1 // Copyright 2006 Google LLC 2 // 3 // Redistribution and use in source and binary forms, with or without 4 // modification, are permitted provided that the following conditions are 5 // met: 6 // 7 // * Redistributions of source code must retain the above copyright 8 // notice, this list of conditions and the following disclaimer. 9 // * Redistributions in binary form must reproduce the above 10 // copyright notice, this list of conditions and the following disclaimer 11 // in the documentation and/or other materials provided with the 12 // distribution. 13 // * Neither the name of Google LLC nor the names of its 14 // contributors may be used to endorse or promote products derived from 15 // this software without specific prior written permission. 16 // 17 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 18 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 19 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 20 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 21 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 22 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 23 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 27 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 // 29 // ProtectedMemoryAllocator 30 // 31 // A very simple allocator class which allows allocation, but not deallocation. 32 // The allocations can be made read-only with the Protect() method. 33 // This class is NOT useful as a general-purpose memory allocation system, 34 // since it does not allow deallocation. It is useful to use for a group 35 // of allocations which are created in the same time-frame and destroyed 36 // in the same time-frame. It is useful for making allocations of memory 37 // which will not need to change often once initialized. This memory can then 38 // be protected from memory smashers by calling the Protect() method. 39 40 #ifndef PROTECTED_MEMORY_ALLOCATOR_H__ 41 #define PROTECTED_MEMORY_ALLOCATOR_H__ 42 43 #include <mach/mach.h> 44 45 // 46 class ProtectedMemoryAllocator { 47 public: 48 ProtectedMemoryAllocator(vm_size_t pool_size); 49 ~ProtectedMemoryAllocator(); 50 51 // Returns a pointer to an allocation of size n within the pool. 52 // Fails by returning NULL is no more space is available. 53 // Please note that the pointers returned from this method should not 54 // be freed in any way (for example by calling free() on them ). 55 char * Allocate(vm_size_t n); 56 57 // Returns the base address of the allocation pool. GetBaseAddress()58 char * GetBaseAddress() { return (char*)base_address_; } 59 60 // Returns the size of the allocation pool, including allocated 61 // plus free space. GetTotalSize()62 vm_size_t GetTotalSize() { return pool_size_; } 63 64 // Returns the number of bytes already allocated in the pool. GetAllocatedSize()65 vm_size_t GetAllocatedSize() { return next_alloc_offset_; } 66 67 // Returns the number of bytes available for allocation. GetFreeSize()68 vm_size_t GetFreeSize() { return pool_size_ - next_alloc_offset_; } 69 70 // Makes the entire allocation pool read-only including, of course, 71 // all allocations made from the pool. 72 kern_return_t Protect(); 73 74 // Makes the entire allocation pool read/write. 75 kern_return_t Unprotect(); 76 77 private: 78 vm_size_t pool_size_; 79 vm_address_t base_address_; 80 vm_size_t next_alloc_offset_; 81 bool valid_; 82 }; 83 84 #endif // PROTECTED_MEMORY_ALLOCATOR_H__ 85