Architecture

Overview

lessVM is a stack-based virtual machine designed specifically for the Solana blockchain. It features a simple instruction set with stack manipulation, arithmetic operations, memory access, control flow, and Solana-specific operations.

Core Components

Stack

#[repr(C, align(64))]
struct Stack {
    data: [Value; 32],
    top: usize,
}

→ 32 entries deep
→ 64-bit values
→ LIFO (Last In, First Out)
→ Overflow protection

Memory

#[repr(C, align(64))]
struct Memory {
    data: [u8; 1024],
    size: usize,
}

→ 1024 bytes linear memory
→ Bounds checking
→ Zero-initialized
→ Memory expansion tracking

Gas Metering

struct GasConfig {
    base_cost: u64,
    memory_cost: u64,
    solana_op_cost: u64,
    spl_op_cost: u64,
    cpi_cost: u64,
    gas_limit: u64,
}

→ Operation-based costs
→ Memory expansion costs
→ CPI operation costs
→ Gas limit enforcement

Program Counter

struct VM {
    pc: usize,
    code: &[u8],
    // ...
}

→ Instruction pointer
→ Sequential execution
→ Jump validation
→ Bounds checking

Security Features

Memory Safety

→ Stack overflow protection
→ Memory bounds checking
→ Zero-initialized memory

Account Safety

→ Account ownership verification
→ Write permission checks
→ Lamport balance checks

Execution Safety

→ Gas metering
→ Jump target validation
→ CPI depth tracking