1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
|
#!/usr/bin/env python3
"""
Disassembler for nandgame.
Using my own flavor of assembly language.
I don't like the "C-style" one nandgame introduces.
"""
import sys
ZERO = "#0"
DEST_NONE = "_"
JUMP_NONE = ""
JUMPS_IF_NZERO = ["jgt", "jlt", "jne", "jmp"]
JUMPS_IF_ZERO = ["jge", "jle", "jeq", "jmp"]
ENDIANNESS = "little"
def decode_jump(ins: int) -> str:
if (ins & 0x7) == 0:
return JUMP_NONE
if (ins & 0x7) == 0x7:
return "jmp"
jl = (ins & (1 << 2)) != 0
je = (ins & (1 << 1)) != 0
jg = (ins & (1 << 0)) != 0
# implied: and not jg
if jl and je:
return "jle"
# implied: and not je
if jl and jg:
return "jne"
# implied: and not je
if je and jg:
return "jge"
# implied: only one flag is 1
if jl:
return "jlt"
if je:
return "jeq"
if jg:
return "jgt"
return "<unknown>"
# return op, and whether it's a one-op or two-op
def decode_ins(ins: int) -> (str, bool):
opcode = (ins >> 8) & 0x03
ar_n_log = (ins & (1 << 10)) != 0
opcode |= ar_n_log << 2
if opcode == 0b000:
return "and", True
if opcode == 0b001:
return "or", True
if opcode == 0b010:
return "xor", True
if opcode == 0b011:
return "not", False
if opcode == 0b100:
return "add", True
if opcode == 0b101:
return "inc", False
if opcode == 0b110:
return "sub", True
if opcode == 0b111:
return "dec", False
return "<?>"
# normally, X = arg1 = D
def decode_arg1(ins: int) -> str:
use_mem = (ins & (1 << 12)) != 0
zx = (ins & (1 << 7)) != 0
sw = (ins & (1 << 6)) != 0
if zx:
return ZERO
if not sw:
return "D"
return "M" if use_mem else "A"
# normally, Y = arg2 = A
def decode_arg2(ins: int) -> str:
use_mem = (ins & (1 << 12)) != 0
# don't care, only X is zeroed
# zx = (ins & (1 << 7)) != 0
sw = (ins & (1 << 6)) != 0
if sw:
return "D"
return "M" if use_mem else "A"
def decode_dest(ins: int) -> str:
dA = (ins & (1 << 5)) != 0
dD = (ins & (1 << 4)) != 0
dM = (ins & (1 << 3)) != 0
dest = ""
if dA:
dest += "A"
if dD:
dest += "D"
if dM:
dest += "M"
return dest if dest else DEST_NONE
def decode_instruction(ins: int) -> list[str]:
"""
Will return a 5 element list/tuple/whatever
mnemonic, destination, X, Y, jumpdest
"""
if ins & 0x8000 == 0:
# mov? ldr? ldi? aaaaaaaaaaa....
return ["mov", "A", f"#{ins}", "", ""]
else:
mnemonic, two_op = decode_ins(ins)
dest = decode_dest(ins)
op1 = decode_arg1(ins)
op2 = decode_arg2(ins) if two_op else ""
jumpdest = decode_jump(ins)
return [mnemonic, dest, op1, op2, jumpdest]
def fixup_ins(ins: int) -> list[str]:
(mnemonic, dest, op1, op2, jumpdest) = decode_instruction(ins)
# fixups
if op1 == ZERO:
# subtract something from #0 - subtraction
if mnemonic == "sub":
return ["neg", dest, op2, "", jumpdest]
# 0 AND something = 0
if mnemonic == "and":
# if no dest, only jump matters
if dest == DEST_NONE:
# jump always or jump-if-zero --> always jump
if jumpdest in JUMPS_IF_ZERO:
return ["jmp", "", "", "", ""]
# all other jumps? <, >, <>, nojmp
else:
return ["nop", "", "", "", ""]
else:
if jumpdest in JUMPS_IF_ZERO:
newjmp = "jmp"
else:
newjmp = ""
return ["mov", dest, ZERO, "", newjmp]
# 0 +/|/^ something = something
if mnemonic in ["add", "or", "xor"]:
if dest == DEST_NONE and jumpdest == JUMP_NONE:
return ["nop", "", "", "", ""]
else:
return ["mov", dest, op2, "", jumpdest]
# basically, not 0 == 0xFFFF....
# opposite of what AND is doing?
if mnemonic == "not":
# if no dest, only jump matters
if dest == DEST_NONE:
# 0xFFFF is not jgt, since highest bit is always signed.
if jumpdest in ["jeq", "jgt", "jge", JUMP_NONE]:
return ["nop", "", "", "", ""]
else:
return ["jmp", "", "", "", ""]
elif dest == DEST_NONE:
if mnemonic == "sub":
return ["cmp", "", op1, op2, jumpdest]
return [mnemonic, dest, op1, op2, jumpdest]
def print_decoded(ins: int, simplify: bool) -> str:
# illegal instruction
if ins & 0xC000 == 0x8000:
return "halt"
if simplify:
(mnemonic, dest, op1, op2, jumpdest) = fixup_ins(ins)
else:
(mnemonic, dest, op1, op2, jumpdest) = decode_instruction(ins)
jumpdest_str = f".{jumpdest}" if jumpdest else ""
opcode_str = f"{mnemonic}{jumpdest_str}"
dest_str = f"{dest}, " if dest else 7 * " "
op2_str = ", " if op2 else ""
op1_str = f"{op1}{op2_str}"
return f"{opcode_str:<9}{dest_str:<6}{op1_str:<4}{op2}"
def main():
if len(sys.argv) != 2:
print(f"Usage: {sys.argv[0]} [filename]")
sys.exit(1)
try:
filename = sys.argv[1]
with open(filename, "rb") as f:
while True:
insb = f.read(2)
if not insb:
break
ins = int.from_bytes(insb, byteorder=ENDIANNESS)
if ENDIANNESS in ["big", "be"]:
raw_ins = f"{insb[0]:02x} {insb[1]:02x}"
elif ENDIANNESS in ["little", "le"]:
raw_ins = f"{insb[1]:02x} {insb[0]:02x}"
else:
raw_ins = f"?? ??"
decoded_ins = print_decoded(ins, False)
decoded_ins2 = print_decoded(ins, True)
if decoded_ins == decoded_ins2:
line = f"\t{raw_ins}\t{decoded_ins}"
else:
line = f"\t{raw_ins}\t{decoded_ins2:<25}; {decoded_ins}"
print(line)
except FileNotFoundError:
print(f"File {filename} not found.")
sys.exit(1)
# head, tail...
except BrokenPipeError:
sys.exit(0)
if __name__ == "__main__":
main()
|
