| /* |
| * Copyright (C) 2015 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #pragma once |
| |
| #include <stddef.h> |
| #include <stdint.h> |
| #include <sys/auxv.h> |
| |
| // For PAGE_SIZE. |
| #include <sys/user.h> |
| |
| inline size_t page_size() { |
| #if defined(PAGE_SIZE) |
| return PAGE_SIZE; |
| #else |
| static const size_t page_size = getauxval(AT_PAGESZ); |
| return page_size; |
| #endif |
| } |
| |
| // The maximum page size supported on any Android device. As |
| // of API level 35, this is limited by ART. |
| constexpr size_t max_android_page_size() { |
| #if defined(PAGE_SIZE) |
| return PAGE_SIZE; |
| #else |
| return 16384; |
| #endif |
| } |
| |
| // Returns the address of the page containing address 'x'. |
| inline uintptr_t page_start(uintptr_t x) { |
| return x & ~(page_size() - 1); |
| } |
| |
| // Returns the offset of address 'x' in its page. |
| inline uintptr_t page_offset(uintptr_t x) { |
| return x & (page_size() - 1); |
| } |
| |
| // Returns the address of the next page after address 'x', unless 'x' is |
| // itself at the start of a page. |
| inline uintptr_t page_end(uintptr_t x) { |
| return page_start(x + page_size() - 1); |
| } |