ZeroModeMemory - NtDoc
Native API online documentation, based on the System Informer
(formerly Process Hacker) phnt
headers
// usermode_accessors.h
VOID ZeroModeMemory(
VOID *Destination,
SIZE_T Length,
KPROCESSOR_MODE Mode
);
View the official Windows Driver Kit DDI referenceNo description available.
The ZeroModeMemory function fills a memory region with zeros, based on the specified processor mode.
Destination[out] A pointer to the starting address of the memory block to zero.
Length[in] The number of bytes to zero.
Mode[in] The processor mode that determines how the memory access is performed. Mode can be one of the following values.
| Value | Meaning |
|---|---|
| KernelMode | Destination points to kernel-mode memory. The function performs a direct memory zero operation with memory_order_relaxed semantics. |
| UserMode | Destination points to user-mode memory. The function raises an exception if Destination doesn't point to user-mode memory; otherwise it performs a zero operation at the specified address with memory_order_relaxed semantics. |
This function provides a safe way to zero a memory region, with the zero mechanism determined by the specified processor mode. This allows for flexible memory operations that can adapt to different execution contexts while initializing memory blocks to zero.
When Mode is KernelMode:
The function performs a volatile zero operation 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 zeros. 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 zero operation.
The function raises a structured exception if the zero operation fails, such as when the destination address is not valid for the specified mode 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.