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293 lines
10 KiB
C++
293 lines
10 KiB
C++
//===-- ARMELFObjectWriter.cpp - ARM ELF Writer ---------------------------===//
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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 "MCTargetDesc/ARMFixupKinds.h"
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#include "MCTargetDesc/ARMMCTargetDesc.h"
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#include "llvm/BinaryFormat/ELF.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCELFObjectWriter.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCFixup.h"
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#include "llvm/MC/MCObjectFileInfo.h"
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#include "llvm/MC/MCObjectWriter.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include <cstdint>
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using namespace llvm;
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namespace {
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class ARMELFObjectWriter : public MCELFObjectTargetWriter {
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enum { DefaultEABIVersion = 0x05000000U };
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unsigned GetRelocTypeInner(const MCValue &Target, const MCFixup &Fixup,
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bool IsPCRel, MCContext &Ctx) const;
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public:
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ARMELFObjectWriter(uint8_t OSABI);
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~ARMELFObjectWriter() override = default;
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unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
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const MCFixup &Fixup, bool IsPCRel) const override;
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bool needsRelocateWithSymbol(const MCSymbol &Sym,
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unsigned Type) const override;
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void addTargetSectionFlags(MCContext &Ctx, MCSectionELF &Sec) override;
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};
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} // end anonymous namespace
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ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI)
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: MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI,
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ELF::EM_ARM,
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/*HasRelocationAddend*/ false) {}
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bool ARMELFObjectWriter::needsRelocateWithSymbol(const MCSymbol &Sym,
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unsigned Type) const {
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// FIXME: This is extremely conservative. This really needs to use an
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// explicit list with a clear explanation for why each realocation needs to
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// point to the symbol, not to the section.
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switch (Type) {
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default:
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return true;
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case ELF::R_ARM_PREL31:
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case ELF::R_ARM_ABS32:
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return false;
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}
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}
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// Need to examine the Fixup when determining whether to
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// emit the relocation as an explicit symbol or as a section relative
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// offset
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unsigned ARMELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
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const MCFixup &Fixup,
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bool IsPCRel) const {
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return GetRelocTypeInner(Target, Fixup, IsPCRel, Ctx);
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}
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unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target,
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const MCFixup &Fixup,
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bool IsPCRel,
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MCContext &Ctx) const {
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unsigned Kind = Fixup.getTargetKind();
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if (Kind >= FirstLiteralRelocationKind)
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return Kind - FirstLiteralRelocationKind;
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MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
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if (IsPCRel) {
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switch (Fixup.getTargetKind()) {
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default:
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Ctx.reportFatalError(Fixup.getLoc(), "unsupported relocation on symbol");
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return ELF::R_ARM_NONE;
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case FK_Data_4:
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switch (Modifier) {
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default:
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Ctx.reportError(Fixup.getLoc(),
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"invalid fixup for 4-byte pc-relative data relocation");
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return ELF::R_ARM_NONE;
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case MCSymbolRefExpr::VK_None: {
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if (const MCSymbolRefExpr *SymRef = Target.getSymA()) {
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// For GNU AS compatibility expressions such as
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// _GLOBAL_OFFSET_TABLE_ - label emit a R_ARM_BASE_PREL relocation.
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if (SymRef->getSymbol().getName() == "_GLOBAL_OFFSET_TABLE_")
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return ELF::R_ARM_BASE_PREL;
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}
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return ELF::R_ARM_REL32;
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}
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case MCSymbolRefExpr::VK_GOTTPOFF:
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return ELF::R_ARM_TLS_IE32;
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case MCSymbolRefExpr::VK_ARM_GOT_PREL:
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return ELF::R_ARM_GOT_PREL;
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case MCSymbolRefExpr::VK_ARM_PREL31:
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return ELF::R_ARM_PREL31;
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}
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case ARM::fixup_arm_blx:
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case ARM::fixup_arm_uncondbl:
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switch (Modifier) {
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case MCSymbolRefExpr::VK_PLT:
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return ELF::R_ARM_CALL;
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case MCSymbolRefExpr::VK_TLSCALL:
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return ELF::R_ARM_TLS_CALL;
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default:
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return ELF::R_ARM_CALL;
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}
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case ARM::fixup_arm_condbl:
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case ARM::fixup_arm_condbranch:
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case ARM::fixup_arm_uncondbranch:
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return ELF::R_ARM_JUMP24;
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case ARM::fixup_t2_condbranch:
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return ELF::R_ARM_THM_JUMP19;
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case ARM::fixup_t2_uncondbranch:
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return ELF::R_ARM_THM_JUMP24;
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case ARM::fixup_arm_movt_hi16:
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return ELF::R_ARM_MOVT_PREL;
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case ARM::fixup_arm_movw_lo16:
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return ELF::R_ARM_MOVW_PREL_NC;
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case ARM::fixup_t2_movt_hi16:
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return ELF::R_ARM_THM_MOVT_PREL;
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case ARM::fixup_t2_movw_lo16:
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return ELF::R_ARM_THM_MOVW_PREL_NC;
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case ARM::fixup_arm_thumb_br:
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return ELF::R_ARM_THM_JUMP11;
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case ARM::fixup_arm_thumb_bcc:
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return ELF::R_ARM_THM_JUMP8;
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case ARM::fixup_arm_thumb_bl:
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case ARM::fixup_arm_thumb_blx:
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switch (Modifier) {
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case MCSymbolRefExpr::VK_TLSCALL:
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return ELF::R_ARM_THM_TLS_CALL;
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default:
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return ELF::R_ARM_THM_CALL;
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}
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case ARM::fixup_bf_target:
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return ELF::R_ARM_THM_BF16;
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case ARM::fixup_bfc_target:
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return ELF::R_ARM_THM_BF12;
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case ARM::fixup_bfl_target:
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return ELF::R_ARM_THM_BF18;
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}
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}
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switch (Kind) {
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default:
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Ctx.reportFatalError(Fixup.getLoc(), "unsupported relocation on symbol");
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return ELF::R_ARM_NONE;
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case FK_Data_1:
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switch (Modifier) {
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default:
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Ctx.reportError(Fixup.getLoc(),
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"invalid fixup for 1-byte data relocation");
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return ELF::R_ARM_NONE;
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case MCSymbolRefExpr::VK_None:
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return ELF::R_ARM_ABS8;
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}
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case FK_Data_2:
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switch (Modifier) {
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default:
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Ctx.reportError(Fixup.getLoc(),
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"invalid fixup for 2-byte data relocation");
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return ELF::R_ARM_NONE;
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case MCSymbolRefExpr::VK_None:
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return ELF::R_ARM_ABS16;
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}
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case FK_Data_4:
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switch (Modifier) {
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default:
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Ctx.reportError(Fixup.getLoc(),
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"invalid fixup for 4-byte data relocation");
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return ELF::R_ARM_NONE;
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case MCSymbolRefExpr::VK_ARM_NONE:
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return ELF::R_ARM_NONE;
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case MCSymbolRefExpr::VK_GOT:
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return ELF::R_ARM_GOT_BREL;
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case MCSymbolRefExpr::VK_TLSGD:
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return ELF::R_ARM_TLS_GD32;
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case MCSymbolRefExpr::VK_TPOFF:
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return ELF::R_ARM_TLS_LE32;
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case MCSymbolRefExpr::VK_GOTTPOFF:
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return ELF::R_ARM_TLS_IE32;
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case MCSymbolRefExpr::VK_None:
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return ELF::R_ARM_ABS32;
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case MCSymbolRefExpr::VK_GOTOFF:
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return ELF::R_ARM_GOTOFF32;
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case MCSymbolRefExpr::VK_ARM_GOT_PREL:
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return ELF::R_ARM_GOT_PREL;
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case MCSymbolRefExpr::VK_ARM_TARGET1:
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return ELF::R_ARM_TARGET1;
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case MCSymbolRefExpr::VK_ARM_TARGET2:
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return ELF::R_ARM_TARGET2;
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case MCSymbolRefExpr::VK_ARM_PREL31:
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return ELF::R_ARM_PREL31;
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case MCSymbolRefExpr::VK_ARM_SBREL:
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return ELF::R_ARM_SBREL32;
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case MCSymbolRefExpr::VK_ARM_TLSLDO:
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return ELF::R_ARM_TLS_LDO32;
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case MCSymbolRefExpr::VK_TLSCALL:
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return ELF::R_ARM_TLS_CALL;
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case MCSymbolRefExpr::VK_TLSDESC:
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return ELF::R_ARM_TLS_GOTDESC;
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case MCSymbolRefExpr::VK_TLSLDM:
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return ELF::R_ARM_TLS_LDM32;
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case MCSymbolRefExpr::VK_ARM_TLSDESCSEQ:
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return ELF::R_ARM_TLS_DESCSEQ;
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}
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case ARM::fixup_arm_condbranch:
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case ARM::fixup_arm_uncondbranch:
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return ELF::R_ARM_JUMP24;
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case ARM::fixup_arm_movt_hi16:
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switch (Modifier) {
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default:
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Ctx.reportError(Fixup.getLoc(), "invalid fixup for ARM MOVT instruction");
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return ELF::R_ARM_NONE;
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case MCSymbolRefExpr::VK_None:
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return ELF::R_ARM_MOVT_ABS;
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case MCSymbolRefExpr::VK_ARM_SBREL:
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return ELF::R_ARM_MOVT_BREL;
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}
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case ARM::fixup_arm_movw_lo16:
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switch (Modifier) {
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default:
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Ctx.reportError(Fixup.getLoc(), "invalid fixup for ARM MOVW instruction");
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return ELF::R_ARM_NONE;
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case MCSymbolRefExpr::VK_None:
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return ELF::R_ARM_MOVW_ABS_NC;
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case MCSymbolRefExpr::VK_ARM_SBREL:
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return ELF::R_ARM_MOVW_BREL_NC;
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}
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case ARM::fixup_t2_movt_hi16:
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switch (Modifier) {
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default:
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Ctx.reportError(Fixup.getLoc(),
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"invalid fixup for Thumb MOVT instruction");
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return ELF::R_ARM_NONE;
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case MCSymbolRefExpr::VK_None:
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return ELF::R_ARM_THM_MOVT_ABS;
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case MCSymbolRefExpr::VK_ARM_SBREL:
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return ELF::R_ARM_THM_MOVT_BREL;
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}
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case ARM::fixup_t2_movw_lo16:
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switch (Modifier) {
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default:
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Ctx.reportError(Fixup.getLoc(),
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"invalid fixup for Thumb MOVW instruction");
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return ELF::R_ARM_NONE;
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case MCSymbolRefExpr::VK_None:
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return ELF::R_ARM_THM_MOVW_ABS_NC;
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case MCSymbolRefExpr::VK_ARM_SBREL:
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return ELF::R_ARM_THM_MOVW_BREL_NC;
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}
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}
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}
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void ARMELFObjectWriter::addTargetSectionFlags(MCContext &Ctx,
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MCSectionELF &Sec) {
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// The mix of execute-only and non-execute-only at link time is
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// non-execute-only. To avoid the empty implicitly created .text
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// section from making the whole .text section non-execute-only, we
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// mark it execute-only if it is empty and there is at least one
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// execute-only section in the object.
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MCSectionELF *TextSection =
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static_cast<MCSectionELF *>(Ctx.getObjectFileInfo()->getTextSection());
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if (Sec.getKind().isExecuteOnly() && !TextSection->hasInstructions()) {
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for (auto &F : TextSection->getFragmentList())
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if (auto *DF = dyn_cast<MCDataFragment>(&F))
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if (!DF->getContents().empty())
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return;
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TextSection->setFlags(TextSection->getFlags() | ELF::SHF_ARM_PURECODE);
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}
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}
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std::unique_ptr<MCObjectTargetWriter>
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llvm::createARMELFObjectWriter(uint8_t OSABI) {
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return std::make_unique<ARMELFObjectWriter>(OSABI);
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}
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