[c-prog] Execute Disable Bit

[Pedro Izecksohn]

Could you post your results?

#include <stdio.h>
#include <stdlib.h>

_Bool xdb () {
unsigned int d;

__asm__("cpuid":"=d"(d):"a"(0x80000001):"%ebx","%ecx");

return ((d&0x100000)==0x100000);
}

char * code = "\xC3"; // ret

char buffer;

int main (int argc, char ** argv) {

  void (*function)();
  char opcode;

  if (!xdb()) {printf ("This CPU does not have Execute Disable
Bit.\n"); return EXIT_SUCCESS;}

  buffer=*code;
  function = (void(*)())&buffer;
  printf ("I\'ll try to call buffer located at %p.\n",function);
  function();
  printf ("Succeeded.\n");

  if (NULL==(function=malloc(1))) {perror(NULL); return EXIT_FAILURE;}
  *(char*)function = *code;
  printf ("I\'ll try to call malloced mem located at %p.\n",function);
  function();
  printf ("Succeeded.\n");

  opcode = *code;
  function = (void(*)())&opcode;
  printf ("I\'ll try to call stacked code located at %p.\n",function);
  function();
  printf ("Succeeded.\n");

  printf ("Enter to exit.");
  getchar();

  return EXIT_SUCCESS;
}