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
31 #include <inttypes.h>
32 #include <string.h>
33 #include <sys/mman.h>
34 #include <sys/param.h>
35 #include <sys/prctl.h>
36 #include <unistd.h>
37
38 #include "linker_debug.h"
39
40 static constexpr size_t kAllocateSize = PAGE_SIZE * 100;
41 static_assert(kAllocateSize % PAGE_SIZE == 0, "Invalid kAllocateSize.");
42
43 struct LinkerBlockAllocatorPage {
44 LinkerBlockAllocatorPage* next;
45 uint8_t bytes[kAllocateSize - 16] __attribute__((aligned(16)));
46 };
47
48 struct FreeBlockInfo {
49 void* next_block;
50 size_t num_free_blocks;
51 };
52
53 static_assert(kBlockSizeAlign >= alignof(FreeBlockInfo));
54 static_assert(kBlockSizeMin == sizeof(FreeBlockInfo));
55
LinkerBlockAllocator(size_t block_size)56 LinkerBlockAllocator::LinkerBlockAllocator(size_t block_size)
57 : block_size_(__BIONIC_ALIGN(MAX(block_size, kBlockSizeMin), kBlockSizeAlign)),
58 page_list_(nullptr),
59 free_block_list_(nullptr),
60 allocated_(0) {}
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 CHECK(page != nullptr);
92
93 ssize_t offset = reinterpret_cast<uint8_t*>(block) - page->bytes;
94 CHECK((offset % block_size_) == 0);
95
96 memset(block, 0, block_size_);
97
98 FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(block);
99
100 block_info->next_block = free_block_list_;
101 block_info->num_free_blocks = 1;
102
103 free_block_list_ = block_info;
104
105 --allocated_;
106 }
107
protect_all(int prot)108 void LinkerBlockAllocator::protect_all(int prot) {
109 for (LinkerBlockAllocatorPage* page = page_list_; page != nullptr; page = page->next) {
110 if (mprotect(page, kAllocateSize, prot) == -1) {
111 async_safe_fatal("mprotect(%p, %zu, %d) failed: %m", page, kAllocateSize, prot);
112 }
113 }
114 }
115
create_new_page()116 void LinkerBlockAllocator::create_new_page() {
117 static_assert(sizeof(LinkerBlockAllocatorPage) == kAllocateSize,
118 "Invalid sizeof(LinkerBlockAllocatorPage)");
119
120 LinkerBlockAllocatorPage* page = reinterpret_cast<LinkerBlockAllocatorPage*>(
121 mmap(nullptr, kAllocateSize, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0));
122 CHECK(page != MAP_FAILED);
123
124 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, page, kAllocateSize, "linker_alloc");
125
126 FreeBlockInfo* first_block = reinterpret_cast<FreeBlockInfo*>(page->bytes);
127 first_block->next_block = free_block_list_;
128 first_block->num_free_blocks = sizeof(page->bytes) / block_size_;
129
130 free_block_list_ = first_block;
131
132 page->next = page_list_;
133 page_list_ = page;
134 }
135
find_page(void * block)136 LinkerBlockAllocatorPage* LinkerBlockAllocator::find_page(void* block) {
137 CHECK(block != nullptr);
138
139 LinkerBlockAllocatorPage* page = page_list_;
140 while (page != nullptr) {
141 const uint8_t* page_ptr = reinterpret_cast<const uint8_t*>(page);
142 if (block >= (page_ptr + sizeof(page->next)) && block < (page_ptr + kAllocateSize)) {
143 return page;
144 }
145
146 page = page->next;
147 }
148
149 async_safe_fatal("couldn't find page for %p", block);
150 }
151
purge()152 void LinkerBlockAllocator::purge() {
153 if (allocated_) {
154 return;
155 }
156
157 LinkerBlockAllocatorPage* page = page_list_;
158 while (page) {
159 LinkerBlockAllocatorPage* next = page->next;
160 munmap(page, kAllocateSize);
161 page = next;
162 }
163 page_list_ = nullptr;
164 free_block_list_ = nullptr;
165 }
166