bc23e530c4
Freeing block mprotects on the page which it turn may lead to application crash if linker subsequently tries to modify another block on the page. Bug: 14895266 Change-Id: I8ff7f5df467d7be184242de652032b3c84e24b76
131 lines
3.5 KiB
C++
131 lines
3.5 KiB
C++
/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "linker_allocator.h"
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#include <inttypes.h>
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#include <sys/mman.h>
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#include <unistd.h>
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struct LinkerAllocatorPage {
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LinkerAllocatorPage* next;
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uint8_t bytes[PAGE_SIZE-sizeof(LinkerAllocatorPage*)];
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};
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struct FreeBlockInfo {
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void* next_block;
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size_t num_free_blocks;
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};
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LinkerBlockAllocator::LinkerBlockAllocator()
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: block_size_(0),
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page_list_(nullptr),
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free_block_list_(nullptr)
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{}
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void LinkerBlockAllocator::init(size_t block_size) {
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block_size_ = block_size < sizeof(FreeBlockInfo) ? sizeof(FreeBlockInfo) : block_size;
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}
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void* LinkerBlockAllocator::alloc() {
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if (free_block_list_ == nullptr) {
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create_new_page();
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}
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FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(free_block_list_);
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if (block_info->num_free_blocks > 1) {
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FreeBlockInfo* next_block_info = reinterpret_cast<FreeBlockInfo*>(
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reinterpret_cast<char*>(free_block_list_) + block_size_);
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next_block_info->next_block = block_info->next_block;
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next_block_info->num_free_blocks = block_info->num_free_blocks - 1;
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free_block_list_ = next_block_info;
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} else {
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free_block_list_ = block_info->next_block;
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}
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block_info->next_block = nullptr;
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block_info->num_free_blocks = 0;
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return block_info;
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}
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void LinkerBlockAllocator::free(void* block) {
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if (block == nullptr) {
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return;
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}
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LinkerAllocatorPage* page = find_page(block);
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if (page == nullptr) {
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abort();
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}
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ssize_t offset = reinterpret_cast<uint8_t*>(block) - page->bytes;
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if (offset % block_size_ != 0) {
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abort();
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}
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FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(block);
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block_info->next_block = free_block_list_;
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block_info->num_free_blocks = 1;
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free_block_list_ = block_info;
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}
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void LinkerBlockAllocator::protect_all(int prot) {
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for (LinkerAllocatorPage* page = page_list_; page != nullptr; page = page->next) {
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if (mprotect(page, PAGE_SIZE, prot) == -1) {
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abort();
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}
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}
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}
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void LinkerBlockAllocator::create_new_page() {
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LinkerAllocatorPage* page = reinterpret_cast<LinkerAllocatorPage*>(mmap(nullptr, PAGE_SIZE,
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PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0));
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if (page == MAP_FAILED) {
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abort(); // oom
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}
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FreeBlockInfo* first_block = reinterpret_cast<FreeBlockInfo*>(page->bytes);
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first_block->next_block = free_block_list_;
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first_block->num_free_blocks = (PAGE_SIZE - sizeof(LinkerAllocatorPage*))/block_size_;
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free_block_list_ = first_block;
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page->next = page_list_;
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page_list_ = page;
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}
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LinkerAllocatorPage* LinkerBlockAllocator::find_page(void* block) {
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if (block == nullptr) {
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abort();
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}
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LinkerAllocatorPage* page = page_list_;
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const uint8_t* page_ptr = reinterpret_cast<const uint8_t*>(page);
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while (page != nullptr) {
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if (block >= (page_ptr + sizeof(page->next)) && block < (page_ptr + PAGE_SIZE)) {
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return page;
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}
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page = page->next;
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}
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abort();
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}
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