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externals/breakpad/src/common/memory_allocator.h

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+// Copyright 2009 Google LLC
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google LLC nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_BREAKPAD_COMMON_MEMORY_ALLOCATOR_H_
+#define GOOGLE_BREAKPAD_COMMON_MEMORY_ALLOCATOR_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/mman.h>
+
+#include <memory>
+#include <vector>
+
+#if defined(MEMORY_SANITIZER)
+#include <sanitizer/msan_interface.h>
+#endif
+
+#ifdef __APPLE__
+#define sys_mmap mmap
+#define sys_munmap munmap
+#define MAP_ANONYMOUS MAP_ANON
+#else
+#include "third_party/lss/linux_syscall_support.h"
+#endif
+
+namespace google_breakpad {
+
+// This is very simple allocator which fetches pages from the kernel directly.
+// Thus, it can be used even when the heap may be corrupted.
+//
+// There is no free operation. The pages are only freed when the object is
+// destroyed.
+class PageAllocator {
+ public:
+  PageAllocator()
+      : page_size_(getpagesize()),
+        last_(NULL),
+        current_page_(NULL),
+        page_offset_(0),
+        pages_allocated_(0) {
+  }
+
+  ~PageAllocator() {
+    FreeAll();
+  }
+
+  void* Alloc(size_t bytes) {
+    if (!bytes)
+      return NULL;
+
+    if (current_page_ && page_size_ - page_offset_ >= bytes) {
+      uint8_t* const ret = current_page_ + page_offset_;
+      page_offset_ += bytes;
+      if (page_offset_ == page_size_) {
+        page_offset_ = 0;
+        current_page_ = NULL;
+      }
+
+      return ret;
+    }
+
+    const size_t pages =
+        (bytes + sizeof(PageHeader) + page_size_ - 1) / page_size_;
+    uint8_t* const ret = GetNPages(pages);
+    if (!ret)
+      return NULL;
+
+    page_offset_ =
+        (page_size_ - (page_size_ * pages - (bytes + sizeof(PageHeader)))) %
+        page_size_;
+    current_page_ = page_offset_ ? ret + page_size_ * (pages - 1) : NULL;
+
+    return ret + sizeof(PageHeader);
+  }
+
+  // Checks whether the page allocator owns the passed-in pointer.
+  // This method exists for testing pursposes only.
+  bool OwnsPointer(const void* p) {
+    for (PageHeader* header = last_; header; header = header->next) {
+      const char* current = reinterpret_cast<char*>(header);
+      if ((p >= current) && (p < current + header->num_pages * page_size_))
+        return true;
+    }
+
+    return false;
+  }
+
+  unsigned long pages_allocated() { return pages_allocated_; }
+
+ private:
+  uint8_t* GetNPages(size_t num_pages) {
+    void* a = sys_mmap(NULL, page_size_ * num_pages, PROT_READ | PROT_WRITE,
+                       MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+    if (a == MAP_FAILED)
+      return NULL;
+
+#if defined(MEMORY_SANITIZER)
+    // We need to indicate to MSan that memory allocated through sys_mmap is
+    // initialized, since linux_syscall_support.h doesn't have MSan hooks.
+    __msan_unpoison(a, page_size_ * num_pages);
+#endif
+
+    struct PageHeader* header = reinterpret_cast<PageHeader*>(a);
+    header->next = last_;
+    header->num_pages = num_pages;
+    last_ = header;
+
+    pages_allocated_ += num_pages;
+
+    return reinterpret_cast<uint8_t*>(a);
+  }
+
+  void FreeAll() {
+    PageHeader* next;
+
+    for (PageHeader* cur = last_; cur; cur = next) {
+      next = cur->next;
+      sys_munmap(cur, cur->num_pages * page_size_);
+    }
+  }
+
+  struct PageHeader {
+    PageHeader* next;  // pointer to the start of the next set of pages.
+    size_t num_pages;  // the number of pages in this set.
+  };
+
+  const size_t page_size_;
+  PageHeader* last_;
+  uint8_t* current_page_;
+  size_t page_offset_;
+  unsigned long pages_allocated_;
+};
+
+// Wrapper to use with STL containers
+template <typename T>
+struct PageStdAllocator {
+  using AllocatorTraits = std::allocator_traits<std::allocator<T>>;
+  using value_type = typename AllocatorTraits::value_type;
+  using pointer = typename AllocatorTraits::pointer;
+  using difference_type = typename AllocatorTraits::difference_type;
+  using size_type = typename AllocatorTraits::size_type;
+
+  explicit PageStdAllocator(PageAllocator& allocator) : allocator_(allocator),
+                                                        stackdata_(NULL),
+                                                        stackdata_size_(0)
+  {}
+
+  template <class Other> PageStdAllocator(const PageStdAllocator<Other>& other)
+      : allocator_(other.allocator_),
+        stackdata_(nullptr),
+        stackdata_size_(0)
+  {}
+
+  explicit PageStdAllocator(PageAllocator& allocator,
+                            pointer stackdata,
+                            size_type stackdata_size) : allocator_(allocator),
+      stackdata_(stackdata),
+      stackdata_size_(stackdata_size)
+  {}
+
+  inline pointer allocate(size_type n, const void* = 0) {
+    const size_type size = sizeof(T) * n;
+    if (size <= stackdata_size_) {
+      return stackdata_;
+    }
+    return static_cast<pointer>(allocator_.Alloc(size));
+  }
+
+  inline void deallocate(pointer, size_type) {
+    // The PageAllocator doesn't free.
+  }
+
+  template <typename U> struct rebind {
+    typedef PageStdAllocator<U> other;
+  };
+
+ private:
+  // Silly workaround for the gcc from Android's ndk (gcc 4.6), which will
+  // otherwise complain that `other.allocator_` is private in the constructor
+  // code.
+  template<typename Other> friend struct PageStdAllocator;
+
+  PageAllocator& allocator_;
+  pointer stackdata_;
+  size_type stackdata_size_;
+};
+
+// A wasteful vector is a std::vector, except that it allocates memory from a
+// PageAllocator. It's wasteful because, when resizing, it always allocates a
+// whole new array since the PageAllocator doesn't support realloc.
+template<class T>
+class wasteful_vector : public std::vector<T, PageStdAllocator<T> > {
+ public:
+  wasteful_vector(PageAllocator* allocator, unsigned size_hint = 16)
+      : std::vector<T, PageStdAllocator<T> >(PageStdAllocator<T>(*allocator)) {
+    std::vector<T, PageStdAllocator<T> >::reserve(size_hint);
+  }
+ protected:
+  wasteful_vector(PageStdAllocator<T> allocator)
+      : std::vector<T, PageStdAllocator<T> >(allocator) {}
+};
+
+// auto_wasteful_vector allocates space on the stack for N entries to avoid
+// using the PageAllocator for small data, while still allowing for larger data.
+template<class T, unsigned int N>
+class auto_wasteful_vector : public wasteful_vector<T> {
+ T stackdata_[N];
+ public:
+  auto_wasteful_vector(PageAllocator* allocator)
+      : wasteful_vector<T>(
+            PageStdAllocator<T>(*allocator,
+                                &stackdata_[0],
+                                sizeof(stackdata_))) {
+    std::vector<T, PageStdAllocator<T> >::reserve(N);
+  }
+};
+
+}  // namespace google_breakpad
+
+inline void* operator new(size_t nbytes,
+                          google_breakpad::PageAllocator& allocator) {
+  return allocator.Alloc(nbytes);
+}
+
+#endif  // GOOGLE_BREAKPAD_COMMON_MEMORY_ALLOCATOR_H_