Author: Yintao, Xu
Email: [email protected]
-
In this repository, we aim at parsing lua5.3's dumped file(a.k.a lua byte code).
- Chunkspy.lua,
luac -lprovides similar functionality.
- Chunkspy.lua,
-
The name is similar to
objdump, which displays information from object files.luacdumpinstead displays information for luac-precompiled lua scripts. -
It is one of the three steps to build a toy lua interpreter.
Run make at repository folder to build the luacdump.
./luacdump <file> <options>
- -h: Print formatted header block memory layout
- -f: Print function block memory layout
- -i: Print instructions
Example of a do end program into dumped file. Our goal is to understand and decode this binary file.
xxd minimal.luac
00000000: 1b4c 7561 5300 1993 0d0a 1a0a 0408 0408 .LuaS...........
00000010: 0878 5600 0000 0000 0000 0000 0000 2877 .xV...........(w
00000020: 4001 0d40 6d69 6e69 6d61 6c2e 6c75 6100 @[email protected].
00000030: 0000 0000 0000 0000 0202 0100 0000 2600 ..............&.
00000040: 8000 0000 0000 0100 0000 0100 0000 0000 ................
00000050: 0100 0000 0100 0000 0000 0000 0100 0000 ................
00000060: 055f 454e 56 ._ENVParsed by luacformatter:
$ ./luacdump luas/minimal.luac -hf
| Offset | Content | Desciption |
| ---------- | ------------ | ------------------------------------ |
| | | |
| | | **Lua Metadata** |
| | | |
| 0x00000000 | 0x1b4c7561 | Lua signature |
| 0x00000004 | 0x53 | Lua version |
| 0x00000005 | 0x00 | Lua Format Version |
| 0x00000006 | 0x19930d0a1a | Lua Data |
| | 0a | |
| | | |
| | | **Lua Metadata(Sizes)** |
| | | |
| 0x0000000c | 0x04 | Size of Integer |
| 0x0000000d | 0x08 | Size of size_t |
| 0x0000000e | 0x04 | Size of Instruction |
| 0x0000000f | 0x08 | Size of Lua Integer |
| 0x00000010 | 0x08 | Size of Lua Number |
| | | |
| | | **Lua Examples** |
| | | |
| 0x00000011 | 22136 | Example Lua Integer (0x5678=22146) |
| 0x00000019 | 370.500000 | Example Lua Number (370.5) |
| | | |
| 0x00000021 | 0x01 | Size of Up Values |
| | | |
| 0x00000022 | | End of table |
Table Size: 34
Function[0]: Level 0
| Offset | Content | Desciption |
| ---------- | ------------ | ------------------------------------ |
| | | |
| | | **Lua Function Metadata** |
| | | |
| 0x00000022 | @luas/minima | Source name |
| | l.lua | |
| 0x00000034 | 0x00000000 | First line defined |
| 0x00000038 | 0x00000000 | Last lind defined |
| 0x0000003c | 0 | Number of params |
| 0x0000003d | 0x02 | `is_vararg` flag |
| 0x0000003e | 2 | Maximum stack size |
| | | |
| | | **Function Instructions** |
| | | |
| 0x0000003f | 1 | Number of instructions |
| 0x00000047 | 0x00800026 | instr 0, optcode 38 |
| | | |
| | | **Constants** |
| | | |
| 0x00000047 | 0 | Number of constants |
| | | |
| | | **UpValues** |
| | | |
| 0x0000004b | 1 | Number of upvalues |
| | | Upvalue [0] |
| 0x0000004f | 1 | is instack |
| 0x00000050 | 0 | upval index |
| | | |
| | | **Sub Functions** |
| | | |
| 0x00000051 | 0 | Sub Function Nums |
| | | |
| | | **Debug Infos - Line Info(opcode -> |
| | | src. line)** |
| | | |
| 0x00000059 | op code [0] | source code line [1] |
| | | |
| | | **Debug Infos - Local Variables** |
| | | |
| 0x0000005d | 0 | Number of local variables |
| | | |
| | | **Debug Infos - Up Values Names** |
| | | |
| 0x00000061 | 1 | Number of up values |
| 0x00000065 | _ENV | [0] Name |
| | | |
| 0x00000065 | | End of table |
Table Size: 72For such a lua program:
local a = 8
function b(c) d = a + c endParsed by luacdump:
$ ./luacdump luas/subfunc.luac -i
**function main **
|
| .const
| [ 0] 8
| [ 1] "b"
|
| .local
| [ 0] "a"
|
| .upvalue
| [ 0] _ENV
|
| **function main.KPROTO[0] **
| |
| | .const
| | [ 0] "d"
| |
| | .local
| | [ 0] "c"
| |
| | .upvalue
| | [ 0] _ENV
| | [ 1] a
| |
| | .instructions
| |
| | [ 0] 00800045 GETUPVAL R(1) := UpValue[1]
| | R(1) := a
| | [ 1] 0080004d ADD R(1) := RK(1) + RK(0)
| | R(1) := R(1) + R(0)
| | [ 2] 80004008 SETTABUP UpValue[0][RK(256)] := RK(1)
| | _ENV["d"] = R(1)
| | [ 3] 00800026 RETURN return void
| |
| **end of function main.KPROTO[0] **
|
| .instructions
|
| [ 0] 00000001 LOADK R(0) := Kst(0)
| a := 8
| [ 1] 0000006c CLOSURE R(1) := closure(KPROTO[0])
| [ 2] 80804008 SETTABUP UpValue[0][RK(257)] := RK(1)
| _ENV["b"] = R(1)
| [ 3] 00800026 RETURN return void
|
**end of function main **- What is lua dumped file? How to get it from source code?
- Lua Dumped Files Layout: header block and top-level function
- Lua VM Bytecode Table
- A No-Frills Introduction to Lua 5.1 VM instructions by Kein-Hong Man, esq.
- https://the-ravi-programming-language.readthedocs.io/en/latest/lua_bytecode_reference.html