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Custom Improvement Proposals

With the release v19.0.0 a new feature called custom improvement proposals has been introduced in the evmOS framework. Custom improvement proposals allow protocol developers to modify the behavior of the EVM opcodes to tailor their functionalities to the specific needs.

Operations​

Operations are the base components of the Ethereum Virtual Machine (EVM) which allow the execution of the smart contract logic. When a developer builds a smart contract, the code written in Solidity, or Vyper, is not directly interpretable by the EVM. Before being able to execute the code in the blockchain, the contract has to be compiled via one of the available compilers, like solc. The compilation converts the human-readable contract code into a sequence of operations that the virtual machine can interpret and execute to perform state transitions or query the latest committed state. These operations are called opcodes, and are contained in a structure called jump table.

Each opcode is defined by specifying the logic that has to be executed when it is called inside the EVM, its relationship with the memory, and the gas cost associated with it. More specifically, an opcode is completely defined by:

  • SetExecute: update the execution logic for the opcode.

  • SetConstantGas: update the value used for the constant gas cost.

  • SetDynamicGas: update the function used to compute the dynamic gas cost.

  • SetMinStack: update the minimum number of items in the stack required to execute the operation.

  • SetMaxStack: update the maximum number of items that will be in the stack after executing the operation.

  • SetMemorySize: the memory size required by the operation.

Within the evmOS framework, developers can modify any of the previous properties.

Improvement Proposals​

Improvement proposals are the approach used by evmOS and Ethereum to modify the behavior of opcodes. They are composed of a function, which has access to the jump table to apply specific changes to operation behavior, and a name.

In the context of Ethereum, these protocol changes are named Ethereum Improvement Proposals (EIPs) and are identified by a unique ID. For example, EIP-1559 is used to introduce the base fee.

To allow any evmOS partner to define their own specific improvements without overlapping with evmOS and Ethereum ones, each proposal is identified by a string, that is composed of the chain name and a number. For example, default evmOS improvements are associated with the string evmos_XXXX. This allows each chain to define their improvements without having to worry about existing or future ID clashes between different chains. Additionally, the ability to start enumeration at 0 is better for chain developers and allows having a better overview of the historical progress for each chain.

Below, you will find an example of how the Evmos chain uses this functionality to modify the behavior of the CREATE and CREATE2 opcodes. First, the modifier function has to be defined:

// Enable0000 contains the logic to modify the CREATE and CREATE2 opcodes
// constant gas value.
func Enable0000(jt *vm.JumpTable) {
    multiplier := 10

    currentValCreate := jt[vm.CREATE].GetConstantGas()
    jt[vm.CREATE].SetConstantGas(currentValCreate * multiplier)

    currentValCreate2 := jt[vm.CREATE2].GetConstantGas()
    jt[vm.CREATE2].SetConstantGas(currentValCreate2 * multiplier)
}

Then, the function as to be associated with a name via a custom activator:

evmosActivators = map[string]func(*vm.JumpTable){
    "evmos_0": eips.Enable0000,
}

Activation of Improvement Proposals​

Due to continuous changes in the users' interaction with the protocol, and to introduce a safety measure along with the freedom to customize the virtual machine behavior, custom improvement proposals are not active by default. The activation of selected improvement proposals is controlled by the EVM module's parameters. There are two ways of introducing the required parameter changes:

  1. Upgrade: create a protocol upgrade handler which introduces the proposal name in the active list.

  2. Governance: create governance proposal to add an improvement proposal to the EVM module parameters.

This approach gives developers the ability to react to security issues or market conditions, while keeping the chain's participants in the loop.

Additional Resources​

  1. Evmos Custom EIPs: please refer to this document for a detailed description of how opcodes and custom improvement proposals have to be used in the evmOS framework.