Some stuff

Cargo.toml

@@ -1,2 +1,3 @@
 [workspace]
-members = ["hbasm", "hbbytecode", "hbvm"]
+resolver = "2"
+members  = ["hbasm", "hbbytecode", "hbvm"]

hbvm/src/main.rs

@@ -21,6 +21,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                     pf_handler: TestTrapHandler,
                     program:    &prog,
                     root_pt:    Box::into_raw(Default::default()),
+                    icache:     Default::default(),
                 },
                 4,
             );

hbvm/src/mem/softpaging/icache.rs

@@ -0,0 +1,107 @@
+//! Program instruction cache
+
+use {
+    super::{lookup::AddrPageLookuper, paging::PageTable, HandlePageFault, PageSize},
+    core::{
+        mem::{size_of, MaybeUninit},
+        ptr::{copy_nonoverlapping, NonNull},
+    },
+};
+
+/// Instruction cache
+#[derive(Clone, Debug)]
+pub struct ICache {
+    /// Current page address base
+    base: u64,
+    /// Curent page pointer
+    data: Option<NonNull<u8>>,
+    /// Current page size
+    size: PageSize,
+    /// Address mask
+    mask: u64,
+}
+
+impl Default for ICache {
+    fn default() -> Self {
+        Self {
+            base: Default::default(),
+            data: Default::default(),
+            size: PageSize::Size4K,
+            mask: Default::default(),
+        }
+    }
+}
+
+impl ICache {
+    /// Fetch instruction from cache
+    ///
+    /// # Safety
+    /// `T` should be valid to read from instruction memory
+    pub(super) unsafe fn fetch<T>(
+        &mut self,
+        addr: u64,
+        root_pt: *const PageTable,
+    ) -> Option<T> {
+        let mut ret = MaybeUninit::<T>::uninit();
+
+        let pbase = self
+            .data
+            .or_else(|| self.fetch_page(self.base.checked_add(self.size as _)?, root_pt))?;
+
+        // Get address base
+        let base = addr & self.mask;
+
+        // Base not matching, fetch anew
+        if base != self.base {
+            self.fetch_page(base, root_pt)?;
+        };
+
+        let offset = addr & !self.mask;
+        let requ_size = size_of::<T>();
+
+        // Page overflow
+        let rem = (offset as usize)
+            .saturating_add(requ_size)
+            .saturating_sub(self.size as _);
+        let first_copy = requ_size.saturating_sub(rem);
+
+        // Copy non-overflowing part
+        copy_nonoverlapping(pbase.as_ptr(), ret.as_mut_ptr().cast::<u8>(), first_copy);
+
+        // Copy overflow
+        if rem != 0 {
+            let pbase = self.fetch_page(self.base.checked_add(self.size as _)?, root_pt)?;
+
+            // Unlikely, unsupported scenario
+            if rem > self.size as _ {
+                return None;
+            }
+
+            copy_nonoverlapping(
+                pbase.as_ptr(),
+                ret.as_mut_ptr().cast::<u8>().add(first_copy),
+                rem,
+            );
+        }
+
+        Some(ret.assume_init())
+    }
+
+    /// Fetch a page
+    unsafe fn fetch_page(&mut self, addr: u64, pt: *const PageTable) -> Option<NonNull<u8>> {
+        let res = AddrPageLookuper::new(addr, 0, pt).next()?.ok()?;
+        if !super::perm_check::executable(res.perm) {
+            return None;
+        }
+
+        (self.size, self.mask) = match res.size {
+            4096 => (PageSize::Size4K, !((1 << 8) - 1)),
+            2097152 => (PageSize::Size2M, !((1 << (8 * 2)) - 1)),
+            1073741824 => (PageSize::Size1G, !((1 << (8 * 3)) - 1)),
+            _ => return None,
+        };
+        self.data = Some(NonNull::new(res.ptr)?);
+        self.base = addr & self.mask;
+        self.data
+    }
+}

hbvm/src/mem/softpaging/lookup.rs

@@ -111,7 +111,7 @@ impl Iterator for AddrPageLookuper {
         };
 
         // Get available byte count in the selected page with offset
-        let avail = (size as usize - offset).clamp(0, self.size);
+        let avail = (size as usize).saturating_sub(offset).clamp(0, self.size);
         self.bump(size);
 
         Some(Ok(AddrPageLookupOk {

hbvm/src/mem/softpaging/mod.rs

@@ -2,6 +2,9 @@
 
 use core::mem::size_of;
 
+use self::icache::ICache;
+
+pub mod icache;
 pub mod lookup;
 pub mod paging;
 
@@ -23,6 +26,8 @@ pub struct SoftPagedMem<'p, PfH> {
     pub pf_handler: PfH,
     /// Program memory segment
     pub program:    &'p [u8],
+    /// Program instruction cache
+    pub icache:     ICache,
 }
 
 impl<'p, PfH: HandlePageFault> Memory for SoftPagedMem<'p, PfH> {
@@ -65,6 +70,10 @@ impl<'p, PfH: HandlePageFault> Memory for SoftPagedMem<'p, PfH> {
 
     #[inline(always)]
     unsafe fn prog_read<T>(&mut self, addr: u64) -> Option<T> {
+        if addr as usize > self.program.len() {
+            return self.icache.fetch::<T>(addr, self.root_pt);
+        }
+
         let addr = addr as usize;
         self.program
             .get(addr..addr + size_of::<T>())
@@ -73,6 +82,13 @@ impl<'p, PfH: HandlePageFault> Memory for SoftPagedMem<'p, PfH> {
 
     #[inline(always)]
     unsafe fn prog_read_unchecked<T>(&mut self, addr: u64) -> T {
+        if addr as usize > self.program.len() {
+            return self
+                .icache
+                .fetch::<T>(addr as _, self.root_pt)
+                .unwrap_or_else(|| core::mem::zeroed());
+        }
+
         self.program.as_ptr().add(addr as _).cast::<T>().read()
     }
 }