Initial commit: xenia-rs workspace for Xbox 360 RE

Rust reimplementation of the xenia Xbox 360 emulator targeting reverse-
engineering and preservation, initially scoped to Project Sylpheed.

Includes:
- XEX2 loader (LZX decompression, AES decryption, PE parsing)
- XISO / XGD2 disc image VFS
- PPC interpreter with 200+ opcodes and VMX128 decoding
- Static analyzer: functions, cross-references, labels, asm + SQLite output
- HLE kernel covering the xboxkrnl/xam subset used by Sylpheed init
- Debugger with in-memory and SQLite-backed execution tracing
- `xenia-rs` CLI with extract/dis/exec commands that produce cumulative,
  superset SQLite databases and opt-in instruction/import/branch traces

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

crates/xenia-memory/src/platform.rs

@@ -0,0 +1,98 @@
+use crate::MemoryError;
+
+/// Reserve a contiguous virtual address region without committing physical pages.
+#[cfg(unix)]
+pub fn reserve_address_space(size: usize) -> Result<*mut u8, MemoryError> {
+    unsafe {
+        let ptr = libc::mmap(
+            std::ptr::null_mut(),
+            size,
+            libc::PROT_NONE,
+            libc::MAP_PRIVATE | libc::MAP_ANONYMOUS | libc::MAP_NORESERVE,
+            -1,
+            0,
+        );
+        if ptr == libc::MAP_FAILED {
+            Err(MemoryError::AllocationFailed(format!(
+                "mmap failed for {} bytes: {}",
+                size,
+                std::io::Error::last_os_error()
+            )))
+        } else {
+            Ok(ptr as *mut u8)
+        }
+    }
+}
+
+/// Commit (make accessible) a region within a previously reserved address space.
+#[cfg(unix)]
+pub fn commit_memory(ptr: *mut u8, size: usize) -> Result<(), MemoryError> {
+    unsafe {
+        let result = libc::mprotect(ptr as *mut libc::c_void, size, libc::PROT_READ | libc::PROT_WRITE);
+        if result != 0 {
+            Err(MemoryError::AllocationFailed(format!(
+                "mprotect failed for {} bytes: {}",
+                size,
+                std::io::Error::last_os_error()
+            )))
+        } else {
+            Ok(())
+        }
+    }
+}
+
+/// Release a previously reserved address space.
+#[cfg(unix)]
+pub unsafe fn release_address_space(ptr: *mut u8, size: usize) {
+    unsafe { libc::munmap(ptr as *mut libc::c_void, size); }
+}
+
+#[cfg(windows)]
+pub fn reserve_address_space(size: usize) -> Result<*mut u8, MemoryError> {
+    unsafe {
+        let ptr = windows_sys::Win32::System::Memory::VirtualAlloc(
+            std::ptr::null_mut(),
+            size,
+            windows_sys::Win32::System::Memory::MEM_RESERVE,
+            windows_sys::Win32::System::Memory::PAGE_NOACCESS,
+        );
+        if ptr.is_null() {
+            Err(MemoryError::AllocationFailed(format!(
+                "VirtualAlloc reserve failed for {} bytes",
+                size,
+            )))
+        } else {
+            Ok(ptr as *mut u8)
+        }
+    }
+}
+
+#[cfg(windows)]
+pub fn commit_memory(ptr: *mut u8, size: usize) -> Result<(), MemoryError> {
+    unsafe {
+        let result = windows_sys::Win32::System::Memory::VirtualAlloc(
+            ptr as *mut _,
+            size,
+            windows_sys::Win32::System::Memory::MEM_COMMIT,
+            windows_sys::Win32::System::Memory::PAGE_READWRITE,
+        );
+        if result.is_null() {
+            Err(MemoryError::AllocationFailed(format!(
+                "VirtualAlloc commit failed for {} bytes",
+                size,
+            )))
+        } else {
+            Ok(())
+        }
+    }
+}
+
+#[cfg(windows)]
+pub unsafe fn release_address_space(ptr: *mut u8, size: usize) {
+    let _ = size;
+    windows_sys::Win32::System::Memory::VirtualFree(
+        ptr as *mut _,
+        0,
+        windows_sys::Win32::System::Memory::MEM_RELEASE,
+    );
+}