Is there a Windows kernel function to unwind the stack?

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Yes, Windows provides a kernel function called RtlVirtualUnwind to unwind the stack. The RtlVirtualUnwind function is part of the Windows Native API (NTAPI) and is used to unwind the call stack during exception handling and stack walking.

The RtlVirtualUnwind function is typically used in kernel-mode drivers or other low-level components that require stack unwinding. It takes the following parameters:

cpp
NTSTATUS RtlVirtualUnwind(

    IN ULONG HandlerType,

    IN ULONG64 ImageBase,

    IN ULONG64 ControlPc,

    IN PRUNTIME_FUNCTION FunctionEntry,

    IN OUT PCONTEXT ContextRecord,

    OUT PVOID *HandlerData,

    OUT PULONG64 EstablisherFrame,

    IN OUT PKNONVOLATILE_CONTEXT_POINTERS ContextPointers

);

Here's a brief description of the parameters:

  • HandlerType: Specifies the type of the exception handler (such as EXCEPTION_UNWINDING, EXCEPTION_EXIT_UNWIND, etc.).

  • ImageBase: Base address of the module that contains the function being unwound.

  • ControlPc: Program counter (PC) value within the function being unwound.

  • FunctionEntry: Pointer to the RUNTIME_FUNCTION structure of the function being unwound.

  • ContextRecord: Pointer to a CONTEXT structure that holds the processor context.

  • HandlerData: Receives the pointer to the language-specific exception handler data.

  • EstablisherFrame: Receives the address of the establisher frame.

  • ContextPointers: Optional pointer to a KNONVOLATILE_CONTEXT_POINTERS structure that receives information about nonvolatile registers.

Note that using RtlVirtualUnwind requires a good understanding of the Windows kernel and exception handling mechanisms. It is typically used in advanced scenarios such as writing custom exception handlers or stack unwinding routines in kernel-mode drivers. For most application-level development, the unwinding of the call stack is handled by the operating system or the compiler during exception handling.

If you're working with user-mode applications in C++ and want to unwind the stack during exception handling, you can use the StackWalk64 function provided by the Debug Help Library (dbghelp.dll). This library offers a higher-level interface to perform stack walking and stack unwinding in user-mode applications.