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