/* * Copyright (C) 2014 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. */ #include "linker_allocator.h" #include #include #include struct LinkerAllocatorPage { LinkerAllocatorPage* next; uint8_t bytes[PAGE_SIZE-sizeof(LinkerAllocatorPage*)]; }; struct FreeBlockInfo { void* next_block; size_t num_free_blocks; }; LinkerBlockAllocator::LinkerBlockAllocator() : block_size_(0), page_list_(nullptr), free_block_list_(nullptr) {} void LinkerBlockAllocator::init(size_t block_size) { block_size_ = block_size < sizeof(FreeBlockInfo) ? sizeof(FreeBlockInfo) : block_size; } void* LinkerBlockAllocator::alloc() { if (free_block_list_ == nullptr) { create_new_page(); } FreeBlockInfo* block_info = reinterpret_cast(free_block_list_); if (block_info->num_free_blocks > 1) { FreeBlockInfo* next_block_info = reinterpret_cast( reinterpret_cast(free_block_list_) + block_size_); next_block_info->next_block = block_info->next_block; next_block_info->num_free_blocks = block_info->num_free_blocks - 1; free_block_list_ = next_block_info; } else { free_block_list_ = block_info->next_block; } memset(block_info, 0, block_size_); return block_info; } void LinkerBlockAllocator::free(void* block) { if (block == nullptr) { return; } LinkerAllocatorPage* page = find_page(block); if (page == nullptr) { abort(); } ssize_t offset = reinterpret_cast(block) - page->bytes; if (offset % block_size_ != 0) { abort(); } memset(block, 0, block_size_); FreeBlockInfo* block_info = reinterpret_cast(block); block_info->next_block = free_block_list_; block_info->num_free_blocks = 1; free_block_list_ = block_info; } void LinkerBlockAllocator::protect_all(int prot) { for (LinkerAllocatorPage* page = page_list_; page != nullptr; page = page->next) { if (mprotect(page, PAGE_SIZE, prot) == -1) { abort(); } } } void LinkerBlockAllocator::create_new_page() { LinkerAllocatorPage* page = reinterpret_cast(mmap(nullptr, PAGE_SIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0)); if (page == MAP_FAILED) { abort(); // oom } memset(page, 0, PAGE_SIZE); FreeBlockInfo* first_block = reinterpret_cast(page->bytes); first_block->next_block = free_block_list_; first_block->num_free_blocks = (PAGE_SIZE - sizeof(LinkerAllocatorPage*))/block_size_; free_block_list_ = first_block; page->next = page_list_; page_list_ = page; } LinkerAllocatorPage* LinkerBlockAllocator::find_page(void* block) { if (block == nullptr) { abort(); } LinkerAllocatorPage* page = page_list_; while (page != nullptr) { const uint8_t* page_ptr = reinterpret_cast(page); if (block >= (page_ptr + sizeof(page->next)) && block < (page_ptr + PAGE_SIZE)) { return page; } page = page->next; } abort(); }