| //===- IRSymtab.cpp - implementation of IR symbol tables ------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Object/IRSymtab.h" |
| #include "llvm/ADT/ArrayRef.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/SmallString.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/StringRef.h" |
| #include "llvm/ADT/Triple.h" |
| #include "llvm/Config/llvm-config.h" |
| #include "llvm/IR/Comdat.h" |
| #include "llvm/IR/DataLayout.h" |
| #include "llvm/IR/GlobalAlias.h" |
| #include "llvm/IR/GlobalObject.h" |
| #include "llvm/IR/Mangler.h" |
| #include "llvm/IR/Metadata.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/Bitcode/BitcodeReader.h" |
| #include "llvm/MC/StringTableBuilder.h" |
| #include "llvm/Object/IRObjectFile.h" |
| #include "llvm/Object/ModuleSymbolTable.h" |
| #include "llvm/Object/SymbolicFile.h" |
| #include "llvm/Support/Allocator.h" |
| #include "llvm/Support/Casting.h" |
| #include "llvm/Support/Error.h" |
| #include "llvm/Support/StringSaver.h" |
| #include "llvm/Support/VCSRevision.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include <cassert> |
| #include <string> |
| #include <utility> |
| #include <vector> |
| |
| using namespace llvm; |
| using namespace irsymtab; |
| |
| static const char *PreservedSymbols[] = { |
| #define HANDLE_LIBCALL(code, name) name, |
| #include "llvm/IR/RuntimeLibcalls.def" |
| #undef HANDLE_LIBCALL |
| // There are global variables, so put it here instead of in |
| // RuntimeLibcalls.def. |
| // TODO: Are there similar such variables? |
| "__ssp_canary_word", |
| "__stack_chk_guard", |
| }; |
| |
| namespace { |
| |
| const char *getExpectedProducerName() { |
| static char DefaultName[] = LLVM_VERSION_STRING |
| #ifdef LLVM_REVISION |
| " " LLVM_REVISION |
| #endif |
| ; |
| // Allows for testing of the irsymtab writer and upgrade mechanism. This |
| // environment variable should not be set by users. |
| if (char *OverrideName = getenv("LLVM_OVERRIDE_PRODUCER")) |
| return OverrideName; |
| return DefaultName; |
| } |
| |
| const char *kExpectedProducerName = getExpectedProducerName(); |
| |
| /// Stores the temporary state that is required to build an IR symbol table. |
| struct Builder { |
| SmallVector<char, 0> &Symtab; |
| StringTableBuilder &StrtabBuilder; |
| StringSaver Saver; |
| |
| // This ctor initializes a StringSaver using the passed in BumpPtrAllocator. |
| // The StringTableBuilder does not create a copy of any strings added to it, |
| // so this provides somewhere to store any strings that we create. |
| Builder(SmallVector<char, 0> &Symtab, StringTableBuilder &StrtabBuilder, |
| BumpPtrAllocator &Alloc) |
| : Symtab(Symtab), StrtabBuilder(StrtabBuilder), Saver(Alloc) {} |
| |
| DenseMap<const Comdat *, int> ComdatMap; |
| Mangler Mang; |
| Triple TT; |
| |
| std::vector<storage::Comdat> Comdats; |
| std::vector<storage::Module> Mods; |
| std::vector<storage::Symbol> Syms; |
| std::vector<storage::Uncommon> Uncommons; |
| |
| std::string COFFLinkerOpts; |
| raw_string_ostream COFFLinkerOptsOS{COFFLinkerOpts}; |
| |
| std::vector<storage::Str> DependentLibraries; |
| |
| void setStr(storage::Str &S, StringRef Value) { |
| S.Offset = StrtabBuilder.add(Value); |
| S.Size = Value.size(); |
| } |
| |
| template <typename T> |
| void writeRange(storage::Range<T> &R, const std::vector<T> &Objs) { |
| R.Offset = Symtab.size(); |
| R.Size = Objs.size(); |
| Symtab.insert(Symtab.end(), reinterpret_cast<const char *>(Objs.data()), |
| reinterpret_cast<const char *>(Objs.data() + Objs.size())); |
| } |
| |
| Expected<int> getComdatIndex(const Comdat *C, const Module *M); |
| |
| Error addModule(Module *M); |
| Error addSymbol(const ModuleSymbolTable &Msymtab, |
| const SmallPtrSet<GlobalValue *, 4> &Used, |
| ModuleSymbolTable::Symbol Sym); |
| |
| Error build(ArrayRef<Module *> Mods); |
| }; |
| |
| Error Builder::addModule(Module *M) { |
| if (M->getDataLayoutStr().empty()) |
| return make_error<StringError>("input module has no datalayout", |
| inconvertibleErrorCode()); |
| |
| // Symbols in the llvm.used list will get the FB_Used bit and will not be |
| // internalized. We do this for llvm.compiler.used as well: |
| // |
| // IR symbol table tracks module-level asm symbol references but not inline |
| // asm. A symbol only referenced by inline asm is not in the IR symbol table, |
| // so we may not know that the definition (in another translation unit) is |
| // referenced. That definition may have __attribute__((used)) (which lowers to |
| // llvm.compiler.used on ELF targets) to communicate to the compiler that it |
| // may be used by inline asm. The usage is perfectly fine, so we treat |
| // llvm.compiler.used conservatively as llvm.used to work around our own |
| // limitation. |
| SmallVector<GlobalValue *, 4> UsedV; |
| collectUsedGlobalVariables(*M, UsedV, /*CompilerUsed=*/false); |
| collectUsedGlobalVariables(*M, UsedV, /*CompilerUsed=*/true); |
| SmallPtrSet<GlobalValue *, 4> Used(UsedV.begin(), UsedV.end()); |
| |
| ModuleSymbolTable Msymtab; |
| Msymtab.addModule(M); |
| |
| storage::Module Mod; |
| Mod.Begin = Syms.size(); |
| Mod.End = Syms.size() + Msymtab.symbols().size(); |
| Mod.UncBegin = Uncommons.size(); |
| Mods.push_back(Mod); |
| |
| if (TT.isOSBinFormatCOFF()) { |
| if (auto E = M->materializeMetadata()) |
| return E; |
| if (NamedMDNode *LinkerOptions = |
| M->getNamedMetadata("llvm.linker.options")) { |
| for (MDNode *MDOptions : LinkerOptions->operands()) |
| for (const MDOperand &MDOption : cast<MDNode>(MDOptions)->operands()) |
| COFFLinkerOptsOS << " " << cast<MDString>(MDOption)->getString(); |
| } |
| } |
| |
| if (TT.isOSBinFormatELF()) { |
| if (auto E = M->materializeMetadata()) |
| return E; |
| if (NamedMDNode *N = M->getNamedMetadata("llvm.dependent-libraries")) { |
| for (MDNode *MDOptions : N->operands()) { |
| const auto OperandStr = |
| cast<MDString>(cast<MDNode>(MDOptions)->getOperand(0))->getString(); |
| storage::Str Specifier; |
| setStr(Specifier, OperandStr); |
| DependentLibraries.emplace_back(Specifier); |
| } |
| } |
| } |
| |
| for (ModuleSymbolTable::Symbol Msym : Msymtab.symbols()) |
| if (Error Err = addSymbol(Msymtab, Used, Msym)) |
| return Err; |
| |
| return Error::success(); |
| } |
| |
| Expected<int> Builder::getComdatIndex(const Comdat *C, const Module *M) { |
| auto P = ComdatMap.insert(std::make_pair(C, Comdats.size())); |
| if (P.second) { |
| std::string Name; |
| if (TT.isOSBinFormatCOFF()) { |
| const GlobalValue *GV = M->getNamedValue(C->getName()); |
| if (!GV) |
| return make_error<StringError>("Could not find leader", |
| inconvertibleErrorCode()); |
| // Internal leaders do not affect symbol resolution, therefore they do not |
| // appear in the symbol table. |
| if (GV->hasLocalLinkage()) { |
| P.first->second = -1; |
| return -1; |
| } |
| llvm::raw_string_ostream OS(Name); |
| Mang.getNameWithPrefix(OS, GV, false); |
| } else { |
| Name = std::string(C->getName()); |
| } |
| |
| storage::Comdat Comdat; |
| setStr(Comdat.Name, Saver.save(Name)); |
| Comdat.SelectionKind = C->getSelectionKind(); |
| Comdats.push_back(Comdat); |
| } |
| |
| return P.first->second; |
| } |
| |
| Error Builder::addSymbol(const ModuleSymbolTable &Msymtab, |
| const SmallPtrSet<GlobalValue *, 4> &Used, |
| ModuleSymbolTable::Symbol Msym) { |
| Syms.emplace_back(); |
| storage::Symbol &Sym = Syms.back(); |
| Sym = {}; |
| |
| storage::Uncommon *Unc = nullptr; |
| auto Uncommon = [&]() -> storage::Uncommon & { |
| if (Unc) |
| return *Unc; |
| Sym.Flags |= 1 << storage::Symbol::FB_has_uncommon; |
| Uncommons.emplace_back(); |
| Unc = &Uncommons.back(); |
| *Unc = {}; |
| setStr(Unc->COFFWeakExternFallbackName, ""); |
| setStr(Unc->SectionName, ""); |
| return *Unc; |
| }; |
| |
| SmallString<64> Name; |
| { |
| raw_svector_ostream OS(Name); |
| Msymtab.printSymbolName(OS, Msym); |
| } |
| setStr(Sym.Name, Saver.save(Name.str())); |
| |
| auto Flags = Msymtab.getSymbolFlags(Msym); |
| if (Flags & object::BasicSymbolRef::SF_Undefined) |
| Sym.Flags |= 1 << storage::Symbol::FB_undefined; |
| if (Flags & object::BasicSymbolRef::SF_Weak) |
| Sym.Flags |= 1 << storage::Symbol::FB_weak; |
| if (Flags & object::BasicSymbolRef::SF_Common) |
| Sym.Flags |= 1 << storage::Symbol::FB_common; |
| if (Flags & object::BasicSymbolRef::SF_Indirect) |
| Sym.Flags |= 1 << storage::Symbol::FB_indirect; |
| if (Flags & object::BasicSymbolRef::SF_Global) |
| Sym.Flags |= 1 << storage::Symbol::FB_global; |
| if (Flags & object::BasicSymbolRef::SF_FormatSpecific) |
| Sym.Flags |= 1 << storage::Symbol::FB_format_specific; |
| if (Flags & object::BasicSymbolRef::SF_Executable) |
| Sym.Flags |= 1 << storage::Symbol::FB_executable; |
| |
| Sym.ComdatIndex = -1; |
| auto *GV = Msym.dyn_cast<GlobalValue *>(); |
| if (!GV) { |
| // Undefined module asm symbols act as GC roots and are implicitly used. |
| if (Flags & object::BasicSymbolRef::SF_Undefined) |
| Sym.Flags |= 1 << storage::Symbol::FB_used; |
| setStr(Sym.IRName, ""); |
| return Error::success(); |
| } |
| |
| setStr(Sym.IRName, GV->getName()); |
| |
| bool IsPreservedSymbol = llvm::is_contained(PreservedSymbols, GV->getName()); |
| |
| if (Used.count(GV) || IsPreservedSymbol) |
| Sym.Flags |= 1 << storage::Symbol::FB_used; |
| if (GV->isThreadLocal()) |
| Sym.Flags |= 1 << storage::Symbol::FB_tls; |
| if (GV->hasGlobalUnnamedAddr()) |
| Sym.Flags |= 1 << storage::Symbol::FB_unnamed_addr; |
| if (GV->canBeOmittedFromSymbolTable()) |
| Sym.Flags |= 1 << storage::Symbol::FB_may_omit; |
| Sym.Flags |= unsigned(GV->getVisibility()) << storage::Symbol::FB_visibility; |
| |
| if (Flags & object::BasicSymbolRef::SF_Common) { |
| auto *GVar = dyn_cast<GlobalVariable>(GV); |
| if (!GVar) |
| return make_error<StringError>("Only variables can have common linkage!", |
| inconvertibleErrorCode()); |
| Uncommon().CommonSize = |
| GV->getParent()->getDataLayout().getTypeAllocSize(GV->getValueType()); |
| Uncommon().CommonAlign = GVar->getAlignment(); |
| } |
| |
| const GlobalObject *GO = GV->getAliaseeObject(); |
| if (!GO) { |
| if (isa<GlobalIFunc>(GV)) |
| GO = cast<GlobalIFunc>(GV)->getResolverFunction(); |
| if (!GO) |
| return make_error<StringError>("Unable to determine comdat of alias!", |
| inconvertibleErrorCode()); |
| } |
| if (const Comdat *C = GO->getComdat()) { |
| Expected<int> ComdatIndexOrErr = getComdatIndex(C, GV->getParent()); |
| if (!ComdatIndexOrErr) |
| return ComdatIndexOrErr.takeError(); |
| Sym.ComdatIndex = *ComdatIndexOrErr; |
| } |
| |
| if (TT.isOSBinFormatCOFF()) { |
| emitLinkerFlagsForGlobalCOFF(COFFLinkerOptsOS, GV, TT, Mang); |
| |
| if ((Flags & object::BasicSymbolRef::SF_Weak) && |
| (Flags & object::BasicSymbolRef::SF_Indirect)) { |
| auto *Fallback = dyn_cast<GlobalValue>( |
| cast<GlobalAlias>(GV)->getAliasee()->stripPointerCasts()); |
| if (!Fallback) |
| return make_error<StringError>("Invalid weak external", |
| inconvertibleErrorCode()); |
| std::string FallbackName; |
| raw_string_ostream OS(FallbackName); |
| Msymtab.printSymbolName(OS, Fallback); |
| OS.flush(); |
| setStr(Uncommon().COFFWeakExternFallbackName, Saver.save(FallbackName)); |
| } |
| } |
| |
| if (!GO->getSection().empty()) |
| setStr(Uncommon().SectionName, Saver.save(GO->getSection())); |
| |
| return Error::success(); |
| } |
| |
| Error Builder::build(ArrayRef<Module *> IRMods) { |
| storage::Header Hdr; |
| |
| assert(!IRMods.empty()); |
| Hdr.Version = storage::Header::kCurrentVersion; |
| setStr(Hdr.Producer, kExpectedProducerName); |
| setStr(Hdr.TargetTriple, IRMods[0]->getTargetTriple()); |
| setStr(Hdr.SourceFileName, IRMods[0]->getSourceFileName()); |
| TT = Triple(IRMods[0]->getTargetTriple()); |
| |
| for (auto *M : IRMods) |
| if (Error Err = addModule(M)) |
| return Err; |
| |
| COFFLinkerOptsOS.flush(); |
| setStr(Hdr.COFFLinkerOpts, Saver.save(COFFLinkerOpts)); |
| |
| // We are about to fill in the header's range fields, so reserve space for it |
| // and copy it in afterwards. |
| Symtab.resize(sizeof(storage::Header)); |
| writeRange(Hdr.Modules, Mods); |
| writeRange(Hdr.Comdats, Comdats); |
| writeRange(Hdr.Symbols, Syms); |
| writeRange(Hdr.Uncommons, Uncommons); |
| writeRange(Hdr.DependentLibraries, DependentLibraries); |
| *reinterpret_cast<storage::Header *>(Symtab.data()) = Hdr; |
| return Error::success(); |
| } |
| |
| } // end anonymous namespace |
| |
| Error irsymtab::build(ArrayRef<Module *> Mods, SmallVector<char, 0> &Symtab, |
| StringTableBuilder &StrtabBuilder, |
| BumpPtrAllocator &Alloc) { |
| return Builder(Symtab, StrtabBuilder, Alloc).build(Mods); |
| } |
| |
| // Upgrade a vector of bitcode modules created by an old version of LLVM by |
| // creating an irsymtab for them in the current format. |
| static Expected<FileContents> upgrade(ArrayRef<BitcodeModule> BMs) { |
| FileContents FC; |
| |
| LLVMContext Ctx; |
| std::vector<Module *> Mods; |
| std::vector<std::unique_ptr<Module>> OwnedMods; |
| for (auto BM : BMs) { |
| Expected<std::unique_ptr<Module>> MOrErr = |
| BM.getLazyModule(Ctx, /*ShouldLazyLoadMetadata*/ true, |
| /*IsImporting*/ false); |
| if (!MOrErr) |
| return MOrErr.takeError(); |
| |
| Mods.push_back(MOrErr->get()); |
| OwnedMods.push_back(std::move(*MOrErr)); |
| } |
| |
| StringTableBuilder StrtabBuilder(StringTableBuilder::RAW); |
| BumpPtrAllocator Alloc; |
| if (Error E = build(Mods, FC.Symtab, StrtabBuilder, Alloc)) |
| return std::move(E); |
| |
| StrtabBuilder.finalizeInOrder(); |
| FC.Strtab.resize(StrtabBuilder.getSize()); |
| StrtabBuilder.write((uint8_t *)FC.Strtab.data()); |
| |
| FC.TheReader = {{FC.Symtab.data(), FC.Symtab.size()}, |
| {FC.Strtab.data(), FC.Strtab.size()}}; |
| return std::move(FC); |
| } |
| |
| Expected<FileContents> irsymtab::readBitcode(const BitcodeFileContents &BFC) { |
| if (BFC.Mods.empty()) |
| return make_error<StringError>("Bitcode file does not contain any modules", |
| inconvertibleErrorCode()); |
| |
| if (BFC.StrtabForSymtab.empty() || |
| BFC.Symtab.size() < sizeof(storage::Header)) |
| return upgrade(BFC.Mods); |
| |
| // We cannot use the regular reader to read the version and producer, because |
| // it will expect the header to be in the current format. The only thing we |
| // can rely on is that the version and producer will be present as the first |
| // struct elements. |
| auto *Hdr = reinterpret_cast<const storage::Header *>(BFC.Symtab.data()); |
| unsigned Version = Hdr->Version; |
| StringRef Producer = Hdr->Producer.get(BFC.StrtabForSymtab); |
| if (Version != storage::Header::kCurrentVersion || |
| Producer != kExpectedProducerName) |
| return upgrade(BFC.Mods); |
| |
| FileContents FC; |
| FC.TheReader = {{BFC.Symtab.data(), BFC.Symtab.size()}, |
| {BFC.StrtabForSymtab.data(), BFC.StrtabForSymtab.size()}}; |
| |
| // Finally, make sure that the number of modules in the symbol table matches |
| // the number of modules in the bitcode file. If they differ, it may mean that |
| // the bitcode file was created by binary concatenation, so we need to create |
| // a new symbol table from scratch. |
| if (FC.TheReader.getNumModules() != BFC.Mods.size()) |
| return upgrade(std::move(BFC.Mods)); |
| |
| return std::move(FC); |
| } |