holey-bytes/hbvm/src/lib.rs

144 lines
3.2 KiB
Rust

//! HoleyBytes Virtual Machine
//!
//! # Alloc feature
//! - Enabled by default
//! - Provides mapping / unmapping, as well as [`Default`] and [`Drop`]
//! implementations for soft-paged memory implementation
// # General safety notice:
// - Validation has to assure there is 256 registers (r0 - r255)
// - Instructions have to be valid as specified (values and sizes)
// - Mapped pages should be at least 4 KiB
#![no_std]
#![cfg_attr(feature = "nightly", feature(fn_align))]
#![deny(unsafe_op_in_unsafe_fn)]
#[cfg(feature = "alloc")]
extern crate alloc;
pub mod mem;
pub mod value;
mod bmc;
mod float;
mod utils;
mod vmrun;
pub use float::FL_ARCH_SPECIFIC_SUPPORTED;
use {
bmc::BlockCopier,
mem::{Address, Memory},
value::{Value, ValueVariant},
};
/// HoleyBytes Virtual Machine
pub struct Vm<Mem, const TIMER_QUOTIENT: usize> {
/// Holds 256 registers
///
/// Writing to register 0 is considered undefined behaviour
/// in terms of HoleyBytes program execution
pub registers: [Value; 256],
/// Memory implementation
pub memory: Mem,
/// Program counter
pub pc: Address,
/// Program timer
timer: usize,
/// Saved block copier
copier: Option<BlockCopier>,
}
impl<Mem, const TIMER_QUOTIENT: usize> Vm<Mem, TIMER_QUOTIENT>
where
Mem: Memory,
{
/// Create a new VM with program and trap handler
///
/// # Safety
/// Program code has to be validated
pub unsafe fn new(memory: Mem, entry: Address) -> Self {
Self {
registers: [Value::from(0_u64); 256],
memory,
pc: entry,
timer: 0,
copier: None,
}
}
/// Read register
#[inline(always)]
pub fn read_reg(&self, n: u8) -> Value {
unsafe { *self.registers.get_unchecked(n as usize) }
}
/// Write a register.
/// Writing to register 0 is no-op.
#[inline(always)]
pub fn write_reg<T: ValueVariant>(&mut self, n: u8, value: T) {
if n != 0 {
unsafe {
core::ptr::copy_nonoverlapping(
(&value as *const T).cast::<u8>(),
self.registers.as_mut_ptr().add(n.into()).cast::<u8>(),
core::mem::size_of::<T>(),
);
};
}
}
}
/// Virtual machine halt error
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
#[repr(u8)]
pub enum VmRunError {
/// Tried to execute invalid instruction
InvalidOpcode(u8),
/// Unhandled load access exception
LoadAccessEx(Address),
/// Unhandled instruction load access exception
ProgramFetchLoadEx(Address),
/// Unhandled store access exception
StoreAccessEx(Address),
/// Register out-of-bounds access
RegOutOfBounds,
/// Address out-of-bounds
AddrOutOfBounds,
/// Reached unreachable code
Unreachable,
/// Invalid operand
InvalidOperand,
/// Unimplemented feature
Unimplemented,
}
/// Virtual machine halt ok
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum VmRunOk {
/// Program has eached its end
End,
/// Program was interrupted by a timer
Timer,
/// Environment call
Ecall,
/// Breakpoint
Breakpoint,
}