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/* $Id: except-seh-vcc.cpp $ */
/** @file
* IPRT - Visual C++ Compiler - SEH exception handler (__try/__except/__finally).
*/
/*
* 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
/**
* Calls an exception filter w/o doing any control guard checks.
*
* Doing this within an inline function to prevent disabling CFG for any other
* calls that __C_specific_handler might be doing.
*
* Presumably, the presumption here is that since the target address here is
* taken from tables assumed to be readonly and generated by the compiler, there
* is no need to do any CFG checks. Besides, the target isn't a function that
* is safe to be called out of context and thus doesn't belong in the CFG tables
* in any way.
*/
__declspec(guard(ignore))
DECLINLINE(LONG) CallFilterFunction(PEXCEPTION_FILTER pfnFilter, PEXCEPTION_POINTERS pXcptPtrs,
PEXCEPTION_REGISTRATION_RECORD pXcptRegRec)
{
return pfnFilter(pXcptPtrs, pXcptRegRec);
}
/**
* Calls an exception finally block w/o doing any control guard checks.
*
* See CallFilterFunction for details.
*/
__declspec(guard(ignore))
DECLINLINE(void) CallFinallyFunction(PTERMINATION_HANDLER const pfnTermHandler, BOOLEAN fAbend,
PEXCEPTION_REGISTRATION_RECORD pXcptRegRec)
{
pfnTermHandler(fAbend, pXcptRegRec);
}
/**
* Call exception filters, handlers and unwind code.
*
* This is called for windows' structured exception handling (SEH), i.e. the
* __try/__except/__finally stuff in Visual C++. The compiler generate scope
* records for the __try/__except blocks as well as unwind records for __finally
* and probably C++ stack object destructors.
*
* @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.
*/
EXCEPTION_DISPOSITION __C_specific_handler(PEXCEPTION_RECORD pXcptRec, PEXCEPTION_REGISTRATION_RECORD pXcptRegRec,
PCONTEXT pCpuCtx, PDISPATCHER_CONTEXT pDispCtx)
{
/*
* This function works the scope table, starting at ScopeIndex
* from the dispatcher context.
*/
SCOPE_TABLE const * const pScopeTab = (SCOPE_TABLE const *)pDispCtx->HandlerData;
uint32_t const cScopes = pScopeTab->Count;
uint32_t idxScope = pDispCtx->ScopeIndex;
/*
* The table addresses are RVAs, so convert the program counter (PC) to an RVA.
*/
uint32_t const uRvaPc = pDispCtx->ControlPc - pDispCtx->ImageBase;
/*
* Before we get any further, there are two types of scope records:
* 1. Unwind (aka termination) handler (JumpTarget == 0).
* 2. Exception filter & handler (JumpTarget != 0).
*/
if (IS_DISPATCHING(pXcptRec->ExceptionFlags))
{
/*
* Call exception filter functions when dispatching.
*/
for (; idxScope < cScopes; idxScope++)
{
/* Skip unwind entries (exception handler set to zero). */
uint32_t const uXcptHandler = pScopeTab->ScopeRecord[idxScope].JumpTarget;
if (uXcptHandler != 0)
{
uint32_t const uBegin = pScopeTab->ScopeRecord[idxScope].BeginAddress;
uint32_t const uEnd = pScopeTab->ScopeRecord[idxScope].EndAddress;
uint32_t const cbScope = uEnd - uBegin;
if ( uRvaPc - uBegin < cbScope
&& uBegin < uEnd /* paranoia */)
{
/* The special HandlerAddress value 1 translates to a
EXCEPTION_EXECUTE_HANDLER filter return value. */
LONG lRet = EXCEPTION_EXECUTE_HANDLER;
uint32_t const uFltTermHandler = pScopeTab->ScopeRecord[idxScope].HandlerAddress;
if (uFltTermHandler != 1)
{
PEXCEPTION_FILTER const pfnFilter = (PEXCEPTION_FILTER)(pDispCtx->ImageBase + uFltTermHandler);
EXCEPTION_POINTERS XcptPtrs = { pXcptRec, pCpuCtx };
lRet = CallFilterFunction(pfnFilter, &XcptPtrs, pXcptRegRec);
AssertCompile(EXCEPTION_CONTINUE_SEARCH == 0);
if (lRet == EXCEPTION_CONTINUE_SEARCH)
continue;
}
/* Return if we're supposed to continue execution (the convention
it to match negative values rather than the exact defined value): */
AssertCompile(EXCEPTION_CONTINUE_EXECUTION == -1);
AssertCompile(EXCEPTION_EXECUTE_HANDLER == 1);
if (lRet <= EXCEPTION_CONTINUE_EXECUTION)
return ExceptionContinueExecution;
/* Execute the handler (lRet >= EXCEPTION_EXECUTE_HANDLER). */
uintptr_t const uPtrXcptHandler = uXcptHandler + pDispCtx->ImageBase;
/** @todo shouldn't we do a guard check on this call? */
/// @todo _NLG_Notify(uPtrXcptHandler, pXcptRegRec, 1); - debugger notification.
RtlUnwindEx(pXcptRegRec, (void *)uPtrXcptHandler, pXcptRec,
(PVOID)(uintptr_t)pXcptRec->ExceptionCode, pCpuCtx, pDispCtx->HistoryTable);
/// @todo _NLG_Return2(); - debugger notification.
}
}
}
}
else
{
/*
* Do unwinding.
*/
/* Convert the target unwind address to an RVA up front for efficiency.
(I think target unwinding is what the RtlUnwindEx call above does.) */
uint32_t const uTargetPc = pXcptRec->ExceptionFlags & EXCEPTION_TARGET_UNWIND
? pDispCtx->TargetIp - pDispCtx->ImageBase
: UINT32_MAX;
//RTAssertMsg2("__C_specific_handler: unwind: idxScope=%#x cScopes=%#x uTargetPc=%#x fXcpt=%#x\n", idxScope, cScopes, uTargetPc, pXcptRec->ExceptionFlags);
for (; idxScope < cScopes; idxScope++)
{
uint32_t const uBegin = pScopeTab->ScopeRecord[idxScope].BeginAddress;
uint32_t const uEnd = pScopeTab->ScopeRecord[idxScope].EndAddress;
uint32_t const cbScope = uEnd - uBegin;
if ( uRvaPc - uBegin < cbScope
&& uBegin < uEnd /* paranoia */)
{
uint32_t const uFltTermHandler = pScopeTab->ScopeRecord[idxScope].HandlerAddress;
uint32_t const uXcptHandler = pScopeTab->ScopeRecord[idxScope].JumpTarget;
/* Target unwind requires us to stop if the target PC is in the same
scope as the control PC. Happens for goto out of inner __try scope
or when longjmp'ing into a __try scope. */
if (pXcptRec->ExceptionFlags & EXCEPTION_TARGET_UNWIND)
{
/* The scope same-ness is identified by the same handler and jump target rva values. */
for (uint32_t idxTgtScope = 0; idxTgtScope < cScopes; idxTgtScope++)
if ( pScopeTab->ScopeRecord[idxTgtScope].JumpTarget == uXcptHandler
&& pScopeTab->ScopeRecord[idxTgtScope].HandlerAddress == uFltTermHandler)
{
uint32_t const uTgtBegin = pScopeTab->ScopeRecord[idxTgtScope].BeginAddress;
uint32_t const uTgtEnd = pScopeTab->ScopeRecord[idxTgtScope].EndAddress;
uint32_t const cbTgtScope = uTgtEnd - uTgtBegin;
if ( uTargetPc - uTgtBegin < cbTgtScope
&& uTgtBegin < uTgtEnd /* paranoia */)
{
//RTAssertMsg2("__C_specific_handler: ExceptionContinueSearch (#1)\n");
return ExceptionContinueSearch;
}
}
}
/* The unwind handlers are what we're here for. */
if (uXcptHandler == 0)
{
PTERMINATION_HANDLER const pfnTermHandler = (PTERMINATION_HANDLER)(pDispCtx->ImageBase + uFltTermHandler);
pDispCtx->ScopeIndex = idxScope + 1;
//RTAssertMsg2("__C_specific_handler: Calling __finally %p (idxScope=%#x)\n", pfnTermHandler, idxScope);
CallFinallyFunction(pfnTermHandler, TRUE /*fAbend*/, pXcptRegRec);
}
/* Exception filter & handler entries are skipped, unless the exception
handler is being targeted by the unwind, in which case we're done
unwinding and the caller should transfer control there. */
else if ( uXcptHandler == uTargetPc
&& (pXcptRec->ExceptionFlags & EXCEPTION_TARGET_UNWIND))
{
//RTAssertMsg2("__C_specific_handler: ExceptionContinueSearch (#2)\n");
return ExceptionContinueSearch;
}
}
}
}
return ExceptionContinueSearch;
}
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