How to write and execute PURE machine code manually without containers like EXE or ELF?

I just need a hello world demo to see how machine code actually works.

Though windows' EXE and linux' ELF is near machine code,but it's not PURE

How can I write/execute PURE machine code?

Solution 1:

You can write in PURE machine code manually WITHOUT ASSEMBLY

Linux/ELF: https://github.com/XlogicX/m2elf. This is still a work in progress, I just started working on this yesterday.

Source file for "Hello World" would look like this:

b8    21 0a 00 00   #moving "!\n" into eax
a3    0c 10 00 06   #moving eax into first memory location
b8    6f 72 6c 64   #moving "orld" into eax
a3    08 10 00 06   #moving eax into next memory location
b8    6f 2c 20 57   #moving "o, W" into eax
a3    04 10 00 06   #moving eax into next memory location
b8    48 65 6c 6c   #moving "Hell" into eax
a3    00 10 00 06   #moving eax into next memory location
b9    00 10 00 06   #moving pointer to start of memory location into ecx
ba    10 00 00 00   #moving string size into edx
bb    01 00 00 00   #moving "stdout" number to ebx
b8    04 00 00 00   #moving "print out" syscall number to eax
cd    80            #calling the linux kernel to execute our print to stdout
b8    01 00 00 00   #moving "sys_exit" call number to eax
cd    80            #executing it via linux sys_call

WIN/MZ/PE:

shellcode2exe.py (takes asciihex shellcode and creates a legit MZ PE exe file) script location:

https://web.archive.org/web/20140725045200/http://zeltser.com/reverse-malware/shellcode2exe.py.txt

dependency:

https://github.com/radare/toys/tree/master/InlineEgg

extract

python setup.py build




sudo python setup.py install

Solution 2:

Everyone knows that the application we usually wrote is run on the operating system. And managed by it.

It means that the operating system is run on the machine. So I think that is PURE machine code which you said.

So, you need to study how an operating system works.

Here is some NASM assembly code for a boot sector which can print "Hello world" in PURE.

 org
   xor ax, ax
   mov ds, ax
   mov si, msg
boot_loop:lodsb
   or al, al 
   jz go_flag   
   mov ah, 0x0E
   int 0x10
   jmp boot_loop

go_flag:
   jmp go_flag

msg   db 'hello world', 13, 10, 0

   times 510-($-$$) db 0
   db 0x55
   db 0xAA

And you can find more resources here: http://wiki.osdev.org/Main_Page.

END.

If you had installed nasm and had a floppy, You can

nasm boot.asm -f bin -o boot.bin
dd if=boot.bin of=/dev/fd0

Then, you can boot from this floppy and you will see the message. (NOTE: you should make the first boot of your computer the floppy.)

In fact, I suggest you run that code in full virtual machine, like: bochs, virtualbox etc. Because it is hard to find a machines with a floppy.

So, the steps are First, you should need to install a full virtual machine. Second, create a visual floppy by commend: bximage Third, write bin file to that visual floppy. Last, start your visual machine from that visual floppy.

NOTE: In https://wiki.osdev.org , there are some basic information about that topic.

How to write and execute PURE machine code manually without containers like EXE or ELF?

Solution 1:

Solution 2:

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