lparser.py: added support for while loops

This commit is contained in:
CPunch 2022-08-11 17:26:48 -05:00
parent 78e137d033
commit 95ca3bb26b
3 changed files with 64 additions and 40 deletions

View File

@ -12,44 +12,46 @@ Lua has a relatively small instruction set (only 38 different opcodes!). This ma
```sh
> cat example.lua && luac5.1 -o example.luac example.lua
pp = "pri" .. "nt"
i = 0
if 2 + 2 == 4 then
_G[pp]("Hello world")
while i < 10 do
print(i)
i = i + 1
end
> python main.py example.luac
example.luac
==== [[example.lua's constants]] ====
0: [STRING] pp
1: [STRING] pri
2: [STRING] nt
3: [NUMBER] 4.0
4: [STRING] _G
5: [STRING] Hello world
0: [STRING] i
1: [NUMBER] 0.0
2: [NUMBER] 10.0
3: [STRING] print
4: [NUMBER] 1.0
==== [[example.lua's dissassembly]] ====
[ 0] LOADK : R[0] K[1] ; load "pri" into R[0]
[ 1] LOADK : R[1] K[2] ; load "nt" into R[1]
[ 2] CONCAT : R[0] R[0] R[1] ; concat 2 values from R[0] to R[1], store into R[0]
[ 3] SETGLOBAL : R[0] K[0] ;
[ 4] EQ : R[0] K[3] K[3] ;
[ 5] JMP : R[0] R[5] ;
[ 6] GETGLOBAL : R[0] K[4] ;
[ 7] GETGLOBAL : R[1] K[0] ;
[ 8] GETTABLE : R[0] R[0] R[1] ;
[ 9] LOADK : R[1] K[5] ; load "Hello world" into R[1]
[ 10] CALL : R[0] R[2] R[1] ;
[ 11] RETURN : R[0] R[1] R[0] ;
[ 0] LOADK : R[0] K[1] ; load 0.0 into R[0]
[ 1] SETGLOBAL : R[0] K[0] ;
[ 2] GETGLOBAL : R[0] K[0] ;
[ 3] LT : R[0] R[0] K[2] ;
[ 4] JMP : R[0] 7 ;
[ 5] GETGLOBAL : R[0] K[3] ;
[ 6] GETGLOBAL : R[1] K[0] ;
[ 7] CALL : R[0] 2 1 ;
[ 8] GETGLOBAL : R[0] K[0] ;
[ 9] ADD : R[0] R[0] K[4] ;
[ 10] SETGLOBAL : R[0] K[0] ;
[ 11] JMP : R[0] -10 ;
[ 12] RETURN : R[0] 1 0 ;
==== [[example.lua's decompiled source]] ====
pp = "pri" .. "nt"
if 4.0 == 4.0 then
_G[pp]("Hello world")
i = 0.0
while i < 10.0 do
print(i)
i = (i + 1.0)
end
```

View File

@ -53,11 +53,17 @@ class LuaDecomp:
self.__startStatement()
self.__addExpr("local " + self.locals[indx] + " = " + expr)
def __getInstrAtPC(self, pc: int) -> Instruction:
if pc < len(self.chunk.instructions):
return self.chunk.instructions[pc]
raise Exception("Decompilation failed!")
def __getNextInstr(self) -> Instruction:
if self.pc + 1 < len(self.chunk.instructions):
return self.chunk.instructions[self.pc + 1]
return None
raise Exception("Decompilation failed!")
def __getCurrInstr(self) -> Instruction:
return self.chunk.instructions[self.pc]
@ -102,6 +108,30 @@ class LuaDecomp:
def __emitOperand(self, a: int, b: str, c: str, op: str) -> None:
self.__setReg(a, "(" + b + op + c + ")")
def __compJmp(self, op: str):
instr = self.__getCurrInstr()
jmpType = "if"
scopeStart = "then"
# we need to check if the jmp location has a jump back (if so, it's a while loop)
jmp = self.__getNextInstr().B + 1
jmpToInstr = self.__getInstrAtPC(self.pc + jmp)
if jmpToInstr.opcode == Opcodes.JMP:
# if this jump jumps back to this compJmp, it's a loop!
if self.pc + jmp + jmpToInstr.B <= self.pc + 1:
jmpType = "while"
scopeStart = "do"
self.__startStatement()
if instr.A > 0:
self.__addExpr("%s not " % jmpType)
else:
self.__addExpr("%s " % jmpType)
self.__addExpr(self.__readRK(instr.B) + op + self.__readRK(instr.C) + " ")
self.__startScope("%s " % scopeStart, jmp)
self.pc += 1 # skip next instr
# 'RK's are special in because can be a register or a konstant. a bitflag is read to determine which
def __readRK(self, rk: int) -> str:
if (whichRK(rk)) > 0:
@ -163,19 +193,11 @@ class LuaDecomp:
elif instr.opcode == Opcodes.JMP:
pass
elif instr.opcode == Opcodes.EQ:
self.__startStatement()
if instr.A > 0:
self.__addExpr("if not ")
else:
self.__addExpr("if ")
self.__addExpr(self.__readRK(instr.B) + " == " + self.__readRK(instr.C) + " ")
self.__startScope("then ", self.__getNextInstr().B + 1)
self.pc += 1 # skip next instr
self.__compJmp(" == ")
elif instr.opcode == Opcodes.LT:
self.__emitOperand(instr.A, self.__readRK(instr.B), self.__readRK(instr.C), " < ")
self.__compJmp(" < ")
elif instr.opcode == Opcodes.LE:
self.__emitOperand(instr.A, instr.B, instr.C, " <= ")
self.__compJmp(" <= ")
elif instr.opcode == Opcodes.CALL:
preStr = ""
callStr = ""

View File

@ -101,8 +101,8 @@ class Instruction:
if self.type == InstructionType.ABC:
# by default, treat them as registers
A = "R[%d]" % self.A
B = "R[%d]" % self.B
C = "R[%d]" % self.C
B = "%d" % self.B
C = "%d" % self.C
# these opcodes have RKs for B & C
if self.opcode in _RKBCInstr:
@ -114,7 +114,7 @@ class Instruction:
regs = "%6s %6s %6s" % (A, B, C)
elif self.type == InstructionType.ABx or self.type == InstructionType.AsBx:
A = "R[%d]" % self.A
B = "R[%d]" % self.B
B = "%d" % self.B
if self.opcode in _KBx:
B = "K[%d]" % self.B