HAssembly-evm =============

EVM (Ethereum virtual machine) Assembly on Haskell DSL

This is a bytecode generator from EVM assembly on Haskell DSL.

Warning: * A big WIP * No guarantee and under testing * Experimental and conceptual project

Feature: * Composable assembly * User definable functions * Purely functional implementation * Simple and slow implementation for readability * Only a few dependent libraries and GHC extensions

Limitation: * Weak error detection and cheap error implementation * Jump size is limited to 2 bytes

Run

Command:

GHC: * $ runghc -isrc app/Main.hs

Stack: * $ stack runghc -- -isrc app/Main.hs or * $ stack build; stack exec hassembly-evm

Cabal: * $ cabal run

Example:

$ runghc -isrc app/Main.hs
  601060200100

Code example

Basic:

main :: IO ()
  main = putStrLn $ codegen prog1
prog1 :: EvmAsm   prog1 = do       push1 0x10       push1 0x20       add

Composable:

prog2 :: EvmAsm
  prog2 = do
      prog2a
      prog2b
prog2a = do       push1 0x40       mload
prog2b = do       push1 0x20       add

Pseudo instruction and built-in function:

* dest : pseudo instruction for jump destination (jump and _jumpi) * label : pseudo instruction for push with symbol (pushlabel) * jump and jumpi : jump instruction with symbol * _pushlabel : push instruction with symbol * _push : push instruction with automatic length adjustment * _raw : pseudo instruction for raw byte * _progSize : built-in function for program size * _genUniqLabel : built-in function to generate unique label

prog3 :: EvmAsm
  prog3 = do
      push1 0x60
      push1 0x40
      mstore
      _jump "target2"            -- symbol jump
push1 (_progSize prog4)    -- program size       _pushlabel "top1"          -- push label       _dest "target2"            -- jump target
prog4 :: EvmAsm   prog4 = do       _label "top1"              -- label       _push 0x11234456788        -- multi length push       _raw 0x7                   -- raw byte       _raw 0x8

Using host language (Haskell):

prog5 = do
      if isBizantinum          -- if expression on Haskell
          then prog_header1
          else prog_header2
      push1 0x60
      push1 0x40
      mstore

User defined functions and syntax:

shiftL nbit = do    -- user defined function
      push1 nbit
      push1 2
      exp
      mul
prog6 = do       mload       shiftL 16    -- using       push1 0x1       add
string "OK" >> log1

Example2: (examples/userSyntax.hs)

prog7 = do
      let num1 = const 0x10      -- let syntax
      let num2 = const 0x20
      let factor1 = ptr 0x05     -- memory type
      let user1   = key 0x100    -- storage type
add2(num1, num2)           -- functional syntax       add2(ref factor1, num1)       add       add2(value user1, const 3)       memory(factor1) <== mul    -- assignment syntax
storage(user1) <== mul2(num2, (add2(const 4, ref factor1)))

Example3: (examples/userFlow.hs)

prog8 = do
      _if (iszero) (do -- then
            push1 0x01
            push1 0x02
            add
        ) (do -- else
            push1 0x01
            push1 0x02
            sub
        )

Execute bytecode

If you need to execute a generated bytecode, please use the evm command of go-ethereum project or some tools.

Execute bytecode by evm command:

$ evm --code "601060200100" --debug run

$ evm disasm sample.bytecode

Listing and pretty printing

Simple listing:

Use pprList function:

main :: IO ()
  main = putStrLn $ pprList prog1   -- using pprList
prog1 :: EvmAsm   prog1 = do ...

Output example:

$ runghc -isrc examples/pprList.hs
  000000: push1 0x10
  000002: push1 0x20
  000004: add
  000005: stop

Under implementation ...

Pretty-print for Solidity:

$ runghc -isrc examples/PprSol.hs
  {
      0x10
      0x20
      add
      stop
      pop
  }

Stack hight checking:

$ runghc -isrc examples/StackCheck.hs
  Final stack-hight: 0

See also

* Ethereum Yellow Paper * Go Ethereum * The Solidity Contract-Oriented Programming Language * Ethereum EVM illustrated