RtlSetVolatileMemory 函式 （wdm.h）

The RtlSetVolatileMemory function provides RtlFillMemory behavior (for example, setting the contents of a buffer) in situations where the developer needs to be sure that the setting operation occurs (for example, isn't subject to compiler optimizations). 函式會傳回已填滿記憶體的指標。

Syntax

volatile void * RtlSetVolatileMemory(
  [out] volatile void *Destination,
  [in]  int           Fill,
  [in]  size_t        Length
);

Parameters

[out] Destination

要填滿之內存區塊起始位址的指標。

[in] Fill

要填滿記憶體區塊的位元組值。

[in] Length

要填入的記憶體區塊大小，以位元組為單位。 This value must be less than the size of the Destination buffer.

Return value

Returns a pointer to the filled memory block (Destination).

Remarks

• 函式無法辨識為編譯程式內部函數，因此編譯程式永遠不會優化呼叫（完全或以對等的指令序列取代呼叫）。 This differs from RtlFillMemory which is subject to various compiler optimizations.

• 當呼叫傳回時，已以所需的值覆寫緩衝區。 This function's memory accesses to the Destination will only be performed within the function (for example, the compiler can't move memory accesses out of this function).

• 如果平台允許，函式可能會執行未對齊的記憶體存取。

• 函式可能會在其作業中多次存取記憶體位置。

此函式適用於所有版本的 Windows，而不只是最新版本。 您必須取用最新的 WDK，才能從 wdm.h 標頭取得函式宣告。 您也需要最新的 WDK 連結庫 （volatileaccessk.lib）。 不過，產生的驅動程式將會在舊版 Windows 上正常執行。

Example

UCHAR SensitiveData[100];

// Imagine we temporarily store some sensitive cryptographic
// material in a buffer.

StoreCryptographicKey(&SensitiveData);

DoCryptographicOperation(&SensitiveData);

// Now that we are done using the sensitive data we want to
// erase it from the stack. We can use RtlSetVolatileMemory
// to fill the buffer and get a pointer to the filled memory.
// This call will not be optimized away by the compiler.

volatile VOID* clearedBuffer = RtlSetVolatileMemory(&SensitiveData, 0, sizeof(SensitiveData));

Requirements

See also

RtlFillMemory

RtlFillVolatileMemory