ReadLongFromMode - NtDoc
Native API online documentation, based on the System Informer
(formerly Process Hacker) phnt
headers
// usermode_accessors.h
LONG ReadLongFromMode(
const LONG *Source,
KPROCESSOR_MODE Mode
);
View the official Windows Driver Kit DDI referenceNo description available.
The ReadLongFromMode function safely reads a LONG value from memory based on the specified processor mode.
Source[in] A pointer to the memory location from which to read the LONG value.
Mode[in] The processor mode that determines how the memory access is performed. Mode can be one of the following values.
| Value | Meaning |
|---|---|
| KernelMode | Source points to kernel-mode memory. The function performs a read from the specified address with memory_order_relaxed semantics. See Remarks for more details. |
| UserMode | Source points to user-mode memory. The function raises an exception if Source doesn't point to user-mode memory; otherwise it performs a read from the specified address with memory_order_relaxed semantics. See Remarks for more details. |
ReadLongFromMode returns the LONG value read from the specified memory address.
This function provides a safe way to read a LONG value from memory, with extra safety checks when accessing user-mode memory. It ensures that the provided address is valid and accessible based on the specified processor mode.
This function doesn't enforce alignment.
It raises a structured exception if the memory access fails, such as when the source address isn't valid or is inaccessible for the specified processor mode.
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.