1 /*
2  * Copyright (C) 2015 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 #pragma once
30 
31 #include <sys/cdefs.h>
32 #include <stddef.h>
33 #include <stdint.h>
34 
35 const uint32_t kSmallObjectMaxSizeLog2 = 10;
36 const uint32_t kSmallObjectMinSizeLog2 = 4;
37 const uint32_t kSmallObjectAllocatorsCount = kSmallObjectMaxSizeLog2 - kSmallObjectMinSizeLog2 + 1;
38 
39 class BionicSmallObjectAllocator;
40 
41 // This structure is placed at the beginning of each addressable page
42 // and has all information we need to find the corresponding memory allocator.
43 struct page_info {
44   char signature[4];
45   uint32_t type;
46   union {
47     // we use allocated_size for large objects allocator
48     size_t allocated_size;
49     // and allocator_addr for small ones.
50     BionicSmallObjectAllocator* allocator_addr;
51   };
52 };
53 
54 struct small_object_block_record {
55   small_object_block_record* next;
56   size_t free_blocks_cnt;
57 };
58 
59 // This structure is placed at the beginning of each page managed by
60 // BionicSmallObjectAllocator.  Note that a page_info struct is expected at the
61 // beginning of each page as well, and therefore this structure contains a
62 // page_info as its *first* field.
63 struct small_object_page_info {
64   page_info info;  // Must be the first field.
65 
66   // Doubly linked list for traversing all pages allocated by a
67   // BionicSmallObjectAllocator.
68   small_object_page_info* next_page;
69   small_object_page_info* prev_page;
70 
71   // Linked list containing all free blocks in this page.
72   small_object_block_record* free_block_list;
73 
74   // Free blocks counter.
75   size_t free_blocks_cnt;
76 };
77 
78 class BionicSmallObjectAllocator {
79  public:
80   BionicSmallObjectAllocator(uint32_t type, size_t block_size);
81   void* alloc();
82   void free(void* ptr);
83 
get_block_size()84   size_t get_block_size() const { return block_size_; }
85  private:
86   void alloc_page();
87   void free_page(small_object_page_info* page);
88   void add_to_page_list(small_object_page_info* page);
89   void remove_from_page_list(small_object_page_info* page);
90 
91   const uint32_t type_;
92   const size_t block_size_;
93   const size_t blocks_per_page_;
94 
95   size_t free_pages_cnt_;
96 
97   small_object_page_info* page_list_;
98 };
99 
100 class BionicAllocator {
101  public:
BionicAllocator()102   constexpr BionicAllocator() : allocators_(nullptr), allocators_buf_() {}
103   void* alloc(size_t size);
104   void* memalign(size_t align, size_t size);
105 
106   // Note that this implementation of realloc never shrinks allocation
107   void* realloc(void* ptr, size_t size);
108   void free(void* ptr);
109 
110   // Returns the size of the given allocated heap chunk, if it is valid.
111   // Otherwise, this may return 0 or cause a segfault if the pointer is invalid.
112   size_t get_chunk_size(void* ptr);
113 
114  private:
115   void* alloc_mmap(size_t align, size_t size);
116   inline void* alloc_impl(size_t align, size_t size);
117   inline page_info* get_page_info_unchecked(void* ptr);
118   inline page_info* get_page_info(void* ptr);
119   BionicSmallObjectAllocator* get_small_object_allocator_unchecked(uint32_t type);
120   BionicSmallObjectAllocator* get_small_object_allocator(page_info* pi, void* ptr);
121   void initialize_allocators();
122 
123   BionicSmallObjectAllocator* allocators_;
124   uint8_t allocators_buf_[sizeof(BionicSmallObjectAllocator)*kSmallObjectAllocatorsCount];
125 };
126