common/kgdb.c - filogic/uboot - Gitiles

 /* 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 <asm/ptrace.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?\n");
 		return (0);
 	}

 	/* probably should check which exception occurred as well */
 	if (longjmp_on_fault) {
 		longjmp_on_fault = 0;
 		kgdb_longjmp(error_jmp_buf, KGDBERR_MEMFAULT);
 		panic("kgdb longjump failed!\n");
 	}

 	if (kgdb_active) {
 		printf("kgdb: unexpected exception from within kgdb\n");
 		return (0);
 	}
 	kgdb_active = 1;

 	kgdb_interruptible(0);

 	printf("kgdb: handle_exception; trap [0x%x]\n", kgdb_trap(regs));

 	if (kgdb_setjmp(error_jmp_buf) != 0)
 		panic("kgdb: error or fault in entry init!\n");

 	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\n", 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\n", 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\n", remcomOutBuffer);
 #endif

 		/* reply to the request */
 		putpacket((unsigned char *)&remcomOutBuffer);

 	} /* while(1) */
 }

 /*
  * kgdb_init must be called *after* the
  * monitor is relocated into ram
  */
 int kgdb_init(void)
 {
 	puts("KGDB:  ");

 	kgdb_serial_init();
 	debugger_exception_handler = handle_exception;
 	initialized = 1;

 	putDebugStr("kgdb ready\n");
 	puts("ready\n");

 	return 0;
 }

 void
 kgdb_error(int errnum)
 {
 	longjmp_on_fault = 0;
 	kgdb_longjmp(error_jmp_buf, errnum);
 	panic("kgdb_error: longjmp failed!\n");
 }

 /* 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\n");
 		return;
 	}

 	kgdb_breakpoint(0, 0);
 }

 int
 do_kgdb(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 {
     printf("Entering KGDB mode via exception handler...\n\n");
     kgdb_breakpoint(argc - 1, argv + 1);
     printf("\nReturned from KGDB mode\n");
     return 0;
 }

 U_BOOT_CMD(
 	kgdb, CONFIG_SYS_MAXARGS, 1,	do_kgdb,
 	"enter gdb remote debug mode",
 	"[arg0 arg1 .. argN]\n"
 	"    - executes a breakpoint so that kgdb mode is\n"
 	"      entered via the exception handler. To return\n"
 	"      to the monitor, the remote gdb debugger must\n"
 	"      execute a \"continue\" or \"quit\" command.\n"
 	"\n"
 	"      if a program is loaded by the remote gdb, any args\n"
 	"      passed to the kgdb command are given to the loaded\n"
 	"      program if it is executed (see the \"hello_world\"\n"
 	"      example program in the U-Boot examples directory)."
 );
	/* 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 <asm/ptrace.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?\n");
	return (0);
	}

	/* probably should check which exception occurred as well */
	if (longjmp_on_fault) {
	longjmp_on_fault = 0;
	kgdb_longjmp(error_jmp_buf, KGDBERR_MEMFAULT);
	panic("kgdb longjump failed!\n");
	}

	if (kgdb_active) {
	printf("kgdb: unexpected exception from within kgdb\n");
	return (0);
	}
	kgdb_active = 1;

	kgdb_interruptible(0);

	printf("kgdb: handle_exception; trap [0x%x]\n", kgdb_trap(regs));

	if (kgdb_setjmp(error_jmp_buf) != 0)
	panic("kgdb: error or fault in entry init!\n");

	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\n", 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\n", 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\n", remcomOutBuffer);
	#endif

	/* reply to the request */
	putpacket((unsigned char *)&remcomOutBuffer);

	} /* while(1) */
	}

	/*
	* kgdb_init must be called after the
	* monitor is relocated into ram
	*/
	int kgdb_init(void)
	{
	puts("KGDB: ");

	kgdb_serial_init();
	debugger_exception_handler = handle_exception;
	initialized = 1;

	putDebugStr("kgdb ready\n");
	puts("ready\n");

	return 0;
	}

	void
	kgdb_error(int errnum)
	{
	longjmp_on_fault = 0;
	kgdb_longjmp(error_jmp_buf, errnum);
	panic("kgdb_error: longjmp failed!\n");
	}

	/* 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\n");
	return;
	}

	kgdb_breakpoint(0, 0);
	}

	int
	do_kgdb(struct cmd_tbl cmdtp, int flag, int argc, char const argv[])
	{
	printf("Entering KGDB mode via exception handler...\n\n");
	kgdb_breakpoint(argc - 1, argv + 1);
	printf("\nReturned from KGDB mode\n");
	return 0;
	}

	U_BOOT_CMD(
	kgdb, CONFIG_SYS_MAXARGS, 1, do_kgdb,
	"enter gdb remote debug mode",
	"[arg0 arg1 .. argN]\n"
	" - executes a breakpoint so that kgdb mode is\n"
	" entered via the exception handler. To return\n"
	" to the monitor, the remote gdb debugger must\n"
	" execute a \"continue\" or \"quit\" command.\n"
	"\n"
	" if a program is loaded by the remote gdb, any args\n"
	" passed to the kgdb command are given to the loaded\n"
	" program if it is executed (see the \"hello_world\"\n"
	" example program in the U-Boot examples directory)."
	);