forked from OSchip/llvm-project
345 lines
11 KiB
C++
345 lines
11 KiB
C++
//===- InputSection.cpp ---------------------------------------------------===//
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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 "InputSection.h"
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#include "ConcatOutputSection.h"
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#include "Config.h"
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#include "InputFiles.h"
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#include "OutputSegment.h"
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#include "Symbols.h"
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#include "SyntheticSections.h"
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#include "Target.h"
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#include "UnwindInfoSection.h"
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#include "Writer.h"
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#include "lld/Common/Memory.h"
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#include "llvm/Support/Endian.h"
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#include "llvm/Support/xxhash.h"
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using namespace llvm;
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using namespace llvm::MachO;
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using namespace llvm::support;
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using namespace lld;
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using namespace lld::macho;
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// Verify ConcatInputSection's size on 64-bit builds. The size of std::vector
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// can differ based on STL debug levels (e.g. iterator debugging on MSVC's STL),
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// so account for that.
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static_assert(sizeof(void *) != 8 || sizeof(ConcatInputSection) ==
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sizeof(std::vector<Reloc>) + 104,
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"Try to minimize ConcatInputSection's size, we create many "
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"instances of it");
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std::vector<ConcatInputSection *> macho::inputSections;
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uint64_t InputSection::getFileSize() const {
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return isZeroFill(getFlags()) ? 0 : getSize();
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}
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uint64_t InputSection::getVA(uint64_t off) const {
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return parent->addr + getOffset(off);
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}
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static uint64_t resolveSymbolVA(const Symbol *sym, uint8_t type) {
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const RelocAttrs &relocAttrs = target->getRelocAttrs(type);
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if (relocAttrs.hasAttr(RelocAttrBits::BRANCH))
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return sym->resolveBranchVA();
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if (relocAttrs.hasAttr(RelocAttrBits::GOT))
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return sym->resolveGotVA();
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if (relocAttrs.hasAttr(RelocAttrBits::TLV))
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return sym->resolveTlvVA();
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return sym->getVA();
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}
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const Defined *InputSection::getContainingSymbol(uint64_t off) const {
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auto *nextSym = llvm::upper_bound(
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symbols, off, [](uint64_t a, const Defined *b) { return a < b->value; });
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if (nextSym == symbols.begin())
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return nullptr;
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return *std::prev(nextSym);
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}
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std::string InputSection::getLocation(uint64_t off) const {
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// First, try to find a symbol that's near the offset. Use it as a reference
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// point.
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if (auto *sym = getContainingSymbol(off))
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return (toString(getFile()) + ":(symbol " + sym->getName() + "+0x" +
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Twine::utohexstr(off - sym->value) + ")")
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.str();
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// If that fails, use the section itself as a reference point.
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for (const Subsection &subsec : section.subsections) {
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if (subsec.isec == this) {
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off += subsec.offset;
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break;
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}
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}
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return (toString(getFile()) + ":(" + getName() + "+0x" +
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Twine::utohexstr(off) + ")")
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.str();
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}
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std::string InputSection::getSourceLocation(uint64_t off) const {
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auto *obj = dyn_cast_or_null<ObjFile>(getFile());
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if (!obj)
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return {};
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DWARFCache *dwarf = obj->getDwarf();
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if (!dwarf)
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return std::string();
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for (const Subsection &subsec : section.subsections) {
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if (subsec.isec == this) {
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off += subsec.offset;
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break;
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}
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}
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auto createMsg = [&](StringRef path, unsigned line) {
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std::string filename = sys::path::filename(path).str();
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std::string lineStr = (":" + Twine(line)).str();
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if (filename == path)
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return filename + lineStr;
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return (filename + lineStr + " (" + path + lineStr + ")").str();
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};
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// First, look up a function for a given offset.
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if (Optional<DILineInfo> li = dwarf->getDILineInfo(
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section.addr + off, object::SectionedAddress::UndefSection))
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return createMsg(li->FileName, li->Line);
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// If it failed, look up again as a variable.
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if (const Defined *sym = getContainingSymbol(off)) {
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// Symbols are generally prefixed with an underscore, which is not included
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// in the debug information.
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StringRef symName = sym->getName();
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if (!symName.empty() && symName[0] == '_')
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symName = symName.substr(1);
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if (Optional<std::pair<std::string, unsigned>> fileLine =
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dwarf->getVariableLoc(symName))
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return createMsg(fileLine->first, fileLine->second);
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}
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// Try to get the source file's name from the DWARF information.
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if (obj->compileUnit)
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return obj->sourceFile();
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return {};
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}
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void ConcatInputSection::foldIdentical(ConcatInputSection *copy) {
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align = std::max(align, copy->align);
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copy->live = false;
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copy->wasCoalesced = true;
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copy->replacement = this;
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for (auto ©Sym : copy->symbols)
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copySym->wasIdenticalCodeFolded = true;
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// Merge the sorted vectors of symbols together.
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auto it = symbols.begin();
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for (auto copyIt = copy->symbols.begin(); copyIt != copy->symbols.end();) {
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if (it == symbols.end()) {
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symbols.push_back(*copyIt++);
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it = symbols.end();
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} else if ((*it)->value > (*copyIt)->value) {
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std::swap(*it++, *copyIt);
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} else {
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++it;
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}
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}
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copy->symbols.clear();
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// Remove duplicate compact unwind info for symbols at the same address.
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if (symbols.empty())
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return;
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it = symbols.begin();
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uint64_t v = (*it)->value;
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for (++it; it != symbols.end(); ++it) {
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Defined *d = *it;
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if (d->value == v)
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d->unwindEntry = nullptr;
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else
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v = d->value;
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}
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}
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void ConcatInputSection::writeTo(uint8_t *buf) {
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assert(!shouldOmitFromOutput());
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if (getFileSize() == 0)
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return;
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memcpy(buf, data.data(), data.size());
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std::vector<uint64_t> relocTargets;
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if (!optimizationHints.empty())
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relocTargets.reserve(relocs.size());
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for (size_t i = 0; i < relocs.size(); i++) {
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const Reloc &r = relocs[i];
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uint8_t *loc = buf + r.offset;
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uint64_t referentVA = 0;
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if (target->hasAttr(r.type, RelocAttrBits::SUBTRAHEND)) {
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const Symbol *fromSym = r.referent.get<Symbol *>();
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const Reloc &minuend = relocs[++i];
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uint64_t minuendVA;
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if (const Symbol *toSym = minuend.referent.dyn_cast<Symbol *>())
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minuendVA = toSym->getVA() + minuend.addend;
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else {
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auto *referentIsec = minuend.referent.get<InputSection *>();
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assert(!::shouldOmitFromOutput(referentIsec));
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minuendVA = referentIsec->getVA(minuend.addend);
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}
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referentVA = minuendVA - fromSym->getVA();
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} else if (auto *referentSym = r.referent.dyn_cast<Symbol *>()) {
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if (target->hasAttr(r.type, RelocAttrBits::LOAD) &&
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!referentSym->isInGot())
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target->relaxGotLoad(loc, r.type);
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referentVA = resolveSymbolVA(referentSym, r.type) + r.addend;
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if (isThreadLocalVariables(getFlags())) {
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// References from thread-local variable sections are treated as offsets
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// relative to the start of the thread-local data memory area, which
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// is initialized via copying all the TLV data sections (which are all
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// contiguous).
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if (isa<Defined>(referentSym))
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referentVA -= firstTLVDataSection->addr;
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}
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} else if (auto *referentIsec = r.referent.dyn_cast<InputSection *>()) {
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assert(!::shouldOmitFromOutput(referentIsec));
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referentVA = referentIsec->getVA(r.addend);
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}
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target->relocateOne(loc, r, referentVA, getVA() + r.offset);
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if (!optimizationHints.empty())
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relocTargets.push_back(referentVA);
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}
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if (!optimizationHints.empty())
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target->applyOptimizationHints(buf, this, relocTargets);
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}
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ConcatInputSection *macho::makeSyntheticInputSection(StringRef segName,
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StringRef sectName,
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uint32_t flags,
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ArrayRef<uint8_t> data,
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uint32_t align) {
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Section §ion =
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*make<Section>(/*file=*/nullptr, segName, sectName, flags, /*addr=*/0);
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auto isec = make<ConcatInputSection>(section, data, align);
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section.subsections.push_back({0, isec});
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return isec;
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}
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void CStringInputSection::splitIntoPieces() {
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size_t off = 0;
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StringRef s = toStringRef(data);
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while (!s.empty()) {
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size_t end = s.find(0);
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if (end == StringRef::npos)
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fatal(getLocation(off) + ": string is not null terminated");
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size_t size = end + 1;
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uint32_t hash = config->dedupLiterals ? xxHash64(s.substr(0, size)) : 0;
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pieces.emplace_back(off, hash);
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s = s.substr(size);
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off += size;
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}
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}
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StringPiece &CStringInputSection::getStringPiece(uint64_t off) {
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if (off >= data.size())
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fatal(toString(this) + ": offset is outside the section");
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auto it =
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partition_point(pieces, [=](StringPiece p) { return p.inSecOff <= off; });
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return it[-1];
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}
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const StringPiece &CStringInputSection::getStringPiece(uint64_t off) const {
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return const_cast<CStringInputSection *>(this)->getStringPiece(off);
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}
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uint64_t CStringInputSection::getOffset(uint64_t off) const {
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const StringPiece &piece = getStringPiece(off);
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uint64_t addend = off - piece.inSecOff;
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return piece.outSecOff + addend;
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}
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WordLiteralInputSection::WordLiteralInputSection(const Section §ion,
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ArrayRef<uint8_t> data,
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uint32_t align)
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: InputSection(WordLiteralKind, section, data, align) {
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switch (sectionType(getFlags())) {
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case S_4BYTE_LITERALS:
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power2LiteralSize = 2;
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break;
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case S_8BYTE_LITERALS:
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power2LiteralSize = 3;
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break;
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case S_16BYTE_LITERALS:
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power2LiteralSize = 4;
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break;
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default:
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llvm_unreachable("invalid literal section type");
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}
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live.resize(data.size() >> power2LiteralSize, !config->deadStrip);
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}
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uint64_t WordLiteralInputSection::getOffset(uint64_t off) const {
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auto *osec = cast<WordLiteralSection>(parent);
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const uintptr_t buf = reinterpret_cast<uintptr_t>(data.data());
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switch (sectionType(getFlags())) {
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case S_4BYTE_LITERALS:
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return osec->getLiteral4Offset(buf + (off & ~3LLU)) | (off & 3);
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case S_8BYTE_LITERALS:
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return osec->getLiteral8Offset(buf + (off & ~7LLU)) | (off & 7);
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case S_16BYTE_LITERALS:
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return osec->getLiteral16Offset(buf + (off & ~15LLU)) | (off & 15);
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default:
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llvm_unreachable("invalid literal section type");
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}
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}
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bool macho::isCodeSection(const InputSection *isec) {
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uint32_t type = sectionType(isec->getFlags());
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if (type != S_REGULAR && type != S_COALESCED)
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return false;
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uint32_t attr = isec->getFlags() & SECTION_ATTRIBUTES_USR;
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if (attr == S_ATTR_PURE_INSTRUCTIONS)
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return true;
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if (isec->getSegName() == segment_names::text)
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return StringSwitch<bool>(isec->getName())
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.Cases(section_names::textCoalNt, section_names::staticInit, true)
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.Default(false);
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return false;
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}
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bool macho::isCfStringSection(const InputSection *isec) {
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return isec->getName() == section_names::cfString &&
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isec->getSegName() == segment_names::data;
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}
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bool macho::isClassRefsSection(const InputSection *isec) {
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return isec->getName() == section_names::objcClassRefs &&
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isec->getSegName() == segment_names::data;
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}
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bool macho::isEhFrameSection(const InputSection *isec) {
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return isec->getName() == section_names::ehFrame &&
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isec->getSegName() == segment_names::text;
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}
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std::string lld::toString(const InputSection *isec) {
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return (toString(isec->getFile()) + ":(" + isec->getName() + ")").str();
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}
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