disc.cpp

Decompilation Dos Program is a technique that allows you to recover lost source code. It is also nee

/*---------------------------------------------------------------------------*/
// DisC Decompilation Wizard
// written by
// Satish Kumar S
// [e-mail]
//
// Copyright 1999-2001 Satish Kumar S
//
// Permission is granted to use this software for research purposes as
// long as this notice stays attached to this software.
/*---------------------------------------------------------------------------*/
#include <dos.h>
#include <stdio.h>
#include <conio.h>
#include "Program.h"
#include "Disasm.h"
#include "TcWizard.h"
#include "LibWiz.h"

VariableList GlobalVars;		// List of known global variables.
VariableList LocalVars;			// List of known local variables.
StringList   ErrorList;			// List of errors encountered
					//  while traversing thro' the code.
char errorStr[256];			// Global temp. string for errors.

void SetRegisterVariable(char *RegName)
{
  int W,Reg;
  for(W=0;W<2;W++)
    for(Reg=0;Reg<8;Reg++)
      if (strcmp(Regstr[W][Reg],RegName)==0)
      {
	Variable v;
	v.Operand=REG_DIRECT;
	v.Data1=W*8+Reg;
	v.Data2=0;
	GlobalVars.Add(v,VAR_REGISTER,0);
	return;
      }
}
/*
[-----------------------------------------------------------------------]
[ RegisterVariable							]
[-----------------------------------------------------------------------]
[ Returns 1 if the register passed is used as a register variable.	]
[-----------------------------------------------------------------------]
*/
int RegisterVariable(int whichReg)
{
  Variable v;
  v.Operand=REG_DIRECT;
  v.Data1=whichReg;
  v.Data2=0;
  if (GlobalVars.IsPresent(v))
    return 1;
  return 0;
}

char *GetRegVarName(int whichReg)
{
  Variable v;
  v.Operand=REG_DIRECT;
  v.Data1=whichReg;
  char *t=GlobalVars.GetName(v);
  if (t) return t;
  static char t1[10];
  t1[0]='_'; strcpy(t1+1,Regstr[whichReg/8][whichReg%8]);
  return t1;
}
void DisplayErrors()
{
  StringList *ptr = &ErrorList;
  while(ptr && ptr->Data)
  {
    puts(ptr->Data);
    ptr=ptr->Next;
  }
  ErrorList.Flush();
  getch();
}

//#define TESTING
#ifdef TESTING
main()
{
  int n;
  Disasm dasm;
  do
  {
    printf("Enter the bytes : ");
    fflush(stdin);
    char str[30];
    gets(str);
    int index=0;
    Byte Insts[10];
    for(int n=0;;n++)
    {
      int x,ok;
      ok = sscanf(str+index,"%2x",&x);
      if (!ok) break;
      Insts[n]=x;
      index+=3;
    }
    if (!n) break;
    String Instruction = dasm.GetAsm(Insts,n);
    puts((char *)Instruction);
  }while(1);
  return 0;
}
#else
main(int argc,char *argv[])
{
  Program prog;
  char *ExeName=(argc>1)?argv[1]:"TMP.EXE";
  if (prog.Load(ExeName)!=0)
  {
    printf("Unable to load executable %s.",ExeName);
    return 0;
  }

  Byte far *ProgAddr = prog.GetCodePtr();
  TcWizard w(ProgAddr,prog.GetCodeSize());
  Byte far *MainAddr = w.GetMain();
  if (MainAddr)
  {
    Variable v;
    v.Operand=IMMEDIATE;
    v.Data1=FP_OFF(MainAddr);
    v.Data2=FP_SEG(MainAddr);
    GlobalVars.Add(v,VAR_USER_FUNCTION,0,"main");
  }
  int endwhile=0;
  clrscr();

  printf("Globals:-\n"); GlobalVars.Display();

  while(!endwhile)
  {
    DisplayErrors();
    printf("\t\t'D'isassembly\n");
    printf("\t\tdis'C'\n");
    printf("\t\t'R'egister variables\n");
    printf("\t\tcompare in 'L'ibrary\n");
    printf("\t\t'A'dd to variable list\n");
    printf("\t\t'G'lobal variables display\n");
    printf("\t\t'F'ull decompilation\n");
    switch(getch())
    {
      case 'g' : case 'G' :
	  GlobalVars.Display(); break;
      case 'a' : case 'A' :
	  printf("Local or global variable(L/G)?\n");
	  switch(getch())
	  {
	    case 'l' : case 'L' :
		int addr,type;
		Variable v;
		int size;
		char varstr[10];
		while(1)
		{
		  printf("Enter the variable's address : ");
		  gets(varstr);
		  if (!varstr[0]) break;
		  addr=atoi(varstr+2);
		  printf("Enter the variable type\n");
		  printf("(1-char, 2-int, 3-long)");
		  scanf("%d",&type);
		  v.Operand=INDEXED_WORD;
		  v.Data1=INDX_BP;
		  v.Data2=addr;
		  size=1<<(type-1);
		  LocalVars.Add(v,type,size);
		  fflush(stdin);
		}
		break;
	    case 'g' : case 'G' :
		printf("Enter the variable's address : ");
		scanf("%X",&addr);
		printf("Enter the variable type\n");
		printf("(1-char, 2-int, 3-long)");
		scanf("%d",&type);
		v.Operand=MEMORY;
		v.Data1=addr;
		size=1<<(type-1);
		GlobalVars.Add(v,type,size);
		fflush(stdin);
		break;
	  }
	  break;
      case 'l' : case 'L' :
	  printf("Function address please : ");
	  long addr;
	  scanf("%lX",&addr);
	  if (addr==0) break;
	  printf("Enter the library file name : ");
	  char LibFileName[80];
	  scanf("%s",LibFileName);

	  Byte far *pa;
	  if (addr<(long)65536) pa = (Byte far *)MK_FP(FP_SEG(ProgAddr),(unsigned)addr);
	  else pa=(Byte far *)addr;
	  TLibWizard tlw;
	  char pname[64];
	  int percent;
	  if (tlw.CheckInLibrary(LibFileName,1,&pa,pname,&percent)==0)
	  {
	    printf("\nMatched with %s at %d.%d%%\n",pname,percent/10,percent%10);
	    Variable v;
	    v.Operand=IMMEDIATE;
	    v.Data1=FP_OFF(pa);
	    v.Data2=FP_SEG(pa);
	    if (percent>950) GlobalVars.Add(v,VAR_LIB_FUNCTION,0,pname);
	  }
	  else
	    printf("\nUnable to load %s\n",LibFileName);
	  break;
      case 'd' : case 'D' :
	  printf("Enter the address : ");
	  Dword funcaddr;
	  scanf("%lX",&funcaddr);
	  if (funcaddr==0) break;
	  Word seg=FP_SEG(ProgAddr),off;
	  off=(Word)funcaddr;
	  if (funcaddr>off) seg=funcaddr>>16;
	  Disasm d;
	  d.SetCodePtr(ProgAddr);
	  d.SetregIP((Byte far *)MK_FP(seg,off) - ProgAddr);
	  do
	  {
	    d.DispPage(10);
	  }while(getch()!=27);
	  break;
      case 'r' : case 'R' :
	  do
	  {
	    puts("Give the register name");
	    char regname[10];
	    fflush(stdin); gets(regname);
	    if (!regname[0]) break;
	    strupr(regname);
	    SetRegisterVariable(regname);
	  }while(1);
	  GlobalVars.NameUnknownVariables();
	  break;
      case 'f' : case 'F' :
	  w.DeCompileFull();
	  break;
      case 'c' : case 'C' :
	  printf("Enter the function address : ");
	  scanf("%lX",&funcaddr);
	  if (funcaddr==0) break;
	  seg=FP_SEG(ProgAddr);
	  off=(Word)funcaddr;
	  if (funcaddr>off) seg=funcaddr>>16;
	  // Initialize info about the procedure.
	  Byte far *ProcAddr=(Byte far *)MK_FP(seg,off);
	  printf("Recurse all(Y/N)?");
	  int recurse=(getch()=='y');
	  w.Pass1(ProcAddr,recurse);
	  w.Flush();
	  clrscr();
	  LocalVars.NameUnknownVariables();
	  printf("Locals:-\n"); LocalVars.Display();
	  DisplayErrors();
	  LocalVars.MakeAllReadOnly();
	  w.DisplayProc(ProcAddr);
	  LocalVars.Flush();
	  break;
      default : endwhile=1; break;
    }
  }
  return 0;
}
#endif