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/* $Id: stack-except-vcc.cpp $ */
/** @file
* IPRT - Visual C++ Compiler - Stack Checking, __GSHandlerCheck.
*/
/*
* Copyright (C) 2022-2023 Oracle and/or its affiliates.
*
* This file is part of VirtualBox base platform packages, as
* available from https://www.virtualbox.org.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation, in version 3 of the
* License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses>.
*
* The contents of this file may alternatively be used under the terms
* of the Common Development and Distribution License Version 1.0
* (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
* in the VirtualBox distribution, in which case the provisions of the
* CDDL are applicable instead of those of the GPL.
*
* You may elect to license modified versions of this file under the
* terms and conditions of either the GPL or the CDDL or both.
*
* SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
*/
/*********************************************************************************************************************************
* Header Files *
*********************************************************************************************************************************/
#include "internal/nocrt.h"
#include "except-vcc.h"
#if !defined(RT_ARCH_AMD64)
# error "This file is for AMD64 (and probably ARM, but needs porting)"
#endif
/**
* Check the stack cookie before calling the exception handler.
*
* This is to prevent attackers from bypassing stack cookie checking by
* triggering an exception.
*
* This does not call any C++ exception handlers, as it's probably (still
* figuring this stuff out) only used when C++ exceptions are disabled.
*
* @returns Exception disposition.
* @param pXcptRec The exception record.
* @param pXcptRegRec The exception registration record, taken to be the frame
* address.
* @param pCpuCtx The CPU context for the exception.
* @param pDispCtx Dispatcher context.
*/
extern "C" __declspec(guard(suppress))
EXCEPTION_DISPOSITION __GSHandlerCheck(PEXCEPTION_RECORD pXcptRec, PEXCEPTION_REGISTRATION_RECORD pXcptRegRec,
PCONTEXT pCpuCtx, PDISPATCHER_CONTEXT pDispCtx)
{
RT_NOREF(pXcptRec, pCpuCtx);
/*
* Only GS handler data here.
*/
PCGS_HANDLER_DATA pHandlerData = (PCGS_HANDLER_DATA)pDispCtx->HandlerData;
/*
* Locate the stack cookie and call the regular stack cookie checker routine.
* (Same code as in __GSHandlerCheck_SEH, fixes applies both places.)
*/
/* Calculate the cookie address and read it. */
uintptr_t uPtrFrame = (uintptr_t)pXcptRegRec;
uint32_t offCookie = pHandlerData->u.offCookie;
if (offCookie & GS_HANDLER_OFF_COOKIE_HAS_ALIGNMENT)
{
uPtrFrame += pHandlerData->offAlignedBase;
uPtrFrame &= ~(uintptr_t)pHandlerData->uAlignmentMask;
}
uintptr_t uCookie = *(uintptr_t const *)(uPtrFrame + (int32_t)(offCookie & GS_HANDLER_OFF_COOKIE_MASK));
/* The stored cookie is xor'ed with the frame / registration record address
or with the frame pointer register if one is being used. In the latter
case, we have to add the frame offset to get the correct address. */
uintptr_t uXorAddr = (uintptr_t)pXcptRegRec;
PCIMAGE_UNWIND_INFO pUnwindInfo = (PCIMAGE_UNWIND_INFO)(pDispCtx->ImageBase + pDispCtx->FunctionEntry->UnwindInfoAddress);
if (pUnwindInfo->FrameRegister != 0)
uXorAddr += pUnwindInfo->FrameOffset << 4;
/* This call will not return on failure. */
__security_check_cookie(uCookie ^ uXorAddr);
return ExceptionContinueSearch;
}
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