lld/COFF/MinGW.cpp

   1 //===- MinGW.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 "MinGW.h"
  10 #include "COFFLinkerContext.h"
  11 #include "Driver.h"
  12 #include "InputFiles.h"
  13 #include "SymbolTable.h"
  14 #include "llvm/ADT/DenseMap.h"
  15 #include "llvm/ADT/DenseSet.h"
  16 #include "llvm/Object/COFF.h"
  17 #include "llvm/Support/Parallel.h"
  18 #include "llvm/Support/Path.h"
  19 #include "llvm/Support/raw_ostream.h"
  20
  21 using namespace llvm;
  22 using namespace llvm::COFF;
  23 using namespace lld;
  24 using namespace lld::coff;
  25
  26 AutoExporter::AutoExporter(
  27     COFFLinkerContext &ctx,
  28     const llvm::DenseSet<StringRef> &manualExcludeSymbols)
  29     : manualExcludeSymbols(manualExcludeSymbols), ctx(ctx) {
  30   excludeLibs = {
  31       "libgcc",
  32       "libgcc_s",
  33       "libstdc++",
  34       "libmingw32",
  35       "libmingwex",
  36       "libg2c",
  37       "libsupc++",
  38       "libobjc",
  39       "libgcj",
  40       "libclang_rt.builtins",
  41       "libclang_rt.builtins-aarch64",
  42       "libclang_rt.builtins-arm",
  43       "libclang_rt.builtins-i386",
  44       "libclang_rt.builtins-x86_64",
  45       "libclang_rt.profile",
  46       "libclang_rt.profile-aarch64",
  47       "libclang_rt.profile-arm",
  48       "libclang_rt.profile-i386",
  49       "libclang_rt.profile-x86_64",
  50       "libc++",
  51       "libc++abi",
  52       "libFortran_main",
  53       "libFortranRuntime",
  54       "libFortranDecimal",
  55       "libunwind",
  56       "libmsvcrt",
  57       "libucrtbase",
  58   };
  59
  60   excludeObjects = {
  61       "crt0.o",    "crt1.o",  "crt1u.o", "crt2.o",  "crt2u.o",    "dllcrt1.o",
  62       "dllcrt2.o", "gcrt0.o", "gcrt1.o", "gcrt2.o", "crtbegin.o", "crtend.o",
  63   };
  64
  65   excludeSymbolPrefixes = {
  66       // Import symbols
  67       "__imp_",
  68       "__IMPORT_DESCRIPTOR_",
  69       // Extra import symbols from GNU import libraries
  70       "__nm_",
  71       // C++ symbols
  72       "__rtti_",
  73       "__builtin_",
  74       // Artificial symbols such as .refptr
  75       ".",
  76       // profile generate symbols
  77       "__profc_",
  78       "__profd_",
  79       "__profvp_",
  80   };
  81
  82   excludeSymbolSuffixes = {
  83       "_iname",
  84       "_NULL_THUNK_DATA",
  85   };
  86
  87   if (ctx.config.machine == I386) {
  88     excludeSymbols = {
  89         "__NULL_IMPORT_DESCRIPTOR",
  90         "__pei386_runtime_relocator",
  91         "_do_pseudo_reloc",
  92         "_impure_ptr",
  93         "__impure_ptr",
  94         "__fmode",
  95         "_environ",
  96         "___dso_handle",
  97         // These are the MinGW names that differ from the standard
  98         // ones (lacking an extra underscore).
  99         "_DllMain@12",
 100         "_DllEntryPoint@12",
 101         "_DllMainCRTStartup@12",
 102     };
 103     excludeSymbolPrefixes.insert("__head_");
 104   } else {
 105     excludeSymbols = {
 106         "__NULL_IMPORT_DESCRIPTOR",
 107         "_pei386_runtime_relocator",
 108         "do_pseudo_reloc",
 109         "impure_ptr",
 110         "_impure_ptr",
 111         "_fmode",
 112         "environ",
 113         "__dso_handle",
 114         // These are the MinGW names that differ from the standard
 115         // ones (lacking an extra underscore).
 116         "DllMain",
 117         "DllEntryPoint",
 118         "DllMainCRTStartup",
 119     };
 120     excludeSymbolPrefixes.insert("_head_");
 121   }
 122 }
 123
 124 void AutoExporter::addWholeArchive(StringRef path) {
 125   StringRef libName = sys::path::filename(path);
 126   // Drop the file extension, to match the processing below.
 127   libName = libName.substr(0, libName.rfind('.'));
 128   excludeLibs.erase(libName);
 129 }
 130
 131 void AutoExporter::addExcludedSymbol(StringRef symbol) {
 132   excludeSymbols.insert(symbol);
 133 }
 134
 135 bool AutoExporter::shouldExport(Defined *sym) const {
 136   if (!sym || !sym->getChunk())
 137     return false;
 138
 139   // Only allow the symbol kinds that make sense to export; in particular,
 140   // disallow import symbols.
 141   if (!isa<DefinedRegular>(sym) && !isa<DefinedCommon>(sym))
 142     return false;
 143   if (excludeSymbols.count(sym->getName()) || manualExcludeSymbols.count(sym->getName()))
 144     return false;
 145
 146   for (StringRef prefix : excludeSymbolPrefixes.keys())
 147     if (sym->getName().starts_with(prefix))
 148       return false;
 149   for (StringRef suffix : excludeSymbolSuffixes.keys())
 150     if (sym->getName().ends_with(suffix))
 151       return false;
 152
 153   // If a corresponding __imp_ symbol exists and is defined, don't export it.
 154   if (ctx.symtab.find(("__imp_" + sym->getName()).str()))
 155     return false;
 156
 157   // Check that file is non-null before dereferencing it, symbols not
 158   // originating in regular object files probably shouldn't be exported.
 159   if (!sym->getFile())
 160     return false;
 161
 162   StringRef libName = sys::path::filename(sym->getFile()->parentName);
 163
 164   // Drop the file extension.
 165   libName = libName.substr(0, libName.rfind('.'));
 166   if (!libName.empty())
 167     return !excludeLibs.count(libName);
 168
 169   StringRef fileName = sys::path::filename(sym->getFile()->getName());
 170   return !excludeObjects.count(fileName);
 171 }
 172
 173 void lld::coff::writeDefFile(StringRef name,
 174                              const std::vector<Export> &exports) {
 175   std::error_code ec;
 176   raw_fd_ostream os(name, ec, sys::fs::OF_None);
 177   if (ec)
 178     fatal("cannot open " + name + ": " + ec.message());
 179
 180   os << "EXPORTS\n";
 181   for (const Export &e : exports) {
 182     os << "    " << e.exportName << " "
 183        << "@" << e.ordinal;
 184     if (auto *def = dyn_cast_or_null<Defined>(e.sym)) {
 185       if (def && def->getChunk() &&
 186           !(def->getChunk()->getOutputCharacteristics() & IMAGE_SCN_MEM_EXECUTE))
 187         os << " DATA";
 188     }
 189     os << "\n";
 190   }
 191 }
 192
 193 static StringRef mangle(Twine sym, MachineTypes machine) {
 194   assert(machine != IMAGE_FILE_MACHINE_UNKNOWN);
 195   if (machine == I386)
 196     return saver().save("_" + sym);
 197   return saver().save(sym);
 198 }
 199
 200 // Handles -wrap option.
 201 //
 202 // This function instantiates wrapper symbols. At this point, they seem
 203 // like they are not being used at all, so we explicitly set some flags so
 204 // that LTO won't eliminate them.
 205 std::vector<WrappedSymbol>
 206 lld::coff::addWrappedSymbols(COFFLinkerContext &ctx, opt::InputArgList &args) {
 207   std::vector<WrappedSymbol> v;
 208   DenseSet<StringRef> seen;
 209
 210   for (auto *arg : args.filtered(OPT_wrap)) {
 211     StringRef name = arg->getValue();
 212     if (!seen.insert(name).second)
 213       continue;
 214
 215     Symbol *sym = ctx.symtab.findUnderscore(name);
 216     if (!sym)
 217       continue;
 218
 219     Symbol *real =
 220         ctx.symtab.addUndefined(mangle("__real_" + name, ctx.config.machine));
 221     Symbol *wrap =
 222         ctx.symtab.addUndefined(mangle("__wrap_" + name, ctx.config.machine));
 223     v.push_back({sym, real, wrap});
 224
 225     // These symbols may seem undefined initially, but don't bail out
 226     // at symtab.reportUnresolvable() due to them, but let wrapSymbols
 227     // below sort things out before checking finally with
 228     // symtab.resolveRemainingUndefines().
 229     sym->deferUndefined = true;
 230     real->deferUndefined = true;
 231     // We want to tell LTO not to inline symbols to be overwritten
 232     // because LTO doesn't know the final symbol contents after renaming.
 233     real->canInline = false;
 234     sym->canInline = false;
 235
 236     // Tell LTO not to eliminate these symbols.
 237     sym->isUsedInRegularObj = true;
 238     if (!isa<Undefined>(wrap))
 239       wrap->isUsedInRegularObj = true;
 240   }
 241   return v;
 242 }
 243
 244 // Do renaming for -wrap by updating pointers to symbols.
 245 //
 246 // When this function is executed, only InputFiles and symbol table
 247 // contain pointers to symbol objects. We visit them to replace pointers,
 248 // so that wrapped symbols are swapped as instructed by the command line.
 249 void lld::coff::wrapSymbols(COFFLinkerContext &ctx,
 250                             ArrayRef<WrappedSymbol> wrapped) {
 251   DenseMap<Symbol *, Symbol *> map;
 252   for (const WrappedSymbol &w : wrapped) {
 253     map[w.sym] = w.wrap;
 254     map[w.real] = w.sym;
 255     if (Defined *d = dyn_cast<Defined>(w.wrap)) {
 256       Symbol *imp = ctx.symtab.find(("__imp_" + w.sym->getName()).str());
 257       // Create a new defined local import for the wrap symbol. If
 258       // no imp prefixed symbol existed, there's no need for it.
 259       // (We can't easily distinguish whether any object file actually
 260       // referenced it or not, though.)
 261       if (imp) {
 262         DefinedLocalImport *wrapimp = make<DefinedLocalImport>(
 263             ctx, saver().save("__imp_" + w.wrap->getName()), d);
 264         ctx.symtab.localImportChunks.push_back(wrapimp->getChunk());
 265         map[imp] = wrapimp;
 266       }
 267     }
 268   }
 269
 270   // Update pointers in input files.
 271   parallelForEach(ctx.objFileInstances, [&](ObjFile *file) {
 272     MutableArrayRef<Symbol *> syms = file->getMutableSymbols();
 273     for (auto &sym : syms)
 274       if (Symbol *s = map.lookup(sym))
 275         sym = s;
 276   });
 277 }