ehandler.c

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/*
 * PROJECT:     ReactOS CRT library
 * LICENSE:     MIT (https://spdx.org/licenses/MIT)
 * PURPOSE:     C specific exception/unwind handler for AMD64
 * COPYRIGHT:   Copyright 2018-2021 Timo Kreuzer <timo.kreuzer@reactos.org>
*/
 
#include <precomp.h>
#include <winnt.h>
 
 
_CRTIMP
EXCEPTION_DISPOSITION
__cdecl
__C_specific_handler(
    struct _EXCEPTION_RECORD *ExceptionRecord,
    void *EstablisherFrame,
    struct _CONTEXT *ContextRecord,
    struct _DISPATCHER_CONTEXT *DispatcherContext)
{
    PSCOPE_TABLE ScopeTable;
    ULONG i, BeginAddress, EndAddress, Handler;
    ULONG64 ImageBase, JumpTarget, IpOffset, TargetIpOffset;
    EXCEPTION_POINTERS ExceptionPointers;
    PTERMINATION_HANDLER TerminationHandler;
    PEXCEPTION_FILTER ExceptionFilter;
    LONG FilterResult;
 
    /* Set up the EXCEPTION_POINTERS */
    ExceptionPointers.ExceptionRecord = ExceptionRecord;
    ExceptionPointers.ContextRecord = ContextRecord;
 
    /* Get the image base */
    ImageBase = (ULONG64)DispatcherContext->ImageBase;
 
    /* Get the image base relative instruction pointers */
    IpOffset = DispatcherContext->ControlPc - ImageBase;
    TargetIpOffset = DispatcherContext->TargetIp - ImageBase;
 
    /* Get the scope table and current index */
    ScopeTable = (PSCOPE_TABLE)DispatcherContext->HandlerData;
 
    /* Loop while we have scope table entries */
    while (DispatcherContext->ScopeIndex < ScopeTable->Count)
    {
        /* Use i as index and update the dispatcher context */
        i = DispatcherContext->ScopeIndex++;
 
        /* Get the start and end of the scrope */
        BeginAddress = ScopeTable->ScopeRecord[i].BeginAddress;
        EndAddress = ScopeTable->ScopeRecord[i].EndAddress;
 
        /* Skip this scope if we are not within the bounds */
        if ((IpOffset < BeginAddress) || (IpOffset >= EndAddress))
        {
            continue;
        }
 
        /* Check if this is an unwind */
        if (ExceptionRecord->ExceptionFlags & EXCEPTION_UNWIND)
        {
            /* Check if this is a target unwind */
            if (ExceptionRecord->ExceptionFlags & EXCEPTION_TARGET_UNWIND)
            {
                /* Check if the target is within the scope itself */
                if ((TargetIpOffset >= BeginAddress) &&
                    (TargetIpOffset <  EndAddress))
                {
                    return ExceptionContinueSearch;
                }
            }
 
            /* Check if this is a termination handler / finally function */
            if (ScopeTable->ScopeRecord[i].JumpTarget == 0)
            {
                /* Call the handler */
                Handler = ScopeTable->ScopeRecord[i].HandlerAddress;
                TerminationHandler = (PTERMINATION_HANDLER)(ImageBase + Handler);
                TerminationHandler(TRUE, EstablisherFrame);
            }
            else if (ScopeTable->ScopeRecord[i].JumpTarget == TargetIpOffset)
            {
                return ExceptionContinueSearch;
            }
        }
        else
        {
            /* We are only unterested in exception handlers */
            if (ScopeTable->ScopeRecord[i].JumpTarget == 0)
            {
                continue;
            }
 
            /* This is an exception filter, get the handler address */
            Handler = ScopeTable->ScopeRecord[i].HandlerAddress;
 
            /* Check for hardcoded EXCEPTION_EXECUTE_HANDLER */
            if (Handler == EXCEPTION_EXECUTE_HANDLER)
            {
                /* This is our result */
                FilterResult = EXCEPTION_EXECUTE_HANDLER;
            }
            else
            {
                /* Otherwise we need to call the handler */
                ExceptionFilter = (PEXCEPTION_FILTER)(ImageBase + Handler);
                FilterResult = ExceptionFilter(&ExceptionPointers, EstablisherFrame);
            }
 
            if (FilterResult < 0 /* EXCEPTION_CONTINUE_EXECUTION */)
            {
                return ExceptionContinueExecution;
            }
 
            if (FilterResult > 0 /* EXCEPTION_EXECUTE_HANDLER */)
            {
                JumpTarget = (ImageBase + ScopeTable->ScopeRecord[i].JumpTarget);
 
                /* Unwind to the target address (This does not return) */
                RtlUnwindEx(EstablisherFrame,
                            (PVOID)JumpTarget,
                            ExceptionRecord,
                            UlongToPtr(ExceptionRecord->ExceptionCode),
                            DispatcherContext->ContextRecord,
                            DispatcherContext->HistoryTable);
 
                /* Should not get here */
                __debugbreak();
            }
        }
    }
 
    /* Reached the end of the scope table */
    return ExceptionContinueSearch;
}
 
void __cdecl _local_unwind(void* frame, void* target)
{
    RtlUnwind(frame, target, NULL, 0);
}