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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
117 lines
4.2 KiB
C++
117 lines
4.2 KiB
C++
//===-- WinException.h - Windows Exception Handling ----------*- C++ -*--===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains support for writing windows exception info into asm files.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIB_CODEGEN_ASMPRINTER_WIN64EXCEPTION_H
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#define LLVM_LIB_CODEGEN_ASMPRINTER_WIN64EXCEPTION_H
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#include "EHStreamer.h"
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namespace llvm {
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class GlobalValue;
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class MachineFunction;
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class MCExpr;
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class MCSection;
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struct WinEHFuncInfo;
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class LLVM_LIBRARY_VISIBILITY WinException : public EHStreamer {
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/// Per-function flag to indicate if personality info should be emitted.
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bool shouldEmitPersonality = false;
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/// Per-function flag to indicate if the LSDA should be emitted.
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bool shouldEmitLSDA = false;
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/// Per-function flag to indicate if frame moves info should be emitted.
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bool shouldEmitMoves = false;
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/// True if this is a 64-bit target and we should use image relative offsets.
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bool useImageRel32 = false;
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/// True if we are generating exception handling on Windows for ARM64.
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bool isAArch64 = false;
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/// Pointer to the current funclet entry BB.
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const MachineBasicBlock *CurrentFuncletEntry = nullptr;
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/// The section of the last funclet start.
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MCSection *CurrentFuncletTextSection = nullptr;
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/// The list of symbols to add to the ehcont section
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std::vector<const MCSymbol *> EHContTargets;
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void emitCSpecificHandlerTable(const MachineFunction *MF);
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void emitSEHActionsForRange(const WinEHFuncInfo &FuncInfo,
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const MCSymbol *BeginLabel,
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const MCSymbol *EndLabel, int State);
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/// Emit the EH table data for 32-bit and 64-bit functions using
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/// the __CxxFrameHandler3 personality.
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void emitCXXFrameHandler3Table(const MachineFunction *MF);
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/// Emit the EH table data for _except_handler3 and _except_handler4
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/// personality functions. These are only used on 32-bit and do not use CFI
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/// tables.
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void emitExceptHandlerTable(const MachineFunction *MF);
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void emitCLRExceptionTable(const MachineFunction *MF);
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void computeIP2StateTable(
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const MachineFunction *MF, const WinEHFuncInfo &FuncInfo,
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SmallVectorImpl<std::pair<const MCExpr *, int>> &IPToStateTable);
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/// Emits the label used with llvm.eh.recoverfp, which is used by
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/// outlined funclets.
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void emitEHRegistrationOffsetLabel(const WinEHFuncInfo &FuncInfo,
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StringRef FLinkageName);
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const MCExpr *create32bitRef(const MCSymbol *Value);
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const MCExpr *create32bitRef(const GlobalValue *GV);
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const MCExpr *getLabel(const MCSymbol *Label);
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const MCExpr *getOffset(const MCSymbol *OffsetOf, const MCSymbol *OffsetFrom);
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const MCExpr *getOffsetPlusOne(const MCSymbol *OffsetOf,
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const MCSymbol *OffsetFrom);
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/// Gets the offset that we should use in a table for a stack object with the
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/// given index. For targets using CFI (Win64, etc), this is relative to the
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/// established SP at the end of the prologue. For targets without CFI (Win32
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/// only), it is relative to the frame pointer.
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int getFrameIndexOffset(int FrameIndex, const WinEHFuncInfo &FuncInfo);
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void endFuncletImpl();
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public:
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//===--------------------------------------------------------------------===//
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// Main entry points.
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//
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WinException(AsmPrinter *A);
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~WinException() override;
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/// Emit all exception information that should come after the content.
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void endModule() override;
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/// Gather pre-function exception information. Assumes being emitted
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/// immediately after the function entry point.
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void beginFunction(const MachineFunction *MF) override;
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void markFunctionEnd() override;
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/// Gather and emit post-function exception information.
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void endFunction(const MachineFunction *) override;
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/// Emit target-specific EH funclet machinery.
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void beginFunclet(const MachineBasicBlock &MBB, MCSymbol *Sym) override;
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void endFunclet() override;
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};
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}
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#endif
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