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/prctl.h>
35 #include <unistd.h>
36
37 #include "linker_debug.h"
38
39 static constexpr size_t kAllocateSize = PAGE_SIZE * 100;
40 static_assert(kAllocateSize % PAGE_SIZE == 0, "Invalid kAllocateSize.");
41
42 // the multiplier should be power of 2
round_up(size_t size,size_t multiplier)43 static constexpr size_t round_up(size_t size, size_t multiplier) {
44 return (size + (multiplier - 1)) & ~(multiplier-1);
45 }
46
47 struct LinkerBlockAllocatorPage {
48 LinkerBlockAllocatorPage* next;
49 uint8_t bytes[kAllocateSize - 16] __attribute__((aligned(16)));
50 };
51
52 struct FreeBlockInfo {
53 void* next_block;
54 size_t num_free_blocks;
55 };
56
LinkerBlockAllocator(size_t block_size)57 LinkerBlockAllocator::LinkerBlockAllocator(size_t block_size)
58 : block_size_(
59 round_up(block_size < sizeof(FreeBlockInfo) ? sizeof(FreeBlockInfo) : block_size, 16)),
60 page_list_(nullptr),
61 free_block_list_(nullptr),
62 allocated_(0)
63 {}
64
alloc()65 void* LinkerBlockAllocator::alloc() {
66 if (free_block_list_ == nullptr) {
67 create_new_page();
68 }
69
70 FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(free_block_list_);
71 if (block_info->num_free_blocks > 1) {
72 FreeBlockInfo* next_block_info = reinterpret_cast<FreeBlockInfo*>(
73 reinterpret_cast<char*>(free_block_list_) + block_size_);
74 next_block_info->next_block = block_info->next_block;
75 next_block_info->num_free_blocks = block_info->num_free_blocks - 1;
76 free_block_list_ = next_block_info;
77 } else {
78 free_block_list_ = block_info->next_block;
79 }
80
81 memset(block_info, 0, block_size_);
82
83 ++allocated_;
84
85 return block_info;
86 }
87
free(void * block)88 void LinkerBlockAllocator::free(void* block) {
89 if (block == nullptr) {
90 return;
91 }
92
93 LinkerBlockAllocatorPage* page = find_page(block);
94 CHECK(page != nullptr);
95
96 ssize_t offset = reinterpret_cast<uint8_t*>(block) - page->bytes;
97 CHECK((offset % block_size_) == 0);
98
99 memset(block, 0, block_size_);
100
101 FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(block);
102
103 block_info->next_block = free_block_list_;
104 block_info->num_free_blocks = 1;
105
106 free_block_list_ = block_info;
107
108 --allocated_;
109 }
110
protect_all(int prot)111 void LinkerBlockAllocator::protect_all(int prot) {
112 for (LinkerBlockAllocatorPage* page = page_list_; page != nullptr; page = page->next) {
113 if (mprotect(page, kAllocateSize, prot) == -1) {
114 async_safe_fatal("mprotect(%p, %zu, %d) failed: %m", page, kAllocateSize, prot);
115 }
116 }
117 }
118
create_new_page()119 void LinkerBlockAllocator::create_new_page() {
120 static_assert(sizeof(LinkerBlockAllocatorPage) == kAllocateSize,
121 "Invalid sizeof(LinkerBlockAllocatorPage)");
122
123 LinkerBlockAllocatorPage* page = reinterpret_cast<LinkerBlockAllocatorPage*>(
124 mmap(nullptr, kAllocateSize, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0));
125 CHECK(page != MAP_FAILED);
126
127 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, page, kAllocateSize, "linker_alloc");
128
129 FreeBlockInfo* first_block = reinterpret_cast<FreeBlockInfo*>(page->bytes);
130 first_block->next_block = free_block_list_;
131 first_block->num_free_blocks = sizeof(page->bytes) / block_size_;
132
133 free_block_list_ = first_block;
134
135 page->next = page_list_;
136 page_list_ = page;
137 }
138
find_page(void * block)139 LinkerBlockAllocatorPage* LinkerBlockAllocator::find_page(void* block) {
140 CHECK(block != nullptr);
141
142 LinkerBlockAllocatorPage* page = page_list_;
143 while (page != nullptr) {
144 const uint8_t* page_ptr = reinterpret_cast<const uint8_t*>(page);
145 if (block >= (page_ptr + sizeof(page->next)) && block < (page_ptr + kAllocateSize)) {
146 return page;
147 }
148
149 page = page->next;
150 }
151
152 async_safe_fatal("couldn't find page for %p", block);
153 }
154
purge()155 void LinkerBlockAllocator::purge() {
156 if (allocated_) {
157 return;
158 }
159
160 LinkerBlockAllocatorPage* page = page_list_;
161 while (page) {
162 LinkerBlockAllocatorPage* next = page->next;
163 munmap(page, kAllocateSize);
164 page = next;
165 }
166 page_list_ = nullptr;
167 free_block_list_ = nullptr;
168 }
169