evm

components

vm/: code for the evm interpreter as/: code for an easm assembler (you can also use evm compile if you have geth installed)

building

you can build individual go modules like usual

cd vm & go build
cd ../as & go build

you can also use the makefile to build all of the modules, and run the test of your choice

TEST=test/add.easm make clean test      # don't need to specify add.easm, it is the default test

as

you can assemble files by specifying the assembly file, and optionally the name of your output binary using the -o flag

./as/as test/add.easm -o test/add.bin

if you want to compare the output with something like the evm tool from geth, you can use xxd with the -p flag

evm compile test/add.easm
xxd -p test/add.bin

vm

running bytecode:

./vm/evm test/add.bin

programming

right now, only a small subset of evm opcodes are supported, and there is no support for calldata, storage, branching, gas fees and much more

the only instruction that takes a parameter is the PUSH instruction. It will take the specified sub 256b number in hex or decimal format, and push it onto the stack.

PUSH 4 # pushes the value 4 to the stack

this PUSH instruction is then used to pass values into other instructions

PUSH 4
PUSH 9
ADD

the result of this ADD instruction (13) will then be pushed to the stack

if you need more info on some operations, check the opcode reference

if you want your program to return some data, you first need store it in memory. Then you push the offset and length (in bytes) of this memory to the stack, and use the return instruction

PUSH 9
PUSH 4
ADD
PUSH 3  // the offset for MSTORE8
MSTORE8 // the value we want to store is already on the stack after the ADD instruction
PUSH 1  // the size in bytes of our return data
PUSH 3  // offset again
RETURN 

how does this connect to the ethereum network

• nodes on the ethereum network will take in similiar bytecode, in addition to persistent contract storage, account state, world state, call data, and much more
• modifications to the state of the ethereum blockchain are verified, usually by comparing the root of hash trees computed by nodes

more notes

• solidity does its own thing, and has its own abi and runtime
• easm is slow and suffers from serious design issues, so ethereum devs want to move to wasm.