src/mem/backdoor.hh

   1 /*
   2  * Copyright 2019 Google, Inc.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met: redistributions of source code must retain the above copyright
   7  * notice, this list of conditions and the following disclaimer;
   8  * redistributions in binary form must reproduce the above copyright
   9  * notice, this list of conditions and the following disclaimer in the
  10  * documentation and/or other materials provided with the distribution;
  11  * neither the name of the copyright holders nor the names of its
  12  * contributors may be used to endorse or promote products derived from
  13  * this software without specific prior written permission.
  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 FOR
  18  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  19  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  20  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  21  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  25  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  */
  27
  28 #ifndef __MEM_BACKDOOR_HH__
  29 #define __MEM_BACKDOOR_HH__
  30
  31 #include <cstdint>
  32 #include <functional>
  33 #include <memory>
  34
  35 #include "base/addr_range.hh"
  36 #include "base/callback.hh"
  37
  38 class MemBackdoor
  39 {
  40   public:
  41     // Callbacks from this back door are set up using a callable which accepts
  42     // a const reference to this back door as their only parameter.
  43     typedef std::function<void(const MemBackdoor &backdoor)> CbFunction;
  44
  45   public:
  46     enum Flags{
  47         // How data is allowed to be accessed through this backdoor.
  48         NoAccess = 0x0,
  49         Readable = 0x1,
  50         Writeable = 0x2
  51     };
  52
  53     // The range in the guest address space covered by this back door.
  54     const AddrRange &range() const { return _range; }
  55     void range(const AddrRange &r) { _range = r; }
  56
  57     // A pointer to the data accessible through this back door.
  58     uint8_t *ptr() const { return _ptr; }
  59     void ptr(uint8_t *p) { _ptr = p; }
  60
  61     /*
  62      * Helper functions to make it easier to set/check particular flags.
  63      */
  64
  65     bool readable() const { return _flags & Readable; }
  66     void
  67     readable(bool r)
  68     {
  69         if (r)
  70             _flags = (Flags)(_flags | Readable);
  71         else
  72             _flags = (Flags)(_flags & ~Readable);
  73     }
  74
  75     bool writeable() const { return _flags & Writeable; }
  76     void
  77     writeable(bool w)
  78     {
  79         if (w)
  80             _flags = (Flags)(_flags | Writeable);
  81         else
  82             _flags = (Flags)(_flags & ~Writeable);
  83     }
  84
  85     Flags flags() const { return _flags; }
  86     void flags(Flags f) { _flags = f; }
  87
  88     MemBackdoor(AddrRange r, uint8_t *p, Flags flags) :
  89         _range(r), _ptr(p), _flags(flags)
  90     {}
  91
  92     MemBackdoor() : MemBackdoor(AddrRange(), nullptr, NoAccess)
  93     {}
  94
  95     // Set up a callable to be called when this back door is invalidated. This
  96     // lets holders update their bookkeeping to remove any references to it,
  97     // and/or to propogate that invalidation to other interested parties.
  98     void
  99     addInvalidationCallback(CbFunction func)
 100     {
 101         invalidationCallbacks.push_back([this,func](){ func(*this); });
 102     }
 103
 104     // Notify and clear invalidation callbacks when the data in the backdoor
 105     // structure is no longer valid/current. The backdoor might then be
 106     // updated or even deleted without having to worry about stale data being
 107     // used.
 108     void
 109     invalidate()
 110     {
 111         invalidationCallbacks.process();
 112         invalidationCallbacks.clear();
 113     }
 114
 115   private:
 116     CallbackQueue invalidationCallbacks;
 117
 118     AddrRange _range;
 119     uint8_t *_ptr;
 120     Flags _flags;
 121 };
 122
 123 typedef MemBackdoor *MemBackdoorPtr;
 124
 125 #endif  //__MEM_BACKDOOR_HH__