From 604a79b636f54470dcabbd55ae9cf74c141ecf0f Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Fri, 6 Mar 2020 14:41:53 +0100
Subject: [PATCH] Make update_flags unsafe too

---
 src/structures/paging/mapper/mapped_page_table.rs    |  6 +++---
 src/structures/paging/mapper/mod.rs                  | 10 +++++++++-
 src/structures/paging/mapper/offset_page_table.rs    |  6 +++---
 src/structures/paging/mapper/recursive_page_table.rs | 12 +++++++++---
 4 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/src/structures/paging/mapper/mapped_page_table.rs b/src/structures/paging/mapper/mapped_page_table.rs
index 4e706fa83..9a0486ec7 100644
--- a/src/structures/paging/mapper/mapped_page_table.rs
+++ b/src/structures/paging/mapper/mapped_page_table.rs
@@ -161,7 +161,7 @@ impl<'a, P: PhysToVirt> Mapper<Size1GiB> for MappedPageTable<'a, P> {
         Ok((frame, MapperFlush::new(page)))
     }
 
-    fn update_flags(
+    unsafe fn update_flags(
         &mut self,
         page: Page<Size1GiB>,
         flags: PageTableFlags,
@@ -237,7 +237,7 @@ impl<'a, P: PhysToVirt> Mapper<Size2MiB> for MappedPageTable<'a, P> {
         Ok((frame, MapperFlush::new(page)))
     }
 
-    fn update_flags(
+    unsafe fn update_flags(
         &mut self,
         page: Page<Size2MiB>,
         flags: PageTableFlags,
@@ -315,7 +315,7 @@ impl<'a, P: PhysToVirt> Mapper<Size4KiB> for MappedPageTable<'a, P> {
         Ok((frame, MapperFlush::new(page)))
     }
 
-    fn update_flags(
+    unsafe fn update_flags(
         &mut self,
         page: Page<Size4KiB>,
         flags: PageTableFlags,
diff --git a/src/structures/paging/mapper/mod.rs b/src/structures/paging/mapper/mod.rs
index 01c15cb36..85b6ac856 100644
--- a/src/structures/paging/mapper/mod.rs
+++ b/src/structures/paging/mapper/mod.rs
@@ -128,7 +128,15 @@ pub trait Mapper<S: PageSize> {
     fn unmap(&mut self, page: Page<S>) -> Result<(PhysFrame<S>, MapperFlush<S>), UnmapError>;
 
     /// Updates the flags of an existing mapping.
-    fn update_flags(
+    ///
+    /// ## Safety
+    ///
+    /// This method is unsafe because changing the flags of a mapping
+    /// might result in undefined behavior. For example, setting the
+    /// `GLOBAL` and `MUTABLE` flags for a page might result in the corruption
+    /// of values stored in that page from processes running in other address
+    /// spaces.
+    unsafe fn update_flags(
         &mut self,
         page: Page<S>,
         flags: PageTableFlags,
diff --git a/src/structures/paging/mapper/offset_page_table.rs b/src/structures/paging/mapper/offset_page_table.rs
index a646c93c1..23e4da4d2 100644
--- a/src/structures/paging/mapper/offset_page_table.rs
+++ b/src/structures/paging/mapper/offset_page_table.rs
@@ -75,7 +75,7 @@ impl<'a> Mapper<Size1GiB> for OffsetPageTable<'a> {
     }
 
     #[inline]
-    fn update_flags(
+    unsafe fn update_flags(
         &mut self,
         page: Page<Size1GiB>,
         flags: PageTableFlags,
@@ -113,7 +113,7 @@ impl<'a> Mapper<Size2MiB> for OffsetPageTable<'a> {
     }
 
     #[inline]
-    fn update_flags(
+    unsafe fn update_flags(
         &mut self,
         page: Page<Size2MiB>,
         flags: PageTableFlags,
@@ -151,7 +151,7 @@ impl<'a> Mapper<Size4KiB> for OffsetPageTable<'a> {
     }
 
     #[inline]
-    fn update_flags(
+    unsafe fn update_flags(
         &mut self,
         page: Page<Size4KiB>,
         flags: PageTableFlags,
diff --git a/src/structures/paging/mapper/recursive_page_table.rs b/src/structures/paging/mapper/recursive_page_table.rs
index 7c1c7f37f..53901031c 100644
--- a/src/structures/paging/mapper/recursive_page_table.rs
+++ b/src/structures/paging/mapper/recursive_page_table.rs
@@ -267,7 +267,9 @@ impl<'a> Mapper<Size1GiB> for RecursivePageTable<'a> {
         Ok((frame, MapperFlush::new(page)))
     }
 
-    fn update_flags(
+    // allow unused_unsafe until https://github.com/rust-lang/rust/pull/69245 lands
+    #[allow(unused_unsafe)]
+    unsafe fn update_flags(
         &mut self,
         page: Page<Size1GiB>,
         flags: PageTableFlags,
@@ -359,7 +361,9 @@ impl<'a> Mapper<Size2MiB> for RecursivePageTable<'a> {
         Ok((frame, MapperFlush::new(page)))
     }
 
-    fn update_flags(
+    // allow unused_unsafe until https://github.com/rust-lang/rust/pull/69245 lands
+    #[allow(unused_unsafe)]
+    unsafe fn update_flags(
         &mut self,
         page: Page<Size2MiB>,
         flags: PageTableFlags,
@@ -465,7 +469,9 @@ impl<'a> Mapper<Size4KiB> for RecursivePageTable<'a> {
         Ok((frame, MapperFlush::new(page)))
     }
 
-    fn update_flags(
+    // allow unused_unsafe until https://github.com/rust-lang/rust/pull/69245 lands
+    #[allow(unused_unsafe)]
+    unsafe fn update_flags(
         &mut self,
         page: Page<Size4KiB>,
         flags: PageTableFlags,