vm-allocator: Add page size related functions

To avoid code duplication extract page related functions to their
own module and add utility functions for manipulating addresses
related to page sizes

Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>

vm-allocator/src/lib.rs

@@ -12,6 +12,8 @@
 
 mod address;
 mod gsi;
+/// page size related utility funtions
+pub mod page_size;
 mod system;
 
 pub use crate::address::AddressAllocator;

vm-allocator/src/page_size.rs

@@ -0,0 +1,38 @@
+// Copyright 2023 Arm Limited (or its affiliates). All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+use libc::{sysconf, _SC_PAGESIZE};
+
+/// get host page size
+pub fn get_page_size() -> u64 {
+    // SAFETY: FFI call. Trivially safe.
+    unsafe { sysconf(_SC_PAGESIZE) as u64 }
+}
+
+/// round up address to let it align page size
+pub fn align_page_size_up(address: u64) -> u64 {
+    let page_size = get_page_size();
+    (address + page_size - 1) & !(page_size - 1)
+}
+
+/// round down address to let it align page size
+pub fn align_page_size_down(address: u64) -> u64 {
+    let page_size = get_page_size();
+    address & !(page_size - 1)
+}
+
+/// Test if address is 4k aligned
+pub fn is_4k_aligned(address: u64) -> bool {
+    (address & 0xfff) == 0
+}
+
+/// Test if size is 4k aligned
+pub fn is_4k_multiple(size: u64) -> bool {
+    (size & 0xfff) == 0
+}
+
+/// Test if address is page size aligned
+pub fn is_page_size_aligned(address: u64) -> bool {
+    let page_size = get_page_size();
+    address & (page_size - 1) == 0
+}

vm-allocator/src/system.rs

@@ -14,14 +14,7 @@ use crate::gsi::GsiAllocator;
 #[cfg(target_arch = "x86_64")]
 use crate::gsi::GsiApic;
 
-use libc::{sysconf, _SC_PAGESIZE};
-
-/// Safe wrapper for `sysconf(_SC_PAGESIZE)`.
-#[inline(always)]
-fn pagesize() -> usize {
-    // SAFETY: FFI call. Trivially safe.
-    unsafe { sysconf(_SC_PAGESIZE) as usize }
-}
+use crate::page_size::get_page_size;
 
 /// Manages allocating system resources such as address space and interrupt numbers.
 ///
@@ -126,7 +119,7 @@ impl SystemAllocator {
         self.platform_mmio_address_space.allocate(
             address,
             size,
-            Some(align_size.unwrap_or(pagesize() as u64)),
+            Some(align_size.unwrap_or(get_page_size())),
         )
     }
 
@@ -140,7 +133,7 @@ impl SystemAllocator {
         self.mmio_hole_address_space.allocate(
             address,
             size,
-            Some(align_size.unwrap_or(pagesize() as u64)),
+            Some(align_size.unwrap_or(get_page_size())),
         )
     }