From e76d2cb18790b8c43fbb174f8523e7e678896883 Mon Sep 17 00:00:00 2001
From: Enrico Lumetti <enrico.lumetti@gmail.com>
Date: Sun, 8 May 2022 09:56:37 +0200
Subject: [PATCH] Improve inspect and add skeleton for VM

---
 README.md       |  2 +-
 inspectbc.lua   | 64 +++++++++++++++++++++++++++++++++++++++++--------
 microLua.lua    |  8 +++++--
 opcodes.lua     |  5 ++--
 readbc.lua      | 11 +++++----
 tests/test2.lua |  4 ++++
 vm.lua          | 36 ++++++++++++++++++++++++++++
 7 files changed, 111 insertions(+), 19 deletions(-)
 create mode 100644 tests/test2.lua

diff --git a/README.md b/README.md
index 73bd702..3cf19b6 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,3 @@
 # microLua
 
-LuaJIT bytecode interpreter written in Lua.
\ No newline at end of file
+LuaJIT bytecode interpreter written in LuaJIT.
diff --git a/inspectbc.lua b/inspectbc.lua
index f150416..aea6a4d 100644
--- a/inspectbc.lua
+++ b/inspectbc.lua
@@ -1,15 +1,59 @@
 local readbc = require('readbc')
 local opcodes = require('opcodes')
 
-fp = io.open('tests/test1.luo')
-header = readbc.read_header(fp)
-proto = readbc.read_proto(fp)
-fp:close()
+local function inspect_proto(proto)
+    print('\n-- proto --')
+    -- print('Debug: ' .. proto.debug)
+    print('Params: ' .. proto.numparams)
+    print('Frame Size: ' .. proto.framesize)
+    print('#Upvalues: ' .. proto.numuv)
+    print('#kgc: ' .. proto.numkgc)
+    print('#bcins: ' .. proto.numbc)
 
-for i = 1, #proto.bcins do
-    local decoded = opcodes.decode(proto.bcins[i])
-    local def = opcodes.defs[decoded.id]
-    print(def.name)
-    print(decoded.a)
-    print(decoded.d)
+    print('-- bytecode --')
+    for i = 1, #proto.bcins do
+        local decoded = opcodes.decode(proto.bcins[i])
+        if opcodes.defs[decoded.id] ~= nil then
+            local def = opcodes.defs[decoded.id]
+            -- check for ABC or AD format
+            if def.b == opcodes.Mode.none then
+                print(string.format('%s\t A: %s\tB: %s\t C: %s', def.name, decoded.a, decoded.b, decoded.c))
+            else
+                print(string.format('%s\t A: %s\tD: %s', def.name, decoded.a, decoded.d))
+            end
+        else
+            print('UNKNOWN OPCODE')
+        end
+    end
 end
+
+local function inspect(fp)
+    local header = readbc.read_header(fp)
+
+    print('-- header --')
+    print('Name: ' .. header.name)
+    print(string.format('Bytecode Version: %s', header.version))
+    print('Stripped: ' .. (header.stripped and 'yes' or 'no'))
+
+    local proto = readbc.read_proto(fp)
+    while proto ~= nil do
+        inspect_proto(proto)
+        proto = readbc.read_proto(fp)
+    end
+end
+
+local arg = {...}
+if arg[1] == nil then
+    print('Please pass a LuaJIT bytecode file as command line argument')
+    return 1
+end
+
+local fp = io.open(arg[1])
+if fp == nil then
+    print('Could not open path ' .. arg[1])
+    return 1
+end
+
+inspect(fp)
+
+fp:close()
diff --git a/microLua.lua b/microLua.lua
index 2067113..24669f9 100644
--- a/microLua.lua
+++ b/microLua.lua
@@ -1,8 +1,12 @@
 local readbc = require('readbc')
+local vm = require('vm')
+local VM = vm.VM
 
 fp = io.open('tests/test1.luo')
 header = readbc.read_header(fp)
 proto = readbc.read_proto(fp)
-fo:close()
+fp:close()
 
-print(#proto.bcins)
+vm = VM.new()
+vm:set_proto(proto)
+vm:run()
diff --git a/opcodes.lua b/opcodes.lua
index c84d449..62f4e27 100644
--- a/opcodes.lua
+++ b/opcodes.lua
@@ -77,8 +77,8 @@ local function decode(ins)
     -- TODO: endianess
     local id = bit.band(ins, 0xff)
     local a = bit.band(ins, 0xff00) / 0x100
-    local b = bit.band(ins, 0xff0000) / 0x10000
-    local c = bit.band(ins, 0xff000000) / 0x1000000
+    local c = bit.band(ins, 0xff0000) / 0x10000
+    local b = bit.band(ins, 0xff000000) / 0x1000000
     local d = bit.band(ins, 0xffff0000) / 0x10000
     return {
         id = id,
@@ -91,5 +91,6 @@ end
 
 return {
     defs = Opcodes_defs,
+    Mode = Mode,
     decode = decode,
 }
diff --git a/readbc.lua b/readbc.lua
index 98ce53e..386dde2 100644
--- a/readbc.lua
+++ b/readbc.lua
@@ -3,7 +3,7 @@
 local bit=require('bit')
 
 local HEADER_MAGIC = {27, string.byte('L'), string.byte('J')}
-local HEADER_FLAG_STRIP = 0x02
+local FLAG_STRIP = 0x02
 
 local function read_u8(fp)
     return string.byte(fp:read(1))
@@ -67,9 +67,12 @@ local function read_header(fp)
     local flags = read_uleb128(fp)
 
     local name
-    if bit.band(flags, HEADER_FLAG_STRIP) ~= 0 then
+    local stripped
+    if bit.band(flags, FLAG_STRIP) ~= 0 then
+        stripped = true
         name = ''
     else
+        stripped = false
         local nameLen = read_uleb128(fp)
         name = fp:read(nameLen)
     end
@@ -77,7 +80,7 @@ local function read_header(fp)
     return {
         magic = magic,
         version = version,
-        flags = flags,
+        stripped = stripped,
         name = name,
     }
 end
@@ -103,7 +106,7 @@ local function read_proto(fp)
     local debugLen = 0
     local debugInfo = nil
 
-    if bit.band(flags, HEADER_FLAG_STRIP) ~= 0 then
+    if bit.band(flags, FLAG_STRIP) ~= 0 then
         debugLen = read_uleb128(fp)
 
         -- TODO: is this correct?
diff --git a/tests/test2.lua b/tests/test2.lua
new file mode 100644
index 0000000..1506407
--- /dev/null
+++ b/tests/test2.lua
@@ -0,0 +1,4 @@
+local x = 1
+local y = 2
+local z = x^y
+return z
diff --git a/vm.lua b/vm.lua
index 8b13789..8379e25 100644
--- a/vm.lua
+++ b/vm.lua
@@ -1 +1,37 @@
+local opcodes = require('opcodes')
 
+local function set_proto(self, proto)
+    self.proto = proto
+end
+
+local function step(self)
+    if self.pc >= self.proto.numbc then
+        return false
+    end
+    local ins = self.proto.bcins[self.pc+1]
+    local decop = opcodes.decode(ins)
+    print(opcodes.defs[decop.id].name)
+
+    self.pc = self.pc + 1
+    return true
+end
+
+local function run(self)
+    while self:step() do
+    end
+end
+
+local VM = {
+    new = function()
+        return {
+            set_proto = set_proto,
+            step = step,
+            run =  run,
+            pc = 0,
+        }
+    end
+}
+
+return {
+    VM = VM
+}