737 lines · cpp
1//=--------- MachOLinkGraphBuilder.cpp - MachO LinkGraph builder ----------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// Generic MachO LinkGraph building code.10//11//===----------------------------------------------------------------------===//12 13#include "MachOLinkGraphBuilder.h"14#include "llvm/ADT/STLExtras.h"15#include "llvm/ADT/Sequence.h"16#include <optional>17 18#define DEBUG_TYPE "jitlink"19 20static const char *CommonSectionName = "__common";21 22namespace llvm {23namespace jitlink {24 25MachOLinkGraphBuilder::~MachOLinkGraphBuilder() = default;26 27Expected<std::unique_ptr<LinkGraph>> MachOLinkGraphBuilder::buildGraph() {28 29 // We only operate on relocatable objects.30 if (!Obj.isRelocatableObject())31 return make_error<JITLinkError>("Object is not a relocatable MachO");32 33 if (auto Err = createNormalizedSections())34 return std::move(Err);35 36 if (auto Err = createNormalizedSymbols())37 return std::move(Err);38 39 if (auto Err = graphifyRegularSymbols())40 return std::move(Err);41 42 if (auto Err = graphifySectionsWithCustomParsers())43 return std::move(Err);44 45 if (auto Err = addRelocations())46 return std::move(Err);47 48 return std::move(G);49}50 51MachOLinkGraphBuilder::MachOLinkGraphBuilder(52 const object::MachOObjectFile &Obj,53 std::shared_ptr<orc::SymbolStringPool> SSP, Triple TT,54 SubtargetFeatures Features,55 LinkGraph::GetEdgeKindNameFunction GetEdgeKindName)56 : Obj(Obj),57 G(std::make_unique<LinkGraph>(58 std::string(Obj.getFileName()), std::move(SSP), std::move(TT),59 std::move(Features), std::move(GetEdgeKindName))) {60 auto &MachHeader = Obj.getHeader64();61 SubsectionsViaSymbols = MachHeader.flags & MachO::MH_SUBSECTIONS_VIA_SYMBOLS;62}63 64void MachOLinkGraphBuilder::addCustomSectionParser(65 StringRef SectionName, SectionParserFunction Parser) {66 assert(!CustomSectionParserFunctions.count(SectionName) &&67 "Custom parser for this section already exists");68 CustomSectionParserFunctions[SectionName] = std::move(Parser);69}70 71Linkage MachOLinkGraphBuilder::getLinkage(uint16_t Desc) {72 if ((Desc & MachO::N_WEAK_DEF) || (Desc & MachO::N_WEAK_REF))73 return Linkage::Weak;74 return Linkage::Strong;75}76 77Scope MachOLinkGraphBuilder::getScope(StringRef Name, uint8_t Type) {78 if (Type & MachO::N_EXT) {79 if ((Type & MachO::N_PEXT) || Name.starts_with("l"))80 return Scope::Hidden;81 else82 return Scope::Default;83 }84 return Scope::Local;85}86 87bool MachOLinkGraphBuilder::isAltEntry(const NormalizedSymbol &NSym) {88 return NSym.Desc & MachO::N_ALT_ENTRY;89}90 91bool MachOLinkGraphBuilder::isDebugSection(const NormalizedSection &NSec) {92 return (NSec.Flags & MachO::S_ATTR_DEBUG &&93 strcmp(NSec.SegName, "__DWARF") == 0);94}95 96bool MachOLinkGraphBuilder::isZeroFillSection(const NormalizedSection &NSec) {97 switch (NSec.Flags & MachO::SECTION_TYPE) {98 case MachO::S_ZEROFILL:99 case MachO::S_GB_ZEROFILL:100 case MachO::S_THREAD_LOCAL_ZEROFILL:101 return true;102 default:103 return false;104 }105}106 107Section &MachOLinkGraphBuilder::getCommonSection() {108 if (!CommonSection)109 CommonSection = &G->createSection(CommonSectionName,110 orc::MemProt::Read | orc::MemProt::Write);111 return *CommonSection;112}113 114Error MachOLinkGraphBuilder::createNormalizedSections() {115 // Build normalized sections. Verifies that section data is in-range (for116 // sections with content) and that address ranges are non-overlapping.117 118 LLVM_DEBUG(dbgs() << "Creating normalized sections...\n");119 120 for (auto &SecRef : Obj.sections()) {121 NormalizedSection NSec;122 uint32_t DataOffset = 0;123 124 auto SecIndex = Obj.getSectionIndex(SecRef.getRawDataRefImpl());125 126 if (Obj.is64Bit()) {127 const MachO::section_64 &Sec64 =128 Obj.getSection64(SecRef.getRawDataRefImpl());129 130 memcpy(&NSec.SectName, &Sec64.sectname, 16);131 NSec.SectName[16] = '\0';132 memcpy(&NSec.SegName, Sec64.segname, 16);133 NSec.SegName[16] = '\0';134 135 NSec.Address = orc::ExecutorAddr(Sec64.addr);136 NSec.Size = Sec64.size;137 NSec.Alignment = 1ULL << Sec64.align;138 NSec.Flags = Sec64.flags;139 DataOffset = Sec64.offset;140 } else {141 const MachO::section &Sec32 = Obj.getSection(SecRef.getRawDataRefImpl());142 143 memcpy(&NSec.SectName, &Sec32.sectname, 16);144 NSec.SectName[16] = '\0';145 memcpy(&NSec.SegName, Sec32.segname, 16);146 NSec.SegName[16] = '\0';147 148 NSec.Address = orc::ExecutorAddr(Sec32.addr);149 NSec.Size = Sec32.size;150 NSec.Alignment = 1ULL << Sec32.align;151 NSec.Flags = Sec32.flags;152 DataOffset = Sec32.offset;153 }154 155 LLVM_DEBUG({156 dbgs() << " " << NSec.SegName << "," << NSec.SectName << ": "157 << formatv("{0:x16}", NSec.Address) << " -- "158 << formatv("{0:x16}", NSec.Address + NSec.Size)159 << ", align: " << NSec.Alignment << ", index: " << SecIndex160 << "\n";161 });162 163 // Get the section data if any.164 if (!isZeroFillSection(NSec)) {165 if (DataOffset + NSec.Size > Obj.getData().size())166 return make_error<JITLinkError>(167 "Section data extends past end of file");168 169 NSec.Data = Obj.getData().data() + DataOffset;170 }171 172 // Get prot flags.173 // FIXME: Make sure this test is correct (it's probably missing cases174 // as-is).175 orc::MemProt Prot;176 if (NSec.Flags & MachO::S_ATTR_PURE_INSTRUCTIONS)177 Prot = orc::MemProt::Read | orc::MemProt::Exec;178 else179 Prot = orc::MemProt::Read | orc::MemProt::Write;180 181 auto FullyQualifiedName =182 G->allocateContent(StringRef(NSec.SegName) + "," + NSec.SectName);183 NSec.GraphSection = &G->createSection(184 StringRef(FullyQualifiedName.data(), FullyQualifiedName.size()), Prot);185 186 // TODO: Are there any other criteria for NoAlloc lifetime?187 if (NSec.Flags & MachO::S_ATTR_DEBUG)188 NSec.GraphSection->setMemLifetime(orc::MemLifetime::NoAlloc);189 190 IndexToSection.insert(std::make_pair(SecIndex, std::move(NSec)));191 }192 193 std::vector<NormalizedSection *> Sections;194 Sections.reserve(IndexToSection.size());195 for (auto &KV : IndexToSection)196 Sections.push_back(&KV.second);197 198 // If we didn't end up creating any sections then bail out. The code below199 // assumes that we have at least one section.200 if (Sections.empty())201 return Error::success();202 203 llvm::sort(Sections,204 [](const NormalizedSection *LHS, const NormalizedSection *RHS) {205 assert(LHS && RHS && "Null section?");206 return std::tie(LHS->Address, LHS->Size) <207 std::tie(RHS->Address, RHS->Size);208 });209 210 for (unsigned I = 0, E = Sections.size() - 1; I != E; ++I) {211 auto &Cur = *Sections[I];212 auto &Next = *Sections[I + 1];213 if (Next.Address < Cur.Address + Cur.Size)214 return make_error<JITLinkError>(215 "Address range for section " +216 formatv("\"{0}/{1}\" [ {2:x16} -- {3:x16} ] ", Cur.SegName,217 Cur.SectName, Cur.Address, Cur.Address + Cur.Size) +218 "overlaps section \"" + Next.SegName + "/" + Next.SectName + "\"" +219 formatv("\"{0}/{1}\" [ {2:x16} -- {3:x16} ] ", Next.SegName,220 Next.SectName, Next.Address, Next.Address + Next.Size));221 }222 223 return Error::success();224}225 226Error MachOLinkGraphBuilder::createNormalizedSymbols() {227 LLVM_DEBUG(dbgs() << "Creating normalized symbols...\n");228 229 for (auto &SymRef : Obj.symbols()) {230 231 unsigned SymbolIndex = Obj.getSymbolIndex(SymRef.getRawDataRefImpl());232 uint64_t Value;233 uint32_t NStrX;234 uint8_t Type;235 uint8_t Sect;236 uint16_t Desc;237 238 if (Obj.is64Bit()) {239 const MachO::nlist_64 &NL64 =240 Obj.getSymbol64TableEntry(SymRef.getRawDataRefImpl());241 Value = NL64.n_value;242 NStrX = NL64.n_strx;243 Type = NL64.n_type;244 Sect = NL64.n_sect;245 Desc = NL64.n_desc;246 } else {247 const MachO::nlist &NL32 =248 Obj.getSymbolTableEntry(SymRef.getRawDataRefImpl());249 Value = NL32.n_value;250 NStrX = NL32.n_strx;251 Type = NL32.n_type;252 Sect = NL32.n_sect;253 Desc = NL32.n_desc;254 }255 256 // Skip stabs.257 // FIXME: Are there other symbols we should be skipping?258 if (Type & MachO::N_STAB)259 continue;260 261 std::optional<StringRef> Name;262 if (NStrX) {263 if (auto NameOrErr = SymRef.getName())264 Name = *NameOrErr;265 else266 return NameOrErr.takeError();267 } else if (Type & MachO::N_EXT)268 return make_error<JITLinkError>("Symbol at index " +269 formatv("{0}", SymbolIndex) +270 " has no name (string table index 0), "271 "but N_EXT bit is set");272 273 LLVM_DEBUG({274 dbgs() << " ";275 if (!Name)276 dbgs() << "<anonymous symbol>";277 else278 dbgs() << *Name;279 dbgs() << ": value = " << formatv("{0:x16}", Value)280 << ", type = " << formatv("{0:x2}", Type)281 << ", desc = " << formatv("{0:x4}", Desc) << ", sect = ";282 if (Sect)283 dbgs() << static_cast<unsigned>(Sect - 1);284 else285 dbgs() << "none";286 dbgs() << "\n";287 });288 289 // If this symbol has a section, verify that the addresses line up.290 if (Sect != 0) {291 auto NSec = findSectionByIndex(Sect - 1);292 if (!NSec)293 return NSec.takeError();294 295 if (orc::ExecutorAddr(Value) < NSec->Address ||296 orc::ExecutorAddr(Value) > NSec->Address + NSec->Size)297 return make_error<JITLinkError>("Address " + formatv("{0:x}", Value) +298 " for symbol " + *Name +299 " does not fall within section");300 301 if (!NSec->GraphSection) {302 LLVM_DEBUG({303 dbgs() << " Skipping: Symbol is in section " << NSec->SegName << "/"304 << NSec->SectName305 << " which has no associated graph section.\n";306 });307 continue;308 }309 }310 311 IndexToSymbol[SymbolIndex] = &createNormalizedSymbol(312 Name, Value, Type, Sect, Desc, getLinkage(Desc), getScope(*Name, Type));313 }314 315 return Error::success();316}317 318void MachOLinkGraphBuilder::addSectionStartSymAndBlock(319 unsigned SecIndex, Section &GraphSec, orc::ExecutorAddr Address,320 const char *Data, orc::ExecutorAddrDiff Size, uint32_t Alignment,321 bool IsLive) {322 Block &B =323 Data ? G->createContentBlock(GraphSec, ArrayRef<char>(Data, Size),324 Address, Alignment, 0)325 : G->createZeroFillBlock(GraphSec, Size, Address, Alignment, 0);326 auto &Sym = G->addAnonymousSymbol(B, 0, Size, false, IsLive);327 auto SecI = IndexToSection.find(SecIndex);328 assert(SecI != IndexToSection.end() && "SecIndex invalid");329 auto &NSec = SecI->second;330 assert(!NSec.CanonicalSymbols.count(Sym.getAddress()) &&331 "Anonymous block start symbol clashes with existing symbol address");332 NSec.CanonicalSymbols[Sym.getAddress()] = &Sym;333}334 335Error MachOLinkGraphBuilder::graphifyRegularSymbols() {336 337 LLVM_DEBUG(dbgs() << "Creating graph symbols...\n");338 339 /// We only have 256 section indexes: Use a vector rather than a map.340 std::vector<std::vector<NormalizedSymbol *>> SecIndexToSymbols;341 SecIndexToSymbols.resize(256);342 343 // Create commons, externs, and absolutes, and partition all other symbols by344 // section.345 for (auto &KV : IndexToSymbol) {346 auto &NSym = *KV.second;347 348 switch (NSym.Type & MachO::N_TYPE) {349 case MachO::N_UNDF:350 if (NSym.Value) {351 if (!NSym.Name)352 return make_error<JITLinkError>("Anonymous common symbol at index " +353 Twine(KV.first));354 NSym.GraphSymbol = &G->addDefinedSymbol(355 G->createZeroFillBlock(getCommonSection(),356 orc::ExecutorAddrDiff(NSym.Value),357 orc::ExecutorAddr(),358 1ull << MachO::GET_COMM_ALIGN(NSym.Desc), 0),359 0, *NSym.Name, orc::ExecutorAddrDiff(NSym.Value), Linkage::Weak,360 NSym.S, false, NSym.Desc & MachO::N_NO_DEAD_STRIP);361 } else {362 if (!NSym.Name)363 return make_error<JITLinkError>("Anonymous external symbol at "364 "index " +365 Twine(KV.first));366 NSym.GraphSymbol = &G->addExternalSymbol(367 *NSym.Name, 0, (NSym.Desc & MachO::N_WEAK_REF) != 0);368 }369 break;370 case MachO::N_ABS:371 if (!NSym.Name)372 return make_error<JITLinkError>("Anonymous absolute symbol at index " +373 Twine(KV.first));374 NSym.GraphSymbol = &G->addAbsoluteSymbol(375 *NSym.Name, orc::ExecutorAddr(NSym.Value), 0, Linkage::Strong,376 getScope(*NSym.Name, NSym.Type), NSym.Desc & MachO::N_NO_DEAD_STRIP);377 break;378 case MachO::N_SECT:379 SecIndexToSymbols[NSym.Sect - 1].push_back(&NSym);380 break;381 case MachO::N_PBUD:382 return make_error<JITLinkError>(383 "Unupported N_PBUD symbol " +384 (NSym.Name ? ("\"" + *NSym.Name + "\"") : Twine("<anon>")) +385 " at index " + Twine(KV.first));386 case MachO::N_INDR:387 return make_error<JITLinkError>(388 "Unupported N_INDR symbol " +389 (NSym.Name ? ("\"" + *NSym.Name + "\"") : Twine("<anon>")) +390 " at index " + Twine(KV.first));391 default:392 return make_error<JITLinkError>(393 "Unrecognized symbol type " + Twine(NSym.Type & MachO::N_TYPE) +394 " for symbol " +395 (NSym.Name ? ("\"" + *NSym.Name + "\"") : Twine("<anon>")) +396 " at index " + Twine(KV.first));397 }398 }399 400 // Loop over sections performing regular graphification for those that401 // don't have custom parsers.402 for (auto &KV : IndexToSection) {403 auto SecIndex = KV.first;404 auto &NSec = KV.second;405 406 if (!NSec.GraphSection) {407 LLVM_DEBUG({408 dbgs() << " " << NSec.SegName << "/" << NSec.SectName409 << " has no graph section. Skipping.\n";410 });411 continue;412 }413 414 // Skip sections with custom parsers.415 if (CustomSectionParserFunctions.count(NSec.GraphSection->getName())) {416 LLVM_DEBUG({417 dbgs() << " Skipping section " << NSec.GraphSection->getName()418 << " as it has a custom parser.\n";419 });420 continue;421 } else if ((NSec.Flags & MachO::SECTION_TYPE) ==422 MachO::S_CSTRING_LITERALS) {423 if (auto Err = graphifyCStringSection(424 NSec, std::move(SecIndexToSymbols[SecIndex])))425 return Err;426 continue;427 } else428 LLVM_DEBUG({429 dbgs() << " Graphifying regular section "430 << NSec.GraphSection->getName() << "...\n";431 });432 433 bool SectionIsNoDeadStrip = NSec.Flags & MachO::S_ATTR_NO_DEAD_STRIP;434 bool SectionIsText = NSec.Flags & MachO::S_ATTR_PURE_INSTRUCTIONS;435 436 auto &SecNSymStack = SecIndexToSymbols[SecIndex];437 438 // If this section is non-empty but there are no symbols covering it then439 // create one block and anonymous symbol to cover the entire section.440 if (SecNSymStack.empty()) {441 if (NSec.Size > 0) {442 LLVM_DEBUG({443 dbgs() << " Section non-empty, but contains no symbols. "444 "Creating anonymous block to cover "445 << formatv("{0:x16}", NSec.Address) << " -- "446 << formatv("{0:x16}", NSec.Address + NSec.Size) << "\n";447 });448 addSectionStartSymAndBlock(SecIndex, *NSec.GraphSection, NSec.Address,449 NSec.Data, NSec.Size, NSec.Alignment,450 SectionIsNoDeadStrip);451 } else452 LLVM_DEBUG({453 dbgs() << " Section empty and contains no symbols. Skipping.\n";454 });455 continue;456 }457 458 // Sort the symbol stack in by address, alt-entry status, scope, and name.459 // We sort in reverse order so that symbols will be visited in the right460 // order when we pop off the stack below.461 llvm::sort(SecNSymStack, [](const NormalizedSymbol *LHS,462 const NormalizedSymbol *RHS) {463 if (LHS->Value != RHS->Value)464 return LHS->Value > RHS->Value;465 if (isAltEntry(*LHS) != isAltEntry(*RHS))466 return isAltEntry(*RHS);467 if (LHS->S != RHS->S)468 return static_cast<uint8_t>(LHS->S) < static_cast<uint8_t>(RHS->S);469 return LHS->Name < RHS->Name;470 });471 472 // The first symbol in a section can not be an alt-entry symbol.473 if (!SecNSymStack.empty() && isAltEntry(*SecNSymStack.back()))474 return make_error<JITLinkError>(475 "First symbol in " + NSec.GraphSection->getName() + " is alt-entry");476 477 // If the section is non-empty but there is no symbol covering the start478 // address then add an anonymous one.479 if (orc::ExecutorAddr(SecNSymStack.back()->Value) != NSec.Address) {480 auto AnonBlockSize =481 orc::ExecutorAddr(SecNSymStack.back()->Value) - NSec.Address;482 LLVM_DEBUG({483 dbgs() << " Section start not covered by symbol. "484 << "Creating anonymous block to cover [ " << NSec.Address485 << " -- " << (NSec.Address + AnonBlockSize) << " ]\n";486 });487 addSectionStartSymAndBlock(SecIndex, *NSec.GraphSection, NSec.Address,488 NSec.Data, AnonBlockSize, NSec.Alignment,489 SectionIsNoDeadStrip);490 }491 492 // Visit section symbols in order by popping off the reverse-sorted stack,493 // building graph symbols as we go.494 //495 // If MH_SUBSECTIONS_VIA_SYMBOLS is set we'll build a block for each496 // alt-entry chain.497 //498 // If MH_SUBSECTIONS_VIA_SYMBOLS is not set then we'll just build one block499 // for the whole section.500 while (!SecNSymStack.empty()) {501 SmallVector<NormalizedSymbol *, 8> BlockSyms;502 503 // Get the symbols in this alt-entry chain, or the whole section (if504 // !SubsectionsViaSymbols).505 BlockSyms.push_back(SecNSymStack.back());506 SecNSymStack.pop_back();507 while (!SecNSymStack.empty() &&508 (isAltEntry(*SecNSymStack.back()) ||509 SecNSymStack.back()->Value == BlockSyms.back()->Value ||510 !SubsectionsViaSymbols)) {511 BlockSyms.push_back(SecNSymStack.back());512 SecNSymStack.pop_back();513 }514 515 // BlockNSyms now contains the block symbols in reverse canonical order.516 auto BlockStart = orc::ExecutorAddr(BlockSyms.front()->Value);517 orc::ExecutorAddr BlockEnd =518 SecNSymStack.empty() ? NSec.Address + NSec.Size519 : orc::ExecutorAddr(SecNSymStack.back()->Value);520 orc::ExecutorAddrDiff BlockOffset = BlockStart - NSec.Address;521 orc::ExecutorAddrDiff BlockSize = BlockEnd - BlockStart;522 523 LLVM_DEBUG({524 dbgs() << " Creating block for " << formatv("{0:x16}", BlockStart)525 << " -- " << formatv("{0:x16}", BlockEnd) << ": "526 << NSec.GraphSection->getName() << " + "527 << formatv("{0:x16}", BlockOffset) << " with "528 << BlockSyms.size() << " symbol(s)...\n";529 });530 531 Block &B =532 NSec.Data533 ? G->createContentBlock(534 *NSec.GraphSection,535 ArrayRef<char>(NSec.Data + BlockOffset, BlockSize),536 BlockStart, NSec.Alignment, BlockStart % NSec.Alignment)537 : G->createZeroFillBlock(*NSec.GraphSection, BlockSize,538 BlockStart, NSec.Alignment,539 BlockStart % NSec.Alignment);540 541 std::optional<orc::ExecutorAddr> LastCanonicalAddr;542 auto SymEnd = BlockEnd;543 while (!BlockSyms.empty()) {544 auto &NSym = *BlockSyms.back();545 BlockSyms.pop_back();546 547 bool SymLive =548 (NSym.Desc & MachO::N_NO_DEAD_STRIP) || SectionIsNoDeadStrip;549 550 auto &Sym = createStandardGraphSymbol(551 NSym, B, SymEnd - orc::ExecutorAddr(NSym.Value), SectionIsText,552 SymLive, LastCanonicalAddr != orc::ExecutorAddr(NSym.Value));553 554 if (LastCanonicalAddr != Sym.getAddress()) {555 if (LastCanonicalAddr)556 SymEnd = *LastCanonicalAddr;557 LastCanonicalAddr = Sym.getAddress();558 }559 }560 }561 }562 563 return Error::success();564}565 566Symbol &MachOLinkGraphBuilder::createStandardGraphSymbol(NormalizedSymbol &NSym,567 Block &B, size_t Size,568 bool IsText,569 bool IsNoDeadStrip,570 bool IsCanonical) {571 572 LLVM_DEBUG({573 dbgs() << " " << formatv("{0:x16}", NSym.Value) << " -- "574 << formatv("{0:x16}", NSym.Value + Size) << ": ";575 if (!NSym.Name)576 dbgs() << "<anonymous symbol>";577 else578 dbgs() << *NSym.Name;579 if (IsText)580 dbgs() << " [text]";581 if (IsNoDeadStrip)582 dbgs() << " [no-dead-strip]";583 if (!IsCanonical)584 dbgs() << " [non-canonical]";585 dbgs() << "\n";586 });587 588 auto SymOffset = orc::ExecutorAddr(NSym.Value) - B.getAddress();589 auto &Sym =590 NSym.Name591 ? G->addDefinedSymbol(B, SymOffset, *NSym.Name, Size, NSym.L, NSym.S,592 IsText, IsNoDeadStrip)593 : G->addAnonymousSymbol(B, SymOffset, Size, IsText, IsNoDeadStrip);594 NSym.GraphSymbol = &Sym;595 596 if (IsCanonical)597 setCanonicalSymbol(getSectionByIndex(NSym.Sect - 1), Sym);598 599 return Sym;600}601 602Error MachOLinkGraphBuilder::graphifySectionsWithCustomParsers() {603 // Graphify special sections.604 for (auto &KV : IndexToSection) {605 auto &NSec = KV.second;606 607 // Skip non-graph sections.608 if (!NSec.GraphSection)609 continue;610 611 auto HI = CustomSectionParserFunctions.find(NSec.GraphSection->getName());612 if (HI != CustomSectionParserFunctions.end()) {613 auto &Parse = HI->second;614 if (auto Err = Parse(NSec))615 return Err;616 }617 }618 619 return Error::success();620}621 622Error MachOLinkGraphBuilder::graphifyCStringSection(623 NormalizedSection &NSec, std::vector<NormalizedSymbol *> NSyms) {624 assert(NSec.GraphSection && "C string literal section missing graph section");625 assert(NSec.Data && "C string literal section has no data");626 627 LLVM_DEBUG({628 dbgs() << " Graphifying C-string literal section "629 << NSec.GraphSection->getName() << "\n";630 });631 632 if (NSec.Data[NSec.Size - 1] != '\0')633 return make_error<JITLinkError>("C string literal section " +634 NSec.GraphSection->getName() +635 " does not end with null terminator");636 637 /// Sort into reverse order to use as a stack.638 llvm::sort(NSyms,639 [](const NormalizedSymbol *LHS, const NormalizedSymbol *RHS) {640 if (LHS->Value != RHS->Value)641 return LHS->Value > RHS->Value;642 if (LHS->L != RHS->L)643 return LHS->L > RHS->L;644 if (LHS->S != RHS->S)645 return LHS->S > RHS->S;646 if (RHS->Name) {647 if (!LHS->Name)648 return true;649 return *LHS->Name > *RHS->Name;650 }651 return false;652 });653 654 bool SectionIsNoDeadStrip = NSec.Flags & MachO::S_ATTR_NO_DEAD_STRIP;655 bool SectionIsText = NSec.Flags & MachO::S_ATTR_PURE_INSTRUCTIONS;656 orc::ExecutorAddrDiff BlockStart = 0;657 658 // Scan section for null characters.659 for (size_t I = 0; I != NSec.Size; ++I) {660 if (NSec.Data[I] == '\0') {661 size_t BlockSize = I + 1 - BlockStart;662 // Create a block for this null terminated string.663 auto &B = G->createContentBlock(*NSec.GraphSection,664 {NSec.Data + BlockStart, BlockSize},665 NSec.Address + BlockStart, NSec.Alignment,666 BlockStart % NSec.Alignment);667 668 LLVM_DEBUG({669 dbgs() << " Created block " << B.getRange()670 << ", align = " << B.getAlignment()671 << ", align-ofs = " << B.getAlignmentOffset() << " for \"";672 for (size_t J = 0; J != std::min(B.getSize(), size_t(16)); ++J)673 switch (B.getContent()[J]) {674 case '\0': break;675 case '\n': dbgs() << "\\n"; break;676 case '\t': dbgs() << "\\t"; break;677 default: dbgs() << B.getContent()[J]; break;678 }679 if (B.getSize() > 16)680 dbgs() << "...";681 dbgs() << "\"\n";682 });683 684 // If there's no symbol at the start of this block then create one.685 if (NSyms.empty() ||686 orc::ExecutorAddr(NSyms.back()->Value) != B.getAddress()) {687 auto &S = G->addAnonymousSymbol(B, 0, BlockSize, false, false);688 setCanonicalSymbol(NSec, S);689 LLVM_DEBUG({690 dbgs() << " Adding symbol for c-string block " << B.getRange()691 << ": <anonymous symbol> at offset 0\n";692 });693 }694 695 // Process any remaining symbols that point into this block.696 auto LastCanonicalAddr = B.getAddress() + BlockSize;697 while (!NSyms.empty() && orc::ExecutorAddr(NSyms.back()->Value) <698 B.getAddress() + BlockSize) {699 auto &NSym = *NSyms.back();700 size_t SymSize = (B.getAddress() + BlockSize) -701 orc::ExecutorAddr(NSyms.back()->Value);702 bool SymLive =703 (NSym.Desc & MachO::N_NO_DEAD_STRIP) || SectionIsNoDeadStrip;704 705 bool IsCanonical = false;706 if (LastCanonicalAddr != orc::ExecutorAddr(NSym.Value)) {707 IsCanonical = true;708 LastCanonicalAddr = orc::ExecutorAddr(NSym.Value);709 }710 711 auto &Sym = createStandardGraphSymbol(NSym, B, SymSize, SectionIsText,712 SymLive, IsCanonical);713 (void)Sym;714 LLVM_DEBUG({715 dbgs() << " Adding symbol for c-string block " << B.getRange()716 << ": "717 << (Sym.hasName() ? *Sym.getName() : "<anonymous symbol>")718 << " at offset " << formatv("{0:x}", Sym.getOffset()) << "\n";719 });720 721 NSyms.pop_back();722 }723 724 BlockStart += BlockSize;725 }726 }727 728 assert(llvm::all_of(NSec.GraphSection->blocks(),729 [](Block *B) { return isCStringBlock(*B); }) &&730 "All blocks in section should hold single c-strings");731 732 return Error::success();733}734 735} // end namespace jitlink736} // end namespace llvm737