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registerAssembler and registerGlobalDisassembleOverride

 
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mgr.inz.Player
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PostPosted: Thu Jun 26, 2014 4:13 pm    Post subject: registerAssembler and registerGlobalDisassembleOverride Reply with quote

based on this post:
http://forum.cheatengine.org/viewtopic.php?p=5539479#5539479

and this:
http://forum.cheatengine.org/viewtopic.php?p=5539482#5539482


I made script which will add those instructions to the assembler and disassembler:

- NOP 2, NOP 3, NOP 4, NOP 5, NOP 6, NOP 7, NOP 8, NOP 9, NOP 10, NOP 11. Those are multibyte NOPs.

- PADDING 4, PADDING 8, PADDING 16 - with those you can guarantee that next instruction will be placed at aligned address. (pad16 will guarantee address which ends with 0)


I mainly made below scripts to achieve PADDING thing, for example when you use movaps instructions, you want a memory operand aligned on a 16-byte boundary. It will pad out with NOP instructions and next available address will be aligned. http://www.winasm.net/forum/index.php?showtopic=2075


Just try to assemble "padding 16" (do it in single-line assembler) at address which ends with "1". It will generate two multibyte nops. Try also other addresses not 16-byte aligned (not ending with zero). The same way it will work for AA scripts.




Add this script to lua file in autorun folder:

Code:
-- initialize table
local NOP = {}
NOP[1]  =       {0x90}
NOP[2]  = {0x66, 0x90}
NOP[3]  = {      0x0F, 0x1F, 0x00}
NOP[4]  = {      0x0F, 0x1F, 0x40, 0x00}
NOP[5]  = {      0x0F, 0x1F, 0x44, 0x00, 0x00}
NOP[6]  = {0x66, 0x0F, 0x1F, 0x44, 0x00, 0x00}
NOP[7]  = {      0x0F, 0x1F, 0x80, 0x00, 0x00, 0x00, 0x00}
NOP[8]  = {      0x0F, 0x1F, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00}

NOP[9]  =             {0x66, 0x0F, 0x1F, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00}
NOP[10] =       {0x66, 0x66, 0x0F, 0x1F, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00}
NOP[11] = {0x66, 0x66, 0x66, 0x0F, 0x1F, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00}
for k,v in ipairs(NOP) do NOP[tostring(k)]=v end
for i=2,11 do NOP['concat'..i]=table.concat(NOP[i],'-') end

local function joinTables(t1,t2)
  local newT = {}
  for _,v in ipairs(t1) do newT[#newT+1] = v end
  for _,v in ipairs(t2) do newT[#newT+1] = v end
  return newT
end


function add_MULTINOP_and_PADDING(address, instruction)

   instruction = instruction:gsub("[^%w]",'')

   if instruction:sub(1,3):upper()=="NOP" then
    return NOP[instruction:sub(4,5)]
   end

   if instruction:upper()=="PADDING4" then
     return NOP[ 4-(address%4) ]
   end

   if instruction:upper()=="PADDING8" then
     return NOP[ 8-(address%8) ]
   end

   if instruction:upper()=="PADDING16" then
     local neededbytes =  16-(address%16)

     if neededbytes<12 then return NOP[ neededbytes ]
                       else return joinTables(NOP[11],NOP[neededbytes-11])
     end

   end
   return nil
end

function disassembleMultiNOP(sender, address, ldd)
  local bytes=readBytes(address, 11, true)

  if bytes==nil then return bytes end

  for i=11,2,-1 do
    if table.concat(bytes,'-',1,i)==NOP['concat'..i] then

      ldd.address=address
      ldd.opcode="nop"
      ldd.parameters=tostring(i)
      ldd.description="it is smartass multibyte nop, size (decimal) of this nop:"..i
      ldd.bytes=NOP[i]
      return ldd.opcode, ldd.description
    end
  end

  return nil,nil
end

registerAssembler(add_MULTINOP_and_PADDING)
registerGlobalDisassembleOverride(disassembleMultiNOP)

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