/****************************************************************************

		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 it's 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
 *
 *    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)
 *
 * 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 <string.h>
#include <signal.h>

/************************************************************************
 *
 * external low-level support routines
 */

extern void dbg_putchar(char c);	/* write a single character      */
extern char dbg_getchar();	/* read and return a single char */
extern void ICACHE_invalidate_all();
extern int sputs(char const *pStr);
extern void print_byte(char byte);
extern void print_word(int word);

void putDebugChar(char c)
{
	dbg_putchar(c);
}

int getDebugChar()
{
	return (int)dbg_getchar();
}

void flush_i_cache()
{
	ICACHE_invalidate_all();
}

void dbg_strcpy(char *pDst, const char *pSrc)
{
	while(*pSrc)
	{
		*(pDst++) = *(pSrc++);
	}
	*pDst = *pSrc;
}

void* dbg_memset(void *pDst, int value, size_t size)
{
	char *dst = (char*)pDst;
	
	while(size)
	{
		*(dst++) = (char)value;
		size--;
	}
	return (void*)dst;
}

void* dbg_memcpy(void *pDst, const void *pSrc, size_t size )
{
	char *dst = (char*)pDst;
	char *src = (char*)pSrc;
	
	while(size)
	{
		*(dst++) = *(src++);
		size--;
	}
	return (void*)dst;
}

/************************************************************************/
/* BUFMAX defines the maximum number of characters in inbound/outbound buffers*/
/* at least NUMREGBYTES*2 are needed for register packets */
#define BUFMAX 2048

const char hexchars[]="0123456789abcdef";

#define NUMREGS 72

/* Number of bytes of registers.  */
#define NUMREGBYTES (NUMREGS * 4)

enum regnames
{
	START_CPU_REGS = 0,
	SR = START_CPU_REGS,
	CR,
	PC,
	BV,
	R00,
	R01,
	R02,
	R03,
	R04,
	R05,
	R06,
	R07,
	R08,
	R09,
	R10,
	R11,
	R12,
	R13,
	R14,
	R15,
	R16,
	R17,
	R18,
	R19,
	R20,
	R21,
	R22,
	R23,
	R24,
	R25,
	R26,
	R27,
	R28,
	R29,
	R30,
	R31,
	LO,
	HI,
	NUM_REGS
};

/* 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;
}

/* scan for the sequence $<data>#<checksum>     */

unsigned char *
getpacket (unsigned char *buffer)
{
	unsigned char checksum;
	unsigned char xmitcsum;
	int count;
	char ch;

	while (1)
	{
		/* wait around for the start character, ignore all other characters */
		while ((ch = getDebugChar ()) != '$')
		;

retry:
		checksum = 0;
		xmitcsum = -1;
		count = 0;

		/* now, read until a # or end of buffer is found */
		while (count < BUFMAX - 1)
		{
			ch = getDebugChar ();
			if (ch == '$')
				goto retry;
			if (ch == '#')
				break;
			checksum = checksum + ch;
			buffer[count] = ch;
			count = count + 1;
		}
		buffer[count] = 0;

		if (ch == '#')
		{
			ch = getDebugChar ();
			xmitcsum = hex (ch) << 4;
			ch = getDebugChar ();
			xmitcsum += hex (ch);

#ifdef WITH_CHECKSUM_CHECK	  
			if (checksum != xmitcsum)
			{
				putDebugChar ('-');	/* failed checksum */
			}
			else
#endif
			{
				putDebugChar ('+');	/* successful transfer */

				/* if a sequence char is present, reply the sequence ID */
				if (buffer[2] == ':')
				{
					putDebugChar (buffer[0]);
					putDebugChar (buffer[1]);

					return &buffer[3];
				}
				return &buffer[0];
			}
		}
	}
}

/* send the packet in buffer.  */

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

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

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

		putDebugChar('#');
		putDebugChar(hexchars[checksum >> 4]);
		putDebugChar(hexchars[checksum & 0xf]);

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

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

/* Convert the memory pointed to by mem into hex, placing result in buf.
 * Return a pointer to the last char put in buf (null), in case of mem fault,
 * return 0.
 * If MAY_FAULT is non-zero, then we will handle memory faults by returning
 * a 0, else treat a fault like any other fault in the stub.
 */

static unsigned char *
mem2hex (unsigned char *mem, unsigned char *buf, int count, int may_fault)
{
	unsigned char ch;

	while (count-- > 0)
	{
		ch = *mem++;
		if (mem_err)
			return 0;
		*buf++ = hexchars[ch >> 4];
		*buf++ = hexchars[ch & 0xf];
	}
	*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 */

static char *
hex2mem (unsigned char *buf, unsigned char *mem, int count, int may_fault)
{
	int i;
	unsigned char ch;

	for (i=0; i<count; i++)
	{
		ch = hex(*buf++) << 4;
		ch |= hex(*buf++);
		*mem++ = ch;
		if (mem_err)
			return 0;
	}
	return mem;
}

/* This table contains the mapping between SPARC hardware trap types, and
   signals, which are primarily what GDB understands.  It also indicates
   which hardware traps we need to commandeer when initializing the stub. */

struct hard_trap_info_t
{
	unsigned long tt;		/* Trap type code for SPARClite */
	unsigned long signo;	/* Signal that we map this trap into */
};

const struct hard_trap_info_t hard_trap_info[] = 
{
	{0, SIGINT},			/* Interrupt (Int) */
	{1, SIGSEGV},			/* TLB modification (Mod) */
	{2, SIGSEGV},			/* TLB load (TLBL) */
	{3, SIGSEGV},			/* TLB store (TLBS) */
	{4, SIGSEGV},			/* Address error load (ADEL) */
	{5, SIGSEGV},			/* Address error store (ADES) */
	{6, SIGBUS},			/* Bus error on instruction (IBE) */
	{7, SIGBUS},			/* Bus error on data (DBE) */
	{8, SIGUSR1},			/* Syscall instruction called (Syscall) */
	{9, SIGTRAP},			/* Breakpoint instruction called (Breakpoint) */
	{10, SIGILL},			/* Reserved instruction (RI) */
	{11, SIGXCPU},			/* Coprocessor unusable (CpU) */
	{12, SIGFPE},			/* Arithmetic overflow (Ov) */
	{0, 0}					/* Must be last */
};

/* Convert the SPARC hardware trap type code to a unix signal number. */
static unsigned long
computeSignal (unsigned long tt)
{
	// Determine linux signal from CPU specific exception code
	struct hard_trap_info_t *ht;

	for (ht = (struct hard_trap_info_t *)hard_trap_info; ht->signo != 0; ht++)
	{
		if (ht->tt == tt)
		{
			return ht->signo;
		}
	}
	return SIGHUP;		/* default for things we don't know about */
}

/*
 * While we find nice hex chars, build an int.
 * Return number of chars processed.
 */

static int
hexToInt(char **ptr, unsigned long *intValue)
{
	unsigned long numChars = 0;
	int hexValue;

	*intValue = 0;

	while (**ptr)
	{
		hexValue = hex(**ptr);
		if (hexValue < 0)
			break;

		*intValue = (*intValue << 4) | hexValue;
		numChars ++;

		(*ptr)++;
	}
	return (numChars);
}

int isBreak(unsigned long instr)
{
	return ((instr & 0xFC00003F) == 0x0000000D);
}

/*
 * This function does all command procesing for interfacing to gdb.  It
 * returns 1 if you should skip the instruction at the trap address, 0
 * otherwise.
 */

void
handle_exception (unsigned long *registers)
{
	char remcomInBuffer[BUFMAX];
	char remcomOutBuffer[BUFMAX];
	
	sputs("Entry\n");
	unsigned long tt;			/* Trap type */
	unsigned long sigval;
	unsigned long addr;
	unsigned long length;
	char *ptr;
	unsigned long *sp;
	
	addr = *((unsigned long *)registers[PC]);
	
	// is break
	if (isBreak(addr))
	{
		registers[PC] += 4;
	}

	sp = (unsigned long *)&registers[R29];

	tt = (registers[CR] >> 2) & 0x1f;

	/* reply to host that an exception has occurred */
	sigval = computeSignal(tt);
	ptr = remcomOutBuffer;

	*ptr++ = 'T';
	*ptr++ = hexchars[sigval >> 4];
	*ptr++ = hexchars[sigval & 0xf];

	*ptr++ = hexchars[37 >> 4];
	*ptr++ = hexchars[37 & 0xf];
	*ptr++ = ':';
	ptr = mem2hex((char *)&registers[PC], ptr, 4, 0);
	*ptr++ = ';';

	*ptr++ = hexchars[29 >> 4];
	*ptr++ = hexchars[29 & 0xf];
	*ptr++ = ':';
	ptr = mem2hex((char *)sp, ptr, 4, 0);
	*ptr++ = ';';

	*ptr++ = 0;

	putpacket(remcomOutBuffer);

	while (1)
	{
		remcomOutBuffer[0] = 0;

		ptr = getpacket(remcomInBuffer);
		switch (*ptr++)
		{
			case '?':
				sputs("?\n");
				remcomOutBuffer[0] = 'S';
				remcomOutBuffer[1] = hexchars[sigval >> 4];
				remcomOutBuffer[2] = hexchars[sigval & 0xf];
				remcomOutBuffer[3] = 0;
				break;

			case 'd':		/* toggle debug flag */
				sputs("d\n");
				break;

			case 'g':		/* return the value of the CPU registers */
			{
				sputs("g\n");
				ptr = remcomOutBuffer;
				 /* R00 .. R31 */
				ptr = mem2hex((char *)&registers[R00], ptr, 4*32, 0);
				/* SR, HI, LO, BADVADDR, CR, PC */
				ptr = mem2hex((char *)&registers[SR], ptr, 4, 0);
				ptr = mem2hex((char *)&registers[HI], ptr, 4, 0); 
				ptr = mem2hex((char *)&registers[LO], ptr, 4, 0);
				ptr = mem2hex((char *)&registers[BV], ptr, 4, 0);
				ptr = mem2hex((char *)&registers[CR], ptr, 4, 0);
				ptr = mem2hex((char *)&registers[PC], ptr, 4, 0);
				 /* Floating point F00 .. F31*/
				dbg_memset(ptr, '0', 8 * 32);
				ptr += 8*32;
				 /* FCSR, FIR, RESTART*/
				dbg_memset(ptr, '0', 8 * 3);
				ptr += 8*3;
				*ptr = 0;
			}
			break;

			case 'G':	   /* set the value of the CPU registers - return OK */
			{
				sputs("G\n");
				unsigned long *newsp, sr;
				sr = registers[SR];

				hex2mem(ptr, (char *)&registers[R00], 4*32, 0); /* R00 .. R31 */
				ptr += 4*32 * 2;
				/* SR, HI, LO, BADVADDR, CR, PC */
				hex2mem(ptr, (char *)&registers[SR], 4, 0); 
				ptr += 4 * 2;
				hex2mem(ptr, (char *)&registers[HI], 4, 0); 
				ptr += 4 * 2;
				hex2mem(ptr, (char *)&registers[LO], 4, 0); 
				ptr += 4 * 2;
				hex2mem(ptr, (char *)&registers[BV], 4, 0); 
				ptr += 4 * 2;
				hex2mem(ptr, (char *)&registers[CR], 4, 0); 
				ptr += 4 * 2;
				hex2mem(ptr, (char *)&registers[PC], 4, 0); 
				ptr += 4 * 2;
				*ptr = 0;

				dbg_strcpy(remcomOutBuffer,"OK");
			}
			break;

			case 'm':	  /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
			sputs("m\n");
			/* Try to read %x,%x.  */

			if (hexToInt(&ptr, &addr) && *ptr++ == ',' && hexToInt(&ptr, &length))
			{
				if (mem2hex((char *)addr, remcomOutBuffer, length, 1))
				{
					break;
				}
				dbg_strcpy (remcomOutBuffer, "E03");
			}
			else
			{
				dbg_strcpy(remcomOutBuffer,"E01");
			}
			sputs("m:"); print_word(addr); sputs(",");print_word(length); sputs("\n");
			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++ == ':')
			{
				if (hex2mem(ptr, (char *)addr, length, 1))
				{
					dbg_strcpy(remcomOutBuffer, "OK");
				}
				else
				{
					dbg_strcpy(remcomOutBuffer, "E03");
				}
			}
			else
			{
				dbg_strcpy(remcomOutBuffer, "E02");
			}
			sputs("M:"); print_word(addr); sputs(",");print_word(length); sputs("\n");
			break;

			case 'c':    /* cAA..AA    Continue at address AA..AA(optional) */
			/* try to read optional parameter, pc unchanged if no parm */

			sputs("c: PC="); print_word(registers[PC]);sputs("\n");
			if (hexToInt(&ptr, &addr))
			{
				registers[PC] = addr;
				sputs("c: addr="); print_word(addr);sputs("\n");
			}

		/* 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.
		 */

			flush_i_cache();
			return;

			/* kill the program */
			case 'k' :		/* do nothing */
				sputs("Kill\n");
				break;
		#if 0
			case 't':		/* Test feature */
				break;
		#endif
			case 'r':		/* Reset */
				// Perform reset
				sputs("Reset\n");
				break;
		}	/* switch */
		/* reply to the request */
		putpacket(remcomOutBuffer);
	}
	sputs("Exit\n");

}