1 // Copyright 2024, The Android Open Source Project
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 /// The size of a 4KB memory in bytes.
16 pub const SIZE_4KB: usize = 4 << 10;
17
18 #[cfg(target_arch = "aarch64")]
19 /// Computes the largest multiple of the provided alignment smaller or equal to the address.
20 ///
21 /// Note: the result is undefined if alignment isn't a power of two.
unchecked_align_down(addr: usize, alignment: usize) -> usize22 pub const fn unchecked_align_down(addr: usize, alignment: usize) -> usize {
23 addr & !(alignment - 1)
24 }
25
26 #[cfg(target_arch = "aarch64")]
27 /// Computes the address of the 4KiB page containing a given address.
page_4kb_of(addr: usize) -> usize28 pub const fn page_4kb_of(addr: usize) -> usize {
29 unchecked_align_down(addr, SIZE_4KB)
30 }
31