MachO.cpp

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//===-------------- MachO.cpp - JIT linker function for MachO -------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// MachO jit-link function.
//
//===----------------------------------------------------------------------===//
 
#include "llvm/ExecutionEngine/JITLink/MachO.h"
 
#include "llvm/BinaryFormat/MachO.h"
#include "llvm/ExecutionEngine/JITLink/MachO_arm64.h"
#include "llvm/ExecutionEngine/JITLink/MachO_x86_64.h"
#include "llvm/Support/Format.h"
 
using namespace llvm;
 
#define DEBUG_TYPE "jitlink"
 
namespace llvm {
namespace jitlink {
 
Expected<std::unique_ptr<LinkGraph>>
createLinkGraphFromMachOObject(MemoryBufferRef ObjectBuffer,
                               std::shared_ptr<orc::SymbolStringPool> SSP) {
  StringRef Data = ObjectBuffer.getBuffer();
  if (Data.size() < 4)
    return make_error<JITLinkError>("Truncated MachO buffer \"" +
                                    ObjectBuffer.getBufferIdentifier() + "\"");
 
  uint32_t Magic;
  memcpy(&Magic, Data.data(), sizeof(uint32_t));
  LLVM_DEBUG({
    dbgs() << "jitLink_MachO: magic = " << format("0x%08" PRIx32, Magic)
           << ", identifier = \"" << ObjectBuffer.getBufferIdentifier()
           << "\"\n";
  });
 
  if (Magic == MachO::MH_MAGIC || Magic == MachO::MH_CIGAM)
    return make_error<JITLinkError>("MachO 32-bit platforms not supported");
  else if (Magic == MachO::MH_MAGIC_64 || Magic == MachO::MH_CIGAM_64) {
 
    if (Data.size() < sizeof(MachO::mach_header_64))
      return make_error<JITLinkError>("Truncated MachO buffer \"" +
                                      ObjectBuffer.getBufferIdentifier() +
                                      "\"");
 
    // Read the CPU type from the header.
    uint32_t CPUType;
    memcpy(&CPUType, Data.data() + 4, sizeof(uint32_t));
    if (Magic == MachO::MH_CIGAM_64)
      CPUType = llvm::byteswap<uint32_t>(CPUType);
 
    LLVM_DEBUG({
      dbgs() << "jitLink_MachO: cputype = " << format("0x%08" PRIx32, CPUType)
             << "\n";
    });
 
    switch (CPUType) {
    case MachO::CPU_TYPE_ARM64:
      return createLinkGraphFromMachOObject_arm64(ObjectBuffer, std::move(SSP));
    case MachO::CPU_TYPE_X86_64:
      return createLinkGraphFromMachOObject_x86_64(ObjectBuffer,
                                                   std::move(SSP));
    }
    return make_error<JITLinkError>("MachO-64 CPU type not valid");
  } else
    return make_error<JITLinkError>("Unrecognized MachO magic value");
}
 
void link_MachO(std::unique_ptr<LinkGraph> G,
                std::unique_ptr<JITLinkContext> Ctx) {
 
  switch (G->getTargetTriple().getArch()) {
  case Triple::aarch64:
    return link_MachO_arm64(std::move(G), std::move(Ctx));
  case Triple::x86_64:
    return link_MachO_x86_64(std::move(G), std::move(Ctx));
  default:
    Ctx->notifyFailed(make_error<JITLinkError>("MachO-64 CPU type not valid"));
    return;
  }
}
 
template <typename MachOHeaderType>
static Expected<Block &> createLocalHeaderBlock(LinkGraph &G, Section &Sec) {
  auto &B = G.createMutableContentBlock(Sec, sizeof(MachOHeaderType),
                                        orc::ExecutorAddr(), 8, 0, true);
  MachOHeaderType Hdr;
  Hdr.magic = G.getPointerSize() == 4 ? MachO::MH_MAGIC : MachO::MH_MAGIC_64;
  if (auto CPUType = MachO::getCPUType(G.getTargetTriple()))
    Hdr.cputype = *CPUType;
  else
    return CPUType.takeError();
  if (auto CPUSubType = MachO::getCPUSubType(G.getTargetTriple()))
    Hdr.cpusubtype = *CPUSubType;
  else
    return CPUSubType.takeError();
  Hdr.filetype = MachO::MH_OBJECT;
 
  if (G.getEndianness() != endianness::native)
    MachO::swapStruct(Hdr);
 
  memcpy(B.getAlreadyMutableContent().data(), &Hdr, sizeof(Hdr));
 
  return B;
}
 
Expected<Symbol &> getOrCreateLocalMachOHeader(LinkGraph &G) {
  StringRef LocalHeaderSectionName("__TEXT,__lcl_macho_hdr");
  Section *Sec = G.findSectionByName(LocalHeaderSectionName);
  if (Sec) {
    assert(Sec->blocks_size() == 1 && "Unexpected number of blocks");
    assert(Sec->symbols_size() == 1 && "Unexpected number of symbols");
    auto &Sym = **Sec->symbols().begin();
    assert(Sym.getOffset() == 0 && "Symbol not at start of header block");
    return Sym;
  }
 
  // Create the local header section, move all other sections up in the
  // section ordering to ensure that it's laid out first.
  for (auto &Sec : G.sections())
    Sec.setOrdinal(Sec.getOrdinal() + 1);
 
  Sec = &G.createSection(LocalHeaderSectionName, orc::MemProt::Read);
 
  Sec->setOrdinal(0);
 
  Block *B = nullptr;
  switch (G.getTargetTriple().getArch()) {
  case Triple::aarch64:
  case Triple::x86_64:
    if (auto BOrErr = createLocalHeaderBlock<MachO::mach_header_64>(G, *Sec))
      B = &*BOrErr;
    else
      return BOrErr.takeError();
    break;
  default:
    return make_error<JITLinkError>("Cannot create local Mach-O header for " +
                                    G.getName() + ": unsupported triple " +
                                    G.getTargetTriple().str());
  }
 
  return G.addAnonymousSymbol(*B, 0, B->getSize(), false, false);
}
 
} // end namespace jitlink
} // end namespace llvm