lib/bc.lua

   1 ----------------------------------------------------------------------------
   2 -- LuaJIT bytecode listing module.
   3 --
   4 -- Copyright (C) 2005-2011 Mike Pall. All rights reserved.
   5 -- Released under the MIT license. See Copyright Notice in luajit.h
   6 ----------------------------------------------------------------------------
   7 --
   8 -- This module lists the bytecode of a Lua function. If it's loaded by -jbc
   9 -- it hooks into the parser and lists all functions of a chunk as they
  10 -- are parsed.
  11 --
  12 -- Example usage:
  13 --
  14 --   luajit -jbc -e 'local x=0; for i=1,1e6 do x=x+i end; print(x)'
  15 --   luajit -jbc=- foo.lua
  16 --   luajit -jbc=foo.list foo.lua
  17 --
  18 -- Default output is to stderr. To redirect the output to a file, pass a
  19 -- filename as an argument (use '-' for stdout) or set the environment
  20 -- variable LUAJIT_LISTFILE. The file is overwritten every time the module
  21 -- is started.
  22 --
  23 -- This module can also be used programmatically:
  24 --
  25 --   local bc = require("jit.bc")
  26 --
  27 --   local function foo() print("hello") end
  28 --
  29 --   bc.dump(foo)           --> -- BYTECODE -- [...]
  30 --   print(bc.line(foo, 2)) --> 0002    KSTR     1   1      ; "hello"
  31 --
  32 --   local out = {
  33 --     -- Do something with each line:
  34 --     write = function(t, ...) io.write(...) end,
  35 --     close = function(t) end,
  36 --     flush = function(t) end,
  37 --   }
  38 --   bc.dump(foo, out)
  39 --
  40 ------------------------------------------------------------------------------
  41
  42 -- Cache some library functions and objects.
  43 local jit = require("jit")
  44 assert(jit.version_num == 20000, "LuaJIT core/library version mismatch")
  45 local jutil = require("jit.util")
  46 local vmdef = require("jit.vmdef")
  47 local bit = require("bit")
  48 local sub, gsub, format = string.sub, string.gsub, string.format
  49 local byte, band, shr = string.byte, bit.band, bit.rshift
  50 local funcinfo, funcbc, funck = jutil.funcinfo, jutil.funcbc, jutil.funck
  51 local funcuvname = jutil.funcuvname
  52 local bcnames = vmdef.bcnames
  53 local stdout, stderr = io.stdout, io.stderr
  54
  55 ------------------------------------------------------------------------------
  56
  57 local function ctlsub(c)
  58   if c == "\n" then return "\\n"
  59   elseif c == "\r" then return "\\r"
  60   elseif c == "\t" then return "\\t"
  61   elseif c == "\r" then return "\\r"
  62   else return format("\\%03d", byte(c))
  63   end
  64 end
  65
  66 -- Return one bytecode line.
  67 local function bcline(func, pc, prefix)
  68   local ins, m = funcbc(func, pc)
  69   if not ins then return end
  70   local ma, mb, mc = band(m, 7), band(m, 15*8), band(m, 15*128)
  71   local a = band(shr(ins, 8), 0xff)
  72   local oidx = 6*band(ins, 0xff)
  73   local op = sub(bcnames, oidx+1, oidx+6)
  74   local s = format("%04d %s %-6s %3s ",
  75     pc, prefix or "  ", op, ma == 0 and "" or a)
  76   local d = shr(ins, 16)
  77   if mc == 13*128 then -- BCMjump
  78     return format("%s=> %04d\n", s, pc+d-0x7fff)
  79   end
  80   if mb ~= 0 then
  81     d = band(d, 0xff)
  82   elseif mc == 0 then
  83     return s.."\n"
  84   end
  85   local kc
  86   if mc == 10*128 then -- BCMstr
  87     kc = funck(func, -d-1)
  88     kc = format(#kc > 40 and '"%.40s"~' or '"%s"', gsub(kc, "%c", ctlsub))
  89   elseif mc == 9*128 then -- BCMnum
  90     kc = funck(func, d)
  91     if op == "TSETM " then kc = kc - 2^52 end
  92   elseif mc == 12*128 then -- BCMfunc
  93     local fi = funcinfo(funck(func, -d-1))
  94     if fi.ffid then
  95       kc = vmdef.ffnames[fi.ffid]
  96     else
  97       kc = fi.loc
  98     end
  99   elseif mc == 5*128 then -- BCMuv
 100     kc = funcuvname(func, d)
 101   end
 102   if ma == 5 then -- BCMuv
 103     local ka = funcuvname(func, a)
 104     if kc then kc = ka.." ; "..kc else kc = ka end
 105   end
 106   if mb ~= 0 then
 107     local b = shr(ins, 24)
 108     if kc then return format("%s%3d %3d  ; %s\n", s, b, d, kc) end
 109     return format("%s%3d %3d\n", s, b, d)
 110   end
 111   if kc then return format("%s%3d      ; %s\n", s, d, kc) end
 112   if mc == 7*128 and d > 32767 then d = d - 65536 end -- BCMlits
 113   return format("%s%3d\n", s, d)
 114 end
 115
 116 -- Collect branch targets of a function.
 117 local function bctargets(func)
 118   local target = {}
 119   for pc=1,1000000000 do
 120     local ins, m = funcbc(func, pc)
 121     if not ins then break end
 122     if band(m, 15*128) == 13*128 then target[pc+shr(ins, 16)-0x7fff] = true end
 123   end
 124   return target
 125 end
 126
 127 -- Dump bytecode instructions of a function.
 128 local function bcdump(func, out, all)
 129   if not out then out = stdout end
 130   local fi = funcinfo(func)
 131   if all and fi.children then
 132     for n=-1,-1000000000,-1 do
 133       local k = funck(func, n)
 134       if not k then break end
 135       if type(k) == "proto" then bcdump(k, out, true) end
 136     end
 137   end
 138   out:write(format("-- BYTECODE -- %s-%d\n", fi.loc, fi.lastlinedefined))
 139   local target = bctargets(func)
 140   for pc=1,1000000000 do
 141     local s = bcline(func, pc, target[pc] and "=>")
 142     if not s then break end
 143     out:write(s)
 144   end
 145   out:write("\n")
 146   out:flush()
 147 end
 148
 149 ------------------------------------------------------------------------------
 150
 151 -- Active flag and output file handle.
 152 local active, out
 153
 154 -- List handler.
 155 local function h_list(func)
 156   return bcdump(func, out)
 157 end
 158
 159 -- Detach list handler.
 160 local function bclistoff()
 161   if active then
 162     active = false
 163     jit.attach(h_list)
 164     if out and out ~= stdout and out ~= stderr then out:close() end
 165     out = nil
 166   end
 167 end
 168
 169 -- Open the output file and attach list handler.
 170 local function bcliston(outfile)
 171   if active then bclistoff() end
 172   if not outfile then outfile = os.getenv("LUAJIT_LISTFILE") end
 173   if outfile then
 174     out = outfile == "-" and stdout or assert(io.open(outfile, "w"))
 175   else
 176     out = stderr
 177   end
 178   jit.attach(h_list, "bc")
 179   active = true
 180 end
 181
 182 -- Public module functions.
 183 module(...)
 184
 185 line = bcline
 186 dump = bcdump
 187 targets = bctargets
 188
 189 on = bcliston
 190 off = bclistoff
 191 start = bcliston -- For -j command line option.
 192