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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 #include "linker_allocator.h"
     30 
     31 #include <stdlib.h>
     32 #include <sys/cdefs.h>
     33 #include <unistd.h>
     34 
     35 #include <atomic>
     36 
     37 #include <async_safe/log.h>
     38 
     39 static LinkerMemoryAllocator g_linker_allocator;
     40 static std::atomic<pid_t> fallback_tid(0);
     41 
     42 // Used by libdebuggerd_handler to switch allocators during a crash dump, in
     43 // case the linker heap is corrupted. Do not use this function.
     44 extern "C" bool __linker_enable_fallback_allocator() {
     45   pid_t expected = 0;
     46   return fallback_tid.compare_exchange_strong(expected, gettid());
     47 }
     48 
     49 extern "C" void __linker_disable_fallback_allocator() {
     50   pid_t previous = fallback_tid.exchange(0);
     51   if (previous == 0) {
     52     async_safe_fatal("attempted to disable unused fallback allocator");
     53   } else if (previous != gettid()) {
     54     async_safe_fatal("attempted to disable fallback allocator in use by another thread (%d)",
     55                      previous);
     56   }
     57 }
     58 
     59 static LinkerMemoryAllocator& get_fallback_allocator() {
     60   static LinkerMemoryAllocator fallback_allocator;
     61   return fallback_allocator;
     62 }
     63 
     64 static LinkerMemoryAllocator& get_allocator() {
     65   if (__predict_false(fallback_tid) && __predict_false(gettid() == fallback_tid)) {
     66     return get_fallback_allocator();
     67   }
     68   return g_linker_allocator;
     69 }
     70 
     71 void* malloc(size_t byte_count) {
     72   return get_allocator().alloc(byte_count);
     73 }
     74 
     75 void* calloc(size_t item_count, size_t item_size) {
     76   return get_allocator().alloc(item_count*item_size);
     77 }
     78 
     79 void* realloc(void* p, size_t byte_count) {
     80   return get_allocator().realloc(p, byte_count);
     81 }
     82 
     83 void free(void* ptr) {
     84   get_allocator().free(ptr);
     85 }
     86 
     87