Snapshot of stand alone i386 NLM debugging stub. Currently sanitized

out because it contains Novell proprietary code.

1 files changed, 1057 insertions, 0 deletions

diff --git a/gdb/i386-nlmstub.c b/gdb/i386-nlmstub.c
new file mode 100644
index 0000000..5604ed6
--- /dev/null
+++ b/gdb/i386-nlmstub.c
@@ -0,0 +1,1057 @@
+/* i386-nlmstub.c -- NLM debugging stub for the i386.
+
+   This is originally based on an m68k software stub written by Glenn
+   Engel at HP, but has changed quite a bit.  It was modified for the
+   i386 by Jim Kingdon, Cygnus Support.  It was modified to run under
+   NetWare by Ian Lance Taylor, Cygnus Support.
+
+   This code is intended to produce an NLM (a NetWare Loadable Module)
+   to run under NetWare on an i386 platform.  To create the NLM,
+   compile this code into an object file using the NLM SDK on any i386
+   host, and use the nlmconv program (available in the GNU binutils)
+   to transform the resulting object file into an NLM.  */
+
+/****************************************************************************
+
+		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.
+
+****************************************************************************/
+
+/****************************************************************************
+ *
+ *    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 <dfs.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <time.h>
+#include <aio.h>
+#include <conio.h>
+#include <advanced.h>
+#include <debugapi.h>
+#include <process.h>
+
+/************************************************************************/
+/*****************************************************************************
+ *
+ *	(C) Copyright 1988-1993 Novell, Inc.
+ *	All Rights Reserved.
+ *
+ *	This program is an unpublished copyrighted work which is proprietary
+ *	to Novell, Inc. and contains confidential information that is not
+ *	to be reproduced or disclosed to any other person or entity without
+ *	prior written consent from Novell, Inc. in each and every instance.
+ *
+ *	WARNING:  Unauthorized reproduction of this program as well as
+ *	unauthorized preparation of derivative works based upon the
+ *	program or distribution of copies by sale, rental, lease or
+ *	lending are violations of federal copyright laws and state trade
+ *	secret laws, punishable by civil and criminal penalties.
+ *
+ *  $release$
+ *  $modname: loadstuff.h$
+ *  $version: 1.37$
+ *  $date: Fri, Jan 15, 1993$
+ *
+ ****************************************************************************/
+
+
+/* WARNING:  THIS IS NOT A COMPLETE OS HEADER FILE - DON'T GET CONFUSED
+ ***********************************************************************
+ * The information is this file is a subset of the OS LOADER.H.			
+ * This file was created to reveal the LoadDefinitionStrucutre and some 
+ * associated information to Cygnus Support to assist them in their 		
+ * efforts to develop GNU netware utilities.	 Don't confuse this file
+ * with LOADER.H or any other actually supported NetWare header.
+
+************************************************************************/
+
+struct LoadDefinitionStructure
+{
+	struct LoadDefinitionStructure *LDLink;
+	struct LoadDefinitionStructure *LDKillLink;
+	struct LoadDefinitionStructure *LDScanLink;
+	struct ResourceTagStructure	*LDResourceList;
+	LONG LDIdentificationNumber;
+	LONG LDCodeImageOffset;
+	LONG LDCodeImageLength;
+	LONG LDDataImageOffset;
+	LONG LDDataImageLength;
+	LONG LDUninitializedDataLength;
+	LONG LDCustomDataOffset;
+	LONG LDCustomDataSize;
+	LONG LDFlags;
+	LONG LDType;
+	LONG (*LDInitializationProcedure)(
+			struct LoadDefinitionStructure *LoadRecord,
+			struct ScreenStruct *screenID,
+			BYTE *CommandLine,
+			BYTE *loadDirectoryPath,
+			LONG uninitializedDataLength,
+			LONG fileHandle,
+			LONG (*ReadRoutine)(
+					LONG fileHandle,
+					LONG offset,
+					void *buffer,
+					LONG numberOfBytes),
+			LONG customDataOffset,
+			LONG customDataSize);
+	void (*LDExitProcedure)(void);
+	LONG (*LDCheckUnloadProcedure)(
+			struct ScreenStruct *screenID);
+	struct ExternalPublicDefinitionStructure *LDPublics;
+	BYTE LDFileName[36];
+	BYTE LDName[128];
+	LONG *LDCLIBLoadStructure;
+	LONG *LDNLMDebugger;
+	LONG LDParentID;
+	LONG LDReservedForCLIB;
+	LONG Reserved0;
+	LONG Reserved1;
+	void *LDModuleObjectHandle;	/* If Instrumented BEW 10/16/90 */
+	LONG LDMajorVersion;
+	LONG LDMinorVersion;
+	LONG LDRevision;
+	LONG LDYear;
+	LONG LDMonth;
+	LONG LDDay;
+	BYTE *LDCopyright;
+	LONG LDAllocAvailBytes;
+	LONG LDAllocFreeCount;
+	LONG LDLastGarbCollect;
+	LONG LDAlloc16Lists[64];
+	LONG LDAlloc256Lists[12];
+	LONG LDAlloc4kList;
+	struct DomainStructure *LDDomainID;	/* This must be non-zero for the Alloc Hunt code to work right. */
+										/* It also points to the domain structure. */
+	struct LoadDefinitionStructure *LDEnvLink;
+	void *LDAllocPagesListHead;
+	struct ExternalPublicDefinitionStructure *LDTempPublicList;
+	LONG LDMessageLanguage; 	/* for enabling */
+	BYTE **LDMessages;			/* for enabling */
+	LONG LDMessageCount;		/* for enabling */
+	BYTE *LDHelpFile;			/* for enabling */
+	LONG LDMessageBufferSize;	/* for enabling */
+	LONG LDHelpBufferSize;		/* for enabling */
+	LONG LDSharedCodeOffset;		/* for protection */
+	LONG LDSharedCodeLength;		/* for protection */
+	LONG LDSharedDataOffset;		/* for protection */
+	LONG LDSharedDataLength;		/* for protection */
+	LONG (*LDSharedInitProcedure)(
+			struct LoadDefinitionStructure *LoadRecord,
+			struct ScreenStruct *screenID,
+			BYTE *CommandLine);
+	void (*LDSharedExitProcedure)(void);
+	LONG LDRPCDataTable;
+	LONG LDRealRPCDataTable;
+	LONG LDRPCDataTableSize;
+	LONG LDNumberOfReferencedPublics;
+	struct ExternalPublicDefinitionStructure **LDReferencedPublics;
+	LONG LDNumberOfReferencedExports;
+};
+
+
+/*	define the LDFlags.	*/
+
+#define LDModuleIsReEntrantBit			0x00000001
+#define LDModuleCanBeMultiplyLoadedBit	0x00000002
+#define LDSynchronizeStart					0x00000004
+#define LDPseudoPreemptionBit				0x00000008
+#define LDLoadInOSDomain					0x00000010
+#define LDDontUnloadBit 					0x20000000
+#define LDModuleIsBeingDebugged 			0x40000000
+#define LDMemoryOn4KBoundriesBit			0x80000000
+
+/* LoadModule load options */
+#define LO_NORMAL				0x0000
+#define LO_STARTUP			0x0001
+#define LO_PROTECT			0x0002
+#define LO_DEBUG				0x0004
+#define LO_AUTO_LOAD			0x0008
+#define LO_DONT_PROMPT		0x0010
+#define LO_LOAD_LOW			0x0020
+#define LO_RETURN_HANDLE	0x0040
+#define LO_LOAD_SILENT		0x0080
+
+/* Loader returned error codes */
+#define LOAD_COULD_NOT_FIND_FILE				1
+#define LOAD_ERROR_READING_FILE 				2
+#define LOAD_NOT_NLM_FILE_FORMAT				3
+#define LOAD_WRONG_NLM_FILE_VERSION			4
+#define LOAD_REENTRANT_INITIALIZE_FAILURE	5
+#define LOAD_CAN_NOT_LOAD_MULTIPLE_COPIES	6
+#define LOAD_ALREADY_IN_PROGRESS				7
+#define LOAD_NOT_ENOUGH_MEMORY				8
+#define LOAD_INITIALIZE_FAILURE 				9
+#define LOAD_INCONSISTENT_FILE_FORMAT		10
+#define LOAD_CAN_NOT_LOAD_AT_STARTUP		11
+#define LOAD_AUTO_LOAD_MODULES_NOT_LOADED	12
+#define LOAD_UNRESOLVED_EXTERNAL				13
+#define LOAD_PUBLIC_ALREADY_DEFINED			14
+#define LOAD_XDC_DATA_ERROR					15
+#define LOAD_NOT_OS_DOMAIN						16
+
+/****************************************************************************/
+
+/* The main thread ID.  */
+static int mainthread;
+
+/* The debug server thread ID.  */
+static int debugthread;
+
+/* The LoadDefinitionStructure of the NLM being debugged.  */
+static struct LoadDefinitionStructure *handle;
+
+/* Whether we have connected to gdb.  */
+static int talking;
+
+/* The actual first instruction in the program.  */
+static unsigned char first_insn;
+
+/* An error message for the main thread to print.  */
+static char *error_message;
+
+/* The AIO port handle.  */
+static int AIOhandle;
+
+/* The console screen.  */
+static int console_screen;
+
+/* BUFMAX defines the maximum number of characters in inbound/outbound
+   buffers.  At least NUMREGBYTES*2 are needed for register packets */
+#define BUFMAX 400
+
+/* remote_debug > 0 prints ill-formed commands in valid packets and
+   checksum errors. */
+static int remote_debug = 1;
+
+static const char hexchars[] = "0123456789abcdef";
+
+/* Number of bytes of registers.  */
+#define NUMREGBYTES 64
+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};
+
+/* Register values.  */
+static int registers[NUMREGBYTES/4];
+
+/* Read a character from the serial port.  This must busy wait, but
+   that's OK because we will be the only thread running anyhow.  */
+
+static int
+getDebugChar ()
+{
+  int err;
+  LONG got;
+  unsigned char ret;
+
+  do
+    {
+      err = AIOReadData (AIOhandle, (char *) &ret, 1, &got);
+      if (err != 0)
+	{
+	  error_message = "AIOReadData failed";
+	  ResumeThread (mainthread);
+	  return -1;
+	}
+    }
+  while (got == 0);
+
+  return ret;
+}
+
+/* Write a character to the serial port.  Returns 0 on failure,
+   non-zero on success.  */
+
+static int
+putDebugChar (c)
+     unsigned char c;
+{
+  int err;
+  LONG put;
+
+  err = AIOWriteData (AIOhandle, (char *) &c, 1, &put);
+  if (err != 0 || put != 1)
+    {
+      error_message = "AIOWriteData failed";
+      ResumeThread (mainthread);
+      return 0;
+    }
+  return 1;
+}
+
+/* Get the registers out of the frame information.  */
+
+static void
+frame_to_registers (frame, regs)
+     T_TSS_StackFrame *frame;
+     int *regs;
+{
+  regs[EAX] = frame->ExceptionEAX;
+  regs[ECX] = frame->ExceptionECX;
+  regs[EDX] = frame->ExceptionEDX;
+  regs[EBX] = frame->ExceptionEBX;
+  regs[ESP] = frame->ExceptionESP;
+  regs[EBP] = frame->ExceptionEBP;
+  regs[ESI] = frame->ExceptionESI;
+  regs[EDI] = frame->ExceptionEDI;
+  regs[PC] = frame->ExceptionEIP;
+  regs[PS] = frame->ExceptionSystemFlags;
+  regs[CS] = frame->ExceptionCS[0];
+  regs[SS] = frame->ExceptionSS[0];
+  regs[DS] = frame->ExceptionDS[0];
+  regs[ES] = frame->ExceptionES[0];
+  regs[FS] = frame->ExceptionFS[0];
+  regs[GS] = frame->ExceptionGS[0];
+}
+
+/* Put the registers back into the frame information.  */
+
+static void
+registers_to_frame (regs, frame)
+     int *regs;
+     T_TSS_StackFrame *frame;
+{
+  frame->ExceptionEAX = regs[EAX];
+  frame->ExceptionECX = regs[ECX];
+  frame->ExceptionEDX = regs[EDX];
+  frame->ExceptionEBX = regs[EBX];
+  frame->ExceptionESP = regs[ESP];
+  frame->ExceptionEBP = regs[EBP];
+  frame->ExceptionESI = regs[ESI];
+  frame->ExceptionEDI = regs[EDI];
+  frame->ExceptionEIP = regs[PC];
+  frame->ExceptionSystemFlags = regs[PS];
+  frame->ExceptionCS[0] = regs[CS];
+  frame->ExceptionSS[0] = regs[SS];
+  frame->ExceptionDS[0] = regs[DS];
+  frame->ExceptionES[0] = regs[ES];
+  frame->ExceptionFS[0] = regs[FS];
+  frame->ExceptionGS[0] = regs[GS];
+}
+
+/* Turn a hex character into a number.  */
+
+static 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 $<data>#<checksum>.  Returns 0 on failure,
+   non-zero on success.  */
+
+static int
+getpacket (buffer)
+     char * buffer;
+{
+  unsigned char checksum;
+  unsigned char xmitcsum;
+  int i;
+  int count;
+  int ch;
+
+  do
+    {
+      /* wait around for the start character, ignore all other characters */
+      while ((ch = getDebugChar()) != '$')
+	if (ch == -1)
+	  return 0;
+      checksum = 0;
+      xmitcsum = -1;
+
+      count = 0;
+
+      /* now, read until a # or end of buffer is found */
+      while (count < BUFMAX)
+	{
+	  ch = getDebugChar();
+	  if (ch == -1)
+	    return 0;
+	  if (ch == '#')
+	    break;
+	  checksum = checksum + ch;
+	  buffer[count] = ch;
+	  count = count + 1;
+	}
+      buffer[count] = 0;
+
+      if (ch == '#')
+	{
+	  ch = getDebugChar ();
+	  if (ch == -1)
+	    return 0;
+	  xmitcsum = hex(ch) << 4;
+	  ch = getDebugChar ();
+	  if (ch == -1)
+	    return 0;
+	  xmitcsum += hex(ch);
+	  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)
+	    {
+	      /* failed checksum */
+	      if (! putDebugChar('-'))
+		return 0;
+	    }
+	  else
+	    {
+	      /* successful transfer */
+	      if (! putDebugChar('+'))
+		return 0;
+	      /* if a sequence char is present, reply the sequence ID */
+	      if (buffer[2] == ':')
+		{
+		  if (! putDebugChar (buffer[0])
+		      || ! putDebugChar (buffer[1]))
+		    return 0;
+		  /* remove sequence chars from buffer */
+		  count = strlen(buffer);
+		  for (i=3; i <= count; i++)
+		    buffer[i-3] = buffer[i];
+		}
+	    }
+	}
+    }
+  while (checksum != xmitcsum);
+
+  return 1;
+}
+
+/* Send the packet in buffer.  Returns 0 on failure, non-zero on
+   success.  */
+
+static int
+putpacket (buffer)
+     char * buffer;
+{
+  unsigned char checksum;
+  int count;
+  int ch;
+
+  /*  $<packet info>#<checksum>. */
+  do
+    {
+      if (! putDebugChar('$'))
+	return 0;
+      checksum = 0;
+      count = 0;
+
+      while (ch=buffer[count])
+	{
+	  if (! putDebugChar(ch))
+	    return 0;
+	  checksum += ch;
+	  count += 1;
+	}
+
+      if (! putDebugChar('#')
+	  || ! putDebugChar(hexchars[checksum >> 4])
+	  || ! putDebugChar(hexchars[checksum % 16]))
+	return 0;
+
+      ch = getDebugChar ();
+      if (ch == -1)
+	return 0;
+    }
+  while (ch != '+');
+
+  return 1;
+}
+
+static char remcomInBuffer[BUFMAX];
+static char remcomOutBuffer[BUFMAX];
+static short error;
+
+static 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 volatile void (*mem_fault_routine)() = NULL;
+
+/* Indicate to caller of mem2hex or hex2mem that there has been an
+   error.  */
+static volatile int mem_err = 0;
+
+static 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).  */
+
+static int
+get_char (addr)
+     char *addr;
+{
+  return *addr;
+}
+
+static 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.  */
+
+static 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 */
+
+static 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.  */
+
+static 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           */
+/**********************************************/
+static int
+hexToInt(ptr, intValue)
+     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 processing for interfacing to gdb.
+   It is called whenever an exception occurs in the module being
+   debugged.  */
+
+static LONG
+handle_exception (T_StackFrame *old_frame)
+{
+  T_TSS_StackFrame *frame = (T_TSS_StackFrame *) old_frame;
+  int first = 0;
+  int sigval;
+  int addr, length;
+  char * ptr;
+  int newPC;
+
+  /* Apparently the bell can sometimes be ringing at this point, and
+     should be stopped.  */
+  StopBell ();
+
+  if (remote_debug)
+    {
+      ConsolePrintf ("vector=%d: %s, sr=0x%x, pc=0x%x, thread=%d\r\n",
+		     frame->ExceptionNumber,
+		     frame->ExceptionDescription,
+		     frame->ExceptionSystemFlags,
+		     frame->ExceptionEIP,
+		     GetThreadID ());
+    }
+
+  /* If the NLM just started, we record the module load information
+     and the thread ID, and set a breakpoint at the first instruction
+     in the program.  */
+  if (frame->ExceptionNumber == START_NLM_EVENT
+      && handle == NULL)
+    {
+      debugthread = GetThreadID ();
+      handle = (struct LoadDefinitionStructure *) frame->ExceptionErrorCode;
+      first_insn = *(char *) handle->LDInitializationProcedure;
+      *(unsigned char *) handle->LDInitializationProcedure = 0xcc;
+      return RETURN_TO_PROGRAM;
+    }
+
+  /* At the moment, we don't care about most of the unusual NetWare
+     exceptions.  */
+  if (frame->ExceptionNumber != TERMINATE_NLM_EVENT
+      && frame->ExceptionNumber > 31)
+    return RETURN_TO_PROGRAM;
+
+  /* Reset the initial breakpoint if necessary.  */
+  if (frame->ExceptionNumber == 3
+      && frame->ExceptionEIP == (LONG) handle->LDInitializationProcedure + 1
+      && *(unsigned char *) handle->LDInitializationProcedure == 0xcc)
+    {
+      *(char *) handle->LDInitializationProcedure = first_insn;
+      frame->ExceptionEIP = (LONG) handle->LDInitializationProcedure;
+      first = 1;
+    }
+
+  /* FIXME: How do we know that this exception has anything to do with
+     the program we are debugging?  We can check whether the PC is in
+     the range of the module we are debugging, but that doesn't help
+     much since an error could occur in a library routine.  */
+
+  frame_to_registers (frame, registers);
+
+  /* reply to host that an exception has occurred */
+  if (frame->ExceptionNumber == TERMINATE_NLM_EVENT)
+    {
+      /* There is no way to get the exit status.  */
+      remcomOutBuffer[0] = 'W';
+      remcomOutBuffer[1] = hexchars[0];
+      remcomOutBuffer[2] = hexchars[0];
+      remcomOutBuffer[3] = 0;
+    }
+  else
+    {
+      sigval = computeSignal (frame->ExceptionNumber);
+      remcomOutBuffer[0] = 'S';
+      remcomOutBuffer[1] =  hexchars[sigval >> 4];
+      remcomOutBuffer[2] =  hexchars[sigval % 16];
+      remcomOutBuffer[3] = 0;
+      if (first)
+	{
+	  remcomOutBuffer[0] = 'N';
+	  sprintf (remcomOutBuffer + 3, "0x%x;0x%x;0x%x",
+		   handle->LDCodeImageOffset,
+		   handle->LDDataImageOffset,
+		   handle->LDDataImageOffset + handle->LDDataImageLength);
+	}
+    }
+
+  if (! putpacket(remcomOutBuffer))
+    return RETURN_TO_NEXT_DEBUGGER;
+
+  if (frame->ExceptionNumber == TERMINATE_NLM_EVENT)
+    {
+      ResumeThread (mainthread);
+      return RETURN_TO_PROGRAM;
+    }
+
+  while (1)
+    {
+      error = 0;
+      remcomOutBuffer[0] = 0;
+      if (! getpacket (remcomInBuffer))
+	return RETURN_TO_NEXT_DEBUGGER;
+      talking = 1;
+      switch (remcomInBuffer[0])
+	{
+	case '?':
+	  sigval = computeSignal (frame->ExceptionNumber);
+	  remcomOutBuffer[0] = 'S';
+	  remcomOutBuffer[1] =  hexchars[sigval >> 4];
+	  remcomOutBuffer[2] =  hexchars[sigval % 16];
+	  remcomOutBuffer[3] = 0;
+	  if (first)
+	    {
+	      remcomOutBuffer[0] = 'N';
+	      sprintf (remcomOutBuffer + 3, "0x%x;0x%x;0x%x",
+		       handle->LDCodeImageOffset,
+		       handle->LDDataImageOffset,
+		       (handle->LDDataImageOffset
+			+ handle->LDDataImageLength));
+	    }
+	  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 'm':
+	  /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
+	  /* 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;
+
+	case 'M':
+	  /* MAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK */
+	  /* 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;
+
+	case 'c':
+	case 's':
+	  /* cAA..AA    Continue at address AA..AA(optional) */
+	  /* sAA..AA   Step one instruction from AA..AA(optional) */
+	  /* 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;
+
+	  registers_to_frame (registers, frame);
+	  return RETURN_TO_PROGRAM;
+
+	case 'k':
+	  /* kill the program */
+	  KillMe (handle);
+	  ResumeThread (mainthread);
+	  return RETURN_TO_PROGRAM;
+	}
+
+      /* reply to the request */
+      if (! putpacket(remcomOutBuffer))
+	return RETURN_TO_NEXT_DEBUGGER;
+    }
+}
+
+/* Start up.  The main thread opens the named serial I/O port, loads
+   the named NLM module and then goes to sleep.  The serial I/O port
+   is named as a board number and a port number.  It would be more DOS
+   like to provide a menu of available serial ports, but I don't want
+   to have to figure out how to do that.  */
+
+int
+main (argc, argv)
+     int argc;
+     char **argv;
+{
+  int hardware, board, port;
+  LONG err;
+  struct debuggerStructure s;
+  char *cmdlin;
+  int i;
+
+  /* Create a screen for the debugger.  */
+  console_screen = CreateScreen ("System Console", 0);
+  if (DisplayScreen (console_screen) != ESUCCESS)
+    fprintf (stderr, "DisplayScreen failed\n");
+
+  if (argc < 4)
+    {
+      fprintf (stderr,
+	       "Usage: load gdbserver board port program [arguments]\n");
+      exit (1);
+    }
+
+  hardware = -1;
+  board = strtol (argv[1], (char **) NULL, 0);
+  port = strtol (argv[2], (char **) NULL, 0);
+
+  err = AIOAcquirePort (&hardware, &board, &port, &AIOhandle);
+  if (err != AIO_SUCCESS)
+    {
+      switch (err)
+	{
+	case AIO_PORT_NOT_AVAILABLE:
+	  fprintf (stderr, "Port not available\n");
+	  break;
+
+	case AIO_BOARD_NUMBER_INVALID:
+	case AIO_PORT_NUMBER_INVALID:
+	  fprintf (stderr, "No such port\n");
+	  break;
+
+	default:
+	  fprintf (stderr, "Could not open port: %d\n", err);
+	  break;
+	}
+
+      exit (1);
+    }
+
+  err = AIOConfigurePort (AIOhandle, AIO_BAUD_9600, AIO_DATA_BITS_8,
+			  AIO_STOP_BITS_1, AIO_PARITY_NONE,
+			  AIO_HARDWARE_FLOW_CONTROL_OFF);
+  if (err != AIO_SUCCESS)
+    {
+      fprintf (stderr, "Could not configure port: %d\n", err);
+      AIOReleasePort (AIOhandle);
+      exit (1);
+    }
+
+  /* Register ourselves as an alternate debugger.  */
+  memset (&s, 0, sizeof s);
+  s.DDSResourceTag = ((struct ResourceTagStructure *)
+		      AllocateResourceTag (GetNLMHandle (),
+					   "gdbserver",
+					   DebuggerSignature));
+  if (s.DDSResourceTag == 0)
+    {
+      fprintf (stderr, "AllocateResourceTag failed\n");
+      AIOReleasePort (AIOhandle);
+      exit (1);
+    }
+  s.DDSdebuggerEntry = handle_exception;
+  s.DDSFlags = TSS_FRAME_BIT;
+
+  err = RegisterDebuggerRTag (&s, AT_FIRST);
+  if (err != 0)
+    {
+      fprintf (stderr, "RegisterDebuggerRTag failed\n");
+      AIOReleasePort (AIOhandle);
+      exit (1);
+    }
+
+  /* Get the command line we were invoked with, and advance it past
+     our name and the board and port arguments.  */
+  cmdlin = getcmd ((char *) NULL);
+  for (i = 0; i < 2; i++)
+    {
+      while (! isspace (*cmdlin))
+	++cmdlin;
+      while (isspace (*cmdlin))
+	++cmdlin;
+    }
+  
+  /* In case GDB is started before us, ack any packets (presumably
+     "$?#xx") sitting there.  */
+  if (! putDebugChar ('+'))
+    {
+      fprintf (stderr, "putDebugChar failed\n");
+      UnRegisterDebugger (&s);
+      AIOReleasePort (AIOhandle);
+      exit (1);
+    }
+
+  mainthread = GetThreadID ();
+  handle = NULL;
+  talking = 0;
+
+  if (remote_debug > 0)
+    ConsolePrintf ("About to call LoadModule with \"%s\" %d %d\r\n",
+		   cmdlin, console_screen, __GetScreenID (console_screen));
+
+  /* Start up the module to be debugged.  */
+  err = LoadModule ((struct ScreenStruct *) __GetScreenID (console_screen),
+		    cmdlin, LO_DEBUG);
+  if (err != 0)
+    {
+      fprintf (stderr, "LoadModule failed: %d\n", err);
+      UnRegisterDebugger (&s);
+      AIOReleasePort (AIOhandle);
+      exit (1);
+    }
+
+  /* By the time we reach this point in the code the debugger thread
+     should have received a START_NLM_EVENT and gone to sleep.  */
+  if (remote_debug > 0)
+    ConsolePrintf ("Resuming %d, suspending %d\r\n", debugthread, mainthread);
+  ResumeThread (debugthread);
+  SuspendThread (mainthread);
+
+  /* If we are woken up, print an optional error message, deregister
+     ourselves and exit.  */
+  if (error_message != NULL)
+    fprintf (stderr, "%s\n", error_message);
+  UnRegisterDebugger (&s);
+  AIOReleasePort (AIOhandle);
+  exit (0);
+}