#  _    _                           ____      _               _   _   _
    # | |  | |                         |  _ \    | |             | | | | | |
    # | |__| | __ _ _ __  _ __  _   _  | |_) | __| | __ _ _   _  | | | | | |
    # |  __  |/ _` | '_ \| '_ \| | | | |  _ < / _` |/ _` | | | | | | | | | |
    # | |  | | (_| | |_) | |_) | |_| | | |_) | (_| | (_| | |_| | |_| |_| |_|
    # |_|  |_|\__,_| .__/| .__/ \__, | |____/ \__,_|\__,_|\__, | (_) (_) (_)
    #              | |   | |     __/ |                     __/ |
    #              |_|   |_|    |___/                     |___/
    #
    #
    #
    # char z3f_bday_shellcode[] =
    # "\xeb\x12\x59\x48\x31\xc0\x48\x31"
    # "\xdb\x48\x31\xd2\xb0\x04\xfe\xc3"
    # "\xb2\x19\xcd\x80\xe8\xe9\xff\xff"
    # "\xff\x7c\x2d\x7c\x34\x70\x70\x59"
    # "\x20\x62\x2d\x44\x40\x79\x20\x5a"
    # "\x43\x46\x20\x3d\x44\x20\x21\x21"
    # "\x21\x0a";
    #
    # $ gcc -c z3f_bday.s
    # $ objdump -d ./z3f_bday.o
    # Disassembly of section .text:
    # 0000000000000000 <main>:
    #    0:   eb 12                   jmp    14 <happy>
    # 0000000000000002 <birthday>:
    #    2:   59                      pop    %rcx
    #    3:   48 31 c0                xor    %rax,%rax
    #    6:   48 31 db                xor    %rbx,%rbx
    #    9:   48 31 d2                xor    %rdx,%rdx
    #    c:   b0 04                   mov    $0x4,%al
    #    e:   fe c3                   inc    %bl
    #   10:   b2 00                   mov    $0x0,%dl
    #   12:   cd 80                   int    $0x80
    # 0000000000000014 <happy>:
    #   14:   e8 e9 ff ff ff          callq  2 <birthday>
    # 0000000000000019 <CAKE>:
    #   19:   7c 2d                   jl     48 <CAKE+0x2f>
    #   1b:   7c 34                   jl     51 <CAKE+0x38>
    #   1d:   70 70                   jo     8f <CAKE+0x76>
    #   1f:   59                      pop    %rcx
    #   20:   20 62 2d                and    %ah,0x2d(%rdx)
    #   23:   44                      rex.R
    #   24:   40 79 20                rex jns 47 <CAKE+0x2e>
    #   27:   48                      rex.W
    #   28:   4b                      rex.WXB
    #   29:   4d 20 3d 44 20 21 21    rex.WRB and %r15b,0x21212044(%rip)        # 21212074 <CAKE+0x2121205b>
    #   30:   21 0a                   and    %ecx,(%rdx)
    #
    # $ gcc z3f_bday.o -o z3f_bday
    # $ ./z3f_bday
    #
    #

    .section .text
    .globl main
    main:
            jmp     happy

    birthday:
            pop     %rcx
            xorq    %rax, %rax
            xorq    %rbx, %rbx
            xorq    %rdx, %rdx
            movb    $4, %al
            incb    %bl
            movb    $CAKESIZE, %dl
            int     $0x80

    happy:
            call    birthday

    CAKE:
    .byte   0x7c,0x2d,0x7c,0x34,0x70,0x70,0x59,0x20
    .byte   0x62,0x2d,0x44,0x40,0x79,0x20,0x5a,0x33
    .byte   0x46,0x20,0x3d,0x44,0x20,0x21,0x21,0x21
    .byte   0x0a

    CAKESIZE = . - CAKE