volatile_memory: avoid undefined symbols on Windows

Windows does not have PROT_READ or PROT_WRITE, remove them.

Signed-off-by: Paolo Bonzini <[email protected]>

Author: bonzini

src/volatile_memory.rs

@@ -315,15 +315,33 @@ pub struct PtrGuard {
     _slice: MmapXenSlice,
 }
 
+#[cfg(all(feature = "xen", unix))]
+impl PtrGuard {
+    const PROT_READ: i32 = libc::PROT_READ;
+    const PROT_WRITE: i32 = libc::PROT_WRITE;
+
+    fn map(mmap: Option<&MmapInfo>, addr: *mut u8, prot: i32, len: usize) -> (*mut u8, MmapXenSlice) {
+        let slice = MmapInfo::mmap(mmap, addr, prot, len);
+        (slice.addr(), slice)
+    }
+}
+
+#[cfg(not(all(feature = "xen", unix)))]
+impl PtrGuard {
+    pub(self) const PROT_READ: i32 = 0
+    pub(self) const PROT_WRITE: i32 = 0;
+
+    fn map(_mmap: Option<&MmapInfo>, addr: *mut u8, _prot: i32, _len: usize) -> (*mut u8, ()) {
+        (addr, ())
+    }
+}
+
 #[allow(clippy::len_without_is_empty)]
 impl PtrGuard {
+
     #[allow(unused_variables)]
     fn new(mmap: Option<&MmapInfo>, addr: *mut u8, prot: i32, len: usize) -> Self {
-        #[cfg(all(feature = "xen", unix))]
-        let (addr, _slice) = {
-            let slice = MmapInfo::mmap(mmap, addr, prot, len);
-            (slice.addr(), slice)
-        };
+        let (addr, _slice) = Self::map(mmap, addr, prot, len);
 
         Self {
             addr,
@@ -335,7 +353,7 @@ impl PtrGuard {
     }
 
     fn read(mmap: Option<&MmapInfo>, addr: *mut u8, len: usize) -> Self {
-        Self::new(mmap, addr, libc::PROT_READ, len)
+        Self::new(mmap, addr, PtrGuard::PROT_READ, len)
     }
 
     /// Returns a non-mutable pointer to the beginning of the slice.
@@ -356,7 +374,7 @@ pub struct PtrGuardMut(PtrGuard);
 #[allow(clippy::len_without_is_empty)]
 impl PtrGuardMut {
     fn write(mmap: Option<&MmapInfo>, addr: *mut u8, len: usize) -> Self {
-        Self(PtrGuard::new(mmap, addr, libc::PROT_WRITE, len))
+        Self(PtrGuard::new(mmap, addr, PtrGuard::PROT_WRITE, len))
     }
 
     /// Returns a mutable pointer to the beginning of the slice. Mutable accesses performed