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