Merge pull request #422 from rust-osdev/v0.9-fixes

[v0.9] Fix map errors during kernel loading

Author: phil-opp

Changelog.md

@@ -1,5 +1,10 @@
 # Unreleased
 
+
+- [Fix map errors during kernel loading](https://github.com/rust-osdev/bootloader/pull/422)
+    - Don't error if a kernel page is already mapped to the correct frame
+    - Fix: unmap temp page again to enable multiple bss-like sections
+
 # 0.9.25 – 2024-02-16
 
 - [Fix data layout for custom targets for LLVM 18](https://github.com/rust-osdev/bootloader/pull/421)

src/page_table.rs

@@ -96,8 +96,15 @@ pub(crate) fn map_segment(
             for frame in PhysFrame::range_inclusive(start_frame, end_frame) {
                 let offset = frame - start_frame;
                 let page = start_page + offset;
-                unsafe { map_page(page, frame, page_table_flags, page_table, frame_allocator)? }
-                    .flush();
+                match unsafe {
+                    map_page(page, frame, page_table_flags, page_table, frame_allocator)
+                } {
+                    Ok(flusher) => flusher.flush(),
+                    Err(MapToError::PageAlreadyMapped(to)) if to == frame => {
+                        // nothing to do, page is already mapped to the correct frame
+                    }
+                    Err(err) => return Err(err),
+                }
             }
 
             if mem_size > file_size {
@@ -117,7 +124,7 @@ pub(crate) fn map_segment(
                     unsafe {
                         map_page(
                             temp_page.clone(),
-                            new_frame.clone(),
+                            new_frame,
                             page_table_flags,
                             page_table,
                             frame_allocator,
@@ -145,6 +152,11 @@ pub(crate) fn map_segment(
                         });
                     }
 
+                    // unmap temp page again
+                    let (new_frame, flusher) = page_table.unmap(temp_page).unwrap();
+                    flusher.flush();
+
+                    // map last page to new frame
                     unsafe {
                         map_page(
                             last_page,