forked from 0ad/0ad
94 lines
2.9 KiB
C++
94 lines
2.9 KiB
C++
/* Copyright (c) 2011 Wildfire Games
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#ifndef INCLUDED_ALLOCATORS_OVERRUN_PROTECTOR
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#define INCLUDED_ALLOCATORS_OVERRUN_PROTECTOR
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#include "lib/config2.h" // CONFIG2_ALLOCATORS_OVERRUN_PROTECTION
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#include "lib/sysdep/vm.h"
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/**
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OverrunProtector wraps an arbitrary object in isolated page(s) and
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can detect inadvertent writes to it. this is useful for
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tracking down memory overruns.
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the basic idea is to require users to request access to the object and
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notify us when done; memory access permission is temporarily granted.
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(similar in principle to Software Transaction Memory).
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since this is quite slow, the protection is disabled unless
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CONFIG2_ALLOCATORS_OVERRUN_PROTECTION == 1; this avoids having to remove the
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wrapper code in release builds and re-write when looking for overruns.
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example usage:
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OverrunProtector\<T\> wrapper;
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..
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T* p = wrapper.get(); // unlock, make ready for use
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if(!p) // wrapper's one-time alloc of a T-
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abort(); // instance had failed - can't continue.
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DoSomethingWith(p); // (read/write access)
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wrapper.lock(); // disallow further access until next .get()
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..
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**/
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template<class T> class OverrunProtector
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{
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NONCOPYABLE(OverrunProtector); // const member
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public:
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OverrunProtector()
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: object(new(vm::Allocate(sizeof(T))) T())
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{
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lock();
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}
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~OverrunProtector()
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{
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unlock();
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object->~T(); // call dtor (since we used placement new)
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vm::Free(object, sizeof(T));
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}
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T* get() const
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{
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unlock();
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return object;
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}
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void lock() const
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{
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#if CONFIG2_ALLOCATORS_OVERRUN_PROTECTION
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vm::Protect(object, sizeof(T), PROT_NONE);
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#endif
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}
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private:
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void unlock() const
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{
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#if CONFIG2_ALLOCATORS_OVERRUN_PROTECTION
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vm::Protect(object, sizeof(T), PROT_READ|PROT_WRITE);
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#endif
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}
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T* const object;
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};
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#endif // #ifndef INCLUDED_ALLOCATORS_OVERRUN_PROTECTOR
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