except.c File Reference

#include <rtl.h>
#include <debug.h>

Include dependency graph for except.c:

Go to the source code of this file.

Macros
#define	NDEBUG

Functions
PVOID NTAPI	RtlpGetExceptionAddress (VOID)
BOOLEAN NTAPI	RtlpUnwindInternal (_In_opt_ PVOID TargetFrame, _In_opt_ PVOID TargetIp, _In_ PEXCEPTION_RECORD ExceptionRecord, _In_ PVOID ReturnValue, _In_ PCONTEXT ContextRecord, _In_opt_ struct _UNWIND_HISTORY_TABLE *HistoryTable, _In_ ULONG Flags)
BOOLEAN NTAPI	RtlDispatchException (_In_ PEXCEPTION_RECORD ExceptionRecord, _In_ PCONTEXT ContextRecord)

Macro Definition Documentation

NDEBUG

#define NDEBUG

Definition at line 11 of file except.c.

Function Documentation

RtlDispatchException()

BOOLEAN NTAPI RtlDispatchException	(	_In_ PEXCEPTION_RECORD	ExceptionRecord,
		_In_ PCONTEXT	ContextRecord
	)

Definition at line 43 of file except.c.

{
    BOOLEAN Handled;
 
    /* Perform vectored exception handling for user mode */
    if (RtlCallVectoredExceptionHandlers(ExceptionRecord, ContextRecord))
    {
        /* Exception handled, now call vectored continue handlers */
        RtlCallVectoredContinueHandlers(ExceptionRecord, ContextRecord);
 
        /* Continue execution */
        return TRUE;
    }
 
    /* Call the internal unwind routine */
    Handled = RtlpUnwindInternal(NULL, // TargetFrame
                                 NULL, // TargetIp
                                 ExceptionRecord,
                                 0, // ReturnValue
                                 ContextRecord,
                                 NULL, // HistoryTable
                                 UNW_FLAG_EHANDLER);
 
    /* In user mode, call any registered vectored continue handlers */
    RtlCallVectoredContinueHandlers(ExceptionRecord, ContextRecord);
 
    return Handled;
}

RtlpGetExceptionAddress()

PVOID NTAPI RtlpGetExceptionAddress

(

VOID

)

Definition at line 21 of file except.c.

{
    UNIMPLEMENTED;
    return NULL;
}

RtlpUnwindInternal()

BOOLEAN NTAPI RtlpUnwindInternal	(	_In_opt_ PVOID	TargetFrame,
		_In_opt_ PVOID	TargetIp,
		_In_ PEXCEPTION_RECORD	ExceptionRecord,
		_In_ PVOID	ReturnValue,
		_In_ PCONTEXT	ContextRecord,
		_In_opt_ struct _UNWIND_HISTORY_TABLE *	HistoryTable,
		_In_ ULONG	HandlerType
	)

Remarks

The implementation is based on the description in this blog: http://www.nynaeve.net/?p=106

Differences to the desciption:
- Instead of using 2 pointers to the unwind context and previous context,
  that are being swapped and the context copied, the unwind context is
  kept in the local context and copied back into the context passed in
  by the caller.

See also

http://www.nynaeve.net/?p=106

TODO: Handle DPC stack

TODO

TODO: Check for DPC stack

Definition at line 717 of file unwind.c.

{
    DISPATCHER_CONTEXT DispatcherContext;
    PEXCEPTION_ROUTINE ExceptionRoutine;
    EXCEPTION_DISPOSITION Disposition;
    PRUNTIME_FUNCTION FunctionEntry;
    ULONG_PTR StackLow, StackHigh;
    ULONG64 ImageBase, EstablisherFrame;
    CONTEXT UnwindContext;
 
    /* Get the current stack limits */
    RtlpGetStackLimits(&StackLow, &StackHigh);
 
    /* If we have a target frame, then this is our high limit */
    if (TargetFrame != NULL)
    {
        StackHigh = (ULONG64)TargetFrame + 1;
    }
 
    /* Copy the context */
    UnwindContext = *ContextRecord;
 
    /* Set up the constant fields of the dispatcher context */
    DispatcherContext.ContextRecord =
        (HandlerType == UNW_FLAG_UHANDLER) ? ContextRecord : &UnwindContext;
    DispatcherContext.HistoryTable = HistoryTable;
    DispatcherContext.TargetIp = (ULONG64)TargetIp;
 
    /* Start looping */
    while (TRUE)
    {
        if (!RtlpIsStackPointerValid(UnwindContext.Rsp, StackLow, StackHigh))
        {
            return FALSE;
        }
 
        /* Lookup the FunctionEntry for the current RIP */
        FunctionEntry = RtlLookupFunctionEntry(UnwindContext.Rip, &ImageBase, NULL);
        if (FunctionEntry == NULL)
        {
            /* No function entry, so this must be a leaf function. Pop the return address from the stack.
               Note: this can happen after the first frame as the result of an exception */
            UnwindContext.Rip = *(DWORD64*)UnwindContext.Rsp;
            UnwindContext.Rsp += sizeof(DWORD64);
 
            if (HandlerType == UNW_FLAG_UHANDLER)
            {
                /* Copy the context back for the next iteration */
                *ContextRecord = UnwindContext;
            }
            continue;
        }
 
        /* Save Rip before the virtual unwind */
        DispatcherContext.ControlPc = UnwindContext.Rip;
 
        /* Do a virtual unwind to get the next frame */
        ExceptionRoutine = RtlVirtualUnwind(HandlerType,
                                            ImageBase,
                                            UnwindContext.Rip,
                                            FunctionEntry,
                                            &UnwindContext,
                                            &DispatcherContext.HandlerData,
                                            &EstablisherFrame,
                                            NULL);
 
        /* Check, if we are still within the stack boundaries */
        if ((EstablisherFrame < StackLow) ||
            (EstablisherFrame >= StackHigh) ||
            (EstablisherFrame & 7))
        {
 
            /* If we are handling an exception, we are done here. */
            if (HandlerType == UNW_FLAG_EHANDLER)
            {
                ExceptionRecord->ExceptionFlags |= EXCEPTION_STACK_INVALID;
                return FALSE;
            }
 
            __debugbreak();
            RtlRaiseStatus(STATUS_BAD_STACK);
        }
 
        /* Check if we have an exception routine */
        if (ExceptionRoutine != NULL)
        {
            /* Check if this is the target frame */
            if (EstablisherFrame == (ULONG64)TargetFrame)
            {
                /* Set flag to inform the language handler */
                ExceptionRecord->ExceptionFlags |= EXCEPTION_TARGET_UNWIND;
            }
 
            /* Log the exception if it's enabled */
            RtlpCheckLogException(ExceptionRecord,
                                  &UnwindContext,
                                  &DispatcherContext,
                                  sizeof(DispatcherContext));
 
            /* Set up the variable fields of the dispatcher context */
            DispatcherContext.ImageBase = ImageBase;
            DispatcherContext.FunctionEntry = FunctionEntry;
            DispatcherContext.LanguageHandler = ExceptionRoutine;
            DispatcherContext.EstablisherFrame = EstablisherFrame;
            DispatcherContext.ScopeIndex = 0;
 
            /* Store the return value in the unwind context */
            UnwindContext.Rax = (ULONG64)ReturnValue;
 
             /* Loop all nested handlers */
            do
            {
                /* Call the language specific handler */
                Disposition = RtlpExecuteHandlerForUnwind(ExceptionRecord,
                                                          (PVOID)EstablisherFrame,
                                                          ContextRecord,
                                                          &DispatcherContext);
 
                /* Clear exception flags for the next iteration */
                ExceptionRecord->ExceptionFlags &= ~(EXCEPTION_TARGET_UNWIND |
                                                     EXCEPTION_COLLIDED_UNWIND);
 
                /* Check if we do exception handling */
                if (HandlerType == UNW_FLAG_EHANDLER)
                {
                    if (Disposition == ExceptionContinueExecution)
                    {
                        /* Check if it was non-continuable */
                        if (ExceptionRecord->ExceptionFlags & EXCEPTION_NONCONTINUABLE)
                        {
                            __debugbreak();
                            RtlRaiseStatus(EXCEPTION_NONCONTINUABLE_EXCEPTION);
                        }
 
                        /* Execution continues */
                        return TRUE;
                    }
                    else if (Disposition == ExceptionNestedException)
                    {
                        __debugbreak();
                    }
                }
 
                if (Disposition == ExceptionCollidedUnwind)
                {
                    /* We collided with another unwind, so we need to continue
                       "after" the handler, skipping the termination handler
                       that resulted in this unwind. The installed handler has
                       already copied the original dispatcher context, we now
                       need to copy back the original context. */
                    UnwindContext = *ContextRecord = *DispatcherContext.ContextRecord;
 
                    /* The original context was from "before" the unwind, so we
                       need to do an additional virtual unwind to restore the
                       unwind contxt. */
                    RtlVirtualUnwind(HandlerType,
                                     DispatcherContext.ImageBase,
                                     UnwindContext.Rip,
                                     DispatcherContext.FunctionEntry,
                                     &UnwindContext,
                                     &DispatcherContext.HandlerData,
                                     &EstablisherFrame,
                                     NULL);
 
                    /* Restore the context pointer and establisher frame. */
                    DispatcherContext.ContextRecord = &UnwindContext;
                    EstablisherFrame = DispatcherContext.EstablisherFrame;
 
                    /* Set the exception flags to indicate that we collided
                       with an unwind and continue the handler loop, which
                       will run any additional handlers from the previous
                       unwind. */
                    ExceptionRecord->ExceptionFlags |= EXCEPTION_COLLIDED_UNWIND;
                    continue;
                }
 
                /* This must be ExceptionContinueSearch now */
                else if (Disposition != ExceptionContinueSearch)
                {
                    __debugbreak();
                    RtlRaiseStatus(STATUS_INVALID_DISPOSITION);
                }
            } while (ExceptionRecord->ExceptionFlags & EXCEPTION_COLLIDED_UNWIND);
        }
 
        /* Check, if we have left our stack (8.) */
        if ((EstablisherFrame < StackLow) ||
            (EstablisherFrame > StackHigh) ||
            (EstablisherFrame & 7))
        {
            __debugbreak();
 
            if (UnwindContext.Rip == ContextRecord->Rip)
            {
                RtlRaiseStatus(STATUS_BAD_FUNCTION_TABLE);
            }
            else
            {
                ZwRaiseException(ExceptionRecord, ContextRecord, FALSE);
            }
        }
 
        if (EstablisherFrame == (ULONG64)TargetFrame)
        {
            break;
        }
 
        if (HandlerType == UNW_FLAG_UHANDLER)
        {
            /* We have successfully unwound a frame. Copy the unwind context back. */
            *ContextRecord = UnwindContext;
        }
    }
 
    if (ExceptionRecord->ExceptionCode != STATUS_UNWIND_CONSOLIDATE)
    {
        ContextRecord->Rip = (ULONG64)TargetIp;
    }
 
    /* Set the return value */
    ContextRecord->Rax = (ULONG64)ReturnValue;
 
    /* Restore the context */
    RtlRestoreContext(ContextRecord, ExceptionRecord);
 
    /* Should never get here! */
    ASSERT(FALSE);
    return FALSE;
}

Referenced by RtlDispatchException(), and RtlUnwindEx().