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/*
* 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 <inttypes.h>
#include <sys/mman.h>
#include <unistd.h>
#include "private/bionic_prctl.h"
struct LinkerAllocatorPage {
LinkerAllocatorPage* next;
uint8_t bytes[PAGE_SIZE-sizeof(LinkerAllocatorPage*)];
};
struct FreeBlockInfo {
void* next_block;
size_t num_free_blocks;
};
LinkerBlockAllocator::LinkerBlockAllocator(size_t block_size)
: block_size_(block_size < sizeof(FreeBlockInfo) ? sizeof(FreeBlockInfo) : block_size),
page_list_(nullptr),
free_block_list_(nullptr)
{}
void* LinkerBlockAllocator::alloc() {
if (free_block_list_ == nullptr) {
create_new_page();
}
FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(free_block_list_);
if (block_info->num_free_blocks > 1) {
FreeBlockInfo* next_block_info = reinterpret_cast<FreeBlockInfo*>(
reinterpret_cast<char*>(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<uint8_t*>(block) - page->bytes;
if (offset % block_size_ != 0) {
abort();
}
memset(block, 0, block_size_);
FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(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<LinkerAllocatorPage*>(mmap(nullptr, PAGE_SIZE,
PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0));
if (page == MAP_FAILED) {
abort(); // oom
}
prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, page, PAGE_SIZE, "linker_alloc");
memset(page, 0, PAGE_SIZE);
FreeBlockInfo* first_block = reinterpret_cast<FreeBlockInfo*>(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<const uint8_t*>(page);
if (block >= (page_ptr + sizeof(page->next)) && block < (page_ptr + PAGE_SIZE)) {
return page;
}
page = page->next;
}
abort();
}
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