ReadUCharFromUser function (usermode_accessors.h)

The ReadUCharFromUser function safely reads a UCHAR value from user-mode memory.

Syntax

UCHAR ReadUCharFromUser(
  const volatile UCHAR *Source
);

Parameters

Source

[in] A pointer to the user-mode memory ___location from which to read the UCHAR value.

Return value

ReadUCharFromUser returns the UCHAR value read from the specified user-mode memory address.

Remarks

This function provides a safe way to read a UCHAR value from user-mode memory. It ensures the provided address is a user-mode address before reading it.

This function doesn't enforce alignment.

It raises a structured exception if the memory access fails, such as when the source address isn't a 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). The memory access is performed with memory_order_relaxed semantics.

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.

Requirements

See also

ReadUCharFromMode

WriteUCharToUser