diff --git a/hbvm/src/softpaging/lookup.rs b/hbvm/src/softpaging/lookup.rs new file mode 100644 index 0000000..9111390 --- /dev/null +++ b/hbvm/src/softpaging/lookup.rs @@ -0,0 +1,124 @@ +//! Address lookup + +use super::{ + addr_extract_index, + paging::{PageTable, Permission}, + PageSize, +}; + +/// Good result from address split +pub struct AddrPageLookupOk { + /// Virtual address + pub vaddr: u64, + + /// Pointer to the start for perform operation + pub ptr: *mut u8, + + /// Size to the end of page / end of desired size + pub size: usize, + + /// Page permission + pub perm: Permission, +} + +/// Errornous address split result +pub struct AddrPageLookupError { + /// Address of failure + pub addr: u64, + + /// Requested page size + pub size: PageSize, +} + +/// Address splitter into pages +pub 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 + pub 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; + + fn next(&mut self) -> Option { + // 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, + })) + } +} diff --git a/hbvm/src/softpaging/mapping.rs b/hbvm/src/softpaging/mapping.rs new file mode 100644 index 0000000..9c556de --- /dev/null +++ b/hbvm/src/softpaging/mapping.rs @@ -0,0 +1,163 @@ +//! Automatic memory mapping + +use { + super::{ + addr_extract_index, + paging::{PageTable, Permission, PtEntry, PtPointedData}, + PageSize, SoftPagedMem, + }, + alloc::boxed::Box, + derive_more::Display, +}; + +#[cfg(feature = "alloc")] +impl<'p, A> SoftPagedMem<'p, 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(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(()) + } +} + +/// 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; diff --git a/hbvm/src/softpaging/mod.rs b/hbvm/src/softpaging/mod.rs index 07e05a5..67c030c 100644 --- a/hbvm/src/softpaging/mod.rs +++ b/hbvm/src/softpaging/mod.rs @@ -1,17 +1,19 @@ //! Platform independent, software paged memory implementation +use self::lookup::{AddrPageLookupError, AddrPageLookupOk, AddrPageLookuper}; + +pub mod lookup; pub mod paging; +#[cfg(feature = "alloc")] +pub mod mapping; + use { super::{LoadError, Memory, MemoryAccessReason, StoreError}, core::slice::SliceIndex, - 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<'p, PfH> { @@ -173,261 +175,6 @@ impl<'p, PfH: HandlePageFault> SoftPagedMem<'p, PfH> { } } -/// 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; - - fn next(&mut self) -> Option { - // 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<'p, A> Drop for SoftPagedMem<'p, A> { - fn drop(&mut self) { - let _ = unsafe { Box::from_raw(self.root_pt) }; - } -} - -#[cfg(feature = "alloc")] -impl<'p, A> SoftPagedMem<'p, 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 @@ -462,27 +209,6 @@ impl PageSize { } } -/// 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;