[lld][MachO] Add debug info support for MachO.

This patch causes LLD to build stabs debugging symbols for files containing
DWARF debug info, and to propagate existing stabs symbols for object files
built using '-r' mode. This enables debugging of binaries generated by LLD
from MachO objects.

llvm-svn: 276921

1 files changed, 321 insertions, 12 deletions

diff --git a/lld/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp b/lld/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp
index fc760a3eddd..9867d92563e 100644
--- a/lld/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp
+++ b/lld/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp
@@ -27,7 +27,11 @@
 #include "MachONormalizedFileBinaryUtils.h"
 #include "lld/Core/Error.h"
 #include "lld/Core/LLVM.h"
+#include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
+#include "llvm/Support/DataExtractor.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/Dwarf.h"
+#include "llvm/Support/Error.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/MachO.h"
 #include "llvm/Support/LEB128.h"
@@ -499,7 +503,7 @@ const Section* findSectionCoveringAddress(const NormalizedFile &normalizedFile,
 
 const MachODefinedAtom *
 findAtomCoveringAddress(const NormalizedFile &normalizedFile, MachOFile &file,
-                        uint64_t addr, Reference::Addend *addend) {
+                        uint64_t addr, Reference::Addend &addend) {
   const Section *sect = nullptr;
   sect = findSectionCoveringAddress(normalizedFile, addr);
   if (!sect)
@@ -509,7 +513,7 @@ findAtomCoveringAddress(const NormalizedFile &normalizedFile, MachOFile &file,
   uint64_t offsetInSect = addr - sect->address;
   auto atom =
       file.findAtomCoveringAddress(*sect, offsetInSect, &offsetInTarget);
-  *addend = offsetInTarget;
+  addend = offsetInTarget;
   return atom;
 }
 
@@ -548,19 +552,23 @@ llvm::Error convertRelocs(const Section &section,
                            -> llvm::Error {
     // Find symbol from index.
     const Symbol *sym = nullptr;
+    uint32_t numStabs  = normalizedFile.stabsSymbols.size();
     uint32_t numLocal  = normalizedFile.localSymbols.size();
     uint32_t numGlobal = normalizedFile.globalSymbols.size();
     uint32_t numUndef  = normalizedFile.undefinedSymbols.size();
-    if (symbolIndex < numLocal) {
-      sym = &normalizedFile.localSymbols[symbolIndex];
-    } else if (symbolIndex < numLocal+numGlobal) {
-      sym = &normalizedFile.globalSymbols[symbolIndex-numLocal];
-    } else if (symbolIndex < numLocal+numGlobal+numUndef) {
-      sym = &normalizedFile.undefinedSymbols[symbolIndex-numLocal-numGlobal];
+    assert(symbolIndex >= numStabs && "Searched for stab via atomBySymbol?");
+    if (symbolIndex < numStabs+numLocal) {
+      sym = &normalizedFile.localSymbols[symbolIndex-numStabs];
+    } else if (symbolIndex < numStabs+numLocal+numGlobal) {
+      sym = &normalizedFile.globalSymbols[symbolIndex-numStabs-numLocal];
+    } else if (symbolIndex < numStabs+numLocal+numGlobal+numUndef) {
+      sym = &normalizedFile.undefinedSymbols[symbolIndex-numStabs-numLocal-
+                                             numGlobal];
     } else {
       return llvm::make_error<GenericError>(Twine("symbol index (")
                                      + Twine(symbolIndex) + ") out of range");
     }
+
     // Find atom from symbol.
     if ((sym->type & N_TYPE) == N_SECT) {
       if (sym->sect > normalizedFile.sections.size())
@@ -685,6 +693,296 @@ bool isDebugInfoSection(const Section &section) {
   return section.segmentName.equals("__DWARF");
 }
 
+static const Atom* findDefinedAtomByName(MachOFile &file, Twine name) {
+  std::string strName = name.str();
+  for (auto *atom : file.defined())
+    if (atom->name() == strName)
+      return atom;
+  return nullptr;
+}
+
+static StringRef copyDebugString(StringRef str, BumpPtrAllocator &alloc) {
+  std::string *strCopy = alloc.Allocate<std::string>();
+  *strCopy = str;
+  return *strCopy;
+}
+
+llvm::Error parseStabs(MachOFile &file,
+                       const NormalizedFile &normalizedFile,
+                       bool copyRefs) {
+
+  if (normalizedFile.stabsSymbols.empty())
+    return llvm::Error::success();
+
+  // FIXME: Kill this off when we can move to sane yaml parsing.
+  std::unique_ptr<BumpPtrAllocator> allocator;
+  if (copyRefs)
+    allocator = llvm::make_unique<BumpPtrAllocator>();
+
+  enum { start, inBeginEnd } state = start;
+
+  const Atom *currentAtom = nullptr;
+  uint64_t currentAtomAddress = 0;
+  StabsDebugInfo::StabsList stabsList;
+  for (const auto &stabSym : normalizedFile.stabsSymbols) {
+    Stab stab(nullptr, stabSym.type, stabSym.sect, stabSym.desc,
+              stabSym.value, stabSym.name);
+    switch (state) {
+    case start:
+      switch (static_cast<StabType>(stabSym.type)) {
+      case N_BNSYM:
+        state = inBeginEnd;
+        currentAtomAddress = stabSym.value;
+        Reference::Addend addend;
+        currentAtom = findAtomCoveringAddress(normalizedFile, file,
+                                              currentAtomAddress, addend);
+        if (addend != 0)
+          return llvm::make_error<GenericError>(
+                   "Non-zero addend for BNSYM '" + stabSym.name + "' in " +
+                   file.path());
+        if (currentAtom)
+          stab.atom = currentAtom;
+        else {
+          // FIXME: ld64 just issues a warning here - should we match that?
+          return llvm::make_error<GenericError>(
+                   "can't find atom for stabs BNSYM at " +
+                   Twine::utohexstr(stabSym.value) + " in " + file.path());
+        }
+        break;
+      case N_SO:
+      case N_OSO:
+        // Not associated with an atom, just copy.
+        if (copyRefs)
+          stab.str = copyDebugString(stabSym.name, *allocator);
+        else
+          stab.str = stabSym.name;
+        break;
+      case N_GSYM: {
+        auto colonIdx = stabSym.name.find(':');
+        if (colonIdx != StringRef::npos) {
+          StringRef name = stabSym.name.substr(0, colonIdx);
+          currentAtom = findDefinedAtomByName(file, "_" + name);
+          stab.atom = currentAtom;
+          if (copyRefs)
+            stab.str = copyDebugString(stabSym.name, *allocator);
+          else
+            stab.str = stabSym.name;
+        } else {
+          currentAtom = findDefinedAtomByName(file, stabSym.name);
+          stab.atom = currentAtom;
+          if (copyRefs)
+            stab.str = copyDebugString(stabSym.name, *allocator);
+          else
+            stab.str = stabSym.name;
+        }
+        if (stab.atom == nullptr)
+          return llvm::make_error<GenericError>(
+                   "can't find atom for N_GSYM stabs" + stabSym.name +
+                   " in " + file.path());
+        break;
+      }
+      case N_FUN:
+        return llvm::make_error<GenericError>(
+                 "old-style N_FUN stab '" + stabSym.name + "' unsupported");
+      default:
+        return llvm::make_error<GenericError>(
+                 "unrecognized stab symbol '" + stabSym.name + "'");
+      }
+      break;
+    case inBeginEnd:
+      stab.atom = currentAtom;
+      switch (static_cast<StabType>(stabSym.type)) {
+      case N_ENSYM:
+        state = start;
+        currentAtom = nullptr;
+        break;
+      case N_FUN:
+        // Just copy the string.
+        if (copyRefs)
+          stab.str = copyDebugString(stabSym.name, *allocator);
+        else
+          stab.str = stabSym.name;
+        break;
+      default:
+        return llvm::make_error<GenericError>(
+                 "unrecognized stab symbol '" + stabSym.name + "'");
+      }
+    }
+    llvm::dbgs() << "Adding to stabsList: " << stab << "\n";
+    stabsList.push_back(stab);
+  }
+
+  file.setDebugInfo(llvm::make_unique<StabsDebugInfo>(std::move(stabsList)));
+
+  // FIXME: Kill this off when we fix YAML memory ownership.
+  file.debugInfo()->setAllocator(std::move(allocator));
+
+  return llvm::Error::success();
+}
+
+static llvm::DataExtractor
+dataExtractorFromSection(const NormalizedFile &normalizedFile,
+                         const Section &S) {
+  const bool is64 = MachOLinkingContext::is64Bit(normalizedFile.arch);
+  const bool isBig = MachOLinkingContext::isBigEndian(normalizedFile.arch);
+  StringRef SecData(reinterpret_cast<const char*>(S.content.data()),
+                    S.content.size());
+  return llvm::DataExtractor(SecData, !isBig, is64 ? 8 : 4);
+}
+
+// FIXME: Cribbed from llvm-dwp -- should share "lightweight CU DIE
+//        inspection" code if possible.
+static uint32_t getCUAbbrevOffset(llvm::DataExtractor abbrevData,
+                                  uint64_t abbrCode) {
+  uint64_t curCode;
+  uint32_t offset = 0;
+  while ((curCode = abbrevData.getULEB128(&offset)) != abbrCode) {
+    // Tag
+    abbrevData.getULEB128(&offset);
+    // DW_CHILDREN
+    abbrevData.getU8(&offset);
+    // Attributes
+    while (abbrevData.getULEB128(&offset) | abbrevData.getULEB128(&offset))
+      ;
+  }
+  return offset;
+}
+
+// FIXME: Cribbed from llvm-dwp -- should share "lightweight CU DIE
+//        inspection" code if possible.
+static Expected<const char *>
+getIndexedString(const NormalizedFile &normalizedFile,
+                 uint32_t form, llvm::DataExtractor infoData,
+                 uint32_t &infoOffset, const Section &stringsSection) {
+  if (form == llvm::dwarf::DW_FORM_string)
+   return infoData.getCStr(&infoOffset);
+  if (form != llvm::dwarf::DW_FORM_strp)
+    return llvm::make_error<GenericError>(
+        "string field encoded without DW_FORM_strp");
+  uint32_t stringOffset = infoData.getU32(&infoOffset);
+  llvm::DataExtractor stringsData =
+    dataExtractorFromSection(normalizedFile, stringsSection);
+  return stringsData.getCStr(&stringOffset);
+}
+
+// FIXME: Cribbed from llvm-dwp -- should share "lightweight CU DIE
+//        inspection" code if possible.
+static llvm::Expected<TranslationUnitSource>
+readCompUnit(const NormalizedFile &normalizedFile,
+             const Section &info,
+             const Section &abbrev,
+             const Section &strings,
+             StringRef path) {
+  // FIXME: Cribbed from llvm-dwp -- should share "lightweight CU DIE
+  //        inspection" code if possible.
+  uint32_t offset = 0;
+  auto infoData = dataExtractorFromSection(normalizedFile, info);
+  uint32_t length = infoData.getU32(&offset);
+  if (length == 0xffffffff)
+    infoData.getU64(&offset);
+  else if (length > 0xffffff00)
+    return llvm::make_error<GenericError>("Malformed DWARF in " + path);
+
+  uint16_t version = infoData.getU16(&offset);
+
+  if (version < 2 || version > 4)
+    return llvm::make_error<GenericError>("Unsupported DWARF version in " +
+                                          path);
+
+  infoData.getU32(&offset); // Abbrev offset (should be zero)
+  uint8_t addrSize = infoData.getU8(&offset);
+
+  uint32_t abbrCode = infoData.getULEB128(&offset);
+  auto abbrevData = dataExtractorFromSection(normalizedFile, abbrev);
+  uint32_t abbrevOffset = getCUAbbrevOffset(abbrevData, abbrCode);
+  uint64_t tag = abbrevData.getULEB128(&abbrevOffset);
+  if (tag != llvm::dwarf::DW_TAG_compile_unit)
+    return llvm::make_error<GenericError>("top level DIE is not a compile unit");
+  // DW_CHILDREN
+  abbrevData.getU8(&abbrevOffset);
+  uint32_t name;
+  uint32_t form;
+  TranslationUnitSource tu;
+  while ((name = abbrevData.getULEB128(&abbrevOffset)) |
+             (form = abbrevData.getULEB128(&abbrevOffset)) &&
+         (name != 0 || form != 0)) {
+    switch (name) {
+    case llvm::dwarf::DW_AT_name: {
+      if (auto eName = getIndexedString(normalizedFile, form, infoData, offset,
+                                        strings))
+          tu.name = *eName;
+      else
+        return eName.takeError();
+      break;
+    }
+    case llvm::dwarf::DW_AT_comp_dir: {
+      if (auto eName = getIndexedString(normalizedFile, form, infoData, offset,
+                                        strings))
+        tu.path = *eName;
+      else
+        return eName.takeError();
+      break;
+    }
+    default:
+      llvm::DWARFFormValue::skipValue(form, infoData, &offset, version,
+                                      addrSize);
+    }
+  }
+  return tu;
+}
+
+llvm::Error parseDebugInfo(MachOFile &file,
+                           const NormalizedFile &normalizedFile, bool copyRefs) {
+
+  // Find the interesting debug info sections.
+  const Section *debugInfo = nullptr;
+  const Section *debugAbbrev = nullptr;
+  const Section *debugStrings = nullptr;
+
+  for (auto &s : normalizedFile.sections) {
+    if (s.segmentName == "__DWARF") {
+      if (s.sectionName == "__debug_info")
+        debugInfo = &s;
+      else if (s.sectionName == "__debug_abbrev")
+        debugAbbrev = &s;
+      else if (s.sectionName == "__debug_str")
+        debugStrings = &s;
+    }
+  }
+
+  if (!debugInfo)
+    return parseStabs(file, normalizedFile, copyRefs);
+
+  if (debugInfo->content.size() == 0)
+    return llvm::Error::success();
+
+  if (debugInfo->content.size() < 12)
+    return llvm::make_error<GenericError>("Malformed __debug_info section in " +
+                                          file.path() + ": too small");
+
+  if (!debugAbbrev)
+    return llvm::make_error<GenericError>("Missing __dwarf_abbrev section in " +
+                                          file.path());
+
+  if (auto tuOrErr = readCompUnit(normalizedFile, *debugInfo, *debugAbbrev,
+                                  *debugStrings, file.path())) {
+    // FIXME: Kill of allocator and code under 'copyRefs' when we fix YAML
+    //        memory ownership.
+    std::unique_ptr<BumpPtrAllocator> allocator;
+    if (copyRefs) {
+      allocator = llvm::make_unique<BumpPtrAllocator>();
+      tuOrErr->name = copyDebugString(tuOrErr->name, *allocator);
+      tuOrErr->path = copyDebugString(tuOrErr->path, *allocator);
+    }
+    file.setDebugInfo(llvm::make_unique<DwarfDebugInfo>(std::move(*tuOrErr)));
+    if (copyRefs)
+      file.debugInfo()->setAllocator(std::move(allocator));
+  } else
+    return tuOrErr.takeError();
+
+  return llvm::Error::success();
+}
+
 static int64_t readSPtr(bool is64, bool isBig, const uint8_t *addr) {
   if (is64)
     return read64(addr, isBig);
@@ -853,7 +1151,7 @@ static llvm::Error processCIE(const NormalizedFile &normalizedFile,
       const MachODefinedAtom *func = nullptr;
       Reference::Addend addend;
       func = findAtomCoveringAddress(normalizedFile, file, funcAddress,
-                                     &addend);
+                                     addend);
       atom->addReference(Reference::KindNamespace::mach_o, handler.kindArch(),
                          handler.unwindRefToPersonalityFunctionKind(),
                          PersonalityFunctionField, func, addend);
@@ -936,7 +1234,7 @@ static llvm::Error processFDE(const NormalizedFile &normalizedFile,
     }
     Reference::Addend addend;
     auto *target = findAtomCoveringAddress(normalizedFile, file,
-                                           targetAddress, &addend);
+                                           targetAddress, addend);
     atom->addReference(Reference::KindNamespace::mach_o, handler.kindArch(),
                        refKind, refAddress, target, addend);
 
@@ -1095,7 +1393,6 @@ llvm::Error parseObjCImageInfo(const Section &sect,
   return llvm::Error();
 }
 
-
 /// Converts normalized mach-o file into an lld::File and lld::Atoms.
 llvm::Expected<std::unique_ptr<lld::File>>
 objectToAtoms(const NormalizedFile &normalizedFile, StringRef path,
@@ -1136,10 +1433,11 @@ normalizedObjectToAtoms(MachOFile *file,
   // Create atoms from each section.
   for (auto &sect : normalizedFile.sections) {
     DEBUG(llvm::dbgs() << "Creating atoms: "; sect.dump());
+
+    // If this is a debug-info section parse it specially.
     if (isDebugInfoSection(sect))
       continue;
 
-
     // If the file contains an objc_image_info struct, then we should parse the
     // ObjC flags and Swift version.
     if (isObjCImageInfo(sect)) {
@@ -1248,6 +1546,10 @@ normalizedObjectToAtoms(MachOFile *file,
   for (const DefinedAtom* defAtom : file->defined()) {
     reinterpret_cast<const SimpleDefinedAtom*>(defAtom)->sortReferences();
   }
+
+  if (auto err = parseDebugInfo(*file, normalizedFile, copyRefs))
+    return err;
+
   return llvm::Error();
 }
 
@@ -1325,6 +1627,13 @@ normalizedToAtoms(const NormalizedFile &normalizedFile, StringRef path,
 }
 
 #ifndef NDEBUG
+void Relocation::dump(llvm::raw_ostream &OS) const {
+  OS << "Relocation (offset=" << llvm::format_hex(offset, 8, true)
+     << ", scatered=" << scattered << ", type=" << type << ", length=" << length
+     << ", pcrel=" << pcRel << ", isExtern=" << isExtern << ", value="
+     << llvm::format_hex(value, 8, true) << ", symbol=" << symbol << ")\n";
+}
+
 void Section::dump(llvm::raw_ostream &OS) const {
   OS << "Section (\"" << segmentName << ", " << sectionName << "\"";
   OS << ", addr: " << llvm::format_hex(address, 16, true);