tools/llvm-objcopy/COFF/COFFObjcopy.cpp

   1 //===- COFFObjcopy.cpp ----------------------------------------------------===//
   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-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "COFFObjcopy.h"
  10 #include "Buffer.h"
  11 #include "CopyConfig.h"
  12 #include "Object.h"
  13 #include "Reader.h"
  14 #include "Writer.h"
  15 #include "llvm-objcopy.h"
  16
  17 #include "llvm/Object/Binary.h"
  18 #include "llvm/Object/COFF.h"
  19 #include "llvm/Support/Errc.h"
  20 #include "llvm/Support/JamCRC.h"
  21 #include "llvm/Support/Path.h"
  22 #include <cassert>
  23
  24 namespace llvm {
  25 namespace objcopy {
  26 namespace coff {
  27
  28 using namespace object;
  29 using namespace COFF;
  30
  31 static bool isDebugSection(const Section &Sec) {
  32   return Sec.Name.startswith(".debug");
  33 }
  34
  35 static uint64_t getNextRVA(const Object &Obj) {
  36   if (Obj.getSections().empty())
  37     return 0;
  38   const Section &Last = Obj.getSections().back();
  39   return alignTo(Last.Header.VirtualAddress + Last.Header.VirtualSize,
  40                  Obj.IsPE ? Obj.PeHeader.SectionAlignment : 1);
  41 }
  42
  43 static uint32_t getCRC32(StringRef Data) {
  44   JamCRC CRC;
  45   CRC.update(ArrayRef<char>(Data.data(), Data.size()));
  46   // The CRC32 value needs to be complemented because the JamCRC dosn't
  47   // finalize the CRC32 value. It also dosn't negate the initial CRC32 value
  48   // but it starts by default at 0xFFFFFFFF which is the complement of zero.
  49   return ~CRC.getCRC();
  50 }
  51
  52 static std::vector<uint8_t> createGnuDebugLinkSectionContents(StringRef File) {
  53   ErrorOr<std::unique_ptr<MemoryBuffer>> LinkTargetOrErr =
  54       MemoryBuffer::getFile(File);
  55   if (!LinkTargetOrErr)
  56     error("'" + File + "': " + LinkTargetOrErr.getError().message());
  57   auto LinkTarget = std::move(*LinkTargetOrErr);
  58   uint32_t CRC32 = getCRC32(LinkTarget->getBuffer());
  59
  60   StringRef FileName = sys::path::filename(File);
  61   size_t CRCPos = alignTo(FileName.size() + 1, 4);
  62   std::vector<uint8_t> Data(CRCPos + 4);
  63   memcpy(Data.data(), FileName.data(), FileName.size());
  64   support::endian::write32le(Data.data() + CRCPos, CRC32);
  65   return Data;
  66 }
  67
  68 // Adds named section with given contents to the object.
  69 static void addSection(Object &Obj, StringRef Name, ArrayRef<uint8_t> Contents,
  70                        uint32_t Characteristics) {
  71   bool NeedVA = Characteristics & (IMAGE_SCN_MEM_EXECUTE | IMAGE_SCN_MEM_READ |
  72                                    IMAGE_SCN_MEM_WRITE);
  73
  74   Section Sec;
  75   Sec.setOwnedContents(Contents);
  76   Sec.Name = Name;
  77   Sec.Header.VirtualSize = NeedVA ? Sec.getContents().size() : 0u;
  78   Sec.Header.VirtualAddress = NeedVA ? getNextRVA(Obj) : 0u;
  79   Sec.Header.SizeOfRawData =
  80       NeedVA ? alignTo(Sec.Header.VirtualSize,
  81                        Obj.IsPE ? Obj.PeHeader.FileAlignment : 1)
  82              : Sec.getContents().size();
  83   // Sec.Header.PointerToRawData is filled in by the writer.
  84   Sec.Header.PointerToRelocations = 0;
  85   Sec.Header.PointerToLinenumbers = 0;
  86   // Sec.Header.NumberOfRelocations is filled in by the writer.
  87   Sec.Header.NumberOfLinenumbers = 0;
  88   Sec.Header.Characteristics = Characteristics;
  89
  90   Obj.addSections(Sec);
  91 }
  92
  93 static void addGnuDebugLink(Object &Obj, StringRef DebugLinkFile) {
  94   std::vector<uint8_t> Contents =
  95       createGnuDebugLinkSectionContents(DebugLinkFile);
  96   addSection(Obj, ".gnu_debuglink", Contents,
  97              IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ |
  98                  IMAGE_SCN_MEM_DISCARDABLE);
  99 }
 100
 101 static Error handleArgs(const CopyConfig &Config, Object &Obj) {
 102   // Perform the actual section removals.
 103   Obj.removeSections([&Config](const Section &Sec) {
 104     // Contrary to --only-keep-debug, --only-section fully removes sections that
 105     // aren't mentioned.
 106     if (!Config.OnlySection.empty() && !Config.OnlySection.matches(Sec.Name))
 107       return true;
 108
 109     if (Config.StripDebug || Config.StripAll || Config.StripAllGNU ||
 110         Config.DiscardMode == DiscardType::All || Config.StripUnneeded) {
 111       if (isDebugSection(Sec) &&
 112           (Sec.Header.Characteristics & IMAGE_SCN_MEM_DISCARDABLE) != 0)
 113         return true;
 114     }
 115
 116     if (Config.ToRemove.matches(Sec.Name))
 117       return true;
 118
 119     return false;
 120   });
 121
 122   if (Config.OnlyKeepDebug) {
 123     // For --only-keep-debug, we keep all other sections, but remove their
 124     // content. The VirtualSize field in the section header is kept intact.
 125     Obj.truncateSections([](const Section &Sec) {
 126       return !isDebugSection(Sec) && Sec.Name != ".buildid" &&
 127              ((Sec.Header.Characteristics &
 128                (IMAGE_SCN_CNT_CODE | IMAGE_SCN_CNT_INITIALIZED_DATA)) != 0);
 129     });
 130   }
 131
 132   // StripAll removes all symbols and thus also removes all relocations.
 133   if (Config.StripAll || Config.StripAllGNU)
 134     for (Section &Sec : Obj.getMutableSections())
 135       Sec.Relocs.clear();
 136
 137   // If we need to do per-symbol removals, initialize the Referenced field.
 138   if (Config.StripUnneeded || Config.DiscardMode == DiscardType::All ||
 139       !Config.SymbolsToRemove.empty())
 140     if (Error E = Obj.markSymbols())
 141       return E;
 142
 143   // Actually do removals of symbols.
 144   Obj.removeSymbols([&](const Symbol &Sym) {
 145     // For StripAll, all relocations have been stripped and we remove all
 146     // symbols.
 147     if (Config.StripAll || Config.StripAllGNU)
 148       return true;
 149
 150     if (Config.SymbolsToRemove.matches(Sym.Name)) {
 151       // Explicitly removing a referenced symbol is an error.
 152       if (Sym.Referenced)
 153         reportError(Config.OutputFilename,
 154                     createStringError(llvm::errc::invalid_argument,
 155                                       "not stripping symbol '%s' because it is "
 156                                       "named in a relocation",
 157                                       Sym.Name.str().c_str()));
 158       return true;
 159     }
 160
 161     if (!Sym.Referenced) {
 162       // With --strip-unneeded, GNU objcopy removes all unreferenced local
 163       // symbols, and any unreferenced undefined external.
 164       // With --strip-unneeded-symbol we strip only specific unreferenced
 165       // local symbol instead of removing all of such.
 166       if (Sym.Sym.StorageClass == IMAGE_SYM_CLASS_STATIC ||
 167           Sym.Sym.SectionNumber == 0)
 168         if (Config.StripUnneeded ||
 169             Config.UnneededSymbolsToRemove.matches(Sym.Name))
 170           return true;
 171
 172       // GNU objcopy keeps referenced local symbols and external symbols
 173       // if --discard-all is set, similar to what --strip-unneeded does,
 174       // but undefined local symbols are kept when --discard-all is set.
 175       if (Config.DiscardMode == DiscardType::All &&
 176           Sym.Sym.StorageClass == IMAGE_SYM_CLASS_STATIC &&
 177           Sym.Sym.SectionNumber != 0)
 178         return true;
 179     }
 180
 181     return false;
 182   });
 183
 184   for (const auto &Flag : Config.AddSection) {
 185     StringRef SecName, FileName;
 186     std::tie(SecName, FileName) = Flag.split("=");
 187
 188     auto BufOrErr = MemoryBuffer::getFile(FileName);
 189     if (!BufOrErr)
 190       return createFileError(FileName, errorCodeToError(BufOrErr.getError()));
 191     auto Buf = std::move(*BufOrErr);
 192
 193     addSection(
 194         Obj, SecName,
 195         makeArrayRef(reinterpret_cast<const uint8_t *>(Buf->getBufferStart()),
 196                      Buf->getBufferSize()),
 197         IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_ALIGN_1BYTES);
 198   }
 199
 200   if (!Config.AddGnuDebugLink.empty())
 201     addGnuDebugLink(Obj, Config.AddGnuDebugLink);
 202
 203   if (Config.AllowBrokenLinks || !Config.BuildIdLinkDir.empty() ||
 204       Config.BuildIdLinkInput || Config.BuildIdLinkOutput ||
 205       !Config.SplitDWO.empty() || !Config.SymbolsPrefix.empty() ||
 206       !Config.AllocSectionsPrefix.empty() || !Config.DumpSection.empty() ||
 207       !Config.KeepSection.empty() || Config.NewSymbolVisibility ||
 208       !Config.SymbolsToGlobalize.empty() || !Config.SymbolsToKeep.empty() ||
 209       !Config.SymbolsToLocalize.empty() || !Config.SymbolsToWeaken.empty() ||
 210       !Config.SymbolsToKeepGlobal.empty() || !Config.SectionsToRename.empty() ||
 211       !Config.SetSectionFlags.empty() || !Config.SymbolsToRename.empty() ||
 212       Config.ExtractDWO || Config.KeepFileSymbols || Config.LocalizeHidden ||
 213       Config.PreserveDates || Config.StripDWO || Config.StripNonAlloc ||
 214       Config.StripSections || Config.Weaken || Config.DecompressDebugSections ||
 215       Config.DiscardMode == DiscardType::Locals ||
 216       !Config.SymbolsToAdd.empty() || Config.EntryExpr) {
 217     return createStringError(llvm::errc::invalid_argument,
 218                              "option not supported by llvm-objcopy for COFF");
 219   }
 220
 221   return Error::success();
 222 }
 223
 224 Error executeObjcopyOnBinary(const CopyConfig &Config, COFFObjectFile &In,
 225                              Buffer &Out) {
 226   COFFReader Reader(In);
 227   Expected<std::unique_ptr<Object>> ObjOrErr = Reader.create();
 228   if (!ObjOrErr)
 229     return createFileError(Config.InputFilename, ObjOrErr.takeError());
 230   Object *Obj = ObjOrErr->get();
 231   assert(Obj && "Unable to deserialize COFF object");
 232   if (Error E = handleArgs(Config, *Obj))
 233     return createFileError(Config.InputFilename, std::move(E));
 234   COFFWriter Writer(*Obj, Out);
 235   if (Error E = Writer.write())
 236     return createFileError(Config.OutputFilename, std::move(E));
 237   return Error::success();
 238 }
 239
 240 } // end namespace coff
 241 } // end namespace objcopy
 242 } // end namespace llvm