1 /*
2 * Copyright (C) 2014 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include "linker_block_allocator.h"
30 #include <inttypes.h>
31 #include <string.h>
32 #include <sys/mman.h>
33 #include <sys/prctl.h>
34 #include <unistd.h>
35
36 static constexpr size_t kAllocateSize = PAGE_SIZE * 100;
37 static_assert(kAllocateSize % PAGE_SIZE == 0, "Invalid kAllocateSize.");
38
39 // the multiplier should be power of 2
round_up(size_t size,size_t multiplier)40 static constexpr size_t round_up(size_t size, size_t multiplier) {
41 return (size + (multiplier - 1)) & ~(multiplier-1);
42 }
43
44 struct LinkerBlockAllocatorPage {
45 LinkerBlockAllocatorPage* next;
46 uint8_t bytes[kAllocateSize - 16] __attribute__((aligned(16)));
47 };
48
49 struct FreeBlockInfo {
50 void* next_block;
51 size_t num_free_blocks;
52 };
53
LinkerBlockAllocator(size_t block_size)54 LinkerBlockAllocator::LinkerBlockAllocator(size_t block_size)
55 : block_size_(
56 round_up(block_size < sizeof(FreeBlockInfo) ? sizeof(FreeBlockInfo) : block_size, 16)),
57 page_list_(nullptr),
58 free_block_list_(nullptr),
59 allocated_(0)
60 {}
61
alloc()62 void* LinkerBlockAllocator::alloc() {
63 if (free_block_list_ == nullptr) {
64 create_new_page();
65 }
66
67 FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(free_block_list_);
68 if (block_info->num_free_blocks > 1) {
69 FreeBlockInfo* next_block_info = reinterpret_cast<FreeBlockInfo*>(
70 reinterpret_cast<char*>(free_block_list_) + block_size_);
71 next_block_info->next_block = block_info->next_block;
72 next_block_info->num_free_blocks = block_info->num_free_blocks - 1;
73 free_block_list_ = next_block_info;
74 } else {
75 free_block_list_ = block_info->next_block;
76 }
77
78 memset(block_info, 0, block_size_);
79
80 ++allocated_;
81
82 return block_info;
83 }
84
free(void * block)85 void LinkerBlockAllocator::free(void* block) {
86 if (block == nullptr) {
87 return;
88 }
89
90 LinkerBlockAllocatorPage* page = find_page(block);
91
92 if (page == nullptr) {
93 abort();
94 }
95
96 ssize_t offset = reinterpret_cast<uint8_t*>(block) - page->bytes;
97
98 if (offset % block_size_ != 0) {
99 abort();
100 }
101
102 memset(block, 0, block_size_);
103
104 FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(block);
105
106 block_info->next_block = free_block_list_;
107 block_info->num_free_blocks = 1;
108
109 free_block_list_ = block_info;
110
111 --allocated_;
112 }
113
protect_all(int prot)114 void LinkerBlockAllocator::protect_all(int prot) {
115 for (LinkerBlockAllocatorPage* page = page_list_; page != nullptr; page = page->next) {
116 if (mprotect(page, kAllocateSize, prot) == -1) {
117 abort();
118 }
119 }
120 }
121
create_new_page()122 void LinkerBlockAllocator::create_new_page() {
123 static_assert(sizeof(LinkerBlockAllocatorPage) == kAllocateSize,
124 "Invalid sizeof(LinkerBlockAllocatorPage)");
125
126 LinkerBlockAllocatorPage* page = reinterpret_cast<LinkerBlockAllocatorPage*>(
127 mmap(nullptr, kAllocateSize, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0));
128
129 if (page == MAP_FAILED) {
130 abort(); // oom
131 }
132
133 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, page, kAllocateSize, "linker_alloc");
134
135 FreeBlockInfo* first_block = reinterpret_cast<FreeBlockInfo*>(page->bytes);
136 first_block->next_block = free_block_list_;
137 first_block->num_free_blocks = sizeof(page->bytes) / block_size_;
138
139 free_block_list_ = first_block;
140
141 page->next = page_list_;
142 page_list_ = page;
143 }
144
find_page(void * block)145 LinkerBlockAllocatorPage* LinkerBlockAllocator::find_page(void* block) {
146 if (block == nullptr) {
147 abort();
148 }
149
150 LinkerBlockAllocatorPage* page = page_list_;
151 while (page != nullptr) {
152 const uint8_t* page_ptr = reinterpret_cast<const uint8_t*>(page);
153 if (block >= (page_ptr + sizeof(page->next)) && block < (page_ptr + kAllocateSize)) {
154 return page;
155 }
156
157 page = page->next;
158 }
159
160 abort();
161 }
162
purge()163 void LinkerBlockAllocator::purge() {
164 if (allocated_) {
165 return;
166 }
167
168 LinkerBlockAllocatorPage* page = page_list_;
169 while (page) {
170 LinkerBlockAllocatorPage* next = page->next;
171 munmap(page, kAllocateSize);
172 page = next;
173 }
174 page_list_ = nullptr;
175 free_block_list_ = nullptr;
176 }
177