1 // Copyright (c) 2006, Google Inc.
2 // All rights reserved.
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:
7 //
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9 // notice, this list of conditions and the following disclaimer.
10 //     * Redistributions in binary form must reproduce the above
11 // copyright notice, this list of conditions and the following disclaimer
12 // in the documentation and/or other materials provided with the
13 // distribution.
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15 // contributors may be used to endorse or promote products derived from
16 // this software without specific prior written permission.
17 //
18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 //
30 // ProtectedMemoryAllocator
31 //
32 // See the header file for documentation
33 
34 #include "protected_memory_allocator.h"
35 #include <assert.h>
36 
37 //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
38 ProtectedMemoryAllocator::ProtectedMemoryAllocator(vm_size_t pool_size)
39   : pool_size_(pool_size),
40     next_alloc_offset_(0),
41     valid_(false) {
42 
43   kern_return_t result = vm_allocate(mach_task_self(),
44                                      &base_address_,
45                                      pool_size,
46                                      TRUE
47                                      );
48 
49   valid_ = (result == KERN_SUCCESS);
50   assert(valid_);
51 }
52 
53 //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
54 ProtectedMemoryAllocator::~ProtectedMemoryAllocator() {
55   vm_deallocate(mach_task_self(),
56                 base_address_,
57                 pool_size_
58                 );
59 }
60 
61 //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
62 char *ProtectedMemoryAllocator::Allocate(vm_size_t bytes) {
63   if (valid_ && next_alloc_offset_ + bytes <= pool_size_) {
64     char *p = (char*)base_address_ + next_alloc_offset_;
65     next_alloc_offset_ += bytes;
66     return p;
67   }
68 
69   return NULL;  // ran out of memory in our allocation block
70 }
71 
72 //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
73 kern_return_t  ProtectedMemoryAllocator::Protect() {
74   kern_return_t result = vm_protect(mach_task_self(),
75                                     base_address_,
76                                     pool_size_,
77                                     FALSE,
78                                     VM_PROT_READ);
79 
80   return result;
81 }
82 
83 //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
84 kern_return_t  ProtectedMemoryAllocator::Unprotect() {
85   kern_return_t result = vm_protect(mach_task_self(),
86                                     base_address_,
87                                     pool_size_,
88                                     FALSE,
89                                     VM_PROT_READ | VM_PROT_WRITE);
90 
91   return result;
92 }
93