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/*
* Copyright (C) 2014 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "linker_block_allocator.h"
#include <inttypes.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#include <unistd.h>
#include "linker_debug.h"
static constexpr size_t kAllocateSize = PAGE_SIZE * 100;
static_assert(kAllocateSize % PAGE_SIZE == 0, "Invalid kAllocateSize.");
// the multiplier should be power of 2
static constexpr size_t round_up(size_t size, size_t multiplier) {
return (size + (multiplier - 1)) & ~(multiplier-1);
}
struct LinkerBlockAllocatorPage {
LinkerBlockAllocatorPage* next;
uint8_t bytes[kAllocateSize - 16] __attribute__((aligned(16)));
};
struct FreeBlockInfo {
void* next_block;
size_t num_free_blocks;
};
LinkerBlockAllocator::LinkerBlockAllocator(size_t block_size)
: block_size_(
round_up(block_size < sizeof(FreeBlockInfo) ? sizeof(FreeBlockInfo) : block_size, 16)),
page_list_(nullptr),
free_block_list_(nullptr),
allocated_(0)
{}
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_);
++allocated_;
return block_info;
}
void LinkerBlockAllocator::free(void* block) {
if (block == nullptr) {
return;
}
LinkerBlockAllocatorPage* page = find_page(block);
CHECK(page != nullptr);
ssize_t offset = reinterpret_cast<uint8_t*>(block) - page->bytes;
CHECK((offset % block_size_) == 0);
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;
--allocated_;
}
void LinkerBlockAllocator::protect_all(int prot) {
for (LinkerBlockAllocatorPage* page = page_list_; page != nullptr; page = page->next) {
if (mprotect(page, kAllocateSize, prot) == -1) {
async_safe_fatal("mprotect(%p, %zu, %d) failed: %m", page, kAllocateSize, prot);
}
}
}
void LinkerBlockAllocator::create_new_page() {
static_assert(sizeof(LinkerBlockAllocatorPage) == kAllocateSize,
"Invalid sizeof(LinkerBlockAllocatorPage)");
LinkerBlockAllocatorPage* page = reinterpret_cast<LinkerBlockAllocatorPage*>(
mmap(nullptr, kAllocateSize, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0));
CHECK(page != MAP_FAILED);
prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, page, kAllocateSize, "linker_alloc");
FreeBlockInfo* first_block = reinterpret_cast<FreeBlockInfo*>(page->bytes);
first_block->next_block = free_block_list_;
first_block->num_free_blocks = sizeof(page->bytes) / block_size_;
free_block_list_ = first_block;
page->next = page_list_;
page_list_ = page;
}
LinkerBlockAllocatorPage* LinkerBlockAllocator::find_page(void* block) {
CHECK(block != nullptr);
LinkerBlockAllocatorPage* 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 + kAllocateSize)) {
return page;
}
page = page->next;
}
async_safe_fatal("couldn't find page for %p", block);
}
void LinkerBlockAllocator::purge() {
if (allocated_) {
return;
}
LinkerBlockAllocatorPage* page = page_list_;
while (page) {
LinkerBlockAllocatorPage* next = page->next;
munmap(page, kAllocateSize);
page = next;
}
page_list_ = nullptr;
free_block_list_ = nullptr;
}
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