Add Linux and Windows implementations for dirty page tracking

- Implemented `LinuxDirtyPageTracker` for tracking dirty pages in Linux.
  - Utilizes SIGSEGV to detect writes and marks pages as dirty.
  - Supports concurrent access and ensures memory protection.
  - Includes comprehensive tests for various scenarios including overlap detection and concurrent writes.

- Added `WindowsDirtyPageTracker` as a placeholder for Windows dirty page tracking.
  - Currently marks all pages as dirty until further implementation is completed.
  - Includes basic structure and initialization logic.

Signed-off-by: Simon Davies <[email protected]>

Author: simongdavies

src/hyperlight_host/src/mem/dirty_page_tracking.rs

@@ -0,0 +1,49 @@
+/*
+Copyright 2025  The Hyperlight Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+use tracing::{Span, instrument};
+
+#[cfg(target_os = "linux")]
+pub use super::linux_dirty_page_tracker::LinuxDirtyPageTracker as PlatformDirtyPageTracker;
+use super::shared_mem::SharedMemory;
+#[cfg(target_os = "windows")]
+pub use super::windows_dirty_page_tracker::WindowsDirtyPageTracker as PlatformDirtyPageTracker;
+use crate::Result;
+
+/// Trait defining the interface for dirty page tracking implementations
+pub trait DirtyPageTracking {
+    fn get_dirty_pages(self) -> Vec<usize>;
+}
+
+/// Cross-platform dirty page tracker that delegates to platform-specific implementations
+pub struct DirtyPageTracker {
+    inner: PlatformDirtyPageTracker,
+}
+
+impl DirtyPageTracker {
+    /// Create a new dirty page tracker for the given shared memory
+    #[instrument(skip_all, parent = Span::current(), level = "Trace")]
+    pub fn new<T: SharedMemory>(shared_memory: &T) -> Result<Self> {
+        let inner = PlatformDirtyPageTracker::new(shared_memory)?;
+        Ok(Self { inner })
+    }
+}
+
+impl DirtyPageTracking for DirtyPageTracker {
+    fn get_dirty_pages(self) -> Vec<usize> {
+        self.inner.get_dirty_pages()
+    }
+}