EVM lab utilities

This package contains various tools to interact with the Ethereum virtual machine.

Compiler

The 'compiler' is a tool to build evm binaries, using a pythonic way to construct the programs using assembly.

Here's an example that tests ecdsaRecover:

	p = compiler.Program()
	p.mstore(0 ,0x38d18acb67d25c8bb9942764b62f18e17054f66a817bd4295423adf9ed98873e)
	v = 0x000000000000000000000000000000000000000000000000000000000000001b
	p.mstore(32   , v)
	p.mstore(64   ,0x723841761d213b60ac1cbf063207cbeba6c2725bcaf7c189e63f13d93fc1dc07)
	p.mstore(96   ,0x789d1dd423d25f0772d2748d60f7e4b81bb14d086eba8e8e8efb6dcff8a4ae02)
	p.call(0xfff,1,0,0,0x80,0x80,0x20)
	p.rreturn(140,20)
	code = p.bytecode()

Here's an example of stuffing JUMPDEST into a program:

	p = compiler.Program()
	p.jump(0x3)
	p.jumpdest()
	p.rreturn()
	for i in range(0,20000):
		p.op(JUMPDEST)

	return p.bytecode()

Gethvm

The gethvm provides some ability to execute the evm from geth. Example:

     vm = gethvm.VM(evmbin)
     output =  vm.execute(code = bootstrap, genesis = g_path, json = True)

Etherchain

The etherchain package contains an API for interacting with the Etherchain API.

Reproduce

An example app is reproduce.py which can reproduce an on-chain transaction as a totally local event, and run it in the evm.

The app takes a txhash, and

1. Fetch the transaction data from an API.
2. Mark (source, destination) as need-to-fetch
3. Fetch balance and nonce at source, add to genesis
4. Execute transaction on the evm
5. If transaction has any externally reaching ops (BALANCE, EXTCODECOPY, CALL etc),

• Add those accounts as need-to-fetch

6. Go back to 3 until the execution does not result in any more accounts to be fetched.
7. Save the transaction trace and genesis

EVM

EVM format

Here's what to think about if you want to add an evm to evmlab.

Input

The evm should take the following inputs:

• --code <code> - code to be executed.
• --codeFile <file> - file containing code to be executed. Sometimes really large chunks of input cannot be passed through bash.
• --gas <int>
• --price <int>
• --sender <address> - address of ORIGIN
• --receiver <address - address of ADDRESS
• --input <code> : CALLDATA
• --value <int>
• --json - boolean flag, output json output for each opcode or not (it's useful to disable json when benchmarking)
• --nomemory - disable showing the full memory output for each op
• --create - if specified, it's executed as initcode
• --prestate - a chain specification, the same one that the client normally would use.

Basically, the evm should be able to run things very simply, like so:

$evm --code 6040 --json run
{"pc":0,"op":96,"gas":"0x2540be400","gasCost":"0x3","memory":"0x","memSize":0,"stack":[],"depth":1,"error":null,"opName":"PUSH1"}
{"pc":2,"op":0,"gas":"0x2540be3fd","gasCost":"0x0","memory":"0x","memSize":0,"stack":["0x40"],"depth":1,"error":null,"opName":"STOP"}
{"output":"","gasUsed":"0x3","time":141485}

But it should also be able to reconstruct an actual on-chain transaction, with complex options including prestate, where no code is passed, since it's already been showed into the prestate:

$evm --prestate /home/martin/workspace/evmlab/output//0xd6d519-genesis-geth_wq38zsy5.json --gas 150000 --sender 0x69ea6b31ef305d6b99bb2d4c9d99456fa108b02a --receiver 0xb97048628db6b661d4c2aa833e95dbe1a905b280 --input a9059cbb0000000000000000000000008eef795fd9150f118bddeca556a5a2a2438ab865000000000000000000000000000000000000000000000081ebd8ffd6b2a58000 --json run

Output

The evm should output a json object for each operation. Example:

{"pc":0,"op":96,"gas":"0x2540be400","gasCost":"0x3","memory":"0x","memSize":0,"stack":[],"depth":1,"error":null,"opName":"PUSH1"}

Required: pc, op, gas, stack, depth Optional: opName, gasCost, error

The stack, memory and memSize are the values before execution of the op.

At the end of execution, some summarical info is good, e.g.

{"output":"","gasUsed":"0x3","time":141485}

When errors occur, geth and parity handles them differently.

Minor changes to how things work is ok, we can handle discrepancies in format and minor quirks.

Opviewer

The 'opviewer.py' is a simple debugger-like trace-viewer. It can be used against an evm-trace and navigate the data in a bit more friendly manner than raw json. Invoke via e.g. python opviewer.py -f example2.json