Initial revision

1 files changed, 927 insertions, 0 deletions

diff --git a/gdb/i386-stub.c b/gdb/i386-stub.c
new file mode 100644
index 00000000000..768f00c3c8e
--- /dev/null
+++ b/gdb/i386-stub.c
@@ -0,0 +1,927 @@
+/****************************************************************************
+
+		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 386 by Jim Kingdon, Cygnus Support.
+ *
+ *  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 external function exceptionHandler() is
+ *  used to attach a specific handler to a specific 386 vector number.
+ *  It should use the same privilege level it runs at.  It should
+ *  install it as an interrupt gate so that interrupts are masked
+ *  while the handler runs.
+ *  Also, need to assign exceptionHook and oldExceptionHook.
+ *
+ *  Because gdb will sometimes write to the stack area to execute function
+ *  calls, this program cannot rely on using the supervisor stack so it
+ *  uses it's own stack area reserved in the int array remcomStack.
+ *
+ *************
+ *
+ *    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 <stdio.h>
+#include <string.h>
+
+/************************************************************************
+ *
+ * external low-level support routines
+ */
+typedef void (*ExceptionHook)(int);   /* pointer to function with int parm */
+typedef void (*Function)();           /* pointer to a function */
+
+extern void putDebugChar();	/* write a single character      */
+extern int getDebugChar();	/* read and return a single char */
+
+extern Function exceptionHandler();  /* assign an exception handler */
+extern ExceptionHook exceptionHook;  /* hook variable for errors/exceptions */
+
+/************************************************************************/
+/* BUFMAX defines the maximum number of characters in inbound/outbound buffers*/
+/* at least NUMREGBYTES*2 are needed for register packets */
+#define BUFMAX 400
+
+static char initialized;  /* boolean flag. != 0 means we've been initialized */
+
+int     remote_debug;
+/*  debug >  0 prints ill-formed commands in valid packets & checksum errors */
+
+void waitabit();
+
+static const char hexchars[]="0123456789abcdef";
+
+/* Number of registers.  */
+#define NUMREGS	16
+
+/* Number of bytes of registers.  */
+#define NUMREGBYTES (NUMREGS * 4)
+
+enum regnames {EAX, ECX, EDX, EBX, ESP, EBP, ESI, EDI,
+	       PC /* also known as eip */,
+	       PS /* also known as eflags */,
+	       CS, SS, DS, ES, FS, GS};
+
+/*
+ * these should not be static cuz they can be used outside this module
+ */
+int registers[NUMREGS];
+
+#define STACKSIZE 10000
+int remcomStack[STACKSIZE/sizeof(int)];
+static int* stackPtr = &remcomStack[STACKSIZE/sizeof(int) - 1];
+
+/*
+ * In many cases, the system will want to continue exception processing
+ * when a continue command is given.
+ * oldExceptionHook is a function to invoke in this case.
+ */
+
+static ExceptionHook oldExceptionHook;
+
+/***************************  ASSEMBLY CODE MACROS *************************/
+/* 									   */
+
+extern void
+return_to_prog ();
+
+/* Restore the program's registers (including the stack pointer, which
+   means we get the right stack and don't have to worry about popping our
+   return address and any stack frames and so on) and return.  */
+asm(".text");
+asm(".globl _return_to_prog");
+asm("_return_to_prog:");
+asm("        movw _registers+44, %ss");
+asm("        movl _registers+16, %esp");
+asm("        movl _registers+4, %ecx");
+asm("        movl _registers+8, %edx");
+asm("        movl _registers+12, %ebx");
+asm("        movl _registers+20, %ebp");
+asm("        movl _registers+24, %esi");
+asm("        movl _registers+28, %edi");
+asm("        movw _registers+48, %ds");
+asm("        movw _registers+52, %es");
+asm("        movw _registers+56, %fs");
+asm("        movw _registers+60, %gs");
+asm("        movl _registers+36, %eax");
+asm("        pushl %eax");  /* saved eflags */
+asm("        movl _registers+40, %eax");
+asm("        pushl %eax");  /* saved cs */
+asm("        movl _registers+32, %eax");
+asm("        pushl %eax");  /* saved eip */
+asm("        movl _registers, %eax");
+/* use iret to restore pc and flags together so
+   that trace flag works right.  */
+asm("        iret");
+
+#define BREAKPOINT() asm("   int $3");
+
+/* Put the error code here just in case the user cares.  */
+int gdb_i386errcode;
+/* Likewise, the vector number here (since GDB only gets the signal
+   number through the usual means, and that's not very specific).  */
+int gdb_i386vector = -1;
+
+/* GDB stores segment registers in 32-bit words (that's just the way
+   m-i386v.h is written).  So zero the appropriate areas in registers.  */
+#define SAVE_REGISTERS1() \
+  asm ("movl %eax, _registers");                                   	  \
+  asm ("movl %ecx, _registers+4");			  		     \
+  asm ("movl %edx, _registers+8");			  		     \
+  asm ("movl %ebx, _registers+12");			  		     \
+  asm ("movl %ebp, _registers+20");			  		     \
+  asm ("movl %esi, _registers+24");			  		     \
+  asm ("movl %edi, _registers+28");			  		     \
+  asm ("movw $0, %ax");							     \
+  asm ("movw %ds, _registers+48");			  		     \
+  asm ("movw %ax, _registers+50");					     \
+  asm ("movw %es, _registers+52");			  		     \
+  asm ("movw %ax, _registers+54");					     \
+  asm ("movw %fs, _registers+56");			  		     \
+  asm ("movw %ax, _registers+58");					     \
+  asm ("movw %gs, _registers+60");			  		     \
+  asm ("movw %ax, _registers+62");
+#define SAVE_ERRCODE() \
+  asm ("popl %ebx");                                  \
+  asm ("movl %ebx, _gdb_i386errcode");
+#define SAVE_REGISTERS2() \
+  asm ("popl %ebx"); /* old eip */			  		     \
+  asm ("movl %ebx, _registers+32");			  		     \
+  asm ("popl %ebx");	 /* old cs */			  		     \
+  asm ("movl %ebx, _registers+40");			  		     \
+  asm ("movw %ax, _registers+42");                                           \
+  asm ("popl %ebx");	 /* old eflags */		  		     \
+  asm ("movl %ebx, _registers+36");			 		     \
+  /* Now that we've done the pops, we can save the stack pointer.");  */   \
+  asm ("movw %ss, _registers+44");					     \
+  asm ("movw %ax, _registers+46");     	       	       	       	       	     \
+  asm ("movl %esp, _registers+16");
+
+/* See if mem_fault_routine is set, if so just IRET to that address.  */
+#define CHECK_FAULT() \
+  asm ("cmpl $0, _mem_fault_routine");					   \
+  asm ("jne mem_fault");
+
+asm (".text");
+asm ("mem_fault:");
+/* OK to clobber temp registers; we're just going to end up in set_mem_err.  */
+/* Pop error code from the stack and save it.  */
+asm ("     popl %eax");
+asm ("     movl %eax, _gdb_i386errcode");
+
+asm ("     popl %eax"); /* eip */
+/* We don't want to return there, we want to return to the function
+   pointed to by mem_fault_routine instead.  */
+asm ("     movl _mem_fault_routine, %eax");
+asm ("     popl %ecx"); /* cs (low 16 bits; junk in hi 16 bits).  */
+asm ("     popl %edx"); /* eflags */
+
+/* Remove this stack frame; when we do the iret, we will be going to
+   the start of a function, so we want the stack to look just like it
+   would after a "call" instruction.  */
+asm ("     leave");
+
+/* Push the stuff that iret wants.  */
+asm ("     pushl %edx"); /* eflags */
+asm ("     pushl %ecx"); /* cs */
+asm ("     pushl %eax"); /* eip */
+
+/* Zero mem_fault_routine.  */
+asm ("     movl $0, %eax");
+asm ("     movl %eax, _mem_fault_routine");
+
+asm ("iret");
+
+#define CALL_HOOK() asm("call _remcomHandler");
+
+/* This function is called when a i386 exception occurs.  It saves
+ * all the cpu regs in the _registers array, munges the stack a bit,
+ * and invokes an exception handler (remcom_handler).
+ *
+ * stack on entry:                       stack on exit:
+ *   old eflags                          vector number
+ *   old cs (zero-filled to 32 bits)
+ *   old eip
+ *
+ */
+extern void _catchException3();
+asm(".text");
+asm(".globl __catchException3");
+asm("__catchException3:");
+SAVE_REGISTERS1();
+SAVE_REGISTERS2();
+asm ("pushl $3");
+CALL_HOOK();
+
+/* Same thing for exception 1.  */
+extern void _catchException1();
+asm(".text");
+asm(".globl __catchException1");
+asm("__catchException1:");
+SAVE_REGISTERS1();
+SAVE_REGISTERS2();
+asm ("pushl $1");
+CALL_HOOK();
+
+/* Same thing for exception 0.  */
+extern void _catchException0();
+asm(".text");
+asm(".globl __catchException0");
+asm("__catchException0:");
+SAVE_REGISTERS1();
+SAVE_REGISTERS2();
+asm ("pushl $0");
+CALL_HOOK();
+
+/* Same thing for exception 4.  */
+extern void _catchException4();
+asm(".text");
+asm(".globl __catchException4");
+asm("__catchException4:");
+SAVE_REGISTERS1();
+SAVE_REGISTERS2();
+asm ("pushl $4");
+CALL_HOOK();
+
+/* Same thing for exception 5.  */
+extern void _catchException5();
+asm(".text");
+asm(".globl __catchException5");
+asm("__catchException5:");
+SAVE_REGISTERS1();
+SAVE_REGISTERS2();
+asm ("pushl $5");
+CALL_HOOK();
+
+/* Same thing for exception 6.  */
+extern void _catchException6();
+asm(".text");
+asm(".globl __catchException6");
+asm("__catchException6:");
+SAVE_REGISTERS1();
+SAVE_REGISTERS2();
+asm ("pushl $6");
+CALL_HOOK();
+
+/* Same thing for exception 7.  */
+extern void _catchException7();
+asm(".text");
+asm(".globl __catchException7");
+asm("__catchException7:");
+SAVE_REGISTERS1();
+SAVE_REGISTERS2();
+asm ("pushl $7");
+CALL_HOOK();
+
+/* Same thing for exception 8.  */
+extern void _catchException8();
+asm(".text");
+asm(".globl __catchException8");
+asm("__catchException8:");
+SAVE_REGISTERS1();
+SAVE_ERRCODE();
+SAVE_REGISTERS2();
+asm ("pushl $8");
+CALL_HOOK();
+
+/* Same thing for exception 9.  */
+extern void _catchException9();
+asm(".text");
+asm(".globl __catchException9");
+asm("__catchException9:");
+SAVE_REGISTERS1();
+SAVE_REGISTERS2();
+asm ("pushl $9");
+CALL_HOOK();
+
+/* Same thing for exception 10.  */
+extern void _catchException10();
+asm(".text");
+asm(".globl __catchException10");
+asm("__catchException10:");
+SAVE_REGISTERS1();
+SAVE_ERRCODE();
+SAVE_REGISTERS2();
+asm ("pushl $10");
+CALL_HOOK();
+
+/* Same thing for exception 12.  */
+extern void _catchException12();
+asm(".text");
+asm(".globl __catchException12");
+asm("__catchException12:");
+SAVE_REGISTERS1();
+SAVE_ERRCODE();
+SAVE_REGISTERS2();
+asm ("pushl $12");
+CALL_HOOK();
+
+/* Same thing for exception 16.  */
+extern void _catchException16();
+asm(".text");
+asm(".globl __catchException16");
+asm("__catchException16:");
+SAVE_REGISTERS1();
+SAVE_REGISTERS2();
+asm ("pushl $16");
+CALL_HOOK();
+
+/* For 13, 11, and 14 we have to deal with the CHECK_FAULT stuff.  */
+
+/* Same thing for exception 13.  */
+extern void _catchException13 ();
+asm (".text");
+asm (".globl __catchException13");
+asm ("__catchException13:");
+CHECK_FAULT();
+SAVE_REGISTERS1();
+SAVE_ERRCODE();
+SAVE_REGISTERS2();
+asm ("pushl $13");
+CALL_HOOK();
+
+/* Same thing for exception 11.  */
+extern void _catchException11 ();
+asm (".text");
+asm (".globl __catchException11");
+asm ("__catchException11:");
+CHECK_FAULT();
+SAVE_REGISTERS1();
+SAVE_ERRCODE();
+SAVE_REGISTERS2();
+asm ("pushl $11");
+CALL_HOOK();
+
+/* Same thing for exception 14.  */
+extern void _catchException14 ();
+asm (".text");
+asm (".globl __catchException14");
+asm ("__catchException14:");
+CHECK_FAULT();
+SAVE_REGISTERS1();
+SAVE_ERRCODE();
+SAVE_REGISTERS2();
+asm ("pushl $14");
+CALL_HOOK();
+
+/*
+ * remcomHandler is a front end for handle_exception.  It moves the
+ * stack pointer into an area reserved for debugger use.
+ */
+asm("_remcomHandler:");
+asm("           popl %eax");        /* pop off return address     */
+asm("           popl %eax");      /* get the exception number   */
+asm("		movl _stackPtr, %esp"); /* move to remcom stack area  */
+asm("		pushl %eax");	/* push exception onto stack  */
+asm("		call  _handle_exception");    /* this never returns */
+
+void _returnFromException()
+{
+  return_to_prog ();
+}
+
+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 $<data>#<checksum>     */
+void getpacket(buffer)
+char * buffer;
+{
+  unsigned char checksum;
+  unsigned char xmitcsum;
+  int  i;
+  int  count;
+  char ch;
+
+  do {
+    /* wait around for the start character, ignore all other characters */
+    while ((ch = (getDebugChar() & 0x7f)) != '$');
+    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;
+      }
+    buffer[count] = 0;
+
+    if (ch == '#') {
+      xmitcsum = hex(getDebugChar() & 0x7f) << 4;
+      xmitcsum += hex(getDebugChar() & 0x7f);
+      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]) {
+    putDebugChar(ch);
+    checksum += ch;
+    count += 1;
+  }
+
+  putDebugChar('#');
+  putDebugChar(hexchars[checksum >> 4]);
+  putDebugChar(hexchars[checksum % 16]);
+
+  } while ((getDebugChar() & 0x7f) != '+');
+
+}
+
+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 void (*volatile 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;
+      case 'P' : /* set the value of a single CPU register - return OK */
+                {
+                  int regno;
+
+                  ptr = &remcomInBuffer[1];
+                  if (hexToInt (&ptr, &regno) && *ptr++ == '=') 
+                  if (regno >= 0 && regno < NUMREGS)
+                    {
+                      hex2mem (ptr, (char *)&registers[regno], 4, 0);
+                      strcpy(remcomOutBuffer,"OK");
+                      break;
+                    }
+
+                  strcpy (remcomOutBuffer, "E01");
+                  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 */
+#if 0
+	/* Huh? This doesn't look like "nothing".
+	   m68k-stub.c and sparc-stub.c don't have it.  */
+		BREAKPOINT();
+#endif
+                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;
+
+void
+waitabit()
+{
+  int i;
+  for (i = 0; i < waitlimit; i++) ;
+}