조건 점프 문서의 검증 코드다. if __name__ == "__main__": 아래가 자체 테스트다.
"""조건 점프 문서의 표 확인 (파이썬 흉내, 실제 MASM 실행 아님).
CMP 뒤의 플래그로 점프 조건식을 계산해, 8비트 두 수의 모든 쌍(65,536쌍)에서
부호 없는 비교·부호 있는 비교와 맞는지 본다.
실행: python3 31_conditional-jumps_verify.py"""
import re
# ---------------------------------------------------------------------------
# x86 흉내기: 이 파일에서 쓰는 만큼만 흉내 낸다 (MASM 문법의 일부를 그대로 읽는다).
# 레지스터 8·16·32비트, ZF/SF/CF/OF/PF, 리틀 엔디언 메모리, 스택, CALL/RET.
# 코드 주소는 실제 기계어 길이가 아니다. 줄 앞에 8자리 16진수를 쓰면 그 주소를 쓰고,
# 안 쓰면 CALL은 5, 나머지는 2씩 늘린다(예: 00000020의 call 다음 줄은 00000025).
# ---------------------------------------------------------------------------
REG32 = ["eax", "ecx", "edx", "ebx", "esp", "ebp", "esi", "edi"]
REG16 = {"ax": "eax", "cx": "ecx", "dx": "edx", "bx": "ebx",
"sp": "esp", "bp": "ebp", "si": "esi", "di": "edi"}
REG8L = {"al": "eax", "cl": "ecx", "dl": "edx", "bl": "ebx"}
REG8H = {"ah": "eax", "ch": "ecx", "dh": "edx", "bh": "ebx"}
TYPES = {"byte": 1, "sbyte": 1, "word": 2, "sword": 2, "dword": 4, "sdword": 4}
STOP = 0xFFFFFFF0 # call_proc이 스택에 넣어 두는 가짜 복귀 주소
JCC = {
"jz": lambda f: f["ZF"], "je": lambda f: f["ZF"],
"jnz": lambda f: not f["ZF"], "jne": lambda f: not f["ZF"],
"jc": lambda f: f["CF"], "jb": lambda f: f["CF"], "jnae": lambda f: f["CF"],
"jnc": lambda f: not f["CF"], "jae": lambda f: not f["CF"], "jnb": lambda f: not f["CF"],
"jo": lambda f: f["OF"], "jno": lambda f: not f["OF"],
"js": lambda f: f["SF"], "jns": lambda f: not f["SF"],
"jp": lambda f: f["PF"], "jnp": lambda f: not f["PF"],
"ja": lambda f: not f["CF"] and not f["ZF"], "jnbe": lambda f: not f["CF"] and not f["ZF"],
"jbe": lambda f: f["CF"] or f["ZF"], "jna": lambda f: f["CF"] or f["ZF"],
"jg": lambda f: not f["ZF"] and f["SF"] == f["OF"],
"jnle": lambda f: not f["ZF"] and f["SF"] == f["OF"],
"jge": lambda f: f["SF"] == f["OF"], "jnl": lambda f: f["SF"] == f["OF"],
"jl": lambda f: f["SF"] != f["OF"], "jnge": lambda f: f["SF"] != f["OF"],
"jle": lambda f: f["ZF"] or f["SF"] != f["OF"],
"jng": lambda f: f["ZF"] or f["SF"] != f["OF"],
}
def signed(v, n):
"""n바이트 값 v를 부호 있는 정수로 읽는다."""
bits = 8 * n
return v - (1 << bits) if v >> (bits - 1) else v
class CPU:
def __init__(self, esp=0x1000):
self.r = {k: 0 for k in REG32}
self.r["esp"] = esp
self.f = dict(ZF=0, SF=0, CF=0, OF=0, PF=0)
self.mem = {} # 주소 -> 바이트
self.sym = {} # 변수 이름 -> (주소, 원소 크기, 원소 수)
self.const = {} # 기호 상수 -> 값
self.here = 0x4000 # 데이터 위치 카운터
self.code = [] # (주소, 연산, [피연산자], 원문)
self.label = {} # 레이블 -> 코드 주소
self.at = {} # 코드 주소 -> code 인덱스
self.hook = {} # 라이브러리 프로시저 흉내: 이름 -> 함수(cpu)
self.steps = 0
self.trace = None # 리스트를 넣어 두면 (원문, 레지스터, 플래그)를 쌓는다
self.calls = [] # 호출한 프로시저 이름 기록
# ---- 레지스터와 메모리 ----
def get(self, name):
name = name.lower()
if name in self.r:
return self.r[name]
if name in REG16:
return self.r[REG16[name]] & 0xFFFF
if name in REG8L:
return self.r[REG8L[name]] & 0xFF
if name in REG8H:
return (self.r[REG8H[name]] >> 8) & 0xFF
raise KeyError(name)
def put(self, name, v):
name = name.lower()
if name in self.r:
self.r[name] = v & 0xFFFFFFFF
elif name in REG16:
k = REG16[name]
self.r[k] = (self.r[k] & 0xFFFF0000) | (v & 0xFFFF)
elif name in REG8L:
k = REG8L[name]
self.r[k] = (self.r[k] & 0xFFFFFF00) | (v & 0xFF)
elif name in REG8H:
k = REG8H[name]
self.r[k] = (self.r[k] & 0xFFFF00FF) | ((v & 0xFF) << 8)
else:
raise KeyError(name)
@staticmethod
def regsize(name):
name = name.lower()
if name in REG32:
return 4
if name in REG16:
return 2
if name in REG8L or name in REG8H:
return 1
return None
def rd(self, addr, n):
"""리틀 엔디언: 낮은 주소에 낮은 바이트."""
return sum(self.mem.get(addr + i, 0) << (8 * i) for i in range(n))
def wr(self, addr, n, v):
for i in range(n):
self.mem[addr + i] = (v >> (8 * i)) & 0xFF
# ---- 데이터 정의 ----
def data(self, name, typ, values):
"""name TYPE values. 문자열은 글자마다 한 바이트, 레이블 이름은 그 코드 주소."""
n = TYPES[typ.lower()]
flat = []
for v in values:
if isinstance(v, str) and v in self.label:
flat.append(self.label[v])
elif isinstance(v, str):
flat.extend(ord(c) for c in v)
else:
flat.append(v)
addr = self.here
if name:
self.sym[name.lower()] = (addr, n, len(flat))
for v in flat:
self.wr(self.here, n, v)
self.here += n
return addr
# ---- 식과 피연산자 ----
def num(self, s):
"""상수식: 10진, 16진(h), 2진(b), 글자, 기호 상수, OFFSET/LENGTHOF/TYPE/SIZEOF, + - * / ( )."""
s = s.strip()
s = re.sub(r"'(.)'", lambda m: str(ord(m.group(1))), s)
def op(m):
a, n, c = self.sym[m.group(2).lower()]
return str({"offset": a, "lengthof": c, "type": n, "sizeof": n * c}[m.group(1).lower()])
s = re.sub(r"(?i)\b(offset|lengthof|type|sizeof)\s+(\w+)", op, s)
def tok(m):
t = m.group(0)
low = t.lower()
if re.fullmatch(r"[0-9][0-9a-f]*h", low):
return str(int(low[:-1], 16))
if re.fullmatch(r"[01]+b", low):
return str(int(low[:-1], 2))
if re.fullmatch(r"[0-9]+d?", low):
return str(int(low.rstrip("d")))
if low in self.const:
return str(self.const[low])
if low in self.label:
return str(self.label[low])
if t in self.label:
return str(self.label[t])
raise ValueError("모르는 이름: " + t)
s = re.sub(r"\w+", tok, s)
if not re.fullmatch(r"[0-9+\-*/() ]+", s):
raise ValueError("식을 못 읽음: " + s)
return int(eval(s.replace("/", "//")))
def operand(self, s):
"""('reg', 이름, 크기) / ('imm', 값, None) / ('mem', 주소, 크기 또는 None)"""
s = s.strip()
size = None
m = re.match(r"(?i)(byte|sbyte|word|sword|dword|sdword|near)\s+ptr\s+(.*)", s)
if m:
size = 4 if m.group(1).lower() == "near" else TYPES[m.group(1).lower()]
s = m.group(2).strip()
if self.regsize(s):
return ("reg", s.lower(), self.regsize(s))
m = re.fullmatch(r"(\w+)?\s*\[([^\]]+)\]", s)
if m:
addr = 0
if m.group(1):
a, n, _ = self.sym[m.group(1).lower()]
addr, size = a, size or n
for sign, term in re.findall(r"([+-]?)\s*([^+-]+)", m.group(2)):
term = term.strip()
v = self.get(term) if self.regsize(term) else self.num(term)
addr += -v if sign == "-" else v
return ("mem", addr & 0xFFFFFFFF, size)
m = re.fullmatch(r"(\w+)\s*(?:([+-])\s*(\w+))?", s)
if m and m.group(1).lower() in self.sym and not re.match(r"(?i)(offset|lengthof|type|sizeof)\b", s):
a, n, _ = self.sym[m.group(1).lower()]
if m.group(2):
d = self.num(m.group(3))
a += -d if m.group(2) == "-" else d
return ("mem", a, size or n)
return ("imm", self.num(s), None)
def val(self, o, n):
if o[0] == "reg":
return self.get(o[1])
if o[0] == "imm":
return o[1] & ((1 << (8 * n)) - 1)
return self.rd(o[1], n)
def store(self, o, n, v):
v &= (1 << (8 * n)) - 1
if o[0] == "reg":
self.put(o[1], v)
else:
self.wr(o[1], n, v)
# ---- 플래그 ----
def szp(self, v, n):
self.f["ZF"] = int(v == 0)
self.f["SF"] = (v >> (8 * n - 1)) & 1
self.f["PF"] = int(bin(v & 0xFF).count("1") % 2 == 0)
def add(self, a, b, n):
mask = (1 << (8 * n)) - 1
r = (a + b) & mask
top = 8 * n - 1
self.f["CF"] = int(a + b > mask)
self.f["OF"] = int((a >> top) == (b >> top) and (r >> top) != (a >> top))
self.szp(r, n)
return r
def sub(self, a, b, n):
mask = (1 << (8 * n)) - 1
r = (a - b) & mask
top = 8 * n - 1
self.f["CF"] = int(a < b)
self.f["OF"] = int((a >> top) != (b >> top) and (r >> top) != (a >> top))
self.szp(r, n)
return r
def logic(self, r, n):
self.f["CF"] = self.f["OF"] = 0
self.szp(r, n)
return r
# ---- 스택 ----
def push(self, v, n=4):
self.r["esp"] = (self.r["esp"] - n) & 0xFFFFFFFF
self.wr(self.r["esp"], n, v)
def pop(self, n=4):
v = self.rd(self.r["esp"], n)
self.r["esp"] = (self.r["esp"] + n) & 0xFFFFFFFF
return v
def eflags(self):
f = self.f
return f["CF"] | 2 | f["PF"] << 2 | f["ZF"] << 6 | f["SF"] << 7 | f["OF"] << 11
# ---- 코드 읽기 ----
def load(self, text, base=0):
cur = base
pending, uses = [], []
for raw in text.splitlines():
line = raw.split(";")[0].strip()
if not line or line.lower() in (".code", ".data"):
continue
m = re.match(r"([0-9A-Fa-f]{8})\s+(.*)", line)
if m:
cur, line = int(m.group(1), 16), m.group(2).strip()
m = re.fullmatch(r"(?i)(\w+)\s+PROC(?:\s+USES\s+(.*))?", line)
if m:
pending.append(m.group(1))
uses = m.group(2).split() if m.group(2) else []
for reg in uses: # USES가 만드는 push
cur = self._emit(cur, "push", [reg], "push " + reg, pending)
pending = []
continue
if re.fullmatch(r"(?i)\w+\s+ENDP", line):
uses = []
continue
m = re.match(r"(\w+)::?\s*(.*)", line)
if m and ":" in line.split()[0]:
pending.append(m.group(1))
line = m.group(2).strip()
if not line:
continue
parts = line.split(None, 1)
op = parts[0].lower()
args = [a.strip() for a in parts[1].split(",")] if len(parts) > 1 else []
if op == "ret":
for reg in reversed(uses): # USES가 만드는 pop
cur = self._emit(cur, "pop", [reg], "pop " + reg, pending)
pending = []
cur = self._emit(cur, op, args, line, pending)
pending = []
for name in pending: # 맨 끝의 레이블(next: 같은 것)
self.label[name] = self.label[name.lower()] = cur
self.end = cur
def _emit(self, cur, op, args, line, pending):
for name in pending:
self.label[name] = self.label[name.lower()] = cur
self.at[cur] = len(self.code)
self.code.append((cur, op, args, line))
return cur + (5 if op == "call" else 2)
def target(self, s):
if s in self.label:
return self.label[s]
if s.lower() in self.label:
return self.label[s.lower()]
o = self.operand(s)
return self.val(o, 4)
# ---- 실행 ----
def run(self, start=None, max_steps=10 ** 6):
eip = self.target(start) if isinstance(start, str) else (start if start is not None else self.code[0][0])
while eip in self.at:
self.steps += 1
if self.steps > max_steps:
raise RuntimeError("너무 오래 돈다")
i = self.at[eip]
addr, op, a, line = self.code[i]
nxt = self.code[i + 1][0] if i + 1 < len(self.code) else self.end
eip = self.step(op, a, nxt)
if self.trace is not None:
self.trace.append((line, dict(self.r), dict(self.f)))
if eip is None:
break
self.eip = eip
return self
def call_proc(self, name):
self.push(STOP)
return self.run(name)
def step(self, op, a, nxt):
f = self.f
if op in ("exit", "hlt"):
return None
if op == "nop":
return nxt
if op == "jmp":
return self.target(a[0])
if op in JCC:
return self.target(a[0]) if JCC[op](f) else nxt
if op == "jecxz":
return self.target(a[0]) if self.r["ecx"] == 0 else nxt
if op == "jcxz":
return self.target(a[0]) if self.get("cx") == 0 else nxt
if op in ("loop", "loope", "loopz", "loopne", "loopnz"):
self.r["ecx"] = (self.r["ecx"] - 1) & 0xFFFFFFFF # 플래그는 안 바뀐다
go = self.r["ecx"] != 0
if op in ("loope", "loopz"):
go = go and f["ZF"] == 1
if op in ("loopne", "loopnz"):
go = go and f["ZF"] == 0
return self.target(a[0]) if go else nxt
if op == "call":
if a[0] in self.hook:
self.calls.append(a[0])
self.hook[a[0]](self)
return nxt
t = self.target(a[0])
self.calls.append(a[0])
self.push(nxt)
return t
if op == "ret":
t = self.pop()
return None if t == STOP else t
if op == "push":
o = self.operand(a[0])
n = 2 if (o[0] == "reg" and o[2] == 2) or (o[0] == "mem" and o[2] == 2) else 4
self.push(self.val(o, n), n)
return nxt
if op == "pop":
o = self.operand(a[0])
n = 2 if o[2] == 2 else 4
self.store(o, n, self.pop(n))
return nxt
if op == "pushfd":
self.push(self.eflags())
return nxt
if op == "popfd":
v = self.pop()
f.update(CF=v & 1, PF=(v >> 2) & 1, ZF=(v >> 6) & 1, SF=(v >> 7) & 1, OF=(v >> 11) & 1)
return nxt
if op == "pushad":
old = self.r["esp"]
for k in ["eax", "ecx", "edx", "ebx"]:
self.push(self.r[k])
self.push(old)
for k in ["ebp", "esi", "edi"]:
self.push(self.r[k])
return nxt
if op == "popad":
for k in ["edi", "esi", "ebp"]:
self.r[k] = self.pop()
self.pop() # ESP 칸은 버린다
for k in ["ebx", "edx", "ecx", "eax"]:
self.r[k] = self.pop()
return nxt
# ---- 피연산자가 있는 명령 ----
d = self.operand(a[0])
s = self.operand(a[1]) if len(a) > 1 else None
n = d[2] or (s[2] if s else None)
if n is None:
raise ValueError("크기를 알 수 없다: " + " ".join(a))
if op in ("movzx", "movsx"):
sn = s[2]
v = self.val(s, sn)
self.store(d, d[2], signed(v, sn) if op == "movsx" else v)
return nxt
if s is not None and s[0] != "imm" and d[2] and s[2] and d[2] != s[2] and op not in ("shl", "sal", "shr", "sar"):
raise ValueError("크기가 다르다: " + " ".join(a))
x = self.val(d, n)
y = self.val(s, n) if s else None
top = 8 * n - 1
if op == "mov":
self.store(d, n, y)
elif op == "xchg":
self.store(d, n, y)
self.store(s, n, x)
elif op == "add":
self.store(d, n, self.add(x, y, n))
elif op == "sub":
self.store(d, n, self.sub(x, y, n))
elif op == "cmp":
self.sub(x, y, n) # 결과는 버린다
elif op == "inc":
c = f["CF"]
self.store(d, n, self.add(x, 1, n))
f["CF"] = c # INC는 CF를 안 건드린다
elif op == "dec":
c = f["CF"]
self.store(d, n, self.sub(x, 1, n))
f["CF"] = c
elif op == "neg":
self.store(d, n, self.sub(0, x, n))
elif op == "and":
self.store(d, n, self.logic(x & y, n))
elif op == "test":
self.logic(x & y, n) # 결과는 버린다
elif op == "or":
self.store(d, n, self.logic(x | y, n))
elif op == "xor":
self.store(d, n, self.logic(x ^ y, n))
elif op == "not":
self.store(d, n, ~x) # 플래그는 안 바뀐다
elif op in ("shl", "sal", "shr", "sar"):
c = self.val(s, 1) & 31
for _ in range(c):
if op in ("shl", "sal"):
f["CF"] = (x >> top) & 1
x = (x << 1) & ((1 << (8 * n)) - 1)
else:
f["CF"] = x & 1
x = (x >> 1) | ((x >> top) << top if op == "sar" else 0)
if c:
self.szp(x, n)
self.store(d, n, x)
else:
raise ValueError("모르는 명령: " + op)
return nxt
def machine(code, esp=0x1000, base=0):
c = CPU(esp)
c.load(code, base)
return c
UNSIGNED = {"ja": ">", "jnbe": ">", "jae": ">=", "jnb": ">=", "jb": "<", "jnae": "<", "jbe": "<=", "jna": "<="}
SIGNED = {"jg": ">", "jnle": ">", "jge": ">=", "jnl": ">=", "jl": "<", "jnge": "<", "jle": "<=", "jng": "<="}
REL = {">": lambda a, b: a > b, ">=": lambda a, b: a >= b, "<": lambda a, b: a < b, "<=": lambda a, b: a <= b}
def taken(code, **reg):
"""code 끝에서 점프했으면 True. 점프 대상 T, 안 뛰면 EDI = 1."""
c = machine(code + " T\nmov edi,1\nT:")
for k, v in reg.items():
c.put(k, v)
c.run()
return c.r["edi"] == 0
def main():
# 1. 비교 점프 16개: 8비트 전수
differ = 0
for a in range(256):
for b in range(256):
c = CPU()
c.sub(a, b, 1) # CMP a,b
f = c.f
for j, rel in UNSIGNED.items():
assert bool(JCC[j](f)) == REL[rel](a, b), (j, a, b)
for j, rel in SIGNED.items():
assert bool(JCC[j](f)) == REL[rel](signed(a, 1), signed(b, 1)), (j, a, b)
assert bool(JCC["je"](f)) == (a == b) and bool(JCC["jne"](f)) == (a != b)
assert bool(JCC["jb"](f)) == bool(JCC["jc"](f)) and bool(JCC["je"](f)) == bool(JCC["jz"](f))
if bool(JCC["ja"](f)) != bool(JCC["jg"](f)):
differ += 1
assert (a >> 7) != (b >> 7) # 두 답이 갈리는 것은 맨 위 비트가 서로 다를 때뿐
assert differ == 32768 # 정확히 절반
# 16비트에서도 무작위로
import random
rnd = random.Random(3)
for _ in range(20000):
a, b = rnd.randrange(65536), rnd.randrange(65536)
c = CPU()
c.sub(a, b, 2)
for j, rel in UNSIGNED.items():
assert bool(JCC[j](c.f)) == REL[rel](a, b)
for j, rel in SIGNED.items():
assert bool(JCC[j](c.f)) == REL[rel](signed(a, 2), signed(b, 2))
# 2. 특정 플래그 점프
pairs = [("jz", "ZF", 1), ("jnz", "ZF", 0), ("jc", "CF", 1), ("jnc", "CF", 0), ("jo", "OF", 1),
("jno", "OF", 0), ("js", "SF", 1), ("jns", "SF", 0), ("jp", "PF", 1), ("jnp", "PF", 0)]
for j, flag, want in pairs:
for v in (0, 1):
f = dict(ZF=0, SF=0, CF=0, OF=0, PF=0)
f[flag] = v
assert bool(JCC[j](f)) == (v == want)
# 3. JECXZ, JCXZ
assert taken("jecxz", ecx=0) and not taken("jecxz", ecx=0x10000)
assert taken("jcxz", ecx=0x10000) and not taken("jcxz", ecx=1) # CX만 본다
# 4. 응용
assert taken("cmp eax,ebx\nja", eax=0xFFFFFFFF, ebx=1) # 부호 없이 4,294,967,295 > 1
assert not taken("cmp eax,ebx\njg", eax=0xFFFFFFFF, ebx=1) # 부호 있게 -1 > 1 은 거짓
assert taken("cmp eax,ebx\njg", eax=5, ebx=0xFFFFFFFE)
large = "mov Large,bx\ncmp ax,bx\njna Next\nmov Large,ax\nNext:"
small = "mov Small,ax\ncmp bx,ax\njnl Next\nmov Small,bx\nNext:"
for a in (0, 1, 2, 0x7FFF, 0x8000, 0xFFFF):
for b in (0, 1, 2, 0x7FFF, 0x8000, 0xFFFF):
c = machine(large)
v = c.data("Large", "WORD", [0])
c.put("ax", a)
c.put("bx", b)
c.run()
assert c.rd(v, 2) == max(a, b)
c = machine(small)
v = c.data("Small", "WORD", [0])
c.put("ax", a)
c.put("bx", b)
c.run()
assert signed(c.rd(v, 2), 2) == min(signed(a, 2), signed(b, 2))
for w in (0, 1, 0x8000):
c = machine("cmp WORD PTR [esi],0\nje L1\nmov bl,1\nL1:")
c.r["esi"] = c.data("w", "WORD", [w])
c.run()
assert (c.get("bl") == 0) == (w == 0)
for d in (0, 1, 2, 0xFFFFFFFF, 0x80000000):
c = machine("test DWORD PTR [edi],1\njz L2\nmov bl,1\nL2:")
c.r["edi"] = c.data("d", "DWORD", [d])
c.run()
assert (c.get("bl") == 0) == (d % 2 == 0)
# 5. 문서의 예: AL = FFh, BL = 01h
c = CPU()
c.sub(0xFF, 0x01, 1)
assert (c.f["ZF"], c.f["CF"], c.f["SF"], c.f["OF"]) == (0, 0, 1, 0)
assert JCC["ja"](c.f) and not JCC["jg"](c.f) and JCC["jl"](c.f) and not JCC["jb"](c.f)
# 넘침이 있는 예: 80h(-128) 대 01h. 결과 7Fh, SF = 0, OF = 1
c = CPU()
c.sub(0x80, 0x01, 1)
assert (c.f["SF"], c.f["OF"], c.f["CF"]) == (0, 1, 0) and JCC["jl"](c.f) and JCC["ja"](c.f)
# "SF만 보면 된다"가 틀리는 쌍의 수: 넘침이 난 쌍
wrong = 0
for a in range(256):
for b in range(256):
c = CPU()
c.sub(a, b, 1)
if bool(c.f["SF"]) != (signed(a, 1) < signed(b, 1)):
wrong += 1
assert c.f["OF"] == 1
assert wrong == 16384 # 전체의 4분의 1
# 6. 카드
c = CPU()
c.sub(0x90, 0x20, 1) # C2: 144 대 32, -112 대 32. 결과 70h, 넘침
assert (c.f["ZF"], c.f["CF"], c.f["SF"], c.f["OF"]) == (0, 0, 0, 1)
got = [j for j in ("ja", "jb", "jg", "jl", "je") if JCC[j](c.f)]
assert got == ["ja", "jl"]
c = CPU()
c.sub(0x10, 0x10, 1)
assert [j for j in ("jae", "jbe", "jge", "jle", "ja", "jg", "jb", "jl") if JCC[j](c.f)] == ["jae", "jbe", "jge", "jle"]
# 오해 항목: CMP와 점프 사이에 ADD를 끼우면 점프는 ADD의 플래그를 본다
assert taken("cmp eax,ebx\nja", eax=5, ebx=1)
assert not taken("cmp eax,ebx\nadd ecx,1\nja", eax=5, ebx=1, ecx=0xFFFFFFFF) # ADD가 CF = 1, ZF = 1
# JECXZ로 루프 건너뛰기: ECX = 0이면 몸통을 한 번도 안 돈다
c = machine("jecxz Done\nL1: inc eax\nloop L1\nDone:").run()
assert c.r["eax"] == 0
c = machine("mov ecx,3\njecxz Done\nL1: inc eax\nloop L1\nDone:").run()
assert c.r["eax"] == 3
if __name__ == "__main__":
main()
print("ALL CHECKS PASSED")