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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
118 lines
3.5 KiB
C++
118 lines
3.5 KiB
C++
//===- lib/MC/MCSectionCOFF.cpp - COFF Code Section Representation --------===//
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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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#include "llvm/MC/MCSectionCOFF.h"
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#include "llvm/BinaryFormat/COFF.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/Support/raw_ostream.h"
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#include <cassert>
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using namespace llvm;
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// ShouldOmitSectionDirective - Decides whether a '.section' directive
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// should be printed before the section name
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bool MCSectionCOFF::ShouldOmitSectionDirective(StringRef Name,
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const MCAsmInfo &MAI) const {
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if (COMDATSymbol)
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return false;
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// FIXME: Does .section .bss/.data/.text work everywhere??
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if (Name == ".text" || Name == ".data" || Name == ".bss")
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return true;
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return false;
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}
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void MCSectionCOFF::setSelection(int Selection) const {
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assert(Selection != 0 && "invalid COMDAT selection type");
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this->Selection = Selection;
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Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
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}
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void MCSectionCOFF::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
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raw_ostream &OS,
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const MCExpr *Subsection) const {
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// standard sections don't require the '.section'
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if (ShouldOmitSectionDirective(getName(), MAI)) {
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OS << '\t' << getName() << '\n';
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return;
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}
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OS << "\t.section\t" << getName() << ",\"";
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if (getCharacteristics() & COFF::IMAGE_SCN_CNT_INITIALIZED_DATA)
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OS << 'd';
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if (getCharacteristics() & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA)
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OS << 'b';
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if (getCharacteristics() & COFF::IMAGE_SCN_MEM_EXECUTE)
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OS << 'x';
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if (getCharacteristics() & COFF::IMAGE_SCN_MEM_WRITE)
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OS << 'w';
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else if (getCharacteristics() & COFF::IMAGE_SCN_MEM_READ)
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OS << 'r';
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else
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OS << 'y';
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if (getCharacteristics() & COFF::IMAGE_SCN_LNK_REMOVE)
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OS << 'n';
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if (getCharacteristics() & COFF::IMAGE_SCN_MEM_SHARED)
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OS << 's';
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if ((getCharacteristics() & COFF::IMAGE_SCN_MEM_DISCARDABLE) &&
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!isImplicitlyDiscardable(getName()))
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OS << 'D';
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OS << '"';
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if (getCharacteristics() & COFF::IMAGE_SCN_LNK_COMDAT) {
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if (COMDATSymbol)
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OS << ",";
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else
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OS << "\n\t.linkonce\t";
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switch (Selection) {
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case COFF::IMAGE_COMDAT_SELECT_NODUPLICATES:
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OS << "one_only";
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break;
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case COFF::IMAGE_COMDAT_SELECT_ANY:
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OS << "discard";
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break;
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case COFF::IMAGE_COMDAT_SELECT_SAME_SIZE:
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OS << "same_size";
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break;
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case COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH:
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OS << "same_contents";
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break;
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case COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE:
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OS << "associative";
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break;
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case COFF::IMAGE_COMDAT_SELECT_LARGEST:
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OS << "largest";
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break;
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case COFF::IMAGE_COMDAT_SELECT_NEWEST:
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OS << "newest";
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break;
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default:
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assert(false && "unsupported COFF selection type");
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break;
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}
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if (COMDATSymbol) {
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OS << ",";
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COMDATSymbol->print(OS, &MAI);
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}
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}
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OS << '\n';
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}
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bool MCSectionCOFF::UseCodeAlign() const {
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return getKind().isText();
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}
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bool MCSectionCOFF::isVirtualSection() const {
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return getCharacteristics() & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA;
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}
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StringRef MCSectionCOFF::getVirtualSectionKind() const {
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return "IMAGE_SCN_CNT_UNINITIALIZED_DATA";
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}
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