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      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:
     84   LinkerTypeAllocator() : block_allocator_(sizeof(T)) {}
     85   T* alloc() { return reinterpret_cast<T*>(block_allocator_.alloc()); }
     86   void free(T* t) { block_allocator_.free(t); }
     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