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llvm-mirror/lib/CodeGen/AsmPrinter/WinException.cpp
Arlo Siemsen d4eefe6819 Add ehcont section support 
In the future Windows will enable Control-flow Enforcement Technology (CET aka shadow stacks). To protect the path where the context is updated during exception handling, the binary is required to enumerate valid unwind entrypoints in a dedicated section which is validated when the context is being set during exception handling.

This change allows llvm to generate the section that contains the appropriate symbol references in the form expected by the msvc linker.

This feature is enabled through a new module flag, ehcontguard, which was modelled on the cfguard flag.

The change includes a test that when the module flag is enabled the section is correctly generated.

The set of exception continuation information includes returns from exceptional control flow (catchret in llvm).

In order to collect catchret we:
1) Includes an additional flag on machine basic blocks to indicate that the given block is the target of a catchret operation,
2) Introduces a new machine function pass to insert and collect symbols at the start of each block, and
3) Combines these targets with the other EHCont targets that were already being collected.

Change originally authored by Daniel Frampton <dframpto@microsoft.com>

For more details, see MSVC documentation for `/guard:ehcont`
  https://docs.microsoft.com/en-us/cpp/build/reference/guard-enable-eh-continuation-metadata

Reviewed By: pengfei

Differential Revision: https://reviews.llvm.org/D94835
2021-02-15 14:27:12 +08:00

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//===-- CodeGen/AsmPrinter/WinException.cpp - Dwarf Exception Impl ------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing Win64 exception info into asm files.
//
//===----------------------------------------------------------------------===//
#include "WinException.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/COFF.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetSubtargetInfo.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/ErrorHandling.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
using namespace llvm;
WinException::WinException(AsmPrinter *A) : EHStreamer(A) {
// MSVC's EH tables are always composed of 32-bit words. All known 64-bit
// platforms use an imagerel32 relocation to refer to symbols.
useImageRel32 = (A->getDataLayout().getPointerSizeInBits() == 64);
isAArch64 = Asm->TM.getTargetTriple().isAArch64();
}
WinException::~WinException() {}
/// endModule - Emit all exception information that should come after the
/// content.
void WinException::endModule() {
auto &OS = *Asm->OutStreamer;
const Module *M = MMI->getModule();
for (const Function &F : *M)
if (F.hasFnAttribute("safeseh"))
OS.EmitCOFFSafeSEH(Asm->getSymbol(&F));
if (M->getModuleFlag("ehcontguard") && !EHContTargets.empty()) {
// Emit the symbol index of each ehcont target.
OS.SwitchSection(Asm->OutContext.getObjectFileInfo()->getGEHContSection());
for (const MCSymbol *S : EHContTargets) {
OS.EmitCOFFSymbolIndex(S);
}
}
}
void WinException::beginFunction(const MachineFunction *MF) {
shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
// If any landing pads survive, we need an EH table.
bool hasLandingPads = !MF->getLandingPads().empty();
bool hasEHFunclets = MF->hasEHFunclets();
const Function &F = MF->getFunction();
shouldEmitMoves = Asm->needsSEHMoves() && MF->hasWinCFI();
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
unsigned PerEncoding = TLOF.getPersonalityEncoding();
EHPersonality Per = EHPersonality::Unknown;
const Function *PerFn = nullptr;
if (F.hasPersonalityFn()) {
PerFn = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
Per = classifyEHPersonality(PerFn);
}
bool forceEmitPersonality = F.hasPersonalityFn() &&
!isNoOpWithoutInvoke(Per) &&
F.needsUnwindTableEntry();
shouldEmitPersonality =
forceEmitPersonality || ((hasLandingPads || hasEHFunclets) &&
PerEncoding != dwarf::DW_EH_PE_omit && PerFn);
unsigned LSDAEncoding = TLOF.getLSDAEncoding();
shouldEmitLSDA = shouldEmitPersonality &&
LSDAEncoding != dwarf::DW_EH_PE_omit;
// If we're not using CFI, we don't want the CFI or the personality, but we
// might want EH tables if we had EH pads.
if (!Asm->MAI->usesWindowsCFI()) {
if (Per == EHPersonality::MSVC_X86SEH && !hasEHFunclets) {
// If this is 32-bit SEH and we don't have any funclets (really invokes),
// make sure we emit the parent offset label. Some unreferenced filter
// functions may still refer to it.
const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
StringRef FLinkageName =
GlobalValue::dropLLVMManglingEscape(MF->getFunction().getName());
emitEHRegistrationOffsetLabel(FuncInfo, FLinkageName);
}
shouldEmitLSDA = hasEHFunclets;
shouldEmitPersonality = false;
return;
}
beginFunclet(MF->front(), Asm->CurrentFnSym);
}
void WinException::markFunctionEnd() {
if (isAArch64 && CurrentFuncletEntry &&
(shouldEmitMoves || shouldEmitPersonality))
Asm->OutStreamer->EmitWinCFIFuncletOrFuncEnd();
}
/// endFunction - Gather and emit post-function exception information.
///
void WinException::endFunction(const MachineFunction *MF) {
if (!shouldEmitPersonality && !shouldEmitMoves && !shouldEmitLSDA)
return;
const Function &F = MF->getFunction();
EHPersonality Per = EHPersonality::Unknown;
if (F.hasPersonalityFn())
Per = classifyEHPersonality(F.getPersonalityFn()->stripPointerCasts());
// Get rid of any dead landing pads if we're not using funclets. In funclet
// schemes, the landing pad is not actually reachable. It only exists so
// that we can emit the right table data.
if (!isFuncletEHPersonality(Per)) {
MachineFunction *NonConstMF = const_cast<MachineFunction*>(MF);
NonConstMF->tidyLandingPads();
}
endFuncletImpl();
// endFunclet will emit the necessary .xdata tables for table-based SEH.
if (Per == EHPersonality::MSVC_TableSEH && MF->hasEHFunclets())
return;
if (shouldEmitPersonality || shouldEmitLSDA) {
Asm->OutStreamer->PushSection();
// Just switch sections to the right xdata section.
MCSection *XData = Asm->OutStreamer->getAssociatedXDataSection(
Asm->OutStreamer->getCurrentSectionOnly());
Asm->OutStreamer->SwitchSection(XData);
// 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_TableSEH)
emitCSpecificHandlerTable(MF);
else if (Per == EHPersonality::MSVC_X86SEH)
emitExceptHandlerTable(MF);
else if (Per == EHPersonality::MSVC_CXX)
emitCXXFrameHandler3Table(MF);
else if (Per == EHPersonality::CoreCLR)
emitCLRExceptionTable(MF);
else
emitExceptionTable();
Asm->OutStreamer->PopSection();
}
if (!MF->getCatchretTargets().empty()) {
// Copy the function's catchret targets to a module-level list.
EHContTargets.insert(EHContTargets.end(), MF->getCatchretTargets().begin(),
MF->getCatchretTargets().end());
}
}
/// Retrieve the MCSymbol for a GlobalValue or MachineBasicBlock.
static MCSymbol *getMCSymbolForMBB(AsmPrinter *Asm,
const MachineBasicBlock *MBB) {
if (!MBB)
return nullptr;
assert(MBB->isEHFuncletEntry());
// Give catches and cleanups a name based off of their parent function and
// their funclet entry block's number.
const MachineFunction *MF = MBB->getParent();
const Function &F = MF->getFunction();
StringRef FuncLinkageName = GlobalValue::dropLLVMManglingEscape(F.getName());
MCContext &Ctx = MF->getContext();
StringRef HandlerPrefix = MBB->isCleanupFuncletEntry() ? "dtor" : "catch";
return Ctx.getOrCreateSymbol("?" + HandlerPrefix + "$" +
Twine(MBB->getNumber()) + "@?0?" +
FuncLinkageName + "@4HA");
}
void WinException::beginFunclet(const MachineBasicBlock &MBB,
MCSymbol *Sym) {
CurrentFuncletEntry = &MBB;
const Function &F = Asm->MF->getFunction();
// If a symbol was not provided for the funclet, invent one.
if (!Sym) {
Sym = getMCSymbolForMBB(Asm, &MBB);
// Describe our funclet symbol as a function with internal linkage.
Asm->OutStreamer->BeginCOFFSymbolDef(Sym);
Asm->OutStreamer->EmitCOFFSymbolStorageClass(COFF::IMAGE_SYM_CLASS_STATIC);
Asm->OutStreamer->EmitCOFFSymbolType(COFF::IMAGE_SYM_DTYPE_FUNCTION
<< COFF::SCT_COMPLEX_TYPE_SHIFT);
Asm->OutStreamer->EndCOFFSymbolDef();
// We want our funclet's entry point to be aligned such that no nops will be
// present after the label.
Asm->emitAlignment(std::max(Asm->MF->getAlignment(), MBB.getAlignment()),
&F);
// Now that we've emitted the alignment directive, point at our funclet.
Asm->OutStreamer->emitLabel(Sym);
}
// Mark 'Sym' as starting our funclet.
if (shouldEmitMoves || shouldEmitPersonality) {
CurrentFuncletTextSection = Asm->OutStreamer->getCurrentSectionOnly();
Asm->OutStreamer->EmitWinCFIStartProc(Sym);
}
if (shouldEmitPersonality) {
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
const Function *PerFn = nullptr;
// Determine which personality routine we are using for this funclet.
if (F.hasPersonalityFn())
PerFn = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
const MCSymbol *PersHandlerSym =
TLOF.getCFIPersonalitySymbol(PerFn, Asm->TM, MMI);
// Do not emit a .seh_handler directives for cleanup funclets.
// FIXME: This means cleanup funclets cannot handle exceptions. Given that
// Clang doesn't produce EH constructs inside cleanup funclets and LLVM's
// inliner doesn't allow inlining them, this isn't a major problem in
// practice.
if (!CurrentFuncletEntry->isCleanupFuncletEntry())
Asm->OutStreamer->EmitWinEHHandler(PersHandlerSym, true, true);
}
}
void WinException::endFunclet() {
if (isAArch64 && CurrentFuncletEntry &&
(shouldEmitMoves || shouldEmitPersonality)) {
Asm->OutStreamer->SwitchSection(CurrentFuncletTextSection);
Asm->OutStreamer->EmitWinCFIFuncletOrFuncEnd();
}
endFuncletImpl();
}
void WinException::endFuncletImpl() {
// No funclet to process? Great, we have nothing to do.
if (!CurrentFuncletEntry)
return;
const MachineFunction *MF = Asm->MF;
if (shouldEmitMoves || shouldEmitPersonality) {
const Function &F = MF->getFunction();
EHPersonality Per = EHPersonality::Unknown;
if (F.hasPersonalityFn())
Per = classifyEHPersonality(F.getPersonalityFn()->stripPointerCasts());
if (Per == EHPersonality::MSVC_CXX && shouldEmitPersonality &&
!CurrentFuncletEntry->isCleanupFuncletEntry()) {
// Emit an UNWIND_INFO struct describing the prologue.
Asm->OutStreamer->EmitWinEHHandlerData();
// If this is a C++ catch funclet (or the parent function),
// emit a reference to the LSDA for the parent function.
StringRef FuncLinkageName = GlobalValue::dropLLVMManglingEscape(F.getName());
MCSymbol *FuncInfoXData = Asm->OutContext.getOrCreateSymbol(
Twine("$cppxdata$", FuncLinkageName));
Asm->OutStreamer->emitValue(create32bitRef(FuncInfoXData), 4);
} else if (Per == EHPersonality::MSVC_TableSEH && MF->hasEHFunclets() &&
!CurrentFuncletEntry->isEHFuncletEntry()) {
// Emit an UNWIND_INFO struct describing the prologue.
Asm->OutStreamer->EmitWinEHHandlerData();
// If this is the parent function in Win64 SEH, emit the LSDA immediately
// following .seh_handlerdata.
emitCSpecificHandlerTable(MF);
} else if (shouldEmitPersonality || shouldEmitLSDA) {
// Emit an UNWIND_INFO struct describing the prologue.
Asm->OutStreamer->EmitWinEHHandlerData();
// In these cases, no further info is written to the .xdata section
// right here, but is written by e.g. emitExceptionTable in endFunction()
// above.
} else {
// No need to emit the EH handler data right here if nothing needs
// writing to the .xdata section; it will be emitted for all
// functions that need it in the end anyway.
}
// Switch back to the funclet start .text section now that we are done
// writing to .xdata, and emit an .seh_endproc directive to mark the end of
// the function.
Asm->OutStreamer->SwitchSection(CurrentFuncletTextSection);
Asm->OutStreamer->EmitWinCFIEndProc();
}
// Let's make sure we don't try to end the same funclet twice.
CurrentFuncletEntry = nullptr;
}
const MCExpr *WinException::create32bitRef(const MCSymbol *Value) {
if (!Value)
return MCConstantExpr::create(0, Asm->OutContext);
return MCSymbolRefExpr::create(Value, useImageRel32
? MCSymbolRefExpr::VK_COFF_IMGREL32
: MCSymbolRefExpr::VK_None,
Asm->OutContext);
}
const MCExpr *WinException::create32bitRef(const GlobalValue *GV) {
if (!GV)
return MCConstantExpr::create(0, Asm->OutContext);
return create32bitRef(Asm->getSymbol(GV));
}
const MCExpr *WinException::getLabel(const MCSymbol *Label) {
if (isAArch64)
return MCSymbolRefExpr::create(Label, MCSymbolRefExpr::VK_COFF_IMGREL32,
Asm->OutContext);
return MCBinaryExpr::createAdd(create32bitRef(Label),
MCConstantExpr::create(1, Asm->OutContext),
Asm->OutContext);
}
const MCExpr *WinException::getOffset(const MCSymbol *OffsetOf,
const MCSymbol *OffsetFrom) {
return MCBinaryExpr::createSub(
MCSymbolRefExpr::create(OffsetOf, Asm->OutContext),
MCSymbolRefExpr::create(OffsetFrom, Asm->OutContext), Asm->OutContext);
}
const MCExpr *WinException::getOffsetPlusOne(const MCSymbol *OffsetOf,
const MCSymbol *OffsetFrom) {
return MCBinaryExpr::createAdd(getOffset(OffsetOf, OffsetFrom),
MCConstantExpr::create(1, Asm->OutContext),
Asm->OutContext);
}
int WinException::getFrameIndexOffset(int FrameIndex,
const WinEHFuncInfo &FuncInfo) {
const TargetFrameLowering &TFI = *Asm->MF->getSubtarget().getFrameLowering();
Register UnusedReg;
if (Asm->MAI->usesWindowsCFI()) {
StackOffset Offset =
TFI.getFrameIndexReferencePreferSP(*Asm->MF, FrameIndex, UnusedReg,
/*IgnoreSPUpdates*/ true);
assert(UnusedReg ==
Asm->MF->getSubtarget()
.getTargetLowering()
->getStackPointerRegisterToSaveRestore());
return Offset.getFixed();
}
// For 32-bit, offsets should be relative to the end of the EH registration
// node. For 64-bit, it's relative to SP at the end of the prologue.
assert(FuncInfo.EHRegNodeEndOffset != INT_MAX);
StackOffset Offset = TFI.getFrameIndexReference(*Asm->MF, FrameIndex, UnusedReg);
Offset += StackOffset::getFixed(FuncInfo.EHRegNodeEndOffset);
assert(!Offset.getScalable() &&
"Frame offsets with a scalable component are not supported");
return Offset.getFixed();
}
namespace {
/// Top-level state used to represent unwind to caller
const int NullState = -1;
struct InvokeStateChange {
/// EH Label immediately after the last invoke in the previous state, or
/// nullptr if the previous state was the null state.
const MCSymbol *PreviousEndLabel;
/// EH label immediately before the first invoke in the new state, or nullptr
/// if the new state is the null state.
const MCSymbol *NewStartLabel;
/// State of the invoke following NewStartLabel, or NullState to indicate
/// the presence of calls which may unwind to caller.
int NewState;
};
/// Iterator that reports all the invoke state changes in a range of machine
/// basic blocks. Changes to the null state are reported whenever a call that
/// may unwind to caller is encountered. The MBB range is expected to be an
/// entire function or funclet, and the start and end of the range are treated
/// as being in the NullState even if there's not an unwind-to-caller call
/// before the first invoke or after the last one (i.e., the first state change
/// reported is the first change to something other than NullState, and a
/// change back to NullState is always reported at the end of iteration).
class InvokeStateChangeIterator {
InvokeStateChangeIterator(const WinEHFuncInfo &EHInfo,
MachineFunction::const_iterator MFI,
MachineFunction::const_iterator MFE,
MachineBasicBlock::const_iterator MBBI,
int BaseState)
: EHInfo(EHInfo), MFI(MFI), MFE(MFE), MBBI(MBBI), BaseState(BaseState) {
LastStateChange.PreviousEndLabel = nullptr;
LastStateChange.NewStartLabel = nullptr;
LastStateChange.NewState = BaseState;
scan();
}
public:
static iterator_range<InvokeStateChangeIterator>
range(const WinEHFuncInfo &EHInfo, MachineFunction::const_iterator Begin,
MachineFunction::const_iterator End, int BaseState = NullState) {
// Reject empty ranges to simplify bookkeeping by ensuring that we can get
// the end of the last block.
assert(Begin != End);
auto BlockBegin = Begin->begin();
auto BlockEnd = std::prev(End)->end();
return make_range(
InvokeStateChangeIterator(EHInfo, Begin, End, BlockBegin, BaseState),
InvokeStateChangeIterator(EHInfo, End, End, BlockEnd, BaseState));
}
// Iterator methods.
bool operator==(const InvokeStateChangeIterator &O) const {
assert(BaseState == O.BaseState);
// Must be visiting same block.
if (MFI != O.MFI)
return false;
// Must be visiting same isntr.
if (MBBI != O.MBBI)
return false;
// At end of block/instr iteration, we can still have two distinct states:
// one to report the final EndLabel, and another indicating the end of the
// state change iteration. Check for CurrentEndLabel equality to
// distinguish these.
return CurrentEndLabel == O.CurrentEndLabel;
}
bool operator!=(const InvokeStateChangeIterator &O) const {
return !operator==(O);
}
InvokeStateChange &operator*() { return LastStateChange; }
InvokeStateChange *operator->() { return &LastStateChange; }
InvokeStateChangeIterator &operator++() { return scan(); }
private:
InvokeStateChangeIterator &scan();
const WinEHFuncInfo &EHInfo;
const MCSymbol *CurrentEndLabel = nullptr;
MachineFunction::const_iterator MFI;
MachineFunction::const_iterator MFE;
MachineBasicBlock::const_iterator MBBI;
InvokeStateChange LastStateChange;
bool VisitingInvoke = false;
int BaseState;
};
} // end anonymous namespace
InvokeStateChangeIterator &InvokeStateChangeIterator::scan() {
bool IsNewBlock = false;
for (; MFI != MFE; ++MFI, IsNewBlock = true) {
if (IsNewBlock)
MBBI = MFI->begin();
for (auto MBBE = MFI->end(); MBBI != MBBE; ++MBBI) {
const MachineInstr &MI = *MBBI;
if (!VisitingInvoke && LastStateChange.NewState != BaseState &&
MI.isCall() && !EHStreamer::callToNoUnwindFunction(&MI)) {
// Indicate a change of state to the null state. We don't have
// start/end EH labels handy but the caller won't expect them for
// null state regions.
LastStateChange.PreviousEndLabel = CurrentEndLabel;
LastStateChange.NewStartLabel = nullptr;
LastStateChange.NewState = BaseState;
CurrentEndLabel = nullptr;
// Don't re-visit this instr on the next scan
++MBBI;
return *this;
}
// All other state changes are at EH labels before/after invokes.
if (!MI.isEHLabel())
continue;
MCSymbol *Label = MI.getOperand(0).getMCSymbol();
if (Label == CurrentEndLabel) {
VisitingInvoke = false;
continue;
}
auto InvokeMapIter = EHInfo.LabelToStateMap.find(Label);
// Ignore EH labels that aren't the ones inserted before an invoke
if (InvokeMapIter == EHInfo.LabelToStateMap.end())
continue;
auto &StateAndEnd = InvokeMapIter->second;
int NewState = StateAndEnd.first;
// Keep track of the fact that we're between EH start/end labels so
// we know not to treat the inoke we'll see as unwinding to caller.
VisitingInvoke = true;
if (NewState == LastStateChange.NewState) {
// The state isn't actually changing here. Record the new end and
// keep going.
CurrentEndLabel = StateAndEnd.second;
continue;
}
// Found a state change to report
LastStateChange.PreviousEndLabel = CurrentEndLabel;
LastStateChange.NewStartLabel = Label;
LastStateChange.NewState = NewState;
// Start keeping track of the new current end
CurrentEndLabel = StateAndEnd.second;
// Don't re-visit this instr on the next scan
++MBBI;
return *this;
}
}
// Iteration hit the end of the block range.
if (LastStateChange.NewState != BaseState) {
// Report the end of the last new state
LastStateChange.PreviousEndLabel = CurrentEndLabel;
LastStateChange.NewStartLabel = nullptr;
LastStateChange.NewState = BaseState;
// Leave CurrentEndLabel non-null to distinguish this state from end.
assert(CurrentEndLabel != nullptr);
return *this;
}
// We've reported all state changes and hit the end state.
CurrentEndLabel = nullptr;
return *this;
}
/// 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 WinException::emitCSpecificHandlerTable(const MachineFunction *MF) {
auto &OS = *Asm->OutStreamer;
MCContext &Ctx = Asm->OutContext;
const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
bool VerboseAsm = OS.isVerboseAsm();
auto AddComment = [&](const Twine &Comment) {
if (VerboseAsm)
OS.AddComment(Comment);
};
if (!isAArch64) {
// Emit a label assignment with the SEH frame offset so we can use it for
// llvm.eh.recoverfp.
StringRef FLinkageName =
GlobalValue::dropLLVMManglingEscape(MF->getFunction().getName());
MCSymbol *ParentFrameOffset =
Ctx.getOrCreateParentFrameOffsetSymbol(FLinkageName);
const MCExpr *MCOffset =
MCConstantExpr::create(FuncInfo.SEHSetFrameOffset, Ctx);
Asm->OutStreamer->emitAssignment(ParentFrameOffset, MCOffset);
}
// Use the assembler to compute the number of table entries through label
// difference and division.
MCSymbol *TableBegin =
Ctx.createTempSymbol("lsda_begin", /*AlwaysAddSuffix=*/true);
MCSymbol *TableEnd =
Ctx.createTempSymbol("lsda_end", /*AlwaysAddSuffix=*/true);
const MCExpr *LabelDiff = getOffset(TableEnd, TableBegin);
const MCExpr *EntrySize = MCConstantExpr::create(16, Ctx);
const MCExpr *EntryCount = MCBinaryExpr::createDiv(LabelDiff, EntrySize, Ctx);
AddComment("Number of call sites");
OS.emitValue(EntryCount, 4);
OS.emitLabel(TableBegin);
// Iterate over all the invoke try ranges. Unlike MSVC, LLVM currently only
// models exceptions from invokes. LLVM also allows arbitrary reordering of
// the code, so our tables end up looking a bit different. Rather than
// trying to match MSVC's tables exactly, we emit a denormalized table. For
// each range of invokes in the same state, we emit table entries for all
// the actions that would be taken in that state. This means our tables are
// slightly bigger, which is OK.
const MCSymbol *LastStartLabel = nullptr;
int LastEHState = -1;
// Break out before we enter into a finally funclet.
// FIXME: We need to emit separate EH tables for cleanups.
MachineFunction::const_iterator End = MF->end();
MachineFunction::const_iterator Stop = std::next(MF->begin());
while (Stop != End && !Stop->isEHFuncletEntry())
++Stop;
for (const auto &StateChange :
InvokeStateChangeIterator::range(FuncInfo, MF->begin(), Stop)) {
// Emit all the actions for the state we just transitioned out of
// if it was not the null state
if (LastEHState != -1)
emitSEHActionsForRange(FuncInfo, LastStartLabel,
StateChange.PreviousEndLabel, LastEHState);
LastStartLabel = StateChange.NewStartLabel;
LastEHState = StateChange.NewState;
}
OS.emitLabel(TableEnd);
}
void WinException::emitSEHActionsForRange(const WinEHFuncInfo &FuncInfo,
const MCSymbol *BeginLabel,
const MCSymbol *EndLabel, int State) {
auto &OS = *Asm->OutStreamer;
MCContext &Ctx = Asm->OutContext;
bool VerboseAsm = OS.isVerboseAsm();
auto AddComment = [&](const Twine &Comment) {
if (VerboseAsm)
OS.AddComment(Comment);
};
assert(BeginLabel && EndLabel);
while (State != -1) {
const SEHUnwindMapEntry &UME = FuncInfo.SEHUnwindMap[State];
const MCExpr *FilterOrFinally;
const MCExpr *ExceptOrNull;
auto *Handler = UME.Handler.get<MachineBasicBlock *>();
if (UME.IsFinally) {
FilterOrFinally = create32bitRef(getMCSymbolForMBB(Asm, Handler));
ExceptOrNull = MCConstantExpr::create(0, Ctx);
} else {
// For an except, the filter can be 1 (catch-all) or a function
// label.
FilterOrFinally = UME.Filter ? create32bitRef(UME.Filter)
: MCConstantExpr::create(1, Ctx);
ExceptOrNull = create32bitRef(Handler->getSymbol());
}
AddComment("LabelStart");
OS.emitValue(getLabel(BeginLabel), 4);
AddComment("LabelEnd");
OS.emitValue(getLabel(EndLabel), 4);
AddComment(UME.IsFinally ? "FinallyFunclet" : UME.Filter ? "FilterFunction"
: "CatchAll");
OS.emitValue(FilterOrFinally, 4);
AddComment(UME.IsFinally ? "Null" : "ExceptionHandler");
OS.emitValue(ExceptOrNull, 4);
assert(UME.ToState < State && "states should decrease");
State = UME.ToState;
}
}
void WinException::emitCXXFrameHandler3Table(const MachineFunction *MF) {
const Function &F = MF->getFunction();
auto &OS = *Asm->OutStreamer;
const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
StringRef FuncLinkageName = GlobalValue::dropLLVMManglingEscape(F.getName());
SmallVector<std::pair<const MCExpr *, int>, 4> IPToStateTable;
MCSymbol *FuncInfoXData = nullptr;
if (shouldEmitPersonality) {
// If we're 64-bit, emit a pointer to the C++ EH data, and build a map from
// IPs to state numbers.
FuncInfoXData =
Asm->OutContext.getOrCreateSymbol(Twine("$cppxdata$", FuncLinkageName));
computeIP2StateTable(MF, FuncInfo, IPToStateTable);
} else {
FuncInfoXData = Asm->OutContext.getOrCreateLSDASymbol(FuncLinkageName);
}
int UnwindHelpOffset = 0;
if (Asm->MAI->usesWindowsCFI())
UnwindHelpOffset =
getFrameIndexOffset(FuncInfo.UnwindHelpFrameIdx, FuncInfo);
MCSymbol *UnwindMapXData = nullptr;
MCSymbol *TryBlockMapXData = nullptr;
MCSymbol *IPToStateXData = nullptr;
if (!FuncInfo.CxxUnwindMap.empty())
UnwindMapXData = Asm->OutContext.getOrCreateSymbol(
Twine("$stateUnwindMap$", FuncLinkageName));
if (!FuncInfo.TryBlockMap.empty())
TryBlockMapXData =
Asm->OutContext.getOrCreateSymbol(Twine("$tryMap$", FuncLinkageName));
if (!IPToStateTable.empty())
IPToStateXData =
Asm->OutContext.getOrCreateSymbol(Twine("$ip2state$", FuncLinkageName));
bool VerboseAsm = OS.isVerboseAsm();
auto AddComment = [&](const Twine &Comment) {
if (VerboseAsm)
OS.AddComment(Comment);
};
// FuncInfo {
// uint32_t MagicNumber
// int32_t MaxState;
// UnwindMapEntry *UnwindMap;
// uint32_t NumTryBlocks;
// TryBlockMapEntry *TryBlockMap;
// uint32_t IPMapEntries; // always 0 for x86
// IPToStateMapEntry *IPToStateMap; // always 0 for x86
// uint32_t UnwindHelp; // non-x86 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.emitValueToAlignment(4);
OS.emitLabel(FuncInfoXData);
AddComment("MagicNumber");
OS.emitInt32(0x19930522);
AddComment("MaxState");
OS.emitInt32(FuncInfo.CxxUnwindMap.size());
AddComment("UnwindMap");
OS.emitValue(create32bitRef(UnwindMapXData), 4);
AddComment("NumTryBlocks");
OS.emitInt32(FuncInfo.TryBlockMap.size());
AddComment("TryBlockMap");
OS.emitValue(create32bitRef(TryBlockMapXData), 4);
AddComment("IPMapEntries");
OS.emitInt32(IPToStateTable.size());
AddComment("IPToStateXData");
OS.emitValue(create32bitRef(IPToStateXData), 4);
if (Asm->MAI->usesWindowsCFI()) {
AddComment("UnwindHelp");
OS.emitInt32(UnwindHelpOffset);
}
AddComment("ESTypeList");
OS.emitInt32(0);
AddComment("EHFlags");
OS.emitInt32(1);
// UnwindMapEntry {
// int32_t ToState;
// void (*Action)();
// };
if (UnwindMapXData) {
OS.emitLabel(UnwindMapXData);
for (const CxxUnwindMapEntry &UME : FuncInfo.CxxUnwindMap) {
MCSymbol *CleanupSym =
getMCSymbolForMBB(Asm, UME.Cleanup.dyn_cast<MachineBasicBlock *>());
AddComment("ToState");
OS.emitInt32(UME.ToState);
AddComment("Action");
OS.emitValue(create32bitRef(CleanupSym), 4);
}
}
// 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) {
const WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
MCSymbol *HandlerMapXData = nullptr;
if (!TBME.HandlerArray.empty())
HandlerMapXData =
Asm->OutContext.getOrCreateSymbol(Twine("$handlerMap$")
.concat(Twine(I))
.concat("$")
.concat(FuncLinkageName));
HandlerMaps.push_back(HandlerMapXData);
// TBMEs should form intervals.
assert(0 <= TBME.TryLow && "bad trymap interval");
assert(TBME.TryLow <= TBME.TryHigh && "bad trymap interval");
assert(TBME.TryHigh < TBME.CatchHigh && "bad trymap interval");
assert(TBME.CatchHigh < int(FuncInfo.CxxUnwindMap.size()) &&
"bad trymap interval");
AddComment("TryLow");
OS.emitInt32(TBME.TryLow);
AddComment("TryHigh");
OS.emitInt32(TBME.TryHigh);
AddComment("CatchHigh");
OS.emitInt32(TBME.CatchHigh);
AddComment("NumCatches");
OS.emitInt32(TBME.HandlerArray.size());
AddComment("HandlerArray");
OS.emitValue(create32bitRef(HandlerMapXData), 4);
}
// All funclets use the same parent frame offset currently.
unsigned ParentFrameOffset = 0;
if (shouldEmitPersonality) {
const TargetFrameLowering *TFI = MF->getSubtarget().getFrameLowering();
ParentFrameOffset = TFI->getWinEHParentFrameOffset(*MF);
}
for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
const 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 and AArch64 only
// };
OS.emitLabel(HandlerMapXData);
for (const WinEHHandlerType &HT : TBME.HandlerArray) {
// Get the frame escape label with the offset of the catch object. If
// the index is INT_MAX, 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.CatchObj.FrameIndex != INT_MAX) {
int Offset = getFrameIndexOffset(HT.CatchObj.FrameIndex, FuncInfo);
assert(Offset != 0 && "Illegal offset for catch object!");
FrameAllocOffsetRef = MCConstantExpr::create(Offset, Asm->OutContext);
} else {
FrameAllocOffsetRef = MCConstantExpr::create(0, Asm->OutContext);
}
MCSymbol *HandlerSym =
getMCSymbolForMBB(Asm, HT.Handler.dyn_cast<MachineBasicBlock *>());
AddComment("Adjectives");
OS.emitInt32(HT.Adjectives);
AddComment("Type");
OS.emitValue(create32bitRef(HT.TypeDescriptor), 4);
AddComment("CatchObjOffset");
OS.emitValue(FrameAllocOffsetRef, 4);
AddComment("Handler");
OS.emitValue(create32bitRef(HandlerSym), 4);
if (shouldEmitPersonality) {
AddComment("ParentFrameOffset");
OS.emitInt32(ParentFrameOffset);
}
}
}
}
// IPToStateMapEntry {
// void *IP;
// int32_t State;
// };
if (IPToStateXData) {
OS.emitLabel(IPToStateXData);
for (auto &IPStatePair : IPToStateTable) {
AddComment("IP");
OS.emitValue(IPStatePair.first, 4);
AddComment("ToState");
OS.emitInt32(IPStatePair.second);
}
}
}
void WinException::computeIP2StateTable(
const MachineFunction *MF, const WinEHFuncInfo &FuncInfo,
SmallVectorImpl<std::pair<const MCExpr *, int>> &IPToStateTable) {
for (MachineFunction::const_iterator FuncletStart = MF->begin(),
FuncletEnd = MF->begin(),
End = MF->end();
FuncletStart != End; FuncletStart = FuncletEnd) {
// Find the end of the funclet
while (++FuncletEnd != End) {
if (FuncletEnd->isEHFuncletEntry()) {
break;
}
}
// Don't emit ip2state entries for cleanup funclets. Any interesting
// exceptional actions in cleanups must be handled in a separate IR
// function.
if (FuncletStart->isCleanupFuncletEntry())
continue;
MCSymbol *StartLabel;
int BaseState;
if (FuncletStart == MF->begin()) {
BaseState = NullState;
StartLabel = Asm->getFunctionBegin();
} else {
auto *FuncletPad =
cast<FuncletPadInst>(FuncletStart->getBasicBlock()->getFirstNonPHI());
assert(FuncInfo.FuncletBaseStateMap.count(FuncletPad) != 0);
BaseState = FuncInfo.FuncletBaseStateMap.find(FuncletPad)->second;
StartLabel = getMCSymbolForMBB(Asm, &*FuncletStart);
}
assert(StartLabel && "need local function start label");
IPToStateTable.push_back(
std::make_pair(create32bitRef(StartLabel), BaseState));
for (const auto &StateChange : InvokeStateChangeIterator::range(
FuncInfo, FuncletStart, FuncletEnd, BaseState)) {
// Compute the label to report as the start of this entry; use the EH
// start label for the invoke if we have one, otherwise (this is a call
// which may unwind to our caller and does not have an EH start label, so)
// use the previous end label.
const MCSymbol *ChangeLabel = StateChange.NewStartLabel;
if (!ChangeLabel)
ChangeLabel = StateChange.PreviousEndLabel;
// Emit an entry indicating that PCs after 'Label' have this EH state.
IPToStateTable.push_back(
std::make_pair(getLabel(ChangeLabel), StateChange.NewState));
// FIXME: assert that NewState is between CatchLow and CatchHigh.
}
}
}
void WinException::emitEHRegistrationOffsetLabel(const WinEHFuncInfo &FuncInfo,
StringRef FLinkageName) {
// Outlined helpers called by the EH runtime need to know the offset of the EH
// registration in order to recover the parent frame pointer. Now that we know
// we've code generated the parent, we can emit the label assignment that
// those helpers use to get the offset of the registration node.
// Compute the parent frame offset. The EHRegNodeFrameIndex will be invalid if
// after optimization all the invokes were eliminated. We still need to emit
// the parent frame offset label, but it should be garbage and should never be
// used.
int64_t Offset = 0;
int FI = FuncInfo.EHRegNodeFrameIndex;
if (FI != INT_MAX) {
const TargetFrameLowering *TFI = Asm->MF->getSubtarget().getFrameLowering();
Offset = TFI->getNonLocalFrameIndexReference(*Asm->MF, FI).getFixed();
}
MCContext &Ctx = Asm->OutContext;
MCSymbol *ParentFrameOffset =
Ctx.getOrCreateParentFrameOffsetSymbol(FLinkageName);
Asm->OutStreamer->emitAssignment(ParentFrameOffset,
MCConstantExpr::create(Offset, Ctx));
}
/// Emit the language-specific data that _except_handler3 and 4 expect. This is
/// functionally equivalent to the __C_specific_handler table, except it is
/// indexed by state number instead of IP.
void WinException::emitExceptHandlerTable(const MachineFunction *MF) {
MCStreamer &OS = *Asm->OutStreamer;
const Function &F = MF->getFunction();
StringRef FLinkageName = GlobalValue::dropLLVMManglingEscape(F.getName());
bool VerboseAsm = OS.isVerboseAsm();
auto AddComment = [&](const Twine &Comment) {
if (VerboseAsm)
OS.AddComment(Comment);
};
const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
emitEHRegistrationOffsetLabel(FuncInfo, FLinkageName);
// Emit the __ehtable label that we use for llvm.x86.seh.lsda.
MCSymbol *LSDALabel = Asm->OutContext.getOrCreateLSDASymbol(FLinkageName);
OS.emitValueToAlignment(4);
OS.emitLabel(LSDALabel);
const auto *Per = cast<Function>(F.getPersonalityFn()->stripPointerCasts());
StringRef PerName = Per->getName();
int BaseState = -1;
if (PerName == "_except_handler4") {
// The LSDA for _except_handler4 starts with this struct, followed by the
// scope table:
//
// struct EH4ScopeTable {
// int32_t GSCookieOffset;
// int32_t GSCookieXOROffset;
// int32_t EHCookieOffset;
// int32_t EHCookieXOROffset;
// ScopeTableEntry ScopeRecord[];
// };
//
// Offsets are %ebp relative.
//
// The GS cookie is present only if the function needs stack protection.
// GSCookieOffset = -2 means that GS cookie is not used.
//
// The EH cookie is always present.
//
// Check is done the following way:
// (ebp+CookieXOROffset) ^ [ebp+CookieOffset] == _security_cookie
// Retrieve the Guard Stack slot.
int GSCookieOffset = -2;
const MachineFrameInfo &MFI = MF->getFrameInfo();
if (MFI.hasStackProtectorIndex()) {
Register UnusedReg;
const TargetFrameLowering *TFI = MF->getSubtarget().getFrameLowering();
int SSPIdx = MFI.getStackProtectorIndex();
GSCookieOffset =
TFI->getFrameIndexReference(*MF, SSPIdx, UnusedReg).getFixed();
}
// Retrieve the EH Guard slot.
// TODO(etienneb): Get rid of this value and change it for and assertion.
int EHCookieOffset = 9999;
if (FuncInfo.EHGuardFrameIndex != INT_MAX) {
Register UnusedReg;
const TargetFrameLowering *TFI = MF->getSubtarget().getFrameLowering();
int EHGuardIdx = FuncInfo.EHGuardFrameIndex;
EHCookieOffset =
TFI->getFrameIndexReference(*MF, EHGuardIdx, UnusedReg).getFixed();
}
AddComment("GSCookieOffset");
OS.emitInt32(GSCookieOffset);
AddComment("GSCookieXOROffset");
OS.emitInt32(0);
AddComment("EHCookieOffset");
OS.emitInt32(EHCookieOffset);
AddComment("EHCookieXOROffset");
OS.emitInt32(0);
BaseState = -2;
}
assert(!FuncInfo.SEHUnwindMap.empty());
for (const SEHUnwindMapEntry &UME : FuncInfo.SEHUnwindMap) {
auto *Handler = UME.Handler.get<MachineBasicBlock *>();
const MCSymbol *ExceptOrFinally =
UME.IsFinally ? getMCSymbolForMBB(Asm, Handler) : Handler->getSymbol();
// -1 is usually the base state for "unwind to caller", but for
// _except_handler4 it's -2. Do that replacement here if necessary.
int ToState = UME.ToState == -1 ? BaseState : UME.ToState;
AddComment("ToState");
OS.emitInt32(ToState);
AddComment(UME.IsFinally ? "Null" : "FilterFunction");
OS.emitValue(create32bitRef(UME.Filter), 4);
AddComment(UME.IsFinally ? "FinallyFunclet" : "ExceptionHandler");
OS.emitValue(create32bitRef(ExceptOrFinally), 4);
}
}
static int getTryRank(const WinEHFuncInfo &FuncInfo, int State) {
int Rank = 0;
while (State != -1) {
++Rank;
State = FuncInfo.ClrEHUnwindMap[State].TryParentState;
}
return Rank;
}
static int getTryAncestor(const WinEHFuncInfo &FuncInfo, int Left, int Right) {
int LeftRank = getTryRank(FuncInfo, Left);
int RightRank = getTryRank(FuncInfo, Right);
while (LeftRank < RightRank) {
Right = FuncInfo.ClrEHUnwindMap[Right].TryParentState;
--RightRank;
}
while (RightRank < LeftRank) {
Left = FuncInfo.ClrEHUnwindMap[Left].TryParentState;
--LeftRank;
}
while (Left != Right) {
Left = FuncInfo.ClrEHUnwindMap[Left].TryParentState;
Right = FuncInfo.ClrEHUnwindMap[Right].TryParentState;
}
return Left;
}
void WinException::emitCLRExceptionTable(const MachineFunction *MF) {
// CLR EH "states" are really just IDs that identify handlers/funclets;
// states, handlers, and funclets all have 1:1 mappings between them, and a
// handler/funclet's "state" is its index in the ClrEHUnwindMap.
MCStreamer &OS = *Asm->OutStreamer;
const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
MCSymbol *FuncBeginSym = Asm->getFunctionBegin();
MCSymbol *FuncEndSym = Asm->getFunctionEnd();
// A ClrClause describes a protected region.
struct ClrClause {
const MCSymbol *StartLabel; // Start of protected region
const MCSymbol *EndLabel; // End of protected region
int State; // Index of handler protecting the protected region
int EnclosingState; // Index of funclet enclosing the protected region
};
SmallVector<ClrClause, 8> Clauses;
// Build a map from handler MBBs to their corresponding states (i.e. their
// indices in the ClrEHUnwindMap).
int NumStates = FuncInfo.ClrEHUnwindMap.size();
assert(NumStates > 0 && "Don't need exception table!");
DenseMap<const MachineBasicBlock *, int> HandlerStates;
for (int State = 0; State < NumStates; ++State) {
MachineBasicBlock *HandlerBlock =
FuncInfo.ClrEHUnwindMap[State].Handler.get<MachineBasicBlock *>();
HandlerStates[HandlerBlock] = State;
// Use this loop through all handlers to verify our assumption (used in
// the MinEnclosingState computation) that enclosing funclets have lower
// state numbers than their enclosed funclets.
assert(FuncInfo.ClrEHUnwindMap[State].HandlerParentState < State &&
"ill-formed state numbering");
}
// Map the main function to the NullState.
HandlerStates[&MF->front()] = NullState;
// Write out a sentinel indicating the end of the standard (Windows) xdata
// and the start of the additional (CLR) info.
OS.emitInt32(0xffffffff);
// Write out the number of funclets
OS.emitInt32(NumStates);
// Walk the machine blocks/instrs, computing and emitting a few things:
// 1. Emit a list of the offsets to each handler entry, in lexical order.
// 2. Compute a map (EndSymbolMap) from each funclet to the symbol at its end.
// 3. Compute the list of ClrClauses, in the required order (inner before
// outer, earlier before later; the order by which a forward scan with
// early termination will find the innermost enclosing clause covering
// a given address).
// 4. A map (MinClauseMap) from each handler index to the index of the
// outermost funclet/function which contains a try clause targeting the
// key handler. This will be used to determine IsDuplicate-ness when
// emitting ClrClauses. The NullState value is used to indicate that the
// top-level function contains a try clause targeting the key handler.
// HandlerStack is a stack of (PendingStartLabel, PendingState) pairs for
// try regions we entered before entering the PendingState try but which
// we haven't yet exited.
SmallVector<std::pair<const MCSymbol *, int>, 4> HandlerStack;
// EndSymbolMap and MinClauseMap are maps described above.
std::unique_ptr<MCSymbol *[]> EndSymbolMap(new MCSymbol *[NumStates]);
SmallVector<int, 4> MinClauseMap((size_t)NumStates, NumStates);
// Visit the root function and each funclet.
for (MachineFunction::const_iterator FuncletStart = MF->begin(),
FuncletEnd = MF->begin(),
End = MF->end();
FuncletStart != End; FuncletStart = FuncletEnd) {
int FuncletState = HandlerStates[&*FuncletStart];
// Find the end of the funclet
MCSymbol *EndSymbol = FuncEndSym;
while (++FuncletEnd != End) {
if (FuncletEnd->isEHFuncletEntry()) {
EndSymbol = getMCSymbolForMBB(Asm, &*FuncletEnd);
break;
}
}
// Emit the function/funclet end and, if this is a funclet (and not the
// root function), record it in the EndSymbolMap.
OS.emitValue(getOffset(EndSymbol, FuncBeginSym), 4);
if (FuncletState != NullState) {
// Record the end of the handler.
EndSymbolMap[FuncletState] = EndSymbol;
}
// Walk the state changes in this function/funclet and compute its clauses.
// Funclets always start in the null state.
const MCSymbol *CurrentStartLabel = nullptr;
int CurrentState = NullState;
assert(HandlerStack.empty());
for (const auto &StateChange :
InvokeStateChangeIterator::range(FuncInfo, FuncletStart, FuncletEnd)) {
// Close any try regions we're not still under
int StillPendingState =
getTryAncestor(FuncInfo, CurrentState, StateChange.NewState);
while (CurrentState != StillPendingState) {
assert(CurrentState != NullState &&
"Failed to find still-pending state!");
// Close the pending clause
Clauses.push_back({CurrentStartLabel, StateChange.PreviousEndLabel,
CurrentState, FuncletState});
// Now the next-outer try region is current
CurrentState = FuncInfo.ClrEHUnwindMap[CurrentState].TryParentState;
// Pop the new start label from the handler stack if we've exited all
// inner try regions of the corresponding try region.
if (HandlerStack.back().second == CurrentState)
CurrentStartLabel = HandlerStack.pop_back_val().first;
}
if (StateChange.NewState != CurrentState) {
// For each clause we're starting, update the MinClauseMap so we can
// know which is the topmost funclet containing a clause targeting
// it.
for (int EnteredState = StateChange.NewState;
EnteredState != CurrentState;
EnteredState =
FuncInfo.ClrEHUnwindMap[EnteredState].TryParentState) {
int &MinEnclosingState = MinClauseMap[EnteredState];
if (FuncletState < MinEnclosingState)
MinEnclosingState = FuncletState;
}
// Save the previous current start/label on the stack and update to
// the newly-current start/state.
HandlerStack.emplace_back(CurrentStartLabel, CurrentState);
CurrentStartLabel = StateChange.NewStartLabel;
CurrentState = StateChange.NewState;
}
}
assert(HandlerStack.empty());
}
// Now emit the clause info, starting with the number of clauses.
OS.emitInt32(Clauses.size());
for (ClrClause &Clause : Clauses) {
// Emit a CORINFO_EH_CLAUSE :
/*
struct CORINFO_EH_CLAUSE
{
CORINFO_EH_CLAUSE_FLAGS Flags; // actually a CorExceptionFlag
DWORD TryOffset;
DWORD TryLength; // actually TryEndOffset
DWORD HandlerOffset;
DWORD HandlerLength; // actually HandlerEndOffset
union
{
DWORD ClassToken; // use for catch clauses
DWORD FilterOffset; // use for filter clauses
};
};
enum CORINFO_EH_CLAUSE_FLAGS
{
CORINFO_EH_CLAUSE_NONE = 0,
CORINFO_EH_CLAUSE_FILTER = 0x0001, // This clause is for a filter
CORINFO_EH_CLAUSE_FINALLY = 0x0002, // This clause is a finally clause
CORINFO_EH_CLAUSE_FAULT = 0x0004, // This clause is a fault clause
};
typedef enum CorExceptionFlag
{
COR_ILEXCEPTION_CLAUSE_NONE,
COR_ILEXCEPTION_CLAUSE_FILTER = 0x0001, // This is a filter clause
COR_ILEXCEPTION_CLAUSE_FINALLY = 0x0002, // This is a finally clause
COR_ILEXCEPTION_CLAUSE_FAULT = 0x0004, // This is a fault clause
COR_ILEXCEPTION_CLAUSE_DUPLICATED = 0x0008, // duplicated clause. This
// clause was duplicated
// to a funclet which was
// pulled out of line
} CorExceptionFlag;
*/
// Add 1 to the start/end of the EH clause; the IP associated with a
// call when the runtime does its scan is the IP of the next instruction
// (the one to which control will return after the call), so we need
// to add 1 to the end of the clause to cover that offset. We also add
// 1 to the start of the clause to make sure that the ranges reported
// for all clauses are disjoint. Note that we'll need some additional
// logic when machine traps are supported, since in that case the IP
// that the runtime uses is the offset of the faulting instruction
// itself; if such an instruction immediately follows a call but the
// two belong to different clauses, we'll need to insert a nop between
// them so the runtime can distinguish the point to which the call will
// return from the point at which the fault occurs.
const MCExpr *ClauseBegin =
getOffsetPlusOne(Clause.StartLabel, FuncBeginSym);
const MCExpr *ClauseEnd = getOffsetPlusOne(Clause.EndLabel, FuncBeginSym);
const ClrEHUnwindMapEntry &Entry = FuncInfo.ClrEHUnwindMap[Clause.State];
MachineBasicBlock *HandlerBlock = Entry.Handler.get<MachineBasicBlock *>();
MCSymbol *BeginSym = getMCSymbolForMBB(Asm, HandlerBlock);
const MCExpr *HandlerBegin = getOffset(BeginSym, FuncBeginSym);
MCSymbol *EndSym = EndSymbolMap[Clause.State];
const MCExpr *HandlerEnd = getOffset(EndSym, FuncBeginSym);
uint32_t Flags = 0;
switch (Entry.HandlerType) {
case ClrHandlerType::Catch:
// Leaving bits 0-2 clear indicates catch.
break;
case ClrHandlerType::Filter:
Flags |= 1;
break;
case ClrHandlerType::Finally:
Flags |= 2;
break;
case ClrHandlerType::Fault:
Flags |= 4;
break;
}
if (Clause.EnclosingState != MinClauseMap[Clause.State]) {
// This is a "duplicate" clause; the handler needs to be entered from a
// frame above the one holding the invoke.
assert(Clause.EnclosingState > MinClauseMap[Clause.State]);
Flags |= 8;
}
OS.emitInt32(Flags);
// Write the clause start/end
OS.emitValue(ClauseBegin, 4);
OS.emitValue(ClauseEnd, 4);
// Write out the handler start/end
OS.emitValue(HandlerBegin, 4);
OS.emitValue(HandlerEnd, 4);
// Write out the type token or filter offset
assert(Entry.HandlerType != ClrHandlerType::Filter && "NYI: filters");
OS.emitInt32(Entry.TypeToken);
}
}
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