1/*
2 * Copyright (C) 2015 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
17#include "linker_allocator.h"
18#include "linker.h"
19
20#include <algorithm>
21#include <vector>
22
23#include <stdlib.h>
24#include <sys/mman.h>
25#include <unistd.h>
26
27#include "private/bionic_prctl.h"
28
29//
30// LinkerMemeoryAllocator is general purpose allocator
31// designed to provide the same functionality as the malloc/free/realloc
32// libc functions.
33//
34// On alloc:
35// If size is >= 1k allocator proxies malloc call directly to mmap
36// If size < 1k allocator uses SmallObjectAllocator for the size
37// rounded up to the nearest power of two.
38//
39// On free:
40//
41// For a pointer allocated using proxy-to-mmap allocator unmaps
42// the memory.
43//
44// For a pointer allocated using SmallObjectAllocator it adds
45// the block to free_blocks_list_. If the number of free pages reaches 2,
46// SmallObjectAllocator munmaps one of the pages keeping the other one
47// in reserve.
48
49static const char kSignature[4] = {'L', 'M', 'A', 1};
50
51static const size_t kSmallObjectMaxSize = 1 << kSmallObjectMaxSizeLog2;
52
53// This type is used for large allocations (with size >1k)
54static const uint32_t kLargeObject = 111;
55
56bool operator<(const small_object_page_record& one, const small_object_page_record& two) {
57  return one.page_addr < two.page_addr;
58}
59
60static inline uint16_t log2(size_t number) {
61  uint16_t result = 0;
62  number--;
63
64  while (number != 0) {
65    result++;
66    number >>= 1;
67  }
68
69  return result;
70}
71
72LinkerSmallObjectAllocator::LinkerSmallObjectAllocator()
73    : type_(0), block_size_(0), free_pages_cnt_(0), free_blocks_list_(nullptr) {}
74
75void* LinkerSmallObjectAllocator::alloc() {
76  if (free_blocks_list_ == nullptr) {
77    alloc_page();
78  }
79
80  small_object_block_record* block_record = free_blocks_list_;
81  if (block_record->free_blocks_cnt > 1) {
82    small_object_block_record* next_free = reinterpret_cast<small_object_block_record*>(
83        reinterpret_cast<uint8_t*>(block_record) + block_size_);
84    next_free->next = block_record->next;
85    next_free->free_blocks_cnt = block_record->free_blocks_cnt - 1;
86    free_blocks_list_ = next_free;
87  } else {
88    free_blocks_list_ = block_record->next;
89  }
90
91  // bookkeeping...
92  auto page_record = find_page_record(block_record);
93
94  if (page_record->allocated_blocks_cnt == 0) {
95    free_pages_cnt_--;
96  }
97
98  page_record->free_blocks_cnt--;
99  page_record->allocated_blocks_cnt++;
100
101  memset(block_record, 0, block_size_);
102
103  return block_record;
104}
105
106void LinkerSmallObjectAllocator::free_page(linker_vector_t::iterator page_record) {
107  void* page_start = reinterpret_cast<void*>(page_record->page_addr);
108  void* page_end = reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(page_start) + PAGE_SIZE);
109
110  while (free_blocks_list_ != nullptr &&
111      free_blocks_list_ > page_start &&
112      free_blocks_list_ < page_end) {
113    free_blocks_list_ = free_blocks_list_->next;
114  }
115
116  small_object_block_record* current = free_blocks_list_;
117
118  while (current != nullptr) {
119    while (current->next > page_start && current->next < page_end) {
120      current->next = current->next->next;
121    }
122
123    current = current->next;
124  }
125
126  munmap(page_start, PAGE_SIZE);
127  page_records_.erase(page_record);
128  free_pages_cnt_--;
129}
130
131void LinkerSmallObjectAllocator::free(void* ptr) {
132  auto page_record = find_page_record(ptr);
133
134  ssize_t offset = reinterpret_cast<uintptr_t>(ptr) - sizeof(page_info);
135
136  if (offset % block_size_ != 0) {
137    __libc_fatal("invalid pointer: %p (block_size=%zd)", ptr, block_size_);
138  }
139
140  memset(ptr, 0, block_size_);
141  small_object_block_record* block_record = reinterpret_cast<small_object_block_record*>(ptr);
142
143  block_record->next = free_blocks_list_;
144  block_record->free_blocks_cnt = 1;
145
146  free_blocks_list_ = block_record;
147
148  page_record->free_blocks_cnt++;
149  page_record->allocated_blocks_cnt--;
150
151  if (page_record->allocated_blocks_cnt == 0) {
152    if (free_pages_cnt_++ > 1) {
153      // if we already have a free page - unmap this one.
154      free_page(page_record);
155    }
156  }
157}
158
159void LinkerSmallObjectAllocator::init(uint32_t type, size_t block_size) {
160  type_ = type;
161  block_size_ = block_size;
162}
163
164linker_vector_t::iterator LinkerSmallObjectAllocator::find_page_record(void* ptr) {
165  void* addr = reinterpret_cast<void*>(PAGE_START(reinterpret_cast<uintptr_t>(ptr)));
166  small_object_page_record boundary;
167  boundary.page_addr = addr;
168  linker_vector_t::iterator it = std::lower_bound(
169      page_records_.begin(), page_records_.end(), boundary);
170
171  if (it == page_records_.end() || it->page_addr != addr) {
172    // not found...
173    __libc_fatal("page record for %p was not found (block_size=%zd)", ptr, block_size_);
174  }
175
176  return it;
177}
178
179void LinkerSmallObjectAllocator::create_page_record(void* page_addr, size_t free_blocks_cnt) {
180  small_object_page_record record;
181  record.page_addr = page_addr;
182  record.free_blocks_cnt = free_blocks_cnt;
183  record.allocated_blocks_cnt = 0;
184
185  linker_vector_t::iterator it = std::lower_bound(
186      page_records_.begin(), page_records_.end(), record);
187  page_records_.insert(it, record);
188}
189
190void LinkerSmallObjectAllocator::alloc_page() {
191  static_assert(sizeof(page_info) % 16 == 0,
192                "sizeof(page_info) is not multiple of 16");
193  void* map_ptr = mmap(nullptr, PAGE_SIZE,
194      PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
195  if (map_ptr == MAP_FAILED) {
196    __libc_fatal("mmap failed");
197  }
198
199  prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, map_ptr, PAGE_SIZE, "linker_alloc_small_objects");
200
201  memset(map_ptr, 0, PAGE_SIZE);
202
203  page_info* info = reinterpret_cast<page_info*>(map_ptr);
204  memcpy(info->signature, kSignature, sizeof(kSignature));
205  info->type = type_;
206  info->allocator_addr = this;
207
208  size_t free_blocks_cnt = (PAGE_SIZE - sizeof(page_info))/block_size_;
209
210  create_page_record(map_ptr, free_blocks_cnt);
211
212  small_object_block_record* first_block = reinterpret_cast<small_object_block_record*>(info + 1);
213
214  first_block->next = free_blocks_list_;
215  first_block->free_blocks_cnt = free_blocks_cnt;
216
217  free_blocks_list_ = first_block;
218}
219
220
221LinkerMemoryAllocator::LinkerMemoryAllocator() {
222  for (size_t i = 0; i < kSmallObjectAllocatorsCount; ++i) {
223    uint32_t type = i + kSmallObjectMinSizeLog2;
224    allocators_[i].init(type, 1 << type);
225  }
226}
227
228void* LinkerMemoryAllocator::alloc_mmap(size_t size) {
229  size_t allocated_size = PAGE_END(size + sizeof(page_info));
230  void* map_ptr = mmap(nullptr, allocated_size,
231      PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
232
233  if (map_ptr == MAP_FAILED) {
234    __libc_fatal("mmap failed");
235  }
236
237  prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, map_ptr, allocated_size, "linker_alloc_lob");
238
239  memset(map_ptr, 0, allocated_size);
240
241  page_info* info = reinterpret_cast<page_info*>(map_ptr);
242  memcpy(info->signature, kSignature, sizeof(kSignature));
243  info->type = kLargeObject;
244  info->allocated_size = allocated_size;
245
246  return info + 1;
247}
248
249void* LinkerMemoryAllocator::alloc(size_t size) {
250  // treat alloc(0) as alloc(1)
251  if (size == 0) {
252    size = 1;
253  }
254
255  if (size > kSmallObjectMaxSize) {
256    return alloc_mmap(size);
257  }
258
259  uint16_t log2_size = log2(size);
260
261  if (log2_size < kSmallObjectMinSizeLog2) {
262    log2_size = kSmallObjectMinSizeLog2;
263  }
264
265  return get_small_object_allocator(log2_size)->alloc();
266}
267
268page_info* LinkerMemoryAllocator::get_page_info(void* ptr) {
269  page_info* info = reinterpret_cast<page_info*>(PAGE_START(reinterpret_cast<size_t>(ptr)));
270  if (memcmp(info->signature, kSignature, sizeof(kSignature)) != 0) {
271    __libc_fatal("invalid pointer %p (page signature mismatch)", ptr);
272  }
273
274  return info;
275}
276
277void* LinkerMemoryAllocator::realloc(void* ptr, size_t size) {
278  if (ptr == nullptr) {
279    return alloc(size);
280  }
281
282  if (size == 0) {
283    free(ptr);
284    return nullptr;
285  }
286
287  page_info* info = get_page_info(ptr);
288
289  size_t old_size = 0;
290
291  if (info->type == kLargeObject) {
292    old_size = info->allocated_size - sizeof(page_info);
293  } else {
294    LinkerSmallObjectAllocator* allocator = get_small_object_allocator(info->type);
295    if (allocator != info->allocator_addr) {
296      __libc_fatal("invalid pointer %p (page signature mismatch)", ptr);
297    }
298
299    old_size = allocator->get_block_size();
300  }
301
302  if (old_size < size) {
303    void *result = alloc(size);
304    memcpy(result, ptr, old_size);
305    free(ptr);
306    return result;
307  }
308
309  return ptr;
310}
311
312void LinkerMemoryAllocator::free(void* ptr) {
313  if (ptr == nullptr) {
314    return;
315  }
316
317  page_info* info = get_page_info(ptr);
318
319  if (info->type == kLargeObject) {
320    munmap(info, info->allocated_size);
321  } else {
322    LinkerSmallObjectAllocator* allocator = get_small_object_allocator(info->type);
323    if (allocator != info->allocator_addr) {
324      __libc_fatal("invalid pointer %p (invalid allocator address for the page)", ptr);
325    }
326
327    allocator->free(ptr);
328  }
329}
330
331LinkerSmallObjectAllocator* LinkerMemoryAllocator::get_small_object_allocator(uint32_t type) {
332  if (type < kSmallObjectMinSizeLog2 || type > kSmallObjectMaxSizeLog2) {
333    __libc_fatal("invalid type: %u", type);
334  }
335
336  return &allocators_[type - kSmallObjectMinSizeLog2];
337}
338