DetourSetSystemRegionUpperBound

DetourSetSystemRegionUpperBound

Set the lower bound of the region of memory that cannot be used for trampolines because it is reserved for system DLLs.

Definition

PVOID DetourSetSystemRegionUpperBound(
    _In_ PVOID pSystemRegionUpperBound
);

Return value

Returns the previous upper bound value.

Parameters

pSystemRegionUpperBound : Specifies the upper bound of the system region into which Detours must avoid placing trampolines.

Remarks

The DetourAttach and DetourAttachEx APIs allocate a trampoline for each detoured function. To avoid fragmenting memory, Detours attempts to create the region from which it allocates trampoline as close as possible to the code being detoured. In some circumstances, trampoline region can collides with memory that is silently set aside by the OS or the application for DLLs that are loaded later. When this happens, the application continues to behave correctly, but the OS can be forced to relocate one or more DLLs to another location, which increase the virtual memory required for the process.

To avoid these DLL-relocation collisions, Detours is programmed to avoid placing any trampolines in region of memory called the "system region". By default, this region is from 0x70000000 to 0x80000000. Call DetourSetSystemRegionLowerBound and DetourSetSystemRegionUpperBound and to change the region. For example, one might increase the region if the CLR is loaded into a process after system DLLs are detoured.

For more information on using Detours to intercept function calls, see Interception of Binary Functions or Using Detours in the Detours Overview.

Related Samples

Region.