ReadStructFromUserAligned macro (usermode_accessors.h)

The ReadStructFromUserAligned macro safely reads a structure from user-mode memory with alignment validation.

Syntax

void ReadStructFromUserAligned(
   Destination,
   Source,
   Alignment
);

Parameters

Destination

[out] A pointer to the structure that receives the data read from user-mode memory.

Source

[in] A pointer to the user-mode memory location from which to read the structure.

Alignment

[in] The required alignment for the source address, in bytes.

Return value

None

Remarks

This macro provides a safe way to read a structure from user-mode memory with alignment enforcement. It ensures the provided address is a user-mode address and meets the specified alignment requirements before reading it.

The macro validates that Source and Destination point to compatible types and automatically determines the structure size for the copy operation.

This macro enforces alignment by verifying that the source address meets the specified alignment requirement. This helps prevent performance penalties and potential hardware faults that can occur when accessing misaligned data structures.

It raises a structured exception if the memory access fails, such as when the source address isn't a user-mode address, is inaccessible, or doesn't meet the alignment requirements.

This macro will never be optimized away by the compiler, nor will the compiler create additional accesses to this memory location before the macro is called or after the macro returns (unless the source code explicitly performs these accesses). The memory access is performed with memory_order_relaxed semantics.

This macro works on all versions of Windows, not just the latest. You need to consume the latest WDK to get the macro 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.

Requirements

See also

ReadStructFromUser

ReadStructFromModeAligned

ReadStructFromUserHelper

WriteStructToUserAligned