[surki]

Doing it in C with mixed assembly

  [surki@linux-vrse tt]$ cat | gcc -nostdlib -x c - -o helloworld
  #define SYS_exit  1
  #define SYS_write 4
  #define stdout    1
  
  int strlen(const char *str)
  {
    long len = 0;
    while (str && *str++)
    {
        len++;
    }
  
    return len;
  }
  
  
  void print(const char *str) 
  {
      int len = strlen(str);
  
      long ret;
  
      /* Can't touch ebx directly, PIC uses it */
      __asm__ __volatile__ ("pushl %%ebx\n"
                            "movl  %%esi, %%ebx\n"
                            "int   $0x80\n;"
                            "popl  %%ebx"
                            
                            "a" (SYS_write),
                              "S" ((long) stdout),
                              "c" ((long) str),
                              "d" ((long) len));
      return;
  }
  
  void _start()
  {
    main();
  
    __asm__ __volatile__ (
         "xorl %%ebx, %%ebx\n"
         "int $0x80\n"
         
         "a" (SYS_exit));
  }
  
  int main()
  {
    print("Hello World\n");
    return 0;
  }

  [surki@linux-vrse tt]$ strip -R .comment -R .comment.SUSE.OPTs -R .note.gnu.build-id helloworld
  [surki@linux-vrse tt]$ ll helloworld 
  -rwxr-xr-x 1 suresh users 540 2010-07-21 13:19 helloworld
  
  [surki@linux-vrse tt]$ ./helloworld 
  Hello World