Question

Should be written in Python:

A disassembler takes a machine code file (binary) and converts it back into assembly code. Disassemblers are a key tool in the software reverse engineering process because it allows you to go from the raw binary all the way back to the original source code, if desired. For this assignment you will be given 8 32-bit binary strings and the type of the instruction (I-type, R-type, or J-type). You’ll write a basic disassembler in Python that splits the 32-bit string into its corresponding fields, converts them from binary into their string representation, then reorders the fields, resulting in the original assembly code instruction. Here’s an example:

Here are the 8 machine code instructions to disassemble (it’s fine to hard-code them into your program):

1. instr1 = 00000001101011100101100000100100 (R-type)

2. instr2 = 10001101010010010000000000001000 (I-type)

3. instr3 = 00001000000000010010001101000101 (J-type)

4. instr4 = 00000010101010010101100000100010 (R-type)

5. instr5 = 00000011111000000000000000001000 (R-type)

6. instr6 = 00110101111100001011111011101111 (I-type)

7. instr7 = 10101110100011010000000000100000 (I-type)

8. instr8 = 00000010110011010101000000100000 (R-type)

Answer 1

Hi!

This is an interesting question. You will need to add more opcodes in Dictionary for it to work with other.

Code:

Nm instructions = || #List to store all functions instructions.append("00000001101011100101100000100100 R"), instructions.append("10001101010010010000000000001000 I") instructions.append("00001000000000010010001101000101 J"), instructions.append("00000010101010010101100000100010 R"), instructions.append("00000011111000000000000000001000 R"), instructions.append("00110101111100001011111011101111 I"), instructions.append("10101110100011010000000000100000 I"), instructions.append("00000010110011010101000000100000 R"), 7 10 11 12 14 15 #Dictionary to store opcodes opcodeDict = {'100011':'Lw', '000010':'j', '001101':'ORI', '101011':'SW', '100100':'AND', '100010':'SUB', '100000':'ADD', '001000': 'JR'} for i in instructions: instr, typeI = i.split() #type of instruction part is sepearted from the strings if(typeI=='R'): opcode = instr[0:6] #store first 6 digits to find opcode rs = instr[6:11] rt = instr[11:16] rd = instr[16:21] shamt = instr[21:26] func = instr[26:] if(opcodeDict[func]!='JR'): print("{}\tR{}\tr{}\tr{}\n". format (opcodeDict[func], int(rs,2), int(rt,2), int(rd, 2))), else: print("{}\tr{}\n".Format(opcodeDict[func], int(rs, 2))) if(typeI=='1'): opcode = instr[0:6] #store first 6 digits to find opcode rs = instr[6:11] rt = instr[11:16] im = instr[16:] if(opcodeDict[opcode][-1)=='1'): print("{}\t{}\t{}\t#{}\n".format(opcodeDict[opcode], int(rs,2), int(rt,2), int(im, 2))) else: print("{}\t{}\t{}(R{})\n".format(opcodeDict[opcode], int(rs,2),int(im,2), int(rt, 2))) if(typeI==')'): opcode = instr[0:6] #store first 6 digits to find opcode address = instr[6:] print("{}\t{}\n".format(opcodeDict[opcode], hex(int(address, 2)))) 38

Code that you can copy: (Take care of Indentation)

file.py

instructions = [] #List to store all functions instructions.append("00000001101011100101100000100100 R") instructions.append("10001101010010010000000000001000 I") instructions.append("00001000000000010010001101000101 J") instructions.append("00000010101010010101100000100010 R") instructions.append("00000011111000000000000000001000 R") instructions.append("00110101111100001011111011101111 I") instructions.append("10101110100011010000000000100000 I") instructions.append("00000010110011010101000000100000 R") #Dictionary to store opcodes opcodeDict = {'100011':'LW','000010':'J','001101':'ORI','101011':'SW','100100':'AND','100010':'SUB','100000':'ADD','001000':'JR'} for i in instructions:     instr,typeI = i.split() #type of instruction part is sepearted from the strings     if(typeI=='R'):         opcode = instr[0:6] #store first 6 digits to find opcode         rs = instr[6:11]         rt = instr[11:16]         rd = instr[16:21]         shamt = instr[21:26]         func = instr[26:]         if(opcodeDict[func]!='JR'):             print("{}\tR{}\tR{}\tR{}\n".format(opcodeDict[func],int(rs,2),int(rt,2),int(rd,2)))         else:             print("{}\tR{}\n".format(opcodeDict[func],int(rs,2)))     if(typeI=='I'):         opcode = instr[0:6] #store first 6 digits to find opcode         rs = instr[6:11]         rt = instr[11:16]         im = instr[16:]         if(opcodeDict[opcode][-1]=='I'):             print("{}\t{}\t{}\t#{}\n".format(opcodeDict[opcode],int(rs,2),int(rt,2),int(im,2)))         else:             print("{}\t{}\t{}(R{})\n".format(opcodeDict[opcode],int(rs,2),int(im,2),int(rt,2)))     if(typeI=='J'):         opcode = instr[0:6] #store first 6 digits to find opcode         address = instr[6:]         print("{}\t{}\n".format(opcodeDict[opcode],hex(int(address,2))))

Output:

AND R14 R11 R13 10 LW 8(R9) 0x12345 SUB R21 R9 R11 JR R31 16 #48879 ORI SW ADD 15 20 R22 32(R13) R13 R10

if you liked the answer, do give feedback.

Comment for help.