lld/ELF/MapFile.cpp

   1 //===- MapFile.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 // This file implements the -Map option. It shows lists in order and
  10 // hierarchically the output sections, input sections, input files and
  11 // symbol:
  12 //
  13 //   Address  Size     Align Out     In      Symbol
  14 //   00201000 00000015     4 .text
  15 //   00201000 0000000e     4         test.o:(.text)
  16 //   0020100e 00000000     0                 local
  17 //   00201005 00000000     0                 f(int)
  18 //
  19 //===----------------------------------------------------------------------===//
  20
  21 #include "MapFile.h"
  22 #include "InputFiles.h"
  23 #include "LinkerScript.h"
  24 #include "OutputSections.h"
  25 #include "Symbols.h"
  26 #include "SyntheticSections.h"
  27 #include "llvm/ADT/MapVector.h"
  28 #include "llvm/ADT/SetVector.h"
  29 #include "llvm/ADT/SmallPtrSet.h"
  30 #include "llvm/Support/FileSystem.h"
  31 #include "llvm/Support/Parallel.h"
  32 #include "llvm/Support/TimeProfiler.h"
  33 #include "llvm/Support/raw_ostream.h"
  34
  35 using namespace llvm;
  36 using namespace llvm::object;
  37 using namespace lld;
  38 using namespace lld::elf;
  39
  40 using SymbolMapTy = DenseMap<const SectionBase *,
  41                              SmallVector<std::pair<Defined *, uint64_t>, 0>>;
  42
  43 static constexpr char indent8[] = "        ";          // 8 spaces
  44 static constexpr char indent16[] = "                "; // 16 spaces
  45
  46 // Print out the first three columns of a line.
  47 static void writeHeader(raw_ostream &os, uint64_t vma, uint64_t lma,
  48                         uint64_t size, uint64_t align) {
  49   if (config->is64)
  50     os << format("%16llx %16llx %8llx %5lld ", vma, lma, size, align);
  51   else
  52     os << format("%8llx %8llx %8llx %5lld ", vma, lma, size, align);
  53 }
  54
  55 // Returns a list of all symbols that we want to print out.
  56 static std::vector<Defined *> getSymbols() {
  57   std::vector<Defined *> v;
  58   for (ELFFileBase *file : ctx.objectFiles)
  59     for (Symbol *b : file->getSymbols())
  60       if (auto *dr = dyn_cast<Defined>(b))
  61         if (!dr->isSection() && dr->section && dr->section->isLive() &&
  62             (dr->file == file || dr->hasFlag(NEEDS_COPY) || dr->section->bss))
  63           v.push_back(dr);
  64   return v;
  65 }
  66
  67 // Returns a map from sections to their symbols.
  68 static SymbolMapTy getSectionSyms(ArrayRef<Defined *> syms) {
  69   SymbolMapTy ret;
  70   for (Defined *dr : syms)
  71     ret[dr->section].emplace_back(dr, dr->getVA());
  72
  73   // Sort symbols by address. We want to print out symbols in the
  74   // order in the output file rather than the order they appeared
  75   // in the input files.
  76   SmallPtrSet<Defined *, 4> set;
  77   for (auto &it : ret) {
  78     // Deduplicate symbols which need a canonical PLT entry/copy relocation.
  79     set.clear();
  80     llvm::erase_if(it.second, [&](std::pair<Defined *, uint64_t> a) {
  81       return !set.insert(a.first).second;
  82     });
  83
  84     llvm::stable_sort(it.second, llvm::less_second());
  85   }
  86   return ret;
  87 }
  88
  89 // Construct a map from symbols to their stringified representations.
  90 // Demangling symbols (which is what toString() does) is slow, so
  91 // we do that in batch using parallel-for.
  92 static DenseMap<Symbol *, std::string>
  93 getSymbolStrings(ArrayRef<Defined *> syms) {
  94   auto strs = std::make_unique<std::string[]>(syms.size());
  95   parallelFor(0, syms.size(), [&](size_t i) {
  96     raw_string_ostream os(strs[i]);
  97     OutputSection *osec = syms[i]->getOutputSection();
  98     uint64_t vma = syms[i]->getVA();
  99     uint64_t lma = osec ? osec->getLMA() + vma - osec->getVA(0) : 0;
 100     writeHeader(os, vma, lma, syms[i]->getSize(), 1);
 101     os << indent16 << toString(*syms[i]);
 102   });
 103
 104   DenseMap<Symbol *, std::string> ret;
 105   for (size_t i = 0, e = syms.size(); i < e; ++i)
 106     ret[syms[i]] = std::move(strs[i]);
 107   return ret;
 108 }
 109
 110 // Print .eh_frame contents. Since the section consists of EhSectionPieces,
 111 // we need a specialized printer for that section.
 112 //
 113 // .eh_frame tend to contain a lot of section pieces that are contiguous
 114 // both in input file and output file. Such pieces are squashed before
 115 // being displayed to make output compact.
 116 static void printEhFrame(raw_ostream &os, const EhFrameSection *sec) {
 117   std::vector<EhSectionPiece> pieces;
 118
 119   auto add = [&](const EhSectionPiece &p) {
 120     // If P is adjacent to Last, squash the two.
 121     if (!pieces.empty()) {
 122       EhSectionPiece &last = pieces.back();
 123       if (last.sec == p.sec && last.inputOff + last.size == p.inputOff &&
 124           last.outputOff + last.size == (unsigned)p.outputOff) {
 125         last.size += p.size;
 126         return;
 127       }
 128     }
 129     pieces.push_back(p);
 130   };
 131
 132   // Gather section pieces.
 133   for (const CieRecord *rec : sec->getCieRecords()) {
 134     add(*rec->cie);
 135     for (const EhSectionPiece *fde : rec->fdes)
 136       add(*fde);
 137   }
 138
 139   // Print out section pieces.
 140   const OutputSection *osec = sec->getOutputSection();
 141   for (EhSectionPiece &p : pieces) {
 142     writeHeader(os, osec->addr + p.outputOff, osec->getLMA() + p.outputOff,
 143                 p.size, 1);
 144     os << indent8 << toString(p.sec->file) << ":(" << p.sec->name << "+0x"
 145        << Twine::utohexstr(p.inputOff) + ")\n";
 146   }
 147 }
 148
 149 static void writeMapFile(raw_fd_ostream &os) {
 150   // Collect symbol info that we want to print out.
 151   std::vector<Defined *> syms = getSymbols();
 152   SymbolMapTy sectionSyms = getSectionSyms(syms);
 153   DenseMap<Symbol *, std::string> symStr = getSymbolStrings(syms);
 154
 155   // Print out the header line.
 156   int w = config->is64 ? 16 : 8;
 157   os << right_justify("VMA", w) << ' ' << right_justify("LMA", w)
 158      << "     Size Align Out     In      Symbol\n";
 159
 160   OutputSection *osec = nullptr;
 161   for (SectionCommand *cmd : script->sectionCommands) {
 162     if (auto *assign = dyn_cast<SymbolAssignment>(cmd)) {
 163       if (assign->provide && !assign->sym)
 164         continue;
 165       uint64_t lma = osec ? osec->getLMA() + assign->addr - osec->getVA(0) : 0;
 166       writeHeader(os, assign->addr, lma, assign->size, 1);
 167       os << assign->commandString << '\n';
 168       continue;
 169     }
 170
 171     osec = &cast<OutputDesc>(cmd)->osec;
 172     writeHeader(os, osec->addr, osec->getLMA(), osec->size, osec->addralign);
 173     os << osec->name << '\n';
 174
 175     // Dump symbols for each input section.
 176     for (SectionCommand *subCmd : osec->commands) {
 177       if (auto *isd = dyn_cast<InputSectionDescription>(subCmd)) {
 178         for (InputSection *isec : isd->sections) {
 179           if (auto *ehSec = dyn_cast<EhFrameSection>(isec)) {
 180             printEhFrame(os, ehSec);
 181             continue;
 182           }
 183
 184           writeHeader(os, isec->getVA(), osec->getLMA() + isec->outSecOff,
 185                       isec->getSize(), isec->addralign);
 186           os << indent8 << toString(isec) << '\n';
 187           for (Symbol *sym : llvm::make_first_range(sectionSyms[isec]))
 188             os << symStr[sym] << '\n';
 189         }
 190         continue;
 191       }
 192
 193       if (auto *data = dyn_cast<ByteCommand>(subCmd)) {
 194         writeHeader(os, osec->addr + data->offset,
 195                     osec->getLMA() + data->offset, data->size, 1);
 196         os << indent8 << data->commandString << '\n';
 197         continue;
 198       }
 199
 200       if (auto *assign = dyn_cast<SymbolAssignment>(subCmd)) {
 201         if (assign->provide && !assign->sym)
 202           continue;
 203         writeHeader(os, assign->addr,
 204                     osec->getLMA() + assign->addr - osec->getVA(0),
 205                     assign->size, 1);
 206         os << indent8 << assign->commandString << '\n';
 207         continue;
 208       }
 209     }
 210   }
 211 }
 212
 213 // Output a cross reference table to stdout. This is for --cref.
 214 //
 215 // For each global symbol, we print out a file that defines the symbol
 216 // followed by files that uses that symbol. Here is an example.
 217 //
 218 //     strlen     /lib/x86_64-linux-gnu/libc.so.6
 219 //                tools/lld/tools/lld/CMakeFiles/lld.dir/lld.cpp.o
 220 //                lib/libLLVMSupport.a(PrettyStackTrace.cpp.o)
 221 //
 222 // In this case, strlen is defined by libc.so.6 and used by other two
 223 // files.
 224 static void writeCref(raw_fd_ostream &os) {
 225   // Collect symbols and files.
 226   MapVector<Symbol *, SetVector<InputFile *>> map;
 227   for (ELFFileBase *file : ctx.objectFiles) {
 228     for (Symbol *sym : file->getSymbols()) {
 229       if (isa<SharedSymbol>(sym))
 230         map[sym].insert(file);
 231       if (auto *d = dyn_cast<Defined>(sym))
 232         if (!d->isLocal())
 233           map[d].insert(file);
 234     }
 235   }
 236
 237   auto print = [&](StringRef a, StringRef b) {
 238     os << left_justify(a, 49) << ' ' << b << '\n';
 239   };
 240
 241   // Print a blank line and a header. The format matches GNU ld.
 242   os << "\nCross Reference Table\n\n";
 243   print("Symbol", "File");
 244
 245   // Print out a table.
 246   for (auto kv : map) {
 247     Symbol *sym = kv.first;
 248     SetVector<InputFile *> &files = kv.second;
 249
 250     print(toString(*sym), toString(sym->file));
 251     for (InputFile *file : files)
 252       if (file != sym->file)
 253         print("", toString(file));
 254   }
 255 }
 256
 257 void elf::writeMapAndCref() {
 258   if (config->mapFile.empty() && !config->cref)
 259     return;
 260
 261   llvm::TimeTraceScope timeScope("Write map file");
 262
 263   // Open a map file for writing.
 264   std::error_code ec;
 265   StringRef mapFile = config->mapFile.empty() ? "-" : config->mapFile;
 266   raw_fd_ostream os = ctx.openAuxiliaryFile(mapFile, ec);
 267   if (ec) {
 268     error("cannot open " + mapFile + ": " + ec.message());
 269     return;
 270   }
 271
 272   if (!config->mapFile.empty())
 273     writeMapFile(os);
 274   if (config->cref)
 275     writeCref(os);
 276 }