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Co-authored-by: Tom Dohrmann <[email protected]>

Author: phil-opp

bios/stage-2/src/protected_mode.rs

@@ -92,7 +92,9 @@ pub unsafe fn copy_to_protected_mode(target: *mut u8, bytes: &[u8]) {
         let dst = target.wrapping_add(offset);
         // we need to do the write in inline assembly because the compiler
         // seems to truncate the address
-        unsafe { asm!("mov [{}], {}", in(reg) dst, in(reg_byte) *byte) };
+        unsafe {
+            asm!("mov [{}], {}", in(reg) dst, in(reg_byte) *byte, options(nostack, preserves_flags))
+        };
         assert_eq!(read_from_protected_mode(dst), *byte);
     }
 }
@@ -102,7 +104,9 @@ pub unsafe fn read_from_protected_mode(ptr: *mut u8) -> u8 {
     let res;
     // we need to do the read in inline assembly because the compiler
     // seems to truncate the address
-    unsafe { asm!("mov {}, [{}]", out(reg_byte) res, in(reg) ptr) };
+    unsafe {
+        asm!("mov {}, [{}]", out(reg_byte) res, in(reg) ptr, options(pure, readonly, nostack, preserves_flags))
+    };
     res
 }
 

bios/stage-3/src/paging.rs

@@ -21,6 +21,7 @@ fn create_mappings() {
         l3.entries[i] = (l2 as *mut PageTable as u64) | common_flags;
         let offset = u64::try_from(i).unwrap() * 1024 * 1024 * 1024;
         for (j, entry) in l2.entries.iter_mut().enumerate() {
+            // map huge pages
             *entry =
                 (offset + u64::try_from(j).unwrap() * (2 * 1024 * 1024)) | common_flags | (1 << 7);
         }