[llvm-dlltool] Implement the --identify option

llvm/lib/ToolDrivers/llvm-dlltool/DlltoolDriver.cpp

@@ -12,6 +12,7 @@
 
 #include "llvm/ToolDrivers/llvm-dlltool/DlltoolDriver.h"
 #include "llvm/ADT/StringSwitch.h"
+#include "llvm/Object/Archive.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/Object/COFFImportFile.h"
 #include "llvm/Object/COFFModuleDefinition.h"
@@ -158,6 +159,143 @@ bool parseModuleDefinition(StringRef DefFileName, MachineTypes Machine,
   return true;
 }
 
+int printError(llvm::Error E, Twine File) {
+  if (!E)
+    return 0;
+  handleAllErrors(std::move(E), [&](const llvm::ErrorInfoBase &EIB) {
+    llvm::errs() << "error opening " << File << ": " << EIB.message() << "\n";
+  });
+  return 1;
+}
+
+template <typename Callable>
+int forEachCoff(object::Archive &Archive, StringRef Name, Callable Callback) {
+  Error Err = Error::success();
+  for (auto &C : Archive.children(Err)) {
+    Expected<StringRef> NameOrErr = C.getName();
+    if (!NameOrErr)
+      return printError(NameOrErr.takeError(), Name);
+    StringRef Name = *NameOrErr;
+
+    Expected<MemoryBufferRef> ChildMB = C.getMemoryBufferRef();
+    if (!ChildMB)
+      return printError(ChildMB.takeError(), Name);
+
+    if (identify_magic(ChildMB->getBuffer()) == file_magic::coff_object) {
+      auto Obj = object::COFFObjectFile::create(*ChildMB);
+      if (!Obj)
+        return printError(Obj.takeError(), Name);
+      if (!Callback(*Obj->get(), Name))
+        return 1;
+    }
+  }
+  if (Err)
+    return printError(std::move(Err), Name);
+  return 0;
+}
+
+// To find the named of the imported DLL from an import library, we can either
+// inspect the object files that form the import table entries, or we could
+// just look at the archive member names, for MSVC style import libraries.
+// Looking at the archive member names doesn't work for GNU style import
+// libraries though, while inspecting the import table entries works for
+// both. (MSVC style import libraries contain a couple regular object files
+// for the header/trailers.)
+//
+// This implementation does the same as GNU dlltool does; look at the
+// content of ".idata$7" sections, or for MSVC style libraries, look
+// at ".idata$6" sections.
+//
+// For GNU style import libraries, there are also other data chunks in sections
+// named ".idata$7" (entries to the IAT or ILT); these are distinguished
+// by seeing that they contain relocations. (They also look like an empty
+// string when looking for null termination.)
+//
+// Alternatively, we could do things differently - look for any .idata$2
+// section; this would be import directory entries. At offset 0xc in them
+// there is the RVA of the import DLL name; look for a relocation at this
+// spot and locate the symbol that it points at. That symbol may either
+// be within the same object file (in the case of MSVC style import libraries)
+// or another object file (in the case of GNU import libraries).
+bool identifyImportName(const COFFObjectFile &Obj, StringRef ObjName,
+                        std::vector<StringRef> &Names, bool IsMsStyleImplib) {
+  StringRef TargetName = IsMsStyleImplib ? ".idata$6" : ".idata$7";
+  for (const auto &S : Obj.sections()) {
+    Expected<StringRef> NameOrErr = S.getName();
+    if (!NameOrErr) {
+      printError(NameOrErr.takeError(), ObjName);
+      return false;
+    }
+    StringRef Name = *NameOrErr;
+    if (Name != TargetName)
+      continue;
+
+    // GNU import libraries contain .idata$7 section in the per function
+    // objects too, but they contain relocations.
+    if (!IsMsStyleImplib && !S.relocations().empty())
+      continue;
+
+    Expected<StringRef> ContentsOrErr = S.getContents();
+    if (!ContentsOrErr) {
+      printError(ContentsOrErr.takeError(), ObjName);
+      return false;
+    }
+    StringRef Contents = *ContentsOrErr;
+    Contents = Contents.substr(0, Contents.find('\0'));
+    if (Contents.empty())
+      continue;
+    Names.push_back(Contents);
+    return true;
+  }
+  return true;
+}
+
+int doIdentify(StringRef File, bool IdentifyStrict) {
+  ErrorOr<std::unique_ptr<MemoryBuffer>> MaybeBuf = MemoryBuffer::getFile(
+      File, /*IsText=*/false, /*RequiredNullTerminator=*/false);
+  if (!MaybeBuf)
+    return printError(errorCodeToError(MaybeBuf.getError()), File);
+  if (identify_magic(MaybeBuf.get()->getBuffer()) != file_magic::archive) {
+    llvm::errs() << File << " is not a library\n";
+    return 1;
+  }
+
+  std::unique_ptr<MemoryBuffer> B = std::move(MaybeBuf.get());
+  Error Err = Error::success();
+  object::Archive Archive(B->getMemBufferRef(), Err);
+  if (Err)
+    return printError(std::move(Err), B->getBufferIdentifier());
+
+  bool IsMsStyleImplib = false;
+  for (const auto &S : Archive.symbols()) {
+    if (S.getName() == "__NULL_IMPORT_DESCRIPTOR") {
+      IsMsStyleImplib = true;
+      break;
+    }
+  }
+  std::vector<StringRef> Names;
+  if (forEachCoff(Archive, B->getBufferIdentifier(),
+                  [&](const COFFObjectFile &Obj, StringRef ObjName) -> bool {
+                    return identifyImportName(Obj, ObjName, Names,
+                                              IsMsStyleImplib);
+                  }))
+    return 1;
+
+  if (Names.empty()) {
+    llvm::errs() << "No DLL import name found in " << File << "\n";
+    return 1;
+  }
+  if (Names.size() > 1 && IdentifyStrict) {
+    llvm::errs() << File << "contains imports for two or more DLLs\n";
+    return 1;
+  }
+
+  for (StringRef S : Names)
+    llvm::outs() << S << "\n";
+
+  return 0;
+}
+
 } // namespace
 
 int llvm::dlltoolDriverMain(llvm::ArrayRef<const char *> ArgsArr) {
@@ -173,7 +311,8 @@ int llvm::dlltoolDriverMain(llvm::ArrayRef<const char *> ArgsArr) {
 
   // Handle when no input or output is specified
   if (Args.hasArgNoClaim(OPT_INPUT) ||
-      (!Args.hasArgNoClaim(OPT_d) && !Args.hasArgNoClaim(OPT_l))) {
+      (!Args.hasArgNoClaim(OPT_d) && !Args.hasArgNoClaim(OPT_l) &&
+       !Args.hasArgNoClaim(OPT_I))) {
     Table.printHelp(outs(), "llvm-dlltool [options] file...", "llvm-dlltool",
                     false);
     llvm::outs()
@@ -185,6 +324,11 @@ int llvm::dlltoolDriverMain(llvm::ArrayRef<const char *> ArgsArr) {
     llvm::errs() << "ignoring unknown argument: " << Arg->getAsString(Args)
                  << "\n";
 
+  if (Args.hasArg(OPT_I)) {
+    return doIdentify(Args.getLastArg(OPT_I)->getValue(),
+                      Args.hasArg(OPT_identify_strict));
+  }
+
   if (!Args.hasArg(OPT_d)) {
     llvm::errs() << "no definition file specified\n";
     return 1;

llvm/lib/ToolDrivers/llvm-dlltool/Options.td

@@ -21,6 +21,11 @@ def k_alias: Flag<["--"], "kill-at">, Alias<k>;
 def no_leading_underscore: Flag<["--"], "no-leading-underscore">,
     HelpText<"Don't add leading underscores on symbols">;
 
+def I: JoinedOrSeparate<["-"], "I">, HelpText<"Identify DLL name from import library">;
+def I_long : JoinedOrSeparate<["--"], "identify">, Alias<I>;
+
+def identify_strict : Flag<["--"], "identify-strict">, HelpText<"Error out if the --identify option detects more than one DLL">;
+
 //==============================================================================
 // The flags below do nothing. They are defined only for dlltool compatibility.
 //==============================================================================

llvm/test/tools/llvm-dlltool/Inputs/gnu_foo_lib_h.yaml

@@ -0,0 +1,133 @@
+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_I386
+  Characteristics: [ IMAGE_FILE_LINE_NUMS_STRIPPED, IMAGE_FILE_32BIT_MACHINE ]
+sections:
+  - Name:            .text
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     ''
+  - Name:            .data
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
+    Alignment:       4
+    SectionData:     ''
+  - Name:            .bss
+    Characteristics: [ IMAGE_SCN_CNT_UNINITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
+    Alignment:       4
+    SectionData:     ''
+  - Name:            '.idata$2'
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
+    Alignment:       4
+    SectionData:     '0000000000000000000000000000000000000000'
+    SizeOfRawData:   20
+    Relocations:
+      - VirtualAddress:  0
+        SymbolName:      '.idata$4'
+        Type:            IMAGE_REL_I386_DIR32NB
+      - VirtualAddress:  12
+        SymbolName:      __foo_lib_iname
+        Type:            IMAGE_REL_I386_DIR32NB
+      - VirtualAddress:  16
+        SymbolName:      '.idata$5'
+        Type:            IMAGE_REL_I386_DIR32NB
+  - Name:            '.idata$5'
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
+    Alignment:       4
+    SectionData:     ''
+  - Name:            '.idata$4'
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
+    Alignment:       4
+    SectionData:     ''
+symbols:
+  - Name:            .file
+    Value:           0
+    SectionNumber:   -2
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_FILE
+    File:            fake
+  - Name:            hname
+    Value:           0
+    SectionNumber:   6
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+  - Name:            fthunk
+    Value:           0
+    SectionNumber:   5
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+  - Name:            .text
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          0
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          0
+  - Name:            .data
+    Value:           0
+    SectionNumber:   2
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          0
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          0
+  - Name:            .bss
+    Value:           0
+    SectionNumber:   3
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          0
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          0
+  - Name:            '.idata$2'
+    Value:           0
+    SectionNumber:   4
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          20
+      NumberOfRelocations: 3
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          0
+  - Name:            '.idata$4'
+    Value:           0
+    SectionNumber:   6
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+  - Name:            '.idata$5'
+    Value:           0
+    SectionNumber:   5
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+  - Name:            __head_foo_lib
+    Value:           0
+    SectionNumber:   4
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            __foo_lib_iname
+    Value:           0
+    SectionNumber:   0
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+...