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 static void addGnuDebugLink(Object &Obj, StringRef DebugLinkFile) {
  69   uint32_t StartRVA = getNextRVA(Obj);
  70
  71   std::vector<Section> Sections;
  72   Section Sec;
  73   Sec.setOwnedContents(createGnuDebugLinkSectionContents(DebugLinkFile));
  74   Sec.Name = ".gnu_debuglink";
  75   Sec.Header.VirtualSize = Sec.getContents().size();
  76   Sec.Header.VirtualAddress = StartRVA;
  77   Sec.Header.SizeOfRawData = alignTo(Sec.Header.VirtualSize,
  78                                      Obj.IsPE ? Obj.PeHeader.FileAlignment : 1);
  79   // Sec.Header.PointerToRawData is filled in by the writer.
  80   Sec.Header.PointerToRelocations = 0;
  81   Sec.Header.PointerToLinenumbers = 0;
  82   // Sec.Header.NumberOfRelocations is filled in by the writer.
  83   Sec.Header.NumberOfLinenumbers = 0;
  84   Sec.Header.Characteristics = IMAGE_SCN_CNT_INITIALIZED_DATA |
  85                                IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_DISCARDABLE;
  86   Sections.push_back(Sec);
  87   Obj.addSections(Sections);
  88 }
  89
  90 static Error handleArgs(const CopyConfig &Config, Object &Obj) {
  91   // Perform the actual section removals.
  92   Obj.removeSections([&Config](const Section &Sec) {
  93     // Contrary to --only-keep-debug, --only-section fully removes sections that
  94     // aren't mentioned.
  95     if (!Config.OnlySection.empty() &&
  96         !is_contained(Config.OnlySection, Sec.Name))
  97       return true;
  98
  99     if (Config.StripDebug || Config.StripAll || Config.StripAllGNU ||
 100         Config.DiscardMode == DiscardType::All || Config.StripUnneeded) {
 101       if (isDebugSection(Sec) &&
 102           (Sec.Header.Characteristics & IMAGE_SCN_MEM_DISCARDABLE) != 0)
 103         return true;
 104     }
 105
 106     if (is_contained(Config.ToRemove, Sec.Name))
 107       return true;
 108
 109     return false;
 110   });
 111
 112   if (Config.OnlyKeepDebug) {
 113     // For --only-keep-debug, we keep all other sections, but remove their
 114     // content. The VirtualSize field in the section header is kept intact.
 115     Obj.truncateSections([](const Section &Sec) {
 116       return !isDebugSection(Sec) && Sec.Name != ".buildid" &&
 117              ((Sec.Header.Characteristics &
 118                (IMAGE_SCN_CNT_CODE | IMAGE_SCN_CNT_INITIALIZED_DATA)) != 0);
 119     });
 120   }
 121
 122   // StripAll removes all symbols and thus also removes all relocations.
 123   if (Config.StripAll || Config.StripAllGNU)
 124     for (Section &Sec : Obj.getMutableSections())
 125       Sec.Relocs.clear();
 126
 127   // If we need to do per-symbol removals, initialize the Referenced field.
 128   if (Config.StripUnneeded || Config.DiscardMode == DiscardType::All ||
 129       !Config.SymbolsToRemove.empty())
 130     if (Error E = Obj.markSymbols())
 131       return E;
 132
 133   // Actually do removals of symbols.
 134   Obj.removeSymbols([&](const Symbol &Sym) {
 135     // For StripAll, all relocations have been stripped and we remove all
 136     // symbols.
 137     if (Config.StripAll || Config.StripAllGNU)
 138       return true;
 139
 140     if (is_contained(Config.SymbolsToRemove, Sym.Name)) {
 141       // Explicitly removing a referenced symbol is an error.
 142       if (Sym.Referenced)
 143         reportError(Config.OutputFilename,
 144                     createStringError(llvm::errc::invalid_argument,
 145                                       "not stripping symbol '%s' because it is "
 146                                       "named in a relocation",
 147                                       Sym.Name.str().c_str()));
 148       return true;
 149     }
 150
 151     if (!Sym.Referenced) {
 152       // With --strip-unneeded, GNU objcopy removes all unreferenced local
 153       // symbols, and any unreferenced undefined external.
 154       // With --strip-unneeded-symbol we strip only specific unreferenced
 155       // local symbol instead of removing all of such.
 156       if (Sym.Sym.StorageClass == IMAGE_SYM_CLASS_STATIC ||
 157           Sym.Sym.SectionNumber == 0)
 158         if (Config.StripUnneeded ||
 159             is_contained(Config.UnneededSymbolsToRemove, Sym.Name))
 160           return true;
 161
 162       // GNU objcopy keeps referenced local symbols and external symbols
 163       // if --discard-all is set, similar to what --strip-unneeded does,
 164       // but undefined local symbols are kept when --discard-all is set.
 165       if (Config.DiscardMode == DiscardType::All &&
 166           Sym.Sym.StorageClass == IMAGE_SYM_CLASS_STATIC &&
 167           Sym.Sym.SectionNumber != 0)
 168         return true;
 169     }
 170
 171     return false;
 172   });
 173
 174   if (!Config.AddGnuDebugLink.empty())
 175     addGnuDebugLink(Obj, Config.AddGnuDebugLink);
 176
 177   if (Config.AllowBrokenLinks || !Config.BuildIdLinkDir.empty() ||
 178       Config.BuildIdLinkInput || Config.BuildIdLinkOutput ||
 179       !Config.SplitDWO.empty() || !Config.SymbolsPrefix.empty() ||
 180       !Config.AllocSectionsPrefix.empty() || !Config.AddSection.empty() ||
 181       !Config.DumpSection.empty() || !Config.KeepSection.empty() ||
 182       !Config.SymbolsToGlobalize.empty() || !Config.SymbolsToKeep.empty() ||
 183       !Config.SymbolsToLocalize.empty() || !Config.SymbolsToWeaken.empty() ||
 184       !Config.SymbolsToKeepGlobal.empty() || !Config.SectionsToRename.empty() ||
 185       !Config.SetSectionFlags.empty() || !Config.SymbolsToRename.empty() ||
 186       Config.ExtractDWO || Config.KeepFileSymbols || Config.LocalizeHidden ||
 187       Config.PreserveDates || Config.StripDWO || Config.StripNonAlloc ||
 188       Config.StripSections || Config.Weaken || Config.DecompressDebugSections ||
 189       Config.DiscardMode == DiscardType::Locals ||
 190       !Config.SymbolsToAdd.empty() || Config.EntryExpr) {
 191     return createStringError(llvm::errc::invalid_argument,
 192                              "option not supported by llvm-objcopy for COFF");
 193   }
 194
 195   return Error::success();
 196 }
 197
 198 Error executeObjcopyOnBinary(const CopyConfig &Config, COFFObjectFile &In,
 199                              Buffer &Out) {
 200   COFFReader Reader(In);
 201   Expected<std::unique_ptr<Object>> ObjOrErr = Reader.create();
 202   if (!ObjOrErr)
 203     return createFileError(Config.InputFilename, ObjOrErr.takeError());
 204   Object *Obj = ObjOrErr->get();
 205   assert(Obj && "Unable to deserialize COFF object");
 206   if (Error E = handleArgs(Config, *Obj))
 207     return createFileError(Config.InputFilename, std::move(E));
 208   COFFWriter Writer(*Obj, Out);
 209   if (Error E = Writer.write())
 210     return createFileError(Config.OutputFilename, std::move(E));
 211   return Error::success();
 212 }
 213
 214 } // end namespace coff
 215 } // end namespace objcopy
 216 } // end namespace llvm