fixup! mm: improve soundness of PageRef methods

kernel/src/cpu/mem.rs

@@ -0,0 +1,39 @@
+use core::arch::asm;
+
+/// Copy `size` bytes from `src` to `dst`.
+///
+/// # Safety
+///
+/// This function has all the safety requirements of `core::ptr::copy` except
+/// that data races (both on `src` and `dst`) are explicitly permitted.
+#[inline(always)]
+pub unsafe fn copy_bytes(src: usize, dst: usize, size: usize) {
+    unsafe {
+        asm!(
+            "rep movsb",
+            inout("rsi") src => _,
+            inout("rdi") dst => _,
+            inout("rcx") size => _,
+            options(nostack),
+        );
+    }
+}
+
+/// Set `size` bytes at `dst` to `val`.
+///
+/// # Safety
+///
+/// This function has all the safety requirements of `core::ptr::write_bytes` except
+/// that data races are explicitly permitted.
+#[inline(always)]
+pub unsafe fn write_bytes(dst: usize, size: usize, value: u8) {
+    unsafe {
+        asm!(
+            "rep stosb",
+            inout("rdi") dst => _,
+            inout("rcx") size => _,
+            in("al") value,
+            options(nostack),
+        );
+    }
+}

kernel/src/cpu/mod.rs

@@ -13,6 +13,7 @@ pub mod features;
 pub mod gdt;
 pub mod idt;
 pub mod irq_state;
+pub mod mem;
 pub mod msr;
 pub mod percpu;
 pub mod registers;

kernel/src/mm/alloc.rs

@@ -5,13 +5,13 @@
 // Author: Joerg Roedel <[email protected]>
 
 use crate::address::{Address, PhysAddr, VirtAddr};
+use crate::cpu::mem::{copy_bytes, write_bytes};
 use crate::error::SvsmError;
 use crate::locking::SpinLock;
 use crate::mm::virt_to_phys;
 use crate::types::{PAGE_SHIFT, PAGE_SIZE};
 use crate::utils::{align_down, align_up, zero_mem_region};
 use core::alloc::{GlobalAlloc, Layout};
-use core::arch::asm;
 use core::mem::size_of;
 use core::ptr;
 
@@ -939,7 +939,7 @@ impl PageRef {
         let size = PAGE_SIZE;
         unsafe {
             // SAFETY: `src` and `dst` are both valid.
-            rep_movs(src, dst, size);
+            copy_bytes(src, dst, size);
         }
 
         Ok(PageRef {
@@ -956,7 +956,7 @@ impl PageRef {
         let size = buf.len();
         unsafe {
             // SAFETY: `src` and `dst` are both valid.
-            rep_movs(src, dst, size);
+            copy_bytes(src, dst, size);
         }
     }
 
@@ -968,7 +968,7 @@ impl PageRef {
         let size = buf.len();
         unsafe {
             // SAFETY: `src` and `dst` are both valid.
-            rep_movs(src, dst, size);
+            copy_bytes(src, dst, size);
         }
     }
 
@@ -978,47 +978,11 @@ impl PageRef {
 
         unsafe {
             // SAFETY: `dst` is valid.
-            rep_stosb(dst, size, value);
+            write_bytes(dst, size, value);
         }
     }
 }
 
-/// Copy `size` bytes from `src` to `dst`.
-///
-/// # Safety
-///
-/// This function has all the safety requirements of `core::ptr::copy` except
-/// that data races (both on `src` and `dst`) are explicitly permitted.
-#[inline(always)]
-unsafe fn rep_movs(src: usize, dst: usize, size: usize) {
-    unsafe {
-        asm!("rep movsb",
-            inout("rsi") src => _,
-            inout("rdi") dst => _,
-            inout("rcx") size => _,
-            options(nostack),
-        );
-    }
-}
-
-/// Set `size` bytes at `dst` to `val`.
-///
-/// # Safety
-///
-/// This function has all the safety requirements of `core::ptr::write_bytes` except
-/// that data races are explicitly permitted.
-#[inline(always)]
-unsafe fn rep_stosb(dst: usize, size: usize, value: u8) {
-    unsafe {
-        asm!("rep stosb",
-            inout("rdi") dst => _,
-            inout("rcx") size => _,
-            in("al") value,
-            options(nostack),
-        );
-    }
-}
-
 impl Clone for PageRef {
     /// Clones the [`PageRef`] instance, obtaining a new reference to the same memory page.
     fn clone(&self) -> Self {