1/* 2 * Copyright (C) 2014 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16#include "linker_allocator.h" 17#include <inttypes.h> 18#include <sys/mman.h> 19#include <unistd.h> 20 21#include "private/bionic_prctl.h" 22 23struct LinkerAllocatorPage { 24 LinkerAllocatorPage* next; 25 uint8_t bytes[PAGE_SIZE-sizeof(LinkerAllocatorPage*)]; 26}; 27 28struct FreeBlockInfo { 29 void* next_block; 30 size_t num_free_blocks; 31}; 32 33LinkerBlockAllocator::LinkerBlockAllocator(size_t block_size) 34 : block_size_(block_size < sizeof(FreeBlockInfo) ? sizeof(FreeBlockInfo) : block_size), 35 page_list_(nullptr), 36 free_block_list_(nullptr) 37{} 38 39void* LinkerBlockAllocator::alloc() { 40 if (free_block_list_ == nullptr) { 41 create_new_page(); 42 } 43 44 FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(free_block_list_); 45 if (block_info->num_free_blocks > 1) { 46 FreeBlockInfo* next_block_info = reinterpret_cast<FreeBlockInfo*>( 47 reinterpret_cast<char*>(free_block_list_) + block_size_); 48 next_block_info->next_block = block_info->next_block; 49 next_block_info->num_free_blocks = block_info->num_free_blocks - 1; 50 free_block_list_ = next_block_info; 51 } else { 52 free_block_list_ = block_info->next_block; 53 } 54 55 memset(block_info, 0, block_size_); 56 57 return block_info; 58} 59 60void LinkerBlockAllocator::free(void* block) { 61 if (block == nullptr) { 62 return; 63 } 64 65 LinkerAllocatorPage* page = find_page(block); 66 67 if (page == nullptr) { 68 abort(); 69 } 70 71 ssize_t offset = reinterpret_cast<uint8_t*>(block) - page->bytes; 72 73 if (offset % block_size_ != 0) { 74 abort(); 75 } 76 77 memset(block, 0, block_size_); 78 79 FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(block); 80 81 block_info->next_block = free_block_list_; 82 block_info->num_free_blocks = 1; 83 84 free_block_list_ = block_info; 85} 86 87void LinkerBlockAllocator::protect_all(int prot) { 88 for (LinkerAllocatorPage* page = page_list_; page != nullptr; page = page->next) { 89 if (mprotect(page, PAGE_SIZE, prot) == -1) { 90 abort(); 91 } 92 } 93} 94 95void LinkerBlockAllocator::create_new_page() { 96 LinkerAllocatorPage* page = reinterpret_cast<LinkerAllocatorPage*>(mmap(nullptr, PAGE_SIZE, 97 PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0)); 98 if (page == MAP_FAILED) { 99 abort(); // oom 100 } 101 102 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, page, PAGE_SIZE, "linker_alloc"); 103 104 memset(page, 0, PAGE_SIZE); 105 106 FreeBlockInfo* first_block = reinterpret_cast<FreeBlockInfo*>(page->bytes); 107 first_block->next_block = free_block_list_; 108 first_block->num_free_blocks = (PAGE_SIZE - sizeof(LinkerAllocatorPage*))/block_size_; 109 110 free_block_list_ = first_block; 111 112 page->next = page_list_; 113 page_list_ = page; 114} 115 116LinkerAllocatorPage* LinkerBlockAllocator::find_page(void* block) { 117 if (block == nullptr) { 118 abort(); 119 } 120 121 LinkerAllocatorPage* page = page_list_; 122 while (page != nullptr) { 123 const uint8_t* page_ptr = reinterpret_cast<const uint8_t*>(page); 124 if (block >= (page_ptr + sizeof(page->next)) && block < (page_ptr + PAGE_SIZE)) { 125 return page; 126 } 127 128 page = page->next; 129 } 130 131 abort(); 132} 133