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llvm-project/lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp
Nick Kledzik 2fcbe822c0 [mach-o] Add support for -sectalign option 
The -sectalign option is used to increase the alignment required for a section.
It required some reworking of how the __TEXT segment is laid out because that
segment also contains the mach_header and load commands. And the size of load
commands depend on the number of segments, sections, and dependent dylibs used.

Using this option will simplify some future test cases because the final
address of code can be pinned down, making tests of its content easier.

llvm-svn: 214268
2014-07-30 00:58:06 +00:00

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//===- lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp ------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// \file Converts from in-memory Atoms to in-memory normalized mach-o.
///
/// +------------+
/// | normalized |
/// +------------+
/// ^
/// |
/// |
/// +-------+
/// | Atoms |
/// +-------+
#include "MachONormalizedFile.h"
#include "ArchHandler.h"
#include "MachONormalizedFileBinaryUtils.h"
#include "lld/Core/Error.h"
#include "lld/Core/LLVM.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/MachO.h"
#include <map>
#include <system_error>
using llvm::StringRef;
using llvm::isa;
using namespace llvm::MachO;
using namespace lld::mach_o::normalized;
using namespace lld;
namespace {
struct AtomInfo {
const DefinedAtom *atom;
uint64_t offsetInSection;
};
struct SectionInfo {
SectionInfo(StringRef seg, StringRef sect, SectionType type,
const MachOLinkingContext &ctxt, uint32_t attr=0);
StringRef segmentName;
StringRef sectionName;
SectionType type;
uint32_t attributes;
uint64_t address;
uint64_t size;
uint32_t alignment;
std::vector<AtomInfo> atomsAndOffsets;
uint32_t normalizedSectionIndex;
uint32_t finalSectionIndex;
};
SectionInfo::SectionInfo(StringRef sg, StringRef sct, SectionType t,
const MachOLinkingContext &ctxt, uint32_t attrs)
: segmentName(sg), sectionName(sct), type(t), attributes(attrs),
address(0), size(0), alignment(0),
normalizedSectionIndex(0), finalSectionIndex(0) {
uint8_t align;
if (ctxt.sectionAligned(segmentName, sectionName, align)) {
alignment = align;
}
}
struct SegmentInfo {
SegmentInfo(StringRef name);
StringRef name;
uint64_t address;
uint64_t size;
uint32_t access;
std::vector<SectionInfo*> sections;
uint32_t normalizedSegmentIndex;
};
SegmentInfo::SegmentInfo(StringRef n)
: name(n), address(0), size(0), access(0), normalizedSegmentIndex(0) {
}
class Util {
public:
Util(const MachOLinkingContext &ctxt) : _context(ctxt),
_archHandler(ctxt.archHandler()), _entryAtom(nullptr) {}
void assignAtomsToSections(const lld::File &atomFile);
void organizeSections();
void assignAddressesToSections(const NormalizedFile &file);
uint32_t fileFlags();
void copySegmentInfo(NormalizedFile &file);
void copySectionInfo(NormalizedFile &file);
void updateSectionInfo(NormalizedFile &file);
void buildAtomToAddressMap();
void addSymbols(const lld::File &atomFile, NormalizedFile &file);
void addIndirectSymbols(const lld::File &atomFile, NormalizedFile &file);
void addRebaseAndBindingInfo(const lld::File &, NormalizedFile &file);
void addSectionRelocs(const lld::File &, NormalizedFile &file);
void buildDataInCodeArray(const lld::File &, NormalizedFile &file);
void addDependentDylibs(const lld::File &, NormalizedFile &file);
void copyEntryPointAddress(NormalizedFile &file);
void copySectionContent(NormalizedFile &file);
private:
typedef std::map<DefinedAtom::ContentType, SectionInfo*> TypeToSection;
typedef llvm::DenseMap<const Atom*, uint64_t> AtomToAddress;
struct DylibInfo { int ordinal; bool hasWeak; bool hasNonWeak; };
typedef llvm::StringMap<DylibInfo> DylibPathToInfo;
SectionInfo *sectionForAtom(const DefinedAtom*);
SectionInfo *getRelocatableSection(DefinedAtom::ContentType type);
SectionInfo *getFinalSection(DefinedAtom::ContentType type);
void appendAtom(SectionInfo *sect, const DefinedAtom *atom);
SegmentInfo *segmentForName(StringRef segName);
void layoutSectionsInSegment(SegmentInfo *seg, uint64_t &addr);
void layoutSectionsInTextSegment(size_t, SegmentInfo *, uint64_t &);
void copySectionContent(SectionInfo *si, ContentBytes &content);
uint8_t scopeBits(const DefinedAtom* atom);
uint16_t descBits(const DefinedAtom* atom);
int dylibOrdinal(const SharedLibraryAtom *sa);
void segIndexForSection(const SectionInfo *sect,
uint8_t &segmentIndex, uint64_t &segmentStartAddr);
const Atom *targetOfLazyPointer(const DefinedAtom *lpAtom);
const Atom *targetOfStub(const DefinedAtom *stubAtom);
bool belongsInGlobalSymbolsSection(const DefinedAtom* atom);
void appendSection(SectionInfo *si, NormalizedFile &file);
uint32_t sectionIndexForAtom(const Atom *atom);
static uint64_t alignTo(uint64_t value, uint8_t align2);
typedef llvm::DenseMap<const Atom*, uint32_t> AtomToIndex;
struct AtomAndIndex { const Atom *atom; uint32_t index; };
struct AtomSorter {
bool operator()(const AtomAndIndex &left, const AtomAndIndex &right);
};
struct SegmentSorter {
bool operator()(const SegmentInfo *left, const SegmentInfo *right);
static unsigned weight(const SegmentInfo *);
};
struct TextSectionSorter {
bool operator()(const SectionInfo *left, const SectionInfo *right);
static unsigned weight(const SectionInfo *);
};
const MachOLinkingContext &_context;
mach_o::ArchHandler &_archHandler;
llvm::BumpPtrAllocator _allocator;
std::vector<SectionInfo*> _sectionInfos;
std::vector<SegmentInfo*> _segmentInfos;
TypeToSection _sectionMap;
std::vector<SectionInfo*> _customSections;
AtomToAddress _atomToAddress;
DylibPathToInfo _dylibInfo;
const DefinedAtom *_entryAtom;
AtomToIndex _atomToSymbolIndex;
};
SectionInfo *Util::getRelocatableSection(DefinedAtom::ContentType type) {
StringRef segmentName;
StringRef sectionName;
SectionType sectionType;
SectionAttr sectionAttrs;
// Use same table used by when parsing .o files.
relocatableSectionInfoForContentType(type, segmentName, sectionName,
sectionType, sectionAttrs);
// If we already have a SectionInfo with this name, re-use it.
// This can happen if two ContentType map to the same mach-o section.
for (auto sect : _sectionMap) {
if (sect.second->sectionName.equals(sectionName) &&
sect.second->segmentName.equals(segmentName)) {
return sect.second;
}
}
// Otherwise allocate new SectionInfo object.
SectionInfo *sect = new (_allocator) SectionInfo(segmentName, sectionName,
sectionType, _context,
sectionAttrs);
_sectionInfos.push_back(sect);
_sectionMap[type] = sect;
return sect;
}
#define ENTRY(seg, sect, type, atomType) \
{seg, sect, type, DefinedAtom::atomType }
struct MachOFinalSectionFromAtomType {
StringRef segmentName;
StringRef sectionName;
SectionType sectionType;
DefinedAtom::ContentType atomType;
};
const MachOFinalSectionFromAtomType sectsToAtomType[] = {
ENTRY("__TEXT", "__text", S_REGULAR, typeCode),
ENTRY("__TEXT", "__cstring", S_CSTRING_LITERALS, typeCString),
ENTRY("__TEXT", "__ustring", S_REGULAR, typeUTF16String),
ENTRY("__TEXT", "__const", S_REGULAR, typeConstant),
ENTRY("__TEXT", "__const", S_4BYTE_LITERALS, typeLiteral4),
ENTRY("__TEXT", "__const", S_8BYTE_LITERALS, typeLiteral8),
ENTRY("__TEXT", "__const", S_16BYTE_LITERALS, typeLiteral16),
ENTRY("__TEXT", "__stubs", S_SYMBOL_STUBS, typeStub),
ENTRY("__TEXT", "__stub_helper", S_REGULAR, typeStubHelper),
ENTRY("__TEXT", "__gcc_except_tab", S_REGULAR, typeLSDA),
ENTRY("__TEXT", "__eh_frame", S_COALESCED, typeCFI),
ENTRY("__DATA", "__data", S_REGULAR, typeData),
ENTRY("__DATA", "__const", S_REGULAR, typeConstData),
ENTRY("__DATA", "__cfstring", S_REGULAR, typeCFString),
ENTRY("__DATA", "__la_symbol_ptr", S_LAZY_SYMBOL_POINTERS,
typeLazyPointer),
ENTRY("__DATA", "__mod_init_func", S_MOD_INIT_FUNC_POINTERS,
typeInitializerPtr),
ENTRY("__DATA", "__mod_term_func", S_MOD_TERM_FUNC_POINTERS,
typeTerminatorPtr),
ENTRY("__DATA", "___got", S_NON_LAZY_SYMBOL_POINTERS,
typeGOT),
ENTRY("__DATA", "___bss", S_ZEROFILL, typeZeroFill),
// FIXME: __compact_unwind actually needs to be processed by a pass and put
// into __TEXT,__unwind_info. For now, forwarding it back to
// __LD,__compact_unwind is harmless (it's ignored by the unwinder, which then
// proceeds to process __TEXT,__eh_frame for its instructions).
ENTRY("__LD", "__compact_unwind", S_REGULAR, typeCompactUnwindInfo),
};
#undef ENTRY
SectionInfo *Util::getFinalSection(DefinedAtom::ContentType atomType) {
for (auto &p : sectsToAtomType) {
if (p.atomType != atomType)
continue;
SectionAttr sectionAttrs = 0;
switch (atomType) {
case DefinedAtom::typeCode:
case DefinedAtom::typeStub:
sectionAttrs = S_ATTR_PURE_INSTRUCTIONS;
break;
default:
break;
}
// If we already have a SectionInfo with this name, re-use it.
// This can happen if two ContentType map to the same mach-o section.
for (auto sect : _sectionMap) {
if (sect.second->sectionName.equals(p.sectionName) &&
sect.second->segmentName.equals(p.segmentName)) {
return sect.second;
}
}
// Otherwise allocate new SectionInfo object.
SectionInfo *sect = new (_allocator) SectionInfo(p.segmentName,
p.sectionName,
p.sectionType,
_context,
sectionAttrs);
_sectionInfos.push_back(sect);
_sectionMap[atomType] = sect;
return sect;
}
llvm_unreachable("content type not yet supported");
}
SectionInfo *Util::sectionForAtom(const DefinedAtom *atom) {
if (atom->sectionChoice() == DefinedAtom::sectionBasedOnContent) {
// Section for this atom is derived from content type.
DefinedAtom::ContentType type = atom->contentType();
auto pos = _sectionMap.find(type);
if ( pos != _sectionMap.end() )
return pos->second;
bool rMode = (_context.outputMachOType() == llvm::MachO::MH_OBJECT);
return rMode ? getRelocatableSection(type) : getFinalSection(type);
} else {
// This atom needs to be in a custom section.
StringRef customName = atom->customSectionName();
// Look to see if we have already allocated the needed custom section.
for(SectionInfo *sect : _customSections) {
const DefinedAtom *firstAtom = sect->atomsAndOffsets.front().atom;
if (firstAtom->customSectionName().equals(customName)) {
return sect;
}
}
// Not found, so need to create a new custom section.
size_t seperatorIndex = customName.find('/');
assert(seperatorIndex != StringRef::npos);
StringRef segName = customName.slice(0, seperatorIndex);
StringRef sectName = customName.drop_front(seperatorIndex + 1);
SectionInfo *sect = new (_allocator) SectionInfo(segName, sectName,
S_REGULAR, _context);
_customSections.push_back(sect);
_sectionInfos.push_back(sect);
return sect;
}
}
void Util::appendAtom(SectionInfo *sect, const DefinedAtom *atom) {
// Figure out offset for atom in this section given alignment constraints.
uint64_t offset = sect->size;
DefinedAtom::Alignment atomAlign = atom->alignment();
uint64_t align2 = 1 << atomAlign.powerOf2;
uint64_t requiredModulus = atomAlign.modulus;
uint64_t currentModulus = (offset % align2);
if ( currentModulus != requiredModulus ) {
if ( requiredModulus > currentModulus )
offset += requiredModulus-currentModulus;
else
offset += align2+requiredModulus-currentModulus;
}
// Record max alignment of any atom in this section.
if ( atomAlign.powerOf2 > sect->alignment )
sect->alignment = atomAlign.powerOf2;
// Assign atom to this section with this offset.
AtomInfo ai = {atom, offset};
sect->atomsAndOffsets.push_back(ai);
// Update section size to include this atom.
sect->size = offset + atom->size();
}
void Util::assignAtomsToSections(const lld::File &atomFile) {
for (const DefinedAtom *atom : atomFile.defined()) {
appendAtom(sectionForAtom(atom), atom);
}
}
SegmentInfo *Util::segmentForName(StringRef segName) {
for (SegmentInfo *si : _segmentInfos) {
if ( si->name.equals(segName) )
return si;
}
SegmentInfo *info = new (_allocator) SegmentInfo(segName);
if (segName.equals("__TEXT"))
info->access = VM_PROT_READ | VM_PROT_EXECUTE;
else if (segName.equals("__DATA"))
info->access = VM_PROT_READ | VM_PROT_WRITE;
else if (segName.equals("__PAGEZERO"))
info->access = 0;
_segmentInfos.push_back(info);
return info;
}
unsigned Util::SegmentSorter::weight(const SegmentInfo *seg) {
return llvm::StringSwitch<unsigned>(seg->name)
.Case("__PAGEZERO", 1)
.Case("__TEXT", 2)
.Case("__DATA", 3)
.Default(100);
}
bool Util::SegmentSorter::operator()(const SegmentInfo *left,
const SegmentInfo *right) {
return (weight(left) < weight(right));
}
unsigned Util::TextSectionSorter::weight(const SectionInfo *sect) {
return llvm::StringSwitch<unsigned>(sect->sectionName)
.Case("__text", 1)
.Case("__stubs", 2)
.Case("__stub_helper", 3)
.Case("__const", 4)
.Case("__cstring", 5)
.Case("__unwind_info", 98)
.Case("__eh_frame", 99)
.Default(10);
}
bool Util::TextSectionSorter::operator()(const SectionInfo *left,
const SectionInfo *right) {
return (weight(left) < weight(right));
}
void Util::organizeSections() {
if (_context.outputMachOType() == llvm::MachO::MH_OBJECT) {
// Leave sections ordered as normalized file specified.
uint32_t sectionIndex = 1;
for (SectionInfo *si : _sectionInfos) {
si->finalSectionIndex = sectionIndex++;
}
} else {
// Main executables, need a zero-page segment
if (_context.outputMachOType() == llvm::MachO::MH_EXECUTE)
segmentForName("__PAGEZERO");
// Group sections into segments.
for (SectionInfo *si : _sectionInfos) {
SegmentInfo *seg = segmentForName(si->segmentName);
seg->sections.push_back(si);
}
// Sort segments.
std::sort(_segmentInfos.begin(), _segmentInfos.end(), SegmentSorter());
// Sort sections within segments.
for (SegmentInfo *seg : _segmentInfos) {
if (seg->name.equals("__TEXT")) {
std::sort(seg->sections.begin(), seg->sections.end(),
TextSectionSorter());
}
}
// Record final section indexes.
uint32_t segmentIndex = 0;
uint32_t sectionIndex = 1;
for (SegmentInfo *seg : _segmentInfos) {
seg->normalizedSegmentIndex = segmentIndex++;
for (SectionInfo *sect : seg->sections) {
sect->finalSectionIndex = sectionIndex++;
}
}
}
}
uint64_t Util::alignTo(uint64_t value, uint8_t align2) {
return llvm::RoundUpToAlignment(value, 1 << align2);
}
void Util::layoutSectionsInSegment(SegmentInfo *seg, uint64_t &addr) {
seg->address = addr;
for (SectionInfo *sect : seg->sections) {
sect->address = alignTo(addr, sect->alignment);
addr += sect->size;
}
seg->size = llvm::RoundUpToAlignment(addr - seg->address,_context.pageSize());
}
// __TEXT segment lays out backwards so padding is at front after load commands.
void Util::layoutSectionsInTextSegment(size_t hlcSize, SegmentInfo *seg,
uint64_t &addr) {
seg->address = addr;
// Walks sections starting at end to calculate padding for start.
int64_t taddr = 0;
for (auto it = seg->sections.rbegin(); it != seg->sections.rend(); ++it) {
SectionInfo *sect = *it;
taddr -= sect->size;
taddr = taddr & (0 - (1 << sect->alignment));
}
int64_t padding = taddr - hlcSize;
while (padding < 0)
padding += _context.pageSize();
// Start assigning section address starting at padded offset.
addr += (padding + hlcSize);
for (SectionInfo *sect : seg->sections) {
sect->address = alignTo(addr, sect->alignment);
addr = sect->address + sect->size;
}
seg->size = llvm::RoundUpToAlignment(addr - seg->address,_context.pageSize());
}
void Util::assignAddressesToSections(const NormalizedFile &file) {
size_t hlcSize = headerAndLoadCommandsSize(file);
uint64_t address = 0; // FIXME
if (_context.outputMachOType() != llvm::MachO::MH_OBJECT) {
for (SegmentInfo *seg : _segmentInfos) {
if (seg->name.equals("__PAGEZERO")) {
seg->size = _context.pageZeroSize();
address += seg->size;
}
else if (seg->name.equals("__TEXT"))
layoutSectionsInTextSegment(hlcSize, seg, address);
else
layoutSectionsInSegment(seg, address);
address = llvm::RoundUpToAlignment(address, _context.pageSize());
}
DEBUG_WITH_TYPE("WriterMachO-norm",
llvm::dbgs() << "assignAddressesToSections()\n";
for (SegmentInfo *sgi : _segmentInfos) {
llvm::dbgs() << " address=" << llvm::format("0x%08llX", sgi->address)
<< ", size=" << llvm::format("0x%08llX", sgi->size)
<< ", segment-name='" << sgi->name
<< "'\n";
for (SectionInfo *si : sgi->sections) {
llvm::dbgs()<< " addr=" << llvm::format("0x%08llX", si->address)
<< ", size=" << llvm::format("0x%08llX", si->size)
<< ", section-name='" << si->sectionName
<< "\n";
}
}
);
} else {
for (SectionInfo *sect : _sectionInfos) {
sect->address = alignTo(address, sect->alignment);
address = sect->address + sect->size;
}
DEBUG_WITH_TYPE("WriterMachO-norm",
llvm::dbgs() << "assignAddressesToSections()\n";
for (SectionInfo *si : _sectionInfos) {
llvm::dbgs() << " section=" << si->sectionName
<< " address= " << llvm::format("0x%08X", si->address)
<< " size= " << llvm::format("0x%08X", si->size)
<< "\n";
}
);
}
}
void Util::copySegmentInfo(NormalizedFile &file) {
for (SegmentInfo *sgi : _segmentInfos) {
Segment seg;
seg.name = sgi->name;
seg.address = sgi->address;
seg.size = sgi->size;
seg.access = sgi->access;
file.segments.push_back(seg);
}
}
void Util::appendSection(SectionInfo *si, NormalizedFile &file) {
// Add new empty section to end of file.sections.
Section temp;
file.sections.push_back(std::move(temp));
Section* normSect = &file.sections.back();
// Copy fields to normalized section.
normSect->segmentName = si->segmentName;
normSect->sectionName = si->sectionName;
normSect->type = si->type;
normSect->attributes = si->attributes;
normSect->address = si->address;
normSect->alignment = si->alignment;
// Record where normalized section is.
si->normalizedSectionIndex = file.sections.size()-1;
}
void Util::copySectionContent(NormalizedFile &file) {
const bool r = (_context.outputMachOType() == llvm::MachO::MH_OBJECT);
// Utility function for ArchHandler to find address of atom in output file.
auto addrForAtom = [&] (const Atom &atom) -> uint64_t {
auto pos = _atomToAddress.find(&atom);
assert(pos != _atomToAddress.end());
return pos->second;
};
for (SectionInfo *si : _sectionInfos) {
if (si->type == llvm::MachO::S_ZEROFILL)
continue;
// Copy content from atoms to content buffer for section.
uint8_t *sectionContent = file.ownedAllocations.Allocate<uint8_t>(si->size);
Section *normSect = &file.sections[si->normalizedSectionIndex];
normSect->content = llvm::makeArrayRef(sectionContent, si->size);
for (AtomInfo &ai : si->atomsAndOffsets) {
uint8_t *atomContent = reinterpret_cast<uint8_t*>
(&sectionContent[ai.offsetInSection]);
_archHandler.generateAtomContent(*ai.atom, r, addrForAtom, atomContent);
}
}
}
void Util::copySectionInfo(NormalizedFile &file) {
file.sections.reserve(_sectionInfos.size());
// For final linked images, write sections grouped by segment.
if (_context.outputMachOType() != llvm::MachO::MH_OBJECT) {
for (SegmentInfo *sgi : _segmentInfos) {
for (SectionInfo *si : sgi->sections) {
appendSection(si, file);
}
}
} else {
// Object files write sections in default order.
for (SectionInfo *si : _sectionInfos) {
appendSection(si, file);
}
}
}
void Util::updateSectionInfo(NormalizedFile &file) {
file.sections.reserve(_sectionInfos.size());
if (_context.outputMachOType() != llvm::MachO::MH_OBJECT) {
// For final linked images, sections grouped by segment.
for (SegmentInfo *sgi : _segmentInfos) {
Segment *normSeg = &file.segments[sgi->normalizedSegmentIndex];
normSeg->address = sgi->address;
normSeg->size = sgi->size;
for (SectionInfo *si : sgi->sections) {
Section *normSect = &file.sections[si->normalizedSectionIndex];
normSect->address = si->address;
}
}
} else {
// Object files write sections in default order.
for (SectionInfo *si : _sectionInfos) {
Section *normSect = &file.sections[si->normalizedSectionIndex];
normSect->address = si->address;
}
}
}
void Util::copyEntryPointAddress(NormalizedFile &nFile) {
if (_context.outputTypeHasEntry()) {
if (_archHandler.isThumbFunction(*_entryAtom))
nFile.entryAddress = (_atomToAddress[_entryAtom] | 1);
else
nFile.entryAddress = _atomToAddress[_entryAtom];
}
}
void Util::buildAtomToAddressMap() {
DEBUG_WITH_TYPE("WriterMachO-address", llvm::dbgs()
<< "assign atom addresses:\n");
const bool lookForEntry = _context.outputTypeHasEntry();
for (SectionInfo *sect : _sectionInfos) {
for (const AtomInfo &info : sect->atomsAndOffsets) {
_atomToAddress[info.atom] = sect->address + info.offsetInSection;
if (lookForEntry && (info.atom->contentType() == DefinedAtom::typeCode) &&
(info.atom->size() != 0) &&
info.atom->name() == _context.entrySymbolName()) {
_entryAtom = info.atom;
}
DEBUG_WITH_TYPE("WriterMachO-address", llvm::dbgs()
<< " address="
<< llvm::format("0x%016X", _atomToAddress[info.atom])
<< " atom=" << info.atom
<< " name=" << info.atom->name() << "\n");
}
}
}
uint8_t Util::scopeBits(const DefinedAtom* atom) {
switch (atom->scope()) {
case Atom::scopeTranslationUnit:
return 0;
case Atom::scopeLinkageUnit:
return N_PEXT | N_EXT;
case Atom::scopeGlobal:
return N_EXT;
}
llvm_unreachable("Unknown scope");
}
uint16_t Util::descBits(const DefinedAtom* atom) {
uint16_t desc = 0;
switch (atom->merge()) {
case lld::DefinedAtom::mergeNo:
case lld::DefinedAtom::mergeAsTentative:
break;
case lld::DefinedAtom::mergeAsWeak:
case lld::DefinedAtom::mergeAsWeakAndAddressUsed:
desc |= N_WEAK_DEF;
break;
case lld::DefinedAtom::mergeSameNameAndSize:
case lld::DefinedAtom::mergeByLargestSection:
case lld::DefinedAtom::mergeByContent:
llvm_unreachable("Unsupported DefinedAtom::merge()");
break;
}
if (atom->contentType() == lld::DefinedAtom::typeResolver)
desc |= N_SYMBOL_RESOLVER;
if (_archHandler.isThumbFunction(*atom))
desc |= N_ARM_THUMB_DEF;
return desc;
}
bool Util::AtomSorter::operator()(const AtomAndIndex &left,
const AtomAndIndex &right) {
return (left.atom->name().compare(right.atom->name()) < 0);
}
bool Util::belongsInGlobalSymbolsSection(const DefinedAtom* atom) {
// ScopeLinkageUnit symbols are in globals area of symbol table
// in object files, but in locals area for final linked images.
if (_context.outputMachOType() == llvm::MachO::MH_OBJECT)
return (atom->scope() != Atom::scopeTranslationUnit);
else
return (atom->scope() == Atom::scopeGlobal);
}
void Util::addSymbols(const lld::File &atomFile, NormalizedFile &file) {
bool rMode = (_context.outputMachOType() == llvm::MachO::MH_OBJECT);
// Mach-O symbol table has three regions: locals, globals, undefs.
// Add all local (non-global) symbols in address order
std::vector<AtomAndIndex> globals;
globals.reserve(512);
for (SectionInfo *sect : _sectionInfos) {
for (const AtomInfo &info : sect->atomsAndOffsets) {
const DefinedAtom *atom = info.atom;
if (!atom->name().empty()) {
if (belongsInGlobalSymbolsSection(atom)) {
AtomAndIndex ai = { atom, sect->finalSectionIndex };
globals.push_back(ai);
} else {
Symbol sym;
sym.name = atom->name();
sym.type = N_SECT;
sym.scope = scopeBits(atom);
sym.sect = sect->finalSectionIndex;
sym.desc = descBits(atom);
sym.value = _atomToAddress[atom];
_atomToSymbolIndex[atom] = file.localSymbols.size();
file.localSymbols.push_back(sym);
}
} else if (rMode && _archHandler.needsLocalSymbolInRelocatableFile(atom)){
// Create 'Lxxx' labels for anonymous atoms if archHandler says so.
static unsigned tempNum = 1;
char tmpName[16];
sprintf(tmpName, "L%04u", tempNum++);
StringRef tempRef(tmpName);
Symbol sym;
sym.name = tempRef.copy(file.ownedAllocations);
sym.type = N_SECT;
sym.scope = 0;
sym.sect = sect->finalSectionIndex;
sym.desc = 0;
sym.value = _atomToAddress[atom];
_atomToSymbolIndex[atom] = file.localSymbols.size();
file.localSymbols.push_back(sym);
}
}
}
// Sort global symbol alphabetically, then add to symbol table.
std::sort(globals.begin(), globals.end(), AtomSorter());
const uint32_t globalStartIndex = file.localSymbols.size();
for (AtomAndIndex &ai : globals) {
Symbol sym;
sym.name = ai.atom->name();
sym.type = N_SECT;
sym.scope = scopeBits(static_cast<const DefinedAtom*>(ai.atom));
sym.sect = ai.index;
sym.desc = descBits(static_cast<const DefinedAtom*>(ai.atom));
sym.value = _atomToAddress[ai.atom];
_atomToSymbolIndex[ai.atom] = globalStartIndex + file.globalSymbols.size();
file.globalSymbols.push_back(sym);
}
// Sort undefined symbol alphabetically, then add to symbol table.
std::vector<AtomAndIndex> undefs;
undefs.reserve(128);
for (const UndefinedAtom *atom : atomFile.undefined()) {
AtomAndIndex ai = { atom, 0 };
undefs.push_back(ai);
}
for (const SharedLibraryAtom *atom : atomFile.sharedLibrary()) {
AtomAndIndex ai = { atom, 0 };
undefs.push_back(ai);
}
std::sort(undefs.begin(), undefs.end(), AtomSorter());
const uint32_t start = file.globalSymbols.size() + file.localSymbols.size();
for (AtomAndIndex &ai : undefs) {
Symbol sym;
sym.name = ai.atom->name();
sym.type = N_UNDF;
sym.scope = N_EXT;
sym.sect = 0;
sym.desc = 0;
sym.value = 0;
_atomToSymbolIndex[ai.atom] = file.undefinedSymbols.size() + start;
file.undefinedSymbols.push_back(sym);
}
}
const Atom *Util::targetOfLazyPointer(const DefinedAtom *lpAtom) {
for (const Reference *ref : *lpAtom) {
if (_archHandler.isLazyPointer(*ref)) {
return ref->target();
}
}
return nullptr;
}
const Atom *Util::targetOfStub(const DefinedAtom *stubAtom) {
for (const Reference *ref : *stubAtom) {
if (const Atom *ta = ref->target()) {
if (const DefinedAtom *lpAtom = dyn_cast<DefinedAtom>(ta)) {
const Atom *target = targetOfLazyPointer(lpAtom);
if (target)
return target;
}
}
}
return nullptr;
}
void Util::addIndirectSymbols(const lld::File &atomFile, NormalizedFile &file) {
for (SectionInfo *si : _sectionInfos) {
Section &normSect = file.sections[si->normalizedSectionIndex];
switch (si->type) {
case llvm::MachO::S_NON_LAZY_SYMBOL_POINTERS:
for (const AtomInfo &info : si->atomsAndOffsets) {
bool foundTarget = false;
for (const Reference *ref : *info.atom) {
const Atom *target = ref->target();
if (target) {
if (isa<const SharedLibraryAtom>(target)) {
uint32_t index = _atomToSymbolIndex[target];
normSect.indirectSymbols.push_back(index);
foundTarget = true;
} else {
normSect.indirectSymbols.push_back(
llvm::MachO::INDIRECT_SYMBOL_LOCAL);
}
}
}
if (!foundTarget) {
normSect.indirectSymbols.push_back(
llvm::MachO::INDIRECT_SYMBOL_ABS);
}
}
break;
case llvm::MachO::S_LAZY_SYMBOL_POINTERS:
for (const AtomInfo &info : si->atomsAndOffsets) {
const Atom *target = targetOfLazyPointer(info.atom);
if (target) {
uint32_t index = _atomToSymbolIndex[target];
normSect.indirectSymbols.push_back(index);
}
}
break;
case llvm::MachO::S_SYMBOL_STUBS:
for (const AtomInfo &info : si->atomsAndOffsets) {
const Atom *target = targetOfStub(info.atom);
if (target) {
uint32_t index = _atomToSymbolIndex[target];
normSect.indirectSymbols.push_back(index);
}
}
break;
default:
break;
}
}
}
void Util::addDependentDylibs(const lld::File &atomFile,NormalizedFile &nFile) {
// Scan all imported symbols and build up list of dylibs they are from.
int ordinal = 1;
for (const SharedLibraryAtom *slAtom : atomFile.sharedLibrary()) {
StringRef loadPath = slAtom->loadName();
DylibPathToInfo::iterator pos = _dylibInfo.find(loadPath);
if (pos == _dylibInfo.end()) {
DylibInfo info;
info.ordinal = ordinal++;
info.hasWeak = slAtom->canBeNullAtRuntime();
info.hasNonWeak = !info.hasWeak;
_dylibInfo[loadPath] = info;
DependentDylib depInfo;
depInfo.path = loadPath;
depInfo.kind = llvm::MachO::LC_LOAD_DYLIB;
nFile.dependentDylibs.push_back(depInfo);
} else {
if ( slAtom->canBeNullAtRuntime() )
pos->second.hasWeak = true;
else
pos->second.hasNonWeak = true;
}
}
// Automatically weak link dylib in which all symbols are weak (canBeNull).
for (DependentDylib &dep : nFile.dependentDylibs) {
DylibInfo &info = _dylibInfo[dep.path];
if (info.hasWeak && !info.hasNonWeak)
dep.kind = llvm::MachO::LC_LOAD_WEAK_DYLIB;
}
}
int Util::dylibOrdinal(const SharedLibraryAtom *sa) {
return _dylibInfo[sa->loadName()].ordinal;
}
void Util::segIndexForSection(const SectionInfo *sect, uint8_t &segmentIndex,
uint64_t &segmentStartAddr) {
segmentIndex = 0;
for (const SegmentInfo *seg : _segmentInfos) {
if ((seg->address <= sect->address)
&& (seg->address+seg->size >= sect->address+sect->size)) {
segmentStartAddr = seg->address;
return;
}
++segmentIndex;
}
llvm_unreachable("section not in any segment");
}
uint32_t Util::sectionIndexForAtom(const Atom *atom) {
uint64_t address = _atomToAddress[atom];
uint32_t index = 1;
for (const SectionInfo *si : _sectionInfos) {
if ((si->address <= address) && (address < si->address+si->size))
return index;
++index;
}
llvm_unreachable("atom not in any section");
}
void Util::addSectionRelocs(const lld::File &, NormalizedFile &file) {
if (_context.outputMachOType() != llvm::MachO::MH_OBJECT)
return;
// Utility function for ArchHandler to find symbol index for an atom.
auto symIndexForAtom = [&] (const Atom &atom) -> uint32_t {
auto pos = _atomToSymbolIndex.find(&atom);
assert(pos != _atomToSymbolIndex.end());
return pos->second;
};
// Utility function for ArchHandler to find section index for an atom.
auto sectIndexForAtom = [&] (const Atom &atom) -> uint32_t {
return sectionIndexForAtom(&atom);
};
// Utility function for ArchHandler to find address of atom in output file.
auto addressForAtom = [&] (const Atom &atom) -> uint64_t {
auto pos = _atomToAddress.find(&atom);
assert(pos != _atomToAddress.end());
return pos->second;
};
for (SectionInfo *si : _sectionInfos) {
Section &normSect = file.sections[si->normalizedSectionIndex];
for (const AtomInfo &info : si->atomsAndOffsets) {
const DefinedAtom *atom = info.atom;
for (const Reference *ref : *atom) {
_archHandler.appendSectionRelocations(*atom, info.offsetInSection, *ref,
symIndexForAtom,
sectIndexForAtom,
addressForAtom,
normSect.relocations);
}
}
}
}
void Util::buildDataInCodeArray(const lld::File &, NormalizedFile &file) {
for (SectionInfo *si : _sectionInfos) {
for (const AtomInfo &info : si->atomsAndOffsets) {
// Atoms that contain data-in-code have "transition" references
// which mark a point where the embedded data starts of ends.
// This needs to be converted to the mach-o format which is an array
// of data-in-code ranges.
uint32_t startOffset = 0;
DataRegionType mode = DataRegionType(0);
for (const Reference *ref : *info.atom) {
if (ref->kindNamespace() != Reference::KindNamespace::mach_o)
continue;
if (_archHandler.isDataInCodeTransition(ref->kindValue())) {
DataRegionType nextMode = (DataRegionType)ref->addend();
if (mode != nextMode) {
if (mode != 0) {
// Found end data range, so make range entry.
DataInCode entry;
entry.offset = si->address + info.offsetInSection + startOffset;
entry.length = ref->offsetInAtom() - startOffset;
entry.kind = mode;
file.dataInCode.push_back(entry);
}
}
mode = nextMode;
startOffset = ref->offsetInAtom();
}
}
if (mode != 0) {
// Function ends with data (no end transition).
DataInCode entry;
entry.offset = si->address + info.offsetInSection + startOffset;
entry.length = info.atom->size() - startOffset;
entry.kind = mode;
file.dataInCode.push_back(entry);
}
}
}
}
void Util::addRebaseAndBindingInfo(const lld::File &atomFile,
NormalizedFile &nFile) {
if (_context.outputMachOType() == llvm::MachO::MH_OBJECT)
return;
uint8_t segmentIndex;
uint64_t segmentStartAddr;
for (SectionInfo *sect : _sectionInfos) {
segIndexForSection(sect, segmentIndex, segmentStartAddr);
for (const AtomInfo &info : sect->atomsAndOffsets) {
const DefinedAtom *atom = info.atom;
for (const Reference *ref : *atom) {
uint64_t segmentOffset = _atomToAddress[atom] + ref->offsetInAtom()
- segmentStartAddr;
const Atom* targ = ref->target();
if (_archHandler.isPointer(*ref)) {
// A pointer to a DefinedAtom requires rebasing.
if (dyn_cast<DefinedAtom>(targ)) {
RebaseLocation rebase;
rebase.segIndex = segmentIndex;
rebase.segOffset = segmentOffset;
rebase.kind = llvm::MachO::REBASE_TYPE_POINTER;
nFile.rebasingInfo.push_back(rebase);
}
// A pointer to an SharedLibraryAtom requires binding.
if (const SharedLibraryAtom *sa = dyn_cast<SharedLibraryAtom>(targ)) {
BindLocation bind;
bind.segIndex = segmentIndex;
bind.segOffset = segmentOffset;
bind.kind = llvm::MachO::BIND_TYPE_POINTER;
bind.canBeNull = sa->canBeNullAtRuntime();
bind.ordinal = dylibOrdinal(sa);
bind.symbolName = targ->name();
bind.addend = ref->addend();
nFile.bindingInfo.push_back(bind);
}
}
if (_archHandler.isLazyPointer(*ref)) {
BindLocation bind;
bind.segIndex = segmentIndex;
bind.segOffset = segmentOffset;
bind.kind = llvm::MachO::BIND_TYPE_POINTER;
bind.canBeNull = false; //sa->canBeNullAtRuntime();
bind.ordinal = 1; // FIXME
bind.symbolName = targ->name();
bind.addend = ref->addend();
nFile.lazyBindingInfo.push_back(bind);
}
}
}
}
}
uint32_t Util::fileFlags() {
// FIXME: these need to determined at runtime.
if (_context.outputMachOType() == MH_OBJECT) {
return MH_SUBSECTIONS_VIA_SYMBOLS;
} else {
return MH_DYLDLINK | MH_NOUNDEFS | MH_TWOLEVEL;
}
}
} // end anonymous namespace
namespace lld {
namespace mach_o {
namespace normalized {
/// Convert a set of Atoms into a normalized mach-o file.
ErrorOr<std::unique_ptr<NormalizedFile>>
normalizedFromAtoms(const lld::File &atomFile,
const MachOLinkingContext &context) {
// The util object buffers info until the normalized file can be made.
Util util(context);
util.assignAtomsToSections(atomFile);
util.organizeSections();
std::unique_ptr<NormalizedFile> f(new NormalizedFile());
NormalizedFile &normFile = *f.get();
normFile.arch = context.arch();
normFile.fileType = context.outputMachOType();
normFile.flags = util.fileFlags();
normFile.installName = context.installName();
util.addDependentDylibs(atomFile, normFile);
util.copySegmentInfo(normFile);
util.copySectionInfo(normFile);
util.assignAddressesToSections(normFile);
util.buildAtomToAddressMap();
util.updateSectionInfo(normFile);
util.copySectionContent(normFile);
util.addSymbols(atomFile, normFile);
util.addIndirectSymbols(atomFile, normFile);
util.addRebaseAndBindingInfo(atomFile, normFile);
util.addSectionRelocs(atomFile, normFile);
util.buildDataInCodeArray(atomFile, normFile);
util.copyEntryPointAddress(normFile);
return std::move(f);
}
} // namespace normalized
} // namespace mach_o
} // namespace lld
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