1 // Copyright (c) 2009, 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 //
8 // * Redistributions of source code must retain the above copyright
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.
14 // * Neither the name of Google Inc. nor the names of its
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
26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 #ifndef GOOGLE_BREAKPAD_COMMON_MEMORY_H_
31 #define GOOGLE_BREAKPAD_COMMON_MEMORY_H_
32
33 #include <stdint.h>
34 #include <stdlib.h>
35 #include <unistd.h>
36 #include <sys/mman.h>
37
38 #include <memory>
39 #include <vector>
40
41 #if defined(MEMORY_SANITIZER)
42 #include <sanitizer/msan_interface.h>
43 #endif
44
45 #ifdef __APPLE__
46 #define sys_mmap mmap
47 #define sys_mmap2 mmap
48 #define sys_munmap munmap
49 #define MAP_ANONYMOUS MAP_ANON
50 #else
51 #include "third_party/lss/linux_syscall_support.h"
52 #endif
53
54 namespace google_breakpad {
55
56 // This is very simple allocator which fetches pages from the kernel directly.
57 // Thus, it can be used even when the heap may be corrupted.
58 //
59 // There is no free operation. The pages are only freed when the object is
60 // destroyed.
61 class PageAllocator {
62 public:
PageAllocator()63 PageAllocator()
64 : page_size_(getpagesize()),
65 last_(NULL),
66 current_page_(NULL),
67 page_offset_(0) {
68 }
69
~PageAllocator()70 ~PageAllocator() {
71 FreeAll();
72 }
73
Alloc(size_t bytes)74 void *Alloc(size_t bytes) {
75 if (!bytes)
76 return NULL;
77
78 if (current_page_ && page_size_ - page_offset_ >= bytes) {
79 uint8_t *const ret = current_page_ + page_offset_;
80 page_offset_ += bytes;
81 if (page_offset_ == page_size_) {
82 page_offset_ = 0;
83 current_page_ = NULL;
84 }
85
86 return ret;
87 }
88
89 const size_t pages =
90 (bytes + sizeof(PageHeader) + page_size_ - 1) / page_size_;
91 uint8_t *const ret = GetNPages(pages);
92 if (!ret)
93 return NULL;
94
95 page_offset_ =
96 (page_size_ - (page_size_ * pages - (bytes + sizeof(PageHeader)))) %
97 page_size_;
98 current_page_ = page_offset_ ? ret + page_size_ * (pages - 1) : NULL;
99
100 return ret + sizeof(PageHeader);
101 }
102
103 // Checks whether the page allocator owns the passed-in pointer.
104 // This method exists for testing pursposes only.
OwnsPointer(const void * p)105 bool OwnsPointer(const void* p) {
106 for (PageHeader* header = last_; header; header = header->next) {
107 const char* current = reinterpret_cast<char*>(header);
108 if ((p >= current) && (p < current + header->num_pages * page_size_))
109 return true;
110 }
111
112 return false;
113 }
114
115 private:
GetNPages(size_t num_pages)116 uint8_t *GetNPages(size_t num_pages) {
117 #if defined(__x86_64__) || defined(__aarch64__) || defined(__aarch64__) || \
118 ((defined(__mips__) && _MIPS_SIM == _ABI64))
119 void *a = sys_mmap(NULL, page_size_ * num_pages, PROT_READ | PROT_WRITE,
120 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
121 #else
122 void *a = sys_mmap2(NULL, page_size_ * num_pages, PROT_READ | PROT_WRITE,
123 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
124 #endif
125 if (a == MAP_FAILED)
126 return NULL;
127
128 #if defined(MEMORY_SANITIZER)
129 // We need to indicate to MSan that memory allocated through sys_mmap is
130 // initialized, since linux_syscall_support.h doesn't have MSan hooks.
131 __msan_unpoison(a, page_size_ * num_pages);
132 #endif
133
134 struct PageHeader *header = reinterpret_cast<PageHeader*>(a);
135 header->next = last_;
136 header->num_pages = num_pages;
137 last_ = header;
138
139 return reinterpret_cast<uint8_t*>(a);
140 }
141
FreeAll()142 void FreeAll() {
143 PageHeader *next;
144
145 for (PageHeader *cur = last_; cur; cur = next) {
146 next = cur->next;
147 sys_munmap(cur, cur->num_pages * page_size_);
148 }
149 }
150
151 struct PageHeader {
152 PageHeader *next; // pointer to the start of the next set of pages.
153 size_t num_pages; // the number of pages in this set.
154 };
155
156 const size_t page_size_;
157 PageHeader *last_;
158 uint8_t *current_page_;
159 size_t page_offset_;
160 };
161
162 // Wrapper to use with STL containers
163 template <typename T>
164 struct PageStdAllocator : public std::allocator<T> {
165 typedef typename std::allocator<T>::pointer pointer;
166 typedef typename std::allocator<T>::size_type size_type;
167
PageStdAllocatorPageStdAllocator168 explicit PageStdAllocator(PageAllocator& allocator): allocator_(allocator) {}
PageStdAllocatorPageStdAllocator169 template <class Other> PageStdAllocator(const PageStdAllocator<Other>& other)
170 : allocator_(other.allocator_) {}
171
172 inline pointer allocate(size_type n, const void* = 0) {
173 return static_cast<pointer>(allocator_.Alloc(sizeof(T) * n));
174 }
175
deallocatePageStdAllocator176 inline void deallocate(pointer, size_type) {
177 // The PageAllocator doesn't free.
178 }
179
180 template <typename U> struct rebind {
181 typedef PageStdAllocator<U> other;
182 };
183
184 private:
185 // Silly workaround for the gcc from Android's ndk (gcc 4.6), which will
186 // otherwise complain that `other.allocator_` is private in the constructor
187 // code.
188 template<typename Other> friend struct PageStdAllocator;
189
190 PageAllocator& allocator_;
191 };
192
193 // A wasteful vector is a std::vector, except that it allocates memory from a
194 // PageAllocator. It's wasteful because, when resizing, it always allocates a
195 // whole new array since the PageAllocator doesn't support realloc.
196 template<class T>
197 class wasteful_vector : public std::vector<T, PageStdAllocator<T> > {
198 public:
199 wasteful_vector(PageAllocator* allocator, unsigned size_hint = 16)
200 : std::vector<T, PageStdAllocator<T> >(PageStdAllocator<T>(*allocator)) {
201 std::vector<T, PageStdAllocator<T> >::reserve(size_hint);
202 }
203 };
204
205 } // namespace google_breakpad
206
new(size_t nbytes,google_breakpad::PageAllocator & allocator)207 inline void* operator new(size_t nbytes,
208 google_breakpad::PageAllocator& allocator) {
209 return allocator.Alloc(nbytes);
210 }
211
212 #endif // GOOGLE_BREAKPAD_COMMON_MEMORY_H_
213