Simple Disassembler & Assembler for Yan85

This is a simple disassembler/assembler for yan85 that could be used in pwn.college challenges, the scripts are not perfect.

Yan85 has 3 bytes op, arg1, arg2

Registers

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Register	Descriptio
a	General purpose register
b	General purpose register
c	General purpose register
d	General purpose register
s	Stack Pointer
i	Instruction pointer
f	Flags register

Instructions

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Register	Descriptio	Example
imm	Moves a byte to a register	imm a 0x41
add	Adds two registers	add a b
stk	Stack instruction deals with push and pop	stk a 0 (pop)
stm	Set a memory value in a register	stm *c a
ldm	Load value of memory into a register	ldm c *a
cmp	Compares two registers	cmp a b
jmp	Jump instruction	jmp 0x10 a
sys	Execute syscalls	sys 0x10 a

• stk
  • to push arg1=0 arg2=reg
  • to pop arg2=reg arg2=0

Syscalls

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Register	Descriptio
open	open syscall
read code	Write into memory space
read memory	will pass the offset of what part in memory to write to
write	write bytes from the buffer pointed to by buf to the file associated with the open file descriptor, fildes
sleep	Delay for seconds
exit	terminate the function currently running

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For more details you can read this Manual