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 #ifndef __LINKER_BLOCK_ALLOCATOR_H
30 #define __LINKER_BLOCK_ALLOCATOR_H
31 
32 #include <stdlib.h>
33 #include <limits.h>
34 #include "private/bionic_macros.h"
35 
36 struct LinkerBlockAllocatorPage;
37 
38 /*
39  * This class is a non-template version of the LinkerTypeAllocator
40  * It keeps code inside .cpp file by keeping the interface
41  * template-free.
42  *
43  * Please use LinkerTypeAllocator<type> where possible (everywhere).
44  */
45 class LinkerBlockAllocator {
46  public:
47   explicit LinkerBlockAllocator(size_t block_size);
48 
49   void* alloc();
50   void free(void* block);
51   void protect_all(int prot);
52 
53  private:
54   void create_new_page();
55   LinkerBlockAllocatorPage* find_page(void* block);
56 
57   size_t block_size_;
58   LinkerBlockAllocatorPage* page_list_;
59   void* free_block_list_;
60 
61   DISALLOW_COPY_AND_ASSIGN(LinkerBlockAllocator);
62 };
63 
64 /*
65  * A simple allocator for the dynamic linker. An allocator allocates instances
66  * of a single fixed-size type. Allocations are backed by page-sized private
67  * anonymous mmaps.
68  *
69  * The differences between this allocator and LinkerMemoryAllocator are:
70  * 1. This allocator manages space more efficiently. LinkerMemoryAllocator
71  *    operates in power-of-two sized blocks up to 1k, when this implementation
72  *    splits the page to aligned size of structure; For example for structures
73  *    with size 513 this allocator will use 516 (520 for lp64) bytes of data
74  *    where generalized implementation is going to use 1024 sized blocks.
75  *
76  * 2. This allocator does not munmap allocated memory, where LinkerMemoryAllocator does.
77  *
78  * 3. This allocator provides mprotect services to the user, where LinkerMemoryAllocator
79  *    always treats it's memory as READ|WRITE.
80  */
81 template<typename T>
82 class LinkerTypeAllocator {
83  public:
LinkerTypeAllocator()84   LinkerTypeAllocator() : block_allocator_(sizeof(T)) {}
alloc()85   T* alloc() { return reinterpret_cast<T*>(block_allocator_.alloc()); }
free(T * t)86   void free(T* t) { block_allocator_.free(t); }
protect_all(int prot)87   void protect_all(int prot) { block_allocator_.protect_all(prot); }
88  private:
89   LinkerBlockAllocator block_allocator_;
90   DISALLOW_COPY_AND_ASSIGN(LinkerTypeAllocator);
91 };
92 
93 #endif // __LINKER_BLOCK_ALLOCATOR_H
94