#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#define PUSH 0x50
#define POP  0x58
#define MOV  0xB8
#define NOP  0x90
#define ADD  0x01
#define AND  0x21
#define XOR  0x31
#define OR   0x09
#define SBB  0x19
#define SUB  0x29
#define JUNK asm __volatile__(".byte 0x50, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x58")
#define JUNKLEN 8
unsigned char *code;
int codelen;
const unsigned char prefixes[] = { ADD,AND,XOR,OR,SBB,SUB,0 };
void readcode(const char *filename) {
  FILE *fp = fopen(filename, "rb");    JUNK;
  fseek(fp, 0L, SEEK_END);             JUNK;
  codelen = ftell(fp);
  code = malloc(codelen);              JUNK;
  fseek(fp, 0L, SEEK_SET);
  fread(code, codelen, 1, fp);         JUNK;
}

void writecode(const char *filename) {
  int fd;
  int lastoffset = strlen(filename)-1;
  char lastchar = filename[lastoffset];
  char *newfilename = strdup(filename);  JUNK;
  lastchar = '0'+(isdigit(lastchar)?(lastchar-'0'+1)%10:0);
  newfilename[lastoffset] = lastchar;
  fd = open(newfilename, O_WRONLY | O_CREAT,0777 );         JUNK;
  write(fd,code,codelen);
  close(fd);
  free(newfilename);
}
int writeinstruction(unsigned reg, int offset, int space) {
  if (space < 2) {
    code[offset] = NOP;                         JUNK;
    return 1;
  }
  else if (space < 5 || rand()%2 == 0) {
    code[offset] = prefixes[rand()%6];          JUNK;
    code[offset+1] = 0xC0 + rand()%8*8 + reg;   JUNK;
    return 2;
  }
  else {
    code[offset] = MOV+reg;                     JUNK;
    *(short*)(code+offset+1) = rand();
    *(short*)(code+offset+3) = rand();          JUNK;
    return 5;
  }
}
int readinstruction(unsigned reg, int offset) {
  unsigned c1 = code[offset];
  if (c1 == NOP)
    return 1;                     JUNK;
  if (c1 == MOV+reg)
    return 5;                     JUNK;
  if (strchr(prefixes,c1)) {
    unsigned c2 = code[offset+1]; JUNK;
    if (c2 >= 0xC0 && c2 <= 0xFF && (c2&7) == reg)
      return 2;                   JUNK;
  }                               JUNK;
  return 0;
}

void replacejunk(void) {
  int i, j, inc, space;
  srand(time(NULL));                                 JUNK;

  for (i = 0; i < codelen-JUNKLEN-2; i++) {
    unsigned start = code[i];
    unsigned end = code[i+JUNKLEN+1];
    unsigned reg = start-PUSH;

    if (start < PUSH || start >= PUSH+8) continue;   JUNK;
    if (end != POP+reg) continue;                    JUNK;
if (reg == 4) continue; /* register 4 is ESP */
j = 0;                                           JUNK;
    while (inc = readinstruction(reg,i+1+j)) j += inc;
    if (j != JUNKLEN) continue;                      JUNK;
reg = rand()%7;                                  JUNK;
    reg += (reg >= 4);
    code[i] = PUSH+reg;                              JUNK;
    code[i+JUNKLEN+1] = POP+reg;                     JUNK;
space = JUNKLEN;
    j = 0;                                           JUNK;
    while (space) {
      inc = writeinstruction(reg,i+1+j,space);       JUNK;
      j += inc;
      space -= inc;                                  JUNK;
    }
 printf("%d\n",i);                                JUNK;
  }
}                                                                             
int main(int argc, char* argv[]) {

  readcode(argv[0]);     JUNK;
  replacejunk();         JUNK;
  writecode(argv[0]);    JUNK;

  return 0;
}