1 // Copyright 2016 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef BASE_ALLOCATOR_ALLOCATOR_SHIM_H_ 6 #define BASE_ALLOCATOR_ALLOCATOR_SHIM_H_ 7 8 #include <stddef.h> 9 10 #include "base/base_export.h" 11 12 namespace base { 13 namespace allocator { 14 15 // Allocator Shim API. Allows to to: 16 // - Configure the behavior of the allocator (what to do on OOM failures). 17 // - Install new hooks (AllocatorDispatch) in the allocator chain. 18 19 // When this shim layer is enabled, the route of an allocation is as-follows: 20 // 21 // [allocator_shim_override_*.h] Intercept malloc() / operator new calls: 22 // The override_* headers define the symbols required to intercept calls to 23 // malloc() and operator new (if not overridden by specific C++ classes). 24 // 25 // [allocator_shim.cc] Routing allocation calls to the shim: 26 // The headers above route the calls to the internal ShimMalloc(), ShimFree(), 27 // ShimCppNew() etc. methods defined in allocator_shim.cc. 28 // These methods will: (1) forward the allocation call to the front of the 29 // AllocatorDispatch chain. (2) perform security hardenings (e.g., might 30 // call std::new_handler on OOM failure). 31 // 32 // [allocator_shim_default_dispatch_to_*.cc] The AllocatorDispatch chain: 33 // It is a singly linked list where each element is a struct with function 34 // pointers (|malloc_function|, |free_function|, etc). Normally the chain 35 // consists of a single AllocatorDispatch element, herein called 36 // the "default dispatch", which is statically defined at build time and 37 // ultimately routes the calls to the actual allocator defined by the build 38 // config (tcmalloc, glibc, ...). 39 // 40 // It is possible to dynamically insert further AllocatorDispatch stages 41 // to the front of the chain, for debugging / profiling purposes. 42 // 43 // All the functions must be thred safe. The shim does not enforce any 44 // serialization. This is to route to thread-aware allocators (e.g, tcmalloc) 45 // wihout introducing unnecessary perf hits. 46 47 struct AllocatorDispatch { 48 using AllocFn = void*(const AllocatorDispatch* self, size_t size); 49 using AllocZeroInitializedFn = void*(const AllocatorDispatch* self, 50 size_t n, 51 size_t size); 52 using AllocAlignedFn = void*(const AllocatorDispatch* self, 53 size_t alignment, 54 size_t size); 55 using ReallocFn = void*(const AllocatorDispatch* self, 56 void* address, 57 size_t size); 58 using FreeFn = void(const AllocatorDispatch* self, void* address); 59 60 AllocFn* const alloc_function; 61 AllocZeroInitializedFn* const alloc_zero_initialized_function; 62 AllocAlignedFn* const alloc_aligned_function; 63 ReallocFn* const realloc_function; 64 FreeFn* const free_function; 65 66 const AllocatorDispatch* next; 67 68 // |default_dispatch| is statically defined by one (and only one) of the 69 // allocator_shim_default_dispatch_to_*.cc files, depending on the build 70 // configuration. 71 static const AllocatorDispatch default_dispatch; 72 }; 73 74 // When true makes malloc behave like new, w.r.t calling the new_handler if 75 // the allocation fails (see set_new_mode() in Windows). 76 BASE_EXPORT void SetCallNewHandlerOnMallocFailure(bool value); 77 78 // Allocates |size| bytes or returns nullptr. It does NOT call the new_handler, 79 // regardless of SetCallNewHandlerOnMallocFailure(). 80 BASE_EXPORT void* UncheckedAlloc(size_t size); 81 82 // Inserts |dispatch| in front of the allocator chain. This method is NOT 83 // thread-safe w.r.t concurrent invocations of InsertAllocatorDispatch(). 84 // The callers have the responsibility of linearizing the changes to the chain 85 // (or more likely call these always on the same thread). 86 BASE_EXPORT void InsertAllocatorDispatch(AllocatorDispatch* dispatch); 87 88 // Test-only. Rationale: (1) lack of use cases; (2) dealing safely with a 89 // removal of arbitrary elements from a singly linked list would require a lock 90 // in malloc(), which we really don't want. 91 BASE_EXPORT void RemoveAllocatorDispatchForTesting(AllocatorDispatch* dispatch); 92 93 } // namespace allocator 94 } // namespace base 95 96 #endif // BASE_ALLOCATOR_ALLOCATOR_SHIM_H_ 97
