Disassembling

Disassembling in rizin is just a way to represent an array of bytes. It is handled as a special print mode within p command.

In the old times, when the rizin core was smaller, the disassembler was handled by an external rsc file. That is, rizin first dumped current block into a file, and then simply called objdump configured to disassemble for Intel, ARM or other supported architectures.

It was a working and unix friendly solution, but it was inefficient as it repeated the same expensive actions over and over, because there were no caches. As a result, scrolling was terribly slow.

So there was a need to create a generic disassembler library to support multiple plugins for different architectures. We can list the current loaded plugins with

$ rz-asm -L

Or from inside rizin:

> e asm.arch=??

This was many years before capstone appeared. So rizin was using udis86 and olly disassemblers, many gnu (from binutils).

Nowadays, the disassembler support is one of the basic features of rizin. It now has many options, endianness, including target architecture flavor and disassembler variants, among other things.

To see the disassembly, use the pd command. It accepts a numeric argument to specify how many opcodes of current block you want to see. Most of the commands in rizin consider the current block size as the default limit for data input. If you want to disassemble more bytes, set a new block size using the b command.

[0x00000000]> b 100    ; set block size to 100
[0x00000000]> pd       ; disassemble 100 bytes
[0x00000000]> pd 3     ; disassemble 3 opcodes
[0x00000000]> pD 30    ; disassemble 30 bytes

You can also pass negative numbers as the numeric argument, if you want to disassemble something that lies before the current offset:

[0x00005bc0]> pd -2
            0x00005bb8      ret
            0x00005bb9      nop dword [rax]
[0x00005bc0]> pd 2
            ;-- entry.fini0:
            0x00005bc0      endbr64
            0x00005bc4      cmp byte [0x000232c8], 0

The pD command works like pd but accepts the number of input bytes as its argument, instead of the number of opcodes.

You can also get information about the pointer chains using the command pdp. This can be helpful while dealing with ROP chains.

The "pseudo" syntax may be somewhat easier for a human to understand than the default assembler notations. But it can become annoying if you read lots of code. To play with it:

[0x00405e1c]> e asm.pseudo=true
[0x00405e1c]> pd 3
		  ; JMP XREF from 0x00405dfa (fcn.00404531)
		  0x00405e1c    488b9424a80. rdx = [rsp+0x2a8]
		  0x00405e24    64483314252. rdx ^= [fs:0x28]
		  0x00405e2d    4889d8       rax = rbx

[0x00405e1c]> e asm.syntax=intel
[0x00405e1c]> pd 3
		  ; JMP XREF from 0x00405dfa (fcn.00404531)
		  0x00405e1c    488b9424a80. mov rdx, [rsp+0x2a8]
		  0x00405e24    64483314252. xor rdx, [fs:0x28]
		  0x00405e2d    4889d8       mov rax, rbx

[0x00405e1c]> e asm.syntax=att
[0x00405e1c]> pd 3
		  ; JMP XREF from 0x00405dfa (fcn.00404531)
		  0x00405e1c    488b9424a80. mov 0x2a8(%rsp), %rdx
		  0x00405e24    64483314252. xor %fs:0x28, %rdx
		  0x00405e2d    4889d8       mov %rbx, %rax

And as always, you can print the disassembly in JSON using pdj and get more information about the other associated commands by running pd?.