Proposal Wasm Env for ETH 2.0

Introduction

This project describes a proposal for simpler option than the current scout to create the wasm state transition function for phase 2 of ethereum 2.0. The project implements a compilation of the proposed function from the languages c and rust and a call to the built wasm from languages java script and golang.

Project Content

Path	Description
create_wasm_from_c	build wasm from c source
create_wasm_from_rust	build wasm from rust source
call_from_golang	execution and testing of wasm files from go
call_from_javascript	execution and testing of wasm files from java script
test_cases	common set of test cases for all programming languages
do_it_all.sh	the script that sequentially builds a program and runs its testing
readme.md	proposal text

Description

The wasm module will have only two exports:

• Memory

   (memory $memory 256)
   (export  "memory" (memory  0))

• Transition function

   (type  (;0;) (func (param  i32) (result  i32)))
   (export  "transition" (func  0))

And will not have imports.

Thus, the wasm code will have a smaller size, their speed will be higher, and the programs calling it will be easier.

All incoming parameters (pre_stata and block_data) are initiated in the module memory before the transition function is called. The results of the transition function (post_state and deposits) are also recorded in the module wasm memory, and can be read from it by the calling (host) program. If the transition function decides to report an error, then it must return a code other than zero.

How to call

1. Load wasm module from blockchain (file for test)
2. Initialize the memory of the module (write pre_stata and block_data to memory)
3. Call the wasm function "transition"
4. Read the memory of the module (read post_state and deposits from memory)

Memory structure

Address (Bytes)	Name	Direction	How the owner initiates before calling the transition function	What are the values after calling the function
0..31	preState	In	preState	undefined
32..63	postState	Out	preState	postState
64..67	depositCount	Out	0	deposit count
68..71	depositsPtr	Out	Indicates position after block data. May be changed in the transition function	deposits pointer
72..75	blockSize	In	Size of block	undefined
76..76+blockSize	block	In	Size of block	undefined
76+len(block)..76+blockSize+depositCount*104	deposits	Out	undefined	By default, the transition function writes deposit data here. But the place can be changed through change depositsPtr

Deposit structure:

Address (Bytes)	Name
0..47	pubKey
47..95	withdrawalCredentials
96..103	amount

Are we trying?

alex:~/ewasm$ ./do_it_all.sh 

============build from c=============
wasm size: 255

===========build from rust===========
   Compiling transition v0.0.0 (/home/alex/ewasm/build_from_rust)
    Finished release [optimized] target(s) in 0.46s
wasm size: 94959

========test call from golang========
INFO[0000] wasm return error code 1                      prefix=ewasm
INFO[0000] wasm return error code 1                      prefix=ewasm
PASS
ok  	_/home/alex/ewasm/call_from_golang	0.026s

======test call from javascript======
> [email protected] test /home/alex/ewasm/call_from_javascript
> mocha

  if the block is not specified, an error is returned
exit code 1
    ✓ transition_c.wasm
exit code 1
    ✓ transition_rust.wasm

  check deposits reading
    ✓ transition_c.wasm
    ✓ transition_rust.wasm

  check postState manipulation
    ✓ transition_c.wasm
    ✓ transition_rust.wasm

  check postState manipulation 2
    ✓ transition_c.wasm
    ✓ transition_rust.wasm


  8 passing (44ms)

PS

Maintainer

Alex Nebotov

Let me know if something didn't work for you. I am happy to modify the script or instruction.

What lies ahead:

1. wasm code for ETH transfer
2. define the gas calculation
3. can wasm modules call other modules? How to send and receive parameters?
4. define the WASM validation:

• wasm version
• memory requirements
• remove non-deterministic operations