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https://github.com/RGBCube/serenity
synced 2025-07-27 04:17:35 +00:00
UserspaceEmulator: Make it possible to wrap PODs in ValueWithShadow
Instead of making it hold the shadow data as another `T`, make it hold the data as a byte array, and allow it to read the byte array as `T`. This makes it much easier to make a "read_typed" function in the MMU.
This commit is contained in:
Ali Mohammad Pur
Andreas Kling
parent
e08cf8f554
commit
f6e82a8e0a
7 changed files with 115 additions and 101 deletions
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@ -13,10 +13,6 @@
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namespace UserspaceEmulator {
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constexpr u64 _initialized_64 = 0x01010101'01010101LLU;
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constexpr u128 _initialized_128 = u128(_initialized_64, _initialized_64);
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constexpr u256 _initialized_256 = u256(_initialized_128, _initialized_128);
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template<typename T>
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class ValueAndShadowReference;
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@ -24,114 +20,134 @@ template<typename T>
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class ValueWithShadow {
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public:
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using ValueType = T;
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using ShadowType = Array<u8, sizeof(T)>;
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ValueWithShadow() = default;
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ValueWithShadow(T value, T shadow)
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: m_value(value)
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{
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ReadonlyBytes { &shadow, sizeof(shadow) }.copy_to(m_shadow);
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}
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ValueWithShadow(T value, ShadowType shadow)
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: m_value(value)
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, m_shadow(shadow)
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{
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}
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ValueWithShadow(const ValueAndShadowReference<T>&);
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static ValueWithShadow create_initialized(T value)
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{
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ShadowType shadow;
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shadow.fill(0x01);
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return {
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value,
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shadow,
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};
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}
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ValueWithShadow(ValueAndShadowReference<T> const&);
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T value() const { return m_value; }
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T shadow() const { return m_shadow; }
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ShadowType const& shadow() const { return m_shadow; }
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T shadow_as_value() const requires(IsTriviallyConstructible<T>)
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{
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return *bit_cast<T const*>(m_shadow.data());
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}
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template<auto member>
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auto reference_to() requires(IsClass<T> || IsUnion<T>)
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{
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using ResultType = ValueAndShadowReference<RemoveReference<decltype(declval<T>().*member)>>;
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return ResultType {
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m_value.*member,
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*bit_cast<typename ResultType::ShadowType*>(m_shadow.span().offset_pointer(bit_cast<u8*>(member) - bit_cast<u8*>(nullptr))),
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};
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}
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template<auto member>
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auto slice() const requires(IsClass<T> || IsUnion<T>)
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{
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using ResultType = ValueWithShadow<RemoveReference<decltype(declval<T>().*member)>>;
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return ResultType {
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m_value.*member,
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*bit_cast<typename ResultType::ShadowType*>(m_shadow.span().offset_pointer(bit_cast<u8*>(member) - bit_cast<u8*>(nullptr))),
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};
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}
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bool is_uninitialized() const
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{
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if constexpr (sizeof(T) == 32)
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return (m_shadow & _initialized_256) != _initialized_256;
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if constexpr (sizeof(T) == 16)
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return (m_shadow & _initialized_128) != _initialized_128;
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if constexpr (sizeof(T) == 8)
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return (m_shadow & _initialized_64) != _initialized_64;
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if constexpr (sizeof(T) == 4)
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return (m_shadow & 0x01010101) != 0x01010101;
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if constexpr (sizeof(T) == 2)
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return (m_shadow & 0x0101) != 0x0101;
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if constexpr (sizeof(T) == 1)
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return (m_shadow & 0x01) != 0x01;
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for (size_t i = 0; i < sizeof(ShadowType); ++i) {
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if ((m_shadow[i] & 0x01) != 0x01)
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return true;
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}
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return false;
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}
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void set_initialized()
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{
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if constexpr (sizeof(T) == 32)
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m_shadow = _initialized_256;
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if constexpr (sizeof(T) == 16)
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m_shadow = _initialized_128;
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if constexpr (sizeof(T) == 8)
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m_shadow = _initialized_64;
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if constexpr (sizeof(T) == 4)
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m_shadow = 0x01010101;
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if constexpr (sizeof(T) == 2)
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m_shadow = 0x0101;
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if constexpr (sizeof(T) == 1)
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m_shadow = 0x01;
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m_shadow.fill(0x01);
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}
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private:
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T m_value;
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T m_shadow;
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T m_value {};
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ShadowType m_shadow {};
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};
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template<typename T>
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class ValueAndShadowReference {
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public:
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using ValueType = T;
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using ShadowType = Array<u8, sizeof(T)>;
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ValueAndShadowReference(T& value, T& shadow)
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ValueAndShadowReference(T& value, ShadowType& shadow)
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: m_value(value)
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, m_shadow(shadow)
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{
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}
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ValueAndShadowReference(T& value, T& shadow)
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: m_value(value)
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, m_shadow(*bit_cast<ShadowType*>(&shadow))
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{
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}
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bool is_uninitialized() const
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{
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if constexpr (sizeof(T) == 32)
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return (m_shadow & _initialized_256) != _initialized_256;
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if constexpr (sizeof(T) == 16)
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return (m_shadow & _initialized_128) != _initialized_128;
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if constexpr (sizeof(T) == 8)
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return (m_shadow & _initialized_64) != _initialized_64;
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if constexpr (sizeof(T) == 4)
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return (m_shadow & 0x01010101) != 0x01010101;
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if constexpr (sizeof(T) == 2)
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return (m_shadow & 0x0101) != 0x0101;
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if constexpr (sizeof(T) == 1)
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return (m_shadow & 0x01) != 0x01;
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for (size_t i = 0; i < sizeof(ShadowType); ++i) {
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if ((m_shadow[i] & 0x01) != 0x01)
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return true;
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}
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return false;
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}
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ValueAndShadowReference<T>& operator=(const ValueWithShadow<T>&);
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T& value() { return m_value; }
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T& shadow() { return m_shadow; }
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T shadow_as_value() const requires(IsTriviallyConstructible<T>)
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{
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return *bit_cast<T const*>(m_shadow.data());
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}
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const T& value() const { return m_value; }
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const T& shadow() const { return m_shadow; }
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T& value() { return m_value; }
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ShadowType& shadow() { return m_shadow; }
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T const& value() const { return m_value; }
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ShadowType const& shadow() const { return m_shadow; }
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private:
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T& m_value;
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T& m_shadow;
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ShadowType& m_shadow;
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};
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template<typename T>
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ALWAYS_INLINE ValueWithShadow<T> shadow_wrap_as_initialized(T value)
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{
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if constexpr (sizeof(T) == 32)
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return { value, _initialized_256 };
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if constexpr (sizeof(T) == 16)
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return { value, _initialized_128 };
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if constexpr (sizeof(T) == 8)
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return { value, _initialized_64 };
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if constexpr (sizeof(T) == 4)
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return { value, 0x01010101 };
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if constexpr (sizeof(T) == 2)
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return { value, 0x0101 };
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if constexpr (sizeof(T) == 1)
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return { value, 0x01 };
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return ValueWithShadow<T>::create_initialized(value);
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}
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template<typename T, typename U>
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ALWAYS_INLINE ValueWithShadow<T> shadow_wrap_with_taint_from(T value, const U& taint_a)
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ALWAYS_INLINE ValueWithShadow<T> shadow_wrap_with_taint_from(T value, U const& taint_a)
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{
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if (taint_a.is_uninitialized())
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return { value, 0 };
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@ -139,7 +155,7 @@ ALWAYS_INLINE ValueWithShadow<T> shadow_wrap_with_taint_from(T value, const U& t
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}
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template<typename T, typename U, typename V>
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ALWAYS_INLINE ValueWithShadow<T> shadow_wrap_with_taint_from(T value, const U& taint_a, const V& taint_b)
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ALWAYS_INLINE ValueWithShadow<T> shadow_wrap_with_taint_from(T value, U const& taint_a, V const& taint_b)
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{
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if (taint_a.is_uninitialized() || taint_b.is_uninitialized())
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return { value, 0 };
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@ -147,7 +163,7 @@ ALWAYS_INLINE ValueWithShadow<T> shadow_wrap_with_taint_from(T value, const U& t
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}
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template<typename T, typename U, typename V, typename X>
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ALWAYS_INLINE ValueWithShadow<T> shadow_wrap_with_taint_from(T value, const U& taint_a, const V& taint_b, const X& taint_c)
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ALWAYS_INLINE ValueWithShadow<T> shadow_wrap_with_taint_from(T value, U const& taint_a, V const& taint_b, X const& taint_c)
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{
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if (taint_a.is_uninitialized() || taint_b.is_uninitialized() || taint_c.is_uninitialized())
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return { value, 0 };
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@ -178,7 +194,3 @@ struct AK::Formatter<UserspaceEmulator::ValueWithShadow<T>> : AK::Formatter<T> {
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return Formatter<T>::format(builder, value.value());
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}
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};
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#undef INITIALIZED_64
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#undef INITIALIZED_128
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#undef INITIALIZED_256
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