ObjectFileInterface.cpp

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//===------ ObjectFileInterface.cpp - MU interface utils for objects ------===//
//
// 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/ExecutionEngine/Orc/ObjectFileInterface.h"
#include "llvm/ExecutionEngine/JITSymbol.h"
#include "llvm/ExecutionEngine/Orc/Shared/ObjectFormats.h"
#include "llvm/Object/COFF.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Object/MachO.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Object/XCOFFObjectFile.h"
#include <optional>
 
#define DEBUG_TYPE "orc"
 
namespace llvm {
namespace orc {
 
void addInitSymbol(MaterializationUnit::Interface &I, ExecutionSession &ES,
                   StringRef ObjFileName) {
  assert(!I.InitSymbol && "I already has an init symbol");
  size_t Counter = 0;
 
  do {
    std::string InitSymString;
    raw_string_ostream(InitSymString)
        << "$." << ObjFileName << ".__inits." << Counter++;
    I.InitSymbol = ES.intern(InitSymString);
  } while (I.SymbolFlags.count(I.InitSymbol));
 
  I.SymbolFlags[I.InitSymbol] = JITSymbolFlags::MaterializationSideEffectsOnly;
}
 
static Expected<MaterializationUnit::Interface>
getMachOObjectFileSymbolInfo(ExecutionSession &ES,
                             const object::MachOObjectFile &Obj) {
  MaterializationUnit::Interface I;
 
  for (auto &Sym : Obj.symbols()) {
    Expected<uint32_t> SymFlagsOrErr = Sym.getFlags();
    if (!SymFlagsOrErr)
      // TODO: Test this error.
      return SymFlagsOrErr.takeError();
 
    // Skip symbols not defined in this object file.
    if (*SymFlagsOrErr & object::BasicSymbolRef::SF_Undefined)
      continue;
 
    // Skip symbols that are not global.
    if (!(*SymFlagsOrErr & object::BasicSymbolRef::SF_Global))
      continue;
 
    // Skip symbols that have type SF_File.
    if (auto SymType = Sym.getType()) {
      if (*SymType == object::SymbolRef::ST_File)
        continue;
    } else
      return SymType.takeError();
 
    auto Name = Sym.getName();
    if (!Name)
      return Name.takeError();
    auto SymFlags = JITSymbolFlags::fromObjectSymbol(Sym);
    if (!SymFlags)
      return SymFlags.takeError();
 
    // Strip the 'exported' flag from MachO linker-private symbols.
    if (Name->starts_with("l"))
      *SymFlags &= ~JITSymbolFlags::Exported;
 
    I.SymbolFlags[ES.intern(*Name)] = std::move(*SymFlags);
  }
 
  for (auto &Sec : Obj.sections()) {
    auto SecType = Obj.getSectionType(Sec);
    if ((SecType & MachO::SECTION_TYPE) == MachO::S_MOD_INIT_FUNC_POINTERS) {
      addInitSymbol(I, ES, Obj.getFileName());
      break;
    }
    auto SegName = Obj.getSectionFinalSegmentName(Sec.getRawDataRefImpl());
    auto SecName = cantFail(Obj.getSectionName(Sec.getRawDataRefImpl()));
    if (isMachOInitializerSection(SegName, SecName)) {
      addInitSymbol(I, ES, Obj.getFileName());
      break;
    }
  }
 
  return I;
}
 
static Expected<MaterializationUnit::Interface>
getELFObjectFileSymbolInfo(ExecutionSession &ES,
                           const object::ELFObjectFileBase &Obj) {
  MaterializationUnit::Interface I;
 
  for (auto &Sym : Obj.symbols()) {
    Expected<uint32_t> SymFlagsOrErr = Sym.getFlags();
    if (!SymFlagsOrErr)
      // TODO: Test this error.
      return SymFlagsOrErr.takeError();
 
    // Skip symbols not defined in this object file.
    if (*SymFlagsOrErr & object::BasicSymbolRef::SF_Undefined)
      continue;
 
    // Skip symbols that are not global.
    if (!(*SymFlagsOrErr & object::BasicSymbolRef::SF_Global))
      continue;
 
    // Skip symbols that have type SF_File.
    if (auto SymType = Sym.getType()) {
      if (*SymType == object::SymbolRef::ST_File)
        continue;
    } else
      return SymType.takeError();
 
    auto Name = Sym.getName();
    if (!Name)
      return Name.takeError();
 
    auto SymFlags = JITSymbolFlags::fromObjectSymbol(Sym);
    if (!SymFlags)
      return SymFlags.takeError();
 
    // ELF STB_GNU_UNIQUE should map to Weak for ORC.
    if (Sym.getBinding() == ELF::STB_GNU_UNIQUE)
      *SymFlags |= JITSymbolFlags::Weak;
 
    I.SymbolFlags[ES.intern(std::move(*Name))] = std::move(*SymFlags);
  }
 
  SymbolStringPtr InitSymbol;
  for (auto &Sec : Obj.sections()) {
    if (auto SecName = Sec.getName()) {
      if (isELFInitializerSection(*SecName)) {
        addInitSymbol(I, ES, Obj.getFileName());
        break;
      }
    }
  }
 
  return I;
}
 
static Expected<MaterializationUnit::Interface>
getCOFFObjectFileSymbolInfo(ExecutionSession &ES,
                            const object::COFFObjectFile &Obj) {
  MaterializationUnit::Interface I;
  std::vector<std::optional<object::coff_aux_section_definition>> ComdatDefs(
      Obj.getNumberOfSections() + 1);
  for (auto &Sym : Obj.symbols()) {
    Expected<uint32_t> SymFlagsOrErr = Sym.getFlags();
    if (!SymFlagsOrErr)
      // TODO: Test this error.
      return SymFlagsOrErr.takeError();
 
    // Handle comdat symbols
    auto COFFSym = Obj.getCOFFSymbol(Sym);
    bool IsWeak = false;
    if (auto *Def = COFFSym.getSectionDefinition()) {
      auto Sec = Obj.getSection(COFFSym.getSectionNumber());
      if (!Sec)
        return Sec.takeError();
      if (((*Sec)->Characteristics & COFF::IMAGE_SCN_LNK_COMDAT) &&
          Def->Selection != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
        ComdatDefs[COFFSym.getSectionNumber()] = *Def;
        continue;
      }
    }
    if (!COFF::isReservedSectionNumber(COFFSym.getSectionNumber()) &&
        ComdatDefs[COFFSym.getSectionNumber()]) {
      auto Def = ComdatDefs[COFFSym.getSectionNumber()];
      if (Def->Selection != COFF::IMAGE_COMDAT_SELECT_NODUPLICATES) {
        IsWeak = true;
      }
      ComdatDefs[COFFSym.getSectionNumber()] = std::nullopt;
    } else {
      // Skip symbols not defined in this object file.
      if (*SymFlagsOrErr & object::BasicSymbolRef::SF_Undefined)
        continue;
    }
 
    // Skip symbols that are not global.
    if (!(*SymFlagsOrErr & object::BasicSymbolRef::SF_Global))
      continue;
 
    // Skip symbols that have type SF_File.
    if (auto SymType = Sym.getType()) {
      if (*SymType == object::SymbolRef::ST_File)
        continue;
    } else
      return SymType.takeError();
 
    auto Name = Sym.getName();
    if (!Name)
      return Name.takeError();
 
    auto SymFlags = JITSymbolFlags::fromObjectSymbol(Sym);
    if (!SymFlags)
      return SymFlags.takeError();
    *SymFlags |= JITSymbolFlags::Exported;
 
    // Weak external is always a function
    if (COFFSym.isWeakExternal())
      *SymFlags |= JITSymbolFlags::Callable;
 
    if (IsWeak)
      *SymFlags |= JITSymbolFlags::Weak;
 
    I.SymbolFlags[ES.intern(*Name)] = std::move(*SymFlags);
  }
 
  SymbolStringPtr InitSymbol;
  for (auto &Sec : Obj.sections()) {
    if (auto SecName = Sec.getName()) {
      if (isCOFFInitializerSection(*SecName)) {
        addInitSymbol(I, ES, Obj.getFileName());
        break;
      }
    } else
      return SecName.takeError();
  }
 
  return I;
}
 
Expected<MaterializationUnit::Interface>
getXCOFFObjectFileSymbolInfo(ExecutionSession &ES,
                             const object::ObjectFile &Obj) {
 
  MaterializationUnit::Interface I;
 
  for (auto &Sym : Obj.symbols()) {
    Expected<uint32_t> SymFlagsOrErr = Sym.getFlags();
    if (!SymFlagsOrErr)
      return SymFlagsOrErr.takeError();
    uint32_t Flags = *SymFlagsOrErr;
 
    // Skip undefined, non global and ST_File
    if (Flags & object::SymbolRef::SF_Undefined)
      continue;
    if (!(Flags & object::SymbolRef::SF_Global))
      continue;
 
    auto SymbolType = Sym.getType();
    if (!SymbolType)
      return SymbolType.takeError();
 
    if (*SymbolType == object::SymbolRef::ST_File)
      continue;
 
    auto Name = Sym.getName();
    if (!Name)
      return Name.takeError();
    auto SymFlags = JITSymbolFlags::fromObjectSymbol(Sym);
    if (!SymFlags)
      return SymFlags.takeError();
 
    // TODO: Revisit symbol visibility
    // On AIX, symbols with C_EXT and C_WEAKEXT symbols have no specified
    // visibility are considered to have Default scope for LinkGraph. When the
    // object is not a DSO, symbol visibility is not specified. In the absence
    // of an Export List, its reasonable to minimic roughly the behaviour of
    // -bexpall or CreateExportList.
    *SymFlags |= JITSymbolFlags::Exported;
 
    I.SymbolFlags[ES.intern(std::move(*Name))] = std::move(*SymFlags);
  }
  // TODO: Find all initialization symbols for c++ static initializers
  return I;
}
 
Expected<MaterializationUnit::Interface>
getGenericObjectFileSymbolInfo(ExecutionSession &ES,
                               const object::ObjectFile &Obj) {
  MaterializationUnit::Interface I;
 
  for (auto &Sym : Obj.symbols()) {
    Expected<uint32_t> SymFlagsOrErr = Sym.getFlags();
    if (!SymFlagsOrErr)
      // TODO: Test this error.
      return SymFlagsOrErr.takeError();
 
    // Skip symbols not defined in this object file.
    if (*SymFlagsOrErr & object::BasicSymbolRef::SF_Undefined)
      continue;
 
    // Skip symbols that are not global.
    if (!(*SymFlagsOrErr & object::BasicSymbolRef::SF_Global))
      continue;
 
    // Skip symbols that have type SF_File.
    if (auto SymType = Sym.getType()) {
      if (*SymType == object::SymbolRef::ST_File)
        continue;
    } else
      return SymType.takeError();
 
    auto Name = Sym.getName();
    if (!Name)
      return Name.takeError();
 
    auto SymFlags = JITSymbolFlags::fromObjectSymbol(Sym);
    if (!SymFlags)
      return SymFlags.takeError();
 
    I.SymbolFlags[ES.intern(*Name)] = std::move(*SymFlags);
  }
 
  return I;
}
 
Expected<MaterializationUnit::Interface>
getObjectFileInterface(ExecutionSession &ES, MemoryBufferRef ObjBuffer) {
  auto Obj = object::ObjectFile::createObjectFile(ObjBuffer);
 
  if (!Obj)
    return Obj.takeError();
 
  if (auto *MachOObj = dyn_cast<object::MachOObjectFile>(Obj->get()))
    return getMachOObjectFileSymbolInfo(ES, *MachOObj);
  else if (auto *ELFObj = dyn_cast<object::ELFObjectFileBase>(Obj->get()))
    return getELFObjectFileSymbolInfo(ES, *ELFObj);
  else if (auto *COFFObj = dyn_cast<object::COFFObjectFile>(Obj->get()))
    return getCOFFObjectFileSymbolInfo(ES, *COFFObj);
  else if (auto *XCOFFObj = dyn_cast<object::XCOFFObjectFile>(Obj->get()))
    return getXCOFFObjectFileSymbolInfo(ES, *XCOFFObj);
 
  return getGenericObjectFileSymbolInfo(ES, **Obj);
}
 
} // End namespace orc.
} // End namespace llvm.