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 <unistd.h>
34
35 #include "private/bionic_prctl.h"
36
37 // the multiplier should be power of 2
round_up(size_t size,size_t multiplier)38 static constexpr size_t round_up(size_t size, size_t multiplier) {
39 return (size + (multiplier - 1)) & ~(multiplier-1);
40 }
41
42 struct LinkerBlockAllocatorPage {
43 LinkerBlockAllocatorPage* next;
44 uint8_t bytes[PAGE_SIZE - 16] __attribute__((aligned(16)));
45 };
46
47 struct FreeBlockInfo {
48 void* next_block;
49 size_t num_free_blocks;
50 };
51
LinkerBlockAllocator(size_t block_size)52 LinkerBlockAllocator::LinkerBlockAllocator(size_t block_size)
53 : block_size_(
54 round_up(block_size < sizeof(FreeBlockInfo) ? sizeof(FreeBlockInfo) : block_size, 16)),
55 page_list_(nullptr),
56 free_block_list_(nullptr)
57 {}
58
alloc()59 void* LinkerBlockAllocator::alloc() {
60 if (free_block_list_ == nullptr) {
61 create_new_page();
62 }
63
64 FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(free_block_list_);
65 if (block_info->num_free_blocks > 1) {
66 FreeBlockInfo* next_block_info = reinterpret_cast<FreeBlockInfo*>(
67 reinterpret_cast<char*>(free_block_list_) + block_size_);
68 next_block_info->next_block = block_info->next_block;
69 next_block_info->num_free_blocks = block_info->num_free_blocks - 1;
70 free_block_list_ = next_block_info;
71 } else {
72 free_block_list_ = block_info->next_block;
73 }
74
75 memset(block_info, 0, block_size_);
76
77 return block_info;
78 }
79
free(void * block)80 void LinkerBlockAllocator::free(void* block) {
81 if (block == nullptr) {
82 return;
83 }
84
85 LinkerBlockAllocatorPage* page = find_page(block);
86
87 if (page == nullptr) {
88 abort();
89 }
90
91 ssize_t offset = reinterpret_cast<uint8_t*>(block) - page->bytes;
92
93 if (offset % block_size_ != 0) {
94 abort();
95 }
96
97 memset(block, 0, block_size_);
98
99 FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(block);
100
101 block_info->next_block = free_block_list_;
102 block_info->num_free_blocks = 1;
103
104 free_block_list_ = block_info;
105 }
106
protect_all(int prot)107 void LinkerBlockAllocator::protect_all(int prot) {
108 for (LinkerBlockAllocatorPage* page = page_list_; page != nullptr; page = page->next) {
109 if (mprotect(page, PAGE_SIZE, prot) == -1) {
110 abort();
111 }
112 }
113 }
114
create_new_page()115 void LinkerBlockAllocator::create_new_page() {
116 static_assert(sizeof(LinkerBlockAllocatorPage) == PAGE_SIZE,
117 "Invalid sizeof(LinkerBlockAllocatorPage)");
118
119 LinkerBlockAllocatorPage* page = reinterpret_cast<LinkerBlockAllocatorPage*>(
120 mmap(nullptr, PAGE_SIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0));
121
122 if (page == MAP_FAILED) {
123 abort(); // oom
124 }
125
126 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, page, PAGE_SIZE, "linker_alloc");
127
128 FreeBlockInfo* first_block = reinterpret_cast<FreeBlockInfo*>(page->bytes);
129 first_block->next_block = free_block_list_;
130 first_block->num_free_blocks = (PAGE_SIZE - sizeof(LinkerBlockAllocatorPage*))/block_size_;
131
132 free_block_list_ = first_block;
133
134 page->next = page_list_;
135 page_list_ = page;
136 }
137
find_page(void * block)138 LinkerBlockAllocatorPage* LinkerBlockAllocator::find_page(void* block) {
139 if (block == nullptr) {
140 abort();
141 }
142
143 LinkerBlockAllocatorPage* page = page_list_;
144 while (page != nullptr) {
145 const uint8_t* page_ptr = reinterpret_cast<const uint8_t*>(page);
146 if (block >= (page_ptr + sizeof(page->next)) && block < (page_ptr + PAGE_SIZE)) {
147 return page;
148 }
149
150 page = page->next;
151 }
152
153 abort();
154 }
155