++ == ','
  			    && hexToInt(&ptr, &length)
  			    && *ptr++ == ':') {
  				hex2mem(ptr, (char *)addr, length);
  				strcpy(remcomOutBuffer, "OK");
  			} else {
  				kgdb_error(KGDBERR_BADPARAMS);
  			}
  			break;
  
  
  		case 'k':    /* kill the program, actually return to monitor */
  			kd.extype = KGDBEXIT_KILL;
  			*regs = entry_regs;
  			goto doexit;
  
  		case 'C':    /* CSS  continue with signal SS */
  			*ptr = '\0';	/* ignore the signal number for now */
  			/* fall through */
  
  		case 'c':    /* cAA..AA  Continue; address AA..AA optional */
  			/* try to read optional parameter, pc unchanged if no parm */
  			kd.extype = KGDBEXIT_CONTINUE;
  
  			if (hexToInt(&ptr, &addr)) {
  				kd.exaddr = addr;
  				kd.extype |= KGDBEXIT_WITHADDR;
  			}
  
  			goto doexit;
  
  		case 'S':    /* SSS  single step with signal SS */
  			*ptr = '\0';	/* ignore the signal number for now */
  			/* fall through */
  
  		case 's':
  			kd.extype = KGDBEXIT_SINGLE;
  
  			if (hexToInt(&ptr, &addr)) {
  				kd.exaddr = addr;
  				kd.extype |= KGDBEXIT_WITHADDR;
  			}
  
  		doexit:
  /* Need to flush the instruction cache here, as we may have deposited a
   * breakpoint, and the icache probably has no way of knowing that a data ref to
   * some location may have changed something that is in the instruction cache.
   */
  			kgdb_flush_cache_all();
  			kgdb_exit(regs, &kd);
  			kgdb_active = 0;
  			kgdb_interruptible(1);
  			return (1);
  
  		case 'r':		/* Reset (if user process..exit ???)*/
  			panic("kgdb reset.");
  			break;
  
  		case 'P':    /* Pr=v  set reg r to value v (r and v are hex) */
  			if (hexToInt(&ptr, &addr)
  			    && *ptr++ == '='
  			    && ((length = strlen(ptr)) & 1) == 0) {
  				hex2mem(ptr, remcomRegBuffer, length/2);
  				kgdb_putreg(regs, addr,
  					remcomRegBuffer, length/2);
  				strcpy(remcomOutBuffer,"OK");
  			} else {
  				kgdb_error(KGDBERR_BADPARAMS);
  			}
  			break;
  		}			/* switch */
  
  		if (errnum != 0)
  			sprintf(remcomOutBuffer, "E%02d", errnum);
  
  #ifdef KGDB_DEBUG
  		if (kdebug)
  			printf("kgdb: remcomOutBuffer: %s
  ", remcomOutBuffer);
  #endif
  
  		/* reply to the request */
  		putpacket((unsigned char *)&remcomOutBuffer);
  
  	} /* while(1) */
  }
  
  /*
   * kgdb_init must be called *after* the
   * monitor is relocated into ram
   */
  void
  kgdb_init(void)
  {
  	kgdb_serial_init();
  	debugger_exception_handler = handle_exception;
  	initialized = 1;
  
  	putDebugStr("kgdb ready
  ");
  	puts("ready
  ");
  }
  
  void
  kgdb_error(int errnum)
  {
  	longjmp_on_fault = 0;
  	kgdb_longjmp(error_jmp_buf, errnum);
  	panic("kgdb_error: longjmp failed!
  ");
  }
  
  /* Output string in GDB O-packet format if GDB has connected. If nothing
     output, returns 0 (caller must then handle output). */
  int
  kgdb_output_string (const char* s, unsigned int count)
  {
  	char buffer[512];
  
  	count = (count <= (sizeof(buffer) / 2 - 2))
  		? count : (sizeof(buffer) / 2 - 2);
  
  	buffer[0] = 'O';
  	mem2hex ((char *)s, &buffer[1], count);
  	putpacket((unsigned char *)&buffer);
  
  	return 1;
  }
  
  void
  breakpoint(void)
  {
  	if (!initialized) {
  		printf("breakpoint() called b4 kgdb init
  ");
  		return;
  	}
  
  	kgdb_breakpoint(0, 0);
  }
  
  int
  do_kgdb(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
  {
      printf("Entering KGDB mode via exception handler...
  
  ");
      kgdb_breakpoint(argc - 1, argv + 1);
      printf("
  Returned from KGDB mode
  ");
      return 0;
  }
  
  U_BOOT_CMD(
  	kgdb, CONFIG_SYS_MAXARGS, 1,	do_kgdb,
  	"enter gdb remote debug mode",
  	"[arg0 arg1 .. argN]
  "
  	"    - executes a breakpoint so that kgdb mode is
  "
  	"      entered via the exception handler. To return
  "
  	"      to the monitor, the remote gdb debugger must
  "
  	"      execute a \"continue\" or \"quit\" command.
  "
  	"
  "
  	"      if a program is loaded by the remote gdb, any args
  "
  	"      passed to the kgdb command are given to the loaded
  "
  	"      program if it is executed (see the \"hello_world\"
  "
  	"      example program in the U-Boot examples directory)."
  );