forked from AbleOS/holey-bytes
Abstraction of memory
This commit is contained in:
parent
2aad3a1002
commit
1e92797775
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@ -26,12 +26,12 @@ use {
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hbbytecode::{
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valider, OpParam, ParamBB, ParamBBB, ParamBBBB, ParamBBD, ParamBBDH, ParamBBW, ParamBD,
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},
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mem::{bmc::BlockCopier, HandlePageFault, Memory},
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mem::bmc::BlockCopier,
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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<'a, PfHandler, const TIMER_QUOTIENT: usize> {
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pub struct Vm<'a, Memory, 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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@ -41,9 +41,6 @@ pub struct Vm<'a, PfHandler, const TIMER_QUOTIENT: usize> {
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/// Memory implementation
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pub memory: Memory,
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/// Trap handler
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pub pfhandler: PfHandler,
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/// Program counter
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pub pc: usize,
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@ -63,18 +60,18 @@ pub struct Vm<'a, PfHandler, const TIMER_QUOTIENT: usize> {
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copier: Option<BlockCopier>,
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}
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impl<'a, PfHandler: HandlePageFault, const TIMER_QUOTIENT: usize>
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Vm<'a, PfHandler, TIMER_QUOTIENT>
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impl<'a, Memory, const TIMER_QUOTIENT: usize> Vm<'a, Memory, TIMER_QUOTIENT>
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where
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Memory: 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_unchecked(program: &'a [u8], traph: PfHandler, memory: Memory) -> Self {
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pub unsafe fn new_unchecked(program: &'a [u8], memory: Memory) -> 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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pfhandler: traph,
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pc: 0,
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program_len: program.len() - 12,
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program: program[4..].as_ptr(),
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@ -85,13 +82,9 @@ impl<'a, PfHandler: HandlePageFault, const TIMER_QUOTIENT: usize>
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}
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/// Create a new VM with program and trap handler only if it passes validation
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pub fn new_validated(
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program: &'a [u8],
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traph: PfHandler,
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memory: Memory,
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) -> Result<Self, valider::Error> {
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pub fn new_validated(program: &'a [u8], memory: Memory) -> Result<Self, valider::Error> {
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valider::validate(program)?;
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Ok(unsafe { Self::new_unchecked(program, traph, memory) })
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Ok(unsafe { Self::new_unchecked(program, memory) })
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}
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/// Execute program
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@ -250,7 +243,6 @@ impl<'a, PfHandler: HandlePageFault, const TIMER_QUOTIENT: usize>
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.add(usize::from(dst) + usize::from(n))
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.cast(),
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usize::from(count).saturating_sub(n.into()),
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&mut self.pfhandler,
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)?;
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}
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ST => {
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@ -260,14 +252,13 @@ impl<'a, PfHandler: HandlePageFault, const TIMER_QUOTIENT: usize>
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self.ldst_addr_uber(dst, base, off, count, 0)?,
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self.registers.as_ptr().add(usize::from(dst)).cast(),
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count.into(),
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&mut self.pfhandler,
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)?;
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}
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BMC => {
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// Block memory copy
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match if let Some(copier) = &mut self.copier {
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// There is some copier, poll.
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copier.poll(&mut self.memory, &mut self.pfhandler)
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copier.poll(&mut self.memory)
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} else {
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// There is none, make one!
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let ParamBBD(src, dst, count) = self.decode();
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@ -284,7 +275,7 @@ impl<'a, PfHandler: HandlePageFault, const TIMER_QUOTIENT: usize>
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self.copier
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.as_mut()
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.unwrap_unchecked() // SAFETY: We just assigned there
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.poll(&mut self.memory, &mut self.pfhandler)
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.poll(&mut self.memory)
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} {
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// We are done, shift program counter
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core::task::Poll::Ready(Ok(())) => {
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@ -1,9 +1,8 @@
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use hbvm::mem::softpaged::{HandlePageFault, PageSize, SoftPagedMem};
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use {
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hbbytecode::valider::validate,
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hbvm::{
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mem::{HandlePageFault, Memory, MemoryAccessReason, PageSize},
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Vm,
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},
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hbvm::{mem::MemoryAccessReason, Vm},
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std::io::{stdin, Read},
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};
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@ -16,7 +15,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
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return Ok(());
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} else {
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unsafe {
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let mut vm = Vm::<_, 0>::new_unchecked(&prog, TestTrapHandler, Default::default());
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let mut vm =
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Vm::<_, 0>::new_unchecked(&prog, SoftPagedMem::<TestTrapHandler>::default());
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let data = {
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let ptr = std::alloc::alloc_zeroed(std::alloc::Layout::from_size_align_unchecked(
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4096, 4096,
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@ -31,7 +31,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
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.map(
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data,
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0,
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hbvm::mem::paging::Permission::Write,
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hbvm::mem::softpaged::paging::Permission::Write,
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PageSize::Size4K,
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)
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.unwrap();
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@ -54,12 +54,13 @@ pub fn time() -> u32 {
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9
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}
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#[derive(Default)]
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struct TestTrapHandler;
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impl HandlePageFault for TestTrapHandler {
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fn page_fault(
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&mut self,
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_: MemoryAccessReason,
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_: &mut Memory,
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//_: &mut Memory,
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_: u64,
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_: PageSize,
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_: *mut u8,
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@ -1,9 +1,6 @@
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use {
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super::MemoryAccessReason,
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crate::{
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mem::{HandlePageFault, Memory},
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VmRunError,
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},
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crate::{mem::Memory, VmRunError},
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core::{mem::MaybeUninit, task::Poll},
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};
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@ -40,11 +37,7 @@ impl BlockCopier {
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///
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/// # Safety
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/// - Same as for [`Memory::load`] and [`Memory::store`]
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pub unsafe fn poll(
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&mut self,
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memory: &mut Memory,
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traph: &mut impl HandlePageFault,
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) -> Poll<Result<(), BlkCopyError>> {
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pub unsafe fn poll(&mut self, memory: &mut impl Memory) -> Poll<Result<(), BlkCopyError>> {
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// Safety: Assuming uninit of array of MaybeUninit is sound
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let mut buf = AlignedBuf(MaybeUninit::uninit().assume_init());
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@ -56,7 +49,6 @@ impl BlockCopier {
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self.dst,
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buf.0.as_mut_ptr().cast(),
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BUF_SIZE,
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traph,
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) {
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return Poll::Ready(Err(e));
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}
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@ -92,7 +84,6 @@ impl BlockCopier {
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self.dst,
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buf.0.as_mut_ptr().cast(),
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self.rem,
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traph,
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) {
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return Poll::Ready(Err(e));
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}
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@ -104,16 +95,15 @@ impl BlockCopier {
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#[inline]
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unsafe fn act(
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memory: &mut Memory,
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memory: &mut impl Memory,
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src: u64,
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dst: u64,
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buf: *mut u8,
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count: usize,
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traph: &mut impl HandlePageFault,
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) -> Result<(), BlkCopyError> {
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// Load to buffer
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memory
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.load(src, buf, count, traph)
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.load(src, buf, count)
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.map_err(|super::LoadError(addr)| BlkCopyError::Access {
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access_reason: MemoryAccessReason::Load,
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addr,
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@ -121,7 +111,7 @@ unsafe fn act(
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// Store from buffer
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memory
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.store(dst, buf, count, traph)
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.store(dst, buf, count)
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.map_err(|super::StoreError(addr)| BlkCopyError::Access {
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access_reason: MemoryAccessReason::Store,
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addr,
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@ -1,426 +1,27 @@
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//! Program memory implementation
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pub mod bmc;
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pub mod paging;
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pub mod softpaged;
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mod pfhandler;
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use {super::VmRunError, derive_more::Display};
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pub use pfhandler::HandlePageFault;
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use {
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super::VmRunError,
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derive_more::Display,
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paging::{PageTable, Permission},
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};
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#[cfg(feature = "alloc")]
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use {alloc::boxed::Box, paging::PtEntry};
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/// HoleyBytes virtual memory
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#[derive(Clone, Debug)]
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pub struct Memory {
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/// Root page table
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pub root_pt: *mut PageTable,
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}
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#[cfg(feature = "alloc")]
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impl Default for Memory {
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fn default() -> Self {
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Self {
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root_pt: Box::into_raw(Default::default()),
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}
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}
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}
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#[cfg(feature = "alloc")]
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impl Drop for Memory {
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fn drop(&mut self) {
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let _ = unsafe { Box::from_raw(self.root_pt) };
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}
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}
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impl Memory {
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/// Maps host's memory into VM's memory
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pub trait Memory {
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/// Load data from memory on address
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///
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/// # Safety
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/// - Your faith in the gods of UB
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/// - Addr-san claims it's fine but who knows is she isn't lying :ferrisSus:
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/// - Alright, Miri-sama is also fine with this, who knows why
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#[cfg(feature = "alloc")]
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pub unsafe fn map(
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&mut self,
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host: *mut u8,
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target: u64,
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perm: Permission,
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pagesize: PageSize,
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) -> Result<(), MapError> {
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let mut current_pt = self.root_pt;
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/// - Shall not overrun the buffer
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unsafe fn load(&mut self, addr: u64, target: *mut u8, count: usize) -> Result<(), LoadError>;
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// Decide on what level depth are we going
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let lookup_depth = match pagesize {
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PageSize::Size4K => 0,
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PageSize::Size2M => 1,
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PageSize::Size1G => 2,
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};
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// Walk pagetable levels
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for lvl in (lookup_depth + 1..5).rev() {
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let entry = (*current_pt)
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.table
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.get_unchecked_mut(addr_extract_index(target, lvl));
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let ptr = entry.ptr();
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match entry.permission() {
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// Still not on target and already seeing empty entry?
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// No worries! Let's create one (allocates).
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Permission::Empty => {
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// Increase children count
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(*current_pt).childen += 1;
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let table = Box::into_raw(Box::new(paging::PtPointedData {
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pt: PageTable::default(),
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}));
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core::ptr::write(entry, PtEntry::new(table, Permission::Node));
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current_pt = table as _;
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}
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// Continue walking
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Permission::Node => current_pt = ptr as _,
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// There is some entry on place of node
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_ => return Err(MapError::PageOnNode),
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}
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}
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let node = (*current_pt)
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.table
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.get_unchecked_mut(addr_extract_index(target, lookup_depth));
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// Check if node is not mapped
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if node.permission() != Permission::Empty {
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return Err(MapError::AlreadyMapped);
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}
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// Write entry
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(*current_pt).childen += 1;
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core::ptr::write(node, PtEntry::new(host.cast(), perm));
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Ok(())
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}
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/// Unmaps pages from VM's memory
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///
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/// If errors, it only means there is no entry to unmap and in most cases
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/// just should be ignored.
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#[cfg(feature = "alloc")]
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pub fn unmap(&mut self, addr: u64) -> Result<(), NothingToUnmap> {
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let mut current_pt = self.root_pt;
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let mut page_tables = [core::ptr::null_mut(); 5];
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// Walk page table in reverse
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for lvl in (0..5).rev() {
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let entry = unsafe {
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(*current_pt)
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.table
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.get_unchecked_mut(addr_extract_index(addr, lvl))
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};
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let ptr = entry.ptr();
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match entry.permission() {
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// Nothing is there, throw an error, not critical!
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Permission::Empty => return Err(NothingToUnmap),
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// Node – Save to visited pagetables and continue walking
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Permission::Node => {
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page_tables[lvl as usize] = entry;
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current_pt = ptr as _
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}
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// Page entry – zero it out!
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// Zero page entry is completely valid entry with
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// empty permission - no UB here!
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_ => unsafe {
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core::ptr::write_bytes(entry, 0, 1);
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break;
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},
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}
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}
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// Now walk in order visited page tables
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for entry in page_tables.into_iter() {
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// Level not visited, skip.
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if entry.is_null() {
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continue;
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}
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unsafe {
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let children = &mut (*(*entry).ptr()).pt.childen;
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*children -= 1; // Decrease children count
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// If there are no children, deallocate.
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if *children == 0 {
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let _ = Box::from_raw((*entry).ptr() as *mut PageTable);
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// Zero visited entry
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core::ptr::write_bytes(entry, 0, 1);
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} else {
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break;
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}
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}
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}
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Ok(())
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}
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/// Load value from an address
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/// Store data to memory on address
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///
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/// # Safety
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/// Applies same conditions as for [`core::ptr::copy_nonoverlapping`]
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pub unsafe fn load(
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&mut self,
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addr: u64,
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target: *mut u8,
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count: usize,
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traph: &mut impl HandlePageFault,
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) -> Result<(), LoadError> {
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self.memory_access(
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MemoryAccessReason::Load,
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addr,
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target,
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count,
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perm_check::readable,
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|src, dst, count| core::ptr::copy_nonoverlapping(src, dst, count),
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traph,
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)
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.map_err(LoadError)
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}
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/// Store value to an address
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///
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/// # Safety
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/// Applies same conditions as for [`core::ptr::copy_nonoverlapping`]
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pub unsafe fn store(
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/// - Shall not overrun the buffer
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unsafe fn store(
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&mut self,
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addr: u64,
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source: *const u8,
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count: usize,
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traph: &mut impl HandlePageFault,
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) -> Result<(), StoreError> {
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self.memory_access(
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MemoryAccessReason::Store,
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addr,
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source.cast_mut(),
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count,
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perm_check::writable,
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|dst, src, count| core::ptr::copy_nonoverlapping(src, dst, count),
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traph,
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)
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.map_err(StoreError)
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}
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// Everyone behold, the holy function, the god of HBVM memory accesses!
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/// Split address to pages, check their permissions and feed pointers with offset
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/// to a specified function.
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///
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/// If page is not found, execute page fault trap handler.
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#[allow(clippy::too_many_arguments)] // Silence peasant
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fn memory_access(
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&mut self,
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reason: MemoryAccessReason,
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src: u64,
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mut dst: *mut u8,
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len: usize,
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permission_check: fn(Permission) -> bool,
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action: fn(*mut u8, *mut u8, usize),
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traph: &mut impl HandlePageFault,
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) -> Result<(), u64> {
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// Create new splitter
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let mut pspl = AddrPageLookuper::new(src, len, self.root_pt);
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loop {
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match pspl.next() {
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// Page is found
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Some(Ok(AddrPageLookupOk {
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vaddr,
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ptr,
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size,
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perm,
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})) => {
|
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if !permission_check(perm) {
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return Err(vaddr);
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}
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// Perform specified memory action and bump destination pointer
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action(ptr, dst, size);
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dst = unsafe { dst.add(size) };
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}
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// No page found
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Some(Err(AddrPageLookupError { addr, size })) => {
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// Attempt to execute page fault handler
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if traph.page_fault(reason, self, addr, size, dst) {
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// Shift the splitter address
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pspl.bump(size);
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// Bump dst pointer
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dst = unsafe { dst.add(size as _) };
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} else {
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return Err(addr); // Unhandleable, VM will yield.
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}
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}
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// No remaining pages, we are done!
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None => return Ok(()),
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}
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}
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}
|
||||
}
|
||||
|
||||
/// Good result from address split
|
||||
struct AddrPageLookupOk {
|
||||
/// Virtual address
|
||||
vaddr: u64,
|
||||
|
||||
/// Pointer to the start for perform operation
|
||||
ptr: *mut u8,
|
||||
|
||||
/// Size to the end of page / end of desired size
|
||||
size: usize,
|
||||
|
||||
/// Page permission
|
||||
perm: Permission,
|
||||
}
|
||||
|
||||
/// Errornous address split result
|
||||
struct AddrPageLookupError {
|
||||
/// Address of failure
|
||||
addr: u64,
|
||||
|
||||
/// Requested page size
|
||||
size: PageSize,
|
||||
}
|
||||
|
||||
/// Address splitter into pages
|
||||
struct AddrPageLookuper {
|
||||
/// Current address
|
||||
addr: u64,
|
||||
|
||||
/// Size left
|
||||
size: usize,
|
||||
|
||||
/// Page table
|
||||
pagetable: *const PageTable,
|
||||
}
|
||||
|
||||
impl AddrPageLookuper {
|
||||
/// Create a new page lookuper
|
||||
#[inline]
|
||||
pub const fn new(addr: u64, size: usize, pagetable: *const PageTable) -> Self {
|
||||
Self {
|
||||
addr,
|
||||
size,
|
||||
pagetable,
|
||||
}
|
||||
}
|
||||
|
||||
/// Bump address by size X
|
||||
fn bump(&mut self, page_size: PageSize) {
|
||||
self.addr += page_size as u64;
|
||||
self.size = self.size.saturating_sub(page_size as _);
|
||||
}
|
||||
}
|
||||
|
||||
impl Iterator for AddrPageLookuper {
|
||||
type Item = Result<AddrPageLookupOk, AddrPageLookupError>;
|
||||
|
||||
fn next(&mut self) -> Option<Self::Item> {
|
||||
// The end, everything is fine
|
||||
if self.size == 0 {
|
||||
return None;
|
||||
}
|
||||
|
||||
let (base, perm, size, offset) = 'a: {
|
||||
let mut current_pt = self.pagetable;
|
||||
|
||||
// Walk the page table
|
||||
for lvl in (0..5).rev() {
|
||||
// Get an entry
|
||||
unsafe {
|
||||
let entry = (*current_pt)
|
||||
.table
|
||||
.get_unchecked(addr_extract_index(self.addr, lvl));
|
||||
|
||||
let ptr = entry.ptr();
|
||||
match entry.permission() {
|
||||
// No page → page fault
|
||||
Permission::Empty => {
|
||||
return Some(Err(AddrPageLookupError {
|
||||
addr: self.addr,
|
||||
size: PageSize::from_lvl(lvl)?,
|
||||
}))
|
||||
}
|
||||
|
||||
// Node → proceed waking
|
||||
Permission::Node => current_pt = ptr as _,
|
||||
|
||||
// Leaf → return relevant data
|
||||
perm => {
|
||||
break 'a (
|
||||
// Pointer in host memory
|
||||
ptr as *mut u8,
|
||||
perm,
|
||||
PageSize::from_lvl(lvl)?,
|
||||
// In-page offset
|
||||
addr_extract_index(self.addr, lvl),
|
||||
);
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
return None; // Reached the end (should not happen)
|
||||
};
|
||||
|
||||
// Get available byte count in the selected page with offset
|
||||
let avail = (size as usize - offset).clamp(0, self.size);
|
||||
self.bump(size);
|
||||
|
||||
Some(Ok(AddrPageLookupOk {
|
||||
vaddr: self.addr,
|
||||
ptr: unsafe { base.add(offset) }, // Return pointer to the start of region
|
||||
size: avail,
|
||||
perm,
|
||||
}))
|
||||
}
|
||||
}
|
||||
|
||||
/// Extract index in page table on specified level
|
||||
///
|
||||
/// The level shall not be larger than 4, otherwise
|
||||
/// the output of the function is unspecified (yes, it can also panic :)
|
||||
pub fn addr_extract_index(addr: u64, lvl: u8) -> usize {
|
||||
debug_assert!(lvl <= 4);
|
||||
usize::try_from((addr >> (lvl * 8 + 12)) & ((1 << 8) - 1)).expect("?conradluget a better CPU")
|
||||
}
|
||||
|
||||
/// Page size
|
||||
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
|
||||
pub enum PageSize {
|
||||
/// 4 KiB page (on level 0)
|
||||
Size4K = 4096,
|
||||
|
||||
/// 2 MiB page (on level 1)
|
||||
Size2M = 1024 * 1024 * 2,
|
||||
|
||||
/// 1 GiB page (on level 2)
|
||||
Size1G = 1024 * 1024 * 1024,
|
||||
}
|
||||
|
||||
impl PageSize {
|
||||
/// Convert page table level to size of page
|
||||
const fn from_lvl(lvl: u8) -> Option<Self> {
|
||||
match lvl {
|
||||
0 => Some(PageSize::Size4K),
|
||||
1 => Some(PageSize::Size2M),
|
||||
2 => Some(PageSize::Size1G),
|
||||
_ => None,
|
||||
}
|
||||
}
|
||||
) -> Result<(), StoreError>;
|
||||
}
|
||||
|
||||
/// Unhandled load access trap
|
||||
|
@ -433,15 +34,6 @@ pub struct LoadError(pub u64);
|
|||
#[display(fmt = "Store access error at address {_0:#x}")]
|
||||
pub struct StoreError(pub u64);
|
||||
|
||||
/// There was no entry in page table to unmap
|
||||
///
|
||||
/// No worry, don't panic, nothing bad has happened,
|
||||
/// but if you are 120% sure there should be something,
|
||||
/// double-check your addresses.
|
||||
#[derive(Clone, Copy, Display, Debug)]
|
||||
#[display(fmt = "There was no entry to unmap")]
|
||||
pub struct NothingToUnmap;
|
||||
|
||||
/// Reason to access memory
|
||||
#[derive(Clone, Copy, Display, Debug, PartialEq, Eq)]
|
||||
pub enum MemoryAccessReason {
|
||||
|
@ -460,35 +52,3 @@ impl From<StoreError> for VmRunError {
|
|||
Self::StoreAccessEx(value.0)
|
||||
}
|
||||
}
|
||||
|
||||
/// Error mapping
|
||||
#[derive(Clone, Copy, Display, Debug, PartialEq, Eq)]
|
||||
pub enum MapError {
|
||||
/// Entry was already mapped
|
||||
#[display(fmt = "There is already a page mapped on specified address")]
|
||||
AlreadyMapped,
|
||||
/// When walking a page entry was
|
||||
/// encounterd.
|
||||
#[display(fmt = "There was a page mapped on the way instead of node")]
|
||||
PageOnNode,
|
||||
}
|
||||
|
||||
/// Permisison checks
|
||||
pub mod perm_check {
|
||||
use super::paging::Permission;
|
||||
|
||||
/// Page is readable
|
||||
#[inline(always)]
|
||||
pub const fn readable(perm: Permission) -> bool {
|
||||
matches!(
|
||||
perm,
|
||||
Permission::Readonly | Permission::Write | Permission::Exec
|
||||
)
|
||||
}
|
||||
|
||||
/// Page is writable
|
||||
#[inline(always)]
|
||||
pub const fn writable(perm: Permission) -> bool {
|
||||
matches!(perm, Permission::Write)
|
||||
}
|
||||
}
|
||||
|
|
|
@ -1,20 +0,0 @@
|
|||
//! Program trap handling interfaces
|
||||
|
||||
use super::{Memory, MemoryAccessReason, PageSize};
|
||||
|
||||
/// Handle VM traps
|
||||
pub trait HandlePageFault {
|
||||
/// Handle page fault
|
||||
///
|
||||
/// Return true if handling was sucessful,
|
||||
/// otherwise the program will be interrupted and will
|
||||
/// yield an error.
|
||||
fn page_fault(
|
||||
&mut self,
|
||||
reason: MemoryAccessReason,
|
||||
memory: &mut Memory,
|
||||
vaddr: u64,
|
||||
size: PageSize,
|
||||
dataptr: *mut u8,
|
||||
) -> bool;
|
||||
}
|
475
hbvm/src/mem/softpaged/mod.rs
Normal file
475
hbvm/src/mem/softpaged/mod.rs
Normal file
|
@ -0,0 +1,475 @@
|
|||
//! Platform independent, software paged memory implementation
|
||||
|
||||
pub mod paging;
|
||||
|
||||
use {
|
||||
super::{LoadError, Memory, MemoryAccessReason, StoreError},
|
||||
derive_more::Display,
|
||||
paging::{PageTable, Permission},
|
||||
};
|
||||
|
||||
#[cfg(feature = "alloc")]
|
||||
use {alloc::boxed::Box, paging::PtEntry};
|
||||
|
||||
/// HoleyBytes software paged memory
|
||||
#[derive(Clone, Debug)]
|
||||
pub struct SoftPagedMem<PfHandler> {
|
||||
/// Root page table
|
||||
pub root_pt: *mut PageTable,
|
||||
/// Page fault handler
|
||||
pub pf_handler: PfHandler,
|
||||
}
|
||||
|
||||
impl<PfHandler: HandlePageFault> Memory for SoftPagedMem<PfHandler> {
|
||||
/// Load value from an address
|
||||
///
|
||||
/// # Safety
|
||||
/// Applies same conditions as for [`core::ptr::copy_nonoverlapping`]
|
||||
unsafe fn load(&mut self, addr: u64, target: *mut u8, count: usize) -> Result<(), LoadError> {
|
||||
self.memory_access(
|
||||
MemoryAccessReason::Load,
|
||||
addr,
|
||||
target,
|
||||
count,
|
||||
perm_check::readable,
|
||||
|src, dst, count| core::ptr::copy_nonoverlapping(src, dst, count),
|
||||
)
|
||||
.map_err(LoadError)
|
||||
}
|
||||
|
||||
/// Store value to an address
|
||||
///
|
||||
/// # Safety
|
||||
/// Applies same conditions as for [`core::ptr::copy_nonoverlapping`]
|
||||
unsafe fn store(
|
||||
&mut self,
|
||||
addr: u64,
|
||||
source: *const u8,
|
||||
count: usize,
|
||||
) -> Result<(), StoreError> {
|
||||
self.memory_access(
|
||||
MemoryAccessReason::Store,
|
||||
addr,
|
||||
source.cast_mut(),
|
||||
count,
|
||||
perm_check::writable,
|
||||
|dst, src, count| core::ptr::copy_nonoverlapping(src, dst, count),
|
||||
)
|
||||
.map_err(StoreError)
|
||||
}
|
||||
}
|
||||
|
||||
impl<PfHandler: HandlePageFault> SoftPagedMem<PfHandler> {
|
||||
// Everyone behold, the holy function, the god of HBVM memory accesses!
|
||||
|
||||
/// Split address to pages, check their permissions and feed pointers with offset
|
||||
/// to a specified function.
|
||||
///
|
||||
/// If page is not found, execute page fault trap handler.
|
||||
#[allow(clippy::too_many_arguments)] // Silence peasant
|
||||
fn memory_access(
|
||||
&mut self,
|
||||
reason: MemoryAccessReason,
|
||||
src: u64,
|
||||
mut dst: *mut u8,
|
||||
len: usize,
|
||||
permission_check: fn(Permission) -> bool,
|
||||
action: fn(*mut u8, *mut u8, usize),
|
||||
) -> Result<(), u64> {
|
||||
// Create new splitter
|
||||
let mut pspl = AddrPageLookuper::new(src, len, self.root_pt);
|
||||
loop {
|
||||
match pspl.next() {
|
||||
// Page is found
|
||||
Some(Ok(AddrPageLookupOk {
|
||||
vaddr,
|
||||
ptr,
|
||||
size,
|
||||
perm,
|
||||
})) => {
|
||||
if !permission_check(perm) {
|
||||
return Err(vaddr);
|
||||
}
|
||||
|
||||
// Perform specified memory action and bump destination pointer
|
||||
action(ptr, dst, size);
|
||||
dst = unsafe { dst.add(size) };
|
||||
}
|
||||
// No page found
|
||||
Some(Err(AddrPageLookupError { addr, size })) => {
|
||||
// Attempt to execute page fault handler
|
||||
if self.pf_handler.page_fault(reason, addr, size, dst) {
|
||||
// Shift the splitter address
|
||||
pspl.bump(size);
|
||||
|
||||
// Bump dst pointer
|
||||
dst = unsafe { dst.add(size as _) };
|
||||
} else {
|
||||
return Err(addr); // Unhandleable, VM will yield.
|
||||
}
|
||||
}
|
||||
// No remaining pages, we are done!
|
||||
None => return Ok(()),
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/// Good result from address split
|
||||
struct AddrPageLookupOk {
|
||||
/// Virtual address
|
||||
vaddr: u64,
|
||||
|
||||
/// Pointer to the start for perform operation
|
||||
ptr: *mut u8,
|
||||
|
||||
/// Size to the end of page / end of desired size
|
||||
size: usize,
|
||||
|
||||
/// Page permission
|
||||
perm: Permission,
|
||||
}
|
||||
|
||||
/// Errornous address split result
|
||||
struct AddrPageLookupError {
|
||||
/// Address of failure
|
||||
addr: u64,
|
||||
|
||||
/// Requested page size
|
||||
size: PageSize,
|
||||
}
|
||||
|
||||
/// Address splitter into pages
|
||||
struct AddrPageLookuper {
|
||||
/// Current address
|
||||
addr: u64,
|
||||
|
||||
/// Size left
|
||||
size: usize,
|
||||
|
||||
/// Page table
|
||||
pagetable: *const PageTable,
|
||||
}
|
||||
|
||||
impl AddrPageLookuper {
|
||||
/// Create a new page lookuper
|
||||
#[inline]
|
||||
pub const fn new(addr: u64, size: usize, pagetable: *const PageTable) -> Self {
|
||||
Self {
|
||||
addr,
|
||||
size,
|
||||
pagetable,
|
||||
}
|
||||
}
|
||||
|
||||
/// Bump address by size X
|
||||
fn bump(&mut self, page_size: PageSize) {
|
||||
self.addr += page_size as u64;
|
||||
self.size = self.size.saturating_sub(page_size as _);
|
||||
}
|
||||
}
|
||||
|
||||
impl Iterator for AddrPageLookuper {
|
||||
type Item = Result<AddrPageLookupOk, AddrPageLookupError>;
|
||||
|
||||
fn next(&mut self) -> Option<Self::Item> {
|
||||
// The end, everything is fine
|
||||
if self.size == 0 {
|
||||
return None;
|
||||
}
|
||||
|
||||
let (base, perm, size, offset) = 'a: {
|
||||
let mut current_pt = self.pagetable;
|
||||
|
||||
// Walk the page table
|
||||
for lvl in (0..5).rev() {
|
||||
// Get an entry
|
||||
unsafe {
|
||||
let entry = (*current_pt)
|
||||
.table
|
||||
.get_unchecked(addr_extract_index(self.addr, lvl));
|
||||
|
||||
let ptr = entry.ptr();
|
||||
match entry.permission() {
|
||||
// No page → page fault
|
||||
Permission::Empty => {
|
||||
return Some(Err(AddrPageLookupError {
|
||||
addr: self.addr,
|
||||
size: PageSize::from_lvl(lvl)?,
|
||||
}))
|
||||
}
|
||||
|
||||
// Node → proceed waking
|
||||
Permission::Node => current_pt = ptr as _,
|
||||
|
||||
// Leaf → return relevant data
|
||||
perm => {
|
||||
break 'a (
|
||||
// Pointer in host memory
|
||||
ptr as *mut u8,
|
||||
perm,
|
||||
PageSize::from_lvl(lvl)?,
|
||||
// In-page offset
|
||||
addr_extract_index(self.addr, lvl),
|
||||
);
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
return None; // Reached the end (should not happen)
|
||||
};
|
||||
|
||||
// Get available byte count in the selected page with offset
|
||||
let avail = (size as usize - offset).clamp(0, self.size);
|
||||
self.bump(size);
|
||||
|
||||
Some(Ok(AddrPageLookupOk {
|
||||
vaddr: self.addr,
|
||||
ptr: unsafe { base.add(offset) }, // Return pointer to the start of region
|
||||
size: avail,
|
||||
perm,
|
||||
}))
|
||||
}
|
||||
}
|
||||
|
||||
#[cfg(feature = "alloc")]
|
||||
impl<PfHandler: Default> Default for SoftPagedMem<PfHandler> {
|
||||
fn default() -> Self {
|
||||
Self {
|
||||
root_pt: Box::into_raw(Default::default()),
|
||||
pf_handler: Default::default(),
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
#[cfg(feature = "alloc")]
|
||||
impl<A> Drop for SoftPagedMem<A> {
|
||||
fn drop(&mut self) {
|
||||
let _ = unsafe { Box::from_raw(self.root_pt) };
|
||||
}
|
||||
}
|
||||
|
||||
#[cfg(feature = "alloc")]
|
||||
impl<A> SoftPagedMem<A> {
|
||||
/// Maps host's memory into VM's memory
|
||||
///
|
||||
/// # Safety
|
||||
/// - Your faith in the gods of UB
|
||||
/// - Addr-san claims it's fine but who knows is she isn't lying :ferrisSus:
|
||||
/// - Alright, Miri-sama is also fine with this, who knows why
|
||||
pub unsafe fn map(
|
||||
&mut self,
|
||||
host: *mut u8,
|
||||
target: u64,
|
||||
perm: Permission,
|
||||
pagesize: PageSize,
|
||||
) -> Result<(), MapError> {
|
||||
let mut current_pt = self.root_pt;
|
||||
|
||||
// Decide on what level depth are we going
|
||||
let lookup_depth = match pagesize {
|
||||
PageSize::Size4K => 0,
|
||||
PageSize::Size2M => 1,
|
||||
PageSize::Size1G => 2,
|
||||
};
|
||||
|
||||
// Walk pagetable levels
|
||||
for lvl in (lookup_depth + 1..5).rev() {
|
||||
let entry = (*current_pt)
|
||||
.table
|
||||
.get_unchecked_mut(addr_extract_index(target, lvl));
|
||||
|
||||
let ptr = entry.ptr();
|
||||
match entry.permission() {
|
||||
// Still not on target and already seeing empty entry?
|
||||
// No worries! Let's create one (allocates).
|
||||
Permission::Empty => {
|
||||
// Increase children count
|
||||
(*current_pt).childen += 1;
|
||||
|
||||
let table = Box::into_raw(Box::new(paging::PtPointedData {
|
||||
pt: PageTable::default(),
|
||||
}));
|
||||
|
||||
core::ptr::write(entry, PtEntry::new(table, Permission::Node));
|
||||
current_pt = table as _;
|
||||
}
|
||||
// Continue walking
|
||||
Permission::Node => current_pt = ptr as _,
|
||||
|
||||
// There is some entry on place of node
|
||||
_ => return Err(MapError::PageOnNode),
|
||||
}
|
||||
}
|
||||
|
||||
let node = (*current_pt)
|
||||
.table
|
||||
.get_unchecked_mut(addr_extract_index(target, lookup_depth));
|
||||
|
||||
// Check if node is not mapped
|
||||
if node.permission() != Permission::Empty {
|
||||
return Err(MapError::AlreadyMapped);
|
||||
}
|
||||
|
||||
// Write entry
|
||||
(*current_pt).childen += 1;
|
||||
core::ptr::write(node, PtEntry::new(host.cast(), perm));
|
||||
|
||||
Ok(())
|
||||
}
|
||||
|
||||
/// Unmaps pages from VM's memory
|
||||
///
|
||||
/// If errors, it only means there is no entry to unmap and in most cases
|
||||
/// just should be ignored.
|
||||
pub fn unmap(&mut self, addr: u64) -> Result<(), NothingToUnmap> {
|
||||
let mut current_pt = self.root_pt;
|
||||
let mut page_tables = [core::ptr::null_mut(); 5];
|
||||
|
||||
// Walk page table in reverse
|
||||
for lvl in (0..5).rev() {
|
||||
let entry = unsafe {
|
||||
(*current_pt)
|
||||
.table
|
||||
.get_unchecked_mut(addr_extract_index(addr, lvl))
|
||||
};
|
||||
|
||||
let ptr = entry.ptr();
|
||||
match entry.permission() {
|
||||
// Nothing is there, throw an error, not critical!
|
||||
Permission::Empty => return Err(NothingToUnmap),
|
||||
// Node – Save to visited pagetables and continue walking
|
||||
Permission::Node => {
|
||||
page_tables[lvl as usize] = entry;
|
||||
current_pt = ptr as _
|
||||
}
|
||||
// Page entry – zero it out!
|
||||
// Zero page entry is completely valid entry with
|
||||
// empty permission - no UB here!
|
||||
_ => unsafe {
|
||||
core::ptr::write_bytes(entry, 0, 1);
|
||||
break;
|
||||
},
|
||||
}
|
||||
}
|
||||
|
||||
// Now walk in order visited page tables
|
||||
for entry in page_tables.into_iter() {
|
||||
// Level not visited, skip.
|
||||
if entry.is_null() {
|
||||
continue;
|
||||
}
|
||||
|
||||
unsafe {
|
||||
let children = &mut (*(*entry).ptr()).pt.childen;
|
||||
*children -= 1; // Decrease children count
|
||||
|
||||
// If there are no children, deallocate.
|
||||
if *children == 0 {
|
||||
let _ = Box::from_raw((*entry).ptr() as *mut PageTable);
|
||||
|
||||
// Zero visited entry
|
||||
core::ptr::write_bytes(entry, 0, 1);
|
||||
} else {
|
||||
break;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
Ok(())
|
||||
}
|
||||
}
|
||||
|
||||
/// Extract index in page table on specified level
|
||||
///
|
||||
/// The level shall not be larger than 4, otherwise
|
||||
/// the output of the function is unspecified (yes, it can also panic :)
|
||||
pub fn addr_extract_index(addr: u64, lvl: u8) -> usize {
|
||||
debug_assert!(lvl <= 4);
|
||||
usize::try_from((addr >> (lvl * 8 + 12)) & ((1 << 8) - 1)).expect("?conradluget a better CPU")
|
||||
}
|
||||
|
||||
/// Page size
|
||||
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
|
||||
pub enum PageSize {
|
||||
/// 4 KiB page (on level 0)
|
||||
Size4K = 4096,
|
||||
|
||||
/// 2 MiB page (on level 1)
|
||||
Size2M = 1024 * 1024 * 2,
|
||||
|
||||
/// 1 GiB page (on level 2)
|
||||
Size1G = 1024 * 1024 * 1024,
|
||||
}
|
||||
|
||||
impl PageSize {
|
||||
/// Convert page table level to size of page
|
||||
const fn from_lvl(lvl: u8) -> Option<Self> {
|
||||
match lvl {
|
||||
0 => Some(PageSize::Size4K),
|
||||
1 => Some(PageSize::Size2M),
|
||||
2 => Some(PageSize::Size1G),
|
||||
_ => None,
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/// Error mapping
|
||||
#[derive(Clone, Copy, Display, Debug, PartialEq, Eq)]
|
||||
pub enum MapError {
|
||||
/// Entry was already mapped
|
||||
#[display(fmt = "There is already a page mapped on specified address")]
|
||||
AlreadyMapped,
|
||||
/// When walking a page entry was
|
||||
/// encounterd.
|
||||
#[display(fmt = "There was a page mapped on the way instead of node")]
|
||||
PageOnNode,
|
||||
}
|
||||
|
||||
/// There was no entry in page table to unmap
|
||||
///
|
||||
/// No worry, don't panic, nothing bad has happened,
|
||||
/// but if you are 120% sure there should be something,
|
||||
/// double-check your addresses.
|
||||
#[derive(Clone, Copy, Display, Debug)]
|
||||
#[display(fmt = "There was no entry to unmap")]
|
||||
pub struct NothingToUnmap;
|
||||
|
||||
/// Permisison checks
|
||||
pub mod perm_check {
|
||||
use super::paging::Permission;
|
||||
|
||||
/// Page is readable
|
||||
#[inline(always)]
|
||||
pub const fn readable(perm: Permission) -> bool {
|
||||
matches!(
|
||||
perm,
|
||||
Permission::Readonly | Permission::Write | Permission::Exec
|
||||
)
|
||||
}
|
||||
|
||||
/// Page is writable
|
||||
#[inline(always)]
|
||||
pub const fn writable(perm: Permission) -> bool {
|
||||
matches!(perm, Permission::Write)
|
||||
}
|
||||
}
|
||||
|
||||
/// Handle VM traps
|
||||
pub trait HandlePageFault {
|
||||
/// Handle page fault
|
||||
///
|
||||
/// Return true if handling was sucessful,
|
||||
/// otherwise the program will be interrupted and will
|
||||
/// yield an error.
|
||||
fn page_fault(
|
||||
&mut self,
|
||||
reason: MemoryAccessReason,
|
||||
// memory: &mut SoftPagedMem<Self>, TODO: Make work
|
||||
vaddr: u64,
|
||||
size: PageSize,
|
||||
dataptr: *mut u8,
|
||||
) -> bool
|
||||
where
|
||||
Self: Sized;
|
||||
}
|
Loading…
Reference in a new issue