From d3134fec7ecaea369be3eba371a8bb9f9f4a4c7f Mon Sep 17 00:00:00 2001
From: Yuekai Jia <equation618@gmail.com>
Date: Mon, 5 Aug 2024 15:45:38 +0800
Subject: [PATCH] Fix entry present check in page table unmap & protect

Otherwise there may be bugs when manipulate empty mappings on
lazy mapping.
---
 page_table_multiarch/src/bits64.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/page_table_multiarch/src/bits64.rs b/page_table_multiarch/src/bits64.rs
index bbcdb3d..118a4da 100644
--- a/page_table_multiarch/src/bits64.rs
+++ b/page_table_multiarch/src/bits64.rs
@@ -104,7 +104,7 @@ impl<M: PagingMetaData, PTE: GenericPTE, H: PagingHandler> PageTable64<M, PTE, H
         flags: MappingFlags,
     ) -> PagingResult<(PageSize, TlbFlush<M>)> {
         let (entry, size) = self.get_entry_mut(vaddr)?;
-        if entry.is_unused() {
+        if !entry.is_present() {
             return Err(PagingError::NotMapped);
         }
         entry.set_flags(flags, size.is_huge());
@@ -117,7 +117,8 @@ impl<M: PagingMetaData, PTE: GenericPTE, H: PagingHandler> PageTable64<M, PTE, H
     /// mapping is not present.
     pub fn unmap(&mut self, vaddr: M::VirtAddr) -> PagingResult<(PhysAddr, PageSize, TlbFlush<M>)> {
         let (entry, size) = self.get_entry_mut(vaddr)?;
-        if entry.is_unused() {
+        if !entry.is_present() {
+            entry.clear();
             return Err(PagingError::NotMapped);
         }
         let paddr = entry.paddr();