SetUserMemory - NtDoc
Native API online documentation, based on the System Informer
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headers
// usermode_accessors.h
VOID SetUserMemory(
volatile VOID *Destination,
UCHAR Fill,
SIZE_T Length
);
View the official Windows Driver Kit DDI referenceNo description available.
The SetUserMemory function fills a user-mode memory region with a specified byte value.
Destination[out] A pointer to the starting address of the memory block to fill.
Fill[in] The byte value used to fill the first Length bytes of Destination.
Length[in] The number of bytes to fill with the Fill value.
This function provides a safe way to fill a user-mode memory region with a specified byte value. This allows for flexible memory operations when kernel-mode code needs to initialize user-mode memory buffers.
The function has the following properties:
The function performs a volatile fill using memory_order_relaxed semantics.
The function isn't recognized as a compiler intrinsic so the compiler will never optimize away the call (either entirely or replace the call with an equivalent sequence of instructions).
When the call returns, the buffer has been overwritten with the specified Fill value. 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).
The function might perform unaligned memory accesses if the platform allows for it.
The function might access memory locations more than once as part of its fill operation.
The function raises a structured exception if the fill operation fails, such as when the destination address is not a valid user-mode address or is inaccessible.
This function will never be optimized away by the compiler, nor will the compiler create additional accesses to this memory location before the function is called or after the function returns (unless the source code explicitly performs these accesses).
This function works on all versions of Windows, not just the latest. You need to consume the latest WDK to get the function declaration from the usermode_accessors.h header. You also need the library (umaccess.lib) from the latest WDK. However, the resulting driver will run fine on older versions of Windows.