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Diffstat (limited to 'security/sandbox/chromium/base/memory/shared_memory_mapping.h')
| -rw-r--r-- | security/sandbox/chromium/base/memory/shared_memory_mapping.h | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/security/sandbox/chromium/base/memory/shared_memory_mapping.h b/security/sandbox/chromium/base/memory/shared_memory_mapping.h new file mode 100644 index 0000000000..2b8858e166 --- /dev/null +++ b/security/sandbox/chromium/base/memory/shared_memory_mapping.h @@ -0,0 +1,252 @@ +// Copyright 2018 The Chromium Authors. All rights reserved. +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. + +#ifndef BASE_MEMORY_SHARED_MEMORY_MAPPING_H_ +#define BASE_MEMORY_SHARED_MEMORY_MAPPING_H_ + +#include <cstddef> +#include <type_traits> + +#include "base/containers/buffer_iterator.h" +#include "base/containers/span.h" +#include "base/macros.h" +#include "base/unguessable_token.h" + +namespace base { + +namespace subtle { +class PlatformSharedMemoryRegion; +} // namespace subtle + +// Base class for scoped handles to a shared memory mapping created from a +// shared memory region. Created shared memory mappings remain valid even if the +// creator region is transferred or destroyed. +// +// Each mapping has an UnguessableToken that identifies the shared memory region +// it was created from. This is used for memory metrics, to avoid overcounting +// shared memory. +class BASE_EXPORT SharedMemoryMapping { + public: + // Default constructor initializes an invalid instance. + SharedMemoryMapping(); + + // Move operations are allowed. + SharedMemoryMapping(SharedMemoryMapping&& mapping) noexcept; + SharedMemoryMapping& operator=(SharedMemoryMapping&& mapping) noexcept; + + // Unmaps the region if the mapping is valid. + virtual ~SharedMemoryMapping(); + + // Returns true iff the mapping is valid. False means there is no + // corresponding area of memory. + bool IsValid() const { return memory_ != nullptr; } + + // Returns the logical size of the mapping in bytes. This is precisely the + // size requested by whoever created the mapping, and it is always less than + // or equal to |mapped_size()|. This is undefined for invalid instances. + size_t size() const { + DCHECK(IsValid()); + return size_; + } + + // Returns the actual size of the mapping in bytes. This is always at least + // as large as |size()| but may be larger due to platform mapping alignment + // constraints. This is undefined for invalid instances. + size_t mapped_size() const { + DCHECK(IsValid()); + return mapped_size_; + } + + // Returns 128-bit GUID of the region this mapping belongs to. + const UnguessableToken& guid() const { + DCHECK(IsValid()); + return guid_; + } + + protected: + SharedMemoryMapping(void* address, + size_t size, + size_t mapped_size, + const UnguessableToken& guid); + void* raw_memory_ptr() const { return memory_; } + + private: + friend class SharedMemoryTracker; + + void Unmap(); + + void* memory_ = nullptr; + size_t size_ = 0; + size_t mapped_size_ = 0; + UnguessableToken guid_; + + DISALLOW_COPY_AND_ASSIGN(SharedMemoryMapping); +}; + +// Class modeling a read-only mapping of a shared memory region into the +// current process' address space. This is created by ReadOnlySharedMemoryRegion +// instances. +class BASE_EXPORT ReadOnlySharedMemoryMapping : public SharedMemoryMapping { + public: + // Default constructor initializes an invalid instance. + ReadOnlySharedMemoryMapping(); + + // Move operations are allowed. + ReadOnlySharedMemoryMapping(ReadOnlySharedMemoryMapping&&) noexcept; + ReadOnlySharedMemoryMapping& operator=( + ReadOnlySharedMemoryMapping&&) noexcept; + + // Returns the base address of the mapping. This is read-only memory. This is + // page-aligned. This is nullptr for invalid instances. + const void* memory() const { return raw_memory_ptr(); } + + // Returns a pointer to a page-aligned const T if the mapping is valid and + // large enough to contain a T, or nullptr otherwise. + template <typename T> + const T* GetMemoryAs() const { + static_assert(std::is_trivially_copyable<T>::value, + "Copying non-trivially-copyable object across memory spaces " + "is dangerous"); + if (!IsValid()) + return nullptr; + if (sizeof(T) > size()) + return nullptr; + return static_cast<const T*>(raw_memory_ptr()); + } + + // Returns a span of const T. The number of elements is autodeduced from the + // size of the shared memory mapping. The number of elements may be + // autodeduced as zero, i.e. the mapping is invalid or the size of the mapping + // isn't large enough to contain even one T: in that case, an empty span + // will be returned. The first element, if any, is guaranteed to be + // page-aligned. + template <typename T> + span<const T> GetMemoryAsSpan() const { + static_assert(std::is_trivially_copyable<T>::value, + "Copying non-trivially-copyable object across memory spaces " + "is dangerous"); + if (!IsValid()) + return span<const T>(); + size_t count = size() / sizeof(T); + return GetMemoryAsSpan<T>(count); + } + + // Returns a span of const T with |count| elements if the mapping is valid and + // large enough to contain |count| elements, or an empty span otherwise. The + // first element, if any, is guaranteed to be page-aligned. + template <typename T> + span<const T> GetMemoryAsSpan(size_t count) const { + static_assert(std::is_trivially_copyable<T>::value, + "Copying non-trivially-copyable object across memory spaces " + "is dangerous"); + if (!IsValid()) + return span<const T>(); + if (size() / sizeof(T) < count) + return span<const T>(); + return span<const T>(static_cast<const T*>(raw_memory_ptr()), count); + } + + // Returns a BufferIterator of const T. + template <typename T> + BufferIterator<const T> GetMemoryAsBufferIterator() const { + return BufferIterator<const T>(GetMemoryAsSpan<T>()); + } + + private: + friend class ReadOnlySharedMemoryRegion; + ReadOnlySharedMemoryMapping(void* address, + size_t size, + size_t mapped_size, + const UnguessableToken& guid); + + DISALLOW_COPY_AND_ASSIGN(ReadOnlySharedMemoryMapping); +}; + +// Class modeling a writable mapping of a shared memory region into the +// current process' address space. This is created by *SharedMemoryRegion +// instances. +class BASE_EXPORT WritableSharedMemoryMapping : public SharedMemoryMapping { + public: + // Default constructor initializes an invalid instance. + WritableSharedMemoryMapping(); + + // Move operations are allowed. + WritableSharedMemoryMapping(WritableSharedMemoryMapping&&) noexcept; + WritableSharedMemoryMapping& operator=( + WritableSharedMemoryMapping&&) noexcept; + + // Returns the base address of the mapping. This is writable memory. This is + // page-aligned. This is nullptr for invalid instances. + void* memory() const { return raw_memory_ptr(); } + + // Returns a pointer to a page-aligned T if the mapping is valid and large + // enough to contain a T, or nullptr otherwise. + template <typename T> + T* GetMemoryAs() const { + static_assert(std::is_trivially_copyable<T>::value, + "Copying non-trivially-copyable object across memory spaces " + "is dangerous"); + if (!IsValid()) + return nullptr; + if (sizeof(T) > size()) + return nullptr; + return static_cast<T*>(raw_memory_ptr()); + } + + // Returns a span of T. The number of elements is autodeduced from the size of + // the shared memory mapping. The number of elements may be autodeduced as + // zero, i.e. the mapping is invalid or the size of the mapping isn't large + // enough to contain even one T: in that case, an empty span will be returned. + // The first element, if any, is guaranteed to be page-aligned. + template <typename T> + span<T> GetMemoryAsSpan() const { + static_assert(std::is_trivially_copyable<T>::value, + "Copying non-trivially-copyable object across memory spaces " + "is dangerous"); + if (!IsValid()) + return span<T>(); + size_t count = size() / sizeof(T); + return GetMemoryAsSpan<T>(count); + } + + // Returns a span of T with |count| elements if the mapping is valid and large + // enough to contain |count| elements, or an empty span otherwise. The first + // element, if any, is guaranteed to be page-aligned. + template <typename T> + span<T> GetMemoryAsSpan(size_t count) const { + static_assert(std::is_trivially_copyable<T>::value, + "Copying non-trivially-copyable object across memory spaces " + "is dangerous"); + if (!IsValid()) + return span<T>(); + if (size() / sizeof(T) < count) + return span<T>(); + return span<T>(static_cast<T*>(raw_memory_ptr()), count); + } + + // Returns a BufferIterator of T. + template <typename T> + BufferIterator<T> GetMemoryAsBufferIterator() { + return BufferIterator<T>(GetMemoryAsSpan<T>()); + } + + private: + friend WritableSharedMemoryMapping MapAtForTesting( + subtle::PlatformSharedMemoryRegion* region, + off_t offset, + size_t size); + friend class ReadOnlySharedMemoryRegion; + friend class WritableSharedMemoryRegion; + friend class UnsafeSharedMemoryRegion; + WritableSharedMemoryMapping(void* address, + size_t size, + size_t mapped_size, + const UnguessableToken& guid); + + DISALLOW_COPY_AND_ASSIGN(WritableSharedMemoryMapping); +}; + +} // namespace base + +#endif // BASE_MEMORY_SHARED_MEMORY_MAPPING_H_ |