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llvm-project/llvm/lib/CodeGen/AsmPrinter/Win64Exception.cpp

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//===-- CodeGen/AsmPrinter/Win64Exception.cpp - Dwarf Exception Impl ------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing Win64 exception info into asm files.
//
//===----------------------------------------------------------------------===//
#include "Win64Exception.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Twine.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/WinEHFuncInfo.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Target/TargetFrameLowering.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
Win64Exception::Win64Exception(AsmPrinter *A)
: EHStreamer(A), shouldEmitPersonality(false), shouldEmitLSDA(false),
shouldEmitMoves(false) {}
Win64Exception::~Win64Exception() {}
/// endModule - Emit all exception information that should come after the
/// content.
void Win64Exception::endModule() {
}
void Win64Exception::beginFunction(const MachineFunction *MF) {
shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
// If any landing pads survive, we need an EH table.
bool hasLandingPads = !MMI->getLandingPads().empty();
shouldEmitMoves = Asm->needsSEHMoves();
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
unsigned PerEncoding = TLOF.getPersonalityEncoding();
const Function *Per = MF->getMMI().getPersonality();
shouldEmitPersonality = hasLandingPads &&
PerEncoding != dwarf::DW_EH_PE_omit && Per;
unsigned LSDAEncoding = TLOF.getLSDAEncoding();
shouldEmitLSDA = shouldEmitPersonality &&
LSDAEncoding != dwarf::DW_EH_PE_omit;
// If this was an outlined handler, we need to define the label corresponding
// to the offset of the parent frame relative to the stack pointer after the
// prologue.
const Function *F = MF->getFunction();
const Function *ParentF = MMI->getWinEHParent(F);
if (F != ParentF) {
WinEHFuncInfo &FuncInfo = MMI->getWinEHFuncInfo(ParentF);
auto I = FuncInfo.CatchHandlerParentFrameObjOffset.find(F);
if (I != FuncInfo.CatchHandlerParentFrameObjOffset.end()) {
MCSymbol *HandlerTypeParentFrameOffset =
Asm->OutContext.getOrCreateParentFrameOffsetSymbol(
GlobalValue::getRealLinkageName(F->getName()));
// Emit a symbol assignment.
Asm->OutStreamer->EmitAssignment(
HandlerTypeParentFrameOffset,
MCConstantExpr::Create(I->second, Asm->OutContext));
}
}
if (!shouldEmitPersonality && !shouldEmitMoves)
return;
Asm->OutStreamer->EmitWinCFIStartProc(Asm->CurrentFnSym);
if (!shouldEmitPersonality)
return;
const MCSymbol *PersHandlerSym =
TLOF.getCFIPersonalitySymbol(Per, *Asm->Mang, Asm->TM, MMI);
Asm->OutStreamer->EmitWinEHHandler(PersHandlerSym, true, true);
}
/// endFunction - Gather and emit post-function exception information.
///
void Win64Exception::endFunction(const MachineFunction *MF) {
if (!shouldEmitPersonality && !shouldEmitMoves)
return;
EHPersonality Per = MMI->getPersonalityType();
// Get rid of any dead landing pads if we're not using a Windows EH scheme. In
// Windows EH schemes, the landing pad is not actually reachable. It only
// exists so that we can emit the right table data.
if (!isMSVCEHPersonality(Per))
MMI->TidyLandingPads();
if (shouldEmitPersonality) {
Asm->OutStreamer->PushSection();
// Emit an UNWIND_INFO struct describing the prologue.
Asm->OutStreamer->EmitWinEHHandlerData();
// Emit the tables appropriate to the personality function in use. If we
// don't recognize the personality, assume it uses an Itanium-style LSDA.
if (Per == EHPersonality::MSVC_Win64SEH)
emitCSpecificHandlerTable();
else if (Per == EHPersonality::MSVC_CXX)
emitCXXFrameHandler3Table(MF);
else
emitExceptionTable();
Asm->OutStreamer->PopSection();
}
Asm->OutStreamer->EmitWinCFIEndProc();
}
const MCExpr *Win64Exception::createImageRel32(const MCSymbol *Value) {
if (!Value)
return MCConstantExpr::Create(0, Asm->OutContext);
return MCSymbolRefExpr::Create(Value, MCSymbolRefExpr::VK_COFF_IMGREL32,
Asm->OutContext);
}
const MCExpr *Win64Exception::createImageRel32(const GlobalValue *GV) {
if (!GV)
return MCConstantExpr::Create(0, Asm->OutContext);
return createImageRel32(Asm->getSymbol(GV));
}
/// Emit the language-specific data that __C_specific_handler expects. This
/// handler lives in the x64 Microsoft C runtime and allows catching or cleaning
/// up after faults with __try, __except, and __finally. The typeinfo values
/// are not really RTTI data, but pointers to filter functions that return an
/// integer (1, 0, or -1) indicating how to handle the exception. For __finally
/// blocks and other cleanups, the landing pad label is zero, and the filter
/// function is actually a cleanup handler with the same prototype. A catch-all
/// entry is modeled with a null filter function field and a non-zero landing
/// pad label.
///
/// Possible filter function return values:
/// EXCEPTION_EXECUTE_HANDLER (1):
/// Jump to the landing pad label after cleanups.
/// EXCEPTION_CONTINUE_SEARCH (0):
/// Continue searching this table or continue unwinding.
/// EXCEPTION_CONTINUE_EXECUTION (-1):
/// Resume execution at the trapping PC.
///
/// Inferred table structure:
/// struct Table {
/// int NumEntries;
/// struct Entry {
/// imagerel32 LabelStart;
/// imagerel32 LabelEnd;
/// imagerel32 FilterOrFinally; // One means catch-all.
/// imagerel32 LabelLPad; // Zero means __finally.
/// } Entries[NumEntries];
/// };
void Win64Exception::emitCSpecificHandlerTable() {
const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
// Simplifying assumptions for first implementation:
// - Cleanups are not implemented.
// - Filters are not implemented.
// The Itanium LSDA table sorts similar landing pads together to simplify the
// actions table, but we don't need that.
SmallVector<const LandingPadInfo *, 64> LandingPads;
LandingPads.reserve(PadInfos.size());
for (const auto &LP : PadInfos)
LandingPads.push_back(&LP);
// Compute label ranges for call sites as we would for the Itanium LSDA, but
// use an all zero action table because we aren't using these actions.
SmallVector<unsigned, 64> FirstActions;
FirstActions.resize(LandingPads.size());
SmallVector<CallSiteEntry, 64> CallSites;
computeCallSiteTable(CallSites, LandingPads, FirstActions);
MCSymbol *EHFuncBeginSym = Asm->getFunctionBegin();
MCSymbol *EHFuncEndSym = Asm->getFunctionEnd();
// Emit the number of table entries.
unsigned NumEntries = 0;
for (const CallSiteEntry &CSE : CallSites) {
if (!CSE.LPad)
continue; // Ignore gaps.
NumEntries += CSE.LPad->SEHHandlers.size();
}
Asm->OutStreamer->EmitIntValue(NumEntries, 4);
// If there are no actions, we don't need to iterate again.
if (NumEntries == 0)
return;
// Emit the four-label records for each call site entry. The table has to be
// sorted in layout order, and the call sites should already be sorted.
for (const CallSiteEntry &CSE : CallSites) {
// Ignore gaps. Unlike the Itanium model, unwinding through a frame without
// an EH table entry will propagate the exception rather than terminating
// the program.
if (!CSE.LPad)
continue;
const LandingPadInfo *LPad = CSE.LPad;
// Compute the label range. We may reuse the function begin and end labels
// rather than forming new ones.
const MCExpr *Begin =
createImageRel32(CSE.BeginLabel ? CSE.BeginLabel : EHFuncBeginSym);
const MCExpr *End;
if (CSE.EndLabel) {
// The interval is half-open, so we have to add one to include the return
// address of the last invoke in the range.
End = MCBinaryExpr::CreateAdd(createImageRel32(CSE.EndLabel),
MCConstantExpr::Create(1, Asm->OutContext),
Asm->OutContext);
} else {
End = createImageRel32(EHFuncEndSym);
}
// Emit an entry for each action.
for (SEHHandler Handler : LPad->SEHHandlers) {
Asm->OutStreamer->EmitValue(Begin, 4);
Asm->OutStreamer->EmitValue(End, 4);
// Emit the filter or finally function pointer, if present. Otherwise,
// emit '1' to indicate a catch-all.
const Function *F = Handler.FilterOrFinally;
if (F)
Asm->OutStreamer->EmitValue(createImageRel32(Asm->getSymbol(F)), 4);
else
Asm->OutStreamer->EmitIntValue(1, 4);
// Emit the recovery address, if present. Otherwise, this must be a
// finally.
const BlockAddress *BA = Handler.RecoverBA;
if (BA)
Asm->OutStreamer->EmitValue(
createImageRel32(Asm->GetBlockAddressSymbol(BA)), 4);
else
Asm->OutStreamer->EmitIntValue(0, 4);
}
}
}
void Win64Exception::emitCXXFrameHandler3Table(const MachineFunction *MF) {
const Function *F = MF->getFunction();
const Function *ParentF = MMI->getWinEHParent(F);
auto &OS = *Asm->OutStreamer;
WinEHFuncInfo &FuncInfo = MMI->getWinEHFuncInfo(ParentF);
StringRef ParentLinkageName =
GlobalValue::getRealLinkageName(ParentF->getName());
MCSymbol *FuncInfoXData =
Asm->OutContext.getOrCreateSymbol(Twine("$cppxdata$", ParentLinkageName));
OS.EmitValue(createImageRel32(FuncInfoXData), 4);
// The Itanium LSDA table sorts similar landing pads together to simplify the
// actions table, but we don't need that.
SmallVector<const LandingPadInfo *, 64> LandingPads;
const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
LandingPads.reserve(PadInfos.size());
for (const auto &LP : PadInfos)
LandingPads.push_back(&LP);
RangeMapType PadMap;
computePadMap(LandingPads, PadMap);
// The end label of the previous invoke or nounwind try-range.
MCSymbol *LastLabel = Asm->getFunctionBegin();
// Whether there is a potentially throwing instruction (currently this means
// an ordinary call) between the end of the previous try-range and now.
bool SawPotentiallyThrowing = false;
int LastEHState = -2;
// The parent function and the catch handlers contribute to the 'ip2state'
// table.
// Include ip2state entries for the beginning of the main function and
// for catch handler functions.
if (F == ParentF) {
FuncInfo.IPToStateList.push_back(std::make_pair(LastLabel, -1));
LastEHState = -1;
} else if (FuncInfo.HandlerBaseState.count(F)) {
FuncInfo.IPToStateList.push_back(std::make_pair(LastLabel,
FuncInfo.HandlerBaseState[F]));
LastEHState = FuncInfo.HandlerBaseState[F];
}
for (const auto &MBB : *MF) {
for (const auto &MI : MBB) {
if (!MI.isEHLabel()) {
if (MI.isCall())
SawPotentiallyThrowing |= !callToNoUnwindFunction(&MI);
continue;
}
// End of the previous try-range?
MCSymbol *BeginLabel = MI.getOperand(0).getMCSymbol();
if (BeginLabel == LastLabel)
SawPotentiallyThrowing = false;
// Beginning of a new try-range?
RangeMapType::const_iterator L = PadMap.find(BeginLabel);
if (L == PadMap.end())
// Nope, it was just some random label.
continue;
const PadRange &P = L->second;
const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
"Inconsistent landing pad map!");
// FIXME: Should this be using FuncInfo.HandlerBaseState?
if (SawPotentiallyThrowing && LastEHState != -1) {
FuncInfo.IPToStateList.push_back(std::make_pair(LastLabel, -1));
SawPotentiallyThrowing = false;
LastEHState = -1;
}
if (LandingPad->WinEHState != LastEHState)
FuncInfo.IPToStateList.push_back(
std::make_pair(BeginLabel, LandingPad->WinEHState));
LastEHState = LandingPad->WinEHState;
LastLabel = LandingPad->EndLabels[P.RangeIndex];
}
}
// Defer emission until we've visited the parent function and all the catch
// handlers. Cleanups don't contribute to the ip2state table yet, so don't
// count them.
if (ParentF != F && !FuncInfo.CatchHandlerMaxState.count(F))
return;
++FuncInfo.NumIPToStateFuncsVisited;
if (FuncInfo.NumIPToStateFuncsVisited != FuncInfo.CatchHandlerMaxState.size())
return;
MCSymbol *UnwindMapXData = nullptr;
MCSymbol *TryBlockMapXData = nullptr;
MCSymbol *IPToStateXData = nullptr;
if (!FuncInfo.UnwindMap.empty())
UnwindMapXData = Asm->OutContext.getOrCreateSymbol(
Twine("$stateUnwindMap$", ParentLinkageName));
if (!FuncInfo.TryBlockMap.empty())
TryBlockMapXData = Asm->OutContext.getOrCreateSymbol(
Twine("$tryMap$", ParentLinkageName));
if (!FuncInfo.IPToStateList.empty())
IPToStateXData = Asm->OutContext.getOrCreateSymbol(
Twine("$ip2state$", ParentLinkageName));
// FuncInfo {
// uint32_t MagicNumber
// int32_t MaxState;
// UnwindMapEntry *UnwindMap;
// uint32_t NumTryBlocks;
// TryBlockMapEntry *TryBlockMap;
// uint32_t IPMapEntries;
// IPToStateMapEntry *IPToStateMap;
// uint32_t UnwindHelp; // (x64/ARM only)
// ESTypeList *ESTypeList;
// int32_t EHFlags;
// }
// EHFlags & 1 -> Synchronous exceptions only, no async exceptions.
// EHFlags & 2 -> ???
// EHFlags & 4 -> The function is noexcept(true), unwinding can't continue.
OS.EmitLabel(FuncInfoXData);
OS.EmitIntValue(0x19930522, 4); // MagicNumber
OS.EmitIntValue(FuncInfo.UnwindMap.size(), 4); // MaxState
OS.EmitValue(createImageRel32(UnwindMapXData), 4); // UnwindMap
OS.EmitIntValue(FuncInfo.TryBlockMap.size(), 4); // NumTryBlocks
OS.EmitValue(createImageRel32(TryBlockMapXData), 4); // TryBlockMap
OS.EmitIntValue(FuncInfo.IPToStateList.size(), 4); // IPMapEntries
OS.EmitValue(createImageRel32(IPToStateXData), 4); // IPToStateMap
OS.EmitIntValue(FuncInfo.UnwindHelpFrameOffset, 4); // UnwindHelp
OS.EmitIntValue(0, 4); // ESTypeList
OS.EmitIntValue(1, 4); // EHFlags
// UnwindMapEntry {
// int32_t ToState;
// void (*Action)();
// };
if (UnwindMapXData) {
OS.EmitLabel(UnwindMapXData);
for (const WinEHUnwindMapEntry &UME : FuncInfo.UnwindMap) {
OS.EmitIntValue(UME.ToState, 4); // ToState
OS.EmitValue(createImageRel32(UME.Cleanup), 4); // Action
}
}
// TryBlockMap {
// int32_t TryLow;
// int32_t TryHigh;
// int32_t CatchHigh;
// int32_t NumCatches;
// HandlerType *HandlerArray;
// };
if (TryBlockMapXData) {
OS.EmitLabel(TryBlockMapXData);
SmallVector<MCSymbol *, 1> HandlerMaps;
for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
MCSymbol *HandlerMapXData = nullptr;
if (!TBME.HandlerArray.empty())
HandlerMapXData =
Asm->OutContext.getOrCreateSymbol(Twine("$handlerMap$")
.concat(Twine(I))
.concat("$")
.concat(ParentLinkageName));
HandlerMaps.push_back(HandlerMapXData);
int CatchHigh = -1;
for (WinEHHandlerType &HT : TBME.HandlerArray)
CatchHigh =
std::max(CatchHigh, FuncInfo.CatchHandlerMaxState[HT.Handler]);
assert(TBME.TryLow <= TBME.TryHigh);
OS.EmitIntValue(TBME.TryLow, 4); // TryLow
OS.EmitIntValue(TBME.TryHigh, 4); // TryHigh
OS.EmitIntValue(CatchHigh, 4); // CatchHigh
OS.EmitIntValue(TBME.HandlerArray.size(), 4); // NumCatches
OS.EmitValue(createImageRel32(HandlerMapXData), 4); // HandlerArray
}
for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
MCSymbol *HandlerMapXData = HandlerMaps[I];
if (!HandlerMapXData)
continue;
// HandlerType {
// int32_t Adjectives;
// TypeDescriptor *Type;
// int32_t CatchObjOffset;
// void (*Handler)();
// int32_t ParentFrameOffset; // x64 only
// };
OS.EmitLabel(HandlerMapXData);
for (const WinEHHandlerType &HT : TBME.HandlerArray) {
MCSymbol *ParentFrameOffset =
Asm->OutContext.getOrCreateParentFrameOffsetSymbol(
GlobalValue::getRealLinkageName(HT.Handler->getName()));
const MCSymbolRefExpr *ParentFrameOffsetRef = MCSymbolRefExpr::Create(
ParentFrameOffset, MCSymbolRefExpr::VK_None, Asm->OutContext);
// Get the frame escape label with the offset of the catch object. If
// the index is -1, then there is no catch object, and we should emit an
// offset of zero, indicating that no copy will occur.
const MCExpr *FrameAllocOffsetRef = nullptr;
if (HT.CatchObjRecoverIdx >= 0) {
MCSymbol *FrameAllocOffset =
Asm->OutContext.getOrCreateFrameAllocSymbol(
GlobalValue::getRealLinkageName(ParentF->getName()),
HT.CatchObjRecoverIdx);
FrameAllocOffsetRef = MCSymbolRefExpr::Create(
FrameAllocOffset, MCSymbolRefExpr::VK_None, Asm->OutContext);
} else {
FrameAllocOffsetRef = MCConstantExpr::Create(0, Asm->OutContext);
}
OS.EmitIntValue(HT.Adjectives, 4); // Adjectives
OS.EmitValue(createImageRel32(HT.TypeDescriptor), 4); // Type
OS.EmitValue(FrameAllocOffsetRef, 4); // CatchObjOffset
OS.EmitValue(createImageRel32(HT.Handler), 4); // Handler
OS.EmitValue(ParentFrameOffsetRef, 4); // ParentFrameOffset
}
}
}
// IPToStateMapEntry {
// void *IP;
// int32_t State;
// };
if (IPToStateXData) {
OS.EmitLabel(IPToStateXData);
for (auto &IPStatePair : FuncInfo.IPToStateList) {
OS.EmitValue(createImageRel32(IPStatePair.first), 4); // IP
OS.EmitIntValue(IPStatePair.second, 4); // State
}
}
}
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