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7a1a2170b7
For `.bss; nop`, MC inappropriately calls abort() (via report_fatal_error()) with a message `cannot have fixups in virtual section!` It is a bug to crash for invalid user input. Fix it by erroring out early in EmitInstToData(). Similarly, emitIntValue() in a virtual section (SHT_NOBITS in ELF) can crash with the mssage `non-zero initializer found in section '.bss'` (see D4199) It'd be nice to report the location but so many directives can call emitIntValue() and it is difficult to track every location. Note, COFF does not crash because MCAssembler::writeSectionData() is not called for an IMAGE_SCN_CNT_UNINITIALIZED_DATA section. Note, GNU as' arm64 backend reports ``Error: attempt to store non-zero value in section `.bss'`` for a non-zero .inst but fails to do so for other instructions. We simply reject all instructions, even if the encoding is all zeros. The Mach-O counterpart is D48517 (see `test/MC/MachO/zerofill-text.s`) Reviewed By: rnk, skan Differential Revision: https://reviews.llvm.org/D78138
95 lines
3.4 KiB
C++
95 lines
3.4 KiB
C++
//===- MCSectionCOFF.h - COFF Machine Code Sections -------------*- 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 declares the MCSectionCOFF class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_MC_MCSECTIONCOFF_H
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#define LLVM_MC_MCSECTIONCOFF_H
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#include "llvm/ADT/StringRef.h"
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#include "llvm/MC/MCSection.h"
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#include "llvm/MC/SectionKind.h"
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#include <cassert>
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namespace llvm {
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class MCSymbol;
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/// This represents a section on Windows
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class MCSectionCOFF final : public MCSection {
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// FIXME: The following fields should not be mutable, but are for now so the
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// asm parser can honor the .linkonce directive.
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/// This is the Characteristics field of a section, drawn from the enums
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/// below.
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mutable unsigned Characteristics;
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/// The unique IDs used with the .pdata and .xdata sections created internally
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/// by the assembler. This ID is used to ensure that for every .text section,
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/// there is exactly one .pdata and one .xdata section, which is required by
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/// the Microsoft incremental linker. This data is mutable because this ID is
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/// not notionally part of the section.
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mutable unsigned WinCFISectionID = ~0U;
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/// The COMDAT symbol of this section. Only valid if this is a COMDAT section.
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/// Two COMDAT sections are merged if they have the same COMDAT symbol.
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MCSymbol *COMDATSymbol;
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/// This is the Selection field for the section symbol, if it is a COMDAT
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/// section (Characteristics & IMAGE_SCN_LNK_COMDAT) != 0
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mutable int Selection;
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private:
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friend class MCContext;
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// The storage of Name is owned by MCContext's COFFUniquingMap.
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MCSectionCOFF(StringRef Name, unsigned Characteristics,
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MCSymbol *COMDATSymbol, int Selection, SectionKind K,
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MCSymbol *Begin)
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: MCSection(SV_COFF, Name, K, Begin), Characteristics(Characteristics),
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COMDATSymbol(COMDATSymbol), Selection(Selection) {
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assert((Characteristics & 0x00F00000) == 0 &&
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"alignment must not be set upon section creation");
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}
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public:
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/// Decides whether a '.section' directive should be printed before the
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/// section name
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bool ShouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) const;
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unsigned getCharacteristics() const { return Characteristics; }
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MCSymbol *getCOMDATSymbol() const { return COMDATSymbol; }
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int getSelection() const { return Selection; }
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void setSelection(int Selection) const;
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void PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
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raw_ostream &OS,
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const MCExpr *Subsection) const override;
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bool UseCodeAlign() const override;
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bool isVirtualSection() const override;
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StringRef getVirtualSectionKind() const override;
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unsigned getOrAssignWinCFISectionID(unsigned *NextID) const {
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if (WinCFISectionID == ~0U)
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WinCFISectionID = (*NextID)++;
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return WinCFISectionID;
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}
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static bool isImplicitlyDiscardable(StringRef Name) {
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return Name.startswith(".debug");
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}
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static bool classof(const MCSection *S) { return S->getVariant() == SV_COFF; }
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};
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} // end namespace llvm
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#endif // LLVM_MC_MCSECTIONCOFF_H
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